JPH02197441A - Lamp lighting circuit for vehicle - Google Patents

Abstract

PURPOSE:To prevent a lamp socket from its electric breakdown and an electric shock, when a lamp is replaced, by constituting a circuit so as to interrupt supply of power to the lamp when it is discriminated that the lamp can not be turned on and/or abnormality is generated in a level of battery voltage and polarity. CONSTITUTION:An overvoltage detecting circuit 4, detecting battery voltage for its excessive high level, is connected between input terminals 3, 3' of a lighting circuit 1 connected to positive and negative poles of a battery 2. While providing a lighting switch circuit 5 receiving a signal showing the excessive voltage and a power cutoff signal from a lamp abnormality detecting circuit 13 to interrupt supply of the battery voltage, this circuit 5 is constituted by providing a lighting switch and a power cutoff circuit. The lamp abnormality detecting circuit 13 is constituted so as to output a power cutoff signal by judging a lamp disabled from lighting by the result of measuring non-lighting time of the lamp from the point of time the metal halide lamp 10 is first started by an ignitor starter circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The details of the vehicle lamp lighting circuit of the present invention will be explained in accordance with the following items.

A. Industrial field of application B1 Overview of the invention C1 Background technology 1 Problems to be solved by the invention E9 Means for solving the problems F. Examples [Figures 1 and 2] a0 Circuit configuration a-1 , overvoltage detection circuit a-28 point lighting switch path a-3, DC boost circuit a-4, high frequency boost circuit a-5, current limiting load and igniter circuit a-6. Igniter starting circuit a-7, control circuit a-8゜Lamp abnormality detection circuit, operation b-1, normal b-2, abnormal b-2-8, lighting failure b-2-b, battery voltage abnormality Time C0 action G1 Effect of the invention (A. Field of industrial application) The present invention relates to a novel vehicular lamp lighting circuit. Specifically, the present invention aims to provide a new vehicle lamp lighting circuit that is designed to prevent lamp insulation breakdown and element failure due to lamp abnormalities, battery voltage abnormalities, etc., as well as electric shock accidents when replacing lamps. It is.

(B. Summary of the Invention) The vehicle lamp lighting circuit of the present invention includes a lighting switch, a power cutoff switch connected in series to the lighting switch, a lighting switch, and a power cutoff switch between input terminals to which a DC power source is connected. A lamp lighting circuit for a vehicle, comprising a switch means for permitting power supply to the lamp when the lamp switch is closed, and a circuit abnormality detection means for detecting an abnormality in the circuit state of the lighting circuit, the circuit comprising: The detection means includes a lamp abnormality detection means for detecting the inability to light the lamp and/or a power supply voltage detection means for detecting the input voltage value from the DC power supply or its polarity. It is designed to cut off the supply of power supply voltage from the DC power supply by being opened in response to a signal indicating an abnormality in the circuit state.In particular, the lamp abnormality detection means detects whether the lamp is turned on or off based on the lamp current. a lamp state detection means for detecting a non-lighting state; a non-lighting time measuring means for measuring a non-lighting time calculated from a signal indicating that the lamp is not lighting sent from the lamp state detecting means; This device is constructed with a power cutoff switch control means that opens the power cutoff switch and cuts off the supply of DC power supply voltage when the power cutoff switch is turned on. Immediately detects voltage abnormalities due to overvoltage or reverse polarity connection of the DC power supply and prevents lamp insulation breakdown and failure of circuit elements, as well as prevents electric shock accidents when replacing lamps. Moreover, this can be realized without complicating the circuit configuration or significantly increasing costs.

(C. Background Art) Incandescent light bulbs are currently widely used as light sources for automobile headlights, and lighting circuits for these incandescent light bulbs include, for example,
A circuit is used in which a relay coil is connected between one terminal of the battery via a lighting switch, and an incandescent light bulb is connected between one terminal of the battery via a relay contact.

In the lighting circuit of such an incandescent light bulb, an abnormality due to the lifespan of the bulb may occur, overvoltage from the battery is input, or the polarity of the battery is incorrect and it is connected to the input terminal of the lighting circuit in the opposite direction. Even in such a case, the worst case scenario is that the filament will break, so there is no safety problem, and no special protection circuit is usually provided for this purpose.

(D. Problems to be Solved by the Invention) Recently, metal halide lamps have been in the spotlight as a new light source to replace incandescent light bulbs, including halogen lamps.This metal halide lamp is used as a light source for automobile headlights. In such cases, it is necessary to instantly light or relight the lamp, and the starting voltage at that time is also very high (about 10 to 20 kV).

Therefore, if the lamp does not light up after the lighting switch is turned on due to an abnormality caused by the lamp's lifespan, high voltage will continue to be generated between the output terminals of the lighting circuit, and the lamp will not turn on. There is a risk of ignition due to insulation breakdown between the contact terminals installed in the socket, or of electric shock if the user replaces the lamp without realizing that high voltage is being applied to the lamp. There's a problem.

In addition, if the battery becomes overvoltage or if the polarity of the battery is incorrectly connected to the input terminal of the lighting circuit, it may destroy the circuit elements and cause circuit malfunction, resulting in high voltage generation and lamp destruction. There is a danger of inviting

(E. Means for Solving Problem 8) Therefore, in order to solve the above-mentioned problems, the vehicle lamp lighting circuit of the present invention uses a circuit abnormality detection means for detecting an abnormality in the circuit state of the lighting circuit to prevent the lamp from turning on. and/or a power supply voltage detection means to detect the input voltage value from the DC power supply or its polarity, and a power supply cutoff switch connected in series to the lighting switch, and a lighting switch and a power supply cutoff switch. and switch means for permitting power supply to the lamp when both are closed, and the power supply cutoff switch is opened in response to a signal indicating an abnormality in the circuit state from the circuit abnormality detection means, thereby switching off the DC power supply. The supply of power supply voltage from the mains is cut off.

Therefore, according to the vehicle lamp lighting circuit of the present invention, when it is determined that the lamp cannot be lit or that there is an abnormality in the magnitude or polarity of the battery voltage value, the power supply to the lamp is cut off. It is possible to prevent insulation breakdown of the socket and electric shock during lamp replacement, and also to prevent destruction of circuit elements and associated malfunctions.

(F. Embodiment) [FIGS. 1 and 2] Details of the vehicular lamp lighting circuit of the present invention will be described below according to the illustrated embodiment. In the illustrated embodiment, the vehicular lamp lighting circuit of the present invention is applied to a lighting circuit for an automobile metal halide lamp.

(a, circuit configuration) 1 is a lighting circuit.

Reference numeral 2 denotes a battery, and the battery voltage is approximately DC 12 V. The positive electrode of the battery 2 is connected to the plus input terminal 3 of the lighting circuit 1, and the negative electrode is connected to the minus input terminal 3'.

4 is an overvoltage detection circuit connected between input terminals 3 and 3', which detects when the battery voltage becomes excessive and sends a signal indicating that the battery voltage is overvoltage to a lighting switch circuit, which will be described later. It has become.

Reference numeral 5 denotes a lighting switch circuit including a lighting switch and a power cutoff circuit, which receives a signal indicating an overvoltage of the battery 2 from the above-mentioned overvoltage detection circuit 4 or a signal indicating a lamp abnormality from a lamp abnormality detection circuit described later. Provided to cut off the supply of battery voltage.

6 is a DC booster circuit placed after the lighting switch circuit 5, and is provided to boost the battery voltage input via the lighting switch circuit 5, and its DC output voltage is controlled by a control circuit to be described later. Levels are now controlled.

Reference numeral 7 denotes a high-frequency booster circuit, which is arranged after the DC booster circuit 6 and is provided to convert the DC output voltage from the DC booster circuit 6 into a sine wave alternating current voltage.

Reference numeral 8 denotes a current limiting load and igniter circuit, which is arranged after the high frequency booster circuit 7, and a metal halide lamp 10 is connected between its output terminals 9 and 9'.

Reference numeral 11 denotes an igniter starting circuit which, when information regarding the lamp current of the metal halide lamp 10 is sent from the current limiting load and igniter circuit 8, applies a signal corresponding to this to the igniter circuit of the current limiting load and igniter circuit 8. The control circuit controls the generation and stopping of starting pulses, or sends a predetermined timing signal to a control circuit that will be described later. Further, the igniter starting circuit 11 is configured to send a signal synchronized with a starting pulse generation signal for the current limiting load and the igniter circuit 8 to a lamp abnormality detection circuit to be described later.

Reference numeral 12 denotes a control circuit, which displays a control mode corresponding to the time when the metal halide lamp 10 is off, sends a predetermined control signal to the DC booster circuit 6, adjusts the boost amount, and controls the high frequency booster circuit 7. is provided to control the level of the DC input voltage of the metal halide lamp 10 and the lamp current of the metal halide lamp 10.

13 is a lamp abnormality detection circuit, which measures the lamp non-lighting time calculated from the time when the metal pallite lamp 10 is first started by the igniter starting circuit 11, and when this exceeds a predetermined time, the lamp is turned on. It is provided to send a power cutoff signal to the lighting switch circuit 5 when it is determined that it is not possible.

(a-1, overvoltage detection circuit) 14.14' is a power supply line, one of which is a positive line connected to the positive input terminal 3, and the other 14 is a positive line connected to the positive input terminal 3.
' is a negative line connected to the negative input terminal 3'.

15.16 are resistors connected in series, while 15
The opposite terminal of the resistor 16 is connected to the anode of a Zener diode 17, and the cathode of the Zener diode 17 is connected to the positive line 14. Further, the terminal of the other resistor 16 on the side opposite to the resistor 15 is connected to the negative line 14'.

18 is a switching NPN transistor, the base of which is connected between the resistors 15 and 16, and the emitter of which is connected to the minus line 14'.

(a-2, lighting switch circuit) 19.20 is a voltage dividing resistor connected in series between the power supply lines 14 and 14', while the counter resistor 20 of 19
The side terminal is connected to the positive line 14, and the opposite terminal 20 of the resistor 19 is connected to the negative line 14'. A transistor 18 is connected between the voltage dividing resistors 19 and 20.
collector is connected.

21 is a switching NPN transistor whose emitter is grounded, its base is connected between resistors 19 and 20, and its collector is connected to one contact 2 of the lighting switch 22.
It is connected to one end of a coil 23a of the relay 23 via the wire 2a, and the other end of the coil 23a is connected to the positive line 14.

A diode 24 is provided in antiparallel to the coil 23a of the relay 23.

25.25' is a warning display LED, while 25
The anode of is connected to the transfer contact 23b of the relay 23 via the limiting resistor and the other contact 22b of the lighting switch 22.
It is connected to the NC (normally closed) contact side of
Its cathode is connected to negative line 14'. In addition, the other LED 25' is in antiparallel to LED 25,
That is, its cathode is connected to the anode of the LED 25, and the anode is connected to the minus line 14'. Note that the common contact of the transfer contacts 23b of the relay 23 is connected to the positive line 14.

(a-3, DC boost circuit) The DC boost circuit 6 is configured as a square-shaped DC-DC converter, and one end thereof is an inductor connected to the No (normal oven) contact of the transfer contact 23a of the relay 23. 26, an N-channel FET 27 which is disposed at the subsequent stage and is switched by a control pulse from the control circuit 12, and an N-channel FET 27 whose anode is FET 27.
Rectifier diode 28 connected to the drain of ET27
and the cathode of the diode 28 and the negative line 14
and a smoothing capacitor 29 connected between the two terminals. Then, in the DC booster circuit 6, the inductor 26 stores energy when the FET 27 is turned on by a control pulse from the control circuit 12, and releases the stored energy when the FET 27 is turned off, thereby increasing the input voltage. DC boosting is performed by superimposing the voltage on the

(a-4, High-frequency boost circuit) The high-frequency boost circuit 7 converts the DC boost from the DC boost circuit 8 into a sinusoidal AC voltage proportional to the DC boost, and is a self-supporting current source inverter circuit configuration that utilizes LC resonance. It is said that

For example, a push-pull type inverter circuit is used,
Although not shown, the positive output line of the DC booster circuit 6 is connected to the center tap of the primary winding of the transformer via a choke coil, and a capacitor is connected between both terminals of the secondary winding, and two capacitors are connected in parallel to this. An active switching element such as a transistor or FET is connected, and the active switching element is operated reciprocally by a feedback winding provided on the primary side of the transformer, and the output is connected to both terminals of the secondary winding of the transformer. A high frequency sinusoidal AC voltage is output between the terminals.

(a-5, current limiting load and igniter circuit) 30.30'
are AC output lines, and one of them 30 is connected to the output terminal 9 via one winding 31a of the transformer 31 and a capacitor 32 connected in series thereto, and is connected to the igniter starting circuit via a connection line 33. It is connected to a relay contact provided at 11, which will be described later. Incidentally, the winding 31a of the transformer 31 is a saturable inductance, and the 4
The a-line 31a and the capacitor 32 constitute a current-limiting load. Another AC output line 30' is connected to an output terminal 9' via a primary winding of a lamp current detection transformer, which will be described later.

One end of the other winding 31b of the transformer 31 is connected to a common contact of a relay contact, which will be described later, provided in the igniter starting circuit 11 via a connection line 34, and the other end of the winding 31b is connected to a predetermined point. It is connected to one end of a 5SS35 having a breakdown voltage of . And 5
A resistor 36 and a capacitor 37 are connected in parallel between the other end of the SS 35 and the connection line 34.

A diode 38 has its anode connected to the opposite terminal of the capacitor 37 on the side of the connection line 34 through a resistor 39, and its cathode connected to the AC output line 30'.

Reference numeral 40 denotes a lamp current detection transformer, one end of which has a secondary winding 40a connected to the AC output line 30', and the other end connected to the output terminal 9'. and,
A metal halide lamp 10 is connected between output terminals 9 and 9'.

(a-8, igniter starting circuit) 41 is a rectifying diode, the anode of which is connected to the voltage grounding side terminal of the secondary winding 40b of the lamp current detection transformer 40, and the cathode of the diode 41 An electrolytic capacitor 42 is inserted between the ground line and the ground line, thereby forming a rectifier circuit.

Reference numeral 43 designates an NPN transistor with a common emitter, the base of which is connected to the cathode of the diode 41 via a resistor 44, and the collector of which is connected to the power supply terminal 4 via a resistor 45 to the NC contact of the transfer contact 23b.
6.

47 is an NPN transistor whose emitter is also grounded, and whose base is connected to the collector of the transistor 43 via a resistor 48.

49 is a relay having two transfer contacts 49a and 149b, one end of whose coil 49c is connected to the collector of the transistor 47, and the other end connected to the power supply terminal 46.

As described above, the common contact of one transfer contact 49a of the relay 49 is connected to the terminal on the piezoresistor 39 side of the capacitor 37 of the current limiting load and igniter circuit 8 via the connection line 34, and the NC contact is connected to the AC output line 30 via a connection line 33, and the NC contact is open. Also, the other transfer contact 4
The common contact point of 9b is connected to the input terminal of the control circuit 12,
The NC contact is connected to the power supply terminal 46, and the NC contact is grounded.

(a-7, Control Circuit) The input terminal of the control circuit 12 is connected to the transfer contact 49b of the relay 49 of the igniter starting circuit 11 as described above.
The output terminal is connected to the gate of the FET 27 of the DC booster circuit 6. Then, the control circuit 12 causes a plurality of control modes to appear depending on the time that the metal halide lamp 10 is turned off. metal halide lamp 10
Control the lamp current several times the rated current of the lamp to flow for a predetermined time and then reach a steady current, or if the lamp has recently gone out, control the lamp current to flow after the lamp is turned on again. A mode discriminating circuit and a PWM circuit (not shown) are provided for control, and such control can be performed by varying the duty cycle of the control pulse sent to the gate of the FET 27 of the DC booster circuit 6. It is composed of etc.

(a-8, lamp abnormality detection circuit) 50 is a PNP transistor whose base is resistor 5
1 through the transistor 47 of the igniter starting circuit 11
The emitter is connected to the power supply terminal 46.
A resistor 52 is inserted between the base and emitter. The collector of the transistor 50 is connected to a resistor 53 and a capacitor 54 connected in series with the resistor 53.
is grounded through.

55 is a resistor connected in parallel to the capacitor 54.

56 is an NPN transistor whose emitter is grounded, the base of which is connected between the resistor 53 and the capacitor 54 via the resistor 57, and the collector of which is connected to the lighting switch circuit 5.
It is connected between voltage dividing resistors 19 and 20 of .

(b. Operation) Next, we will explain the operation of the lighting circuit 1 when there is no abnormality in the battery voltage or the metal halide lamp, etc., and the lamp lights up after the lighting switch 22 is turned on (hereinafter referred to as "normal"), and when the battery 2 A case in which the lamp does not light up even when the lighting switch 22 is turned on due to a lamp abnormality caused by overvoltage or the lifespan of the metal halide lamp (hereinafter referred to as "abnormality") will be explained separately.

(b-i, normal state) First, when the contacts 22a122b of the lighting switch 22 are closed, the transistor 18 of the overvoltage detection circuit 4 and the transistor 56 of the lamp abnormality detection circuit 13 are both in the off state, so that the lighting switch circuit 5 Since the transistor 21 is in the on state, the relay 23 is turned on,
The transfer contact 23b switches to the NO contact side,
Battery voltage is applied to the DC boost circuit 6.

Therefore, after the battery voltage input to the DC booster circuit 6 is boosted, the high frequency booster circuit 7 converts the battery voltage into an alternating current voltage, which is then applied to the metal halide lamp 10 via the current limiting load and the igniter circuit 8. Immediately after the lighting switch 22 is turned on, no lamp current is flowing yet, and this is determined by the igniter starting circuit 11 via the lamp current detection transformer 40.

That is, since no voltage is applied to the secondary winding 40b of the lamp detection transformer 40, the transistor 43 is in the OFF state, so the transistor 47 is turned on and the relay 49 is operated, so that the transfer contacts 49a and 49b are in the N state.
Switches from C contact to NO contact. Therefore, connection line 3
3.34 is connected and the capacitor 37 is connected to the capacitor 3.
The capacitor 33 is charged with a time constant defined by the capacitance of the capacitor 7 and the resistance value of the resistor 3g, and when the terminal voltage of the capacitor 33 reaches the breakover voltage of the capacitor 35, it is turned on, and the instantaneous voltage at this time is changed by the transformer 31. The voltage is transformed and superimposed on the sine wave alternating current from the high frequency booster circuit 7 as a starting pulse and applied to the metal halide lamp 10.

On the other hand, since a predetermined timing signal is sent to the control circuit 12 by switching the transfer contact 49b of the relay 49 to the NO contact side, the control circuit 12 detects the time during which the metal halide lamp 10 is turned off. The duty cycle of the control pulse sent to the DC booster circuit 6 is varied and
Controls the level of C output voltage. Therefore, this DC output voltage is converted into an AC voltage by the high frequency boost circuit 7, and the lamp current flowing to the metal halide lamp 10 via the current limiting load and igniter circuit 8 is controlled.

On the other hand, when the transistor 47 is turned on, the transistor 50 of the lamp abnormality detection circuit 13 is turned on, and the capacitor 54 is gradually charged with a time constant defined by its capacitance and the resistance value of the resistor 53.57. However,
The value of this time constant is set to be sufficiently longer than the time it takes for the metal halide lamp 10 to normally light up, so when the metal pararite lamp 10 lights up, the transistor 47.
50 is turned off, and therefore, the charge stored in the capacitor 54 up to that point is discharged through the resistor 55, and the transistor 56 is not turned on. That is, when the metal halide lamp 10 is turned on, the lamp current of this lamp is applied as a voltage to the rectifying and smoothing circuit 41, 42 via the lamp current detection transformer 40 and turns on the transistor 43. is turned off, and the potential of the capacitor 54 rises, causing the transistor 5 to turn off.
The transistor 50 is turned off before the transistor 6 is turned on. At this time, the relay 49 is simultaneously turned off, the transfer contacts 49a and 49b are switched to the NC contact side, and the generation of the starting pulse is stopped.

Once the metal halide lamp 10 is started, the lamp current is controlled by the control circuit 12, and finally the metal halide lamp 10 emits light at the rated current.

(b-2, Abnormality) Next, we will explain the operation of the lighting circuit 1 when the lighting circuit 1 is in an abnormal state: when the lighting circuit 1 cannot be lit due to the lifespan of the metal halide lamp 10, and when the battery voltage is abnormal due to overvoltage of the battery or incorrect polarity when connecting the battery. explain.

(b-2-a, when lighting is not possible) In this case, even if the lighting switch 22 is closed, the metal halide lamp 10 does not start, so the transistor 47
．． 50 and the relay 49 will continue to be on, but the potential of the capacitor 54 of the lamp abnormality detection circuit 13 will rise, and when this reaches a predetermined value, the transistor 56 will be in the on state, and the base potential of the transistor 21 of the lighting switch circuit 5 will increase. This turns off because relay 23 goes down, so relay
is turned off and the transfer contact 23b is switched to the NC contact side, so that the supply of battery voltage to the DC booster circuit 6 is cut off, and the abnormality is notified by the illumination of the LED 25.

(b-2-b, when the battery voltage is abnormal) When the battery voltage exceeds the normal value, the voltage increase can be suppressed to some extent by the constant voltage action of the lighting circuit, but if it becomes too excessive (more than 18V), the Zener Diode 17 conducts, transistor 18 turns on, and even though contact 22a of lighting switch 22 is closed, transistor 21 remains off, so transfer contact 23b of relay 23 is turned on.
It becomes the C contact side, and therefore the supply of battery voltage is cut off, and the abnormality is notified by the light emission of the LED 25.

In addition, if the polarity of the battery 2 is incorrectly connected to the input terminal 3.3', even if the lighting switch 22 is turned on, the transistor 21 becomes reverse biased and remains off, and the battery voltage is not supplied. Not released, LED25
The polarity error will be notified by the emission of '.

(c. Effect) In the lighting circuit 1, when the metal halide lamp 10 cannot be lit, the transistor 56 of the lamp abnormality detection circuit 13 is turned on after a predetermined time, and the lighting switch circuit 5
Since the supply of battery voltage is cut off to turn off the transistor 21 of the metal halide lamp 1,
A high voltage will not continue to be applied to the capacitor 54, and even if the lamp condition becomes unstable and the lamp is temporarily turned off while it is on, the potential of the capacitor 54 will be approximately 0 at this time. The supply of battery voltage is not cut off, and the metal halide lamp 10 is started again by the igniter starting circuit 11.

Further, when the battery 2 is overvoltage, the transistor 18 of the overvoltage detection circuit 4 is turned on, so the transistor 21 of the lighting switch circuit 5 is also turned off and the supply of battery voltage is cut off. This avoids a situation in which the lamp current of the metal halide lamp 10 becomes uncontrollable due to destruction, and lamp destruction occurs due to an increase in lamp current.

Then, if the polarity of battery 2 is incorrectly connected to input terminal 3.3',
Even if the transistor 21 of the lighting switch circuit 5 is reversely connected to
remains off, preventing short-circuiting of active elements (for example, FET 27 of DC booster circuit 6).
It is important to protect the active elements.

(G. Effects of the Invention) As is clear from the above description, the vehicle lamp lighting circuit of the present invention serves as a circuit abnormality detection means for detecting an abnormality in the circuit state of the lighting circuit. It has an abnormality detection means and/or a power supply voltage detection means for detecting the input voltage value or the polarity from the DC power supply, and a power supply cutoff switch connected in series with the lighting switch, and a power supply cutoff switch that is connected in series with the lighting switch, and a power supply cutoff switch that is connected in series with the lighting switch and the power supply cutoff switch when both the lighting switch and the power supply cutoff switch are closed. and switch means for permitting power supply to the lamp when the lamp is in a state of abnormality, and the power supply cutoff switch is opened in response to a signal indicating an abnormality in the circuit state from the circuit abnormality detection means, whereby the power supply voltage from the DC power source is cut off. It is characterized in that the supply of is cut off.

Therefore, according to the vehicle lamp lighting circuit of the present invention, when it is determined that the lamp cannot be lit or that there is an abnormality in the magnitude or polarity of the battery voltage value, the power supply to the lamp is cut off. It is possible to prevent insulation breakdown of the socket and electric shock during lamp replacement, and also to prevent destruction of circuit elements and associated malfunctions.

In the above embodiments, the vehicle lamp lighting circuit of the present invention was applied to a metal halide lamp lighting circuit, but the invention is not limited to this and may be applied to a lighting circuit using other light sources.
Further, in the above embodiment, an analog timer using a CR circuit and a transistor was shown as the lamp non-lighting time measuring means, but it is of course possible to use a digital timer or a counter circuit.

21・ 22・ 23・ 53. 56・ ・Power cutoff switch, ・Lighting switch, ・Switch means, 4.57... Non-lighting time measuring means, ・Power cutoff switch control means

[Brief explanation of the drawing]

The drawings show an example of the implementation of the vehicle lamp lighting circuit of the present invention, and FIG. 1 is a block diagram showing the overall configuration, and FIG. 2 is a circuit diagram. Applicant Koito Seisakusho Co., Ltd. Explanation of codes 1...Vehicle lamp lighting circuit, 2...DC power supply, 3.3'...Input terminal, 4.13...Circuit abnormality detection means, 4...・Power supply voltage detection means, 10... Lamp, 11.40... Lamp status detection means, 13... Lamp abnormality detection means,

Claims (5)

[Claims] (1) Between input terminals to which a DC power source is connected, a lighting switch, a power cutoff switch connected in series to the lighting switch, and power supply to the lamp when the lighting switch and power cutoff switch are closed. A vehicular lamp lighting circuit comprising a switch means for permitting a circuit abnormality detection means for detecting an abnormality in a circuit state of the lighting circuit, wherein the power cutoff switch detects an abnormality in the circuit state from the circuit abnormality detection means. A vehicle lamp lighting circuit characterized in that the circuit is opened in response to a signal indicating an abnormality, thereby cutting off the supply of power voltage from a DC power source. (2) The vehicle lamp lighting circuit according to claim 1, wherein the circuit abnormality detection means is a lamp abnormality detection means that detects that the lamp cannot be lit. (3) The vehicle lamp lighting circuit according to claim 1, wherein the circuit abnormality detection means is a power supply voltage detection means that detects an input voltage value and/or its polarity from a DC power supply. (4) A patent characterized in that the circuit abnormality detection means consists of a lamp abnormality detection means that detects whether the lamp cannot be lit, and a power supply voltage detection means that detects the input voltage value and/or its polarity from the DC power supply. Vehicle lamp lighting circuit according to claim 1 (5) The lamp abnormality detection means includes a lamp condition detection means that detects whether the lamp is lit or not lit based on the lamp current, and an error calculated from a signal indicating that the lamp is not lit, which is sent from the lamp condition detection means. A patent claim comprising: a non-lighting time measuring means for measuring the lighting time; and a power cutoff switch control means for opening a power cutoff switch to cut off the supply of DC power supply voltage when the non-lighting time exceeds a predetermined time. Vehicle lamp lighting circuit according to the scope of item 2 or 4