JP2010244716A - Drive circuit for lamp - Google Patents

Abstract

A signal indicating an abnormality of a vehicular lamp 21a is held by an inexpensive and simple circuit configuration.
A lamp driving circuit for driving a vehicular lamp 21a includes a lighting control unit 15a that controls a lighting state of the vehicular lamp 21a, and the operating states of the vehicular lamp 21a and the lighting control unit 15a are both normal. Or at least one of the operation states is abnormal, and a signal output unit 17a that outputs an output signal V _wng indicating the operation state determined by the operation determination unit 16a to the outside. . The signal output unit 17a includes a signal holding unit 18a that holds the state of the output signal even when the power supply to the lamp driving circuit 1a is interrupted.
[Selection] Figure 2

Description

  The present invention relates to a lamp driving circuit having a function of holding a signal indicating an abnormality occurring in a vehicle lamp.

  2. Description of the Related Art Conventionally, there is known a lighting control circuit that detects, based on a change in voltage applied to a light source, when an abnormality occurs in any of the light sources of each vehicle lamp (for example, Patent Document 1). reference). In Patent Document 1, a period for regulating the current supplied to the semiconductor light source to be less than a predetermined current is set, and the forward voltage generated from the semiconductor light source in the period is compared with the reference determination value, thereby the forward voltage of the semiconductor light source. The presence or absence of abnormalities accompanying changes in When the specified current is reduced compared to the rated current, the amount of decrease in the forward voltage of the abnormal semiconductor light source is larger than the amount of decrease in the forward voltage of the normal semiconductor light source, so that the determination accuracy is improved. ing.

  Also, the vehicle lamp drive circuits 51a and 51b shown in FIGS. 7A to 7C drive vehicle lamps (not shown), and whether each vehicle lamp is abnormal or normal. Are respectively provided with signal holding units 67a and 67b. The signals held by the signal holding units 67a and 67b are transmitted to the signal receiving unit 55 of the vehicle-side ECU 54, and the signal determination unit 56 determines whether each vehicle lamp is normal or abnormal. And the judgment result is displayed on the signal display part 57, and a driver | operator is alert | reported.

JP 2007-200670 A

  However, the signal holding units 67a and 67b shown in FIG. 7A are supplied from the backup power supplies 68a and 68b after the power supply from the batteries 61a and 61b to the drive circuits 51a and 51b is interrupted and restarted. Without power supply, the signal state cannot be maintained. When the backup power supplies 68a and 68b are not used, it is necessary to store data indicating the signal state in the nonvolatile memories 69a and 69b. Therefore, in any case, since new members for the backup power supplies 68a and 68b and the nonvolatile memories 69a and 69b are required, the manufacturing cost increases and the system becomes complicated.

  In FIG. 7C, the non-volatile memory 58 is provided not in the drive circuits 51a and 51b but in the vehicle side ECU 54, so that the manufacturing cost of the vehicle side ECU 54 increases.

  The signal holding units 67a and 67b shown in FIG. 7B are directly connected to the batteries 61a and 61b without passing through the switches SWa and SWb, and the signals are received by constantly receiving power regardless of whether the switches SWa and SWb are on or off. In order to maintain the state, the battery 61a, 61b becomes exhausted.

  The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a lamp driving circuit that holds a signal indicating an abnormality of a vehicular lamp with an inexpensive and simple circuit configuration. is there.

  A feature of the present invention is a lamp driving circuit for driving a vehicular lamp, wherein the lamp driving circuit controls a lighting state of the vehicular lamp, and operating states of the vehicular lamp and the lighting control unit And a signal output unit for outputting an output signal indicating the operation state determined by the operation determination unit to the outside. The signal output unit includes a signal holding unit that holds the state of the output signal even when the power supply to the lamp driving circuit is interrupted.

  According to the feature of the present invention, the signal holding unit holds the state of the output signal indicating the operation state of the vehicle lamp and the lighting control unit even in the state where the power supply to the lamp driving circuit is cut off, Since the power supply from the backup power source and the nonvolatile memory are not required, the manufacturing cost is reduced and the system is simplified.

  In the feature of the present invention, the operation determination unit outputs a state signal to the signal output unit, and the signal holding unit mechanically contacts the switching state corresponding to the operation state every time the state signal is input from the operation determination unit. And the open / close state of the mechanical contact may be maintained even when the power supply to the lamp driving circuit is interrupted.

  Since the open / close state of the mechanical contact corresponds to the operation state of the vehicle lamp and the lighting control unit, the operation determination unit controls the open / close state of the mechanical contact by outputting a state signal to the signal output unit, The signal holding unit can hold the state of the output signal indicating the operation state of the vehicular lamp and the lighting control unit even in a state where the power supply to the lamp driving circuit is interrupted.

  In the feature of the present invention, the variable resistance whose resistance value corresponding to the operation state is changed according to the state signal input from the operation determination unit by the operation determination unit outputs the state signal to the signal output unit. And the resistance value of the variable resistor may be held even when the power supply to the lamp driving circuit is interrupted.

  By associating the resistance value of the variable resistor with the operation state of the vehicle lamp and the lighting control unit, the operation determination unit controls the resistance value of the variable resistor by outputting a state signal to the signal output unit, and the signal holding unit Can maintain the state of the output signal indicating the operating state of the vehicular lamp and the lighting controller even in the state where the power supply to the lamp driving circuit is interrupted.

  As described above, according to the lamp driving circuit of the present invention, a signal indicating an abnormality of the vehicular lamp can be held with an inexpensive and simple circuit configuration.

It is a block diagram which shows the whole structure of the lamp control system containing the drive circuit for lamps concerning the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the 1st drive circuit 1a for lamps shown in FIG. FIG. 3A is a block diagram illustrating a configuration example of the signal output unit 17a illustrated in FIG. 2, and FIG. 3B is a graph illustrating an operation example of the signal output unit 17a. FIG. 4A to FIG. _4D are graphs showing examples of changes in the states of the switch SWa, the state signal V _sig, and the output signal V _wng . FIG. 5A is a block diagram illustrating a configuration example of the signal output unit 27a according to the second embodiment, and FIG. 5B is a graph illustrating an operation example of the signal output unit 27a. FIGS. _{6A to 6D} are graphs showing examples of changes in the states of the switch SWa, the state signal V _sig, and the output signal V _wng in the second embodiment. FIG. 7A to FIG. 7C are block diagrams showing the overall configuration of a lamp control system including a lamp driving circuit related to the prior art.

Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same portions are denoted by the same reference numerals, and description thereof is omitted.
(First embodiment)
First, an overall configuration of a lamp control system including a lamp drive circuit according to an embodiment of the present invention will be described with reference to FIG. The lamp control system includes a first lamp driving circuit 1a and a second lamp driving circuit 1b that respectively drive a vehicle lamp, and a first lamp driving circuit 1a and a second lamp driving circuit 1b. Vehicle-side ECU 4, connected to the first lamp drive circuit 1a, the second lamp drive circuit 1b, and the vehicle-side ECU 4, wirings 3a, 3b, batteries 11a, 11b, and switch SWa, respectively. , SWb.

  The first lamp driving circuit 1a and the second lamp driving circuit 1b operate by receiving power supply from the battery 11a and the battery 11b, respectively. The power supply from the batteries 11a and 11b is started when the switches SWa and SWb are closed, and is cut off when the switches SWa and SWb are opened. The lamp drive circuits 1a and 1b are provided for each vehicle lamp. In addition, although the case where there are two sets of lamp driving circuits and vehicle lamps is described here, one set or three or more sets may be used.

  In addition, the first lamp driving circuit 1a and the second lamp driving circuit 1b have signal output units 17a and 17b that output output signals indicating whether each vehicle lamp is abnormal or normal, respectively. Prepare. The output signals output from the signal output units 17a and 17b are transferred to the signal receiving unit 5 of the vehicle-side ECU 4 via the wirings 3a and 3b, and the signal determination unit 6 determines whether each vehicle lamp is normal or abnormal. And the judgment result is displayed on the signal display part 7, and it alert | reports to a driver | operator.

  The signal determination unit 6 has an abnormality in at least one of all the lamp driving circuits connected to the vehicle-side ECU 4 or at least one of the vehicle lamps driven by each lamp driving circuit. Is judged as “abnormal”, and when all are normal, it is judged as “normal”. Thereby, the abnormality of the one part member which comprises a lamp control system can be alert | reported.

A configuration example of the first lamp driving circuit 1a shown in FIG. 1 will be described with reference to FIG. The first lamp driving circuit 1a will be described as an example, and the description of the second lamp driving circuit 1b having the same configuration will be omitted. The first lamp driving circuit 1a includes a lighting control unit 15a that controls the lighting state of the vehicle lamp 21a, and the operation states of the vehicle lamp 21a and the lighting control unit 15a are both normal or at least one of them. An operation determination unit 16a that determines whether the operation state is abnormal, and a signal output unit 17a that outputs an output signal _Vwng indicating the operation state of the vehicular lamp 21a and the lighting control unit 15a determined by the operation determination unit 16a. Prepare.

  The vehicular lamp 21a includes a light source composed of a plurality of semiconductor light emitting elements (LEDs) connected to each other, and an optical system member such as a lens or a reflector (not shown). The lighting control unit 15a lights the vehicle lamp 21a by supplying the electric power stored in the battery 11a of FIG. 1 to the light source included in the vehicle lamp 21a. When both the vehicle lamp 21a and the lighting control unit 15a operate normally, the vehicle lamp 21a can perform a normal lighting operation. The vehicular lamp 21a can be configured as various vehicular lamps such as a headlamp, a stop & tail lamp, a fog lamp, and a turn signal lamp.

The operation determination unit 16a determines whether the operation states of the vehicular lamp 21a and the lighting control unit 15a are both normal or at least one of the operation states is abnormal, and a signal output unit according to the determination result The status signal V _sig is output to 17a. Hereinafter, the operation state of the vehicular lamp 21a and the lighting control unit 15a is abbreviated as “operation state”.

The signal output unit 17a includes a signal holding unit 18a that holds the state of the output signal _Vwng even when the switch SWa of FIG. 1 is opened and the power supply to the lamp driving circuit 1a is cut off. The state of the output signal V _wng changes according to the state signal V _sig input to the signal output unit 17a. A wiring 3a is connected to the signal holding unit 18a, and an output signal _Vwng held by the signal holding unit 18a is transferred to the signal receiving unit 5 of the vehicle side ECU 4 through the wiring 3a.

A configuration example of the signal output unit 17a illustrated in FIG. 2 will be described with reference to FIG. The signal output unit 17a of the first lamp driving circuit 1a will be described as an example, and the description of the signal output unit of the second lamp driving circuit 1b having the same configuration will be omitted. The state signal V _sig output from the operation determination unit 16a is input to the signal holding unit 18a. The signal holding unit 18a includes a mechanical contact that switches between open and closed states corresponding to the operation state each time the state signal V _sig is input from the operation determination unit 16a, and supplies power to the first lamp driving circuit 1a. Even in the state where is interrupted, the open / close state of the mechanical contact is maintained.

  The signal holding unit described above can be configured using, for example, a latching relay 18a. One terminal connected to the mechanical contact is grounded, and the other terminal is connected to the vehicle-side ECU 4 via the wiring 3a. Depending on the open / close state of the mechanical contact, the resistance value between the two terminals changes between two values of zero or a low resistance value and an infinite or high resistance value.

For example, if a predetermined voltage is applied from the vehicle side ECU 4 to the wiring 3a and a current _flows, the voltage (V _wng ) of the other terminal changes according to the open / close state of the mechanical contact. Specifically, when the mechanical contact is opened, the voltage (V _wng ) becomes a high potential side voltage, and when the mechanical contact is closed, the voltage (V _wng ) becomes a low potential side voltage.

Since the open / closed state of the mechanical contact is maintained even when the power supply to the first lamp driving circuit 1a is cut off, the signal output unit 17a can supply power to the first lamp driving circuit 1a. Even in the blocked state, the output signal _Vwng indicating the operation state of the vehicular lamp 21a and the lighting control unit 15a can be output to the vehicle-side ECU 4. Further, the vehicle-side ECU 4 applies the predetermined voltage to the wiring 3a so that the operation of the vehicle lamp 21a and the lighting control unit 15a is performed even when the power supply to the first lamp drive circuit 1a is cut off. The output signal V _wng indicating the state can be read out.

For example, between the vehicle side ECU4 the first lamp drive circuits 1a, the output signal state of V _WNG is normal operation state when the low-potential-side voltage, the state of the output signal V _WNG a high potential side voltage At this time, by making an agreement that the operation state is normal, the vehicle-side ECU 4 can determine the normality / abnormality of the vehicular lamp 21a through the state of the output signal _Vwng .

An example of the operation of the signal output unit 17a will be described with reference to FIG. Operation when the pulse signal PS is input from the determination unit 16a as the state signal V _sig, of the output signal V _WNG a pulse signal PS as a trigger state when the state of the output signal V _WNG is, for example, a low-potential-side voltage, such as ground potential Changes to the high potential side voltage. When the pulse signal PS is input from the operation determination unit 16a when the state of the output signal V _wng is the high potential side voltage, the state of the output signal V _wng changes to the low potential side voltage _using the pulse signal PS as a trigger. Thus, every time the pulse signal PS is input as the state signal V _sig from the operation determination unit 16a, the state of the output signal V _wng switches between the low potential side voltage and the high potential side voltage, that is, a latching relay. 18a performs an alternate operation.

A change example of the state of the switch SWa, the state signal V _sig and the output signal V _wng will be described with reference to FIGS. FIG. 4A shows a case where the operation state is normal before and after the determination period Td in which the operation determination unit 16a in FIG. 2 determines the operation state. In the determination period Td after the switch SWa in FIG. 1 changes from the open (off) state to the closed (on) state, the operation determination unit 16a determines the operation state. In FIG. 4A, since the determination results of the operation determination unit 16a are both normal before and after the determination period Td, the pulse signal PS as the state signal V _sig is output as a signal when the switch SWa is in the closed (on) state. Without being input to the unit 17a, the mechanical contact is kept closed before and after the determination period Td, and the state of the output signal _Vwng is maintained at the low potential side voltage. Further, even after the switch SWa is opened, the mechanical contact is kept closed, and the state of the output signal V _wng is held at the low potential side voltage.

FIG. 4B shows a case where there is an abnormality in the operation state before the determination period Td and it is determined that the operation state is normal in the determination period Td. In this case, when the switch SWa is in the closed (on) state, the pulse signal PS as the state signal V _sig is input to the signal output unit 17a, the mechanical contact changes from the open state to the closed state, and the output signal V The state of _wng is switched from the high potential side voltage to the low potential side voltage. Even after the switch SWa is opened, the mechanical contact is kept closed, and the state of the output signal V _wng is maintained at the low potential side voltage.

FIG. 4C shows a case where the judgment results of the motion judgment unit 16a are both abnormal before and after the judgment period Td. In this case, when the switch SWa is in the closed (on) state, the pulse signal PS as the state signal V _sig is not input to the signal output unit 17a, and the mechanical contact is kept open before and after the determination period Td. The state of the output signal V _wng is maintained at the high potential side voltage. Furthermore, even after the switch SWa is opened, the mechanical contact is kept open, and the state of the output signal V _wng is held at the high potential side voltage.

FIG. 4D shows a case where the operation state is normal before the determination period Td and it is determined that the operation state is abnormal in the determination period Td. In this case, when the switch SWa is in the closed (on) state, the pulse signal PS as the state signal V _sig is input to the signal output unit 17a, the mechanical contact changes from the closed state to the open state, and the output signal V The state of _wng is switched from the low potential side voltage to the high potential side voltage. Even after the switch SWa is opened, the mechanical contact is kept open, and the state of the output signal V _wng is held at the high potential side voltage.

  As described above, according to the first embodiment of the present invention, the following operational effects can be obtained.

_{Each time the} state signal V _sig is input from the operation determination unit 16a, the open / close state of the mechanical contact corresponding to the operation state is switched, and the power supply to the first lamp driving circuit 1a is cut off. The signal holding unit 18a holds the open / close state of the mechanical contact. Since the open / close state of the mechanical contact corresponds to the operation state, the operation determination unit 16a controls the open / close state of the mechanical contact by outputting the state signal V _sig to the signal output unit 17a, and the signal holding unit 18a. Can maintain the state of the output signal V _wng indicating the operating state even when the switch SWa is opened and the power supply to the first lamp driving circuit 1a is cut off.

Therefore, the vehicle-side ECU ₄ can read the output signal V _wng indicating the operating state even when the power supply to the first lamp driving circuit 1a is interrupted, as shown in FIG. The power supply from the backup power supplies 68a and 68b and the non-volatile memories 69a and 69b are not required, the manufacturing cost is reduced, and the lamp control system is simplified.

  Further, as shown in FIG. 7C, since it is not necessary to provide the nonvolatile memory 58 in the vehicle side ECU 54, the manufacturing cost of the vehicle side ECU 4 can be kept low. As shown in FIG. 7B, the signal holding units 67a and 67b need not always hold the signal state by receiving the power supply, and the fatigue of the batteries 11a and 11b can be suppressed to extend the life. Can do.

In addition, it is possible to reduce the burden on the alternator when starting the engine. In addition, since the number of parts of the lamp control system is reduced, the weight of the vehicle body can be reduced, leading to an improvement in vehicle fuel efficiency.
(Second Embodiment)
In the second embodiment, a case will be described in which a digital potentiometer 28a is used as a signal holding unit instead of the latching relay 18a of FIG. Other configurations are the same as those of the first embodiment, and the description thereof is omitted.

  As shown in FIG. 5A, the signal output unit 27a according to the second embodiment has a signal holding unit including a digital potentiometer 28a. The digital potentiometer 28a includes a variable resistor Ra whose resistance value changes according to the state signal when the state signal is input from the operation determination unit 16a in a state where the power supply voltage Vcc is supplied. The resistance value of the variable resistor Ra is associated with the operating state in advance. For example, when a threshold value is set and the resistance value of the variable resistor Ra is lower than the threshold value, this corresponds to a case where the operating state is normal, and when the resistance value of the variable resistor Ra is higher than the threshold value. Corresponds to when there is an abnormality in the operating state.

  The signal output unit 27a has a function of holding the resistance value of the variable resistor Ra even when the switch SWa is opened and the power supply to the first lamp driving circuit 1a is cut off. That is, when the power supply to the first lamp driving circuit 1a is cut off, the supply of the power supply voltage Vcc to the digital potentiometer 28a is also cut off. However, the signal output unit 27a also has the variable resistor Ra in this state. It has a function of holding a resistance value.

One terminal connected to the variable resistor Ra is grounded, and the other terminal is connected to the signal receiving unit 5 of the vehicle side ECU 4 via the wiring 3a. If a predetermined voltage is applied to the wiring 3a via the pull-up resistor Rb in the signal receiving unit 5 and a current flows, the voltage dividing ratio between the pull-up resistor Rb and the variable resistor Ra changes according to the resistance value of the variable resistor Ra. Then, the voltage (V _wng ) of the other terminal changes. If the resistance value of the variable resistor Ra is lower than the threshold value, the voltage V _wng becomes a low potential side voltage, and if the resistance value of the variable resistor Ra is higher than the threshold value, the voltage V _wng becomes a high potential side voltage.

Since the resistance value of the variable resistor Ra is maintained even when the power supply to the first lamp driving circuit 1a is interrupted, the signal output unit 27a is configured to supply power to the first lamp driving circuit 1a. Even in the blocked state, the output signal V _wng indicating the operating state can be output to the vehicle-side ECU 4. Further, the vehicle-side ECU ₄ reads the output signal V _wng indicating the operating state even when the power supply to the first lamp driving circuit 1a is interrupted by applying a predetermined voltage to the wiring 3a. Can do.

With reference to FIG.5 (b), the operation example of the signal output part 27a is demonstrated. First, consider the case where the supply of the power supply voltage Vcc to the digital potentiometer 28a is started when the state of the output signal _Vwng is a low potential side voltage such as a ground potential. In this case, when the state signal DS for making the resistance value of the variable resistor Ra higher than the threshold value is written from the operation determination unit 16a, the resistance value of the variable resistor Ra becomes higher than the threshold value, and the output signal V _wng Changes to a high potential side voltage.

On the other hand, consider the case where the supply of the power supply voltage Vcc to the digital potentiometer 28a is started when the state of the output signal _Vwng is, for example, a high potential side voltage. In this case, when the state signal DS for lowering the resistance value of the variable resistor Ra below the threshold value is written from the operation determination unit 16a, the resistance value of the variable resistor Ra becomes lower than the threshold value, and the output signal V _wng Changes to a low potential side voltage. Thus, the resistance value of the variable resistor Ra can be changed according to the data content of the state signal input from the operation determination unit 16a.

A change example of the state of the switch SWa, the state signal V _sig and the output signal V _wng will be described with reference to FIGS. FIG. 6A shows a case where the operating state is normal before and after the determination period Td. In the determination period Td after the switch SWa in FIG. 1 changes from the open (off) state to the closed (on) state, the operation determination unit 16a determines the operation state. In FIG. 6A, since the determination result of the operation determination unit 16a is normal before and after the determination period Td, the state signal is not input to the signal output unit 27a when the switch SWa is in the closed (on) state. Before and after the determination period Td, the resistance value of the variable resistor Ra is maintained lower than the threshold value, and the state of the output signal V _wng is maintained at the low potential side voltage. Moreover, even after the switch SWa is open, the resistance value of the variable resistor Ra is maintained lower than the threshold, the state of the output signal V _WNG is held at a low potential side voltage.

FIG. 6B shows a case where there is an abnormality in the operation state before the determination period Td and it is determined that the operation state is normal in the determination period Td. In this case, when the switch SWa is in the closed (on) state, the state signal DS is input to the signal output unit 27a, the resistance value of the variable resistor Ra changes from a state higher than the threshold value to a lower state, and the output signal V The state of _wng is switched from the high potential side voltage to the low potential side voltage. Even after the switch SWa is opened, the resistance value of the variable resistor Ra remains lower than the threshold value, and the state of the output signal V _wng is held at the low potential side voltage.

FIG. 6C shows a case where the judgment results of the motion judgment unit 16a are both abnormal before and after the judgment period Td. In this case, when the switch SWa is in the closed (on) state, the state signal DS is not input to the signal output unit 27a, and the resistance value of the variable resistor Ra is maintained higher than the threshold before and after the determination period Td. The state of the output signal V _wng is maintained at the high potential side voltage. Further, even after the switch SWa is opened, the resistance value of the variable resistor Ra remains higher than the threshold value, and the state of the output signal V _wng is held at the high potential side voltage.

FIG. 6D shows a case where the operation state is normal before the determination period Td and it is determined that the operation state is abnormal in the determination period Td. In this case, when the switch SWa is in the closed (on) state, the state signal DS is input to the signal output unit 27a, the resistance value of the variable resistor Ra changes from a state lower than the threshold value to a high state, and the output signal V The state of _wng is switched from the low potential side voltage to the high potential side voltage. Even after the switch SWa is opened, the resistance value of the variable resistor Ra remains higher than the threshold value, and the state of the output signal V _wng is held at the high potential side voltage.

  As described above, according to the second embodiment of the present invention, the following operational effects can be obtained.

The signal is held even when the resistance value of the variable resistor Ra corresponding to the operation state changes according to the state signal input from the operation determination unit 16a and the power supply to the first lamp driving circuit 1a is cut off. The unit 28a holds the resistance value of the variable resistor Ra. Since the resistance value of the variable resistor Ra corresponds to the operation state, the operation determination unit 16a controls the resistance value of the variable resistor Ra by outputting a state signal to the signal output unit 27a, and the signal holding unit 28a Even in the state where the switch SWa is opened and the power supply to the first lamp driving circuit 1a is cut off, the state of the output signal _Vwng indicating the operation state can be maintained.

  Therefore, also in the lamp drive circuit according to the second embodiment, the same effect as in the first embodiment can be obtained.

  As described above, the present invention has been described in terms of two embodiments, but it should not be understood that the discussion and drawings that form part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. That is, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters according to the scope of claims reasonable from this disclosure.

1a First lamp driving circuit (lamp driving circuit)
1b Second lamp driving circuit (lamp driving circuit)
3a, 3b Wiring 4 Vehicle side ECU
DESCRIPTION OF SYMBOLS 5 Signal receiving part 6 Signal judgment part 7 Signal display part 11a, 11b Battery 15a Lighting control part 16a Operation judgment part 17a, 27a Signal output part 18a Latching relay (signal holding part)
21a Vehicle lamp 28a Digital potentiometer (signal holding unit)
28a signal holding section DS state signal PS pulse signal Ra variable resistor Rb pullup resistor SWa, SWb switch Td determination period V _sig status signal V _WNG output signal Vcc supply voltage

Claims (3)

A lamp driving circuit for driving a vehicle lamp,
A lighting control unit for controlling the lighting state of the vehicular lamp;
An operation determination unit for determining whether the operation state of both the vehicle lamp and the lighting control unit is normal or at least one of the operation states is abnormal;
A signal output unit that outputs an output signal indicating the operation state determined by the operation determination unit to the outside;
The lamp drive circuit according to claim 1, wherein the signal output unit includes a signal holding unit that holds the state of the output signal even when power supply to the lamp drive circuit is interrupted. The operation determination unit outputs a status signal to the signal output unit,
The signal holding unit includes a mechanical contact that switches an open / close state corresponding to the operation state each time the state signal is input from the operation determination unit, and power supply to the lamp driving circuit is cut off. The lamp driving circuit according to claim 1, wherein the open / close state of the mechanical contact is maintained even in a closed state. The operation determination unit outputs a status signal to the signal output unit,
The signal holding unit includes a variable resistor that changes a resistance value corresponding to the operation state in accordance with the state signal input from the operation determination unit, and power supply to the lamp driving circuit is interrupted. The lamp driving circuit according to claim 1, wherein the resistance value of the variable resistor is maintained even in a state where the lamp is in a lit state.

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