JP2010033859A - Discharge lamp lighting circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect smoothed voltages at both potential sides with a simple circuit configuration to obtain detection voltages at both potential sides and a difference voltage between both the detected smoothed voltages through computational processing for more accurate determination of lifetime end stage. <P>SOLUTION: The voltages across a discharge lamp FL are rectified to the positive and negative potentials using diodes D11 and D12. The positive potential-side rectified voltage is smoothed by a capacitor C12, and is divided by voltage divider resistors R14 and R15 to be output to an output terminal P01, while the negative potential-side rectified voltage is smoothed by a capacitor C14, and the resulting smoothed voltage is placed into a positive pole state through voltage division using voltage divider resistors R16-R18 between the smoothed voltage and the positive supply voltage ei to be output to an output terminal P02. A microcomputer 12 converts the voltage input from the output terminal P02 to correspond to a variation range of the detection voltage for the voltage from the output terminal P01. The voltage on the output terminal P01 is compared with a threshold V1, and the output from the output terminal P02, that is, the voltage after conversion, is compared with a threshold V2, while a difference between both voltages is compared with a threshold V3. If any one of the voltages exceeds the threshold, this is determined to be a lifetime end stage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting circuit having a function of detecting the end of life of a discharge lamp.

  Conventionally, as seen in Patent Documents 1 to 4, there has been proposed a discharge lamp lighting circuit that has an inverter circuit and a resonance circuit connected to the output side of the inverter circuit, and controls the lighting of the discharge lamp with the resonance circuit output. Yes. By the way, a fluorescent lamp is generally used as a discharge lamp, but in the case of a fluorescent lamp, among the electron emitting materials (called emitters) of the filament at the end of its lifetime, the so-called electron emitting material of only one filament is consumed. A half-wave discharge phenomenon may occur due to one-side Emires, and a phenomenon in which the tube voltage increases due to so-called both-side Emiles where the electron emission materials of the filaments on both sides are consumed tends to occur. Therefore, it is desired to further improve the reliability by detecting the phenomenon at the end of the life of the discharge lamp to protect the discharge lamp lighting circuit.

  In Patent Document 1, as shown in FIG. 9, a series circuit of resistors R1 and R2 is connected between the power supply line to the discharge lamp and the ground, and a DC component detecting capacitor C3 is connected in parallel to the resistor R2. From the connected detection circuit, the voltage comparison circuit 2 that compares the voltage generated in the capacitor C3 with the reference voltage value, and the control circuit 3 that receives the detection output of the voltage comparison circuit 2 and reduces the output of the inverter circuit A technique for detecting the end of lamp life and protecting the circuit is described.

  In Patent Document 2, as shown in FIG. 14, a lamp voltage direct current component for detecting a half-wave discharge that is composed of resistors R 1 and R 2 and a capacitor C 2 and is generated in a one-side Emires state at the end of the life of the discharge lamp La. In addition to a detection circuit, a capacitor C3, diodes D1 and D2, resistors R3 and R4 are provided, and a tube voltage beak detection circuit is provided for detecting an increase in tube voltage that occurs in both-side Emires state at the end of the lamp life. Discharge lamp lighting devices have been proposed. The outputs of these two detection circuits are synthesized via diodes D3 and D4, exceed a voltage generated when the discharge lamp La is normal, and have a predetermined value less than a voltage generated at the end of its life, such as the end of life of the discharge lamp La. It is determined whether or not a phenomenon that occurs in the above occurs.

  Also, in the same document 2, as shown in FIG. 1 and FIG. 2, the combined value of the direct current voltage component detected by the half-wave discharge caused by one-side Emires and the tube voltage are extracted and led to the OR circuit. A circuit for determining the end of life is described.

  Patent Document 3 discloses a DC voltage detection circuit that detects a DC component of voltage generated at both ends of a discharge lamp, and stops the oscillation of the high-frequency inverter circuit or suppresses the output when there is an output exceeding a predetermined level from the DC voltage detection circuit. There has been proposed a discharge lamp protection device that includes an inverter circuit control means that reliably detects the end of life of a discharge lamp.

Patent Document 4 discloses a positive potential peak detection circuit for detecting a positive potential peak voltage supplied to a discharge lamp, which is connected to a middle point of a coupling capacitor and a choke coil of an inverter circuit, and a negative potential supplied to a discharge lamp. A negative potential peak detection circuit that detects a peak voltage and a life end detection circuit that detects the end of life of a discharge lamp according to the detected positive potential and the negative potential peak voltage have been proposed. Specifically, FIG. 1 shows a capacitor C4 for synthesizing positive and negative peak potentials. FIG. 4 shows capacitors C4A and C4B for individually detecting positive and negative peak potentials, an operational amplifier OP1 for inverting one polarity, and both A comparator TL3 for detecting a potential difference is described.
Japanese Patent No. 3797079 Japanese Patent No. 3941360 JP 2006-228755 A JP 2007-66700 A

  Patent Documents 1 to 4 detect a positive-potential-side lamp voltage DC component and a negative-potential-side lamp voltage DC component, determine the occurrence of one-side Emires from the detection results, and control the oscillation of the inverter circuit, or The voltage (tube voltage) across the discharge lamp is detected, and the oscillation of the inverter circuit is controlled from the detection result. By the way, at the end of the life of a discharge lamp, as described above, both sides of Emires may occur or only one side of Emires may occur, so the DC component and tube voltage on each potential side are detected respectively. Judgment is desired for more appropriate protection of the inverter circuit. However, providing each circuit individually is not preferable because it leads to an increase in circuit size and cost due to an increase in the number of parts.

  In addition, since the circuit described in FIGS. 1 and 2 of Patent Document 2 uses a voltage obtained by combining both positive and negative voltage DC components, the presence or absence of an Emiles (end of life) state for each filament is determined. It cannot be judged.

  Further, in the case of one-side Emires, the rising change of the lamp voltage DC component does not necessarily appear greatly, so that it is not easy to determine the end of life. In particular, the lamp voltage has a temperature characteristic, and when the temperature of the discharge lamp is based on room temperature, the lamp voltage tends to decrease as the temperature increases from room temperature. Therefore, when the tube temperature rises and is in a high temperature state, even a discharge lamp in the end of life state may be erroneously determined as normal.

  The present invention has been made in view of the above, and detects the smoothed voltage on both potential sides with a simple circuit configuration, and obtains the detected voltage on both potential sides and the difference between them by arithmetic processing from the detected smoothed voltage. The present invention provides a discharge lamp lighting circuit that makes this determination more accurately.

  According to a first aspect of the present invention, there is provided a discharge lamp lighting circuit that controls the power supply when a discharge lamp that is lit by receiving power supply from an inverter circuit is determined to have reached the end of its life. A rectifier circuit that rectifies the potential, and a first detection circuit that smoothes a rectified voltage of one potential and divides the smoothed voltage into a voltage within a first predetermined range by a voltage dividing resistor to obtain a first detection voltage. And smoothing the rectified voltage of the other potential, the smoothed voltage is a voltage dividing resistor in which the smoothed voltage is applied to one end and a predetermined power supply voltage having the same potential as the one potential is applied to the other end, A second detection circuit that obtains a second detection voltage by dividing the voltage into a voltage within a second set range having the same potential as that of one potential side; and the first and second detection voltages that are A / D converted. One of the first and second detection voltages is made to coincide with the change range of the other detection voltage. And a calculation unit having a conversion unit that performs a calculation, and the calculation unit is further obtained by the calculation unit, and is converted from the first and second detection voltages, and the first and second converted voltages. A first comparison unit that outputs a control signal when at least one of the detection voltages not converted among the detection voltages exceeds a threshold value corresponding to the end of life set for each potential side; and The difference between the obtained converted voltage of the first and second detection voltages and the unconverted detection voltage of the first and second detection voltages is calculated, and this difference voltage is the tube voltage. And a second comparison means for outputting a control signal when a threshold value corresponding to the end of life set for the first and second comparison means is exceeded, and with respect to the inverter circuit by the control signal from the first and second comparison means It is characterized by controlling the power supply Than is.

  According to the present invention, the voltage across the discharge lamp is rectified into both positive and negative potentials by the rectifier circuit. Then, the rectified voltage of one potential is smoothed by the first detection circuit, and the smoothed voltage is divided by the voltage dividing resistor into a voltage within the first predetermined range, whereby the first detected voltage is obtained. On the other hand, the rectified voltage of the other potential is smoothed by the second detection circuit, and this smoothed voltage is applied to one end and a predetermined power supply voltage equal to the one potential is applied to the other end. The second detection voltage is obtained by dividing the voltage into a voltage within the second set range having the same potential as that of one potential side. Then, the conversion unit of the calculation means converts the first and second detection voltages, which are A / D converted, so that one of the first and second detection voltages coincides with the change range of the other detection voltage. . Further, the calculating means has first comparing means and second comparing means, and is obtained by the calculating means by the first comparing means, and after being converted from the first and second detection voltages. A control signal is output when at least one of the converted voltage and the unconverted detection voltage of the first and second detection voltages exceeds a threshold value corresponding to the end of life set for each potential side. Further, the converted voltage obtained by the second comparing means by the calculating means and converted from the first and second detected voltages and the detected voltage not converted from the first and second detected voltages. The control signal is output when the difference voltage exceeds a threshold value corresponding to the end of life set for the tube voltage. Then, the power supply is controlled to the inverter circuit by a control signal from the first and second comparison means.

  As described above, the second detection circuit can obtain a detection signal having the same potential as that of the first detection circuit by using a predetermined power supply voltage. Therefore, the circuit 2 detects and divides the voltage DC component on both electrode sides. The number of parts is reduced as compared with the prior art that requires a system. Further, the end of life is more accurately detected by comparing the detection voltage obtained from the smooth voltage on both potential sides and the difference between the detection voltage and the threshold value.

  According to a second aspect of the present invention, in the discharge lamp lighting circuit according to the first aspect, the one potential is a positive potential, and the conversion unit converts the second detection voltage to a voltage within the first set range. It is characterized by converting to According to this configuration, it is possible to use the arithmetic means at a positive potential which is a normal usage mode, and the circuit design is facilitated.

  According to a third aspect of the present invention, in the discharge lamp lighting circuit according to the second aspect of the present invention, the discharge lamp lighting circuit includes a DC power source that generates a voltage of a predetermined level for driving the arithmetic means, and the predetermined circuit of the second detection circuit The power supply voltage is a voltage of the DC power supply. According to this configuration, since the power source for driving the arithmetic means can be used also as the power source for voltage division, the circuit configuration becomes easy.

  A fourth aspect of the present invention is the discharge lamp lighting circuit according to any one of the first to third aspects, further comprising an adjusting unit that changes the threshold values. According to this configuration, it is possible to set a threshold value corresponding to the lighting condition of the discharge lamp.

  According to a fifth aspect of the present invention, in the discharge lamp lighting circuit according to any one of the first to fourth aspects of the present invention, the discharge lamp lighting circuit includes a temperature sensor that detects a temperature in the vicinity of the discharge lamp. It has the correction means which correct | amends each threshold value, It is characterized by the above-mentioned. According to this configuration, the threshold value is corrected to an appropriate threshold value corresponding to the continuation of lighting and the operating environment temperature of the discharge lamp, so that the influence of the temperature characteristic of the discharge lamp is suppressed.

  According to the first aspect of the present invention, the number of parts can be reduced as compared with the prior art in which two systems of circuits for detecting and dividing the voltage DC component on both potential sides are required. Further, the end of life is more accurately detected by comparing the detection voltage obtained from the smooth voltage on both potential sides and the difference between the detection voltage and the threshold value.

  According to the second aspect of the present invention, it is possible to use the arithmetic means at the positive potential which is a normal use mode, and the circuit design can be facilitated.

  According to the third aspect of the present invention, since the power source for driving the arithmetic means can also be used as the power source for voltage division, the circuit configuration can be simplified.

  According to the invention described in claim 4, it is possible to set the threshold value corresponding to the lighting condition of the discharge lamp.

  According to the fifth aspect of the invention, since the threshold value is corrected to an appropriate threshold value corresponding to the continuation of lighting and the operating environment temperature of the discharge lamp, the influence of the temperature characteristics of the discharge lamp can be suppressed.

  FIG. 1 is an overall block diagram showing an embodiment of a discharge lamp lighting circuit according to the present invention. In the present embodiment, the discharge lamp lighting circuit 1 is driven by connecting a commercial AC power supply AC via an outlet or the like. The diode bridge DB is for full-wave rectification of the commercial AC power supply AC. A boost chopper circuit 10 is connected to the output side of the diode bridge DB. The step-up chopper circuit 10 includes a choke coil Lc, a switching element Q1, a rectifier diode D1, and a smoothing capacitor C1, and generates a predetermined voltage, here 360 V, at one end of the smoothing capacitor C1. The switching element driving circuit 11 is connected to the base of the switching element Q1, and controls the driving of the switching element Q1.

  The microcomputer (arithmetic unit) 12 inputs and outputs signals to and from each circuit unit. For example, the microcomputer 12 outputs a control signal to the switching element driving circuit 11 to drive the switching element Q1 on and off so that the smoothing capacitor C1 is charged to a predetermined voltage. The AC input detection circuit 13 is connected between the commercial AC power supply AC line and the ground, detects the connection state of the commercial AC power supply AC, and outputs the detection result to the microcomputer 12. The choke coil output detection circuit 14 is connected to the secondary side of the choke coil Lc and detects whether or not electric power is supplied from the diode bridge DB to the choke coil Lc, and outputs the detection result to the microcomputer 12. . The control circuit power supply circuit 15 generates power supply voltages (14 V and 5 V) for the microcomputer 12, a half-bridge drive circuit 16, which will be described later, the end of life detection circuit 18, and the like, using the voltage generated by the boost chopper circuit 10. Is.

  The half bridge drive circuit 16 outputs drive pulses that alternately become high and low based on a control signal from the microcomputer 12 to the inverter circuit 17. The inverter circuit 17 includes switching elements Q2 and Q3 connected in series, an induction reactor L1 for forming a resonance circuit on the output (load) side, and capacitors C2 and C3. A discharge lamp FL is detachably connected in parallel with the capacitor C3 of the resonance circuit. The capacitor C2 is for direct current cut. The switching elements Q2 and Q3 are alternately turned on and off by receiving drive pulses having opposite phases from the half-bridge drive circuit 16. Accordingly, the discharge lamp FL is supplied with power from a predetermined power source (360 V in this embodiment) converted into high-frequency power by the on / off operation and resonance operation of the switching elements Q2 and Q3, and both filaments are preheated. After that, it starts and lights up.

  The end-of-life detection circuit 18 is connected to both ends of the discharge lamp FL, has a circuit configuration to be described later, and outputs the detected voltage to the microcomputer 12. The microcomputer 12 performs conversion or calculation processing, which will be described later, based on the detection voltage from the end-of-life detection circuit 18 to determine and control the end-of-life of the discharge lamp FL.

  The power supply voltage detection circuit 19 detects the level of the voltage generated by the boost chopper circuit 10. The microcomputer 12 controls the on / off timing of the switching element Q1 via the switching element drive circuit 11 so that the level of the voltage generated by the boost chopper circuit 10 is stabilized based on the detection result of the power supply voltage detection circuit 19. . The remote control light receiving circuit 20 receives an instruction signal transmitted by infrared modulation from, for example, a portable operation unit (remote control) outside the figure. The microcomputer 12 performs on / off control and dimming control according to the light reception signal from the remote control light receiving circuit 20.

  FIG. 2 is a circuit diagram showing an example of the circuit configuration of the end of life detection circuit 18. The end-of-life detection circuit 18 inputs a voltage between the filaments (tube voltage) from the high voltage side of the capacitor C3 constituting the inverter circuit 17. This input path is provided with voltage dividing resistors R11, R12, and R13 connected in series with the ground, and takes in the tube voltage from the midpoint A0 of the resistors R12 and R13. Diodes D11 and D12 having opposite directions are connected to the middle point A0. That is, the diode D11 is in the forward direction with respect to the midpoint A0, and the diode D12 is connected in the reverse direction with respect to the midpoint A0.

  The cathode side of the diode D11 is a circuit for detecting a smoothing voltage corresponding to the peak value of the positive potential, and the anode side of the diode D12 is a circuit for detecting the smoothing voltage corresponding to the peak value of the negative potential. . The smoothing voltage detection circuit according to the peak value of the positive potential includes a diode D11, a Zener diode ZD11 connected in parallel between the cathode of the diode D11 and the ground, and a capacitor C12, and a series voltage dividing resistor. R14, R15, and a capacitor C13 connected to both ends of the voltage dividing resistor R15, and a midpoint between the voltage dividing resistors R14 and R15 is an output terminal Po1 to the microcomputer 12.

  On the other hand, the smoothing voltage detection circuit corresponding to the peak value of the negative potential includes a diode D12, a Zener diode ZD12 and a capacitor C14 connected in parallel between the anode of the diode D12 and the ground, respectively, and the anode of the diode D12. And a series voltage dividing resistor R16, R17, R18 interposed between the power supply ei having a predetermined voltage. Further, the capacitor C15 is connected between the midpoint of the voltage dividing resistors R16 and R17 and the ground, and the midpoint of the voltage dividing resistors R16 and R17 is an output terminal Po2 to the microcomputer 12. .

  Here, the operation of the end of life detection circuit 18 will be described. However, the voltage of the power source ei is 5V, the Zener voltage of the Zener diodes ZD11 and ZD12 is 10V (volts), and the voltage dividing ratio of the voltage dividing resistors R11, R12, and R13 is the diode D11, The voltage taken into D12 is set to be a predetermined level of at least 10V or less. Further, the voltage dividing resistors R14 and R15 have the same resistance value, and the voltage dividing resistors R16, R17, and R18 all have the same resistance value.

  First, the operation on the positive potential side will be described. The tube voltage divided to a predetermined level is half-wave rectified on the positive potential side by the diode D11, limited to 10 V or less by the Zener diode ZD11, and charged by the capacitor C12, so that the smoothing according to the peak value of the positive potential is achieved. A voltage is obtained. The smoothed voltage of the capacitor C12 is divided by half by the voltage dividing resistor R15 and input to the microcomputer 12 from the output terminal Po1.

  FIG. 3 is a diagram illustrating the relationship between the voltage of the capacitor C12 (horizontal axis) and the voltage of the output terminal Po1 (vertical axis). As shown in FIG. 3, when the smoothing voltage of the capacitor C12 is 0V, the voltage at the output terminal Po1 is also 0V, and the smoothing voltage of the capacitor C12 is At the maximum of 10V, the voltage at the output terminal Po1 is 5V, and during this time, it can be seen that it changes linearly as shown by the solid line in the figure. Therefore, in the microcomputer 12, considering that the voltage change is 0 to 5V, Emires is generated on the high voltage side of the filament and the end of life is reached, and the voltage waveform becomes half-wave discharge and biased to the positive potential side. As a result, a threshold value V1 (see FIG. 5) for determining the end of life may be set in advance and compared with the input voltage from the output terminal Po1.

  Next, the operation on the negative potential side will be described. The tube voltage divided to a predetermined level is half-wave rectified on the negative potential side by the diode D12, limited to -10V or more by the Zener diode ZD12, and charged by the capacitor C14, so that the tube voltage corresponds to the peak value of the negative potential. A smooth voltage is obtained. The smoothing voltage of the capacitor C14 is divided by the voltage dividing resistors R16, R17, and R18 with + 5V of the power source ei. Here, since the resistance values of the voltage dividing resistors R16, R17, and R18 are equal, a voltage in the following range is obtained at the output terminal Po2.

  FIG. 4 is a diagram showing a relationship for obtaining a converted value from the capacitor C14. FIG. 4A shows a relationship between the voltage of the capacitor C14 (horizontal axis) and the voltage of the output terminal Po2 (vertical axis). b) shows the relationship between the absolute value (horizontal axis) of the voltage of the capacitor C14 and the converted value (vertical axis). When the smoothing voltage 0 to -10V generated in the capacitor C14 is applied with the minimum voltage of -10V, + 5V and -10V are divided into 2/3 (that is, 1 to 2) at the output terminal Po2. Voltage, that is, 0V is output. In addition, when the maximum voltage of 0V is applied to the capacitor C14, a voltage obtained by dividing + 5V and 0V into 2/3, that is, + 3.33V, is output to the output terminal Po2. In the meantime, it can be seen that the line changes linearly as shown by the solid line in FIG.

  Note that the slope of the solid line shown in FIG. 4A differs from the slope of the positive potential side shown in FIG. 3 in both the slope and direction, so that the negative potential side can be handled with the same scale as the positive potential side. Can not. Therefore, the microcomputer 12 performs an operation of multiplying the input voltage from the output terminal Po2 by 3/2 to obtain a characteristic line indicated by a broken line in FIG. 4A so that it matches the gradient of FIG. ing. Further, in order to reverse the direction of the gradient and make them coincide (see FIG. 4B), the value is subtracted from 5V.

  That is, the converted value is obtained by calculating 5V-Po2 voltage * (3/2). Therefore, in the microcomputer 12, the smoothed voltage generated in the capacitor C14 corresponds to 0 to -10V and the converted value becomes 0 to + 5V, so that the processing is replaced with a positive potential, that is, the emiles occur on the low voltage side of the filament. As a result of the end of life and half-wave discharge resulting in a voltage waveform biased to the negative potential side, the threshold V2 (see FIG. 5) for determining the end of life is set to the same polarity as the end of life for Emiles on the high voltage side This makes it possible to simplify the circuit configuration. The conversion straight line in FIG. 4B can be calculated by conversion by the microcomputer 12, but the calculation result is stored in advance as a storage unit such as an LUT (lookup table) or a conversion unit. Referring to this is preferable from the viewpoint of reducing the software load and processing speed.

  5 to 8 show the tube voltage, the smooth voltage according to the positive potential peak value, the Po1 voltage, the smooth voltage according to the negative potential peak value, the Po2 voltage, the Po2 converted value, and the Po1 voltage and the Po2 converted value ( FIG. 5 is a diagram showing the relationship between the voltage and the differential voltage. FIG. 5 shows a case where the discharge lamp FL is normal, FIG. 6 shows a case where the discharge lamp FL is at the end of its life due to high-pressure side Emiles, and FIG. Is the end of life due to low-pressure side Emires, FIG. 8 is a relationship diagram when the discharge lamp FL is at the end of life due to both-side Emires.

  In FIG. 5, the voltage at the output terminal Po1 on the positive potential side is less than the threshold value V1, and the conversion value (Po2 conversion value in FIG. 5) obtained by converting the voltage at the output terminal Po2 on the negative potential side with the above equation is the threshold value V2. Since the difference between the output terminal Po1 voltage and the output terminal Po2 converted value is less than the threshold value V3, it can be seen that the discharge lamp FL is normal.

  In FIG. 6, the voltage at the output terminal Po1 on the positive potential side exceeds the threshold value V1, while the converted value obtained by converting the voltage at the output terminal Po2 on the negative potential side with the above equation (Po2 conversion value in FIG. 6). Is less than the threshold value V2, and the difference between the output terminal Po1 voltage and the output terminal Po2 converted value exceeds the threshold value V3, it can be seen that the discharge lamp FL is at the end of its life due to the high-pressure side Emires.

  In FIG. 7, the voltage at the output terminal Po1 on the positive potential side is less than the threshold value V1, while the converted value (Po2 conversion value in FIG. 7) obtained by converting the voltage at the output terminal Po2 on the negative potential side with the above equation is Since the threshold value V2 is exceeded and the difference between the output terminal Po1 voltage and the output terminal Po2 converted value exceeds the threshold value V3, it can be seen that the discharge lamp FL is at the end of its life due to the low-pressure side Emires.

  In FIG. 8, the voltage at the output terminal Po1 on the positive potential side exceeds the threshold value V1, and the converted value (the converted Po2 value in FIG. 5) obtained by converting the voltage at the output terminal Po2 on the negative potential side with the above equation is the threshold value. Since V2 is exceeded and the difference between the output terminal Po1 voltage and the output terminal Po2 converted value is less than the threshold value V3, it can be seen that the discharge lamp FL is at the end of its life due to both-side Emires.

  FIG. 9 is a functional block diagram of a portion related to determination of the end of life of the microcomputer 12. The microcomputer (calculation means) 12 is connected to the ROM 121 and the RAM 122. The ROM 121 stores an end-of-life determination processing program and converted data shown in FIG. 4B as an LUT. The RAM 122 temporarily stores data being processed.

  The microcomputer 12 includes each potential-side detection voltage comparison unit 123, a difference comparison unit 124, a determination unit 125, a threshold change setting unit 126, and a threshold correction unit 127 as function execution units. Each potential-side detection voltage comparison unit 123 compares the input value from the output terminal Po1 with a threshold value V1 that can be determined as the end of life for one side (high-voltage side) Emiles. In addition, each potential side detection voltage comparison unit 123 compares the input value from the output terminal Po2 with a value converted as shown in FIG. 4B by the LUT in the ROM 121 and a preset one-side Emires (low-voltage side). This is to compare the magnitude with the threshold value V2 that can be determined as the end of life.

  The difference comparison unit 124 calculates the absolute value of the difference between the input value from the output terminal Po1 and the input value from the output terminal Po2 and converted as shown in FIG. 4B. This is to compare the value and the threshold value V3 that can be determined as the end of life for the difference. By converting the input value from the output terminal Po2 as shown in FIG. 4B, the direct difference from the input value from the output terminal Po1 can be obtained. Further, the absolute value of the difference is because there is no difference in the comparison result between the two sides even if one-side Emires occurs on either the high-pressure side or the low-pressure side. Furthermore, only by comparing the differences, if both the smoothing voltage on the positive potential side and the smoothing voltage on the negative potential side increase, the difference does not increase, but the intimidation voltage on both the positive potential and the negative potential increases. There is a high possibility that Emiles on both sides has occurred to some extent. In some cases, only the difference comparison unit 124 cannot effectively detect both-side Emires. Thus, each potential-side detection voltage comparison unit 123 detects each one-side Emires so that both one-side Emires and both-side Emires can be detected effectively.

  The determination unit 125 determines the end of life when the comparison result by the difference comparison unit 124 exceeds the threshold value V3. In addition, the determination unit 125 determines whether the input value from the output terminal Po1 exceeds the threshold value V1 or the input value from the output terminal Po2 by the potential side detection voltage comparison unit 123. When the threshold value V2 is exceeded, the end of life is determined.

  Here, the end of life determination process executed by the microcomputer 12 will be described with reference to FIG. The flowchart of FIG. 10 is started when the discharge lamp FL is turned on. The detection voltage is input from the output terminals Po1 and P02 (after being converted into a digital value by an A / D conversion circuit (not shown)). First, the input value from the output terminal P02 is displayed using the LUT in the ROM 121. 4 (b) is converted (step S1). Next, the absolute value of the difference between the input value from the output terminal P01 and the input value from the output terminal P02 and converted by the LUT is calculated, and the absolute value of the difference is compared with the threshold value V3. Performed (step S3). As a result of this comparison, it is determined whether or not the absolute value of the difference exceeds the threshold value V3 (step S5). If the absolute value of the difference exceeds the threshold value V3, it is determined that the end of life is reached, and inverter control instructions for the end of life are given (step S7). The inverter control instruction for the end of life is to control the output power to the inverter circuit 17 by the microcomputer 12. Specifically, a control pulse with a small on-duty is output to the gates of the switching elements Q2 and Q3 for the half-bridge drive circuit 16, or the operation of the inverter circuit 17 is stopped.

  On the other hand, when the absolute value of the difference is equal to or less than the threshold value V3, it is considered that either the discharge lamp FL is operating normally, or both sides of Emires or a state close thereto is occurring. Therefore, the magnitude comparison between the input value from the output terminal P01 and the threshold value V1 and the magnitude comparison between the input value from the output terminal P02 and the converted value and the threshold value V2 are performed (step S9). As a result of these magnitude comparisons, it is determined whether one of the values exceeds the threshold values V1 and V2 (step S11). If one of the values exceeds the threshold values V1 and V2, it is assumed that one-side emiles have occurred in the high-pressure or low-pressure filament (or that both-side emires have occurred), and inverter control for the end of life (Step S7). On the other hand, if both values are equal to or less than the threshold values V1 and V2, it is determined that the discharge lamp FL is normal, and this flow is terminated. By repeatedly executing this flowchart at a predetermined cycle, it becomes possible to quickly and effectively cope with an abnormality.

  In addition, the following aspects are employable for this invention.

(1) Returning to FIG. 9, the threshold value change setting unit 126 operates the operation unit 31 in the lighting state of the discharge lamp FL, for example, in the case of a lighting circuit having a plurality of dimming lighting modes. The threshold value is changed corresponding to the mode in accordance with the operation from. Each threshold value is stored in advance in the ROM 121 corresponding to the mode, and each threshold value selected by the threshold value change setting unit 126 is used as a threshold value for each potential-side detection voltage comparison unit 123 and difference comparison unit 124. For example, the operation unit 31 may be disposed at an appropriate position of the casing of the lighting circuit and can be set by a mode switching button or the like.

(2) The threshold value correction unit 127 shown in FIG. 9 corrects each threshold value used in each potential-side detection voltage comparison unit 123 and difference comparison unit 124 according to the temperature of the discharge lamp FL detected by the temperature sensor 32. Is. The temperature sensor 32 is disposed at an appropriate position near the discharge lamp FL. FIG. 11 is a characteristic diagram showing the relationship between the temperature of the discharge lamp FL and the smoothing voltage (detection voltage) described above. As shown in FIG. 11, the smoothed voltage has a peak when the temperature of the discharge lamp FL is around room temperature, and decreases as the temperature increases. Similarly, the smoothing voltage becomes smaller as the temperature of the discharge lamp FL becomes lower than room temperature. Therefore, if the threshold value is set at a predetermined temperature around room temperature, lighting continues, or if the temperature of the discharge lamp FL deviates from room temperature depending on the usage environment, even if the emiless occurs and the end of the life is reached, the smooth voltage Is detected as a low value, it may be erroneously determined to be normal. Therefore, the ROM 121 stores in advance the relationship between the temperature and the correction value as an LUT, and the correction value corresponding to the detected temperature may be added to the original threshold value, or may be calculated using a correction formula. Good. The correction may be set so that the threshold value becomes smaller corresponding to the characteristic of FIG.

(3) In the flowchart of FIG. 10, the comparison process of the difference comparison unit 124 is performed before the process of each potential-side detection voltage comparison unit 123, but the reverse may be possible.

(4) In this embodiment, the input value from the output terminal P02 corresponding to the negative potential side smoothing voltage is converted by the LUT as shown in FIG. 4B, but conversely, the input value from the output terminal P01 is converted. 4 (a)
You may convert so that it may become the same ruler as the solid line.

(5) In this embodiment, + 5V is adopted as the power source ei and the minimum detection voltage of the capacitor C14 on the high voltage side is set to −10V. However, the present invention is not limited to this, but the voltage divider resistors R16, R17, and R18 are important. As a result, when the voltage is the minimum detection voltage of the capacitor C14, the voltage at the output terminal P02 may be divided so that the voltage is 0 V, and the voltage dividing resistors are not limited to three of R16, R17, and R18. Depending on the resistance value, it may be at least two, or may be three or more. Therefore, the voltage dividing resistors R16, R17, and R18 need not have the same resistance value. By doing so, two voltage-dividing resistors are required when a voltage / DC component detection circuit on both the positive and negative electrodes is provided together as in the prior art, but in this embodiment, only one system is sufficient. Therefore, the number of parts can be reduced accordingly.

1 is an overall block diagram showing an embodiment of a discharge lamp lighting circuit according to the present invention. It is a circuit diagram which shows an example of a circuit structure of a life end detection circuit. It is a figure which shows the relationship between the voltage (horizontal axis) of the capacitor | condenser C12, and the voltage (vertical axis) of output terminal Po1. It is a figure which shows the relationship between the voltage (horizontal axis) of the capacitor | condenser C14, and the voltage (vertical axis) of output terminal Po2. Tube voltage, smooth voltage according to positive potential peak value, Po1 voltage, smooth voltage according to negative potential peak value, Po2 voltage, Po2 converted value, and differential voltage between Po1 voltage and Po2 converted value (voltage) It is a figure which shows a relationship, and is a relationship figure in case the discharge lamp FL is normal. Tube voltage, smooth voltage according to positive potential peak value, Po1 voltage, smooth voltage according to negative potential peak value, Po2 voltage, Po2 converted value, and differential voltage between Po1 voltage and Po2 converted value (voltage) It is a figure which shows a relationship, and is a relationship figure in case the discharge lamp FL is the end of life by the high pressure side Emires. Tube voltage, smooth voltage according to positive potential peak value, Po1 voltage, smooth voltage according to negative potential peak value, Po2 voltage, Po2 converted value, and differential voltage between Po1 voltage and Po2 converted value (voltage) It is a figure which shows a relationship, and is a relationship figure in case the discharge lamp FL is the end of life by the low pressure side Emires. Tube voltage, smooth voltage according to positive potential peak value, Po1 voltage, smooth voltage according to negative potential peak value, Po2 voltage, Po2 converted value, and differential voltage between Po1 voltage and Po2 converted value (voltage) It is a figure which shows a relationship, and is a relationship figure in case the discharge lamp FL is the end of life by both sides Emires. It is a functional block diagram of the part regarding determination of the end of life of a microcomputer. It is a flowchart of the end-of-life determination process performed by the microcomputer. It is a characteristic view which shows the relationship between the temperature of a discharge lamp, and the smooth voltage (detection voltage) of each electric potential side.

Explanation of symbols

1 discharge lamp lighting circuit 12 microcomputer 18 end of life detection circuit FL discharge lamp R11, R12, R13 voltage dividing resistor D11, D12 diode C12, C14 capacitor R14, R15, R16, R17, R18 voltage dividing resistor 122 RAM
123 Each potential side detection voltage comparison unit 124 Difference comparison unit 125 Determination unit 126 Threshold change setting unit 127 Threshold correction unit

Claims (5)

In the discharge lamp lighting circuit that controls the power supply when it is determined that the discharge lamp that is lit by receiving power supply from the inverter circuit is at the end of its life,
A rectifier circuit that rectifies the voltage across the discharge lamp into both positive and negative potentials, and smoothes the rectified voltage of one potential, and divides the smoothed voltage into a voltage within a first predetermined range by a voltage dividing resistor to perform first detection. A first detection circuit for obtaining a voltage and a rectified voltage of the other potential are smoothed. The smoothed voltage is applied to one end and a predetermined power supply voltage having the same potential as the one potential is applied to the other end. A second detection circuit that obtains a second detection voltage by dividing the voltage into a voltage within a second set range having the same potential as that of one potential side, and the first and second detection voltages; And an arithmetic means having a conversion unit that performs conversion for matching one of the first and second detection voltages subjected to A / D conversion with a change range of the other detection voltage,
The calculation means further includes at least a conversion voltage obtained by the calculation means and converted after the first and second detection voltages and a detection voltage not converted among the first and second detection voltages. A first comparator that outputs a control signal when one exceeds a threshold value corresponding to the end of life set for each potential side, and the first and second detection voltages obtained by the arithmetic unit; The difference between the converted voltage after conversion and the detection voltage not converted among the first and second detection voltages is calculated, and the threshold corresponding to the end of life set for the tube voltage is set as the difference voltage. And a second comparison means for outputting a control signal when exceeding the control circuit, and causing the inverter circuit to control the power supply by a control signal from the first and second comparison means. Electric light lighting circuit. 2. The discharge lamp lighting circuit according to claim 1, wherein the one potential is a positive potential, and the conversion unit converts the second detection voltage into a voltage within the first setting range. 3. The DC power supply for generating a voltage of a predetermined level for driving the arithmetic means, wherein the predetermined power supply voltage of the second detection circuit is a voltage of the DC power supply. The discharge lamp lighting circuit described. The discharge lamp lighting circuit according to claim 1, further comprising an adjustment unit that changes each of the threshold values. The temperature sensor which detects the temperature of the said discharge lamp vicinity is provided, The said calculating means has a correction means which correct | amends each said threshold value according to detected temperature, The one in any one of Claims 1-4 characterized by the above-mentioned. Discharge lamp lighting circuit.

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