lamps

Abstract

To provide a lighting fixture capable of suppressing heat generation and preventing breakage of electronic components.SOLUTION: A lighting fixture comprises: a power supply circuit that generates a predetermined voltage on the basis of a power supply voltage; a light source that includes a plurality of light-emitting elements and an adjustment unit adjusting a drive current flowing in each of the plurality of light-emitting elements, and that uses the predetermined voltage as a power supply; a temperature detection circuit for detecting a temperature, provided on a substrate on which the power supply circuit is arranged; and a control unit that controls the adjustment unit on the basis of a first signal from the temperature detection circuit and a second signal indicating lighting conditions of the plurality of light-emitting elements.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a lighting fixture. [Background technology]

[0002] For example, as a lighting fixture (vehicle lighting fixture) used in a vehicle, there is known an adaptive driving beam (ADB) headlamp that arranges multiple light-emitting elements in a row and variably controls the light distribution of the light distribution pattern by switching on and off each light-emitting element (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-107743 Summary of the Invention [Problem to be solved by the invention]

[0004] When multiple light-emitting elements are connected in parallel, it is necessary to supply a current (drive current) according to the number of light-emitting elements to be turned on. Therefore, when a large number of light-emitting elements are provided, a large current may be required, which may result in large heat generation and, as a result, may lead to thermal destruction of electronic components.

[0005] The present invention has been made in view of the above-mentioned problems of the prior art, and its object is to provide a lighting fixture that can suppress heat generation and prevent damage to electronic components. [Means for solving the problem]

[0006] The main invention that solves the above-mentioned problems is a lighting fixture that includes a power supply circuit that generates a predetermined voltage based on a power supply voltage, a plurality of light-emitting elements, and an adjustment unit that adjusts the drive current flowing through each of the plurality of light-emitting elements, and is equipped with a light source that uses the predetermined voltage as its power source, a temperature detection circuit that is provided on a substrate on which the power supply circuit is arranged and that detects temperature, and a control unit that controls the adjustment unit based on a first signal from the temperature detection circuit and a second signal that indicates the lighting conditions of the plurality of light-emitting elements. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a lighting fixture that can suppress heat generation and prevent damage to electronic components. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram showing an example of a system configuration including a vehicle lamp 1 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating a configuration example of an ADB unit 5. [Figure 3] FIG. 2 is a diagram showing a configuration of a detection circuit 50 in the first embodiment. [Figure 4] 4A to 4C are diagrams for explaining the relationship between the temperature information of the temperature detection circuit 51 and the temperature derating. [Figure 5] FIG. 10 is a diagram showing a configuration of a detection circuit 150 in a second embodiment. [Figure 6] FIG. 10 is a diagram showing the configuration of a detection circuit 250 in a third embodiment. [Figure 7] FIG. 10 is a diagram showing the configuration of a detection circuit 350 in a fourth embodiment. [Figure 8] 8A to 8D are diagrams for explaining the relationship between the temperature information of the temperature detection circuit 55 and the temperature derating. DETAILED DESCRIPTION OF THE INVENTION

[0009] At least the following matters will become clear from the description of this specification and the accompanying drawings.

[0010] =====First Embodiment====== <<<System Configuration>>> FIG. 1 is a block diagram showing an example of a system configuration including a vehicle lamp 1 according to this embodiment.

[0011] The system shown in FIG. 1 includes a vehicle ECU (Electronic Control Unit) 10 provided on the vehicle side, and a vehicle lamp 1 on the lamp side.

[0012] The vehicle ECU 10 is connected to the lamp-side lighting fixture ECU 2 of the vehicle lighting fixture 1 via a control line such as a CAN (Controller Area Network), and performs integrated control of the vehicle lighting fixture 1. The vehicle ECU 10 of this embodiment receives vehicle information from the driver's seat of the vehicle and camera information from an on-board camera, and sends a signal to the lighting fixture ECU 2 to control the vehicle lighting fixture 1 based on this information.

[0013] The vehicle lamp 1 is, for example, a headlamp provided at the front end of a vehicle. The vehicle lamp 1 is provided on both the right and left sides of the vehicle, but since the configuration is the same on both sides, Fig. 1 shows the configuration of only one side (for example, the right side). The vehicle lamp 1 of this embodiment includes a lamp ECU 2, a Lo light source 3, a Hi light source 4, and an ADB unit 5.

[0014] The lamp ECU 2 is a device that controls the lighting of each light source of the vehicle lamp 1. Signals including vehicle information, camera information, etc. are input to the lamp ECU 2 from the vehicle ECU 10. Based on these signals, the lamp ECU 2 appropriately lights up the Lo light source 3, the Hi light source 4, and the ADB light source 30 (described later) of the ADB unit 5. The lamp ECU 2 also transmits a signal SA indicating the lighting conditions (such as the light distribution pattern) of the ADB light source 30 to a control circuit 40 (described later) of the ADB unit 5. This signal SA corresponds to a "second signal."

[0015] In addition, a power supply line of the power supply voltage Vbat from a vehicle battery (battery 6 shown in FIG. 2) and a ground line of the voltage at the ground level are input to the lamp ECU 2. Then, the lamp ECU 2 supplies power to the Lo light source 3, the Hi light source 4, and the ADB unit 5.

[0016] The Lo light source 3 is a light source for low beam. The low beam illuminates the vicinity of the host vehicle with a predetermined illuminance, and the light distribution regulation is defined so as not to give glare to oncoming vehicles or preceding vehicles, and it is mainly used when driving in urban areas.

[0017] The Hi light source 4 is a light source for high beam. The high beam illuminates a wide range and the distance ahead with a relatively high illuminance, and it is mainly used when driving at high speed on a road with few oncoming vehicles or preceding vehicles.

[0018] The ADB unit 5 is a unit that constitutes an adaptive driving beam (ADB) that variably controls the light distribution of the light distribution pattern. Note that ADB detects the presence or absence of preceding vehicles, oncoming vehicles, and pedestrians in front of the vehicle using an in-vehicle camera, and reduces the glare given to the vehicle or pedestrians by dimming the area corresponding to the vehicle or pedestrians.

[0019] <<Configuration of ADB Unit 5>> FIG. 2 is a diagram showing a configuration example of the ADB unit 5. FIG. 3 is a diagram showing the configuration of the detection circuit 50 (and the power supply circuit 20) and the like in the first embodiment.

[0020] As shown in FIGS. 1 to 3, the ADB unit 5 of the present embodiment includes a power supply board K1, an LED board K2, and a controller board K3. The power supply circuit 20 and the detection circuit 50 are arranged on the power supply board K1, the ADB light source 30 is arranged on the LED board K2, and the control circuit 40 is arranged on the controller board K3. Also, each board is connected by a signal line such as a harness.

[0021] <ADB Light Source 30> The ADB light source 30 is a light source powered by the output voltage (predetermined voltage) of the power supply circuit 20, which will be described later, and corresponds to the "light source."

[0022] As shown in FIG. 2, the ADB light source 30 includes a plurality (N pieces) of light emitting elements D1 to DN, a plurality (N pieces) of current sources 31_1 to 31_N, and a light distribution adjustment circuit 32.

[0023] The plurality of light-emitting elements D1 to DN and the plurality of current sources 31_1 to 31_N are connected in series between a power supply line and a ground line, respectively. That is, in the ADB light source 30, a plurality of combinations of series-connected light-emitting elements and current sources are arranged in parallel (parallel connection).

[0024] The light emitting elements D1 to DN are elements that light up when a driving current is supplied, and in this embodiment, LEDs (light emitting diodes) are used. The multiple light emitting elements D1 to DN are connected in parallel and are arranged, for example, in an array so as to be able to form a light distribution pattern.

[0025] Based on the output voltage of the power supply circuit 20, the current sources 31_1 to 31_N supply drive currents to the corresponding light emitting elements.

[0026] The light distribution adjustment circuit 32 controls the current sources 31_1 to 31_N in response to an instruction from the control circuit 40 (a signal SC input from the control circuit 40) and adjusts the drive current flowing through the plurality of light emitting elements D1 to DN. This makes it possible to light the vehicle with a light distribution pattern that suits the vehicle situation. The light distribution adjustment circuit 32 corresponds to the "adjustment unit."

[0027] The method of adjusting the drive current by the light distribution adjustment circuit 32 is not particularly limited, and for example, PWM control or analog control can be applied. In this embodiment, the current sources 31_1 to 31_N are configured as current mirror circuits, and by adjusting the magnitude of the drive current flowing through one light-emitting element, the magnitude of the dynamic current flowing through the other light-emitting elements also changes accordingly.

[0028] <Control circuit 40> The control circuit 40 generates a signal SC that collectively instructs the lighting of the plurality of light-emitting elements D1 to DN, such as turning them on and off and setting their brightness pattern, based on a signal SA from the lamp ECU 2 (and a signal SB from the detection circuit 50, which will be described later), and outputs the signal SC to the ADB light source 30 (light distribution adjustment circuit 32). In this way, the control circuit 40 controls the light distribution adjustment circuit 32, and lights up each of the plurality of light-emitting elements D1 to DN at the desired brightness. The control circuit 40 corresponds to a "control unit."

[0029] As described above, in the ADB light source 30 of this embodiment, multiple light-emitting elements D1 to DN are connected in parallel. In this case, the more light-emitting elements to be turned on, the larger the current required. For example, if the number of light-emitting elements is 1000 and the current required to turn on each element is 10 mA, a total current supply capacity of 10 A (= 10 mA × 1000 elements) is required. This increases the heat generated by the power supply circuit 20 that supplies power, which may result in thermal damage to the electronic components that make up the power supply circuit 20.

[0030] Therefore, in the ADB unit 5 of this embodiment, a detection circuit 50 is provided on the power supply board K1 on which the power supply circuit 20 is arranged. Then, based on the signal SB output from the detection circuit 50 and the signal SA indicating the lighting condition from the lamp ECU 2, temperature derating is performed to reduce power consumption in accordance with an increase in temperature.

[0031] <Power circuit 20> The power supply circuit 20 is a voltage regulator that generates a predetermined voltage (e.g., 5 V) based on a power supply voltage Vbat (e.g., 12 V) supplied from the vehicle battery 6. The power supply circuit 20 of this embodiment is a step-down DC-DC converter (e.g., a switching regulator). However, the power supply circuit 20 is not limited to this and may be, for example, a linear regulator or a configuration including a step-up circuit and a step-down circuit (a configuration that steps up and then steps down the voltage).

[0032] The power supply circuit 20 is a so-called synchronous rectification type circuit, and includes capacitors C1 and C2, transistors M1 and M2, a coil L1, resistors R1, R2 and R3, and a control IC 21, as shown in FIG.

[0033] The capacitor C1 is an input-side capacitor, one end of which is connected to the power supply line and the other end of which is connected to the ground line (grounded).

[0034] The transistors M1 and M2 are NMOSFETs. The drain of the transistor M1 is connected to one end of the capacitor C1, and the source of the transistor M1 is connected to the drain of the transistor M2 and one end of the coil L1. The source of the transistor M2 is grounded. The gates of the transistors M1 and M2 are connected to the control IC 21, and the on / off of the transistors M1 and M2 is controlled by the control IC 21.

[0035] The other end of the coil L1 is connected to one end of the output capacitor C2 via a resistor R1. The other end of the capacitor C2 is grounded. The voltage generated across the capacitor C2 is the output voltage.

[0036] Resistors R2 and R3 are connected in series between the connection point between resistor R1 and one end of capacitor C2 and ground. The voltage at the connection point between resistors R2 and R3 (the voltage obtained by dividing the output voltage by resistors R2 and R3) is input to control IC 21.

[0037] The control IC 21 switches the transistors M1 and M2 based on the voltage generated at the connection point between the resistors R2 and R3 so that the output voltage of the power supply circuit 20 becomes a predetermined voltage.

[0038] When transistor M1 is on and transistor M2 is off, the input voltage (the voltage of capacitor C1) is applied to one end of coil L1. When transistor M1 is off and transistor M2 is on, the voltage of the ground line (ground voltage) is applied to one end of coil L1.

[0039] By repeating the above operation, the output voltage of the power supply circuit 20 becomes lower than the input voltage (power supply voltage Vbat) and is controlled to a predetermined voltage (for example, 5V).

[0040] <Detection circuit 50> The detection circuit 50 is provided on the power supply board K1 on which the power supply circuit 20 is arranged, and includes a temperature detection circuit 51 and an interface circuit (hereinafter referred to as I / F circuit) 52.

[0041] The temperature detection circuit 51 is provided on the power supply board K1 and is a circuit for detecting temperature. In this embodiment, the temperature detection circuit 51 is configured with an oscillation circuit that outputs a signal SD with a frequency according to the temperature. As shown in Fig. 3, the temperature detection circuit 51 includes resistors R4 to R6, capacitors C3 and C4, a thermistor Rth1, and an operational amplifier OP1.

[0042] Resistors R4 and R5 are connected in series, one end (one end of resistor R4) is applied with voltage Vcc, and the other end (the other end of resistor R5) is grounded.

[0043] One end of the capacitor C3 is connected to the connection point of the series-connected resistors R4 and R5, and the other end is grounded.

[0044] The inverting input terminal (negative terminal) of the operational amplifier OP1 is grounded via a capacitor C4 and is also connected to the output of the operational amplifier OP1 via a thermistor Rth1. The thermistor Rth1 is an electronic component whose resistance value changes in response to changes in temperature (see FIG. 4A).

[0045] The non-inverting input terminal (+ terminal) of the operational amplifier OP1 is connected to the connection point between the resistors R4 and R5, and is also connected to the output of the operational amplifier OP1 via a resistor R6.

[0046] This temperature detection circuit 51 is an oscillator circuit using an operational amplifier OP1, in which some of the resistors (resistors connected between the negative terminal and the output) are replaced with a thermistor Rth1. The resistance value of the thermistor Rth1 changes in response to temperature, thereby changing the frequency of the output signal (signal SD). This signal SD corresponds to the "first signal." Note that the temperature detection circuit 51 may also be a Hartley oscillator circuit or a Wien-bridge oscillator circuit, for example, as long as it can output a signal SD with a frequency that corresponds to the resistance value of the thermistor Rth1.

[0047] The I / F circuit 52 is a circuit that converts the signal SD, which is the output of the temperature detection circuit 51, into a logic level signal (signal SB). The logic level signal is a rectangular wave signal that switches between a high level (hereinafter referred to as H level) and a low level (hereinafter referred to as L level).

[0048] The I / F circuit 52 includes a transistor M3, resistors R7 to R9, a coil L2, and a capacitor C5. The coil L2 and the capacitor C5 are connected to a pull-up resistor (not shown) inside the control circuit 40.

[0049] The transistor M3 is an NPN transistor, and its emitter is grounded and its collector is connected to one end of the coil L2 via a resistor R9. The collector of the NPN transistor M3 is supplied with power from, for example, the control circuit 40. The base of the NPN transistor M3 is connected to the connection point of resistors R7 and R8, which are connected in series between the output of the temperature detection circuit 51 (the output of the operational amplifier OP1) and the ground. That is, a voltage obtained by dividing the output (signal SD) of the temperature detection circuit 51 by the resistors R7 and R8 is applied to the base of the NPN transistor M3.

[0050] One end of capacitor C5 is connected to the other end of coil L2, and the other end of capacitor C5 is grounded. Coil L2 and capacitor C5 form a noise removal filter. The voltage across capacitor C5 is the output of detection circuit 50.

[0051] With the above configuration, when the NPN transistor M3 is turned on, an L-level signal is output, and when the NPN transistor M3 is turned off, an H-level signal is output. As a result, the output (signal SB) of the I / F circuit 52 becomes a square wave signal (logic level signal) indicating temperature information based on the signal SD (oscillation signal). As a result, even when the signal SB is transmitted to the control circuit 40 of the controller board K3 via a harness, the square wave nature of the signal SB makes it less susceptible to noise (increasing noise resistance).

[0052] 4A to 4C are diagrams illustrating the relationship between temperature information of temperature detection circuit 51 and temperature derating. The horizontal axis of each diagram represents the temperature of thermistor Rth1. The vertical axis of FIG. 4A represents the resistance value of thermistor Rth1, the vertical axis of FIG. 4B represents temperature information of temperature detection circuit 51 (oscillation frequency of signal SD), and the vertical axis of FIG. 4C represents the magnitude of the output current (drive current flowing through the light-emitting element) in ADB light source 30.

[0053] As shown in Fig. 4A, the resistance value of the thermistor Rth1 decreases as the temperature increases, which causes the oscillation frequency of the signal SD to increase as the thermistor temperature increases, as shown in Fig. 4B.

[0054] Based on the signal SD from the temperature detection circuit 51 and the signal SA from the lamp ECU 2 indicating the light distribution pattern (lighting condition), the control circuit 40 generates a signal SC that reduces power consumption (drive current flowing to the light-emitting element) in response to an increase in frequency (temperature increase), as shown in FIG. 4C , and controls the light distribution adjustment circuit 32 (performs temperature derating). This makes it possible to suppress heat generation and prevent damage to electronic components. The range of temperature information (frequency) for which temperature derating is performed (the range corresponding to temperatures Ta to Tb) is designed in accordance with the specifications of the control circuit 40, which receives the information.

[0055] Furthermore, in this embodiment, when performing temperature derating, the control circuit 40 controls the light distribution adjustment circuit 32 so as to reduce the drive current flowing through each of the light-emitting elements D1 to DN without changing the number of light-emitting elements D1 to DN that are turned on. This makes it possible to reduce power consumption (suppress heat generation) without affecting the light distribution pattern. However, this is not limited to this, and for example, the upper limit of the drive current flowing through each light-emitting element may be reduced, or the light distribution pattern may be changed.

[0056] ===== Second Embodiment ===== Figure 5 is a diagram showing the configuration of a detection circuit 150 in the second embodiment. In Figure 5, parts having the same configuration as those in Figure 3 are given the same reference numerals, and descriptions thereof will be omitted. In the second embodiment, a power supply circuit 20 and a detection circuit 150 are provided on a power supply board K1.

[0057] The detection circuit 150 includes a temperature detection circuit 51 , an I / F circuit 52 , and a signal output circuit 53 .

[0058] The signal output circuit 53 is a circuit that outputs a signal SE that serves as a trigger when performing temperature derating, separate from the temperature detection circuit 51, and is configured to include resistors R10 to R12, a thermistor Rth2, and a comparator COM1. The signal output circuit 53 corresponds to the "output circuit," and the signal SE corresponds to the "third signal."

[0059] Resistors R10 and R11 are connected in series, with one end (the end of resistor R10) being applied with voltage Vcc and the other end (the end of resistor R11) being grounded. Thermistor Rth2 and resistor R12 are also connected in series, with one end (the end of thermistor Rth2) being applied with voltage Vcc and the other end (the end of resistor R12) being grounded.

[0060] The inverting input terminal (negative terminal) of the comparator COM1 is connected to the junction of resistors R10 and R11, and the non-inverting input terminal (positive terminal) is connected to the junction of thermistor Rth2 and resistor R12. The comparator COM1 compares the voltage at the positive terminal with the voltage at the negative terminal and outputs the comparison result. Note that the comparator COM1 in this embodiment is an open-drain type, and outputs an open (high impedance) voltage if the voltage at the positive terminal is greater than the voltage at the negative terminal, and an L-level (ground) voltage if the voltage is smaller. Note that the resistance values ​​of the resistors R10, R11, and R12 are set so that the output of the comparator COM1 switches at the temperature Ta shown in FIGS. 4A to 4C in accordance with changes in the resistance of the thermistor Rth2.

[0061] When the temperature of the power supply substrate K1 is higher than a predetermined temperature Ta, the resistance of the thermistor Rth2 is small, so the voltage at the + terminal of the comparator COM1 is greater than the voltage at the - terminal. This causes the output of the comparator COM1 to open. When the temperature drops below the predetermined temperature Ta, the resistance of the thermistor Rth2 increases, and the voltage at the - terminal of the comparator COM1 is greater than the voltage at the + terminal. This causes the output of the comparator COM1 to go to L level. This output of the comparator COM1 is output to the control circuit 40 as a signal SE. The predetermined temperature Ta corresponds to the "second temperature."

[0062] The control circuit 40 of the second embodiment receives the signal SB as well as the output signal (signal SE) of the signal output circuit 53. When the signal SE goes low, the control circuit 40 does not perform temperature derating. That is, regardless of the signal SB output from the I / F circuit 52 (in other words, the signal SD output from the temperature detection circuit 51), the control circuit 40 lights up the plurality of light-emitting elements D1 to DN based on the signal SA from the lamp ECU 2.

[0063] As a result, even when the oscillation operation becomes unstable near the temperature Ta due to the conditions of the temperature detection circuit 51 (oscillator circuit) (such as the resistance values ​​of the operational amplifier OP1 and each resistor), the output (signal SE) of the signal output circuit 53 can be used as a trigger to stop the temperature derating. In this embodiment, the signal output circuit 53 detects the lower limit (temperature Ta) of the range in which temperature derating is required, but a circuit for detecting the upper limit (temperature Tb) may also be provided. This allows temperature derating to be performed reliably within the temperature range in which temperature derating is required.

[0064] =====Third Embodiment===== Figure 6 is a diagram showing the configuration of a detection circuit 250 in the third embodiment. In Figure 6, parts having the same configuration as those in Figures 3 and 5 are given the same reference numerals, and descriptions thereof will be omitted. In the third embodiment, a power supply circuit 20 and a detection circuit 250 are provided on a power supply board K1.

[0065] The detection circuit 250 includes a temperature detection circuit 51, an I / F circuit 52, and an oscillation stop circuit .

[0066] The oscillation stop circuit 54 includes resistors R13 to R15, a thermistor Rth3, and a comparator COM2. As shown in FIG. 6, the oscillation stop circuit 54 has the same configuration as the signal output circuit 53 of the second embodiment (FIG. 5), and therefore a description thereof will be omitted. The output of the oscillation stop circuit 54 (the output of the comparator COM2) is connected to the connection point between the negative terminal of the operational amplifier OP1 of the temperature detection circuit 51, the thermistor Rth1, and the capacitor C4. The oscillation stop circuit 54 corresponds to a "stop circuit."

[0067] When the temperature of the power supply substrate K1 is higher than, for example, the temperature Ta in FIG. 4, the voltage at the + terminal of the comparator COM2 becomes higher than the voltage at the - terminal. This causes the output of the comparator COM2 to open. Therefore, similar to the first embodiment, the temperature detection circuit 51 performs an oscillation operation (temperature detection) according to the temperature, and temperature derating is performed based on the result.

[0068] On the other hand, when the temperature is equal to or lower than temperature Ta, the resistance of the thermistor Rth3 increases, and the voltage at the negative terminal of comparator COM2 becomes greater than the voltage at the positive terminal. This causes the output of comparator COM2 to go low. When the output of comparator COM2 goes low, the negative terminal of operational amplifier OP1 goes to ground level, and operational amplifier OP1 no longer oscillates (oscillation is forcibly stopped). In this way, oscillation stop circuit 54 stops the operation of temperature detection circuit 51 when the temperature goes below temperature Ta. This prevents temperature derating. Note that temperature Ta at this time corresponds to the "first temperature."

[0069] In this third embodiment as well, the output of the oscillation stop circuit 54 can be used as a trigger to stop the temperature derating.

[0070] =====Fourth Embodiment===== Fig. 7 is a diagram showing the configuration of a detection circuit 350 in the fourth embodiment. In Fig. 7, parts having the same configuration as those in Figs. 3, 5, and 6 are given the same reference numerals, and descriptions thereof will be omitted. In the fourth embodiment, a power supply circuit 20 and a detection circuit 350 are provided on a power supply board K1.

[0071] The detection circuit 350 includes a temperature detection circuit 55 and a buffer circuit 56 .

[0072] The temperature detection circuit 55 includes resistors R16 to R25, comparators COM3 to COM5, and a thermistor Rth4.

[0073] The resistors R16 to R19 are connected in series, one end of which (the end of the resistor R16) is applied with a voltage Vcc, and the other end (the end of the resistor R19) is grounded.

[0074] The thermistor Rth4 and resistor R20 are connected in series and are provided in parallel with the resistors R16 to R19. That is, a voltage Vcc is applied to one end (the end of thermistor Rth4) of the series-connected thermistor Rth4 and resistor R20, and the other end (the end of resistor R20) is grounded.

[0075] Resistors R24 and R25 are connected in series, with one end (the end of resistor R24) to which voltage Vcc is applied and the other end (the end of resistor R25) to which ground is applied.

[0076] The voltage at the junction of thermistor Rth4 and resistor R20 is applied to the inverting input terminal (- terminal) of comparator COM3, and the voltage at the junction of resistors R18 and R19 is applied to the non-inverting input terminal (+ terminal). The output of comparator COM3 is connected to the junction of resistors R24 and R25 via resistor R21.

[0077] The voltage at the junction of thermistor Rth4 and resistor R20 is applied to the negative terminal of comparator COM4, ​​and the voltage at the junction of resistors R17 and R18 is applied to the positive terminal. The output of comparator COM3 is connected to the junction of resistors R24 and R25 via resistor R22.

[0078] The voltage at the junction of thermistor Rth4 and resistor R20 is applied to the negative terminal of comparator COM5, and the voltage at the junction of resistors R16 and R17 is applied to the positive terminal. The output of comparator COM3 is connected to the junction of resistors R24 and R25 via resistor R23.

[0079] Comparators COM3, COM4, ​​and COM5 are each open-drain comparators that output an open (high impedance) voltage when the voltage at the + terminal is greater than the voltage at the - terminal, and an L level (ground level) voltage when the voltage at the + terminal is less than the voltage at the - terminal.

[0080] The buffer circuit 56 is a circuit that prevents the output voltage from fluctuating according to the input impedance, and is composed of an operational amplifier OP2 (voltage follower) whose output is negatively fed back. The output voltage of the temperature detection circuit 55 (the voltage at the connection node between resistors R24 and R25) is applied to the positive terminal of the operational amplifier OP2, and the output of the operational amplifier OP2 is sent to the control circuit 40 as a signal SB.

[0081] Next, the operation of the detection circuit 350 (temperature detection circuit 55) will be described.

[0082] 8A to 8D are diagrams showing the relationship between temperature information from the temperature detection circuit 55 and temperature derating. The horizontal axis in FIGS. 8A to 8D represents the temperature of thermistor Rth4. The vertical axis in FIG. 8A represents the resistance value of thermistor Rth4, and the vertical axis in FIG. 8B represents the magnitude of the input to the negative terminal of each comparator (comparators COM3, COM4, ​​COM5). The vertical axis in FIG. 8C represents the output (signal SB) of detection circuit 350, and the vertical axis in FIG. 8D represents the magnitude of the output current (drive current flowing through each light-emitting element) in ADB light source 30.

[0083] As shown in Figure 8A, the resistance value of thermistor Rth4 decreases as the temperature rises. As a result, as shown in Figure 8B, the input voltage to the - terminal of each comparator (comparators COM3, COM4, ​​COM5) increases as the thermistor temperature rises. Note that this input voltage corresponds to a "first voltage" that corresponds to the temperature, and thermistor Rth4 and resistor R20 correspond to a "voltage generating circuit" that generates the input voltage (first voltage).

[0084] As shown in FIG. 8C, at temperatures below Tc, the comparators COM3, COM4, ​​and COM5 are open. Therefore, a voltage obtained by dividing the voltage Vcc by resistors R24 and R25 is output as signal SB. The control circuit 40 does not perform temperature derating at temperatures below Tc. That is, in this embodiment, temperature Tc corresponds to a "second temperature," and the control circuit 40 lights up the multiple light-emitting elements D1 to DN of the ADB light source 30 based on the signal SA from the lamp ECU 2, regardless of the signal SB, at temperatures below Tc.

[0085] When the temperature exceeds Tc, the voltage at the negative terminal of comparator COM3 becomes higher than the voltage at the positive terminal, and the output of comparator COM3 becomes L level (ground level). This causes resistor R21 to be grounded, and as shown in FIG. 8C, the output voltage (the voltage of signal SB) becomes lower than when the temperature is below Tc. In this case, control circuit 40 controls light distribution adjustment circuit 32 so that the drive current flowing through each light-emitting element becomes smaller (for example, to 80% of when the temperature is below Tc), thereby performing temperature derating.

[0086] Furthermore, when the temperature exceeds Td (>Tc), the voltage at the negative terminal of comparator COM4 becomes higher than the voltage at the positive terminal, and the output of comparator COM4 becomes L level (ground level). This causes resistor R22 to be grounded, and the output voltage (voltage of signal SB) becomes lower, as shown in FIG. 8C. In this case, control circuit 40 controls light distribution adjustment circuit 32 so that the drive current flowing through each light-emitting element becomes smaller (for example, to 60% of that at temperatures below Tc), thereby performing temperature derating.

[0087] Furthermore, when the temperature exceeds temperature Te (>Td), the voltage at the negative terminal of comparator COM5 becomes higher than the voltage at the positive terminal, and the output of comparator COM5 becomes L level (ground level). This causes resistor R23 to be grounded, and as shown in FIG. 8C, the output voltage (voltage of signal SB) becomes even lower. In this case, control circuit 40 controls light distribution adjustment circuit 32 so that the drive current flowing through each light-emitting element becomes even smaller (for example, to 40% of the value when temperature is below Tc), thereby performing temperature derating.

[0088] In the fourth embodiment, the voltage (input voltage to the negative terminal of each comparator) that changes in response to an increase in the thermistor temperature is converted into a stepped voltage as shown in Fig. 8C. This stepped voltage corresponds to the "second voltage," and the components of the temperature detection circuit 55 excluding the thermistor Rth4 and resistor R20 correspond to the "voltage conversion circuit."

[0089] In this way, also in the fourth embodiment, by performing temperature derating in accordance with the detection result of the temperature detection circuit 55, it is possible to suppress heat generation and prevent damage to electronic components.

[0090] In addition, in the fourth embodiment, by forming a step-like waveform (voltage) as shown in Figure 8C, it is possible to make the signal less susceptible to noise (increase noise resistance) when transmitting a signal from the temperature detection circuit 55 to the control circuit 40 via the harness.

[0091] ===Summary=== The above describes the vehicular lamp 1 of this embodiment. The vehicular lamp 1 is a lamp used in a vehicle, and includes a power supply circuit 20 that generates a predetermined voltage by stepping down the power supply voltage Vbat, multiple light-emitting elements D1-DN, and a light distribution adjustment circuit 32 that adjusts the drive current flowing through each of the multiple light-emitting elements D1-DN. The ADB light source 30 is powered by the predetermined voltage. In the first embodiment, the power supply board K1 on which the power supply circuit 20 is mounted also includes a temperature detection circuit 51 that detects temperature, and a control circuit 40 that controls the light distribution adjustment circuit 32 based on a signal SD from the temperature detection circuit 51 and a signal SA that indicates the lighting conditions of the multiple light-emitting elements D1-DN. This reduces power consumption when the temperature rises, thereby suppressing heat generation and preventing damage to electronic components.

[0092] Furthermore, the temperature detection circuit 51 of the first to third embodiments is an oscillation circuit that uses a thermistor Rth1 whose resistance changes with temperature, and outputs a signal SD with a frequency that corresponds to the temperature, thereby making it possible to detect the temperature from the oscillation frequency.

[0093] Furthermore, the first to third embodiments include an I / F circuit 52 that converts the signal SD into a signal SB at a logic level, thereby improving noise resistance when transmitting the signal SB to the control circuit 40.

[0094] In the third embodiment, the power supply substrate K1 has an oscillation stop circuit 54 that stops the operation of the temperature detection circuit 51 when the temperature drops below the temperature Ta. This makes it possible to improve the accuracy of the temperature when performing temperature derating.

[0095] Furthermore, the temperature detection circuit 55 of the fourth embodiment includes a voltage generation circuit (thermistor Rth4 and resistor R20) that generates a voltage according to temperature, and a voltage conversion circuit (the portion of the temperature detection circuit 55 excluding the thermistor Rth4 and resistor R20) that converts that voltage into a stepped voltage and outputs it as signal SB. This makes it possible to improve noise resistance when transmitting signal SB to the control circuit 40.

[0096] Furthermore, when the detected temperature is equal to or lower than the temperature Ta (temperature Tc in the fourth embodiment), the control circuit 40 in the first to third embodiments turns on the plurality of light-emitting elements D1 to DN based on the signal SA regardless of the signal SB. This makes it possible to avoid performing temperature derating in a temperature range where temperature derating is not required.

[0097] Furthermore, the second embodiment includes a signal output circuit 53 that outputs a signal SE indicating that the temperature has become equal to or lower than Ta to the control circuit 40. This makes it possible to improve the accuracy of the temperature at which temperature derating is performed.

[0098] Furthermore, when performing temperature derating, the control circuit 40 controls the adjustment unit to reduce the drive current flowing through each of the plurality of light-emitting elements D1 to DN without changing the number of light-emitting elements D1 to DN to be turned on, thereby reducing power consumption without affecting the light distribution pattern.

[0099] Furthermore, the lamp (vehicle lamp 1) of this embodiment can be suitably used as a vehicle headlamp (especially an ADB). However, the present invention is not limited to this, and it may also be applied to, for example, a street lamp. In this case, the same effects can be obtained.

[0100] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. Furthermore, the present invention may be modified or improved without departing from the spirit thereof, and the present invention naturally includes equivalents thereof. For example, the following embodiments may be used.

[0101] In the above embodiment, the circuits of the ADB unit 5 are configured on three boards (power supply board K1, LED board K2, and controller board K3), but may be configured on a single board.

[0102] Furthermore, the control circuit 40 and the light distribution adjustment circuit 32 may be configured, for example, by part of a microcomputer functioning as a control unit and an adjustment unit. [Explanation of symbols]

[0103] 1 Vehicle lighting fixtures 2 Lighting ECU 3 Lo light source 4 Hi light source 5 ADB Unit 6 Battery 10 Vehicle ECU 20 Power circuit 21 Control IC 30 ADB light source 31_1~31_N Current source 32 Light distribution adjustment circuit 40 Control circuit 50 Detection circuit 51 Temperature detection circuit 52 Interface circuit 53 Signal output circuit 54 Oscillation stop circuit 55 Temperature detection circuit 56 Buffer circuit 150,250,350 detection circuit C1~C5 capacitors COM1~COM5 Comparators D1 to DN light-emitting elements, K1 Power Supply Board K2 LED Board K3 controller board L1, L2 coils M1, M2 transistors M3 NPN transistor OP1, OP2 operational amplifiers R1~R25 Resistance Rth1~Rth4 thermistors SA~SD signal Vbat power supply voltage Vcc voltage

Claims

1. a first substrate provided with a power supply circuit that generates a predetermined voltage based on a power supply voltage and a temperature detection circuit that detects temperature; a light source including a plurality of light-emitting elements and an adjusting unit that adjusts a drive current flowing through each of the plurality of light-emitting elements, the light source being powered by the predetermined voltage; a second substrate provided with a control unit that controls the adjustment unit based on a first signal from the temperature detection circuit and a second signal that indicates lighting conditions of the plurality of light-emitting elements; an interface circuit that converts the first signal into a logic level signal; Equipped with the temperature detection circuit is an oscillation circuit that outputs the first signal having a frequency according to temperature; Light equipment.

2. 2. The lamp according to claim 1, a stop circuit provided on the first substrate that stops operation of the oscillation circuit when the temperature drops below a first temperature; Light equipment.

3. a first substrate provided with a power supply circuit that generates a predetermined voltage based on a power supply voltage and a temperature detection circuit that detects temperature; a light source including a plurality of light-emitting elements and an adjusting unit that adjusts a drive current flowing through each of the plurality of light-emitting elements, the light source being powered by the predetermined voltage; a second substrate provided with a control unit that controls the adjustment unit based on a first signal from the temperature detection circuit and a second signal that indicates lighting conditions of the plurality of light-emitting elements; Equipped with The temperature detection circuit a voltage generating circuit that generates a first voltage according to temperature; a voltage conversion circuit that converts the first voltage into a stepped second voltage and outputs the second voltage as the first signal; Including, Light equipment.

4. The lamp according to any one of claims 1 to 3, When the detected temperature is equal to or lower than a second temperature, the control unit turns on the plurality of light-emitting elements based on the second signal regardless of the first signal. Light equipment.

5. 5. The lamp according to claim 4, an output circuit that outputs a third signal to the control unit, the third signal indicating that the temperature has become equal to or lower than the second temperature; Light equipment.

6. The lamp according to any one of claims 1 to 5, the control unit controls the adjustment unit so as to reduce the drive current flowing through each of the plurality of light-emitting elements without changing the number of the light-emitting elements to be turned on. Light equipment.

7. The lamp according to any one of claims 1 to 6, The lamp is used in a vehicle. Light equipment.

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