JP7535017B2 - Lighting fixtures - Google Patents

Description

The present invention relates to a lighting fixture.

For example, a known lighting device (vehicle lighting device) used in a vehicle is an adaptive driving beam (ADB) headlamp that variably controls the light distribution of the light distribution pattern by arranging multiple light-emitting elements in a row and switching on and off each light-emitting element (see, for example, Patent Document 1).

JP 2016-107743 A

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 lit. For this reason, when many light-emitting elements are provided, a large current may be required, which may result in large amounts of heat being generated and, as a result, the electronic components may be thermally destroyed. In addition, when electronic components are provided on multiple boards, the electronic components on each board may generate heat and be thermally destroyed.

The present invention was made in consideration of the above-mentioned problems with the conventional technology, and its purpose is to provide a lighting fixture that can suppress heat generation and prevent damage to electronic components.

The main invention for solving the above-mentioned problems is a lighting fixture that includes a power supply circuit provided on a first substrate that generates a predetermined voltage based on a power supply voltage, a plurality of light-emitting elements provided on a second substrate, and an adjustment unit that adjusts the drive current flowing through each of the plurality of light-emitting elements, the light source being powered by the predetermined voltage, a control unit provided on a third substrate that controls the adjustment unit, a first temperature detection circuit provided on the first substrate that detects temperature, and a second temperature detection circuit provided on the second substrate that detects temperature, and the control unit controls the adjustment unit based on the higher of the detection results of the first and second temperature detection circuits and a signal indicating the lighting conditions of the plurality of light-emitting elements.

The present invention provides a lighting fixture that can suppress heat generation and prevent damage to electronic components.

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; FIG. 2 is a block diagram showing the configuration of an ADB unit 5. FIG. 2 is a diagram showing an example of the configuration of a circuit arranged on a power supply board K1. FIG. 2 is a diagram showing an example of the configuration of a circuit arranged on an LED board K2. 5A to 5C are diagrams for explaining the relationship between temperature information and temperature derating in the first embodiment. FIG. 11 is a diagram illustrating a configuration of an ADB unit 15 according to a second embodiment. 7A to 7D are diagrams for explaining the relationship between temperature information and temperature derating in the second embodiment.

The present specification and accompanying drawings make clear at least the following:

First Embodiment
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.

The vehicle ECU 10 is connected to the lamp ECU 2 of the vehicle lamp 1 on the lamp side via a control line such as a Controller Area Network (CAN), and controls the vehicle lamp 1 in an integrated manner. In this embodiment, the vehicle ECU 10 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 lamp ECU 2 to control the vehicle lamp 1 based on that information.

The vehicle lamp 1 is, for example, a headlamp provided at the front end of the vehicle, and corresponds to a "lamp". 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.

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 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 (light distribution pattern, etc.) of the ADB light source 30 to the control circuit 40 (described later) of the ADB unit 5.

The lamp ECU 2 also receives a power line of the power supply voltage Vbat from the vehicle battery (battery 6 shown in FIG. 2) and a ground line of the ground level voltage. The lamp ECU 2 then supplies power to the Lo light source 3, the Hi light source 4, and the ADB unit 5.

The low light source 3 is a light source for low beam. Low beam illuminates the vicinity of the vehicle with a specified illuminance, and light distribution regulations are established so as not to cause glare to oncoming vehicles or preceding vehicles, and it is mainly used when driving in urban areas.

The Hi light source 4 is a light source for high beams. High beams illuminate a wide area and a long distance ahead with relatively high illuminance, and are primarily used when driving at high speeds on roads with few oncoming or preceding vehicles.

The ADB unit 5 is a component of an adaptive driving beam (ADB) headlamp that variably controls the light distribution of the light distribution pattern. Note that an ADB uses an on-board camera to detect the presence or absence of preceding vehicles, oncoming vehicles, and pedestrians ahead of the vehicle, and reduces the glare given to the vehicle or pedestrians by dimming the areas corresponding to the vehicle or pedestrian.

<<Configuration of ADB unit 5>>
Fig. 2 is a block diagram showing the configuration of the ADB unit 5. Fig. 3 is a diagram showing an example of the configuration of a circuit arranged on the power supply board K1, and Fig. 4 is a diagram showing an example of the configuration of a circuit arranged on the LED board K2.

As shown in Figures 1 to 4, the ADB unit 5 of this embodiment includes a power supply board K1, an LED board K2, and a controller board K3. The power supply board K1 has a power supply circuit 20 and a detection circuit 50 arranged thereon, the LED board K2 has an ADB light source 30 and a detection circuit 60 arranged thereon, and the controller board K3 has a control circuit 40 arranged thereon. The power supply board K1 corresponds to the "first board", the LED board K2 corresponds to the "second board", and the controller board K3 corresponds to the "third board". The boards are connected to each other by signal lines such as harnesses.

<Power supply 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 in which the voltage is stepped up and then stepped down).

The power supply circuit 20 is a so-called synchronous rectification type circuit, and as shown in FIG. 3, is composed of capacitors C1 and C2, transistors M1 and M2, a coil L1, resistors R1, R2, and R3, and a control IC 21.

Capacitor C1 is an input side capacitor, with one end connected to the power line and the other end connected to the ground line (grounded).

Transistors M1 and M2 are each an NMOSFET. The drain of transistor M1 is connected to one end of capacitor C1, and the source of transistor M1 is connected to the drain of transistor M2 and one end of coil L1. The source of transistor M2 is grounded. In addition, the gates of transistors M1 and M2 are connected to control IC 21, and transistors M1 and M2 are controlled to be turned on and off by control IC 21.

The other end of coil L1 is connected to one end of capacitor C2 on the output side via resistor R1. The other end of capacitor C2 is grounded. The voltage generated across both ends of capacitor C2 is the output voltage.

Resistors R2 and R3 are connected in series between the connection point between resistor R1 and one end of capacitor C2 and ground. In addition, 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.

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

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.

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 (e.g., 5 V).

<ADB light source 30>
The ADB light source 30 is a light source that uses the output voltage (predetermined voltage) of the power supply circuit 20 as its power source, and corresponds to a "light source."

As shown in FIG. 4, the ADB light source 30 includes multiple (N) light-emitting elements D1 to DN, multiple (N) current sources 31_1 to 31_N, and a light distribution adjustment circuit 32.

The multiple light-emitting elements D1 to DN and the multiple current sources 31_1 to 31_N are each connected in series between the power supply line and the ground line. In other words, the ADB light source 30 has multiple combinations of light-emitting elements and current sources connected in series arranged in parallel (parallel connection).

The light-emitting elements D1 to DN are elements that light up when a drive 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 that a light distribution pattern can be formed.

Current sources 31_1 to 31_N each supply a drive current to a corresponding light-emitting element based on the output voltage of the power supply circuit 20.

The light distribution adjustment circuit 32 controls the current sources 31_1 to 31_N in response to instructions from the control circuit 40 (signal SC input from the control circuit 40) and adjusts the drive current flowing through the multiple light-emitting elements D1 to DN. This allows the light to be turned on in a light distribution pattern that suits the vehicle's situation. The light distribution adjustment circuit 32 corresponds to the "adjustment unit."

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 a current mirror circuit, 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 changes accordingly.

<Control Circuit 40>
Based on a signal SA from the lamp ECU 2 (and signals SB1, SB2 from detection circuits 50, 60 described later), the control circuit 40 generates a signal SC that collectively instructs the turning on and off of the multiple light-emitting elements D1 to DN, the brightness pattern, etc., and outputs the signal SC to the light distribution adjustment circuit 32 of the ADB light source 30. In this way, the control circuit 40 controls the light distribution adjustment circuit 32 to light up each of the multiple light-emitting elements D1 to DN at the desired brightness. The control circuit 40 corresponds to a "control unit."

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 that are turned on, the larger the current required. For example, if there are 1000 light-emitting elements and the current required to turn on each one is 10 mA, a total current supply capacity of 10 A (= 10 mA x 1000 elements) is required. This causes the power supply circuit 20 that supplies power and the ADB light source 30 to generate large amounts of heat, which may cause thermal damage to electronic components.

In the ADB unit 5 of this embodiment, a detection circuit 50 capable of detecting temperature is provided on the power supply board K1 on which the power supply circuit 20 is arranged, and a detection circuit 60 capable of detecting temperature is provided on the LED board K2 on which the ADB light source 30 is arranged. Then, based on one of the detection results of the detection circuit 50 and the detection circuit 60 (the higher temperature) and a signal SA indicating the lighting conditions from the lamp ECU 2, temperature derating is performed to reduce power consumption in response to an increase in temperature.

<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 has a temperature detection circuit 51 and an interface circuit (hereinafter, referred to as I/F circuit) 52.

The temperature detection circuit 51 is provided on the power supply board K1 and is a circuit that detects temperature. The temperature detection circuit 51 corresponds to the "first temperature detection circuit." In this embodiment, the temperature detection circuit 51 is composed of an oscillator circuit that outputs a signal SD1 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.

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

One end of capacitor C3 is connected to the junction point between resistors R4 and R5, which are connected in series, and the other end is grounded.

The inverting input terminal (- terminal) of the operational amplifier OP1 is grounded via a capacitor C4 and is 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 Figure 5A).

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

This temperature detection circuit 51 is an oscillator circuit using an operational amplifier OP1, in which some of the resistors (resistors connected between the - terminal and the output) have been replaced with a thermistor Rth1. The resistance value of thermistor Rth1 changes in response to temperature, causing the frequency of the output signal (signal SD1) to change. Note that as long as the temperature detection circuit 51 can output a signal SD with a frequency that corresponds to the resistance value of thermistor Rth1, it is also possible to use, for example, a Hartley oscillator circuit or a Wien bridge oscillator circuit.

The I/F circuit 52 is a circuit that converts the output signal (signal SD1) of the temperature detection circuit 51 into a logic level signal (signal SB1). A logic level signal is a rectangular wave signal that switches between a high level (hereinafter H level) and a low level (hereinafter L level). The I/F circuit 52 corresponds to the "first interface circuit."

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

Transistor M3 is an NPN transistor, with its emitter grounded and its collector connected to one end of coil L2 via resistor R9. The collector of NPN transistor M3 is supplied with power from, for example, control circuit 40. The base of NPN transistor M3 is connected to the connection point of resistors R7 and R8, which are connected in series between the output of temperature detection circuit 51 (output of operational amplifier OP1) and ground. In other words, the voltage obtained by dividing the output (signal SD1) of temperature detection circuit 51 by resistors R7 and R8 is applied to the base of NPN transistor M3.

One end of the capacitor C5 is connected to the other end of the coil L2, and the other end of the capacitor C5 is grounded. The coil L2 and the capacitor C5 form a filter for removing noise. The voltage across the capacitor C5 is the output of the detection circuit 50.

With the above configuration, when NPN transistor M3 is turned on, an L-level signal is output, and when NPN transistor M3 is turned off, an H-level signal is output. As a result, the output (signal SB1) of I/F circuit 52 becomes a square wave signal (logical level signal) indicating temperature information based on signal SD1. As a result, even when transmitting to control circuit 40 of controller board K3 via a harness, signal SB1 is a square wave, making it less susceptible to noise (increasing noise resistance).

<Detection Circuit 60>
The detection circuit 60 is provided on the LED board K2 on which the ADB light source 30 is arranged, and includes a temperature detection circuit 61 and an I/F circuit 62.

The temperature detection circuit 61 is provided on the LED board K2 and is a circuit that detects temperature. The temperature detection circuit 61 corresponds to the "second temperature detection circuit." In this embodiment, the temperature detection circuit 61 is composed of an oscillator circuit that outputs a signal SD2 with a frequency according to the temperature. As shown in FIG. 4, the temperature detection circuit 61 includes resistors R10 to R12, capacitors C6 and C7, a thermistor Rth2, and an operational amplifier OP2. The configuration of the temperature detection circuit 61 is similar to that of the temperature detection circuit 51, so a description thereof will be omitted.

The I/F circuit 62 is a circuit that converts the output signal (signal SD2) of the temperature detection circuit 61 into a logic level signal (signal SB2). The I/F circuit 62 corresponds to the "second interface circuit." The I/F circuit 62 includes a transistor M4, resistors R13 to R15, a coil L3, and a capacitor C8. The coil L3 and the capacitor C8 are connected to a pull-up resistor (not shown) inside the control circuit 40. The configuration of the I/F circuit 62 is similar to that of the I/F circuit 52, so a description thereof will be omitted.

<<About temperature derating>>
The control circuit 40 performs temperature derating based on one of the detection results of the detection circuit 50 (in other words, the temperature detection circuit 51) and the detection results of the detection circuit 60 (in other words, the temperature detection circuit 61), and a signal SA indicating the light distribution pattern (lighting conditions) from the lamp ECU 2.

Figures 5A to 5C are diagrams for explaining the relationship between temperature information and temperature derating in the first embodiment. Note that while the temperature information of the temperature detection circuit 51 (thermistor Rth1) is explained here, the same applies to the temperature detection circuit 61 (thermistor Rth2). The horizontal axis of each figure indicates the temperature of thermistor Rth1. The vertical axis of Figure 5A indicates the resistance value of thermistor Rth1, the vertical axis of Figure 5B indicates the temperature information of the temperature detection circuit 51 (oscillation frequency of signal SD1), and the vertical axis of Figure 5C indicates the magnitude of the output current (drive current flowing through the light-emitting element) in the ADB light source 30.

As shown in FIG. 5A, the resistance value of thermistor Rth1 decreases as the temperature increases. As a result, as shown in FIG. 5B, the frequency of oscillation of signal SD1 (signal SB1) increases as the temperature increases. Similarly, in temperature detection circuit 61, the frequency of oscillation of signal SD2 (signal SB2) increases as the temperature increases.

The control circuit 40 selects the signal SB1 received from the detection circuit 50 or the signal SB2 received from the detection circuit 60, whichever has the higher frequency (in other words, the higher temperature). Then, based on the detection result of the higher temperature and the signal SA indicating the lighting conditions, it performs temperature derating as shown in FIG. 5C. In other words, it generates a signal SC that reduces power consumption (drive current flowing through the light-emitting element) in response to an increase in frequency (increase in temperature), and controls the light distribution adjustment circuit 32.

In this embodiment, when performing temperature derating, the control circuit 40 controls the light distribution adjustment circuit 32 so that the drive current flowing through each of the light-emitting elements D1 to DN is reduced 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 value of the drive current flowing through each light-emitting element may be lowered, or the light distribution pattern may be changed. In this way, heat generation in the power supply board K1 and the LED board K2 can be efficiently suppressed, and it is possible to prevent damage to electronic components.

The range of temperature information (frequency) for temperature derating (the range corresponding to temperatures Ta to Tb) is designed according to the specifications of the control circuit 40, which receives the information. If this temperature range is wide and the oscillation operation becomes unstable, a temperature detection circuit (not shown) that acts as a trigger in addition to the oscillation circuit may be provided on each of the power supply board K1 and the LED board K2, and temperature derating may be performed or stopped based on the output of that circuit.

Second Embodiment
In the second embodiment, the configuration of the ADB unit is different from that in the first embodiment.
Fig. 6 is a diagram showing the configuration of an ADB unit 15 according to the second embodiment. In Fig. 6, the same components as those in the first embodiment are given the same reference numerals and the description thereof will be omitted.

In the second embodiment, the power supply circuit 20 and the detection circuit 150 are arranged on the power supply board K1, the ADB light source 30 and the detection circuit 160 are arranged on the LED board K2, and the control circuit 40 and the voltage conversion circuit 70 (and the buffer circuit 71) are arranged on the controller board K3.

The detection circuit 150 is provided on the power supply board K1 and includes a temperature detection circuit 53 that detects temperature and a buffer circuit 54.

The temperature detection circuit 53 includes a resistor R16 and a thermistor Rth3. The resistor R16 and thermistor Rth3 are connected in series, with one end (the end of the thermistor Rth3) being applied with a voltage Vcc and the other end (the end of the resistor R16) being grounded. In the second embodiment, the temperature detection circuit 53 corresponds to the "first temperature detection circuit."

The buffer circuit 54 is a circuit that prevents the output voltage from fluctuating according to the input impedance, and is composed of an operational amplifier OP3 (voltage follower) whose output is negatively fed back. The output voltage of the temperature detection circuit 53 (the voltage at the connection node between resistor R16 and thermistor Rth3) is applied to the positive terminal of the operational amplifier OP3, and the output of the operational amplifier OP3 is sent to the controller board K3 as a signal SE1.

The detection circuit 160 is provided on the LED board K2 and includes a temperature detection circuit 63 that detects the temperature and a buffer circuit 64.

The temperature detection circuit 63 includes a resistor R17 and a thermistor Rth4. The temperature detection circuit 63 has a similar configuration to the temperature detection circuit 53, so a description thereof will be omitted. In the second embodiment, the temperature detection circuit 63 corresponds to the "second temperature detection circuit."

The buffer circuit 64 is a circuit having the same function as the buffer circuit 54, and is composed of an operational amplifier OP4 (voltage follower) whose output is negatively fed back. The output voltage of the temperature detection circuit 63 (the voltage at the connection node between resistor R17 and thermistor Rth4) is applied to the positive terminal of the operational amplifier OP4, and the output of the operational amplifier OP4 is sent to the controller board K3 as a signal SE2.

The voltage conversion circuit 70 is a circuit that converts the detection results of the temperature detection circuit 53 and the temperature detection circuit 63 into a stepped voltage waveform (see FIG. 7C), and is composed of resistors R18 to R26, comparators COM1 to COM3, and a switch SW1.

Resistors R18 to R21 are connected in series, with one end (the end of resistor R18) being applied with voltage Vcc, and the other end (the end of resistor R21) being grounded.

In addition, resistors R25 and R26 are connected in series, with one end (the end of resistor R25) being applied with voltage Vcc and the other end (the end of resistor R26) being grounded.

The switch SW1 is a switch for switching the input to the inverting input terminal (- terminal) of each of the comparators COM1 to COM3 to the detection result (signal SE1) of the detection circuit 150 or the detection result (signal SE2) of the detection circuit 160. In this embodiment, the switching of the switch SW1 is automatically performed every predetermined time (for example, one minute) by a timer or the like. However, this is not limited to this, and for example, the control circuit 40 may select the target of temperature detection (switch the switch SW1).

The voltage at the connection point between resistors R20 and R21 is applied to the non-inverting input terminal (+ terminal) of comparator COM1. The output of comparator COM1 is also connected to the connection point between resistors R25 and R26 via resistor R22.

The voltage at the connection point between resistors R19 and R20 is applied to the positive terminal of comparator COM2. The output of comparator COM2 is also connected to the connection point between resistors R25 and R26 via resistor R23.

The voltage at the connection point between resistors R18 and R19 is applied to the positive terminal of comparator COM3. The output of comparator COM3 is also connected to the connection point between resistors R25 and R26 via resistor R24.

Comparators COM1, COM2, and COM3 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.

Buffer circuit 71 is a circuit having the same function as buffer circuits 54 and 64, and is composed of an operational amplifier OP5 (voltage follower) whose output is negatively fed back. The output voltage of voltage conversion circuit 70 (the voltage at the connection node between resistors R25 and R26) is applied to the positive terminal of operational amplifier OP5. The output of voltage conversion circuit 70 is then input to control circuit 40 via buffer circuit 71 (operational amplifier OP5).

Next, the temperature derating operation of the second embodiment will be described.

Figures 7A to 7D are diagrams showing the relationship between temperature information and temperature derating in the second embodiment. Note that, here, a case where the detection result (signal SE1) of the detection circuit 150 is selected by the switch SW1 will be described, but the same applies to the case where the detection result (signal SE2) of the detection circuit 160 is selected. The horizontal axis of Figures 7A to 7D indicates the temperature of thermistor Rth3. The vertical axis of Figure 7A indicates the resistance value of thermistor Rth3, and the vertical axis of Figure 7B indicates the magnitude of the input to the negative terminal of each comparator (comparators COM1, COM2, COM3). The vertical axis of Figure 7C indicates the output voltage (temperature information) of the voltage conversion circuit 70, and the vertical axis of Figure 7D indicates the magnitude of the output current (drive current flowing through each light-emitting element) in the ADB light source 30.

As shown in FIG. 7A, the resistance value of thermistor Rth3 decreases as the temperature increases. As a result, the voltage at the connection node between thermistor Rth3 and resistor R16 increases as the temperature increases. In other words, as shown in FIG. 7B, the input voltage to the - terminal of each comparator (comparators COM1, COM2, COM3) increases as the temperature increases.

As shown in FIG. 7C, at temperatures below Tc, comparators COM1, COM2, and COM3 are open. Therefore, the voltage conversion circuit 70 outputs a voltage obtained by dividing the voltage Vcc by resistors R25 and R26.

When the temperature exceeds Tc, the voltage at the negative terminal of comparator COM1 becomes higher than the voltage at the positive terminal, and the output of comparator COM1 becomes L level (ground level). This causes resistor R22 to be grounded, and as shown in Figure 7C, the output voltage (temperature information) of voltage conversion circuit 70 becomes lower than when the temperature is below Tc.

When the temperature exceeds Td (>Tc), the voltage at the negative terminal of comparator COM2 becomes higher than the voltage at the positive terminal, and the output of comparator COM2 becomes L level (ground level). This causes resistor R23 to be grounded, and the output voltage of voltage conversion circuit 70 becomes lower, as shown in FIG. 7C.

Furthermore, when the temperature exceeds Te (> Td), the voltage at the - terminal of comparator COM3 becomes higher than the voltage at the + terminal, and the output of comparator COM3 becomes L level (ground level). This causes resistor R24 to be grounded, and as shown in Figure 7C, the output voltage of voltage conversion circuit 70 becomes even lower.

In this way, the voltage conversion circuit 70 converts the voltage proportional to temperature (analog voltage) shown in FIG. 7B into a stepped voltage as shown in FIG. 7C.

By switching switch SW1 at a predetermined timing, the control circuit 40 receives temperature information obtained by converting the detection result of the detection circuit 150 (temperature detection circuit 53) by the voltage conversion circuit 70, and temperature information obtained by converting the detection result of the detection circuit 160 (temperature detection circuit 63) by the voltage conversion circuit 70.

Then, the control circuit 40 controls the light distribution adjustment circuit 32 based on the higher temperature among the temperature information (detection results) and the signal SA.

For example, in FIG. 7D, temperature derating is not performed below temperature Tc. In other words, below temperature Tc, the control circuit 40 turns on 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 temperature information (detection result).

When the temperature exceeds Tc, the control circuit 40 controls the light distribution adjustment circuit 32 so that the drive current flowing through each light-emitting element becomes small (for example, to 80% of the current when the temperature is below Tc).

In addition, when the temperature exceeds Td, the control circuit 40 controls the light distribution adjustment circuit 32 so that the drive current flowing through each light-emitting element becomes smaller (for example, to 60% of the current when the temperature is below Tc).

In addition, when the temperature exceeds Te, the control circuit 40 controls the 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 current when the temperature is below Tc).

In this way, when the temperature Tc is exceeded, the control circuit 40 controls the light distribution adjustment circuit 32 to perform temperature derating. This suppresses heat generation in the power supply board K1 and the LED board K2, and prevents thermal damage to electronic components. When performing temperature derating, as in the first embodiment, the light distribution adjustment circuit 32 is controlled so that the drive current flowing through each of the light-emitting elements D1 to DN is reduced 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.

In this embodiment, the voltage conversion circuit 70 is disposed on the controller board K3, but the voltage conversion circuit 70 may be provided on each of the power supply board K1 and the LED board K2, and a stepped voltage waveform (Figure 7C) may be sent to the control circuit 40 of the controller board K3. In this case, noise resistance can be improved. On the other hand, if the voltage conversion circuit 70 is provided on the controller board K3 as in this embodiment, it can be used in common for the detection results of the temperature detection circuit 53 and the detection results of the temperature detection circuit 63, thereby reducing the number of parts and saving space.

====Summary====
The vehicle lamp 1 of this embodiment has been described above. The vehicle lamp 1 is a lamp used in a vehicle, and includes a power supply circuit 20 provided on a power supply board K1 that generates a predetermined voltage based on a power supply voltage Vbat, an ADB light source 30 provided on an LED board K2, and a control circuit 40 provided on a controller board K3. The ADB light source 30 is a light source that uses a predetermined voltage as a power source, and includes a plurality of light-emitting elements D1 to DN and a light distribution adjustment circuit 32 that adjusts the drive current flowing through each of the plurality of light-emitting elements D1 to DN. In addition, the power supply board K1 of the first embodiment is provided with a temperature detection circuit 51 that detects temperature, and the LED board K2 is provided with a temperature detection circuit 61 that detects temperature, and the control circuit 40 controls the light distribution adjustment circuit 32 based on the detection result of the higher temperature among the detection results of the temperature detection circuits 51 and 61 and the signal SA that indicates the lighting condition of the plurality of light-emitting elements D1 to DN. This makes it possible to efficiently suppress heat generation in the power supply board K1 and the LED board K2, and to prevent damage to electronic components.

The temperature detection circuits 51 and 61 are each an oscillation circuit that oscillates at a frequency according to the temperature. This allows the temperatures of the power supply board K1 and the LED board K2 to be detected from the respective frequencies.

The power supply board K1 is provided with an I/F circuit 52 that converts the output signal SD1 of the temperature detection circuit 51 into a logic level signal SB1, and the LED board K2 is provided with an I/F circuit 62 that converts the output signal SD2 of the temperature detection circuit 61 into a logic level signal SB2. This makes it possible to reduce the influence of noise (increase noise resistance).

In the second embodiment, the power supply board K1 is provided with a temperature detection circuit 53 including a resistor R16 and a thermistor Rth3, and the LED board K2 is provided with a temperature detection circuit 63 including a resistor R17 and a thermistor Rth4. This allows the temperatures of the power supply board K1 and the LED board K2 to be detected with a simple configuration.

It also has a voltage conversion circuit 70 that converts the detection results of the temperature detection circuit 53 and the temperature detection circuit 63 into a stepped voltage waveform. This improves noise resistance.

The voltage conversion circuit 70 is also provided on the controller board K3. This allows the detection results of the temperature detection circuit 53 and the temperature detection circuit 63 to be converted by a single voltage conversion circuit 70, thereby reducing the number of components and saving space.

In addition, when performing temperature derating, the control circuit 40 controls the adjustment unit so that the drive current flowing through each of the multiple light-emitting elements D1 to DN is reduced without changing the number of the multiple light-emitting elements D1 to DN that are turned on. This makes it possible to reduce power consumption without affecting the light distribution pattern.

The lamp of this embodiment (vehicle lamp 1) can be suitably used as a vehicle headlamp (particularly an ADB). However, this is not limited thereto, and it may also be applied to, for example, a street lamp. In this case, the same effect can be obtained.

The above embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. Furthermore, the present invention may be modified or improved without departing from the spirit of the present invention, and it goes without saying that the present invention includes equivalents. For example, the following form is also possible.

In the above embodiment, the control circuit 40 and the light distribution adjustment circuit 32 are provided as separate entities, but for example, a part of the microcomputer may be configured to function as the control unit and the adjustment unit.

In the second embodiment, the detection results of the temperature detection circuits 51 and 61 are converted into stepped voltages by the voltage conversion circuit 70, but the voltage may be input to the control circuit 40 without being converted (as an analog voltage). Temperature derating may then be performed based on one of the detection results (the higher temperature) and the signal SA.

1 Vehicle lighting 2 Lighting ECU
3 Lo light source 4 Hi light source 5, 15 ADB unit 6 Battery 10 Vehicle ECU
20 Power supply circuit 21 Control IC
30 ADB light sources 31_1 to 31_N Current source 32 Light distribution adjustment circuit 40 Control circuit 50, 60 Detection circuit 51, 61 Temperature detection circuit 52, 62 Interface circuit 53, 63 Temperature detection circuit 54, 64, 71 Buffer circuit 70 Voltage conversion circuit 150 , 160 detection circuits C1 to C8 capacitors COM1 to COM3 comparators D1 to DN light emitting elements,
K1 Power supply board K2 LED board K3 Controller board L1 to L3 Coils M1 to M4 Transistors OP1 to OP5 Operational amplifiers R1 to R26 Resistors Rth1 to Rth4 Thermistors SA, SB1, SB2, SC, SD1, SD2, SE1, SE2 Signal SW1 Switch Vbat Power supply voltage Vcc Voltage

Claims (8)

a power supply circuit provided on the first substrate for generating a predetermined voltage based on a power supply voltage;
a light source provided on a second substrate, the light source including a plurality of light emitting elements and an adjustment 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 control unit provided on a third substrate and controlling the adjustment unit;
a first temperature detection circuit provided on the first substrate for detecting a temperature;
a second temperature detection circuit provided on the second substrate and configured to detect a temperature;
having
The control unit controls the adjustment unit based on a higher temperature detection result of the first and second temperature detection circuits and a signal indicating a lighting condition of the plurality of light-emitting elements.
Lighting fixture. 2. The lamp according to claim 1,
The first and second temperature detection circuits are each an oscillation circuit that oscillates at a frequency according to temperature.
Lighting fixture. The lamp according to claim 2,
a first interface circuit that converts an output signal of the first temperature detection circuit into a logic level signal is provided on the first substrate;
The second substrate is provided with a second interface circuit that converts an output signal of the second temperature detection circuit into a logic level signal.
Lighting fixture. 2. The lamp according to claim 1,
The first and second temperature detection circuits each include a resistor and a thermistor.
Lighting fixture. The lamp according to claim 4,
a voltage conversion circuit for converting detection results of the first and second temperature detection circuits into a stepped voltage waveform;
Lighting fixture. The lamp according to claim 5,
the voltage conversion circuit is provided on the third substrate;
Lighting fixture. The lamp according to any one of claims 1 to 6,
The control unit controls the adjustment unit so as to reduce the driving current flowing through each of the plurality of light-emitting elements without changing the number of the light-emitting elements to be turned on among the plurality of light-emitting elements.
Lighting fixture. The lamp according to any one of claims 1 to 7,
The lamp is used in a vehicle.
Lighting fixture.

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