JPH11329767A - Discharge lamp device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a fail-safe operation without causing malfunction when the electric wiring part of a lamp comes into an earth fault condition. SOLUTION: In this discharge lamp device, when earth fault condition is determined based on a signal from a lamp voltage detection circuit 601 at the time a lamp voltage VL is not more than a predetermined voltage and a signal from a lamp current detection circuit 602 at the time a lamp current IL is not more than a predetermined current, a high level signal is output from a monostable circuit 605 for a certain period, an H bridge circuit is turned off by an H bridge circuit turning-off circuit 401 to stop the power feeding to a lamp, and high-voltage generation to turn on the lamp again is prevented, and thereafter, when a certain period has elapsed, the H bridge circuit is actuated again and the lamp is lit again. Then, an earth fault condition is determined again, the aforementioned operation is repeated, and if the repeating state has continued for a predetermined period, the H bridge circuit is turned off and this condition is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp device for lighting a high-pressure discharge lamp, and is particularly suitable for use in a vehicle headlamp.

[0002]

2. Description of the Related Art Conventionally, a high-pressure discharge lamp (hereinafter, referred to as a lamp) is applied to a vehicle headlamp, the voltage of a vehicle-mounted battery is increased by a transformer, and the polarity of the high voltage is determined by an inverter circuit. There have been proposed various lamps for switching the lamp so that the lamp is turned on by alternating current (JP-A-9-180).
888, JP-A-8-321389, etc.).

[0003]

This type of lamp is usually mounted in a reflector provided at the front of the vehicle. However, if the electric wiring of the lamp is grounded for some reason, an overcurrent occurs. This causes a problem that the fuse is blown or the circuit element in the discharge lamp device is broken.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to perform fail-safe operation without occurrence of a malfunction when an electric wiring portion of a lamp is grounded.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, a transformer (4
A voltage between the inverter circuit (1) and the inverter circuit (6) is equal to or lower than a predetermined voltage, and a DC voltage source (1) is supplied from the inverter circuit (6).
The ground fault state is determined when the current flowing to the negative electrode side of the inverter is less than or equal to a predetermined current.
, All the switching elements (61a to 61d) are turned off to stop the power supply to the discharge lamp (2),
Thereafter, power supply by the plurality of switching elements (61a to 61d) is started.

When the ground fault state is determined again by the start of the power supply, the above-described stop and start of the power supply are repeated. Then, when the repetition continues for a predetermined period, all the plurality of switching elements (61a to 61d) are kept in an off state. Thus, a fail-safe operation at the time of a ground fault can be performed. In this case, since the fail-safe operation is performed on condition that the stop and start of the power supply continue for a predetermined period, malfunction can be prevented.

The plurality of switching elements (6) in the inverter circuit (6) are temporarily determined by the determination of the ground fault state.
When turning off 1a to 61d), it is preferable to prohibit the lighting start operation of the start circuit (7) as in the second aspect of the present invention. According to the third aspect of the present invention, when all of the plurality of switching elements (61a to 61d) are kept off, the transformer (41)
Switching element (42) connected to the temporary side of
Is kept off. As a result, it is possible to reliably prevent an excessive current from flowing to the primary side of the transformer (41).

It is to be noted that the determination period for stopping and starting the power supply in the ground fault state can be a predetermined time or a predetermined number of times as in the invention according to claim 4, and the invention according to claim 5 The predetermined time or the predetermined number of times, whichever is earlier, can be used. In the invention according to claim 6, when it is determined that the electric wiring between the inverter circuit (6) and the discharge lamp (2) is grounded, the power supply is temporarily stopped. Power supply is started, and when the stop and start of the power supply based on the ground fault determination continue for a predetermined period, the power supply is kept stopped.

In this invention, the same effects as those of the first aspect can be obtained. Further, as in the invention according to claim 7, when the stop and start of the power supply based on the ground fault determination continue for the first predetermined time, all the plurality of switching elements (61a to 61d) are turned off. Hold and the second abnormality other than the ground fault is longer than the first predetermined time.
When a predetermined time has elapsed, a plurality of switching elements (6
By keeping all of 1a to 61d) in an off state, fail-safe operation can be performed immediately at the time of ground fault, and a longer judgment time for other abnormality judgments to prevent malfunction. Can be.

[0010] The reference numerals in parentheses above indicate the correspondence with specific means described in the embodiment described later.

[0011]

(First Embodiment) FIG. 1 shows an overall configuration of an embodiment in which a discharge lamp device according to the present invention is applied to a vehicle headlamp. Reference numeral 1 denotes an in-vehicle battery as a DC power supply, 2 denotes a lamp such as a metal halide lamp as a vehicle headlight, and 3 denotes a lighting switch of the lamp 2.

The discharge lamp device has a DC power supply circuit (DC / DC
It has circuit functional parts such as a converter 4, a takeover circuit 5, an inverter circuit 6, and a starting circuit 7. DC /
The DC converter 4 includes a flyback transformer 41 having a primary winding 41a arranged on the battery 1 side and a secondary winding 41b arranged on the lamp 2 side, a MOS transistor 42 connected to the primary winding 41a, It is composed of a rectifying diode 43 and a smoothing capacitor 44 connected to the secondary winding 41b, and outputs a boosted voltage obtained by boosting the battery voltage VB. That is, when the MOS transistor 42 is turned on, a primary current flows through the primary winding 41a and energy is stored in the primary winding 41a.
When 2 is turned off, the energy of the primary winding 41a is supplied to the secondary winding 41b. By repeating such an operation, the diode 43 and the smoothing capacitor 4
A high voltage is output from the connection point No. 4.

The flyback transformer 41 is configured such that the primary winding 41a and the secondary winding 41b are electrically connected as shown in FIG. The takeover circuit 5 is composed of a capacitor 51 and a resistor 52. The capacitor 51 is charged after the lighting switch 3 is turned on, so that the lamp 2 is quickly shifted from arc breakdown between the electrodes to arc discharge.

The inverter circuit 6 illuminates the lamp 2 with alternating current, and comprises an H-bridge circuit 61 and bridge drive circuits 62 and 63. H bridge circuit 61
Are composed of MOS transistors 61a to 61d serving as bridge semiconductor switching elements arranged in an H-bridge shape. The bridge drive circuits 62 and 63 are controlled by a control signal from an H-bridge control circuit
Transistors 61a and 61d and MOS transistor 61
b and 61c are alternately turned on and off. As a result, the direction of the discharge current of the lamp 2 is alternately switched, the polarity of the applied voltage (discharge voltage) of the lamp 2 is inverted, and the lamp 2 is turned on by AC.

The capacitors 61e and 61f are protection capacitors for protecting the H-bridge circuit 61 from high-voltage pulses generated at the start of lighting. The starting circuit 7 is H
A transformer 71 having a primary winding 71a and a secondary winding 71b, diodes 72 and 73, and a resistor 7 are provided between the midpoint potential point of the bridge circuit 61 and the negative terminal of the battery 1.
4, a capacitor 75, and a thyristor 76, which is a one-way semiconductor element, for starting the lighting of the lamp 2. That is, when the lighting switch 3 is turned on, the capacitor 75 starts charging, and thereafter, the thyristor 76
Turns on, the capacitor 75 starts discharging, and applies a high voltage to the lamp 2 through the transformer 71. As a result, the lamp 2 is lit by dielectric breakdown between the electrodes.

The MOS transistor 42, the bridge circuits 62 and 63, and the thyristor 76 are controlled by the control circuit 10. The control circuit 10 includes a DC-DC
A lamp voltage VL between the converter 4 and the inverter circuit 6 (that is, a voltage applied to the inverter circuit 6), a lamp current IL flowing from the inverter circuit 6 to the negative electrode side of the battery 1, and the like are input. Note that the lamp current I
L is detected as a voltage by the current detection resistor 8.

FIG. 2 shows a block configuration of the control circuit 10. The control circuit 10 sets the MOS transistor 42 to PWM
A PWM control circuit 100 that is turned on and off by a signal;
A sample and hold circuit 200 for sampling and holding the lamp voltage VL;
A lamp power control circuit 300 for controlling the lamp power to a desired value based on L and the lamp current IL, an H-bridge control circuit 400 for controlling the H-bridge circuit 61, and a thyristor 76 turned on to generate a high voltage in the lamp 2 High-voltage generation control circuit 500 and electric wiring portions 2 on both sides of lamp 2
It comprises a fail-safe circuit 600 that detects an abnormal state such as when a ground fault occurs at 0 and performs a coping process.

In the above configuration, the lighting operation of the discharge lamp device will be described. When the lighting switch 3 is turned on, power is supplied to each unit shown in FIG. Then, the PWM control circuit 10
0 performs PWM control on the MOS transistor 42. As a result, a voltage obtained by boosting the battery voltage VB by the operation of the flyback transformer 41 is output from the DC-DC converter 4. Also, the H-bridge control circuit 400
MOS transistors 61a-61 in the bridge circuit 61
61d is turned on and off alternately in a diagonal relationship. As a result, the high voltage output from the DC-DC converter 4 is supplied to the capacitor 75 of the starting circuit 7 via the H-bridge circuit 61, and the capacitor 75 is charged.

Thereafter, the high voltage generation control circuit 500
A gate drive signal is output to thyristor 76 based on a signal output from bridge control circuit 400 to notify the switching timing of MOS transistors 61a to 61d, and thyristor 76 is turned on. When the thyristor 76 is turned on, the capacitor 75 is discharged, and a high voltage is applied to the lamp 2 through the transformer 71. As a result, the lamp 2 is broken down between the electrodes, and the lighting is started.

Thereafter, the polarity of the discharge voltage to the lamp 2 (direction of the discharge current) is alternately switched by the H-bridge circuit 61, so that the lamp 2 is turned on by AC. Further, the lamp power control circuit 300 controls the lamp power to a desired value based on the lamp current IL and the lamp voltage VL (sampled and held by the sample and hold circuit 200), and stably turns on the lamp 2. Let it.

Note that the sample and hold circuit 200
In synchronization with the switching timing of the bridge circuit 61, the transient voltage generated at the time of the switching is masked, and the ramp voltage VL other than when the transient voltage is generated is sampled and held. Next, the above-described bridge drive circuits 62 and 63 will be described. FIG. 3 shows the specific configuration.

The bridge drive circuits 62 and 63 have the same configuration, and have a high and low driver circuit (Inter).
National Rectifier, IR21
01). Then, the bridge driving circuit 62
The H-bridge control circuit 400 is connected to the high-voltage input terminal Hin of the
Is input from the terminal 400a of the bridge drive circuit 62 to the low-voltage-side input terminal Lin of the bridge drive circuit 62.
The signal from the terminal 400b of the H-bridge control circuit 400 is input to the third high-voltage input terminal Hin. Then, the terminals 400a, 400 of the H-bridge control circuit 400
The signal from b is inverted between high level and low level.

In such a configuration, when a high-level signal is output from the terminal 400a of the H-bridge control circuit 400 and a low-level signal is output from the terminal 400b,
By the output signals from the bridge drive circuits 62 and 63,
The MOS transistors 61a and 61d are turned on, and the MOS transistors 61b and 61c are turned off. When a low-level signal is output from the terminal 400a of the H-bridge control circuit 400 and a high-level signal is output from the terminal 400b, the MOS transistors 61b and 61c are turned on by the output signals from the bridge drive circuits 62 and 63, MO
The S transistors 61a and 61d are turned off.

The bridge driving circuits 62 and 63 include:
A voltage is supplied from the secondary side of the flyback transformer 41. That is, on the secondary side of the flyback transformer 29, the resistor 64a and the Zener diode 6
4b, the first power supply circuit 64 is provided.
The predetermined voltage V2 generated by the power supply circuit 64 (for example, 15
V) is supplied to the bridge drive circuits 62 and 63. In addition to the voltage on the secondary side of the transformer 41, the voltage on the primary side (battery voltage VB) via the diode 65, the resistor 66, and the capacitor 67 for removing noise can be supplied to the bridge drive circuits 62 and 63. It has become.

A fail-safe circuit 600 described later
, A low-level signal is applied to all of the input terminals Hin and Lin of the bridge drive circuits 62 and 63, and all four MOS transistors 61a to 61d in the H bridge circuit 61 are turned off (hereinafter, this state is referred to as H
An H-bridge off circuit 401 for turning off the bridge circuit 61) is provided.

Next, the lamp power control circuit 30
0 will be described. FIG. 4 shows the specific configuration.
The lamp power control circuit 300 includes an error amplifier circuit 301 that generates an output according to a lamp voltage VL, a lamp current IL, or the like, which is a signal indicating a lighting state of the lamp 2,
The output of the error amplification circuit 301 is the PWM control circuit 100
To be entered. PWM control circuit 100
Is, as the output voltage of the error amplifier circuit 301 increases,
The duty ratio for turning on / off the MOS transistor 42 is increased to increase the lamp power.

The reference voltage Vr1 is input to the non-inverting input terminal of the error amplifier circuit 301, and the voltage V1 as a parameter for controlling the lamp power is input to the inverting input terminal. Is the reference voltage Vr1
And a voltage corresponding to the difference between the voltage and the voltage V1. This voltage V1
Is determined based on the lamp current IL, the constant current i1, the current i2 set by the first current setting circuit 302, and the current i3 set by the second current setting circuit 303. The sum of the current i1, the current i2, and the current i3 is set sufficiently smaller than the lamp current IL.

Here, the first current setting circuit 302 sets the current i2 higher as the lamp voltage VL increases as shown in the figure, and the second current setting circuit 303 turns on the lighting switch 3 as shown in the figure. The current i3 is set to be larger as the later time T becomes longer. The lamp power control circuit 300 controls the lamp power by outputting a voltage corresponding to the time T after the lighting switch 3 is turned on, the lamp voltage VL, the lamp current IL, and the like. (For example, 75 W) to quickly raise the electrode temperature,
When the electrode temperature gradually increases, the lamp power is gradually reduced, and when the lamp 2 is in a stable state, the lamp power is controlled to a predetermined value (for example, 35 W).

Next, the PWM control circuit 100 will be described. FIG. 5 shows a specific configuration thereof. The PWM control circuit 100 includes a threshold level setting circuit 101 for setting a threshold level, a sawtooth wave forming circuit 102 for forming a sawtooth wave, and a duty cycle corresponding to the threshold level by comparing the sawtooth wave with the threshold level. A comparator 103 for outputting a gate signal having a ratio, an output from the comparator 13 and a fail-safe circuit 600
That receives the output from the inverter through the inverter 104 as an input
It comprises a gate 105.

The threshold level setting circuit 101
In response to the output voltage (command signal) from the above-described error amplifier circuit 301, the lower the threshold voltage is set as the output voltage increases. Therefore, when the output voltage of the error amplifier circuit 301 increases to increase the lamp power, the threshold level decreases and the duty ratio increases. Further, when the output voltage of the error amplifier circuit 301 decreases to reduce the lamp power, the threshold level increases and the duty ratio decreases.

When the fail-safe circuit 600 outputs a high-level signal indicating the detection of the ground fault condition of the lamp 2, the inverter 104 outputs a low-level signal, so that the output of the AND gate 105 becomes low. , The MOS transistor 42 is turned off. Therefore, when the lamp 2 is in the ground fault state, the operation of the DC-DC converter 4 is stopped.

Next, the fail safe circuit 600 will be described. FIG. 6 shows the specific configuration. The fail safe circuit 600 includes a lamp voltage detection circuit 601, a lamp current detection circuit 602, an AND gate 603, a filter 604, a monostable circuit 605, and a NOR gate 606.
, A filter 607, an OR gate 608, a timer circuit 609, and a D flip-flop 610.

The ramp voltage detection circuit 601 is configured to output the ramp voltage VL from the sample hold circuit 200 and a predetermined voltage Vr.
2 (for example, 20 V)
And outputs a high-level signal (voltage drop signal) when the lamp voltage VL is equal to or lower than the predetermined voltage Vr2. The lamp current detection circuit 602 includes a comparator 602a, a capacitor 602b, and a resistor 602c. The comparator 602a compares the voltage VIL according to the lamp current IL with the predetermined voltage Vr3, and when the voltage VIL is equal to or lower than the predetermined voltage Vr3, that is, when the lamp current IL is equal to or lower than the predetermined current (for example, 0.2 A). Outputs a level signal (current drop signal).

Here, when the power of the lamp 2 is controlled, the lamp voltage VL is in the range of, for example, 20 V to 400 V, and the lamp current IL is, for example, 0.35 to 2.
6A, both the lamp voltage detection circuit 601 and the lamp current detection circuit 602 output a low level signal. However, if the electric wiring section at both ends of the lamp 2, that is, the electric wiring section 20 between the inverter circuit 6 and the lamp 2 is grounded, an overcurrent flows to the secondary side of the flyback transformer 41 and the lamp voltage VL becomes It becomes lower than 20V. The overcurrent from the secondary winding 41b drops from the electric wiring section 20 to the ground, and the lamp current IL becomes 0.2 A or less. As a result, both the lamp voltage detection circuit 601 and the lamp current detection circuit 602 output a high level signal,
The output of the ND gate 603 becomes a high level signal indicating a ground fault state.

When both ends of the lamp 2 are short-circuited, the lamp voltage VL becomes lower than the predetermined voltage Vr2, but the lamp current IL becomes larger than the predetermined current. When the lamp 2 is disconnected, the lamp current IL becomes smaller than the predetermined current, but the lamp voltage VL becomes the predetermined voltage Vr.
Greater than 2. Therefore, by comparing both the lamp voltage VL and the lamp current IL with predetermined values,
The ground fault state of the electric wiring unit 20 can be distinguished from the short-circuit or disconnection state of the lamp 2.

Next, the operation after the above-described ground fault occurs will be described. FIG. 7 shows the signal waveform of each part in FIG. 6 in this case. Output signal a of AND gate 603
Becomes a high level signal indicating a ground fault condition, the filter 6
The output signal b at 04 also goes high. Then, the output signal c of the monostable circuit 605 is kept for a certain time (for example, 10 ms).
The high level signal is output to the H bridge off circuit 401 and the high voltage control circuit 500.

The H-bridge off circuit 401 receives the high-level signal from the monostable circuit 605,
Turn 1 off. As a result, an overcurrent due to a ground fault in the electric wiring section 20 is caused by the MOS transistors 61a and 61c.
Will be cut off. Further, the high voltage control circuit 500 operates so as not to output a gate drive signal to the thyristor 76 by a high level signal from the monostable circuit 605. FIG. 8 shows the configuration of the high voltage control circuit 500. The high-voltage control circuit 500 includes the H-bridge control circuit 40
A signal generation circuit 501 that outputs a gate drive signal to the thyristor 76 based on an output signal from 0 is provided. Then, when a high-level signal is output from the monostable circuit 605, the output of the inverter 502 becomes low and A
Since the ND gate 503 is closed, the ON of the thyristor 76 is prohibited. That is, generation of a high voltage for lighting the lamp 2 is prohibited.

When the lamp voltage VL rises due to the turning off of the H-bridge circuit 61, the lamp voltage detecting circuit 6
Since the output signal of the AND gate 603 goes low, the output signal of the AND gate 603 goes low. Thereafter, when the output signal c of the monostable circuit 605 goes low, the H-bridge control circuit 400
The on / off driving of 1d is started, and power supply to the lamp 2 is started. At this time, if the grounding state of the electric wiring unit 20 continues, the output signal of the lamp voltage detection circuit 601 becomes high level again, and the output signal a of the AND gate 603 is output.
Also goes high again. As a result, the monostable circuit 605
Outputs a high-level signal for a certain period of time, turning off the H-bridge circuit 61 and inhibiting the thyristor 76 from being turned on.

Thereafter, the above operation is repeated while the ground fault state of the electric wiring section 20 continues. Further, when the high level signal is output from the lamp current detection circuit 602, the output signal of the NOR gate 606 becomes low level, and the output signal e of the filter 607 also becomes low level. Then, since the output signal of the OR gate 608 becomes low level, the reset of the timer circuit 609 is released, and the timer circuit 609 starts the time counting operation. Thereafter, when a predetermined time (for example, 0.2 seconds) elapses and the output signal f of the timer circuit 609 becomes a high level, the Q terminal output signal g of the D flip-flop 610 becomes a high level using this as a clock.

The high-level signal from the D flip-flop 610 causes the H-bridge off circuit 401 to output a high-level signal.
The bridge circuit 61 is turned off, and the PWM control circuit 100
The MOS transistor 42 is turned off. That is, PWM
In the control circuit 100, when a high-level signal is output from the D flip-flop 610, the output of the inverter 104 shown in FIG.
Since the output of No. 5 becomes low level, the MOS transistor 42 is turned off. Therefore, the operation of the DC-DC converter 4 stops.

This makes it possible to prevent the primary current from becoming excessive. That is, when the MOS transistor 42 is not turned off, for example, when the electric wiring unit 20 is grounded and a predetermined contact resistance is present in that portion, the power on the secondary side of the flyback transformer 41 is greatly consumed by the contact resistance. Then, by the operation of the lamp power control circuit 300, the on / off control of the MOS transistor 42 is performed so as to increase the energy stored in the primary winding 41a.
Therefore, the primary winding 41a of the flyback transformer 41
However, as described above, the MOS transistor 42 is turned off and the DC-D
By stopping the operation of the C converter 4, it is possible to prevent an excessive current from flowing through the primary winding 41a of the flyback transformer 41.

As described above, in this embodiment, when the lamp voltage VL is equal to or lower than the predetermined voltage and the lamp current IL is equal to or lower than the predetermined current, it is determined that the ground fault has occurred.
By this determination, the H-bridge circuit 61 is temporarily turned off (for a certain period of time) and a high voltage for turning on the H-bridge circuit 61 again is not generated.
The H-bridge circuit 61 is operated again, and the re-lighting operation is performed. If the ground fault state is determined again in this operation, the above operation is repeated, and when this repeated state continues for a predetermined time, the operation of the DC-DC converter 4 is stopped and this state is maintained.

As described above, the lamp voltage VL and the lamp current I
When the ground fault state is determined based on L, the H-bridge circuit 61 is repeatedly stopped and started, and the fail-safe is performed when the repetition continues for a predetermined time. Erroneous operation can be prevented as compared with the case where the fail-safe operation is immediately performed based on the determination.

In the fail-safe circuit 600, not only the above-described fail-safe at the time of a ground fault, but also the fail-safe for other abnormality detection (for example, detection of disconnection of the connector of the lamp 2 not shown). I'm trying to do it. In this case, the abnormality detection signal (a signal that goes high when an abnormality is detected) is input to the NOR gate 606. If the abnormality detection signal continues to be generated while the timer circuit 609 counts for a predetermined time, a high-level signal is output from the D flip-flop 610.
The bridge circuit 61 is turned off, and the MOS transistor 42 is turned off. (Second Embodiment) In the first embodiment, the time counted by the timer circuit 609, that is, the abnormality determination time is calculated as follows.
It is the same when a ground fault is detected and when another abnormality is detected. It is preferable that the abnormality determination time is long from the viewpoint of preventing a malfunction in detecting abnormality, but it is preferable to perform the fail-safe as soon as possible at the time of a ground fault.

Therefore, in this embodiment, the abnormality determination time at the time of detecting a ground fault is set shorter than at the time of detecting another abnormality. FIG. 9 shows a configuration of the fail-safe circuit 600 according to this embodiment, and FIG. 10 shows signal waveforms at various parts in FIG. OR by ground fault detection or other abnormality detection
When the signal from the circuit 608 becomes low level, the reset of the timer circuit 609 is released and the timer circuit 609 starts the time counting operation. The timer circuit 609 sets the output signal h to a high level when counting a first predetermined time (eg, 0.2 seconds), and sets the output signal i to a high level when counting a second predetermined time (eg, 0.4 seconds). To

When a ground fault is detected, the timer circuit 60
9 and the output signal c from the monostable circuit 605, when both output signals go high, the output signal j of the AND gate 611 goes high and the D flip-flop 610 via the OR gate 612. , A high-level signal is input to the clock terminal of the D flip-flop 610, so that the Q-terminal output signal 1 of the D flip-flop 610 goes high.
Therefore, in the case of ground fault detection, the fail-safe operation is performed with the abnormality determination time as the first predetermined time.

In the case of another abnormality detection, the Q terminal output signal 1 of the D flip-flop 610 goes high when the output signal i from the timer circuit 609 goes high. Therefore, in the case of another abnormality detection, the fail-safe operation is performed using the second abnormality determination time longer than that in the case of the ground fault detection. (Third Embodiment) In the first and second embodiments,
Although the fail-safe operation is performed when the stop and the start of the operation of the H-bridge circuit 61 continue for a predetermined time, the fail-safe operation is performed by using the number of times of the stop and the start of the H-bridge circuit 61. Is also good.

FIG. 11 shows the configuration of the fail-safe circuit 600 according to this embodiment, and FIG. 12 shows the signal waveforms at various points in FIG. In this embodiment, the H-bridge circuit 61 based on the output signal c of the monostable circuit 605
Counter circuit 613 for counting the number of times of stop and start
Is provided. Then, when the count value reaches a predetermined number (for example, five times), the counter 613 sets the output signal m to a high level. Thus, a high-level signal is input to the clock terminal of the D flip-flop 610 via the OR gate 614, so that a fail-safe operation is performed as in the first and second embodiments.

Further, in this embodiment, similarly to the first embodiment, the fail-safe operation is also performed by the signal o when a predetermined time has elapsed from the timer circuit 609. Therefore, in this embodiment, the fail-safe operation is performed at the earlier timing of stopping or starting the H-bridge circuit 61 a predetermined number of times or counting time of the timer circuit 609 reaching a predetermined time. .

In this embodiment, the fail-safe operation may be performed only when the number of times the H-bridge circuit 61 stops and starts reaches a predetermined number.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a discharge lamp device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a control circuit 10 in FIG. 1;

FIG. 3 is a diagram showing a specific configuration of bridge drive circuits 62 and 63 in FIG. 1;

FIG. 4 is a diagram showing a specific configuration of a lamp power control circuit 300 in FIG. 2;

FIG. 5 is a diagram showing a specific configuration of a PWM control circuit 100 in FIG. 2;

FIG. 6 is a diagram showing a specific configuration of a fail-safe circuit 600 in FIG. 2;

FIG. 7 is a diagram showing signal waveforms of respective units in FIG.

8 is a diagram showing a configuration of a high voltage generation circuit 500 in FIG.

FIG. 9 is a diagram illustrating a specific configuration of a fail-safe circuit 600 according to a second embodiment of the present invention.

FIG. 10 is a diagram showing signal waveforms at various parts in FIG. 9;

FIG. 11 is a diagram showing a specific configuration of a fail-safe circuit 600 according to a third embodiment of the present invention.

FIG. 12 is a diagram showing signal waveforms at various parts in FIG. 11;

[Explanation of symbols]

1: Vehicle battery, 2: Lamp, 3: Lamp, 4: DC
DC converter, 5: takeover circuit, 6: inverter circuit, 7: starting circuit, 41: flyback transformer, 42: MOS transistor, 61: H bridge circuit, 100: PWM control circuit, 200: sample and hold circuit, 300 ... PWM control circuit, 400 H bridge control circuit, 500 high voltage generation control circuit, 600 fail-safe circuit.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Satoru Oda 500 Kitawaki, Shimizu-shi, Shizuoka Prefecture Inside the Koito Manufacturing Co., Ltd. Shizuoka Plant (72) Inventor Tomoyuki Funayama 1 Toyota Town, Toyota-shi, Aichi Prefecture Toyota Motor Corporation

Claims (7)

[Claims] 1. A transformer (41) for boosting the voltage of a DC voltage source (1) and a plurality of switching elements (61a to 61d) for converting the boosted voltage to an AC voltage to supply power to a discharge lamp (2). And a voltage between the transformer (41) and the inverter circuit (6) is equal to or lower than a predetermined voltage, and the inverter circuit (6) supplies a negative voltage to the DC voltage source (1). When it is determined that the current flowing through the plurality of switching elements (61a to 61d) is temporarily turned off to stop the power supply, the plurality of switching elements (61a to 61d) are temporarily turned off. ) Is started, and when the stop and start of the power supply based on the determination continue for a predetermined period, the plurality of switching elements (61)
a discharge lamp device comprising: a fail-safe circuit (600) for keeping all of the a-61d) turned off. 2. The fail-safe circuit (600),
When all of the plurality of switching elements (61a to 61d) are turned off, a lighting start operation of a starting circuit (7) for lighting and starting the discharge lamp (2) is prohibited, and the plurality of switching elements (61a to 61d) are turned off. The discharge lamp device according to claim 1, wherein when the power supply is started, the prohibition of the lighting start operation of the start circuit (7) is released. 3. The transformer (41) is provided on the side of the DC power supply (1), on the primary side to which a boosting switching element (42) for boosting is connected, and on the side of the discharge lamp (2). The fail-safe circuit (600) is configured to be electrically connected to the provided secondary side. When the fail-safe circuit (600) holds all of the plurality of switching elements (61a to 61d) in an off state, , The boosting switching element (4
The discharge lamp device according to claim 1, wherein the discharge lamp device is kept in a state where 2) is turned off. 4. The fail-safe circuit (600)
If the stop and start of the power supply based on the determination continue for a predetermined time or a predetermined number of times, all of the plurality of switching elements (61a to 61d) are held in an off state. Item 4. The discharge lamp device according to any one of Items 1 to 3. 5. The fail safe circuit (600),
When the stop and start of the power supply based on the determination continue for a predetermined time or a predetermined number of times, whichever is earlier, all of the plurality of switching elements (61a to 61d) are maintained in an off state. The discharge lamp device according to any one of claims 1 to 3, wherein: 6. A transformer (41) for boosting the voltage of the DC voltage source (1), and an inverter for converting the voltage boosted by the transformer (41) into an AC voltage to supply power to the discharge lamp (2). When it is determined that the circuit (6) and the electric wiring section (20) between the inverter circuit (6) and the discharge lamp (2) are grounded, the power supply is temporarily stopped. A fail-safe circuit (600) that starts the power supply and holds the power supply in a stopped state when the power supply is stopped and started based on the ground fault determination for a predetermined period. Discharge lamp device characterized by the above-mentioned. 7. The fail safe circuit (600),
Stopping and starting the power supply based on the ground fault determination is the first
When the predetermined time has continued, the plurality of switching elements (61a to 61d) are all kept in an off state, and the abnormality other than the ground fault is longer than the first predetermined time for a second predetermined time. 7. The discharge lamp device according to claim 6, wherein when continuing, the plurality of switching elements (61 a to 61 d) are all kept in an off state. 8.