JP2700934B2 - Lighting circuit for vehicle discharge lamps - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Details of a lighting circuit of a vehicle discharge lamp according to the present invention will be described in accordance with the following items.

A. Industrial application fields B. Summary of the invention C. Background art D. Problems to be solved by the invention E. Means to solve the problems F. Embodiment [FIGS. 1 to 3] a. [Fig.1] b. Circuit configuration of each part [Fig.2, Fig.3] b-1. Power cutoff relay circuit b-2. Relay cutoff circuit b-3. Overvoltage detection circuit b-4. DC booster circuit b-5. High frequency booster circuit b-6. Current limiting load and igniter circuit b-7. Igniter starting circuit b-8. Lighting abnormality detection circuit b-9. Control circuit [Fig.2, Fig.3] b-10. Output current abnormality detection circuit b-11. Output voltage abnormality detection circuit c. Operation c-1. Normal operation c-2. Abnormality c-2-a. Lighting disabled c-2-b. Output current Abnormality c-2-c. Abnormal output voltage c-2-d. Abnormal battery G. Effects of the Invention (A. Industrial Application Field) The present invention relates to a novel lighting circuit for a discharge lamp for a vehicle. More specifically, it is an object of the present invention to provide a novel lighting circuit for a discharge lamp for a vehicle, which can prevent a breakdown of a lamp due to an abnormality of a circuit state, an element failure, and an electric shock accident at the time of lamp replacement. .

(B. Summary of the Invention) A lighting circuit of a vehicular discharge lamp according to the present invention includes a DC booster circuit for boosting a DC voltage from a DC voltage input terminal, and a converter circuit for converting an output voltage of the DC booster circuit to an AC voltage. A lighting circuit for a discharge lamp for a vehicle, wherein the output of the converter circuit is applied to the discharge lamp via a current-limiting load, wherein a power cutoff switch connected in series to the lighting switch between DC voltage input terminals. Means, a relay for permitting power supply to the discharge lamp when the lighting switch and the power cutoff switch means are closed, and a circuit abnormality detecting means for detecting an abnormality in the circuit state of the lighting circuit. The circuit abnormality detecting means detects an abnormal state relating to the output current and voltage of the DC booster circuit, an overvoltage of the DC power supply, and sends a signal to the power cutoff switch means to relay the signal. By operated so as cut off the power supply to the lighting circuit from the DC power source is obtained by so it is possible to prevent and prevent electric shock at the time of lamp replacement of insulation breakdown and circuit elements lamp failure.

(C. Background Art) Currently, incandescent lamps are widely used as light sources for automotive headlamps. For example, a lighting circuit for the incandescent lamp includes a relay coil connected between battery terminals through a lighting switch. A circuit is used in which the lamp is connected and an incandescent lamp is connected between the battery terminals via a relay contact.

In such a lighting circuit of an incandescent light bulb, an abnormality occurs due to the life of the light bulb, an overvoltage is input from the battery, or the polarity of the battery is incorrectly connected to the input terminal of the lighting circuit. Even in such a case, there is no problem in safety because the worst case is to cause the filament to be broken, and no special protection circuit is usually provided for this.

(D. Problems to be Solved by the Invention) By the way, recently, metal halide lamps have been spotlighted as new light sources replacing incandescent lamps including halogen lamps, and these metal halide lamps are used as light sources for headlamps for automobiles. In this case, the lamp needs to be turned on or turned on instantaneously, and the starting voltage at that time is very high (about 10 to 20 kV).

Therefore, after turning on the lighting switch, if an abnormality occurs due to the life of the lamp or the like and the lamp does not turn on, a high voltage will continue to be generated between the output terminals of the lighting circuit. There is a danger that ignition will occur due to insulation breakdown between the contact terminals provided in the socket that is provided, or that the user will be shocked by replacing the lamp without the user knowing that a high voltage is being applied to the lamp. There's a problem.

In addition, if an abnormal condition occurs with respect to the output current or output voltage of the DC booster circuit that forms part of the lighting circuit, or if the battery becomes overvoltage, the destruction of circuit elements and associated circuit malfunctions will be induced, and the occurrence of high voltage and There is a risk of lamp destruction.

(E. Means for Solving the Problems) In order to solve the above-described problems, a lighting circuit for a vehicle discharge lamp according to the present invention includes: a DC boosting circuit for boosting a DC voltage from a DC voltage input terminal; A converter circuit for converting the output voltage of the booster circuit into an AC voltage, and a lighting circuit for a vehicle discharge lamp in which the output of the converter circuit is applied to the discharge lamp via a current-limiting load. And a means for detecting an output current and / or output voltage of the DC booster circuit and an overvoltage state of the DC power supply to detect an abnormality in the circuit state, and the circuit is provided with a circuit. When an abnormality occurs, a signal is sent to the power cutoff switch means to cut off the power supply from the DC power supply to the lighting circuit.

Therefore, according to the present invention, when an abnormality in the output current and / or output voltage of the DC booster circuit is detected, or when an overvoltage of the DC power supply is detected, the lighting circuit using the DC power supply is switched by the power supply cutoff switch means. Since the supply of the power supply voltage to the power supply is cut off, destruction of lamps and circuit elements, electric shock, and the like can be prevented.

(F. Embodiment) [FIGS. 1 to 3] Hereinafter, details of a lighting circuit of a vehicular discharge lamp according to the present invention will be described with reference to an illustrated embodiment. In the illustrated embodiment, the lighting circuit of the vehicle discharge lamp of the present invention is applied to the lighting circuit of a metal halide lamp for an automobile.

(A. Entire Configuration) [FIG. 1] Reference numeral 1 denotes a lighting circuit.

Reference numeral 2 denotes a battery, which is connected between the DC voltage input terminals 3, 3 '.

Reference numerals 4 and 4 'denote DC power supply lines, and a lighting switch 5 is provided on one of the plus lines 4.

Reference numeral 6 denotes a power cut-off relay circuit. When a signal from the relay cut-off circuit 7 is received when the circuit is abnormal, supply of a power supply voltage to a circuit at a subsequent stage is cut off. The relay cutoff circuit 7 receives signals from an overvoltage detection circuit 8 for detecting an overvoltage of the battery 2, an output current abnormality detection circuit, an output voltage abnormality detection circuit, and a lighting abnormality detection circuit, which will be described later. Is turned off.

Reference numeral 9 denotes a DC booster circuit, which is provided downstream of the power cutoff relay circuit 6 and boosts the battery voltage. The boosting control is performed by a control circuit described later.

Reference numeral 10 denotes a high-frequency booster circuit, which is provided after the DC booster circuit 9 and is provided for converting a DC voltage from the DC booster circuit 9 into a sine wave AC voltage. As the high-frequency booster circuit 10, for example, a push-pull type inverter circuit is used.

Reference numeral 11 denotes a current-limiting load and an igniter circuit, which is disposed at a stage subsequent to the high-frequency booster circuit 10 and has AC output terminals 12, 1
A metal halide lamp 13 (about 35 W) is connected between 2 '.

Reference numeral 14 denotes an igniter starting circuit, which detects the lighting or non-lighting of the metal halide lamp 13 based on the lamp current, and is provided to transmit a starting pulse generation signal to the current limiting load and the igniter circuit 11 when the metal halide lamp 13 is not lit. Have been.

The current limiting load and the igniter circuit 11 and the igniter starting circuit 14 are arranged on the same substrate, and the other components are arranged on a separate substrate, and the two substrates are connected by a connection cord with a connector. I have.

Reference numeral 15 denotes a control circuit which controls the output voltage of the DC booster circuit 9 and the output current of the DC booster circuit 9 which are detected via voltage dividing resistors 16 and 16 'provided between the output terminals of the DC booster circuit 9. For conversion, a pulse signal having a duty cycle corresponding to a voltage from a current detecting resistor 17 provided on a ground line connecting the DC boosting circuit 9 and the high-frequency boosting circuit 10 is generated, and this signal is gate-driven. The signal is sent to the DC booster circuit 9 via the circuit 18 and is provided for controlling the output voltage. The control circuit 15 and the battery 2 are connected to a common ground.

19 is an output current abnormality detection circuit, which is a high-frequency booster circuit 10
When the output stage is short-circuited (for example,
(If the connector of the connection cord connecting the current-limiting load 10 and the igniter circuit 11 comes off and comes into contact with another)
Is provided in order to prevent the output current of the DC booster circuit 9 from becoming excessively large and causing the destruction of the control element and the like. Then, when the output current of the DC booster circuit 9 becomes equal to or more than a predetermined value, it is determined that an abnormality has occurred, and a signal is sent to the relay cutoff circuit 7.

Reference numeral 20 denotes an output voltage abnormality detection circuit, which is used when the metal halide lamp 13 or the AC output terminals 12, 12 'is in a sheet state, or when the output stage of the high-frequency booster circuit 10 is in an open state (for example, a disconnection or a connector). In such a case, the duty cycle of the control pulse generated by the control circuit 15 becomes the maximum, so that the output voltage of the DC boosting circuit 9 becomes the maximum value. If this state continues for a long time, the element is destroyed, or the transformer or the like generates heat or deteriorates. Therefore, if this continues for a predetermined time or more, it is determined that an abnormality has occurred and a signal is sent to the relay interrupting circuit 7.

Reference numeral 21 denotes a lighting abnormality detection circuit, which is an igniter starting circuit 14.
The lighting or non-lighting of the metal halide lamp 13 is determined on the basis of the signal from the controller, and when the lamp does not light up for some reason, a signal is sent to the relay interrupting circuit 7. For example, if the lamp is not connected between the AC output terminals 12 and 12 'or if the lamp cannot be turned on due to the life of the lamp or the like, the starting pulse will continue to be generated. This is to prevent destruction and electromagnetic interference.

(B. Circuit Configuration of Each Unit) [FIGS. 2 and 3] Next, each circuit unit constituting the lighting circuit 1 will be described in detail.

(B-1. Power-off relay circuit) Reference numeral 22 denotes a diode for preventing reverse voltage, the anode of which is connected to the positive line 4. This diode 22
Are provided for protection when the polarity of the battery 2 is erroneously connected to the DC voltage input terminals 3, 3 '.

Reference numeral 23 denotes a relay. One end of a coil 23a is connected to the cathode of the diode 22, and the other end is an NPN for shutting off the relay.
Connected to the collector of transistor 24. This transistor 24 forms part of the circuit 7 for relay cutoff.
If the transistor 24 is on when the lighting switch 5 is turned on, the relay 23 is turned on, the NO (normally open) contact 23b provided on the plus line 4 is closed, and the DC booster circuit thereafter 9 is supplied with a battery voltage. Conversely, when the transistor 24 is turned off, the relay 23 is turned off and the NO contact 23b is opened, so that the supply of the battery voltage is cut off.

Reference numeral 25 denotes a diode provided in anti-parallel to the coil 23a.

26 is a power supply terminal connected to the cathode of the diode 22, and 27 is a power supply line.

(B-2. Relay disconnection circuit) 28 is a power supply terminal, and a diode is provided on the positive line at the subsequent stage of the NO contact 23b so that a predetermined voltage is obtained when the NO contact 23b of the relay 23 is closed. Connected through.

Reference numeral 29 denotes a PNP transistor whose emitter is connected to the power supply terminal 28 and whose collector is connected to the anode of the diode 30. The base is connected to a collector of an NPN transistor provided at an output stage of the output current abnormality detection circuit 19, the output voltage abnormality detection circuit 20, and the lighting abnormality detection circuit 21 via a resistor (101) described later. I have.

Reference numeral 31 denotes a resistor provided between the base and the emitter of the transistor 29.

32 is an NPN transistor whose emitter is grounded,
Its collector is connected to the power supply line 27 via the series resistors 33 and 33 '.
And its base is connected to a diode 30 via a resistor 34.
Connected to the cathode. A resistor 35 is provided between the base and the emitter.

36 is a PNP transistor whose collector is connected to the cathode of the diode 30 and whose emitter is connected to the power supply line 27.
And its base is connected between resistors 33 and 33 '.

37 is a diode whose cathode is a transistor
The collector of the transistor 32 is connected to the base of the transistor 24 via a resistor 38.

39 is a resistor provided between the anode of the diode 37 and the power supply line 27, and 40 is a resistor inserted between the base and the emitter of the transistor 24.

As described above, in the relay interrupting circuit 7, when the transistor 29 is turned on, the on state of the transistors 32 and 36 is maintained, and the transistor 24 is turned off.

The holding of the signal by the transistor 36 is for preventing chattering in the detection of an abnormality. When the non-lighting state of the metal halide lamp 13 continues for a predetermined time or more, or when the output current of the DC booster circuit 9 becomes excessive or the output voltage becomes It is meaningful when the maximum value state continues for a predetermined time or more. By carrying out such signal holding, in the event of a circuit abnormality, it is sufficient to supply power only to the circuit such as the relay cutoff circuit 7 which is fed from the plus line 4 via the diode 22, thereby saving power. .

(B-3. Overvoltage Detection Circuit) Reference numeral 41 denotes a Zener diode, the cathode of which is connected to the power supply terminal 26, and the anode of which is grounded via the series resistors 42 and 42 '.

43 is an NPN transistor whose emitter is grounded,
Its collector is connected between the resistors 38 and 39 of the relay breaking circuit 7, and its base is connected between the resistors 42 and 42 '.

As described above, in the overvoltage detection circuit 8, when the battery voltage exceeds a certain voltage, the Zener diode 41 conducts and the transistor 43 turns on, so that the transistor 24 of the relay cutoff circuit 7 turns off and the relay 23 turns off. Will do.

(B-4. DC Step-Up Circuit) The DC step-up circuit 9 is configured as a chopper-type DC-DC converter, and includes an inductor 44 provided on the plus line 4, and a plus line 4 and a ground line 4 ′ at a subsequent stage. And an N-channel FET 45 that is switched between the control circuit 15 and the control pulse sent from the control circuit 15 via the gate drive circuit 18, and whose anode is connected to the drain of the FET 45 on the plus line 4. Rectifying diode 46 and the diode
And a smoothing capacitor 47 provided between the cathode 46 and the ground line 4 '. The DC booster circuit 9 stores energy when the FET 45 is turned on by a control pulse sent from the control circuit 15 via the gate drive circuit 18 and stores energy when the FET 45 is turned off. Release the stored energy,
A DC voltage is boosted by superimposing a voltage corresponding to this on the input voltage.

(B-5. High-frequency booster circuit) As the high-frequency booster circuit 10, a self-excited push-pull type inverter circuit utilizing the reciprocal operation of two FETs is used.

48 is a choke coil, one end of which is a DC booster circuit 9
The other end is connected to the center tap of the primary winding 49a of the transformer 49.

Reference numerals 50 and 51 denote N-channel FETs, respectively, and their sources are both connected to the ground line 4 'via the current detecting resistor 17. The drain of one FET 50 is connected to one end of the primary winding 49a of the transformer 49, and the drain of the other FET 51 is connected to the other end of the primary winding 49a.

Reference numeral 52 denotes a feedback winding, one end of which is connected to the FET 5 via a resistor 53.
Connected to one gate. Further, the other end of the feedback winding 52 is connected to the gate of the FET 50 via the resistor 54.

55 and 55 'are capacitors; 56, 56 and 56' and 56 'are Zener diodes; the capacitor 55 and the Zener diodes 56 and 56 in an opposed state are interposed between the gate and source of the FET 50; Zener diodes 56 'and 56' facing each other are interposed between the gate and source of the FET 51. The Zener diode is provided as a measure against surge voltage.

Reference numerals 57 and 57 'denote constant current diodes, which are provided for regulating switching timing of the switching operations of the FETs 50 and 51 and reducing power loss. On the other hand, 57 is a positive output terminal of the DC booster circuit 9. And the other end 57 ′ is connected to the plus output terminal of the DC booster circuit 9.
Inserted between the gate of FET51.

58 is a resistor provided between the gate and source of the FET 50, 5
8 'is a resistor provided between the gate and the source of the FET 51.

59 and 60 are capacitors, one of which is provided between both terminals of the primary winding 49a of the transformer 49, and the other 60 is
Are provided between both terminals of the secondary winding 49b.

Thus, in the high-frequency booster circuit 10, the feedback winding 52
The switching control of the FETs 50 and 51 is performed opposite to each other, and a sine wave output is obtained through the transformer 49.

The resonance frequency of the high-frequency booster circuit 9 is defined by the inductance of the primary winding 49a of the transformer 49 and the capacitance of the capacitor 59 or 60, and its value is selected to be 20 KHz. Increasing the resonance frequency can reduce the size of the transformer 49 and the trigger transformer constituting the igniter circuit. However, if the frequency is too high, an acoustic resonance phenomenon will occur and lighting of the lamp will become unstable. This value of 20 KHz is higher than the conventional value of 10 KHz for a 35 W lamp, but is in a range that does not cause an acoustic resonance phenomenon (30 KHz or less).

(B-6. Current-limiting load and igniter circuit) 61 and 61 'are AC lines, one of which is a transformer 49.
One end of the secondary winding 49b is connected to the AC output terminal 12, and the secondary winding 62b of the trigger transformer 62 is provided on the AC line 61. An AC line 61 'connects the other end of the secondary winding 49b and the AC output terminal 12', and a lamp current detecting capacitor 63 is provided on the AC line 61 '.
Is provided.

The secondary winding 62b of the trigger transformer 62 and the capacitor 63 constitute a current-limiting load, and the capacitor 63 also serves to detect the lamp current of the metal halide lamp 13. If the capacitor 63 is also used to detect the lamp current, the circuit becomes simpler and the cost can be reduced as compared with the case where a current transformer is used for the lamp current detection.

One end of the primary winding 62a of the trigger transformer 62 is connected to the AC line 61 near the high-frequency booster circuit 10, and the other end is connected to the resistor 64.
Is connected to the anode of the thyristor 65.
If a thyristor is used as a switching element, the rated value for surge current is high, so Sydac (SSS)
The reliability is higher than when using.

66 is a condenser, and an AC line near the transformer 49
It is provided between 61 and the cathode of thyristor 65,
A resistor 67 is connected in parallel with the capacitor 66.

Reference numeral 68 denotes a Zener diode, the cathode of which is connected to the AC line 61 near the transformer 49, and the anode of which is a resistor.
It is connected to the cathode of the thyristor 65 via 69 and 70. The gate of the thyristor 65 is connected between the resistors 69 and 70.

 71 is a capacitor provided in parallel with the resistor 70.

Reference numerals 72, 72 'denote resistors connected in parallel to each other. One end of each of them is connected to the cathode of the thyristor 65, and the other end is connected to the anode of the diode 73.

74 is a thyristor whose anode is a diode 73
Of the AC line 61 '
It is connected to the. Then, a voltage from the igniter starting circuit 14 is applied between the gate and the cathode of the thyristor 74, whereby on / off control of the thyristor 74 is performed.

The igniter circuit is provided with an igniter starting circuit 14 (described later) at the start of lighting or at the time of temporary turning off after lighting.
The thyristor 74 is turned on in response to the signal from the input terminal, and the capacitor 66 is gradually charged in the half-wave period of the AC output output from the high-frequency booster circuit 10.

The terminal voltage of the capacitor 66 is detected by a circuit composed of the Zener diode 68 and the resistors 69 and 70.When the terminal voltage of the capacitor 66 rises and the Zener diode 68 conducts, the thyristor 65 is turned on and the capacitor 66 is discharged. .

The voltage generated at this time is boosted by the trigger transformer 62 to become a high-voltage starting pulse, which is superimposed on the sine wave alternating current and applied to the metal halide lamp 13 to start the lamp.

(B-7. Igniter starting circuit) Reference numeral 75 denotes a rectifying diode, the anode of which is connected to the AC output terminal 12 ', and the cathode of which is connected via an integrating circuit consisting of a resistor 76 and a capacitor 77 and a base resistor 78. NP
Connected to the base of N transistor 79.

The NPN transistor 79 is grounded at the emitter, and its collector is connected to the power supply terminal 81 via the resistor 80.
A resistor 82 is interposed between the base and the emitter. still,
The power supply terminal 81 is connected to the plus line 4 (between the NO contact 23b and the DC boost circuit 9) via a diode, and a predetermined voltage is applied when the lighting switch 5 is closed.

An NPN transistor 83 is an emitter follower, the base of which is connected to the collector of a transistor 79, and the emitter of which is connected via a resistor 84 to the thyristor described above.
Connected to 74 gates. A resistor 85 and a capacitor 86 are provided between the gate and cathode of the thyristor 74 in a parallel relationship with each other.

87 is an NPN transistor whose emitter is grounded,
Its base is connected to the emitter of the transistor 83 via a resistor 88, and its collector is connected to a power supply terminal 81 via a resistor 89.
And to the input terminal of the lighting abnormality detection circuit 21.

90 is a resistor interposed between the base and the emitter of the transistor 87.

In the igniter starting circuit 14, since no voltage is generated across the capacitor 63 immediately after the lamp starts to be turned on, the transistor 79 is turned off, the transistor 83 is turned on, and the thyristor of the igniter circuit is turned on. 74
Turns on. This generates a start-up pulse as described above.

At this time, the transistor 87 is also turned on, and its collector output is sent to the lighting abnormality detection circuit 21 described later as a signal indicating that the metal halide lamp 13 has not been turned on yet.

Thereafter, when the lamp is turned on, a voltage higher than a predetermined value is applied to the capacitor 63, so that the transistor 79 is turned on and the transistors 83 and 87 are turned off. Therefore, thyristor 74
Is turned off, the generation of the start pulse is stopped, and the lighting abnormality detection circuit 21 is notified that the lamp has been turned on.

(B-8. Lighting Abnormality Detection Circuit) Reference numeral 91 denotes an NPN transistor whose emitter is grounded, and its base is connected via a resistor 92 to the collector of a transistor 87 provided in the output stage of the igniter starting circuit 14. The collector of the transistor 91 is connected to the anode of the diode 94 via the resistor 93, and the cathode of the diode 94 is connected to the power supply terminal.

Reference numeral 95 denotes a resistor provided between the base and the emitter of the transistor 91.

Reference numeral 96 denotes a timer capacitor provided between the anode of the diode 94 and the ground line.

 97 is a resistor provided in parallel with the diode 94.

Reference numeral 98 denotes a diode, the anode of which is connected to the anode of the diode 94 via a resistor 99.

100 is an emitter-grounded NPN transistor whose collector is connected to the base resistor 101 of the transistor 29 of the relay cutoff circuit 7 and whose base is connected to the cathode of the diode 98.

Reference numeral 102 denotes a resistor provided between the base and the emitter of the transistor 100.

Thus, in the lighting abnormality detection circuit 21, when the transistor 87 in the output stage of the igniter starting circuit 14 is kept on, the transistor 91 is turned off, and after the capacitor 96 is charged and a predetermined time has elapsed, the diode 98 and the transistor Ten
0 turns on, so that the transistor 2 of the relay cutoff circuit 7
Works to turn 9 on.

(B-9. Control Circuit) [FIGS. 2 and 3] The control circuit 15 is an output voltage of the DC boosting circuit 9 which is detected by the voltage dividing resistors 16 and 16 'provided at the output stage of the DC boosting circuit 9. Then, a control pulse having a duty cycle corresponding to a signal indicating the output current of the DC booster circuit 9 detected by the current detecting resistor 17 is generated and transmitted to the gate of the FET 45 of the DC booster circuit 9 via the gate drive circuit 18. Is what you do.

103 is a PWM control IC, for example, provided with two error amplifiers 104 and 105 as shown in FIG.
Is connected between the voltage dividing resistors 16 and 16 ', and a predetermined reference voltage is applied to the inverting input terminal.

Further, the terminal voltage of the current detection resistor 17 is sent to the non-inverting input terminal 105a of the error amplifier 105 after passing through the amplifier circuit 106 and the low-pass filter 107. A reference voltage is applied.
The output terminals of the error amplifiers 104 and 105 are OR-connected to the minus input terminal of the PWM comparator 108,
The sawtooth wave from the oscillator 109 is input to the plus input terminal of the comparator 108.

Numeral 110 denotes a comparator for adjusting the idle period, the minus input terminal of which is connected to the control terminal 110a, and the plus input terminal of which is connected to the output terminal of the oscillator 109. Although not shown, a predetermined voltage is applied to the control terminal 110a so that the upper limit of the duty cycle of the control pulse is defined.

An AND circuit 111 performs an AND operation on an output of the PWM comparator 108 and an output of the idle period adjustment comparator 110, and outputs an output signal from the output mode switching circuit 112.
The data is sent to the control output terminal 114 via the buffer 113.

The output signal of the PWM control IC 103 is a gate drive circuit
The signal is sent to the gate of the FET 45 of the DC boosting circuit 9 via 18.

(B-10. Output Current Abnormality Detection Circuit) Reference numeral 115 denotes a comparator for comparing the output voltage of the low-pass filter 107 with a reference voltage _Vref.
To be sent to the base.

The collector of the transistor 117 is connected to the base resistor 101 of the transistor 29 of the relay cutoff circuit 7.

Reference numeral 118 denotes a resistor provided between the base and the emitter of the transistor 117.

Thus, in the output current abnormality detecting circuit 19, the output current of the DC boosting circuit 9 detected by the current detecting resistor 17 is large, and therefore, the amplification circuit 016 and the low-pass filter 1
When the detection voltage obtained through 07 becomes equal to or higher than the reference voltage _Vref , it is determined that an abnormality has occurred, the transistor 117 is turned on, and the transistor 29 of the relay cutoff circuit 7 is turned on.

(B-11. Output Voltage Abnormality Detection Circuit) 119 is a Zener diode whose cathode is DC
The anode connected to the plus side output terminal of the booster circuit 9 is grounded via the resistor 120 and the timer capacitor 121.

Reference numeral 122 denotes a diode whose cathode is connected to the cathode of the Zener diode 119 and whose anode is connected between the resistor 120 and the capacitor 121.

Reference numeral 123 denotes an NPN transistor of an emitter follower. The collector is connected to the cathode of the diode 124, and the anode of the diode 124 is connected to the power supply terminal 81.
The base is connected between the resistor 120 and the capacitor 121.

Reference numeral 125 denotes a common-emitter NPN transistor whose collector is connected to the base resistor 101 of the transistor 29 of the relay cutoff circuit 7 and whose base is connected to the emitter of the transistor 123 via the resistor 126.

127 is a resistor provided between the base and the emitter of the transistor 125.

Thus, in this output voltage abnormality detection circuit 20,
If the output voltage of the DC boosting circuit 9 continues to be at the maximum value, the Zener diode 119 becomes conductive and the capacitor 121
Are charged, and after a lapse of a predetermined time, the transistors 123 and 125 are turned on, and the transistor 29 of the relay cutoff circuit 7 is turned on.

(C. Operation) Next, when the operation of the lighting circuit 1 has no abnormality in the circuit state and the lamp is normally lit after turning on the lighting switch 5 (hereinafter referred to as “normal state”), the circuit state is abnormal. Are described separately (hereinafter, referred to as “abnormal time”).

(C-1. Normal operation) When the lighting switch 5 is closed, the transistor 24 of the relay cutoff circuit 7 is in the ON state, the relay 23 is turned on, and the contact 23b is closed. It is supplied to the booster circuit 9.

Immediately after the lighting switch 5 is turned on, the lamp is not lit and the output current of the DC boosting circuit 9 is small, so that the PWM control I
FET4 of DC booster circuit 9 from C103 via gate drive circuit 18
The control pulse sent to the gate 5 has a duty cycle corresponding to the value detected by the voltage dividing resistors 16 and 16 '. Therefore, the output power of the DC booster circuit 9 is increased, and the output power is exchanged by the high-frequency booster circuit 10 to a sine wave AC of 20 KHz and applied to the metal halide lamp 13.

Further, since no voltage is generated in the lamp current detecting capacitor 63, the igniter starting circuit 14 is activated, and the thyristor 74 of the igniter circuit is turned on to charge the capacitor 66. Turns on, generating a high-voltage pulse. This is superimposed on the AC output of the high-frequency booster circuit 10 as a lamp start pulse, and the metal halide lamp 13 is triggered.

Until the metal halide lamp 13 is turned on, the transistor 87 of the igniter starting circuit 14 is on, so the transistor 91 of the lighting abnormality detection circuit 21 is off, and the capacitor 96 is gradually charged. However, before the transistor 100 is turned on, the metal halide lamp 13
Lights up, this is detected by the capacitor 63 and the igniter starting circuit 14, and the transistor 87 is turned off.
The transistor 91 is turned on, and the capacitor 96 is discharged.

In the normal state, the transistor 117 of the output current abnormality detection circuit 19 and the Zener diode 1 of the output voltage abnormality detection circuit 20
19, the transistors 123 and 125 remain off, so that the transistor 29 of the output stage is on while the transistor 29 of the relay cutoff circuit 7 is off.

Then, a control pulse having a duty cycle corresponding to the output voltage and output current of the DC booster circuit 9 is supplied to the PWM control IC 103.
This is fed back to the FET 45 of the DC booster circuit 9 via the gate drive circuit 18, so that the output voltage of the DC booster circuit 9 is controlled.

When the lamp voltage increases as the luminous flux of the metal halide lamp 13 increases after the lamp is turned on, the output current of the DC booster circuit 9 increases, so that the duty cycle of the control pulse output from the PWM control IC 103 decreases. Then, the output voltage of the DC boosting circuit 9 decreases accordingly. Finally, the output current of the DC booster circuit 9 saturates to a steady level, and the luminous flux of the metal halide lamp 13 falls to the rated luminous flux.

(C-2. Abnormal state) Next, the operation of the lighting circuit 1 in the abnormal state is described in the case where the lamp is not connected between the AC output terminals 12 and 12 ', or the lamp cannot be turned on due to lamp life or the like (hereinafter referred to as " When the output voltage of the DC booster circuit 9 is abnormal (hereinafter, referred to as “output current abnormal”), and when the output voltage is in an abnormal state (hereinafter, referred to as “abnormal output current”). , "When the output voltage is abnormal.")
A description will be given separately for a case where there is an abnormality in the battery voltage (hereinafter, referred to as “when the battery is abnormal”).

(C-2-a. When the lamp cannot be turned on) When the metal halide lamp 13 is not connected between the AC output terminals 12 and 12 'and is in an open state, or when the lamp cannot be turned on due to lamp life or the like. Is a thyristor of the igniter circuit because the lamp 63 is detected as unlit by the capacitor 63 and the igniter starting circuit 14.
Turn on 74 to generate a start pulse. During this time, the transistor 87 of the igniter starting circuit 14 is on, and thus the transistor 91 of the lighting abnormality detection circuit 21 is off.

However, since the lamp does not turn on any more, the capacitor 96 of the lighting abnormality detection circuit 21 is charged and its terminal voltage rises, and the transistor 100 turns on after a certain time has elapsed since the transistor 91 turned off.

As a result, the transistor 29 of the relay cutoff circuit 7 is turned on, its output is held, and the transistor 24 is turned off. Accordingly, since the relay 23 is turned off and the contact 23b is opened, the power supply to the DC booster circuit 9 is cut off, and this state is maintained until the lighting switch 5 is turned on again, and the generation of the start pulse is generated. Stop.

(C-2-b. When output current is abnormal) When a short circuit occurs at the output stage of the high-frequency booster circuit 10, an excessive current flows from the battery 2 to the DC booster circuit 9 and the high-frequency booster circuit 10, and this is current detection. The voltage is converted by the use resistor 17 and input to the comparator 115 via the amplifier circuit 106 and the low-pass filter 107.

Then, the input voltage is changed by the comparator 115 to the reference voltage V.
_Since it is determined that the voltage is _{equal to} or _larger than _ref , an H signal is sent to the transistor 117, so that the transistor 117 is turned on.

Thereby, the transistor 29 of the relay cutoff circuit 7 is
Is turned on, the transistor 24 in the output stage is turned off, the relay 23 is turned off, the power supply is cut off, and this state is maintained until the lighting switch 5 is turned on again.

(C-2-c. When the output voltage is abnormal) When the lamp is short-circuited or when the high-frequency
For example, when the output stage becomes open at the output stage, the duty cycle of the control pulse sent from the control circuit 15 to the DC booster circuit 9 via the gate drive circuit 18 becomes maximum, and thus the output voltage of the DC booster circuit 9 Becomes the maximum value, so that the Zener diode 11 of the output voltage abnormality detection circuit 20
9 conducts.

As a result, the capacitor 121 is filled and its terminal voltage rises. After a predetermined time, the transistors 123 and 125 are turned on, so that the transistor 29 of the circuit 7 for turning off the relay is turned on, the transistor 24 is turned off, and the relay 23 is turned off. This state is maintained until the power supply is cut off and the lighting switch 5 is turned on again.

(C-2-d. At the time of battery abnormality) When the voltage of the battery 2 becomes excessive, the overvoltage detection circuit 8
Since the Zener diode 41 becomes conductive and the transistor 43 is turned on, the transistor 24 of the relay cutoff circuit 7 is turned off and the relay 23 is turned off, so that the power supply is cut off. However, when the battery voltage returns to the predetermined voltage or lower again only by temporarily increasing the battery voltage, the transistor 43 is turned off, the transistor 24 is turned on, the relay 23 is turned on, and the power supply is restored.

As described above, when the battery voltage becomes excessive, the power supply is not shut off, and the relay 23 is turned on again when the battery voltage returns to a predetermined value. If a voltage or the like is superimposed, an instantaneous overvoltage state occurs, and if this state is determined to be abnormal, a dangerous situation is caused. In other words, unless the driver turns on the lighting switch 5 immediately, a disadvantage arises in that the driver must travel in the dark while the metal halide lamp 13 remains off.

When the polarity of the battery 2 is erroneously connected to the DC voltage input terminals 3 and 3 ', the relay 22 does not turn on because the diode 22 is off.

(G. Effects of the Invention) As is clear from the above description, the lighting circuit of the vehicular discharge lamp of the present invention includes a DC boosting circuit for boosting a DC voltage from a DC voltage input terminal, and a DC boosting circuit for the DC boosting circuit. A converter circuit for converting an output voltage to an AC voltage, and a lighting circuit for a vehicle discharge lamp in which an output of the converter circuit is applied to the discharge lamp via a current-limiting load, in series with a lighting switch. The connected power cutoff switch means, the output current abnormality detection means for determining that the output current of the DC booster circuit is greater than a predetermined value and sending a signal to the power cutoff switch means, and / or the DC booster circuit. Output voltage abnormality detection means for determining that an abnormality has occurred when the duration of the state in which the output voltage is at the maximum value exceeds a predetermined value and sending a signal to the power cutoff switch means, or An overvoltage detecting means for detecting an overvoltage state of the power source, wherein the means for detecting an abnormality sends a signal to the power cutoff switch means when the circuit is abnormal to cut off the power supply from the DC power supply to the lighting circuit. It was made.

Therefore, according to the present invention, when an abnormality in the output current or output voltage of the DC booster circuit is detected, or when an overvoltage of the DC power supply is detected, the power supply from the DC power supply to the lighting circuit is switched by the power cutoff switch means. Since the supply of the voltage is cut off, it is possible to prevent a discharge lamp or a circuit element from being broken or an electric shock accident.

In the above-described embodiment, the power supply from the DC power supply to the lighting circuit is cut off by opening the contact point of the relay when the circuit is abnormal, but the technical scope of the lighting circuit of the vehicle discharge lamp of the present invention is limited. The present invention is not construed as being narrowly limited to this, and it is needless to say that any aspect of the contact configuration of the relay (such as the use of the transfer contact and the b-contact) is included in the technical scope of the present invention.

[Brief description of the drawings]

1 to 3 show an embodiment of a lighting circuit for a vehicle discharge lamp according to the present invention. FIG. 1 is a block diagram showing the overall configuration, FIG. 2 is a circuit diagram, and FIG. FIG. 3 is a block diagram illustrating a configuration of a PWM control IC. DESCRIPTION OF SYMBOLS 1... Lighting circuit of vehicle discharge lamp 2... DC power supply 3. 3 ′... DC voltage input terminal 5... Lighting switch 8... Overvoltage detecting means 9. , 10 ... Converter circuit, 13 ... Discharge lamp, 17, 19 ... Output current abnormality detection means, 16, 16 ', 20 ... Output voltage abnormality detection means, 23, 24 ... Power cutoff switch means, 62b , 63 …… current-limiting load,

Continued on the front page (72) Inventor Akihiro Matsumoto 500 Kitawaki, Shimizu City, Shizuoka Prefecture Inside Koito Manufacturing Shizuoka Plant (72) Inventor Murata Atsuhiko 500 Kitawaki Shimizu City Shizuoka Prefecture Koito Manufacturing Shizuoka Plant (72 Inventor Shoichi Yagi 500 Kitawaki, Shimizu City, Shizuoka Prefecture Inside the Koito Manufacturing Co., Ltd. Shizuoka Plant (56) References JP-A-62-259391 (JP, A) JP-A-57-162290 (JP, A) JP-A-57-46499 (JP, A) JP-A-56-136498 (JP, A) JP-A-60-207462 (JP, A)

Claims (4)

(57) [Claims] 1. A DC booster circuit for boosting a DC voltage from a DC voltage input terminal, and a converter circuit for converting an output voltage of the DC booster circuit to an AC voltage, wherein an output of the converter circuit is supplied via a current-limiting load. In the lighting circuit of the vehicle discharge lamp, which is applied to the discharge lamp, the power cutoff switch means connected in series to the lighting switch, and the output current of the DC booster circuit is detected, and the output current is detected. Output current abnormality detection means for sending a signal to the power cutoff switch means when it is determined to be abnormal when the value is equal to or more than a predetermined value, wherein the power cutoff switch means indicates a circuit state abnormality from the output current abnormality detection means. A lighting circuit for a discharge lamp for a vehicle, wherein when a signal is received, supply of a power supply voltage from a DC power supply to the lighting circuit is cut off. 2. A DC booster circuit for boosting a DC voltage from a DC voltage input terminal, and a converter circuit for converting an output voltage of the DC booster circuit into an AC voltage, wherein an output of the converter circuit is supplied via a current-limiting load. In the lighting circuit of the vehicle discharge lamp, which is applied to the discharge lamp, the power supply switch means connected in series to the lighting switch and the output voltage of the DC booster circuit are detected, and the output voltage is detected. Output voltage abnormality detection means for judging an abnormality when the continuation time of the maximum value state is equal to or more than a predetermined value and sending a signal to the power supply cutoff switch means, wherein the power supply cutoff switch means Upon receiving a signal indicating a circuit state abnormality from the output voltage abnormality detection means, the supply of the power supply voltage from the DC power supply to the lighting circuit is cut off. Road. 3. An overvoltage detecting means for detecting an overvoltage state of the DC power supply is provided, and when the voltage of the DC power supply becomes a predetermined value or more, it is determined that an abnormality has occurred, and a signal is transmitted to the power cutoff switch means so as to provide a direct current. When the supply of the power supply voltage from the power supply to the lighting circuit is interrupted, and when the voltage of the DC power supply again becomes lower than the predetermined value, the overvoltage detecting means sends a signal to the power cutoff switch means so that the lighting circuit is switched from the DC power supply. The lighting circuit for a vehicular discharge lamp according to claim 1 or 2, wherein supply of a power supply voltage to the vehicle is restored. 4. A DC booster circuit for boosting a DC voltage from a DC voltage input terminal, and a converter circuit for converting an output voltage of the DC booster circuit to an AC voltage, wherein an output of the converter circuit is supplied via a current-limiting load. In a lighting circuit of a vehicular discharge lamp which is applied to a discharge lamp, a power supply switch means connected in series to a lighting switch and an overvoltage detection means for detecting an overvoltage state of a DC power supply are provided. When the voltage of the DC power supply becomes equal to or more than a predetermined value, the overvoltage detection means determines that there is an abnormality and sends a signal to the power cutoff switch means to cut off the supply of the power supply voltage from the DC power supply to the lighting circuit, When the voltage of the DC power supply falls again below the predetermined value, the overvoltage detection means sends a signal to the power cutoff switch means to supply the power supply voltage from the DC power supply to the lighting circuit. Lighting circuit of a vehicular discharge lamp, characterized in that so as to return.