JP2005283657A - Inverter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter device of a discharge tube for image display that can improve display quality by reducing a flicker and luminance deviation of a screen. <P>SOLUTION: A lamp drive circuit 51 generates voltages VL applied to corresponding lamps L while shifting their phases by a phase difference corresponding to a period obtained by dividing one cycle T of the applied voltages VL by the number N of the lamps L. Consequently, noise due to a leak current can be prevented. Further, a ground potential can be stabilized to prevent malfunction of other control systems. Further, the turn-on frequency of all the lamps can be set to N time as high as turn-on frequencies by the lamps. Consequently, a luminance ripple is reduced to suppress interference fringes and a flicker of the liquid crystal display screen and the turn-on frequencies by the lamps are made low to reduce a leak current, thereby reducing luminance deviation of the liquid crystal display screen. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inverter device for driving and driving a discharge tube for liquid crystal display.

  An inverter device used in a liquid crystal display device applies high-voltage and high-frequency applied voltages to discharge tubes, so-called lamps. When the lamp is driven, a leakage current flows to a nearby conductor such as a metal chassis due to the distributed capacitance parasitic on the lamp. The leakage current increases in proportion to the drive frequency at the applied voltage, the voltage, and the distributed capacitance parasitic on the lamp.

  When there are a plurality of lamps, the conventional inverter device performs any one of an asynchronous driving operation, an in-phase driving operation, and an anti-phase driving operation. For example, Patent Document 1 (see FIG. 3) discloses an inverter device that performs an anti-phase synchronization operation.

  FIG. 19 is a block diagram for explaining the inverter device 1 that performs the asynchronous driving operation. A conventional inverter device 1 that performs an asynchronous driving operation applies an applied voltage VL having a different phase to each of the lamps L1 to L6. That is, a phase difference occurs between the applied voltages VL1 to VL6 applied to the lamps L1 to L6. In this case, the leakage current leaking from the lamps L1 to L6 to the adjacent conductor 2 also causes a phase difference. Therefore, the combined leakage current on which the individual leakage currents are superimposed repeatedly increases and decreases non-sinusoidally with time.

  The combined leakage current flows through the circuit while increasing or decreasing. As a result, in a closed circuit in which the proximity conductor 2 and the ground potential are electrically connected, a potential difference ΔV is generated due to an impedance component included in the closed circuit. The generation of this potential difference ΔV becomes a cause of noise and causes a malfunction of other control systems by making the ground potential unstable.

  FIG. 20 is a block diagram for explaining the potential difference between the lamps. FIG. 21 is a graph showing temporal changes in the potential difference between the applied voltages VL1 and VL2 when there is a phase difference between the applied voltages VL1 and VL2 applied to the two adjacent lamps L1 and L2, respectively. FIG. 21 (1) shows the time change of the phase of the applied voltages VL1 and VL2 applied to the two adjacent lamps L1 and L2, respectively. FIG. 21 (2) shows the time change of the potential difference between the applied voltages VL1 and VL2. Indicates. FIG. 21 shows a case where the phase difference between the two applied voltages VL1 and VL2 is 45 degrees, 90 degrees, and 180 degrees, respectively.

  Since the applied voltages are asynchronous, a phase difference of 0 ° or more and 360 ° or less occurs between the two applied voltages VL1 and VL2. As shown in FIG. 21, when the phase difference between the applied voltages VL1 and VL2 is 180 degrees, the potential difference between the two lamps is maximized, and the potential difference is twice the effective value of the applied voltages VL1 and VL2. . Therefore, in order to achieve the electrical insulation of the liquid crystal display device, it is necessary to sufficiently ensure the creepage distance and the spatial distance in the circuit pattern. Further, the connector CN that connects the inverter device 1 and the plurality of lamps L1 to L6 needs to have a high terminal voltage guarantee value.

  FIG. 22 is a block diagram for explaining a case where the proximity conductor 2 has a floating structure in the asynchronous driving state. When the proximity conductor 2 has a floating structure, that is, an insulating structure, the proximity conductor 2 has a high capacitance due to the parasitic capacitance between the closed circuit constituted by the lamps L1 to L6 and the inverter device 1 and the proximity conductor 2. The voltage is induced and dangerous. In addition, contact discharge noise for other adjacent conductors may occur. Furthermore, when the phases of the lighting frequencies of the lamps L1 to L6 are randomly superimposed, interference occurs between the driving timing of the liquid crystal display substrate and the driving timing of the entire lamp, causing the display image to flicker.

  FIG. 23 is a block diagram for explaining the inverter device 3 that performs the in-phase driving operation. The prior art inverter device 3 that performs the same phase driving operation applies the applied voltages VL1 to VL6 having the same phase to the lamps L1 to L6, respectively. In this case, the leakage current leaking from the lamps L1 to L6 to the adjacent conductor 2 also has the same phase. By causing each leakage current to flow in the same phase, the combined leakage current is superimposed without canceling each other, and repeatedly increases and decreases sinusoidally with a large amplitude.

  The combined leakage current flows through the closed circuit while increasing or decreasing. As a result, in a closed circuit in which the proximity conductor 2 and the ground potential are electrically connected, a potential difference ΔV is generated due to an impedance component included in the closed circuit. The generation of this potential difference ΔV becomes a cause of noise and causes a malfunction of other control systems by making the ground potential unstable.

  FIG. 24 is a block diagram for explaining a case where the proximity conductor 2 has a floating structure in the in-phase driving state. When the proximity conductor 2 has a floating structure, that is, an insulating structure, the proximity conductor 2 has a high capacitance due to the parasitic capacitance between the closed circuit constituted by the lamps L1 to L6 and the inverter device 3 and the proximity conductor 2. The voltage is induced and dangerous. In addition, contact discharge noise for other adjacent conductors may occur. Furthermore, when the phases of the lighting frequencies of the lamps L1 to L6 are synchronized, interference occurs between the driving timing of the liquid crystal display substrate and the driving timing of the entire lamp, causing the display image to flicker. In the same phase driving operation, the phase difference between the applied voltages VL1 to VL6 is zero. Therefore, the potential difference between the lamps L1 to L6 can theoretically be zero.

  FIG. 25 is a block diagram for explaining the inverter device 4 that performs the anti-phase synchronization operation. The prior art inverter device 4 that performs the anti-phase synchronization operation applies the applied voltage VL that is 180 degrees out of phase to the two adjacent lamps L. In this case, the leakage current leaking from the lamps L1 to L6 to the adjacent conductor 2 flows in the opposite direction and cancels out, so that the combined leakage current is theoretically zero.

  Since the applied voltages VL applied to the two adjacent lamps L are in opposite phases, a phase difference of 180 degrees is generated between the lamps as shown in FIG. In this case, the maximum potential difference between the lamps is twice the applied voltage VL. Therefore, in order to achieve the electrical insulation of the liquid crystal display device, it is necessary to sufficiently ensure the creepage distance and the spatial distance. The connector CN that connects the inverter device 4 and each of the lamps L1 to L6 needs to have a high inter-terminal voltage guarantee value.

  The liquid crystal display device needs to realize high brightness of the display image and prevent flickering of the display image. In any of the asynchronous drive operation, the in-phase drive operation, and the anti-phase drive operation described above, the frequencies of the applied voltages VL1 to VL6 are set high in order to prevent interference fringes and flickering on the display screen. As a result, leakage current leaking from the lamps VL1 to VL6 increases. When the leakage current increases, a luminance deviation occurs between the high-voltage electrode side and the low-voltage electrode side of the lamps L1 to L6. This becomes more prominent by increasing the applied voltages VL1 to VL6 as the lamps L1 to L6 become longer.

  FIG. 26 is a diagram for explaining the distribution of leakage current with respect to the lamp L. FIG. The lamp L has parasitic capacitance evenly with respect to the adjacent conductor 2. From this distributed capacity, leakage currents I11 to Iln corresponding to the potential gradient of the lamp L leak to the adjacent conductor 2. The current IL passing through the lamp L gradually leaks to the adjacent conductor 2 as it proceeds from the high voltage electrode 5 side to the low voltage electrode 6 side. Therefore, the lamp current IL flowing on the low voltage electrode 6 side is smaller than the current Ih flowing on the high voltage electrode 5 side.

  In the vicinity of the high-voltage electrode 5, since the total current of the lamp current IL and the leakage currents IL1 to ILn leaking to the adjacent conductor 2 contributes to lighting, it lights brightly. On the other hand, the currents Il1 to Iln leak from the lamp L to the adjacent conductor 2 as the voltage goes to the low voltage electrode 6, and the total current contributing to lighting is reduced, so that the brightness is lowered as compared with the high voltage electrode 5 side. Therefore, the lamp L has a luminance deviation between the high voltage electrode 5 side and the low voltage electrode 6 side.

  Further, as an inverter device for driving other than the discharge tube for liquid crystal display, a discharge tube lighting inverter for a fishing light for a fishing boat is disclosed in Patent Document 2, and an inverter for outputting AC power from a solar cell is disclosed in Patent Document 3. Has been.

JP 2000-352718 A Japanese Patent Laid-Open No. 10-290574 JP 2001-268922 A

  In the conventional inverter devices 1, 3, and 4 that perform any one of the asynchronous driving operation, the in-phase driving operation, and the anti-phase driving operation, the display screen flickers or the luminance deviation of the lamp occurs. This becomes more noticeable as the lamp L becomes longer. The techniques disclosed in Patent Document 2 and Patent Document 3 do not disclose driving a lamp for liquid crystal display using an inverter. Therefore, even if the techniques disclosed in Patent Document 2 and Patent Document 3 are taken into consideration, the object of improving the display quality of the liquid crystal display device cannot be achieved.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a discharge tube inverter device for image display which improves display quality by reducing screen flicker and luminance deviation.

The present invention is an inverter device for driving and lighting each of a plurality of liquid crystal display discharge tubes arranged in a predetermined parallel direction,
Driving means for applying an applied voltage to the discharge tube for driving the discharge tube;
The phase of each applied voltage applied to each discharge tube arranged in the parallel direction is sequentially shifted by a phase difference corresponding to a period T / N divided by the number N of discharge tubes with respect to one period T of the applied voltage. The inverter device includes drive signal generating means for supplying a drive signal to the drive means.

  According to the present invention, the drive means is supplied with the drive signal from the drive signal generating means, so that the phase of each applied voltage applied to the discharge tubes arranged in the parallel direction is set to one cycle T of the applied voltage. Each phase difference corresponding to the period T / N divided by the number N is sequentially shifted and given to each discharge tube. As a result, the sum of the leakage currents leaking from the respective discharge tubes to the adjacent conductors can theoretically be zero, and the generation of noise due to the leakage current can be prevented. In addition, the ground potential can be stabilized, and malfunctions in other control systems can be prevented.

  In the present invention, as the number of discharge tubes increases, the potential difference between adjacent discharge tubes can be reduced. Thereby, even if the creeping distance and the spatial distance are small in the discharge tube arrangement pattern, electrical insulation between the discharge tubes can be achieved. In addition, a high guaranteed voltage between terminals is not required for each electrical component constituting the display device. Furthermore, by applying the applied voltages with different phases to the corresponding discharge tubes, the lighting frequency of the entire discharge tube can be made to correspond to N times the lighting frequency of each discharge tube, and luminance ripple can be reduced. it can.

Further, the present invention is an inverter device for driving and lighting each of a plurality of liquid crystal display discharge tubes arranged in a predetermined parallel direction,
Driving means for applying an applied voltage to the discharge tube for driving the discharge tube;
A period T · () obtained by dividing the phase of each applied voltage applied to each discharge tube arranged in the parallel direction by a number N / M obtained by dividing the number N of discharge tubes by a natural number M with respect to one period T of the applied voltage. M / N), and a drive signal generating means for supplying the drive means with drive signals that are sequentially shifted by a phase difference corresponding to M / N).

  According to the present invention, the drive means is supplied with the drive signal from the drive signal generation means, so that the phase of each applied voltage applied to the discharge tubes arranged in the parallel direction is set to one cycle T of the applied voltage. A phase difference corresponding to a divided period T / (N · M) is shifted in order by a number M · N obtained by multiplying the number N of discharge tubes by a natural number M, and is given to each discharge tube. As a result, the sum of the leakage currents leaking from the respective discharge tubes to the adjacent conductors can theoretically be zero, and the generation of noise due to the leakage current can be prevented. In addition, the ground potential can be stabilized, and malfunctions in other control systems can be prevented.

  In the present invention, as the number of discharge tubes increases, the potential difference between adjacent discharge tubes can be reduced. Thereby, even if the creeping distance and the spatial distance are small in the discharge tube arrangement pattern, electrical insulation between the discharge tubes can be achieved. In addition, high electrical terminal voltage guarantee values are not required for the electrical components constituting the display device. Further, by applying the applied voltages with different phases to the corresponding discharge tubes, the lighting frequency of the entire discharge tube can be made to correspond to N / M times the lighting frequency of each discharge tube, and the luminance ripple is reduced. be able to. Further, since it is not necessary to shift the phase of the applied voltage by the same number as the number of discharge tubes, the configuration of the driving means can be simplified as compared with the case where the phase of the applied voltage is shifted by the number of discharge tubes. The natural number M described above is preferably less than N / 2, that is, the phase difference between the applied voltages applied to two adjacent discharge tubes is set to less than 180 degrees.

  According to the present invention, the drive signal generating means makes the phase difference between applied voltages respectively applied to two adjacent discharge tubes 90 degrees or less.

  According to the present invention, by setting the phase difference of the applied voltage to 90 degrees or less, the period in which the potential difference between adjacent discharge tubes exceeds the effective value of the applied voltage is set to ¼ period or less of the applied voltage. be able to. Further, it is possible to prevent the period in which the potential difference between adjacent discharge tubes exceeds the effective value of the applied voltage from overlapping with the period in which the potential difference between the other two discharge tubes exceeds the effective value of the applied voltage. This makes it possible to display an image stably.

  Moreover, the lighting frequency of the whole discharge tube can be made four times or more the lighting frequency of one discharge tube. Therefore, when the lighting frequency of the entire discharge tube is set so that interference fringes and flickering on the display screen can be prevented, the frequency of the applied voltage applied to one discharge tube is 1/4 times the lighting frequency of the entire discharge tube. It will be enough. When the frequency of the applied voltage applied to each discharge tube is ¼, leakage current leaking from each discharge tube can be reduced, and luminance deviation generated in the discharge tube can be reduced.

  In the invention, it is preferable that the drive signal generating means sets a phase difference between applied voltages to two adjacent discharge tubes to 60 degrees or less.

  According to the present invention, the potential difference between adjacent discharge tubes can be made equal to or less than the potential difference between the set potential and the applied voltage by setting the applied voltage phase difference to 60 degrees or less.

  According to the present invention, the drive signal generating means shifts the phase of each applied voltage applied to each discharge tube so that the potential difference between the applied voltages applied to two adjacent discharge tubes is equal to or less than a predetermined allowable potential difference. Features.

  According to the present invention, the electrical insulation in the circuit pattern of the display device can be sufficiently achieved by setting the potential difference between the discharge tubes to a predetermined allowable potential difference or less. Moreover, the guaranteed voltage between terminals of each electrical component can be lowered.

  Further, according to the present invention, the drive signal generating means shifts the phase of each applied voltage applied to each discharge tube so that the total leakage current leaked from each discharge tube to the adjacent conductor is equal to or less than a predetermined allowable current value. It is characterized by that.

  According to the present invention, an image can be stably displayed by setting the total value of leakage currents to be equal to or less than a predetermined allowable current.

  Further, according to the present invention, the driving means can apply the number α of applied voltages having different phases with respect to the frequency f of the applied voltage that can prevent flickering of the discharge tube in a state where the phases of the applied voltages are the same. An applied voltage having a divided frequency f / α is applied to each discharge tube.

  According to the present invention, the lighting timing of each discharge tube can be made different by giving the applied voltage shifted in phase to the corresponding discharge tube, and the lighting frequency of the entire discharge tube can be changed to the lighting for each discharge tube. This can correspond to α times the frequency. Therefore, even if the lighting frequency of the discharge tube is lowered to 1 / N or M / N as in the present invention, the lighting frequency capable of preventing flickering can be achieved as the entire discharge tube. By reducing the lighting frequency of each discharge tube, the leakage current leaking to the adjacent conductor can be reduced. As a result, it is possible to reduce the luminance deviation between the high voltage electrode side and the low voltage electrode side of the discharge tube while preventing flickering of the display image.

The present invention is also characterized in that the number of applied voltages having different phases is an even number.
According to the present invention, by setting the number of applied voltages that have different phases to an even number, it is possible to easily generate applied voltages whose phases are mutually inverted. The two discharge tubes to which applied voltages whose phases are reversed from each other are different in the direction in which the leakage current flows, and the amount of flow is equal. In other words, the current flowing out to the adjacent conductor is equal to the current flowing into the adjacent conductor. As a result, even if the adjacent conductor is disposed in a state insulated from the discharge tube, high voltage can be prevented from being induced in the adjacent conductor.

  In addition, the present invention is characterized by having a connection means for electrically connecting the low-voltage side electrodes of the respective discharge tubes.

  According to the present invention, the feedback cable that electrically connects the low-voltage electrode side terminal of the discharge tube and the driving means can be eliminated, and can be configured at low cost.

Further, the present invention is characterized in that the discharge tube to be driven is a cold cathode fluorescent lamp.
According to the present invention, the driving means is activated by applying electric power having a higher voltage than that of the hot cathode fluorescent lamp in order to drive the cold cathode fluorescent lamp. In the present invention, even if the starting voltage by the driving means is high, the mutual potential difference of the cold cathode fluorescent lamp can be reduced, the leakage current can be reduced, and the screen can be prevented from flickering, and the display quality can be improved.

The present invention also provides a plurality of liquid crystal display discharge tubes arranged in a predetermined parallel direction;
Driving means for applying an applied voltage to the discharge tube for driving the discharge tube;
The phase of each applied voltage applied to each discharge tube arranged in parallel is divided by the number N of discharge tubes with respect to one period T in the applied voltage, or the natural number M in the number N of discharge tubes. Drive signal generation means for supplying a drive signal to the drive means for shifting by a phase difference corresponding to a period T · (M / N) divided by the divided number N / M and selectively transmitting light lit by the discharge tube A liquid crystal display substrate,
And a control unit that controls a light transmission state of the liquid crystal display substrate.

  According to the present invention, the discharge tube driven by the driving means is lit, and the lit light is transmitted through the liquid crystal display substrate. The control means controls the light transmission state of the liquid crystal display substrate based on the image to be displayed. The liquid crystal display substrate can selectively transmit light from the discharge tube and display an image on the image display surface by the light transmitted through the liquid crystal display substrate.

  The driving means applies each applied voltage with the phase shifted to each discharge tube. As a result, the total leakage current that leaks from each discharge tube to the adjacent conductor can be reduced, and the occurrence of noise due to the leakage current can be prevented. In addition, the ground potential can be stabilized, and malfunctions in other control systems can be prevented.

  Further, as the number of driving means increases, the potential difference between adjacent discharge tubes can be reduced. As a result, in the circuit pattern of the display device, electrical insulation between adjacent discharge tubes can be achieved without increasing the creepage distance and the spatial distance.

  Further, by applying the applied voltages having different phases to the corresponding discharge tubes, the lighting frequency of the entire discharge tube can be made to correspond to N times or N / M times the lighting frequency of one discharge tube. As a result, flickering of the display image can be prevented and luminance ripple and luminance deviation can be reduced. In addition, it is preferable that the phase difference of the applied voltage respectively given to two adjacent discharge tubes is set to less than 180 degrees.

  According to the present invention, the sum of leakage currents can theoretically be zero, and noise due to leakage currents can be prevented. In addition, the ground potential can be stabilized, and malfunctions in other control systems can be prevented. Thereby, the operation of the display device on which the inverter device and the discharge tube are mounted can be stabilized, and the display quality can be improved.

  In addition, as the number of applied voltages for different phases is increased, the potential difference between adjacent discharge tubes can be reduced. In the discharge tube arrangement pattern, the creepage distance and the spatial distance are reduced to reduce the mutual discharge tube. The electrical insulation can be achieved. As a result, the interval between the discharge tubes can be reduced, and a large number of discharge tubes can be arranged on the display screen. By arranging a large number of discharge tubes, it is possible to increase the brightness of the display screen, which in turn can increase the size of the display screen.

  In addition to the potential difference between the discharge tubes, the potential difference between the connector terminals and the potential difference between the adjacent substrate patterns can be reduced, so that the display device can be thinned without increasing the creepage distance and the spatial distance. Further, for each electrical component constituting the display device, a component having a low terminal voltage guarantee value can be used, and the manufacturing cost of the display device can be reduced.

  Further, by shifting the phase of each applied voltage, the lighting frequency of the entire discharge tube can be made equal to N times the lighting frequency of each discharge tube. Accordingly, the luminance ripple of the entire discharge tube can be reduced without increasing the frequency of the applied voltage, and interference fringes and flickering of the display screen can be prevented. By reducing the frequency for each applied voltage, the leakage current leaking from the discharge tube can be reduced, and the luminance deviation of the discharge tube can be reduced. Thus, according to the present invention, it is possible to reduce the luminance deviation of the display screen while preventing interference fringes and flickering of the display image, and to improve the display quality of the display screen.

  In addition to shifting the phase of the applied voltage by a phase difference corresponding to a period T / N divided by the number N of discharge tubes with respect to one period T in the applied voltage, The phase difference corresponding to the period T · (M / N) obtained by dividing the number N of discharge tubes by the number N / M divided by the natural number M may be shifted. As a result, the above-described effects can be achieved, and the configuration of the driving means can be simplified.

  In addition, according to the present invention, by setting the phase difference of the applied voltage to 90 degrees or less, the potential difference between adjacent discharge tubes can be set to a period of ¼ period or less during which the effective value of the applied voltage is exceeded. it can. Further, it is possible to prevent a period in which the potential difference between two adjacent discharge tubes exceeds the effective value of the applied voltage from overlapping with a period in which the potential difference between the other two discharge tubes exceeds the effective value of the applied voltage. it can. As a result, the display image can be displayed stably.

  Moreover, the lighting frequency of the whole discharge tube can be made four times or more the lighting frequency of one discharge tube. When the lighting frequency of the entire discharge tube is set so that interference fringes and flickering on the display screen can be prevented, the frequency of the applied voltage applied to one discharge tube is sufficient to be 1/4 times the lighting frequency of the entire discharge tube. It becomes. When the lighting frequency of the entire discharge tube is set to ¼, the leakage current leaked from each discharge tube can be reduced, and thereby the luminance deviation generated in the discharge tube can be sufficiently reduced.

  Further, according to the present invention, by making the applied voltage phase difference 60 degrees or less, the potential difference between the adjacent discharge tubes can be made equal to or less than the potential difference between the ground voltage and the applied voltage. As a result, it is not necessary to increase the withstand voltage performance of each electrical component more than necessary, and the manufacturing cost can be reduced. In addition, the electrical insulation between the discharge tubes can be improved, and it is not necessary to increase the creepage distance and the spatial distance in the circuit pattern of the display device, so that restrictions on the design of the circuit pattern can be reduced. Pattern design can be performed flexibly.

  Further, according to the present invention, the electrical insulation in the circuit pattern of the display device can be sufficiently achieved by setting the potential difference between the discharge tubes to be equal to or less than a predetermined allowable potential difference. Moreover, the guaranteed voltage between terminals of each electrical component can be lowered.

  Further, according to the present invention, by setting the total value of the leakage currents to be equal to or less than a predetermined allowable current amount, the leakage current flows in the closed circuit, and the potential difference ΔV generated by the closed loop impedance component can be reduced. As a result, the generation of noise can be reduced. Further, the ground potential can be stabilized, the ground potential of other control systems can be kept stable, and malfunction of the display device can be prevented. Thereby, the display quality can be further improved.

  According to the present invention, the lighting frequency of each discharge tube can be varied by shifting the phase of the discharge frequency of the discharge tube, and the lighting frequency of the entire discharge tube is α times the lighting frequency of one discharge tube. It can be made to correspond. Therefore, even if the lighting frequency of the discharge tube is lowered to 1 / α as in the present invention, the lighting frequency capable of preventing flickering can be achieved as the entire discharge tube. By reducing the lighting frequency of each discharge tube, the leakage current leaking to the adjacent conductor can be reduced. As a result, it is possible to reduce the luminance deviation between the high voltage electrode side and the low voltage electrode side of the discharge tube while preventing flickering of the display image.

  Further, according to the present invention, by setting the number of applied voltages that vary the phase difference to an even number, the leakage current that flows out from the entire discharge tube to the adjacent conductor and the leakage current that flows into the adjacent conductor are reduced. Can be easily equalized. As a result, even if the proximity conductor is arranged in a state insulated from the closed circuit of the display device, it is possible to prevent a high voltage from being induced in the proximity conductor, and when the proximity conductor comes into contact with another proximity conductor. Generation of contact discharge noise can be prevented.

  According to the present invention, the feedback cable for electrically connecting the low voltage electrode side terminal of the discharge tube and the driving means can be eliminated, and the image display apparatus can be formed at low cost.

  Further, according to the present invention, even for a cold cathode fluorescent lamp that requires a high voltage to start up, it is possible to reduce the mutual potential difference of the cold cathode fluorescent lamp, reduce the leakage current, and prevent the screen from flickering. . The cold cathode fluorescent lamp is smaller than the hot cathode fluorescent lamp. Therefore, the use of a cold cathode fluorescent lamp in a display device can make the display device thinner.

  Further, according to the present invention, the driving means constituting the liquid crystal display device applies the applied voltages whose phases are shifted to the corresponding discharge tubes. As a result, leakage currents leaking from the respective discharge tubes to the adjacent conductors flow in opposite directions to cancel each other, and generation of noise due to the leakage current can be prevented. In addition, the ground potential can be stabilized, and malfunctions in other control systems can be prevented.

  Moreover, the potential difference between the adjacent discharge tubes can be reduced as the number of applied voltages for different phases is increased. Thereby, in the circuit pattern of the display device, the electrical insulation of the display device can be achieved without increasing the creepage distance and the spatial distance.

  Furthermore, the application timings of the respective discharge tubes can be made different by individually applying the applied voltages having different phases to the respective discharge tubes. Therefore, the lighting frequency of the entire discharge tube can be made to correspond to N times or N / M times the lighting frequency of one discharge tube. As a result, flickering of the display image can be prevented.

  FIG. 1 is a block diagram for explaining an inverter device 50 according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a liquid crystal display device 11. The inverter device 50 of the present invention constitutes a part of the liquid crystal display device 11. The liquid crystal display device 11 includes a liquid crystal display substrate 12, a chassis 14 serving as a casing, a plurality of discharge tubes L1 to L4 that emit a backlight 13, and an electric circuit for supplying AC power to the discharge tubes L1 to L6. Group 15. The electric circuit group 15 includes a DC converter that converts AC current supplied from a commercial power source into DC power, and an inverter device 50 that converts DC current converted by the DC converter into AC power for driving a discharge tube. . Hereinafter, the discharge tubes L1 to L6 are referred to as lamps L1 to L6.

  The inverter device 50 applies AC power to each lamp L to drive each lamp L to light. Each lit lamp L irradiates the backlight 13 to the liquid crystal display substrate 12. The liquid crystal display substrate 12 partially switches the transmission state of the backlight 13 among the light receiving surfaces irradiated with the backlight 13. Accordingly, the liquid crystal display device 11 selectively transmits the backlight 13 to the liquid crystal display substrate 12 and displays an image on the image display surface by the transmitted light.

  The liquid crystal display device 11 is desired to improve the brightness and size of the display screen. In order to improve the brightness of the displayed image, a plurality of lamps L are arranged in parallel in a predetermined parallel direction X along the display surface of the liquid crystal display substrate 12 so as to face the liquid crystal display substrate 12. Further, the lamp is lengthened in order to enlarge the display screen.

  FIG. 3 is a block diagram illustrating the liquid crystal display device 11 including the inverter device 50. The liquid crystal display device 11 means, for example, a television receiver having a liquid crystal monitor and a personal computer having a liquid crystal monitor.

  The liquid crystal display device 11 includes an inverter device 50, a DC conversion device 6, a plurality of lamps L, a liquid crystal display substrate 12, an image processing circuit 7, a liquid crystal driver 8, and a speaker 9. The DC converter 6 acquires the commercial AC power supplied from the commercial power supply 10 as described above, and converts it to DC power having a predetermined voltage. The DC converter 6 gives the converted DC power to the inverter device 50, the image processing circuit 7, the liquid crystal driver 8, the speaker 9, and the like.

  When the liquid crystal display device 11 is a television receiver, the receiver receives image data and audio data. When the liquid crystal display device 11 is a personal computer, image data and audio data are generated by a CPU (Central Processing Unit). In this way, the liquid crystal display device 11 acquires image data and audio data to be displayed by some acquisition means, and gives the acquired image data to the image processing circuit 7. The image processing circuit 7 generates a pixel signal corresponding to the given image data. The pixel signal is generated for each pixel constituting the image represented by the image data. The image processing circuit 7 is realized by, for example, an LSI (Large-Scale Integration).

  The image processing circuit 7 gives the generated pixel signals to the liquid crystal driver 8. The liquid crystal driver 8 controls the liquid crystal display substrate 12 in accordance with each given pixel signal to partially change the light transmission state of the liquid crystal display substrate 12. Each lamp L irradiates the liquid crystal display substrate 12 with irradiation light to be the backlight 13. At this time, the light transmission state of the liquid crystal display substrate 12 is partially changed according to the image to be displayed by the liquid crystal driver 8. Accordingly, the light from each lamp L is selectively transmitted through the liquid crystal display substrate 12 in accordance with the image to be displayed and is emitted from the liquid crystal display substrate 12. When the emitted light emitted from the liquid crystal display substrate 12 reaches the display screen, an image is displayed on the display screen. The liquid crystal driver 8 serves as control means for controlling the transmission state of the liquid crystal display substrate 12.

  In the liquid crystal display device 11, an audio processing circuit (not shown) generates the acquired audio data as an audio signal, and gives the audio signal to the speaker 9. The speaker 9 emits a sound to be generated by receiving a sound signal. An audio processing circuit is also one of DC drive devices.

  Inverter device 50 changes the direct-current power given from direct-current converter 6 to the drive voltage and drive frequency of each lamp L, and outputs it. For example, the effective value of the voltage output from inverter device 50 is set to 1000 Vrms (root mean square). The predetermined frequency is set to 40 kHz.

  Hereinafter, a case where the six lamps L1 to L6 are provided in the liquid crystal display device 11 will be described. As shown in FIG. 1, the inverter device 50 includes a plurality of lamp driving circuits 51 provided for each of the lamps L <b> 1 to L <b> 6 and a driving signal generator 52 that supplies a driving signal to each lamp driving circuit 51. Each lamp drive circuit 51 applies AC applied power to the corresponding lamp L. The drive signal includes information representing the phase of the applied voltage output from each lamp drive circuit 51. When the driving signal is supplied from the driving signal generator 52, the lamp driving circuit 51 generates an applied voltage having a predetermined phase and frequency according to the driving signal and supplies the generated voltage to the corresponding lamp L. Thus, the lamp driving circuit 51 serves as driving means for applying an applied voltage for driving the lamp, and the driving signal generator 52 serves as driving signal generating means for providing a driving signal to the lamp driving circuit 51.

  Each lamp L is a discharge tube, and is realized by a cold cathode fluorescent lamp in the present embodiment. Each lamp L is a direct type lamp that illuminates the liquid crystal display substrate 12 from the back side. Each lamp L is formed in a cylindrical shape extending in the longitudinal direction, and electrode terminals 76 and 79 are formed at both ends in the longitudinal direction. As described above, the lamps L are arranged in the parallel direction X. The parallel direction X extends in a direction perpendicular to the longitudinal direction of each lamp L. Each lamp L is lit by applying a high-frequency and high-voltage applied voltage between the electrode terminals 76 and 79 of the lamp L. The lighting cycle T of the lamp L substantially coincides with the frequency T of the applied voltage VL.

  The lamp drive circuit 51 includes an AC converter 51a and a voltage converter 51b. The AC converter 51a receives a DC voltage from the DC converter 6 and converts it into an AC voltage having a predetermined frequency. The predetermined frequency is a frequency necessary for driving the lamp L. The AC converter 51a gives the converted AC voltage to the voltage converter 51b. The voltage converter 51b receives the AC voltage from the AC converter 51a and boosts it to a predetermined voltage. This predetermined voltage is a voltage necessary for driving the lamp L. The voltage converter 51b gives the boosted AC voltage to the lamp L. The AC conversion unit 51a can change the phase of the AC voltage to be output when the drive signal is supplied from the drive signal generator 52.

  For example, the AC conversion unit 51a is realized by a converter circuit such as a single push-pull circuit, a half bridge circuit, or a full bridge circuit. The voltage converter 51b is realized by a high voltage transformer circuit. The drive signal generator 52 can be configured by a gate array, a PLD (Programmable Logic Device), or a microcomputer. The circuit configuration for realizing the above-described AC converter 51a, voltage converter 51b, and drive signal generator 52 is an example. Therefore, the AC converter 51a, the voltage converter 51b, and the drive signal generator 52 may be realized by other circuit configurations not described above.

  In order to transmit the phase-shifted drive signal to the AC converter 51a, two signal lines are required in the push-pull circuit and the half-bridge circuit, and four signal lines are required in the full-bridge circuit and the like. It is. FIG. 1 shows a state in which a phase-shifted drive signal is supplied to each drive circuit by one signal line for easy understanding.

  The drive signal generator 52 shifts the phase of the applied voltage VL output from each lamp drive circuit 51 by a phase difference corresponding to a period obtained by dividing the phase of the applied voltage by N, which is the number of lamps L, for one cycle T of the applied voltage. A drive signal is supplied to the lamp drive circuit 51, respectively. In other words, the phase of the applied voltage is sequentially shifted by (one cycle / number of lamp driving circuits). In other words, the phase of each applied voltage VL applied to each of the lamps L1 to L6 arranged in the parallel direction X corresponds to a period T / N divided by the number N of discharge tubes with respect to one period T in the applied voltage. Each phase difference is shifted sequentially.

  Specifically, when there are N lamps L, the phase of the applied voltage output from each lamp driving circuit 51 is sequentially shifted by 2π / N radians. The two lamps L adjacent to each other in the parallel direction X are set so that the phase of the applied voltage applied to the other lamp in the parallel direction X is delayed by 2π / N radians with respect to the phase of the applied voltage applied to the other lamp in the parallel direction X. Is done. Further, as another modification, it may be set to advance by 2π / N radians.

  For example, when the liquid crystal display device 11 has six lamps L and the first lamp L1 to the sixth lamp L6 are arranged from one side in the parallel direction X to the other side in the parallel direction X, the first application applied to the first lamp L1. The phase of the second applied voltage VL2 applied to the second lamp L2 is delayed by 60 degrees (π / 3 radians) with respect to the voltage VL1. Further, the phase of the third applied voltage VL3 applied to the third lamp L3 is delayed by 120 degrees (2 · π / 3 radians) with respect to the first applied voltage VL1 applied to the first lamp L1. Further, the phase of the fourth applied voltage VL4 applied to the fourth lamp L4 is delayed by 180 degrees (π radians) with respect to the first applied voltage VL1 applied to the first lamp L1. Further, the phase of the fifth applied voltage VL5 applied to the fifth lamp L5 is delayed by 240 degrees (4 · π / 3 radians) with respect to the first applied voltage VL1 applied to the first lamp L1. Further, the phase of the sixth applied voltage VL6 applied to the sixth lamp L6 is delayed by 300 degrees (5 · π / 3 radians) with respect to the first applied voltage VL1 applied to the first lamp L1.

  FIG. 4 is a time chart showing drive signals that the drive signal generator 52 gives to the lamp drive circuits 51, respectively. The drive signal generator 52 gives different drive signals to the lamp drive circuits 51. As shown in FIG. 4, the drive signal is a pulse signal. In this case, the drive signal repeats an on state and an off state at a constant period T, and the signal waveform with the passage of time becomes a rectangular wave. The drive signal generator 52 provides each lamp drive circuit 51 with a drive signal that is phase-shifted evenly during one cycle of the drive signal for each lamp drive circuit 51.

  The lamp driving circuits 51 corresponding to the first to sixth lamps L1 to L6 are first to sixth lamp driving circuits 51, and a period (T / N) obtained by dividing the cycle T of the driving signal by the number N of lamps is delayed. Let it be period t. The drive signal generator 52 delays the phase of the second drive signal applied to the second lamp drive circuit 51 with respect to the first drive signal applied to the first lamp drive circuit by a delay period t. The phase of the third drive signal applied to the third lamp drive circuit 51 is delayed by the delay period t, the phase of the fourth drive signal applied to the fourth lamp drive circuit 51 is delayed by the delay period t relative to the third drive signal, and the fourth The phase of the fifth drive signal applied to the fifth lamp drive circuit 51 is delayed with respect to the drive signal by a delay period t, and the phase of the sixth drive signal applied to the sixth lamp drive circuit 51 is delayed with respect to the fifth drive signal. Delay period t.

  FIG. 5 is a time chart showing applied voltages VL <b> 1 to VL <b> 6 output from each lamp drive circuit 51 when the drive signal shown in FIG. 4 is given to each lamp drive circuit 51. When the first to sixth lamp driving circuits 51 are respectively provided with driving signals whose phases are sequentially shifted, the first to sixth applied voltages VL1 to VL6 output from the first to sixth lamp driving circuits 51 are also phased. Shift sequentially. The first to sixth applied voltages VL <b> 1 to VL <b> 6 are repeatedly increased and decreased at a constant cycle, and the signal waveform with the passage of time becomes a sine wave.

  Therefore, the phase of the second applied voltage VL2 is delayed by the delay period t as compared with the first applied voltage VL1. The phase of the third applied voltage VL3 is delayed by the delay period t compared to the second applied voltage VL2. The phase of the fourth applied voltage VL4 is delayed by the delay period t compared to the third applied voltage VL3. The phase of the fifth applied voltage VL5 is delayed by the delay period t as compared to the fourth applied voltage VL4. The phase of the sixth applied voltage VL6 is delayed by the delay period t compared to the fifth applied voltage VL4.

  FIG. 6 is a graph showing leakage currents leaking from the lamps L, respectively. FIG. 7 is a graph showing the combined leakage current obtained by adding the leakage currents. Since the applied voltage VL applied to the lamp L is a high-frequency and high-voltage sine wave AC voltage, a current leaks from the lamp L to the adjacent conductor 2 as a leakage current due to the distributed capacitance parasitic on the lamp L. The proximity conductor 2 is, for example, a rear metal chassis disposed to face each lamp L. As described above, the applied voltages VL1 to VL6 whose phases are sequentially shifted are applied to the lamps L, respectively. Accordingly, the first to sixth leakage currents leaking from the first to sixth lamps L1 to L6 to the adjacent conductor 2 also have a phase difference. As shown in FIG. 6, at an arbitrary time, there is a leakage current flowing from the lamp L toward the adjacent conductor 2 and a leakage current flowing from the adjacent conductor 2 toward the lamp L. Therefore, the combined leakage current is theoretically zero as each leakage current is canceled out. Actually, as shown in FIG. 7, the combined leakage current does not completely become zero but flows by a minute amount. Further, when the total current value of leakage currents leaking from the respective discharge tubes to the adjacent conductors is determined in advance, the phase difference is preferably determined so as to be equal to or less than the determined total current value.

  FIG. 8 is a block diagram showing a case where the proximity conductor 2 has a floating structure. When the proximity conductor 2 is insulated from the closed circuit including the lamp L, the first to third leakage currents flow from the first to third lamps L1 to L3 to the proximity conductor 2, whereas the fourth to fourth The sixth leakage current flows from the adjacent conductor 2 to the fourth to sixth lamps L4 to L6. As a result, the current flowing into the adjacent conductor 2 as a whole is canceled out, and a high voltage is not induced in the adjacent conductor 2, so that safety can be improved.

  FIG. 9 is a graph showing a potential difference between two adjacent applied voltages, and FIG. 9 (1) shows a time change between the first applied voltage VL1 and the second applied voltage VL2. FIG. 9B shows the potential difference between the first applied voltage VL1 and the second applied voltage VL2.

For example, when there is a phase difference Δθ between the first applied voltage VL1 and the second applied voltage VL2, the maximum potential difference Vdef between the first lamp L1 and the second lamp L2 is obtained by the following equation.
Vdef = VL × | 2 · Sin (Δθ / 2) | (1)
In the above formula, Vdef represents a potential difference between the first lamp L1 and the second lamp L2. VL represents the effective value of the first applied voltage VL1 and the second applied voltage VL2. Δθ represents a phase difference between the first applied voltage VL1 and the second applied voltage VL2.

  Assuming that VL = 1500 Vrms, the maximum potential difference between the lamps is 0 V when the phase difference Δθ = 0 °, the maximum potential difference between the lamps is 1148 V when the phase difference Δθ = 45 °, and the maximum between the lamps when the phase difference Δθ = 60 °. When the phase difference Δθ = 90 °, the maximum potential difference between the lamps is 2121 V, and when the phase difference Δθ = 180 °, the maximum potential difference between the lamps is 3000 V. Therefore, six or more lamp driving circuits 51 are provided, and the phase difference between the applied voltages VL1 to VL6 output from each lamp driving circuit 51 is set to 60 degrees or less, so that the two adjacent lamps L can be connected to each other. The potential difference Vdef can be suppressed below the potential difference VL between the lamp L and the ground potential.

  In the present embodiment, as described above, the phase difference between applied voltages applied to two adjacent lamps L is 60 degrees. Therefore, the potential difference between the two adjacent lamps L can be suppressed to be equal to or less than the potential difference between the lamp and the ground potential. FIG. 9 shows only the first applied voltage VL1 and the second applied voltage VL2, but the same applies to the other applied voltages VL3 to VL6. When the potential difference between the applied voltages applied to two adjacent discharge tubes is predetermined, it is preferable that the phase difference is determined so as to be equal to or less than the predetermined allowable potential difference.

  FIG. 10 is a graph showing the time change of each lamp current of the present invention and the time change of the total luminance obtained by adding the luminances of all the lamps. FIG. 10 (1) shows the time change of each lamp current, and FIG. 10 (2) shows the time change of the total luminance obtained by adding the luminances of all the lamps. In each lamp L, the phases of the applied voltages VL1 to VL6 applied are shifted from each other. Therefore, for each lamp, the phases of the first to sixth lamp currents flowing in the lamp are also shifted. The timing of lighting for each lamp varies depending on the phase of each lamp current. When the brightness of one lamp is low, the brightness of the other lamp is high. As a result, as shown in FIG. 10 (2), the luminance ripple which is the difference between the lower limit value and the upper limit value of the luminance value of the entire lamp can be reduced. Further, the lighting frequency of the entire lamp can be made to correspond to N times the lighting frequency of each lamp. Therefore, flickering of the display image can be suppressed.

  FIG. 11 is a graph showing a temporal change of each lamp current of the comparative example and a temporal change of luminance obtained by adding the luminances of all the lamps of the comparative example. FIG. 11 (1) shows the time change of each lamp current, and FIG. 11 (2) shows the time change of the total luminance obtained by adding the luminances of all the lamps. The lamps of the comparative examples are in phase with the applied voltage applied. In this case, when the luminance of one lamp becomes low, the luminance of the other lamps also becomes low. Therefore, as shown in FIG. 11 (2), the luminance ripple becomes large and the display image tends to flicker.

  As described above, according to the inverter device 50 according to the first embodiment of the present invention, the applied voltages applied to the plurality of lamps L are sequentially given phase differences corresponding to the parallel direction X in which the lamps L are arranged. . As a result, the sum of the leakage currents leaking from the lamps L to the adjacent conductors 2 can theoretically be zero, and the generation of noise due to the leakage current can be prevented. In addition, the ground potential can be stabilized, and malfunctions in other control systems can be prevented. Therefore, the operations of the inverter device 50 and the liquid crystal display device 11 can be stabilized, and the display quality can be improved.

  In the present embodiment, the number of lamps L is six. However, as the number of lamps L increases, the potential difference between the lamps L adjacent in the parallel direction X can be reduced. Thereby, even if the creeping distance and the spatial distance are small in the arrangement pattern of the lamp L, electrical insulation between the discharge tubes can be achieved. Therefore, the lamp driving circuits 51, the lamps L, the connectors for connecting the lamp driving circuits 51 and the lamps L, and the like can be arranged close to each other, and the liquid crystal display device 11 can be thinned.

  Further, the lamps L can be densely arranged on the back surface of the liquid crystal display substrate 12, and many lamps L can be arranged on the liquid crystal display substrate 12. By disposing many lamps L, it is possible to increase the luminance of the display screen, reduce unevenness in luminance, and consequently increase the size of the display screen.

  Further, by reducing the potential difference between the lamps, a high inter-terminal voltage compensation value is not required for the electrical components constituting the liquid crystal display device 11. Further, by applying the applied voltages VL1 to VL6 with the phases shifted to the corresponding lamps L, as shown in FIG. 10 (2), the lighting timing of each lamp L can be made different, and the lighting frequency of the entire lamp can be set. This can correspond to N times the lighting frequency for each lamp. As a result, the luminance ripple of the entire lamp can be reduced, and the display quality can be improved.

  Conventionally, the lighting frequency for each lamp is increased to prevent interference fringes and flickering. In the embodiment of the present invention, the lighting frequency of the entire lamp can be increased without increasing the lighting frequency for each lamp. As a result, the frequency of the applied voltage can be made lower than in the prior art to prevent interference fringes and flickering on the liquid crystal display screen. Thus, the leakage current of the lamp L can be reduced by reducing the frequency of the applied voltage.

  In this case, the frequency f obtained by dividing the frequency f of the applied voltage VL that can prevent the flickering of the discharge tube with the phase of each applied voltage VL being the same phase by the number α of applied voltages having different phases. Even if the lighting frequency of the lamp L is reduced to 1 / N by applying an applied voltage of / α to each lamp L, the entire discharge tube has a lighting frequency that can prevent interference fringes and flickering of the liquid crystal image. Can be reliably achieved. Further, by reducing the lighting frequency of each lamp L, the leakage current leaking to the adjacent conductor 2 can be reduced. As a result, flickering of the display image can be prevented, and a luminance deviation between the high voltage electrode side and the low voltage electrode side of the lamp L can be reduced.

  Further, by setting the phase difference between the applied voltages VL1 to VL6 applied to each lamp L to 90 degrees or less, a period in which the potential difference between the adjacent lamps exceeds the effective value of the applied voltage VL is set to ¼ period of the applied voltage VL. It can be: Further, it is possible to prevent the period in which the potential difference between adjacent lamps L exceeds the effective value of the applied voltage VL from overlapping with the period in which the potential difference between the other two lamps L exceeds the effective value of the applied voltage VL. This makes it possible to display an image stably.

  Further, by setting the phase difference between the applied voltages VL1 to VL6 applied to each lamp L to 60 degrees or less, the potential difference between the adjacent lamps L can be made to be less than the potential difference between the ground potential and the applied voltage. Accordingly, it is not necessary to increase the withstand voltage performance of each electrical component more than necessary, and the manufacturing cost of the liquid crystal display device 11 can be reduced. Further, it is possible to improve the electrical insulation between the lamps L, it is not necessary to increase the creepage distance and the spatial distance in the circuit pattern of the display device, and restrictions on the design of the circuit pattern can be reduced. Pattern design can be performed flexibly.

  Further, even if the phase difference between the applied voltages VL1 to VL6 applied to each lamp L is not 60 degrees or less, the phase difference between the applied voltages is set so that the potential difference between the lamps is not more than a predetermined allowable potential difference. The electrical insulation in the circuit pattern of the device can be sufficiently achieved. Similarly, even if the phase difference between the applied voltages VL1 to VL6 applied to each lamp L is not 60 degrees or less, each applied voltage is set so that the total leakage current leaked from the lamp is not more than a predetermined allowable total leakage current value. By setting the phase difference, it is possible to display an image stably.

  In addition, by setting the number of applied voltages VL that vary in phase to an even number, it is possible to easily generate the applied voltages VL whose phases are mutually inverted. The two lamps L to which the applied voltages VL whose phases are inverted from each other are different in the direction in which the leakage current flows, and the amount of flow is equal. In other words, the leakage current that flows out to the adjacent conductor 2 is equal to the leakage current that flows into the adjacent conductor 2. Even if the adjacent conductor 2 is arranged in an insulated state, it is possible to prevent high voltage from being induced in the adjacent conductor. Further, it is possible to prevent the occurrence of contact discharge noise when the proximity conductor 2 comes into contact with another proximity conductor.

The lamp L is realized by a cold cathode fluorescent lamp. In order to drive a cold cathode fluorescent lamp, it is necessary to start it by applying a higher voltage power than a hot cathode fluorescent lamp, and its leakage current also increases. In the present invention, as described above, it is possible to reduce the mutual potential difference of the lamp, reduce the leakage current, and prevent the flickering of the screen, so that the display quality can be improved even with a cold cathode discharge tube. By using a cold cathode fluorescent lamp, the liquid crystal display device can be thinned.
Table 1 summarizes the drive operation of the prior art and the relationship between one embodiment of the present invention.

  As described above, according to the inverter device 50 according to the first embodiment of the present invention, each lamp driving circuit 51 is sequentially driven by phase shift with a phase difference of a period corresponding to one cycle / (the number of lamp driving circuits). Therefore, the combined leakage current, the mutual potential difference between the lamps, the flickering of the screen and the brightness deviation can be reduced, and many electrical, optical and economical problems can be solved. A circuit can be configured.

  On the other hand, the conventional inverter devices 1, 3 and 4 cannot achieve the effect as in the present embodiment. In the above-described embodiment, the applied voltage applied to the lamp on the other side in the parallel direction X is delayed by a predetermined phase difference with respect to the applied voltage applied to the lamp on the one side in the parallel direction X. Even if it is advanced, the same effect can be obtained.

  FIG. 12 is an electric circuit showing an example of the lamp driving circuit 51. The AC conversion unit 51 a has two input terminals 55 and 57. One input terminal 55 is connected to the input line 58, and the other input terminal 57 is connected to the ground potential line 56. The ground potential line 56 is set to a predetermined ground potential. The input line 58 is set by the DC converter 6 so as to have a predetermined potential difference with respect to the ground potential. The AC conversion unit 51 a has two output terminals 59 and 60. The AC converter 51a generates an AC sine wave potential difference corresponding to the applied voltage VL between the two output terminals 59 and 60.

  The voltage conversion unit 51 b has two input terminals 80 and 81 and two output terminals 82 and 83. One input terminal 80 of the voltage conversion unit 51 b is electrically connected to one output terminal 59 of the AC conversion unit 51 through the first connection line 84. The other input terminal 81 of the voltage conversion unit 51 b is electrically connected to the other output terminal 60 of the AC conversion unit 51 by the second connection line 85. The voltage conversion unit 51b boosts the potential difference applied between the input terminals 80 and 81 of the voltage conversion unit 51b and generates the boosted potential difference between the output terminals 82 and 83. One output terminal 82 of the voltage conversion unit 51 b is electrically connected to one electrode 76 of the lamp by a first output line 86. The other output terminal 83 of the voltage conversion unit 51 b is electrically connected to the other electrode 79 of the lamp by the second output line 87. Further, one of the first output line 86 and the second output line 87 may be electrically connected to the ground line 56 by a connection line 88 as shown in FIG.

  For example, the AC conversion unit 51a includes the capacitor C2 and the two switching elements Tr1 and rL2 to configure a push-pull type AC conversion circuit, thereby realizing the converter circuit 100. In addition to the converter circuit 100, the AC converter 51 a includes a transformer circuit 101 having a first transformer 90.

  In the present embodiment, the two switching elements Tr1 and Tr2 are realized by an enhancement type MOS transistor and a feedback diode connected in antiparallel to the transistor. Each of the switching elements Tr1 and Tr2 switches the conduction state based on a signal given from the drive signal generator 52. As a result, the AC converter 51a can generate alternating power having an arbitrary frequency and phase based on the signal from the drive signal generator 52. The alternating power includes those whose voltage waveform is a sine waveform and those whose waveform is a rectangular waveform.

  Specifically, the converter circuit 100 is formed with a center tap, and has two input terminals 55 and 57, two output terminals 92 and 94, and a center output terminal 93. The input terminals 55 and 57 of the converter circuit 100 coincide with the two input terminals 55 and 57 as the AC converter 51a.

  The converter circuit 100 includes a first line 108 that connects one input terminal 55 and the center output terminal 93, and a second line 109 that connects the other input terminal 57 and the two output terminals 92 and 94. In the second line 109, a branch point 110 is formed, and branch portions 109a and 109b branching into two from the branch point 110 are formed. One branch portion 109 a is connected to one of the output terminals 92 and 94, and the other branch portion 109 b is connected to the other 94 of the output terminals 92 and 94.

  The switching elements Tr2 and Tr3 are connected in series to the branch portions 109a and 109b of the second line 109, respectively. One switching element Tr2 short-circuits the other input terminal 27 and the output terminal 92 connected to the branching portion 109a by connecting the branching portion 109a of the corresponding second line 109 in the ON state. One switching element Tr2 turns off the branch portion 109a of the corresponding second line 109 in the OFF state, and opens the other input terminal 57 and the output terminal 92 connected to the branch portion 109a. The same applies to the other switching element Tr3.

  The converter circuit 100 has a third line 111 that connects the branch portions 109a and 109b of the second line 109 closer to the output terminals 92 and 93 than the switching elements Tr2 and Tr3. The capacitor C <b> 2 is interposed in the third line 111 and is connected in series to the third line 111. The drive signal generator 52 applies a drive signal to each of the two switching elements Tr2 and Tr3 so as to have a predetermined frequency, operates in conjunction with each other, and adjusts the on / off ratio thereof. When one of the two switching elements Tr is turned on, the drive signal generator 52 turns the other one off.

  The first transformer 90 constituting the transformer circuit 101 transforms the alternating power generated by the converter circuit 100. The first transformer 90 includes a primary winding 61 extending in a coil shape, a secondary winding 64 extending in a coil shape, and a core that passes through the primary winding 61 and the secondary winding 64 along the central axis thereof. 66. The core 66 is made of a magnetic material and is realized by, for example, an iron core. When an alternating current flows through the primary winding 61, the magnetic flux in the core changes, thereby generating an electromotive force in the secondary winding 64. By adjusting the turn ratio between the primary winding 61 and the secondary winding 64, the electromotive force generated in the secondary winding 64 can be transformed with respect to the power supplied to the primary winding 61.

  One end 62 of the primary winding 61 of the first transformer 90 is connected to one output terminal 92 of the converter circuit 100. The other end 63 of the primary winding 61 of the first transformer 90 is connected to the other output terminal 94 of the converter circuit 100. Further, a center output terminal 93 of the converter circuit 100 is connected to a substantially central portion 113 of the coiled portion of the primary winding. One end portion 65 of the secondary winding 64 of the first transformer 90 is connected to one of the two output terminals 59 and 60 serving as the AC converter 51a. The other end 69 of the secondary winding 64 of the first transformer 90 is connected to one 60 of the two output terminals 59 and 60 serving as the AC converter 51a.

  The drive signal generator 52 alternately switches the on / off states of the two switching elements Tr2 and Tr3, whereby a current flows alternately in the branch portions 109a and 109b of the second line 109, and the primary winding of the first transformer 90 The direction of the current flowing through 61 is switched. The drive signal generator 52 can apply an alternating current to the primary winding 61 of the first transformer 90 by switching the on / off states of the switching elements Tr2 and Tr3 in a predetermined cycle. The converter circuit 100 can reduce the current flowing through the converter circuit 100 by switching high-voltage DC power compared to the commercial AC voltage, and can reduce power loss in the converter circuit 100.

  In the present embodiment, DC voltage of 140 V to 380 V is applied to converter circuit 100 from DC power generation device 6. The converter circuit 100 converts the DC power into a frequency of 35 kHz to 70 kHz, for example, 40 kHz AC power, in order to maintain stable lighting of the lamp L and good liquid crystal image quality. The voltage waveform of the AC power output from the converter circuit 100 is a rectangular waveform. First transformer 90 steps down AC power supplied from converter circuit 100 by 0.035 to 0.07 times. As a result, the voltage waveform of the electric power output from the first transformer 90 becomes an alternating waveform of 12 to 40V0-P, for example, a rectangular waveform alternating between 12V and -12V. The AC conversion unit 51 a generates an AC sine wave potential difference between the two output terminals 59, 60 between the output terminals 59, 60.

  The voltage conversion unit 51b includes a second transformer 91. The second transformer 91 has a configuration corresponding to the first transformer 90 except that the turns ratio of the primary winding 67 and the secondary winding 73 is different. One end 68 of the primary winding 67 of the second transformer 91 is connected to one output terminal 80 of the voltage converter 51b. The other end 71 of the primary winding 67 of the second transformer 91 is connected to the other output terminal 81 of the voltage converter 51b. One end 74 of the secondary winding 73 of the second transformer 91 is connected to one of the two output terminals 82 and 83 of the voltage conversion unit 51b. The other end 77 of the secondary winding 73 of the second transformer 91 is connected to the other 83 of the two output terminals 82 and 83 of the AC converter 51b. In FIG. 12, the leakage inductance of the second transformer 91 is indicated by reference numeral 73a.

  When an alternating current flows through the primary winding 61 of the first transformer 90 and the secondary winding 64 of the first transformer 90 extracts AC power, the primary winding 67 of the second transformer 91 includes AC current flows. The winding ratio between the primary winding 67 and the secondary winding 73 of the second transformer 90 is appropriately set in advance to transform the secondary winding 73 of the second transformer 91 to a predetermined voltage. AC power can be taken out. The AC power extracted from the secondary winding 73 of the second transformer 91 is converted AC power that can drive the lamp L.

  A line connecting one end 65 and the other end 69 of the secondary winding 64 of the first transformer 90 and one end 74 and the other end 77 of the secondary winding 73 of the second transformer 91 are connected. Any of the lines to be connected may be provided, and a capacitor for waveform rectification may be provided on the line. By providing the capacitor for waveform rectification, the lamp driving circuit 51 can include a low-pass filter circuit, and the harmonic component can be removed from the waveform of the applied voltage applied to the lamp L to prepare a sine wave signal. it can. Thereby, the operation of the lamp can be stabilized.

  In the voltage converter 51b, a DC superposition prevention capacitor 72 is interposed in series between one input terminal 80 of the voltage converter 51b and one end 68 of the primary winding 67 of the second transformer 91. . As a result, the direct current component of the current flowing through the primary winding 67 of the second transformer 91 is removed. Then, it is possible to prevent DC superposition from occurring in the second transformer 91 and to prevent an excessive current from flowing in each circuit constituting the liquid crystal display device 11.

  Further, the DC voltage applied to converter circuit 100 is preferably as high as possible as long as it is equal to or lower than the allowable withstand voltage value of converter circuit 100. As a result, the current flowing through the converter circuit 100 and the transformer circuit 101 can be reduced, and the heat generation of each circuit can be suppressed.

  The lamp drive circuit 51 as described above is provided for each lamp, and a common drive signal is given from a common drive signal generator 52. As a result, the phase of the applied voltage generated in each lamp driving circuit 51 can be made different. Such a lamp driving circuit 51 is an example of implementation of the present invention, and the lamp driving circuit 51 may be realized by other circuit configurations.

  For example, the lamp driving circuit 51 may further include a lamp current detection circuit that detects a lamp current flowing from the lamp L. The lamp current detection circuit detects a lamp current flowing through the lamp L and generates a lamp current signal representing the detected current. The lamp current detection circuit provides a lamp current signal to the drive signal generator 52. The drive signal generator 52 performs error amplification based on the lamp current signal supplied from the lamp current detection circuit and feedback-controls the on / off ratio of the switching element. As a result, the lamp current flowing through the lamp L can be stabilized.

  FIG. 13 is a block diagram for explaining an inverter device 150 according to the second embodiment of the present invention. The inverter device 150 of the second form is similar to the inverter device 50 of the first form, and has the same configuration except that the connection state of each lamp is different. Therefore, a different structure from the inverter apparatus 50 of the 1st form is demonstrated, the same referential mark is attached | subjected about the same structure, and the description is abbreviate | omitted.

  The lamp driving circuit 51 has two output terminals 82 and 83, and generates an AC sine wave potential difference corresponding to the applied voltage VL between the output terminals 82 and 83. The lamp driving circuit 51 and the lamp L are connected by an output line 86 capable of electrical conduction. Specifically, one output terminal 82 of the lamp driving circuit 51 and one output terminal 76 of the lamp L are electrically connected by the first output line 86. A ground line 88 is electrically connected to the other output terminal 83 of the lamp driving circuit 51 and a ground potential. The other output terminal 79 of each lamp L is electrically connected by a feedback line 89.

  A combined leakage current obtained by combining the lamp currents flowing through the lamps L flows through the feedback line 89. Here, in the present embodiment, the phase between the first applied voltage VL1 and the fourth applied voltage VL4, the phase between the second applied voltage VL2 and the fifth applied voltage VL5, the third applied voltage VL3 and the sixth applied voltage VL6, The phases are reversed. As a result, the first lamp current is canceled by the fourth lamp current, the second lamp current is canceled by the fifth lamp current, and the third lamp current is canceled by the sixth lamp current. Therefore, even if the feedback line 89 and the ground line 88 are connected, the current flowing from the feedback line 89 to the connection line 88 becomes zero. Therefore, it is not necessary to connect the other output terminal 79 of each lamp L and the ground line 88. As a result, it is possible to simplify the structure and to obtain an economic effect that the manufacturing cost can be reduced.

  This can be achieved even when the number of lamp driving circuits 51 is not six. In addition, when there are an even number of lamp driving circuits 51, among the applied voltages VL output from each lamp driving circuit 51, there is a combination of two applied voltages VL whose phases are reversed. It can be suitably realized. It is obvious that the inverter device 150 according to the second embodiment of the present invention can obtain the same effects as those of the inverter device 50 according to the first embodiment.

  FIG. 14 is a block diagram for explaining an inverter device 250 according to the third embodiment of the present invention. The inverter device 250 according to the third embodiment is similar to the inverter device 50 according to the first embodiment, and has the same configuration except that the driving lamp L is different. Therefore, a different structure from the inverter apparatus 50 of the 1st form is demonstrated, the same referential mark is attached | subjected about the same structure, and the description is abbreviate | omitted. Inverter device 250 drives a U-shaped tube, not a straight tube lamp. Even in this case, the same effect as that of the inverter device 50 of the first embodiment can be obtained by shifting the phase of the applied voltage VL output from each lamp driving circuit 51.

  In this case, the lamp driving circuit 51 has two output terminals 82 and 83, and generates an AC sine wave potential difference corresponding to the applied voltage VL between the output terminals 82 and 83. The lamp driving circuit 51 and the lamp L are connected by two output lines 86 and 87 that can conduct electricity. Specifically, one output terminal 82 of the lamp driving circuit 51 and one output terminal 76 of the lamp L are electrically connected by the first output line 86. The second output line 87 electrically connects the other output terminal 83 of the lamp drive circuit 51 and the other output terminal 79 of the lamp L. Each lamp driving circuit 51 is electrically connected to a ground line 88 set to a ground potential.

  FIG. 15 is a block diagram for explaining an inverter device 350 according to the fourth embodiment of the present invention. FIG. 16 is an electric circuit showing the lamp driving circuit 351 in the fourth embodiment. The inverter device 350 of the fourth form is similar to the inverter device 50 of the first form except for the configuration of the lamp drive circuit 351. Therefore, a different structure from the inverter apparatus 50 of the 1st form is demonstrated, the same referential mark is attached | subjected about the same structure, and the description is abbreviate | omitted.

  The lamp driving circuit 351 drives two lamps having different applied voltages by 180 degrees. The lamp driving unit 351 outputs a reference applied voltage serving as a reference and an inverted applied voltage whose phase is inverted with respect to the reference applied voltage, and applies the voltage to each lamp. A plurality of lamp driving circuits 351 are provided. Each lamp driving circuit 351 is supplied with a driving signal for shifting the phase of the reference applied voltage by a phase difference corresponding to a period obtained by dividing one cycle T of the applied voltage by the number N of lamps L. Further, each lamp driving circuit 351 shifts the phase of the applied voltage applied to each of the two lamps L adjacent in the parallel direction X by a phase difference corresponding to a period obtained by dividing one cycle T by the number N of lamps. , Connected to each lamp L.

  As in the present embodiment, when there are six lamps L, the first lamp driving circuit 351 supplies the reference application voltage VL1 to the first lamp L1 and the reverse application voltage VL4 to the fourth lamp L4. The second lamp driving circuit 351 applies the reference application voltage VL2 to the second lamp L2, and applies the reverse application voltage VL5 to the fifth lamp L5. Further, the reference application voltage VL3 is applied to the third lamp L3, and the reverse application voltage VL6 is applied to the sixth lamp L6. As a result, the phase difference between the lamps adjacent to each other in the parallel direction X is maintained at 60 degrees.

  The lamp driving circuit 351 includes an AC conversion unit 51a illustrated in FIG. 12 and two voltage conversion units 51b illustrated in FIG. The AC conversion unit 51a drives the two voltage conversion units 51b in parallel, and the connection direction to the AC conversion unit 51a is different between the one voltage conversion unit 51b and the other voltage conversion unit 51b. As a result, the phase of the applied voltage VL output from one voltage converter 51b and the other voltage converter 51b can be inverted. With this configuration, it is possible to reduce the number of AC converters 51a and simplify the configuration of the drive signal generator that supplies a signal to the AC converter 51a. In the fourth embodiment, a capacitor ballast circuit is preferably interposed between the AC converter 51a and the voltage converter 51b. The capacitor ballast circuit is a turbulent P current that balances a lamp current in order to prevent a malfunction due to a negative resistance of the lamp when a plurality of lamps are connected in parallel to the AC converter 51a by a plurality of voltage converters 51b. It is an example of a balanced circuit. The capacitor ballast circuit reduces the lamp current when the lamp resistance decreases.

  FIGS. 15 and 16 show an example in which, when there are six lamps, a sequential phase shift of 60 degrees is realized by three drive signals, three AC converters 51a, and six voltage converters 51b. For example, when there are four lamps, a sequential phase shift of 90 degrees can be realized by two phase shift signals, two AC converters 51a, and four voltage converters 51b. Therefore, when there are N lamps, a sequential phase shift of 360 / N is realized by N / 2 drive signals, N / 2 AC converters 51a, and N voltage converters 51b. Can do.

  FIG. 17 is a block diagram for explaining an inverter device 450 according to the fifth embodiment of the present invention. In the lamp drive circuit 51 of the combination in which the phase difference of the applied voltage output in FIG. 1 is reversed, the same drive signal may be given by changing the connection state between the switching elements Tr2 and Tr3 and the drive signal generator 52. By varying the connection state, the phase of the alternating voltage generated by the first lamp driving circuit 51 and the alternating voltage generated by the second lamp driving circuit can be reversed even when the same drive signal is given. As a result, the number of drive signals generated from the drive signal generator 52 can be reduced.

  FIG. 18 is a block diagram for explaining an inverter device 550 according to the sixth embodiment of the present invention. The inverter device 550 of the sixth embodiment is similar to the inverter device 50 of the first embodiment, and has the same configuration except that the connection state between each lamp driving circuit 51 and the lamp is different. Therefore, a different structure from the inverter apparatus 50 of the 1st form is demonstrated, the same referential mark is attached | subjected about the same structure, and the description is abbreviate | omitted.

  The lamp driving circuit 51 may drive a plurality of lamps L. For example, as shown in FIG. 18, when there are 12 lamps and there are first to sixth amplifier driving means for outputting applied voltages that are sequentially shifted in phase by 60 degrees, the first lamp L1 to the twelfth lamp from one side in the parallel direction X. When referred to as L12, the first lamp driving circuit 51 applies the applied voltage VL1 having the same phase to the first lamp L1 and the seventh lamp L7. The second lamp driving circuit 51 gives the applied voltage VL2 having the same phase to the second lamp L2 and the eighth lamp L8. The third lamp driving circuit 51 applies the applied voltage VL3 having the same phase to the third lamp L3 and the ninth lamp L9. The fourth lamp driving circuit 51 applies an applied voltage having the same phase to the fourth lamp L4 and the tenth lamp L10. The fifth lamp drive circuit 51 gives the applied voltage L5 having the same phase to the fifth lamp L5 and the eleventh lamp L11. The sixth lamp drive circuit 51 applies an applied voltage having the same phase to the sixth lamp L6 and the twelfth lamp L12.

  As a result, the phase difference between the applied voltages applied to two lamps adjacent to each other in the parallel direction X is maintained at 60 degrees, and the total leakage current flowing through each lamp L becomes zero. When generalized, the drive signal generator 52 sets the phase of the applied voltage VL applied to each of the two lamps L adjacent in the parallel direction X to a natural number M to the number N of discharge tubes with respect to one period T in the applied voltage. Each lamp drive circuit 51 is provided with a drive signal that is shifted by a phase difference corresponding to the period T · (M / N) divided by the number N / M divided by. Each lamp driving circuit 51 applies an applied voltage VL having the same phase to M lamps L.

  Thereby, the same effect as that of the inverter device 50 of the first embodiment can be obtained. Further, it is possible to prevent the number of lamp driving circuits 51 from increasing compared to the number N of lamps, and even if the number N of lamps increases, the manufacturing cost of the inverter device 50 can be suppressed. Further, the liquid crystal display device 11 can be thinned. Further, by reducing the number of AC converters 51a and voltage converters 51b, the temperature rise of the liquid crystal display device 11 can be suppressed, damage due to heat generation can be prevented, and reliability can be improved.

  Further, in the sixth embodiment, the drive signal generator 52 is arranged so that the potential difference between the applied voltages applied to the two adjacent lamps L is less than or equal to a predetermined allowable potential difference, and from each lamp L to the adjacent conductor 2. It is preferable to shift the phase of each applied voltage applied to each lamp so that the total value of leaking leakage currents is equal to or less than a predetermined allowable total leakage current value.

  In addition, the lamp driving circuit 51 divides the applied voltage frequency f that can prevent flickering of the lamp L with the phase of the applied voltages in the same phase by the number α of applied voltages having different phases. It is preferable to apply an applied voltage of frequency f / α to each discharge tube. At this time, the number α of applied voltages having different phases is a number N / M obtained by dividing the number N of lamps by the number M of lamps connected to each lamp driving circuit 51. As a result, the flickering of the display image and the luminance deviation can be reduced, and the manufacturing cost can be further reduced.

  Each embodiment of the present invention described above is merely an example of the present invention, and the configuration can be changed within the scope of the invention. For example, in the present embodiment, the number of lamps L is six, but the number is not limited to six. Moreover, the phase difference of each applied voltage should just be shifted | deviated to the unified direction as it goes to the other from one side of a parallel direction, and may be advanced even if it is late.

  Further, for example, the lamp driving circuit 51 does not need to further convert the direct current generated from the direct current converter 6 into an alternating voltage, and may directly generate the applied voltage from the commercial alternating voltage. As a result, it is possible to reduce the power loss by reducing the conversion process necessary for generating the applied voltage.

It is a block diagram for demonstrating the inverter apparatus 50 which is 1st Embodiment of this invention. 2 is a cross-sectional view showing a liquid crystal display device 11. FIG. 3 is a block diagram showing a liquid crystal display device 11 including an inverter device 50. FIG. 3 is a time chart showing drive signals that the drive signal generator 52 gives to the lamp drive circuits 51, respectively. 5 is a time chart showing applied voltages output from each lamp drive circuit 51 when the drive signals shown in FIG. 3 is a graph showing leakage currents leaking from each lamp L. It is a graph which shows the synthetic | combination leakage current which totaled each leakage current. It is a block diagram which shows the case where a proximity | contact conductor is a floating structure. It is a graph which shows the electric potential difference of two adjacent applied voltages. It is a graph which shows the time change of each lamp current of this invention, and the time change of the total brightness which totaled the brightness | luminance of all the lamps. It is a graph which shows the time change of each lamp current of a comparative example, and the time change of the brightness | luminance which totaled the brightness | luminance of all the lamps of the comparative example. 2 is an electric circuit illustrating an example of a lamp driving circuit 51. It is a block diagram for demonstrating the inverter apparatus 150 which is the 2nd Embodiment of this invention. It is a block diagram for demonstrating the inverter apparatus 250 which is 3rd Embodiment of this invention. It is a block diagram for demonstrating the inverter apparatus 350 which is the 4th Embodiment of this invention. It is an electric circuit which shows the lamp drive circuit 351 in a 4th form. It is a block diagram for demonstrating the inverter apparatus 450 which is 5th Embodiment of this invention. It is a block diagram for demonstrating the inverter apparatus 550 which is the 6th Embodiment of this invention. It is a block diagram for demonstrating the inverter apparatus which performs asynchronous drive operation | movement. It is a block diagram for demonstrating the electric potential difference between lamp | ramp.

It is a graph which shows the time change of the potential difference of each application voltage VL1 and VL2 when there exists a phase difference in the application voltages VL1 and VL2 given to two lamps L1 and L2. It is a block diagram for demonstrating the case where the proximity | contact conductor 2 is made into a floating structure in an asynchronous drive state. It is a block diagram for demonstrating the inverter apparatus 3 which performs in-phase drive operation | movement. It is a block diagram for demonstrating the case where the proximity | contact conductor 2 is made into a floating structure in the same phase drive state. It is a block diagram for demonstrating the inverter apparatus which performs a reverse phase synchronous operation | movement. It is a figure for demonstrating distribution of the leakage current with respect to a lamp | ramp.

Explanation of symbols

2 Proximity conductor 11 Liquid crystal display device 12 Liquid crystal display substrate 50, 150, 250, 350, 450, 550 Inverter device 51 Lamp drive circuit 51a AC converter 51b Transformer 52 Drive signal generator L1-L6 Lamps VL1-VL6 Applied voltage

Claims (11)

An inverter device for driving and lighting each of a plurality of liquid crystal display discharge tubes arranged in a predetermined parallel direction,
Driving means for applying an applied voltage to the discharge tube for driving the discharge tube;
The phase of each applied voltage applied to each discharge tube arranged in the parallel direction is sequentially shifted by a phase difference corresponding to a period T / N divided by the number N of discharge tubes with respect to one period T of the applied voltage. An inverter device comprising drive signal generating means for supplying a drive signal to the drive means. An inverter device for driving and lighting each of a plurality of liquid crystal display discharge tubes arranged in a predetermined parallel direction,
Driving means for applying an applied voltage to the discharge tube for driving the discharge tube;
A period T · () obtained by dividing the phase of each applied voltage applied to each discharge tube arranged in the parallel direction by a number N / M obtained by dividing the number N of discharge tubes by a natural number M with respect to one period T of the applied voltage. M / N), and a drive signal generating means for providing the drive means with a drive signal that is sequentially shifted by a phase difference corresponding to M / N).   3. The inverter device according to claim 1, wherein the drive signal generating means sets a phase difference between applied voltages respectively applied to two adjacent discharge tubes to 90 degrees or less.   3. The inverter apparatus according to claim 1, wherein the drive signal generating means sets the phase difference between the applied voltages applied to two adjacent discharge tubes to 60 degrees or less.   The drive signal generating means shifts the phase of each applied voltage applied to each discharge tube so that a potential difference between applied voltages applied to two adjacent discharge tubes is equal to or less than a predetermined allowable potential difference. The inverter apparatus as described in any one of 1-4.   The drive signal generating means is characterized in that the phase of each applied voltage applied to each discharge tube is shifted so that the total value of leakage currents leaking from each discharge tube to the adjacent conductors is equal to or less than a predetermined allowable current value. The inverter apparatus as described in any one of Claims 1-5.   The driving means has a frequency f / divided by the number α of applied voltages having different phases with respect to the frequency f of the applied voltage that can prevent flickering of the discharge tube in a state where the phases of the applied voltages are the same. The inverter device according to claim 1, wherein an applied voltage α is applied to each discharge tube.   The inverter device according to claim 1, wherein the number of applied voltages having different phases is set to an even number.   The inverter device according to claim 1, further comprising a connection unit that electrically connects the low-voltage side electrodes of each discharge tube.   The inverter device according to any one of claims 1 to 9, wherein the discharge tube to be driven is a cold cathode fluorescent lamp. A plurality of liquid crystal display discharge tubes arranged in a predetermined parallel direction;
Driving means for applying an applied voltage to the discharge tube for driving the discharge tube;
The phase of each applied voltage applied to each discharge tube arranged in parallel is divided by the number N of discharge tubes with respect to one period T in the applied voltage, or the natural number M in the number N of discharge tubes. Drive signal generation means for supplying a drive signal to the drive means for shifting by a phase difference corresponding to a period T · (M / N) divided by the divided number N / M and selectively transmitting light lit by the discharge tube A liquid crystal display substrate,
And a control means for controlling the light transmission state of the liquid crystal display substrate.

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