JP2018122742A - Light source drive device, and vehicular lighting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a light source drive device to appropriately execute temperature derating.SOLUTION: The light source drive device includes: a first temperature sensor arranged near a light source element; a second temperature sensor arranged at a position at which influence by heat generation from the light source element is smaller than that in the first temperature sensor; and a voltage conversion part for receiving direct current voltage to perform voltage conversion and supplying driving current to the light source element. The driving current from the voltage conversion part is controlled by using temperature information detected by the first temperature sensor and temperature information detected by the second temperature sensor.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light source driving device and a vehicular lamp, and more particularly to a technique for controlling driving current to a light source according to temperature.

In a vehicular lamp, it is common to use a light source such as a laser diode or an LED (Light Emitting Diode). These vehicle lamps protect the light source from heat at high temperatures, and control the drive current to the light source by temperature in order to suppress COD (catastrophic optical damage) due to increased light intensity at low temperatures. Some of them do so-called temperature derating.
For example, laser diodes and LEDs have a temperature characteristic in which the amount of emitted light is negative, and the amount of light increases as the temperature decreases. For this reason, the drive current value is reduced in consideration of thermal effects at high temperatures, and the drive current value is reduced to suppress an increase in the amount of emitted light even at low temperatures.
The following Patent Documents 1 and 2 describe a vehicular lamp provided with a lighting circuit that performs temperature derating.

JP 2006-201341 A JP, 2006-192512, A

In order to perform temperature derating, information on the temperature of the light source, that is, the junction temperature of the chip is required. Therefore, a temperature sensor is disposed in the vicinity of the light source element so as to detect the light source temperature. In the lighting circuit that supplies the drive current to the light source element, the current value of the drive current is adjusted based on the temperature information detected by the temperature sensor.
However, since there is a thermal resistance between the junction of the light source and the temperature sensor, the temperature sensor detects a temperature that is lower than the junction temperature by a temperature drop (ΔT) due to the thermal resistance.

Considering this, the current control may be performed on the lighting circuit side in anticipation of ΔT and assuming that a value higher by ΔT than the detected value Ts of the temperature sensor is the actual junction temperature. That is, the detected value Ts may be corrected by ΔT.
However, the value of ΔT is not always constant. Immediately after lighting, the substantial ΔT is a small value. In particular, ΔT = 0 at the start of lighting in a cold start.
For this reason, if the detection value Ts is simply corrected by ΔT, the derating is too effective at high temperatures, reducing the current more than necessary, reducing the amount of light, and sufficient derating at low temperatures. In some cases, the amount of light cannot be sufficiently suppressed.

  Accordingly, an object of the present invention is to realize a temperature derating based on a more appropriate temperature detection in consideration of a situation of a decrease (ΔT) in a detection temperature due to a thermal resistance.

The light source driving device according to the present invention includes a first temperature sensor arranged in the vicinity of the light source element, and a second temperature arranged at a position where the influence of heat generated from the light source element is smaller than the first temperature sensor. A sensor; a voltage converter that receives a direct current voltage to perform voltage conversion and supplies a drive current to the light source element; temperature information detected by the first temperature sensor; and a temperature information detected by the second temperature sensor. And a controller that controls the drive current from the voltage converter using the temperature information.
In order to protect the light source, when performing temperature derating that controls the drive current according to the light source temperature, the first temperature sensor in the vicinity of the light source detects the temperature change of the light source element. Detection information of the second temperature sensor at a position not received is also used.

In the light source driving device, the second temperature sensor includes a light source substrate on which the light source element and the first temperature sensor are disposed, and a lighting circuit substrate on which the voltage conversion unit and the control unit are disposed. Is considered to be disposed on the lighting circuit board.
That is, the first temperature sensor and the second temperature sensor are arranged on different substrates.

In the light source driving device, the control unit corrects the temperature information detected by the first temperature sensor using the temperature information detected by the second temperature sensor, and corrects the temperature information. It is conceivable to control the drive current from the voltage converter according to the above.
The temperature information detected by the first temperature sensor detects a temperature ΔT lower than the junction temperature of the light source by the thermal resistance between the junction of the laser diode and the temperature sensor. Derating may be performed assuming this, but ΔT is not constant. In particular, ΔT = 0 at the start of lighting in a cold start. This makes the derating control inaccurate. Therefore, correction by ΔT is performed using detection information of the second temperature sensor.

In the light source driving device, the control unit detects temperature information detected by the first temperature sensor, temperature information detected by the first temperature sensor, and temperature information detected by the second temperature sensor. It is conceivable to correct the temperature information so as to be high according to the difference in temperature information.
Specifically, the correction is performed on the assumption that the first temperature sensor detects a temperature lower than the junction temperature of the light source by ΔT and that ΔT fluctuates after the start of lighting.

The light source element driven by the light source driving device is a laser light source element, and the light source driving device applies to the laser light source element as the temperature detected by the second temperature sensor is lower at a low temperature of a predetermined temperature or lower. It is conceivable to reduce the driving current.
A laser light source element, for example, a laser diode, has a light emitting point area much smaller than that of an LED, and care must be taken to prevent COD due to an increase in the amount of light. In particular, it is desirable to take safer measures than necessary for the increase in light intensity at low temperatures. Therefore, so-called low temperature derating is performed.

  The vehicular lamp according to the present invention includes a light source element and the light source driving device described above.

  According to the present invention, temperature derating can be performed by appropriately detecting the light source temperature. Therefore, it is possible to realize temperature derating that functions sufficiently for protecting the light source.

It is a block diagram of the vehicle lamp of the 1st Embodiment of this invention. It is explanatory drawing of the temperature derating of embodiment. It is a circuit diagram of the temperature sensor and temperature information correction part of an embodiment. It is a block diagram of the vehicle lamp of 2nd Embodiment.

<First Embodiment>
Hereinafter, a light source driving device and a vehicle lamp according to an embodiment will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a vehicular lamp 1 according to a first embodiment configured to include a lighting circuit 2 and a light source unit 3.
The vehicular lamp 1 can be suitably applied to various lamps such as a vehicle headlamp, a turn signal lamp, and a backlight.
In addition, the structure remove | excluding the light source element (laser diode 31) from the vehicle lamp 1 becomes embodiment of the light source drive device of this invention.

The lighting circuit 2 in the vehicular lamp 1 is composed of various electronic components arranged on a lighting circuit board, for example.
The light source unit 3 is formed having one or a plurality of light source elements arranged on a light source substrate. Here, an example in which a laser diode 31 is used as the light source element is used. However, an LED may be used as the light source element.

The lighting circuit 2 is configured to receive power supply from the vehicle battery 90 between the terminals 41 and 42.
A switch 91 is inserted between the positive terminal of the battery 90 and the terminal 41 of the lighting circuit 2, and lighting / extinguishing of the vehicular lamp 1 is controlled by turning on / off the switch 91. The terminal 42 of the vehicular lamp 1 is connected to the negative electrode side of the battery 90 through a ground point.
Although not shown, the lighting circuit 2 may be configured to be communicably connected to an ECU (Electronic Control Unit) that comprehensively performs electrical control provided on the vehicle side. In this case, a configuration is also conceivable in which the power supply voltage line and the ground line from the battery 90 are connected to the terminals 41 and 42 via the ECU so that the ECU can control the power supply to the lighting circuit 2.

  In the light source unit 3 in the vehicular lamp 1, a laser diode 31 is connected between the terminals 53 and 54. The laser diode 31 is driven to emit light by being supplied with a drive current Idr controlled at a constant current from the lighting circuit 2.

In the light source section 3, a thermistor (temperature detection resistor) as the first temperature sensor TH1 is disposed in the vicinity of the laser diode 31. That is, the first temperature sensor TH1 is mounted on the same light source substrate as the laser diode 31 and at a position close to the laser diode 31.
The first temperature sensor TH1 is connected between the terminals 55 and 56.

  The lighting circuit 2 includes a DC / DC converter 21, a voltage generation unit 22, and a control unit 23. Here, the control unit 23 is used as a general term for the converter drive unit 24, the temperature derating circuit 25, and the temperature information correction unit 26 in the sense of a circuit system that performs output current control for the DC / DC converter 21.

  The voltage generation unit 22 generates an operating voltage Vcc used in a circuit system such as the control unit 23 from the input voltage and supplies it to each unit.

The DC / DC converter 21 is a voltage converter that supplies a drive current Idr to the laser diode 31 of the light source unit 3. The DC / DC converter 21 receives the direct current voltage from the battery 90 to perform voltage conversion, and generates an output voltage Vdr between the terminals 43 and 44.
The terminals 43 and 53 and the terminals 44 and 54 are connected. Accordingly, the drive current Ids based on the output voltage Vdr appearing on the output side of the DC / DC converter 21 flows in the order of terminal 43 → terminal 53 → laser diode 31 → terminal 54 → terminal 44.
The DC / DC converter 21 is, for example, a switching regulator. Depending on the relationship between the light source configuration of the light source unit 3 (forward effect voltage and the like) and the power supply voltage by the battery 90, any of a step-up type, a step-down type, and a step-up / step-down type can be considered.

The converter drive unit 24 performs the voltage conversion operation of the DC / DC converter 21 and performs constant current control of the drive current Idr.
For example, the converter drive unit 24 compares the current value of the drive current Idr with the target current value based on the detection signal SId of the output (drive current Idr) of the DC / DC converter 21, and the PWM control signal Spwm corresponding to the difference. Is generated. The PWM control signal Spwm is supplied to the switching element of the DC / DC converter 21 to control the voltage conversion operation, thereby realizing a constant current output.

  A derating control signal Std is supplied from the temperature derating circuit 25 to the converter drive unit 24. The converter drive unit 24 implements temperature derating by increasing or decreasing the target current value based on the derating control signal Std. The temperature derating circuit 25 outputs a derating control signal Std having a value corresponding to the detected temperature value Ts of the detected laser diode 31 (voltage value Vs corresponding to the detected value Ts).

For this temperature derating, in addition to the first temperature sensor TH1 on the light source board described above, the second temperature sensor TH2 is mounted on the lighting circuit board. The second temperature sensor TH2 is a thermistor, for example, like the first temperature sensor TH1.
The second temperature sensor TH2 is arranged so that the temperature change of the laser diode 31 as the light source element does not affect the detected temperature. Or at least 2nd temperature sensor TH2 is arrange | positioned in the position where the influence by the heat_generation | fever from the laser diode 31 is smaller than 1st temperature sensor TH1.
In this example, the second temperature sensor TH2 is arranged not on the light source board but on the lighting circuit board in order to be less susceptible to the temperature change of the laser diode 31.

The terminal 45 and the terminal 46 of the lighting circuit board are connected to the terminal 55 and the terminal 56 of the light source board, respectively. Therefore, the resistor R1 on the lighting circuit board and the first temperature sensor TH1 on the light source board are connected in series between the voltage Vcc line and the ground. The voltage divided by the resistor R1 and the first temperature sensor TH1 is input to the temperature information correction unit 26 as a detection voltage V1 corresponding to the temperature detected by the first temperature sensor TH1.
The terminals 43, 44, 45, and 46 of the lighting circuit board and the terminals 53, 54, 55, and 56 of the light source board are inter-board wirings and are connected by a harness 80 having four transmission paths.

  The resistor R2 and the second temperature sensor TH2 are connected in series between the voltage Vcc line and the ground, and the divided voltage by the resistor R2 and the second temperature sensor TH2 is a detected voltage V2 corresponding to the detected temperature of the second temperature sensor TH2. Input to the temperature information correction unit 26.

  The temperature information correction unit 26 generates a voltage value Vs corresponding to the temperature detection value Ts based on the detection voltages V1 and V2.

Here, temperature derating will be described.
FIG. 2A shows an example of a derating curve. The horizontal axis represents temperature, and the vertical axis represents the current value flowing through the light source element.
In this case, when the temperature is higher than the temperature T2, the current is decreased according to the temperature. This is to protect the light source from heat.

Further, when the temperature is lower than the temperature T1, the current is decreased according to the temperature. This is to suppress COD due to an increase in the amount of emitted light at a low temperature. In particular, prevention of COD is important for maintaining the reliability of the vehicular lamp.
FIG. 2B shows the relationship between the temperature of the laser diode 31 and the amount of light. As shown in the drawing, the amount of light emitted from the laser diode 31 decreases as the temperature rises. On the other hand, since the amount of emitted light increases at low temperatures, temperature derating is particularly important at low temperatures in order to prevent COD due to an increase in the amount of light. Actually, as indicated by a one-dot chain line in FIG. 2B, it is desirable that the amount of light is substantially constant when the temperature is equal to or lower than T1. For this purpose, as shown in FIG. 2C, the current value is decreased according to the temperature in a region below the temperature T1.

As described above, the temperature derating is performed in order to suppress the heat at a high temperature and to prevent the light amount from increasing excessively at a low temperature.
Here, conventionally, it is usual to use only the first temperature sensor TH1 in the vicinity of the light source element. However, as described above, the detected temperature becomes lower than the junction temperature by ΔT due to the influence of the thermal resistance, and ΔT Since the value of fluctuates from the start of lighting, there has been a case where optimum derating cannot be realized.
Therefore, in the present embodiment, in addition to the first temperature sensor TH1, as described above, the second temperature sensor TH2 that is not influenced (or has a small effect) by the heat change of the light source element is used. In order to obtain the temperature detection value Ts, the detection values (detection voltages V1, V2) by the first temperature sensor TH1 and the second temperature sensor TH2 are used. Specifically, when the difference between the detection voltages V1 and V2 is small (that is, when ΔT is small), the correction value from the detection voltage V1 is reduced to generate the voltage value Vs as the detection value, and the detection voltages V1, When the difference in V2 is large (that is, when ΔT is large), the correction amount from the detection voltage V1 is increased so that the voltage value Vs as the detection value can be generated.

A configuration example of the temperature information correction unit 26 is shown in FIG.
As described above, the resistor R1 and the first temperature sensor TH1 (thermistor) are connected in series between the voltage Vcc line and the ground, and the resistor R2 and the second temperature sensor TH2 (thermistor) are connected in series.
Here, the thermistors as the first and second temperature sensors TH1 and TH2 are NTC (negative temperature coefficient) thermistors, which are elements whose resistance value decreases as the temperature increases. Accordingly, the detection voltages V1 and V2 decrease as the temperature increases.
The thermistors as the first and second temperature sensors TH1 and TH2 have the same characteristics, and the resistors R1 and R2 have the same resistance value.

The temperature information correction unit 26 includes buffer amplifiers 61 and 62, a differential amplification amplifier 63, an amplifier 64, resistors R3, R4, R5, R6, R7, R8, and an NPN transistor 65.
The detection voltage V1 is input to the buffer amplifier 61, and the detection voltage V2 is input to the buffer amplifier 62.
Differential amplification of the outputs of the buffer amplifiers 61 and 62 is performed by the differential amplification amplifier 63 and the resistors R3, R4, R5, and R6. That is, the differential voltage value (V2−V1) between the detection voltages V1 and V2 is obtained as the output of the differential amplifier 63.
When the light source element (laser diode 31) is turned on, the temperature in the vicinity of the light source becomes higher, so that normally V2> V1. Therefore, the voltage value (V2−V1) that is the output of the differential amplifier 63 is estimated as the value of ΔT (the temperature decrease due to the thermal resistance between the laser diode 31 and the first temperature sensor TH1). This voltage value (V2-V1) is input to the amplifier 64.

A current source circuit is formed by the amplifier 64, the transistor 65, and the resistor R7. That is, the output terminal of the amplifier 64 is also connected to the base of the transistor 64, and the conduction of the transistor 65 is controlled by the output current of the amplifier 64.
The collector of the transistor 65 is connected to the output terminal 66, and the emitter is connected to the ground via the resistor R7.
Here, the output voltage of the buffer amplifier 61 appears at the output terminal 66 as the voltage value Vs (that is, the temperature detection value Ts) via the resistor R8. From the output line (output terminal 66) of this voltage value Vs to the ground. The transistor 65 is configured to draw the correction current Ih.
That is, the voltage value Vs is lowered according to the correction current amount. Since the voltage value Vs is originally a detected voltage by the first temperature sensor TH1 as an NTC thermistor, the voltage value Vs becomes information indicating a higher temperature as the voltage value is lower. Therefore, controlling the correction current Ih to decrease the voltage value Vs results in a detection value Ts in which the temperature detection value by the first temperature sensor TH1 is corrected to a temperature higher by ΔT.

Specifically, if the voltage value (V2−V1) corresponding to ΔT is zero, the transistor 65 is turned off, and the voltage value Vs appearing at the output terminal 66 is not corrected and is directly applied to the temperature derating circuit 25 in the next stage. Is output.
The transistor 65 allows a correction current Ih corresponding to the voltage value (V2-V1) to flow between the collector and the emitter. Therefore, the current value of the correction current Ih drawn by the transistor 65 increases as the voltage value (V2−V1) corresponding to ΔT increases. Therefore, if ΔT is small, the correction amount of the voltage value Vs is small, and if ΔT is large, the correction amount of the voltage value Vs is large.
That is, ΔT is estimated as a voltage value (V2−V1), and the detected temperature of the first temperature sensor TH1 is lower than the junction temperature by the estimated ΔT, and temperature detection indicating a high temperature corresponding to ΔT. Correction is made to the value Ts (the voltage value Vs is lowered by an amount corresponding to ΔT).

  By correcting the detection value Ts (voltage value Vs) by the temperature information correction unit 26 in this way, temperature information in which ΔT due to thermal resistance is canceled can be supplied to the temperature derating circuit 25 in the next stage. Therefore, appropriate temperature derating control can be performed according to the detected value Ts regardless of the change in ΔT.

<Second Embodiment>
The configuration of the vehicular lamp 1 according to the second embodiment is shown in FIG. In addition, the same part as FIG. 1 attaches | subjects the same code | symbol, and avoids duplication description.
The configuration of FIG. 4 is an example in which a portion corresponding to the control unit 23 of FIG.

The detection voltages V1, V2 detected by the first temperature sensor TH1 and the second temperature sensor TH2 are taken in as digital data by the A / D conversion input ports 74, 75 of the microcomputer 70, respectively.
The microcomputer 70 is provided with a temperature information correction calculation unit 73, a temperature derating calculation unit 72, and a converter drive function 71 by a software program. Calculations are performed to realize functions similar to those of the temperature information correction unit 26, the temperature derating circuit 25, and the converter driving unit 24 of FIG.
Accordingly, the temperature information correction calculation unit 73 performs a calculation for correcting the detected temperature V1 according to the difference (V2−V1) in accordance with the digital data input of the detected temperatures V1 and V2, and generates a corrected detection value Ts. The temperature derating calculation unit 72 performs calculation for calculating the derating control signal Std using the detection value Ts from the temperature information correction calculation unit 73. The converter drive function 71 controls the operation of the DC / DC converter 21 according to the derating control signal Std, that is, adjusts the drive current Ids.

In this way, the vehicular lamp 1 that performs appropriate temperature derating can be realized even if the microcomputer 70 is used.
Thereby, the mounting of the lighting circuit 2 can be simplified. In particular, in the case of a vehicular lamp 1 of a type that implements a microcomputer for converter drive control, the function of the temperature information correction calculation unit 73 may be added by a software program, and detection temperature correction for temperature derating control is performed. Implementation of functions to be performed is easy.

<Effects and Modifications of Embodiment>
According to the light source driving device mounted on the vehicular lamp 1 described as the first and second embodiments, the following effects can be obtained.
The light source driving apparatus according to the embodiment includes a first temperature sensor TH1 disposed in the vicinity of the laser diode 31 that is a light source element, and a first temperature sensor that is disposed at a position where the influence of heat generated from the light source element is smaller than the first temperature sensor TH1. It has two temperature sensors TH2. The DC / DC converter 21 (voltage conversion unit) that receives the DC voltage and converts the voltage to supply the drive current Idr to the laser diode 31, the temperature information detected by the first temperature sensor TH1, and the second temperature sensor TH2 Is provided with a control unit 23 (or a microcomputer 70) for controlling the drive current Idr from the DC / DC converter 21 using the temperature information detected in (1).
The temperature information detected by the first temperature sensor TH1 may detect a temperature lower than the junction temperature due to the thermal resistance between the junction of the laser diode 31 and the temperature sensor, but the second temperature sensor TH2 is also used. To obtain appropriate temperature information.
In addition, although the laser diode 31 was mentioned as a light source element, this invention is applicable also when using other light source elements, such as LED, for example.

In the embodiment, the light source board on which the laser diode 31 and the first temperature sensor TH1 are arranged, and the lighting circuit board on which the DC / DC converter 21 and the control unit 23 (or the microcomputer 70) are arranged, the second temperature is provided. The sensor TH2 is an example disposed on the lighting circuit board.
By disposing the second temperature sensor TH2 on the lighting circuit board, the second temperature sensor TH2 can be sufficiently separated from the laser diode 31 so that the temperature change of the laser diode 31 does not affect the detected temperature. That is, no special structure is required for the arrangement of the second temperature sensor TH2.
Further, since the second temperature sensor TH2 is mounted on the lighting circuit board 2, the connection between the second temperature sensor and the temperature information correction unit 26 can be made by pattern wiring on the board. That is, it can be avoided that the number of wires by the harness 80 between the light source substrate and the lighting circuit substrate is increased by providing the second temperature sensor TH2. In other words, even if the second temperature sensor TH2 is provided, the inter-board wiring does not become complicated.
Further, it is not necessary to increase the area of the light source substrate in consideration of the second temperature sensor TH2. This means that the degree of freedom of design around the light source arrangement of the vehicular lamp is not lowered by an increase in the board area, which is advantageous in design.
Note that the second temperature sensor TH2 is desirably arranged at a position as far as possible from the DC / DC converter 21 on the lighting circuit board. This is to avoid the influence of heat generated by the DC / DC converter 21.
On the other hand, it is also possible to mount the second temperature sensor TH2 on the light source substrate. In that case, it is desirable to arrange the second temperature sensor TH2 at a location sufficiently away from the laser diode 31.
The second temperature sensor TH2 may be disposed on a third substrate different from the lighting circuit substrate and the light source substrate. For example, a sensor substrate may be provided separately.

In the embodiment, the temperature information detected by the first temperature sensor TH1 is corrected using the temperature information detected by the second temperature sensor TH2, and from the DC / DC converter 21 according to the corrected temperature information. The configuration for controlling the drive current Idr of the current is shown.
Appropriate temperature information used for derating can be obtained by correcting the temperature information of the first temperature sensor TH1 using the temperature information of the second temperature sensor TH2. Thereby, derating becomes accurate and appropriate light source protection can be realized. Also

More specifically, in the embodiment, the temperature information (V1) detected by the first temperature sensor TH1 is calculated using the temperature information detected by the first temperature sensor TH1 and the temperature information detected by the second temperature sensor TH2. The correction is made so that the temperature information becomes high according to the difference (V2−V1).
The temperature information detected by the first temperature sensor TH1 may detect a temperature that is ΔT lower than the junction temperature of the light source due to the thermal resistance between the junction of the laser diode 31 and the temperature sensor. ΔT is not constant. Therefore, correction for ΔT is performed using detection information of the second temperature sensor TH2. Specifically, the correction is performed assuming that the first temperature sensor TH1 detects a temperature that is lower than the junction temperature of the light source by ΔT, and that ΔT fluctuates after the start of lighting.
ΔT is zero at the start of lighting. Then, ΔT increases as lighting continues. In other words, the temperature detected by the first temperature sensor TH1 detects the temperature without the thermal resistance at the start of lighting, but detects the temperature lower than the junction temperature by ΔT due to the influence of the thermal resistance due to the continued lighting.
The difference between the detected temperatures of the first temperature sensor TH1 and the second temperature sensor TH2 is substantially zero at the start of lighting. On the other hand, after the lighting is started, the difference between the detected temperatures of the first temperature sensor TH1 and the second temperature sensor TH2 increases.
Therefore, by increasing the detected temperature by the first temperature sensor TH1 according to the difference between the detected temperatures of the first temperature sensor TH1 and the second temperature sensor TH2 (in the above example, the value of the voltage Vs is decreased), ΔT The detected temperature information corrected so as not to be affected by the fluctuation can be obtained.
Accordingly, appropriate temperature information used for derating can be obtained, and appropriate light source protection can be realized by accurate derating.
In particular, the drive current can be appropriately derated in a transient state from lighting of the light source to thermal equilibrium.

In the embodiment, the light source element is the laser diode 31, and an example in which the drive current Idr applied to the laser diode 31 is decreased as the temperature detected by the second temperature sensor TH2 is lower at a low temperature equal to or lower than the predetermined temperature T1. It was.
Laser diodes have a very small emission point area compared to LEDs, and care must be taken to prevent COD due to an increase in the amount of light. In particular, it is desirable to take safer measures than necessary for the increase in light intensity at low temperatures.
In the case of the embodiment, by performing derating by optimizing the detection temperature, it is possible to appropriately reduce the drive current and reduce the amount of light at a low temperature, which is very effective in suppressing COD. Therefore, a more reliable vehicular lamp can be realized.

In the embodiment, the example of the vehicular lamp 1 has been described. However, the light source driving apparatus of the present invention can be applied as a light source driving apparatus for various lamps that drive a light source.
For example, the light source driving device of the present invention can also be used for road lighting lamps, outdoor lighting lamps, indoor lighting lamps, and the like. Illumination by light quantity can be realized.
Further, according to the present invention, the current of the light source can be controlled with high accuracy even in a lamp having a layout restriction that there is no space for disposing the lighting circuit on the same substrate or in the vicinity of the light source. There is also an effect that the degree of design freedom can be increased.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle lamp, 2 ... Lighting circuit, 3 ... Light source part, 21 ... DC / DC converter, 23 ... Control part, 24 ... Converter drive part, 25 ... Temperature derating circuit, 26 ... Temperature information correction part, 31 ... Laser diode, 70 ... microcomputer, TH1 ... first temperature sensor, TH2 ... second temperature sensor

Claims (6)

A first temperature sensor disposed in the vicinity of the light source element;
A second temperature sensor disposed at a position where the influence of heat generated from the light source element is smaller than the first temperature sensor;
A voltage conversion unit that receives a DC voltage to perform voltage conversion and supplies a driving current to the light source element;
A light source drive comprising: temperature information detected by the first temperature sensor; and a control unit that controls drive current from the voltage conversion unit using the temperature information detected by the second temperature sensor. apparatus. A light source substrate on which the light source element and the first temperature sensor are disposed;
A lighting circuit board on which the voltage conversion unit and the control unit are arranged;
The light source driving device according to claim 1, wherein the second temperature sensor is disposed on the lighting circuit board. The control unit corrects the temperature information detected by the first temperature sensor using the temperature information detected by the second temperature sensor, and the voltage conversion unit according to the corrected temperature information. The light source driving device according to claim 1, wherein the driving current from the light source is controlled. The controller is high in temperature information detected by the first temperature sensor according to a difference between temperature information detected by the first temperature sensor and temperature information detected by the second temperature sensor. The light source driving device according to claim 3, wherein the light source driving device corrects the temperature information. The light source element is a laser light source element;
5. The drive current applied to the laser light source element is decreased as the temperature detected by the second temperature sensor is lower at a low temperature that is equal to or lower than a predetermined temperature. 6. Light source drive device.   A vehicle lamp comprising a light source element and the light source driving device according to any one of claims 1 to 5.

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