JP4475148B2 - Discharge lamp lighting device and lighting fixture including the same - Google Patents

Description

  The present invention relates to a discharge lamp lighting device for stably lighting a discharge lamp and a lighting fixture including the same, and more particularly to protection control when an output terminal is in a ground fault state in output control of a power conversion circuit.

  Conventionally, a discharge lamp lighting device has been used in which DC power obtained by rectifying and smoothing a battery or AC current is converted into a form required by a discharge lamp in a power conversion circuit, and the discharge lamp is lit stably. ing. In Patent Document 1, as shown in FIG. 6, when supplying alternating current power obtained by alternating direct current power from the DC-DC conversion circuit 1 using the inverter circuit 2 to the lamp, the lamp current is supplied to the DC-DC conversion circuit 1. Detection is performed by a current detection resistor r inserted between one end of the output end and one end of the input end of the inverter circuit 2, and the detection result is compared with the command value Vk in the error amplifier 3, and according to the comparison result. The lamp circuit is controlled by the PWM circuit 4 adjusting the PWM signal to the switching element q <b> 1 constituting the DC-DC conversion circuit 1.

  One end of the input terminal of the inverter circuit 2 to which one end of the current detection resistor r is connected is a ground line of the circuit, and a voltage signal generated at the other end of the current detection resistor r is input to the error amplifier 3 as a current detection signal. is doing. As a result, as shown in FIG. 6, even if the output terminal of the inverter circuit 2 is grounded, the ground fault current flowing from the smoothing capacitor C at the output terminal of the DC-DC conversion circuit 1 through the transistor q3 of the inverter circuit 2 By forming a circuit that returns to the smoothing capacitor c through the current detection resistor r, the ground fault current is also detected by the current detection resistor r, and the ground fault current can be suppressed. .

  Further, in Patent Document 2, if a current detection resistor is connected in the same configuration as in FIG. 6 and an overcurrent flows even after a predetermined time has elapsed after the discharge lamp lighting device starts, an overcurrent due to a ground fault is generated. Judging that it is flowing, the discharge lamp lighting device is stopped and protected.

Further, in Patent Document 3, immediately after the operation of the discharge lamp lighting device, when the output voltage or output current of the discharge lamp lighting device generated when the discharge lamp is in the unlit state deviates from the assumed range, the output terminal is The discharge lamp lighting device is protected by assuming that it is grounded and stopping. Specifically, since the load current does not flow in the unlit state, the output voltage rises to a predetermined no-load secondary voltage that is higher than that in the steady-lit state, but is assumed to rise to the no-load secondary voltage. If the load current flows more than a predetermined value, or if the output voltage does not rise to the predetermined voltage, it is determined that there is a ground fault.
Japanese Patent Laid-Open No. 7-298613 Japanese Patent Laid-Open No. 9-50893 JP-A-8-250289

  In the examples of Patent Documents 1 and 2, even if a ground fault occurs, the current is detected by the lamp current detection circuit, and the ground fault state may be a normal low-impedance ground fault such as a short circuit to a ground line or a housing. For example, overcurrent flows and it can be determined that a ground fault has occurred, but even if a ground fault has occurred, if it has a certain impedance due to carbonization of the output wiring, it does not become an overcurrent, There is a problem that it cannot be protected. Also, it cannot be determined whether the current that is flowing is the current flowing through the load or the ground fault current, and even if an overcurrent flows, it is difficult to distinguish whether it is a ground fault current or a short-circuit current , I want to stop and protect the ground fault quickly.For example, when the lamp is cold, the gas pressure is low and the terminal voltage is low. There is also a problem that it is not possible to distinguish between protective actions such as wanting to make the time until the ground fault longer.

  Further, in the example of Patent Document 3, it is determined that a ground fault has occurred if the behavior of the output voltage or output current in the lamp extinction state immediately after the start of operation deviates from the normal state. When the no-load voltage output polarity is fixed at a predetermined polarity, there is a problem that even if the ground fault at one end of the output can be detected, the ground fault at the other end cannot be detected.

  An object of the present invention is to provide a discharge lamp lighting device capable of reliably detecting any ground fault at the output end, including a high impedance ground fault, and accurately determining whether it is a ground fault or a short circuit. It is providing a lighting fixture provided with it.

The discharge lamp lighting device of the present invention includes a power conversion circuit that creates a desired DC voltage, an inverter circuit that switches the output voltage to create an alternating voltage and applies the same to the discharge lamp, and the output voltage of the power conversion circuit An output feedback control circuit that performs feedback control to achieve a desired DC voltage, and a PWM signal generation circuit that controls switching of the power conversion circuit in response to a PWM duty adjustment signal from the output feedback control circuit In the discharge lamp lighting device, the power conversion circuit and the inverter circuit are grounded on the power conversion circuit side and are inserted into a ground-side power line between the power conversion circuit and the inverter circuit. When a voltage detecting circuit for detecting an output voltage of the power converter circuit, a detection result of the current detection circuit Lighting of the discharge lamp is equal to or less than a first value predetermined to not be maintained, and the detection result of said voltage detection circuit is higher than the upper limit of the operating voltage of the discharge lamp, from a no-load condition where the discharge lamp is off Is less than a predetermined second value, a ground fault determination circuit that determines that the output terminal is in a ground fault state, and a detection result of the current detection circuit is equal to or lower than the predetermined first value, And a duty fixing circuit for fixing the level of the PWM duty adjustment signal to the level of the PWM duty adjustment signal when the no-load voltage rises .

  According to the above configuration, the generated DC voltage is switched to a DC-DC conversion circuit or an AC-DC conversion circuit that generates a desired DC voltage from a DC voltage from a DC power supply or an AC voltage from an AC power supply. In a discharge lamp lighting device comprising an inverter circuit that creates an alternating voltage and applies it to a discharge lamp, provided for equivalently detecting the lamp current and the lamp voltage of the discharge lamp for output feedback control. Using the current detection circuit and the voltage detection circuit that detect the voltage and current at the output terminal of the power conversion circuit, the ground fault determination circuit performs the ground fault determination as follows.

That is, the power conversion circuit and the inverter circuit are grounded on the power conversion circuit side, and the current detection circuit is inserted into the ground-side power line between the power conversion circuit and the inverter circuit. Therefore, even if any of the two output ends of the discharge lamp lighting device is grounded, the ground fault current does not flow to the current detection circuit, and the ground fault determination circuit determines the detection result of the current detection circuit in advance. since the lighting of the lamp discharge, which is the first value is equal to or less than can not become current maintenance, it is determined that there is a possibility of a ground fault. Even if the ground fault has an impedance of a certain level (for example, about several hundreds Ω), it does not rise to the no-load voltage at the time of starting, so the detection result of the voltage detection circuit is a second value determined in advance. Since it is higher than the upper limit of the lighting voltage of the discharge lamp and lower than the output voltage in the no-load state where the discharge lamp is extinguished, it is officially determined to be a ground fault state.

  With this configuration, even if any of the output ends of the discharge lamp lighting device has a ground fault and has a certain level of impedance, the discharge lamp can be turned off due to a power shortage due to a ground fault. Thus, it is possible to reliably detect a ground fault.

Further, by adjusting the level of the PWM duty adjustment signal given from the output feedback control circuit to the PWM signal generation circuit, the duty of the PWM signal given from the PWM signal generation circuit to the switching element of the power conversion circuit is controlled, In performing feedback control so that the output voltage of the power conversion circuit becomes the desired DC voltage, a duty fixing circuit is provided, and the detection result of the current detection circuit may be a ground fault when the detection result is equal to or less than the predetermined first value. When there is, the level of the PWM duty adjustment signal is fixed to the level of the PWM duty adjustment signal when the no-load voltage rises, so that in the case of a ground fault, the output current is not detected, and the output current that is no longer detected In contrast, the output feedback control circuit will further increase the output. Also, it is possible to prevent such problems.

  The discharge lamp lighting device of the present invention further includes a timer circuit that stops the operation of the power conversion circuit when a ground fault determination result by the ground fault determination circuit continues for a predetermined time.

  According to the above configuration, when the ground fault state occurs, the operation is not immediately stopped, but the timer circuit officially determines that the ground fault state has continued for a predetermined time, and the power conversion circuit Stop the operation.

  Therefore, since it is not determined that the terminal is short-circuited only when the terminal voltage at the beginning of the discharge lamp is low, erroneous determination can be prevented.

  In the discharge lamp lighting device of the present invention, the ground fault determination circuit gives an alternating stop signal to the inverter circuit when the detection result of the current detection circuit is equal to or less than a predetermined first value, and performs a polarity inversion operation. It is characterized by stopping.

  According to the above configuration, when a ground fault is detected, the polarity of the inverter circuit is fixed to the polarity through which the ground fault current flows, so that a reliable ground fault determination can be performed.

  Furthermore, a lighting fixture according to the present invention includes the discharge lamp lighting device, a housing for housing the discharge lamp lighting device, and a socket for connecting to the discharge lamp lighting device.

  According to the above configuration, even if any of the output ends of the discharge lamp lighting device has a ground fault and has a certain degree of impedance, it is a condition that the discharge lamp is extinguished due to power shortage due to the ground fault. It is possible to realize a lighting fixture that can reliably detect a ground fault.

  As described above, a discharge lamp lighting device and a lighting fixture including the same according to the present invention include a power conversion circuit that creates a desired DC voltage, and an inverter circuit that switches the output voltage to create an alternating voltage and applies it to the discharge lamp. In the discharge lamp lighting device comprising the power conversion circuit and the inverter circuit, the power conversion circuit side is grounded, and the voltage and current at the output terminal of the power conversion circuit are detected respectively. Using the current detection circuit and the voltage detection circuit, the ground fault determination circuit determines that there is a possibility of a ground fault because the detection result of the current detection circuit is equal to or less than a predetermined first value. Since the detection result of the detection circuit is equal to or less than a predetermined second value, it is officially determined that a ground fault condition has occurred.

  Therefore, even if any of the output terminals of the discharge lamp lighting device has a ground fault and has a certain level of impedance, it is definitely necessary to provide grounding if the discharge lamp is extinguished due to power shortage due to the ground fault. A fault can be detected.

[Embodiment 1]
FIG. 1 is a block diagram showing an electrical configuration of a discharge lamp lighting device 10 according to the first embodiment of the present invention. The discharge lamp lighting device 10 generally converts the input voltage Vin from the DC power source E to a desired voltage Vout by the DC-DC conversion circuit 11 and then converts the obtained DC power in the inverter circuit 12. Since it is assumed that the discharge lamp La is a high-intensity discharge lamp, the electric power is supplied to the discharge lamp La, which is a load, via the start circuit 13 for starting the discharge by applying a high voltage at the start. Supplying. The lamp current and lamp voltage of the discharge lamp La are detected equivalently from the voltage Vout and current Iout at the output end of the DC-DC conversion circuit 11, and the output feedback control circuit 15 of the control circuit 14 detects the detection. The stable lighting of the discharge lamp La is realized by adjusting the switching condition of the DC-DC conversion circuit 11 from the value through the PWM signal generation circuit 16 and controlling the output.

  The DC-DC conversion circuit 11 connects a series circuit of a primary winding N1 of a transformer T and a switching element Q0 between both terminals of a DC power supply E, and the switching element Q0 is received by a PWM signal from the PWM signal generation circuit 16. The voltage induced in the secondary winding N2 of the transformer T is rectified and smoothed by the diode D and the smoothing capacitor C, and a desired DC voltage Vout is output between the power supply lines 17 and 18. It is a converter.

  The inverter circuit 12 connects a series circuit of switching elements Q1, Q2 and Q3, Q4 between the power supply lines 17, 18, and connects the switching elements Q1, Q2; Q3, Q4 to the starting circuit 3. And the switching elements Q1, Q4 and Q2, Q3 which the drive circuit 20 forms a pair in response to the drive signal generated by the low frequency drive signal generation circuit 19 of the control circuit 14. Then, an alternating voltage of the voltage Vout is created and output.

  The PWM signal generation circuit 16 is a PWM duty adjustment signal of a DC voltage output from the output feedback control circuit 15 and can level discriminate the internally generated triangular wave to adjust the voltage Vout to a desired value. A so-called switch mode type PWM signal generation circuit that creates a PWM signal of duty, or a so-called current mode type PWM signal generation circuit that turns on when a switching element current is reached based on a PWM duty adjustment signal that is turned on at a predetermined cycle. Etc. Since the DC-DC conversion circuit 11, the inverter circuit 12, and the PWM signal generation circuit 16 have been described with general-purpose configurations, other configurations may be used.

  It should be noted that in the discharge lamp lighting device 10, the control circuit 14 is provided with a ground fault determination circuit 21, a timer circuit 22, a flip-flop 23 and an AND gate 24.

The ground fault determination circuit 21 includes two comparators 25 and 26 and a NOR gate 27. The output voltage Vout of the DC-DC conversion circuit 11 is input to the non-inverting input terminal of the comparator 25, and a predetermined reference voltage _VEF is input to the inverting input terminal. The output current Iout of the DC-DC conversion circuit 11 is converted into a voltage value by the current detection circuit B and input to the non-inverting input terminal of the comparator 26, and a predetermined current level is input to the inverting input terminal. The reference voltage I _ZC corresponding to is input. Outputs from the comparators 25 and 26 are input to the timer circuit 22 via the NAND gate 27.

  The timer circuit 22 includes an oscillator 28, an AND gate 29, and a counter 30. An output from the NAND gate 27 is given to one input of an AND gate 29, a low active system reset signal is inputted to the other input, and an output thereof is inputted to a reset input terminal of the counter 30. The The output from the oscillator 28 is given to the clock input terminal of the counter 30. Therefore, the counter 30 starts counting when the reset signal is not input from the AND gate 29, and when the predetermined count value is reached, the flip-flop A reset output is given to

  The flip-flop 23 is an RS flip-flop, and the system reset signal is input to a set input terminal. The output from the flip-flop 23 and the system reset signal are given to an AND gate 24, and control of the PWM signal passing / blocking from the PWM signal generating circuit 16 to the switching element Q0 is controlled.

  In the discharge lamp lighting device 10 configured as described above, the current detection circuit B is connected to the ground-side power source at the output terminal of the DC-DC conversion circuit 11 that supplies voltage and current at substantially the same level as the discharge lamp La. By connecting to the line 18 and grounding the DC power supply E side with respect to the current detection circuit B, any of the output terminals A1 and A2 of the discharge lamp lighting device 10 can be grounded as shown in FIG. A closed circuit can be formed in which a ground fault current does not flow to the current detection circuit B.

With such a circuit configuration, when the line from the output end of the discharge lamp lighting device 10 to the discharge lamp La is grounded, the power supplied to the discharge lamp La is reduced, and the discharge cannot be maintained and disappears. . Then, the output current of the DC-DC conversion circuit 11 flows through the ground side as a ground fault current from the ground fault point only through the path returning to the DC-DC conversion circuit 11, and the current flowing through the current detection circuit B as described above. Iout is substantially zero. Therefore, when no current flows in the current detection circuit B, it can be determined whether the discharge lamp La is in a no-load state in which the lamp is extinguished or in a ground fault state. Is compared with a reference voltage _{IZC for} determination which is a first value determined in advance. The reference voltage I _ZC is preferably set to a value lower than the lamp current that can be kept on even when the discharge lamp La is lit by DC.

Further, in order to facilitate the lighting of the discharge lamp La in the no-load state, the starting circuit 13 increases the output voltage of the inverter circuit 12 to a predetermined no-load voltage higher than the lighting voltage. Even if it is a ground fault having an impedance of about several hundreds of Ω, it does not rise to a predetermined no-load voltage, so that it is possible to distinguish the no-load condition from the ground fault condition. Therefore, the output voltage Vout of the power supply line 17 on the high level side of the DC-DC conversion circuit 11 captured by the line 17a which is a voltage detection circuit is higher than the upper limit of the lighting voltage of the discharge lamp La in the comparator 25. By comparing with a reference voltage V _{EF for} determination, which is a predetermined second value lower than the output voltage in the no-load state in which the discharge lamp La is turned off, either the no-load state or the ground fault state It is possible to determine whether or not.

Therefore, by determining the outputs from the comparators 25 and 26 by the NOR gate 27, it is possible to determine that a ground fault has occurred when the output current Iout is not detected and the output voltage Vout is not detected. On the other hand, since the increase in the output voltage Vout takes time even when there is no load when the discharge lamp La is not lit, the no-load voltage is increased in the normal state in consideration of the rise time of the no-load voltage in the normal state. If a ground fault is determined even after a determination period that is assumed to have reached at least the reference voltage V _EF has elapsed, it can be finally determined that a ground fault has occurred. Thus, since it is not determined that the short circuit is caused only when the terminal voltage at the beginning of the discharge lamp La is low, it is possible to accurately determine the ground fault.

  Therefore, the output of the NOR gate 27 is applied to one input of the AND gate 29, and when the ground fault is determined, the output becomes a low level, so that the output of the AND gate 29 also becomes a low level, and the counter 30 is reset. Is released and the count operation is started. When the ground fault determination is continued until the count value reaches the determination period, the counter 30 resets the flip-flop 23, whereby the output of the PWM signal is blocked by the AND gate 24, and the DC-DC conversion circuit 11. Is stopped and the ground fault protection operation is performed.

  With this configuration, even if any of the output ends of the discharge lamp lighting device 10 has a ground fault and has a certain level of impedance, the discharge lamp La is turned off due to power shortage due to the ground fault. If this is the case, it is possible to reliably detect a ground fault, block the PWM signal, and perform a protective operation, thereby suppressing an excessive ground fault current and preventing the discharge lamp lighting device 10 from being damaged. can do.

  Furthermore, when a ground fault occurs, the protection operation is not performed immediately, but it is determined by the timer circuit 22 whether or not the lamp La has started lighting. It is also possible to prevent erroneous determination in a state where the user is present.

  The power conversion circuit is not limited to the DC-DC conversion circuit 11 and may be an AC-DC conversion circuit that creates a desired DC voltage Vout. The current detection circuit B includes the AC-DC conversion circuit and the inverter circuit 12. The power source line 18 is connected to the ground, and is grounded in the AC-DC conversion circuit so that a closed circuit is formed so that a ground fault current does not flow to the current detection circuit B. .

  FIG. 2 is a cross-sectional view illustrating a configuration of a lighting fixture 101 including the discharge lamp lighting device 10 configured as described above. This illuminating device 101 is a headlamp used for vehicles such as automobiles, motorcycles, trains, and the like. Inside a lamp housing 102 (housing) fixed to the vehicle body of the vehicle, a lamp socket 103 and a reflector 104 are provided. The discharge lamp La is accommodated, and a lamp body lens 105 is attached to an opening provided in the front surface of the lamp body housing 102. An opening 106 for replacing the discharge lamp La is provided at the rear of the lamp housing 102, and a detachable cap 107 is attached to the opening 106.

  The above-mentioned discharge lamp lighting device 10 is housed and attached to the outside of the lower part of the lamp housing 102, and a power line CBL1 for supplying power using a battery as a DC power source is attached to the discharge lamp lighting device 10. Is connected. Further, the discharge lamp lighting device 10 and the lamp socket 103 are connected by a harness CBL2. And by attaching the discharge lamp La to the lamp socket 103, the electric power from the discharge lamp lighting device 10 is supplied to the discharge lamp La, and the discharge lamp La is lighted. And the illuminating device 101 is each arrange | positioned at the both right and left sides of the front part in the vehicle body of the vehicle 109 shown, for example in FIG.

[Embodiment 2]
FIG. 4 is a block diagram showing an electrical configuration of the discharge lamp lighting device 40 according to the second embodiment of the present invention. In this discharge lamp lighting device 40, the delay method from the determination of the ground fault to the operation stop of the DC-DC conversion circuit 11a by the timer circuit 22 is the same as that of the above-described discharge lamp lighting device 10, and the same configuration is the same. The same reference numerals are denoted by the suffix “a” for similar configurations. It should be noted that in this discharge lamp lighting device 40, the rectifying diode Da in the DC-DC conversion circuit 11a is disposed in the opposite polarity to the diode D of the discharge lamp lighting device 10, and the inverter circuit 12a The switching elements Q1a to Q4a are P-type while the switching elements Q1 to Q4 of the inverter circuit 12 are N-type, and the DC-DC conversion circuit 11a is a negative power source. This negative power source is suitably used for in-vehicle applications, and the discharge lamp La is a high-intensity discharge lamp for a headlamp.

In order to deal with the negative power supply, the output voltage Vout is input from the negative power supply line 17 to the control circuit 14a via the resistor R, and the polarity is inverted by the amplifier 45, and then the output feedback control circuit 15 And the non-inverting input terminal of the comparator 25. In FIG. 4, a current-voltage conversion resistor is specifically shown as the current detection circuit B, and the terminal voltage is similarly input to the output feedback control circuit 15 after the polarity is inverted by the amplifier 46. And input to the non-inverting input terminal of the comparator 26. The amplifiers 45 and 46 may be omitted by setting the reference voltages I _ZC and V _EF to negative voltages having the same absolute value and reversing the input logic of the comparators 25 and 26.

  Further, in this discharge lamp lighting device 40, the PWM signal generation circuit 16a shows a more specific example, which is a current mode type, a flip-flop composed of two comparators 31, 32, an OR gate 33, and an RS flip-flop. And an off-time upper limit timer 35. The voltages corresponding to the detection results of the primary current I1 and the secondary current I2 of the transformer T are input to the inverting input terminal of the comparator 31 and the non-inverting input terminal of the comparator 32, respectively. A PWM duty adjustment signal from the output feedback control circuit 15 is input to the inverting input terminal, and a predetermined reference voltage Vriz is input to the inverting input terminal of the comparator 32.

  Therefore, when the switching element Q0 of the DC-DC conversion circuit 11a of the main circuit is on, when the switching current I1 is detected and the signal reaches a value corresponding to the PWM duty adjustment signal, the comparator 31 switches the flip-flop 34. The switching element Q 0 is turned off from the flip-flop 34 through the AND gate 24. On the other hand, when the switching element Q0 is turned on, after the switching element Q0 is turned off, the discharge of the energy stored in the transformer T to the load side is completed, and the voltage corresponding to the secondary current I2 is the reference voltage Vriz. It is driven in a so-called current boundary mode, which is performed by the comparator 32 determining that the following has occurred and setting the flip-flop 34. However, in order to prevent an excessive decrease in the switching frequency, the flip-flop 34 is forcibly set by the off-time upper limit timer 35 when the off-time is long.

Furthermore, in the discharge lamp lighting device 40, feedback control is performed by the output feedback control circuit 15, and even in the case of a ground fault, if the output current Iout is reduced, the output is increased, so the output feedback control circuit 15 the switch 41 between the non-inverting input of the comparator 31 is provided with, the current of the current hereinafter corresponding to the reference voltage I _ZC in the comparator 26 that flows is detected, the output feedback The control circuit 15 is disconnected, and a voltage V _NL corresponding to a predetermined fixed duty is applied to the PWM signal generation circuit 16a. The amplifier 46, the comparator 26 and the switch 41 constitute a duty fixed circuit.

Normally, even when there is no load, feedback by the output current Iout is not possible, so the voltage V _NL is set to the level of the PWM duty adjustment signal when the no-load voltage rises. In the discharge lamp lighting device 40, as described above, the PWM signal generation circuit 16a is a current mode type, and the voltage V _NL is an off-timing current value of the switching element Q0 during no-load operation, but the input voltage Vin It may be adjusted by, for example. When the PWM signal generation circuit is a switch mode type, the voltage V _NL may correspond to a predetermined duty or cycle during no-load operation.

As a result, even if a closed circuit is formed so that the output current Iout is not detected in the case of a ground fault as described above, the output feedback control circuit 15 further increases the output with respect to the output current Iout that is no longer detected. Even when trying to do so, the level of the PWM duty adjustment signal is fixed to the voltage V _NL corresponding to the predetermined fixed duty by switching the switch 41 with the output of the comparator 26 that detects the decrease in the output current Iout. As a result, the ON time of the switching element Q0, and hence the current I1 flowing through the switching element Q0, is suppressed, and such a problem can be prevented.

Further, in the discharge lamp lighting device 40, when the comparator 26 detects that the output current Iout is less than or equal to the value corresponding to the reference voltage _IZC , the comparator 26 is in a state until the state is released. Is supplied as an alternating stop signal to the low-frequency drive signal generation circuit 19a, whereby the polarity inversion operation of the inverter circuit 12a is stopped. Therefore, when a ground fault is detected, the polarity of the inverter circuit 12a can be fixed to the polarity through which the ground fault current flows, and reliable ground fault determination can be performed.

[Embodiment 3]
FIG. 5 is a flowchart for explaining the operation of the control circuit in the discharge lamp lighting device according to the third embodiment of the present invention. In the discharge lamp lighting devices 10 and 40 shown in FIGS. 1 and 4 described above, the control circuits 14 and 14a realize the protection control operation by hardware. In this embodiment, a microcomputer or the like is used for the control circuit. Explains the operation when there is. Each detection signal is converted into a digital signal by an analog / digital converter and input to the control circuit. Normally, control by a microcomputer or the like is performed by looping and repeating a series of processing routines, and this embodiment can be realized by incorporating this processing into the control software loop.

First, in step S1, it is determined whether or not the output current Iout is equal to or less than the current corresponding to the reference voltage _IZC . If so, it is determined that the discharge lamp La is extinguished and is in a no-load state or is grounded. In step S2, the PWM duty adjustment signal is switched to a predetermined level. In step S3, the inversion operation of the inverter circuit 12 is stopped.

Thereafter, the output voltage Vout is determined whether the reference voltage V _EF or more in step S4, is less than the reference voltage V _EF, to operate the timers considering a rise time of no-load voltage in step S5, in step S6 If the timer value does not exceed the predetermined value T _NLR , the operation is continued in step S7. If it exceeds, the operation is shifted to the operation prohibited state, and the operation prohibited state is maintained until a system reset is generated due to power-off or the like.

If the output current Iout exceeds the current corresponding to the reference voltage _IZC in step S1, the PWM duty adjustment signal is switched to the food back control level in step S11, and the polarity inversion operation of the inverter circuit 12 is performed in step S12. In step S13, the no-load determination timer is cleared and stopped. Furthermore, in the above steps S1 S4, the output current Iout current below corresponding to the reference voltage I _ZC, and determines the output voltage Vout is the no-load state if the reference voltage V _EF above, no load processing operation I leave it to you.

  The above processing flow enables the ground fault determination operation and the protection operation similar to those of the discharge lamp lighting devices 10 and 40 described above, but the processing flow is not limited to that of FIG. Anything is possible as long as it realizes. Further, the present invention is not limited to the specified circuit, and other configurations may be employed as long as the concept is realized. Furthermore, the same control may be realized by a numerical calculation function by a microcomputer or the like.

1 is a block diagram showing an electrical configuration of a discharge lamp lighting device according to a first embodiment of the present invention. It is sectional drawing which shows the structure of a lighting fixture provided with the discharge lamp lighting device shown in FIG. It is a perspective view which shows the example of attachment to the vehicle of the lighting fixture shown in FIG. It is a block diagram which shows the electric constitution of the discharge lamp lighting device which concerns on the 2nd Embodiment of this invention. It is a flowchart for demonstrating operation | movement of the control circuit in the discharge lamp lighting device which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the electric constitution of the typical discharge lamp lighting device of a prior art.

10, 40 Discharge lamp lighting device 11, 11a DC-DC conversion circuit 12, 12a Inverter circuit 13 Start circuit 14, 14a Control circuit 15 Output feedback control circuit 16, 16a PWM signal generation circuit 17, 18 Power line 19, 19a Low frequency Drive signal generation circuit 20 Drive circuit 21 Ground fault determination circuit 22 Timer circuit 23 Flip flops 24 and 29 AND gates 25 and 26 Comparator 27 NOR gate 28 Oscillator 30 Counter 31 and 32 Comparator 33 OR gate 34 Flip flop 35 Off time upper limit Timer 41 Switch 45, 46 Amplifier 101 Lighting device 102 Lamp housing 103 Lamp socket 104 Reflector 105 Lamp lens 109 Vehicle C Smoothing capacitor D, Da Diode E DC power supply La Discharge lamp Q0; Q1-Q4 Switching element T transformer

Claims (4)

A power conversion circuit that generates a desired DC voltage, an inverter circuit that generates an alternating voltage by switching the output voltage and applies it to a discharge lamp, and feedback control so that the output voltage of the power conversion circuit becomes the desired DC voltage In a discharge lamp lighting device configured to include an output feedback control circuit that performs, and a PWM signal generation circuit that controls switching of the power conversion circuit in response to a PWM duty adjustment signal from the output feedback control circuit ,
The power conversion circuit and the inverter circuit are grounded on the power conversion circuit side, and are inserted into a ground-side power line between the power conversion circuit and the inverter circuit, and
A voltage detection circuit for detecting an output voltage of the power conversion circuit;
The detection result of the current detection circuit is equal to or lower than a predetermined first value at which the lighting of the discharge lamp cannot be maintained , and the detection result of the voltage detection circuit is higher than the upper limit of the lighting voltage of the discharge lamp, A ground fault determination circuit that determines that the output terminal is in a ground fault state when the output end is equal to or lower than a predetermined second value lower than the no-load state in which the light is extinguished ,
A duty fixing circuit that fixes the level of the PWM duty adjustment signal to the level of the PWM duty adjustment signal when the no-load voltage rises when the detection result of the current detection circuit is equal to or lower than the first predetermined value. A discharge lamp lighting device characterized by.   The discharge lamp lighting device according to claim 1, further comprising a timer circuit that stops the operation of the power conversion circuit when a ground fault determination result by the ground fault determination circuit continues for a predetermined time. 2. The ground fault determination circuit according to claim 1, wherein when the detection result of the current detection circuit is equal to or less than a predetermined first value, the ground fault determination circuit gives an alternating stop signal to the inverter circuit to stop the polarity inversion operation. Or the discharge lamp lighting device of 2. The discharge lamp lighting device according to any one of claims 1 to 3 , a housing for housing the discharge lamp lighting device, and a socket for connecting to the discharge lamp lighting device. Lighting equipment to do.

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