JP2010129238A - Lighting device and lighting fixture using the same as well as liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device and a lighting fixture using the same capable of maintaining brightness of a lamp constant, and alleviating stress of switching elements constituting an inverter circuit, as well as a liquid crystal display. <P>SOLUTION: The lighting device A includes an inverter circuit 3 converting a direct-current power source into high-frequency power to supply to a discharge lamp 4, a drive pulse generating circuit for generating drive pulses determining operation frequency of the switching elements constituting the inverter circuit 3, a voltage control circuit 7 outputting feedback signals Cv1 in accordance with a lamp voltage Vla impressed on the discharge lamp 4, a power control circuit 8 outputting feedback signals Cc1 in accordance with a lamp current Ila supplied to the discharge lamp 4, a selective circuit 6 selecting either the voltage control circuit 7 or the power control circuit 8, and a switching circuit 5 switching the selective circuit 6 in accordance with comparison results of voltage signals fv proportional to the operation frequency of the inverter circuit 3 with a reference value fp1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lighting device, a lighting fixture using the same, and a liquid crystal display device.

  Conventionally provided liquid crystal display devices are composed of a liquid crystal panel and a backlight disposed on the back of the liquid crystal panel. In each pixel constituting the liquid crystal panel, a liquid crystal element is provided according to a video signal. When driven, the light emitted from the backlight is transmitted. Conversely, when the liquid crystal element is not driven, the light emitted from the backlight is shielded, and as a result, an image is displayed on the liquid crystal panel. Yes.

  Here, for example, a cold cathode fluorescent lamp (CCFL) or a hot cathode fluorescent lamp (HCFL) is used as the backlight of the liquid crystal display device. However, these fluorescent lamps require a lighting device for lighting the lamp. In particular, when used as a backlight of a liquid crystal display device, it is very important to keep the brightness of the lamp constant.

  Therefore, a backlight inverter employing a feedback circuit has been proposed in order to keep the brightness of the lamp constant (see, for example, Patent Document 1). The backlight inverter feeds back a detection voltage corresponding to the lamp current, feeds back a detection voltage corresponding to the lamp voltage, and a first error amplification circuit that outputs an error voltage by comparing the detection voltage with a reference voltage. And a second error amplification circuit that outputs an error voltage by comparing the detected voltage with a reference voltage, and either the first or second error amplification circuit is selected according to the operation of the selection circuit. When the lamp is released or excessive voltage is applied to the lamp, the applied voltage is limited to the open voltage until the lamp current is completely cut off to prevent the lamp from being damaged or shortening its life. It has come to be.

  In addition, when the voltage applied to the lamp is generated via the resonance circuit, it is desirable to change the frequency continuously. However, at this time, the lamp may not start unless the lamp voltage at the start is appropriate. . Therefore, a lighting device has also been proposed that adjusts the lamp voltage at the start to an appropriate value while continuously varying the frequency (see, for example, Patent Document 2).

This lighting device is a device in which the startability of the lamp is improved by suppressing the lamp start voltage that rises with variations in the elements constituting the resonance circuit. In the resonance type inverter circuit including such a lamp, When the lamp is not lit, the Q value of the resonance circuit is high, and the lamp voltage changes according to the frequency difference from the resonance frequency. However, if the resonance frequency shifts due to variations in the elements, the starting voltage The lamp may not start, especially when the starting voltage increases. Therefore, in this lighting device, when the inverter circuit is started up, the voltage across the capacitor constituting the resonance circuit is monitored to detect the operating frequency (resonance frequency) at which the voltage across the capacitor is maximized when the lamp is not lit. Then, by continuously shifting the operating frequency of the resonance circuit to the resonance frequency, the starting voltage is controlled to a predetermined value, and the lamp is stably lit.
JP 2008-3601 A (paragraph [0016] -paragraph [0039] and FIG. 2) Japanese Patent Laying-Open No. 2005-63862 (paragraph [0009] -paragraph [0043] and FIG. 1)

  In the backlight inverter disclosed in Patent Document 1 described above, for example, when the first error amplifier circuit is switched to the second error amplifier circuit, the input terminal of the first error amplifier circuit is connected to the ground so that the reference voltage is As the difference increases, the error voltage increases, and the second error amplifier circuit operates to suppress the ramp voltage, so that the error voltage decreases. That is, according to this example, each error amplifier circuit performs the reverse operation at the time of circuit switching, so that there is a possibility that it does not function properly depending on the constant of the feedback circuit. For example, the gain of the second error amplifier circuit is the first error. If the gain is smaller than the gain of the amplifier circuit, or the second error amplifier circuit is less responsive than the first error amplifier circuit, the lamp voltage may not be immediately limited. In a resonance type inverter circuit, if the operating frequency of the inverter circuit is a control amount of feedback control, excessive stress may be applied to the switching elements constituting the inverter circuit when discontinuous control occurs. It was.

  Further, in the lighting device shown in Patent Document 2, since the resonance frequency can be detected from the voltage across the capacitor, the starting voltage can be controlled by the frequency, but the starting voltage can be controlled by other factors. For example, when a power supply fluctuation occurs in the inverter circuit, a response cannot be made, so that the lamp voltage fluctuates with the power supply fluctuation. In such a case, there is no problem even if the starting state fluctuates somewhat in a general lighting fixture, but in the liquid crystal display device, the starting timing is very important, and there is a possibility that the image is uneven.

  The present invention has been made in view of the above problems, and its object is to maintain the brightness of the lamp constant and to reduce the stress of the switching elements constituting the inverter circuit. An object of the present invention is to provide a lighting device, a lighting fixture using the same, and a liquid crystal display device.

  The invention according to claim 1 is an inverter circuit that converts a DC power source into high-frequency power and supplies it to a light source, a drive pulse generation circuit that generates a drive pulse that determines an operating frequency of a switching element that constitutes the inverter circuit, A plurality of output signals that detect the separate electrical physical quantities related to the lighting state of the motor and that change the frequency of the drive pulse output from the drive pulse generation circuit so that the detected physical quantity becomes a predetermined target value. A feedback control circuit, a selection circuit that selects any one of the plurality of feedback control circuits and outputs a feedback signal to the drive pulse generation circuit, and a comparison result between the operating frequency of the inverter circuit and the reference value And a switching circuit for switching the selection circuit accordingly.

  According to a second aspect of the present invention, a low-pass filter is provided between the output terminal of the selection circuit and the input terminal of the drive pulse generation circuit.

  The invention according to claim 3 is characterized in that the switching circuit changes the target value of the newly selected feedback control circuit in accordance with the switching timing of the selection circuit.

  According to a fourth aspect of the present invention, the light source is a discharge lamp, and a voltage control circuit that outputs a feedback signal according to a voltage applied to the light source, and a power or current supplied to the light source. And a power control circuit that outputs a feedback signal as a plurality of feedback control circuits, and the switching circuit switches the switching signal to be switched to the voltage control circuit when the detection result of the detection means is equal to or greater than a predetermined reference value. When the detection result is lower than a predetermined reference value, a switching signal for switching to the power control circuit is output to the selection circuit.

  According to a fifth aspect of the present invention, the light source is a hot cathode discharge lamp, and a voltage control circuit that outputs a feedback signal according to a tube voltage of the discharge lamp, and a tube power or a tube current of the discharge lamp. A plurality of feedbacks including a power control circuit that outputs a feedback signal according to the current and a preheating control circuit that outputs a feedback signal according to either the current flowing through the filament electrode of the discharge lamp or the voltage applied to the filament electrode. The switching circuit is provided as a control circuit, and outputs a switching signal for switching to the preheating control circuit to the selection circuit when the detection result of the detection means is equal to or higher than the first reference value, and the detection result is lower than the first reference value. When the value is lower than the second reference value, a switching signal for switching to the voltage control circuit is output to the selection circuit, and the detection result is greater than the second reference value. And outputs to the selection circuit a switching signal for switching to the power control circuit if it is lower.

  The invention of claim 6 includes a dimming circuit that outputs a dimming signal for determining an output value of the light source, and the switching circuit changes the reference value according to the dimming signal.

  The invention of claim 7 includes the lighting device according to any one of claims 1 to 6.

  The invention of claim 8 is characterized by comprising the lighting device according to any one of claims 1 to 6.

  According to the first aspect of the present invention, the brightness of the light source can be kept constant by feeding back the electrical physical quantity related to the light source, and feedback is performed according to the comparison result between the operating frequency of the inverter circuit and the reference value. Since continuous control is possible by switching the control circuit, there is an effect that stress applied to the switching elements constituting the inverter circuit can be reduced.

  According to the second aspect of the present invention, since the low-pass filter is provided between the output terminal of the selection circuit and the input terminal of the drive pulse generation circuit, a signal having a predetermined frequency or more is attenuated. As a result, it is possible to alleviate a steep change in the control signal in the circuit, and as a result, it is possible to prevent malfunction of the drive pulse generation circuit.

  According to the invention of claim 3, by changing the target value of the feedback control circuit to be newly selected in accordance with the switching timing of the selection circuit, the response delay that occurs when switching the feedback control circuit is suppressed, As a result, it is possible to prevent the circuit and the light source from being stressed due to overshoot.

  According to the invention of claim 4, the design freedom can be increased by making it possible to set the target values of the voltage control circuit and the power control circuit separately, and each lamp starts the target value of each control circuit. By setting the value to a possible value, the lamp can be reliably turned on, so that there is an effect that a special means for detecting lighting is not required.

  According to the invention of claim 5, since the lamp is started after the filament temperature is controlled to a constant temperature by the preheating control circuit, the filament temperature becomes too high, so that electrons are excessively emitted and the lamp life is shortened. When the length is shortened or the filament temperature is too low, it is possible to prevent the discharge amount from being insufficient and the discharge tube from being damaged by ion bombardment.

  According to the invention of claim 6, there is an effect that the dimming range can be expanded by changing the reference value of the operating frequency of the inverter circuit according to the dimming signal from the dimming circuit.

  According to the invention of claim 7, by using the lighting device according to any one of claims 1 to 6, there is an effect that it is possible to provide a lighting fixture capable of keeping the illuminance level constant. .

  According to the invention of claim 8, by using the lighting device according to any one of claims 1 to 6, there is provided a liquid crystal display device capable of keeping the brightness of a light source used as a backlight constant. There is an effect that can be done.

  DESCRIPTION OF EMBODIMENTS Embodiments of a lighting device according to the present invention, a lighting fixture using the same, and a liquid crystal display device will be described below with reference to the drawings. The lighting device according to the present invention is used for lighting a light source of a lighting fixture or a backlight of a liquid crystal display device, for example.

(Embodiment 1)
FIG. 1 is a schematic circuit diagram illustrating a lighting device A according to the first embodiment. The lighting device A includes a rectifier 1 that full-wave rectifies AC power from a commercial power supply AC, a switching element, an inductor, a diode, and the like. A conventionally known boost chopper circuit 2 that boosts and smoothes the output DC voltage, and an inverter circuit 3 that converts the DC power supplied from the boost chopper circuit 2 into high-frequency power and supplies it to a discharge lamp (light source) 4. A voltage control circuit 7 for detecting a lamp voltage Vla applied to the discharge lamp 4 and outputting a feedback signal Cv1 for changing the operating frequency of the inverter circuit 3 so that the detected lamp voltage Vla becomes a target value A1, and a discharge An inverter circuit that detects a lamp current Ila supplied to the lamp 4 and sets the detected lamp current Ila to a target value A2. The power control circuit 8 that outputs the feedback signal Cc1 that changes the operating frequency of the power supply circuit 8 and either the voltage control circuit 7 or the power control circuit 8 are selected, and the feedback signal Cv1 (or the feedback signal Cc1) is sent to the inverter circuit 3 A voltage signal fv proportional to the operating frequency is input from the selection circuit 6 that outputs to the inverter circuit 3 and switching for switching the output of the selection circuit 6 according to the result of comparing the level of the voltage signal fv with the reference value fp1 Circuit 5. In the present embodiment, a low-pass filter that attenuates the high-frequency component of the feedback signal Cv1 (or feedback signal Cc1) output from the selection circuit 6 between the output terminal of the selection circuit 6 and the input terminal of the inverter circuit 3. 9 is provided. Here, in this embodiment, the voltage control circuit 7 and the power control circuit 8 constitute a feedback control circuit, and the lamp voltage Vla and the lamp current Ila are detected as electrical physical quantities related to the lighting state of the light source. .

  The inverter circuit 3 has a resonance circuit (not shown), and the output voltage and the output impedance change according to the operating frequency. That is, the power supplied to the discharge lamp 4 can be controlled by changing the operating frequency. In the present embodiment, the switching cycle of the switching elements constituting the inverter circuit 3 becomes the operating frequency of the inverter circuit 3, but a driving pulse generating circuit (not shown) for generating a driving pulse for determining the operating frequency. ) Is built in the inverter circuit 3.

  The switching circuit 5 includes a voltage signal fv input from an FV converter (not shown) that outputs a voltage signal fv proportional to the operating frequency of the inverter circuit 3, and a reference value corresponding to the reference value of the operating frequency. The switching signal Cs1 is output to the selection circuit 6 according to the comparison result with fp1. In this embodiment, the voltage signal fv proportional to the operating frequency is input from the FV converter to the switching circuit 5. For example, a signal corresponding to the operating frequency is output from the drive pulse generating circuit included in the inverter circuit 3. You may enter.

  The selection circuit 6 is, for example, a circuit that selects one of two input signals as an output signal. As shown in FIG. 1, the output terminal of the voltage control circuit 7 is connected to one input terminal A, and The output terminal of the power control circuit 8 is connected to the other input terminal B. FIG. 3 shows an example of the selection circuit 6, which includes transistors Q1 and Q2 that are turned on / off in response to a switching signal Cs1 from the switching circuit 5 input to a select terminal (SELECT in FIG. 3). When the switching signal Cs1 input to the select terminal is Low, the transistor Q1 is turned on and the input terminal B is short-circuited to the ground. Therefore, feedback from the power control circuit 8 input to the input terminal B is performed. The signal Cc1 is not output to the output terminal (OUTPUT in FIG. 3). On the other hand, since the transistor Q2 is off, the feedback signal Cv1 from the voltage control circuit 7 input to the input terminal A is output to the output terminal via the resistor Rc2 and the diode D2. That is, in this case, the voltage control circuit 7 is selected as the feedback control circuit.

  Conversely, when the switching signal Cs1 input to the select terminal is High, the transistor Q2 is turned on and the transistor Q1 is turned off, so that the feedback signal Cc1 from the power control circuit 8 input to the input terminal B is The signal is output to the output terminal via the resistor Rc1 and the diode D1. That is, in this case, the power control circuit 8 is selected as the feedback control circuit. The feedback signals Cv1 and Cc1 are both set to increase the operating frequency of the inverter circuit 3 as the lamp voltage Vla is higher.

  Here, the low-pass filter 9 is composed of, for example, an RC circuit, and can attenuate a high-frequency component of the feedback signal Cv1 (or feedback signal Cc1) generated when the selection circuit 6 is switched. Can be prevented.

  Here, in the present embodiment, when the operating frequency of the inverter circuit 3, that is, the voltage signal fv input to the switching circuit 5 is equal to or higher than the reference value fp1, the switching is performed so that the voltage control circuit 7 is selected. When the signal Cs1 is set to Low and the voltage signal fv is smaller than the reference value fp1, the switching signal Cs1 is set to High so that the power control circuit 8 is selected. In order to prevent chattering at the time of switching, it is desirable that the reference value fp1 has a hysteresis characteristic.

  Next, operation | movement of the lighting device A of this embodiment is demonstrated. FIG. 2 is a time chart for explaining the operation of each circuit described above. In the initial stage before time t1, the discharge lamp 4 is turned off, and at this time, the voltage control circuit 7 is selected as the feedback control circuit. Yes. That is, the switching circuit 5 outputs a Low switching signal Cs1.

  When the target value A1 of the voltage control circuit 7 (the voltage value for starting the discharge lamp 4 in this example) is set at the time t1, the voltage control circuit 7 causes the detected lamp voltage Vla to become the target value A1. A feedback signal Cv1 for lowering the operating frequency of the inverter circuit 3 is output to generate a high voltage for starting the discharge lamp 4. In addition, since the inverter circuit 3 of this embodiment is provided with the resonance circuit, a high output voltage can be obtained by bringing the operating frequency of the inverter circuit 3 close to the resonance frequency.

  When the discharge lamp 4 is started from a state in which the lamp voltage Vla is controlled to be constant, a lamp current Ila is generated in the discharge lamp 4, but the lamp voltage Vla decreases accordingly. Then, the voltage control circuit 7 attempts to increase the lamp voltage Vla by further reducing the operating frequency of the inverter circuit 3 in response to the decrease of the lamp voltage Vla. However, since the discharge lamp 4 has already started, the lamp voltage Vla never reaches the target value A1, and the feedback signal Cv1 of the voltage control circuit 7 is saturated at a predetermined lower limit value.

  On the other hand, the feedback signal Cc1 of the power control circuit 8 is saturated at a predetermined lower limit so that the lamp current Ila increases until the discharge lamp 4 is started, and the discharge lamp 4 is started and the lamp current Ila is generated. Then, the power control circuit 8 changes the feedback signal Cc1 in a direction to decrease the output of the inverter circuit 3.

  Next, when the voltage signal fv becomes smaller than the reference value fp1 at time t2 (that is, when the operating frequency becomes smaller than the reference frequency), the switching circuit 5 outputs the High switching signal Cs1, and the feedback control circuit. As a result, the power control circuit 8 is selected. That is, after time t2, feedback control is performed by the lamp current Ila supplied to the discharge lamp 4. At time t3, the response of the power control circuit 8 is completed and the lamp current Ila becomes stable. The time t2 to t3 is the switching timing from the voltage control circuit 7 to the power control circuit 8. The high-frequency component of the feedback signal generated at this time is attenuated by the low-pass filter 9 described above. Further, when the selection circuit 6 is configured using the transistors Q1 and Q2 as in the present embodiment, it is possible to smoothly perform input switching by using the active regions of the transistors Q1 and Q2.

  Thus, according to the present embodiment, the brightness of the discharge lamp 4 can be kept constant by feeding back the lamp voltage Vla or the lamp current Ila of the discharge lamp 4, and the operating frequency and reference of the inverter circuit 3 can be maintained. Since continuous control becomes possible by switching the feedback control circuit (the voltage control circuit 7 and the power control circuit 8) according to the comparison result with the value, the stress applied to the switching elements constituting the inverter circuit 3 can be reduced. . In addition, as in this embodiment, by making it possible to set the target values of the voltage control circuit 7 and the power control circuit 8 separately, the degree of design freedom can be increased, and the target values of each control circuit can be discharged. Since the discharge lamp 4 can be reliably turned on by setting the lamp 4 to a startable value, there is also an advantage that no special means for detecting lighting is required.

  In the present embodiment, the lamp current Ila flowing through the discharge lamp 4 is a control target of the power control circuit 8, but for example, a power value calculated from the lamp voltage Vla and the lamp current Ila may be the control target. In this embodiment, the selection circuit 6 is composed of the transistors Q1 and Q2. However, for example, an analog switch or the like may be used.

(Embodiment 2)
Embodiment 2 of the lighting device A according to the present invention will be described with reference to FIGS. 4 and 5. In the present embodiment, the switching circuit 5 changes the target value A2 of the newly selected feedback control circuit (the power control circuit 8 in the present embodiment) in accordance with the timing at which the switching signal Cs1 is output to the selection circuit 6. It is configured as follows. Since other configurations are the same as those in the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 4, the lighting device A of the present embodiment includes a rectifier 1, a boost chopper circuit 2, an inverter circuit 3, a switching circuit 5, a selection circuit 6, a voltage control circuit 7, and a power control circuit 8. And a low-pass filter 9.

  The switching circuit 5 outputs the switching signal Cs1 to the selection circuit 6 according to the comparison result between the voltage signal fv proportional to the operating frequency of the inverter circuit 3 and the reference value fp1, and the newly selected power control circuit 8 The target value A2 is changed.

  Next, operation | movement of the lighting device A of this embodiment is demonstrated based on FIG. Since the operation before time t2 is the same as that of the first embodiment, the description thereof is omitted here. When the voltage signal fv falls below the reference value fp1 at time t2 (that is, when the operating frequency falls below the reference frequency), the switching circuit 5 outputs a switching signal Cs1 for switching to the power control circuit 8 to the selection circuit 6. At the same time, the target value A2 of the power control circuit 8 is changed to a current value at which the discharge lamp 4 starts. Then, in the power control circuit 8, feedback control is executed so that the lamp current Ila of the discharge lamp 4 becomes the target value A2.

  Here, since the switching signal Cs1 output from the switching circuit 5 is Low before time t2, the voltage control circuit 7 is selected as the feedback control circuit. At this time, the target value A2 of the power control circuit 8 is the discharge lamp. 4 is set lower than the starting current value (see FIG. 5). Thus, by setting the target value A2 of the power control circuit 8 to be low in the initial stage, the feedback signal Cc1 of the power control circuit 8 is not saturated at the lower limit corresponding to the frequency lower limit, and the reference frequency at which feedback control is switched. An initial value corresponding to a frequency close to (a frequency corresponding to the reference value fp1) can be output.

  Thus, according to this embodiment, the voltage control circuit 7 changes to the power control circuit 8 by changing the target value A2 of the newly selected power control circuit 8 in accordance with the switching timing of the selection circuit 6. The response delay occurring at the time of switching is suppressed, and as a result, it is possible to prevent stress from being applied to each circuit and the discharge lamp 4 constituting the lighting device A due to overshoot or the like.

(Embodiment 3)
Embodiment 3 of the lighting device A according to the present invention will be described with reference to FIGS. 6 and 7. In the first and second embodiments, two circuits of the voltage control circuit 7 and the power control circuit 8 are used as the feedback control circuit. However, in this embodiment, preheating for supplying preheating power to the filament electrode included in the discharge lamp 4 is further used. The preheating control circuit 10 that outputs a feedback signal Cc2 according to the preheating current Ihc flowing through the circuit 11 is used, and the target value A3 of the preheating control circuit 10 is set by the timer circuit 12. In the following description, the same components as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted.

  The discharge lamp 4 used in the present embodiment is a hot cathode type discharge lamp, and the lighting device A according to the present invention includes a rectifier 1, a boost chopper circuit 2, an inverter circuit 3, as shown in FIG. Voltage that outputs the feedback signal Cv1 that detects the tube voltage Vla of the switching circuit 5, the selection circuit 6, and the discharge lamp 4 and changes the operating frequency of the inverter circuit 3 so that the detected tube voltage Vla becomes the target value A1. A control circuit 7; a power control circuit 8 that detects a tube current Ila of the discharge lamp 4; and outputs a feedback signal Cc1 that changes the operating frequency of the inverter circuit 3 so that the detected tube current Ila becomes a target value A2. A preheating circuit 11 for supplying preheating power to the filament electrode of the discharge lamp 4 and a preheating current Ihc flowing through the preheating circuit 11 are detected, and the detected preheating current Ihc is detected. Preheating control circuit 10 for outputting a feedback signal Cc2 changing the operating frequency of the inverter circuit 3 so that the target value A3, and a timer circuit 12 for setting a target value A3 of the preheating control circuit 10. In the present embodiment, one of the voltage control circuit 7, the power control circuit 8, and the preheating control circuit 10 is selected according to the switching signal Cs1 from the switching circuit 5, and the above A feedback control circuit is constituted by three control circuits.

  In this embodiment, two reference values fp1, fp2 (fp2> fp1) are set as frequency reference values when the switching circuit 5 switches the feedback control circuit, and the switching circuit 5 corresponds to the frequency. When the voltage signal fv of the magnitude is equal to or higher than the reference value fp2 (that is, the operating frequency is equal to or higher than the first reference frequency), the switching signal Cs1 for switching to the preheating control circuit 10 is output. When the reference value fp2 is smaller (that is, the operating frequency is lower than the first reference frequency and equal to or higher than the second reference frequency), the switching signal Cs1 for switching to the voltage control circuit 7 is output, and the voltage signal fv is lower than the reference value fp1. When the frequency is small (that is, when the operating frequency is lower than the second reference frequency), the switching signal Cs1 for switching to the power control circuit 8 is output. To have. The target value A3 of the preheating control circuit 10 is set by a setting signal output from the timer circuit 12 after the time set by the timer circuit 12 has elapsed. Here, in the present embodiment, the reference value fp2 is the first reference value, and the reference value fp1 is the second reference value.

  Next, operation | movement of the lighting device A of this embodiment is demonstrated based on FIG. The lighting device A is for lighting the hot cathode type discharge lamp 4, and starts the discharge lamp 4 from a state in which the temperature of the filament electrode is controlled to be constant. Therefore, in the initial stage, the preheating control circuit 10 is selected as the feedback control circuit. In addition, before the time t1, the discharge lamp 4 is extinguished.

  When the lighting device A is activated at time t0, the preheating control circuit 10 controls the operating frequency of the inverter circuit 3 so that the preheating current Ihc flowing through the preheating circuit 11 becomes a predetermined target value A3. Eventually, when the temperature of the filament electrode rises sufficiently and thermoelectrons are generated, the target value A3 of the preheating control circuit 10 is set low by the timer circuit 12 at time t1, and as a result, the operating frequency of the inverter circuit 3 Decreases.

  After that, when the voltage signal fv becomes smaller than the reference value fp2 at time t2 (that is, when the operating frequency becomes lower than the first reference frequency), the switching circuit 5 selects the switching signal Cs1 for switching to the voltage control circuit 7. The feedback control circuit is switched to the voltage control circuit 7. That is, after time t2, feedback control is executed based on the tube voltage Vla.

  Further, when the voltage signal fv becomes smaller than the reference value fp1 at time t3 (that is, when the operating frequency becomes lower than the second reference frequency), the switching circuit 5 selects the switching signal Cs1 for switching to the power control circuit 8 as the selection circuit 6 And the feedback control circuit is switched to the power control circuit 8. That is, after time t3, feedback control is executed based on the lamp current Ila.

  Thus, according to this embodiment, since the discharge lamp 4 is started after the filament temperature is controlled to a constant temperature by the preheating control circuit 10, electrons are excessively emitted due to the filament temperature becoming too high. As a result, the lamp life of the discharge lamp 4 is shortened or the filament temperature is too low, so that it is possible to prevent the discharge tube from being damaged by ion bombardment due to insufficient electron emission.

  In the present embodiment, the control target of the preheating control circuit 10 is the preheating current Ihc flowing through the preheating circuit 11, but for example, the voltage applied to the preheating circuit 11 may be the control target.

(Embodiment 4)
Embodiment 4 of the lighting device A according to the present invention will be described with reference to FIGS. 8 and 9. Since the lighting device A of the present embodiment includes a dimming circuit 13 for dimming the discharge lamp 4 and the other configuration is the same as that of the second embodiment, the same components are denoted by the same reference numerals. The description is omitted.

  As shown in FIG. 8, the lighting device A of the present embodiment includes a rectifier 1, a boost chopper circuit 2, an inverter circuit 3, a switching circuit 5, a selection circuit 6, a voltage control circuit 7, and a power control circuit 8. And a dimming circuit 13 for dimming the discharge lamp 4, and a dimming signal DIM in which High / Low is repeated at a predetermined cycle is output from the dimming circuit 13 to the switching circuit 5. (See FIG. 9). Here, the drive pulse generation circuit of the inverter circuit 3 performs dimming control according to the dimming signal DIM from the dimming circuit 13, and the discharge lamp 4 is turned on during the period when the dimming signal DIM is High. The discharge lamp 4 is turned off while the dimming signal DIM is Low. In the present embodiment, the discharge lamp 4 is dimmed and turned on by repeating the lighting / extinguishing of the discharge lamp 4 in a predetermined cycle in accordance with the dimming signal DIM. The dimming signal DIM is also input to the switching circuit 5. In the switching circuit 5, the switching signal Cs1 is set to an initial value (a signal at start-up) at the timing when the dimming signal DIM becomes Low. It is supposed to reset to.

  Next, the operation of the lighting device A of the present embodiment will be described with reference to FIG. 9, but the operation up to time t3 is the same as that of the above-described second embodiment, and thus the description thereof is omitted here.

  When a dimming signal DIM (that is, a Low signal) for turning off the discharge lamp 4 is output from the dimming circuit 13 at time t3, the switching signal Cs1 is an initial value (in this embodiment, a voltage control circuit) in the switching circuit 5. (Low signal to be switched to 7). Then, the operating frequency of the inverter circuit 3 rises, and the lighting device A returns to the initial start state. Thereafter, when the dimming signal DIM (that is, the High signal) for lighting the discharge lamp 4 is output from the dimming circuit 13 at time t4, the discharge lamp 4 is lit through the processing from time t1 to t3. In the lighting device A of the present embodiment, burst (intermittent oscillation) dimming lighting can be realized by repeating the above operation.

(Embodiment 5)
Embodiment 5 of the lighting device A according to the present invention will be described with reference to FIGS. 10 and 11. Since the lighting device A of the present embodiment includes a dimming circuit 13 for dimming the discharge lamp 4 and the other configuration is the same as that of the second embodiment, the same components are denoted by the same reference numerals. The description is omitted.

  As shown in FIG. 10, the lighting device A of the present embodiment includes a rectifier 1, a boost chopper circuit 2, an inverter circuit 3, a switching circuit 5, a selection circuit 6, a voltage control circuit 7, and a power control circuit 8. And a dimming circuit 13 for dimming the discharge lamp 4, and the reference value fp1 of the switching circuit 5 is changed according to the dimming signal DIM output from the dimming circuit 13, The target value A2 of the power control circuit 8 is changed.

  Next, operation | movement of the lighting device A of this embodiment is demonstrated based on FIG. Since the operation up to time t1 is the same as that of the first embodiment, the description thereof is omitted here.

  When the time t1 is exceeded, the voltage signal fv proportional to the operating frequency of the inverter circuit 3 falls below the reference value fp1, and the power control circuit 8 is selected as the feedback control circuit. When the dimming signal DIM for reducing the lamp power is output from the dimming circuit 13 at time t2, the operating frequency of the inverter circuit 3 is increased so that the output value is decreased (that is, the voltage signal fv is increased). A dimming operation is performed. At this time, the target value A2 of the power control circuit 8 is set low and the reference value fp1 of the switching circuit 5 is set high, so that the voltage signal fv corresponding to the operating frequency is between the reference value fp1. The width will be expanded.

  Thus, according to the present embodiment, by setting the reference value fp1 of the operating frequency of the inverter circuit 3 to be high according to the dimming signal DIM from the dimming circuit 13, the voltage signal fv and the reference value fp1 are set. As a result, the dimming range of the discharge lamp 4 can be expanded.

(Embodiment 6)
Embodiment of the lighting fixture B using the lighting device which concerns on this invention is described based on FIG. The lighting fixture B of the present embodiment is, for example, a ceiling-mounted lighting fixture, and is formed into a cylindrical shape having a substantially trapezoidal cross-sectional shape with any of the lighting devices described in the first to fifth embodiments. A fixture main body 14 in which the lighting device is housed, and a set of two lamp sockets 15 and 15 which are fixed to both longitudinal ends of the fixture main body 14 and in which a straight tube type discharge lamp 4 is detachably mounted. The high-frequency power output from the lighting device is supplied to the discharge lamp 4 via the lamp sockets 15 and 15.

  Thus, according to the present embodiment, it is possible to provide the lighting fixture B that can keep the illuminance level constant by using any of the lighting devices described in the first to fifth embodiments.

  Note that the lighting fixture B is not limited to a ceiling-mounted type, and may be a ceiling-embedded type, a hanging type, or an annular discharge lamp.

(Embodiment 7)
An embodiment of a liquid crystal display device C using the lighting device according to the present invention will be described with reference to FIG. The liquid crystal display device C of the present embodiment is, for example, a liquid crystal television, and includes a liquid crystal screen unit 101 and a backlight unit 102.

  The liquid crystal screen unit 101 includes a color filter substrate, a liquid crystal, a TFT substrate, a drive module, and the like, and forms a color image based on an image signal from the outside. On the other hand, the backlight unit 102 includes any one of the lighting devices A described in the first to fifth embodiments and a plurality (16 in the present embodiment) of the discharge lamps 4. When the discharge lamp 4 is turned on by the high frequency power output from the lighting device A, a color image corresponding to an image signal from the outside is displayed on the liquid crystal screen.

  Thus, according to the present embodiment, the liquid crystal display that can keep the brightness of the discharge lamp 4 used as a backlight constant by using any one of the lighting devices A described in the first to fifth embodiments. Apparatus C can be provided.

FIG. 3 is a schematic circuit diagram illustrating the lighting device according to the first embodiment. It is a time chart explaining operation | movement of each circuit which comprises the same as the above. It is a circuit diagram of the selection circuit which comprises the same as the above. FIG. 6 is a schematic circuit diagram illustrating a lighting device according to a second embodiment. It is a time chart explaining operation | movement of each circuit which comprises the same as the above. FIG. 6 is a schematic circuit diagram illustrating a lighting device according to a third embodiment. It is a time chart explaining operation | movement of each circuit which comprises the same as the above. FIG. 6 is a schematic circuit diagram illustrating a lighting device according to a fourth embodiment. It is a time chart explaining operation | movement of each circuit which comprises the same as the above. FIG. 10 is a schematic circuit diagram illustrating a lighting device according to a fifth embodiment. It is a time chart explaining operation | movement of each circuit which comprises the same as the above. It is a perspective view of the lighting fixture using any lighting device of Embodiments 1-5. It is a perspective view which can partly break the liquid crystal display device using the lighting device in any one of Embodiments 1-5.

Explanation of symbols

3 Inverter circuit 4 Discharge lamp (light source)
5 switching circuit 6 selection circuit 7 voltage control circuit (feedback control circuit)
8 Power control circuit (feedback control circuit)
A lighting device A1, A2 target value Cv1, Cc1 feedback signal Ila lamp current (electrical physical quantity)
Vla lamp voltage (electrical physical quantity)
fp1 Reference value fv Voltage signal

Claims (8)

  An inverter circuit that converts DC power into high-frequency power and supplies it to the light source, a drive pulse generation circuit that generates a drive pulse that determines the operating frequency of the switching element that constitutes the inverter circuit, and a separate light source related to the lighting state of the light source A plurality of feedback control circuits for detecting a respective electrical physical quantity and outputting a feedback signal for changing the frequency of the drive pulse output from the drive pulse generation circuit so that the detected physical quantity becomes a predetermined target value; A selection circuit that selects any one of the plurality of feedback control circuits and outputs the feedback signal to the drive pulse generation circuit, and a comparison result between an operating frequency of the inverter circuit and a reference value. A lighting device comprising: a switching circuit that switches a selection circuit.   The lighting device according to claim 1, further comprising a low-pass filter between an output terminal of the selection circuit and an input terminal of the drive pulse generation circuit.   The lighting device according to claim 1, wherein the switching circuit changes a target value of a newly selected feedback control circuit in accordance with a switching timing of the selection circuit.   The light source is a discharge lamp, a voltage control circuit that outputs the feedback signal according to a voltage applied to the light source, and the feedback signal according to any one of power or current supplied to the light source. A plurality of feedback control circuits, and the switching circuit selects the switching signal for switching to the voltage control circuit when the detection result of the detection means is equal to or greater than a predetermined reference value. The output to the circuit, and when the detection result is lower than a predetermined reference value, a switching signal for switching to the power control circuit is output to the selection circuit. The lighting device described.   The light source is a hot cathode discharge lamp, a voltage control circuit that outputs the feedback signal according to a tube voltage of the discharge lamp, and the feedback according to any one of tube power or tube current of the discharge lamp. A power control circuit that outputs a signal, and a preheating control circuit that outputs the feedback signal in accordance with either a current flowing through a filament electrode of the discharge lamp or a voltage applied to the filament electrode. Provided as a control circuit, and the switching circuit outputs a switching signal for switching to the preheating control circuit to the selection circuit when the detection result of the detection means is equal to or greater than a first reference value, and the detection result is the first When the reference signal is lower than the first reference value and greater than or equal to the second reference value, the switching signal for switching to the voltage control circuit is selected. 4. The switch circuit according to claim 1, wherein a switching signal for switching to the power control circuit is output to the selection circuit when the detection result is lower than the second reference value. The lighting device according to item.   The light control circuit which outputs the light control signal which determines the output value of a light source is provided, The said switching circuit changes the said reference value according to the said light control signal, The any one of Claims 1-5 characterized by the above-mentioned. The lighting device according to item 1.   A lighting fixture comprising the lighting device according to any one of claims 1 to 6.   A liquid crystal display device comprising the lighting device according to claim 1.

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