JP4678355B2 - Headlamp control circuit - Google Patents

Description

  The present invention relates to a headlamp control circuit that controls lighting driving of a headlamp of a vehicle.

  Conventionally, a vehicle has been provided with a high beam headlamp and a low beam headlamp on the left and right sides of the vehicle body so that the driver can switch between the high beam and the low beam according to the road conditions. Yes.

In addition, vehicle headlamps are required to have high reliability from the viewpoint of traffic safety, and there is a need to prevent the low beam headlamps from being disconnected and causing trouble in driving. Therefore, the current flowing through the low beam headlamp is detected to detect the disconnection of the low beam headlamp. When the low beam headlamp is disconnected, the high beam headlamp is dimmed instead of the low beam headlamp. A technique is known in which, when the low-beam headlamp is disconnected, the trouble is prevented from occurring when the low-beam headlamp is disconnected (see, for example, Patent Document 1).
JP-A-11-170908

  However, the failure in the lighting circuit of the headlamp is not necessarily limited to the disconnection of the headlamp, and the headlamp may not be lit due to a failure of a switching element that supplies a current for lighting the headlamp. As described above, in the method of detecting the disconnection of the low beam headlamp and lighting the high beam headlamp, the low beam headlamp is disconnected even if the lighting switching element of the low beam headlamp fails. Otherwise, the high beam headlamps cannot be turned on. If the low beam headlamps cannot be turned on due to a failure of the lighting switching element, all the headlamps are turned off and the operation is hindered. There was an inconvenience that it might occur.

  The present invention has been made in view of such circumstances, and can reduce the possibility that all headlamps will be turned off even if the lighting switching element of the low-beam headlamp fails. An object is to provide a lamp control circuit.

  A headlamp control circuit according to the present invention includes first and second connection terminals that output low beam lighting voltages for lighting first and second light emitting units used as low beam headlamps, respectively, and a high beam Third and fourth connection terminals that output voltages for lighting the third and fourth light emitting units used as headlamps, a low beam lighting instruction for lighting the low beam headlamp, and the high beam An instruction receiving unit for receiving a high beam lighting instruction to turn on the headlamp, and when the low beam lighting instruction is received by the instruction receiving unit, the low beam lighting voltage is collectively applied to the first and second connection terminals. A low beam switch unit for output and a power for detecting an output voltage of the low beam switch unit. When the high beam lighting instruction is received by the detection unit and the instruction receiving unit, a voltage for lighting the high beam headlamp at the first illuminance is output to the third and fourth connection terminals, When the low beam lighting instruction is received by the instruction receiving unit and the low beam lighting voltage is not detected by the voltage detection unit, the high beam headlamp is turned on at a second illuminance that is darker than the first illuminance. And a high beam lighting control unit that outputs the voltage to the third and fourth connection terminals.

  According to this configuration, when the low beam lighting instruction is received by the instruction receiving unit, the low beam lighting voltage is output from the low beam switch unit to the first and second connection terminals and connected to the first and second connection terminals. The first and second light emitting units for the low beam are turned on. Further, when a high beam lighting instruction is received by the instruction receiving unit, the high beam lighting control unit outputs a voltage for lighting the high beam headlamp with the first illuminance to the third and fourth connection terminals, The high-beam third and fourth light emitting units connected to the third and fourth connection terminals are lit with the first illuminance. When the low beam lighting instruction is received by the instruction receiving unit and the low beam lighting voltage is not detected by the voltage detecting unit, the low beam switch unit is considered to be broken. A voltage for lighting the headlamp with the second illuminance darker than the first illuminance is output to the third and fourth connection terminals, and the high-beam headlamp is lit with the second illuminance. As a result, even if the low beam switch unit, which is the switching element for lighting the low beam headlamp, breaks down, the high beam headlamp can be lit with the second illuminance that is darker than the first illuminance. The possibility that the headlamps are turned off can be reduced, and the driver of the oncoming vehicle is not dazzled, so safety is not impaired.

  The high beam lighting control unit preferably generates a voltage for lighting with the second illuminance by adjusting a duty ratio of a voltage output to the third and fourth connection terminals. According to this configuration, since the high beam headlamp can be dimmed by reducing the duty ratio of the voltage supplied to the high beam headlamp, the high beam headlamp is lit at the second illuminance. Is easy.

  The low beam switch section is preferably a semiconductor switch. Semiconductor switches are less reliable than mechanical relays and are more likely to fail. However, if the headlamp control circuit configured in this way is used to control lighting of low-beam headlamps, the low-beam switch unit will fail in a low-beam state. However, since it is possible to reduce that all the headlamps are turned off, it is easy to reduce the size of the low beam switch section as a semiconductor switch.

  The low beam switch unit further includes a self-protection unit that chops the output voltage when an abnormality is detected, and the low beam switch unit passes through the voltage detection unit to the high beam lighting control unit. It is preferable that a low-pass filter is interposed in the signal path to reach.

  According to this configuration, when an abnormality is detected by the self-protection unit, the output voltage of the low beam switch unit is chopped and the output current is limited. Since the low-pass filter is interposed in the signal path from the voltage detection unit to the high beam lighting control unit, the voltage chopped by the low beam switch unit is cut off by the low-pass filter, and the chopped voltage is changed to the chopped voltage. Accordingly, the possibility that the high beam headlamp blinks by the high beam lighting control unit is reduced.

  The instruction receiving unit further receives a dimming lighting instruction for dimming the headlight during daytime to call attention to the surroundings, and the high beam lighting control unit receives the instruction receiving unit by the instruction receiving unit. When the dimming lighting instruction is accepted, it is preferable that a voltage for lighting the high beam headlamp with a third illuminance darker than the second illuminance is output to the third and fourth connection terminals. .

  According to this configuration, when the dimming lighting instruction is received by the instruction receiving unit, the high beam headlight is turned on by the high beam lighting control unit with the third illuminance darker than the second illuminance intended for illumination. By doing so, it is possible to call attention to the surroundings.

  In the headlamp control circuit having such a configuration, when a low beam lighting instruction is received by the instruction receiving unit, a low beam lighting voltage is output from the low beam switch unit to the first and second connection terminals, and the first and second connection terminals are connected. The first and second light emitting units for low beam connected to the terminal are turned on. Further, when a high beam lighting instruction is received by the instruction receiving unit, the high beam lighting control unit outputs a voltage for lighting the high beam headlamp with the first illuminance to the third and fourth connection terminals, The high-beam third and fourth light emitting units connected to the third and fourth connection terminals are lit with the first illuminance. When the low beam lighting instruction is received by the instruction receiving unit and the low beam lighting voltage is not detected by the voltage detecting unit, the low beam switch unit is considered to be broken. A voltage for lighting the headlamp with the second illuminance darker than the first illuminance is output to the third and fourth connection terminals, and the high-beam headlamp is lit with the second illuminance. As a result, even if the low beam switch unit, which is the switching element for lighting the low beam headlamp, breaks down, the high beam headlamp can be lit with the second illuminance that is darker than the first illuminance. The possibility that the headlamps are turned off can be reduced, and the driver of the oncoming vehicle is not dazzled, so safety is not impaired.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a circuit diagram showing an example of the configuration of a headlamp control system using a headlamp control circuit according to the first embodiment of the present invention. The headlamp control system shown in FIG. 1 includes a headlamp control circuit 1, a left low beam headlamp 91 (first light emitting unit), a right low beam headlamp 92 (second light emitting unit), and a left high beam headlamp. 93 (third light emitting unit), a right high beam headlamp 94 (fourth light emitting unit), an ECU (Electric Control Unit) 5, operation switches 6 and 7, and a battery 8 are provided.

  The ECU 5 includes a microcomputer 51, transistors 52 and 53, and resistors 54 and 55. The signal input terminals P1 and P2 of the microcomputer 51 are connected to the operation switches 6 and 7, respectively. The signal output terminal P3 of the microcomputer 51 is connected to the base of the transistor 52 through the resistor 54, and the emitter of the transistor 52 is connected to the ground. The signal output terminal P4 of the microcomputer 51 is connected to the base of the transistor 53 via the resistor 55, and the emitter of the transistor 53 is connected to the ground. Then, the microcomputer 51 turns on and off the transistors 52 and 53 according to the on and off of the operation switches 6 and 7, whereby the collector voltages of the transistors 52 and 53 are sent to the headlamp control circuit 1 as signals S 1 and S 2. Output.

  The headlamp control circuit 1 includes lamp connection terminals 101, 102, 103, and 104 (first, second, third, and fourth connection terminals), lighting instruction reception terminals 105 and 106 (instruction reception unit), and a power supply terminal. 107, fuses 111, 112, 113, and 114, a switch unit SW1 (low beam switch unit), a high beam lighting control unit 120, a voltage detection unit 131, and a CR filter 132.

  The lamp connection terminal 101 is connected to the ground via the left low beam headlamp 91, the lamp connection terminal 102 is connected to the ground via the right low beam headlamp 92, and the lamp connection terminal 103 is connected to the left high beam. The lamp connection terminal 104 is connected to the ground via the right high beam head lamp 94. The power supply terminal 107 is connected to the battery 8.

  The lighting instruction receiving terminals 105 and 106 receive the signals S1 and S2 output from the ECU 5 as lighting instruction signals. Specifically, the lighting instruction receiving terminal 105 is connected to the collector of the transistor 52 and receives the signal S1 output from the ECU 5. The lighting instruction receiving terminal 106 is connected to the collector of the transistor 53, and receives the signal S2 output from the ECU 5.

  The high beam lighting control unit 120 includes a switch unit SW2, a DRL control circuit 121, a DRL PWM generation circuit 122, an HLH control circuit 123, a resistor R1, and a capacitor C2.

  The switch units SW1 and SW2 are semiconductor switches having a self-protection function for limiting the output current when, for example, an abnormality such as overcurrent or overheating due to an output short circuit is detected. For example, a PROFET series semiconductor relay switch manufactured by Infineon is used. be able to. The switch unit SW1 includes a field effect transistor (FET) 201 and a self-protection unit 115. The switch unit SW2 includes an FET 203 and a self-protection unit 117. The self-protecting units 115 and 117 are circuit units that limit the output current by chopping the output voltage at a predetermined frequency when an abnormality is detected.

  The power supply voltage + B is supplied from the battery 8 through the power supply terminal 107 to the drains of the FET 201 and the FET 203. The source of the FET 201 is connected to the lamp connection terminals 101 and 102 via the fuses 111 and 112. The source of the FET 203 is connected to the lamp connection terminal 103 via the fuse 113 and is connected to the lamp connection terminal 104 via the fuse 114.

  Further, the self-protection unit 115 turns on the FET 201 when the signal S1 received by the lighting instruction receiving terminal 105 is at a low level, turns off the FET 201 when the signal S1 is at a high level, or turns on the FET 201 at a predetermined frequency to perform a protection operation. Or chopping the output voltage. In this case, the signal S1 is at a low level, indicating a low beam lighting instruction. The self-protecting unit 117 turns on / off the FET 203 in accordance with a control signal from the HLH control circuit 123, and turns on / off the FET 203 at a predetermined frequency to perform a protection operation, thereby chopping the output voltage.

  The voltage detection unit 131 detects the output voltage of the switch unit SW1, and outputs the detection signal to the DRL control circuit 121 via the CR filter 132 (low-pass filter). For example, a buffer is used. For example, the voltage detection unit 131 uses a threshold voltage that is set in advance so that the output voltage of the switch unit SW1 detects a low beam lighting voltage for lighting the left low beam headlamp 91 and the right low beam headlamp 92. If it is Vth or higher, for example, the detection signal S3 is output at a high level as a detection signal indicating that the low beam lighting voltage has been detected. If the output voltage of the switch unit SW1 does not satisfy the threshold voltage Vth, the low beam lighting voltage is detected. For example, the detection signal S3 is output at a low level as a detection signal indicating that the operation is not performed.

  The CR filter 132 may be provided in a signal path from the switch unit SW1 to the high beam lighting control unit 120 via the voltage detection unit 131. For example, the CR filter 132 is provided between the switch unit SW1 and the voltage detection unit 131. It may be done.

  The lighting instruction reception terminal 106 is connected to the control input terminal of the switch unit SW2 via the DRL control circuit 121, the DRL PWM generation circuit 122, the HLH control circuit 123, and the resistor R1. The lighting instruction receiving terminal 105 is connected to the ground via the capacitor C1, and the lighting instruction receiving terminal 106 is connected to the ground via the capacitor C2. Capacitors C1 and C2 are noise filters.

  The DRL control circuit 121 outputs a control signal instructing high beam lighting to the HLH control circuit 123 when the signal S2 received by the lighting instruction receiving terminal 106 is at a low level. In this case, the signal S2 is at a low level, indicating a high beam lighting instruction.

  Further, the DRL control circuit 121, when the detection signal S3 indicating that the low beam lighting voltage is not detected, that is, the low level detection signal S3, is output from the voltage detection unit 131 via the CR filter 132, the DRL PWM generation circuit. 122 and the HLH control circuit 123 are supplied with a control signal instructing a dimming mode in which the left high beam head lamp 93 and the right high beam head lamp 94 are turned on by reducing the amount of light.

  When the DRL PWM generation circuit 122 receives a control signal instructing the dimming mode from the DRL control circuit 121, for example, the DRL PWM generation circuit 122 generates a PWM signal having a preset duty ratio, for example, an on-duty ratio of 25%, and the HLH control circuit 123. Output to.

  The HLH control circuit 123 is a control for instructing the DRL (Day-time Running Light) mode (the signal S2 is at low level) from the DRL control circuit 121 when the signal S1 received at the lighting instruction receiving terminal 105 is at low level. When the signal is received, a control signal is output to the switch unit SW2 via the resistor R1, and the left high beam head lamp 93 and the right high beam head lamp 94 are turned on.

  In addition, the HLH control circuit 123 has received a control signal for instructing the dimming mode (the signal S2 is at a low level) from the DRL control circuit 121 when the signal S1 received at the lighting instruction receiving terminal 105 is at a high level. In this case, the PWM signal output from the DRL PWM generation circuit 122 is output to the switch unit SW2 via the resistor R1 so that the left high beam head lamp 93 and the right high beam head lamp 94 are dimmed.

  The DRL control circuit 121, the DRL PWM generation circuit 122, and the HLH control circuit 123 may be configured using, for example, a logic circuit or an oscillation circuit, or may be configured using a microcomputer.

  Next, the operation of the headlamp control circuit 1 configured as described above will be described. FIG. 2 is a list showing the operation of the headlamp control circuit 1. In FIG. 2, “H” is described when the signals S1, S2, and S3 are at a high level, and “L” when the signals are at a low level. First. Signal S1: “H” and signal S2: “H” mean that the headlamp is completely turned off. In this case, since the signal S1 is at a high level, the switch unit SW1 is turned off, and the left low beam headlamp 91 and the right low beam headlamp 92 are turned off. Further, since the signal S2 is at a high level, the switch unit SW2 is turned off by the DRL control circuit 121 and the HLH control circuit 123, and the left high beam head lamp 93 and the right high beam head lamp 94 are turned off.

  Signal S1: “L” and signal S2: “H” indicate a low beam lighting instruction. In this case, since the signal S1 is at a low level, the switch unit SW1 is turned on. If the switch unit SW1 is not broken, the power source voltage + B is output from the switch unit SW1 to the left low beam headlamp 91 and the right low beam headlamp 92 via the fuses 111 and 112, and the left low beam headlamp is output. 91 and the right low beam headlamp 92 are lit, and the output voltage of the switch unit SW1 is equal to or higher than the threshold voltage Vth, and the detection signal S3 is a detection signal indicating that the low beam lighting voltage is detected from the voltage detection unit 131. It is output to the DRL control circuit 121 at a high level. Then, since both the signal S2 and the detection signal S3 are at the high level, the DRL control circuit 121 outputs a control signal to the HLH control circuit 123 to turn off the left high beam head lamp 93 and the right high beam head lamp 94. , The switch unit SW2 is turned off by the HLH control circuit 123, and the left high beam head lamp 93 and the right high beam head lamp 94 are turned off.

  On the other hand, if the switch unit SW1 is out of order and the power supply voltage + B is not output from the switch unit SW1 even when the signal S1 is at a low level, the output voltage of the switch unit SW1 is less than the threshold voltage Vth. The detection signal S3 is output to the DRL control circuit 121 at a low level as a detection signal indicating that the low beam lighting voltage is not detected from the unit 131. Then, since both the signal S1 and the detection signal S3 are at a low level, the control signal instructing the dimming mode is output from the DRL control circuit 121 to the DRL PWM generation circuit 122 and the HLH control circuit 123. Then, the DRL PWM generation circuit 122 outputs, for example, a PWM signal with a duty ratio of 25% to the HLH control circuit 123. This PWM signal is output from the HLH control circuit 123 to the switch unit SW2, and the switch unit SW2 is turned on duty. As a result of the switch unit SW2 being turned on / off at a ratio of 25%, the left high beam head lamp 93 and the right high beam head lamp 94 are lit in a state in which the amount of light is reduced.

  Thereby, even if the switch part SW1 that is the switching element for lighting the low beam headlamp is broken, the possibility that all the headlamps are extinguished can be reduced.

  Signal S1: “L” and signal S2: “L” indicate a high beam lighting instruction. In this case, when the signal S1 becomes low level, the switch unit SW1 is turned on. If the switch unit SW1 is not broken, the power source voltage + B is output from the switch unit SW1 to the left low beam head lamp 91 and the right low beam head lamp 92 via the fuses 111 and 112, and the left low beam head lamp is output. 91 and the right low beam headlamp 92 are lit.

  Further, since the signal S2 is at a low level, a control signal for instructing high beam lighting is output from the DRL control circuit 121 to the HLH control circuit 123, the switch unit SW2 is turned on by the HLH control circuit 123, and the left high beam head lamp 93 is turned on. The right high beam headlamp 94 is turned on. In this way, when the high beam lighting instruction is signal S1: “L” and signal S2: “L”, the switch unit SW1 and the switch unit SW2 are turned on, so that the switch unit SW1 and the switch unit SW2 Even if one of them fails, even if the switching element for lighting the low beam headlamp fails, the possibility that all the headlamps are extinguished can be reduced.

  When the high beam lighting instruction is received by the lighting instruction receiving terminals 105 and 106, it is not always necessary to turn on both the switch unit SW1 and the switch unit SW2. For example, the signal S1: “H” and the signal S2: “L” ”May indicate a high beam lighting instruction, and only the switch unit SW2 may be turned on.

  In addition, when the load of the switch unit SW1, for example, the left low beam headlamp 91 or the right low beam headlamp 92 is short-circuited in the low beam lighting state, an overcurrent is detected by the self protection unit 115, and the FET 201 is turned on by the self protection operation. The output voltage is chopped by turning on and off.

  FIG. 3 is a signal waveform diagram showing an example of the output voltage waveform of the FET 201 chopped by the self-protection operation of the switch unit SW1. The horizontal axis indicates time, and the vertical axis indicates voltage. In FIG. 3A, one scale on the horizontal axis is set to 100 msec. FIG. 3B is an enlarged view of the signal waveform of the portion indicated by reference numeral A in FIG. 3A, and one scale on the horizontal axis is 5 msec. As shown in FIG. 3B, the output voltage chopped by the self-protection operation of the switch unit SW1 is a very short pulse with a pulse width of 1 msec or less, for example, at a cycle of 20 msec.

  The output voltage waveform as shown in FIG. 3B is smoothed by the CR filter 132 to become a low level signal. Therefore, when the signal S1: “L” and the signal S2: “H” are received and the low beam lighting instruction is received by the lighting instruction receiving terminals 105 and 106, the left low beam headlamp 91 and the right low beam headlamp 92 are When a short circuit failure occurs and the self-protection function of the switch unit SW1 is activated, the output signal of the switch unit SW1 is less than the threshold voltage Vth, so that the detection signal is detected as a detection signal indicating that the low beam lighting voltage is not detected from the voltage detection unit 131. S3 is output at low level to the DRL control circuit 121. Then, since both the signal S1 and the detection signal S3 are at a low level, the control signal instructing the dimming mode is output from the DRL control circuit 121 to the DRL PWM generation circuit 122 and the HLH control circuit 123. Then, the DRL PWM generation circuit 122 outputs, for example, a PWM signal with a duty ratio of 25% to the HLH control circuit 123, and the PWM signal is output from the HLH control circuit 123 to the switch unit SW2, so that the switch unit SW2 has a duty ratio. As a result of the switch unit SW2 being turned on / off at 25%, the left high beam head lamp 93 and the right high beam head lamp 94 are lit in a state in which the amount of light is reduced.

  Thereby, even if the left low beam head lamp 91 and the right low beam head lamp 92 are short-circuited and the self-protection function of the switch unit SW1 is activated, the possibility that all the head lamps are turned off is reduced. be able to.

  As shown in FIG. 4, a mechanical relay may be used as the switch unit SW1a. However, by using a semiconductor relay switch as shown in FIG. 1, the headlamp control circuit 1 can be easily downsized. In this case, since the reliability of the semiconductor relay switch is generally lower than that of the mechanical relay, if the lighting drive of the left and right left low beam headlamps 91 and the right low beam headlamp 92 is performed by one switch unit SW1, the switch unit SW1. However, according to the headlamp control circuit 1 shown in FIG. 1, even if the switch unit SW1 breaks down in the low beam lighting state, there is an increased possibility that the low beam headlamps cannot be turned on. Since the left high beam head lamp 93 and the right high beam head lamp 94 are turned on instead of the left low beam head lamp 91 and the right low beam head lamp 92, all the head lamps are not turned off, and fail safe. Is preserved.

  Further, when the left high beam headlamp 93 and the right high beam headlamp 94 are turned on instead of the left low beam headlamp 91 and the right low beam headlamp 92 due to a failure of the switch unit SW1, the high beam lighting control unit 120 is turned on. As a result, the left high beam head lamp 93 and the right high beam head lamp 94 are dimmed and turned on. Therefore, the left high beam head lamp 93 and the right high beam head lamp 94 are too bright. Dazzling is reduced and safety is improved.

  Further, if a switching element for lighting control of the left low beam headlamp 91 and a switching element for lighting control of the right low beam headlamp 92 are individually provided, even if one of the switching elements fails, the other Since the headlight continues to be lit, two low beam switching elements are required instead of maintaining fail-safe, which increases costs. On the other hand, according to the headlamp control circuits 1 and 1a shown in FIGS. 1 and 4, the left low beam headlamp 91 and the right low beam headlamp 92 are collectively controlled to be turned on by one switch unit SW1. Thus, while reducing costs, the possibility that all the headlamps are turned off due to the failure of the switch unit SW1 is reduced, and fail-safe is maintained.

  It is to be noted that the headlamp control circuit 1 is connected to a so-called four-lamp type headlight to which a left low beam headlamp 91, a right low beam headlamp 92, a left high beam headlamp 93, and a right high beam headlamp 94 are connected. Although an example of performing the control is shown, for example, as shown in FIG. 4, instead of the left low beam headlamp 91 and the left high beam headlamp 93, a low beam filament 21 (first light emitting unit) and a high beam filament 22 are used. A left headlamp 2 having a (third light emitting portion) is used, and instead of the right low beam headlamp 92 and the right high beam headlamp 94, a low beam filament 31 (second light emitting portion) and a high beam filament 32 ( You may use the right headlamp 3 provided with 4th light emission part.

(Second Embodiment)
Next, a headlamp control circuit according to the second embodiment of the present invention will be described. FIG. 5 is a block diagram showing an example of the configuration of the headlamp control circuit 1b according to the second embodiment of the present invention. The headlamp control circuit 1 b shown in FIG. 5 is different from the headlamp control circuit 1 shown in FIG. 1 in that a DRL / abnormality PWM generation circuit 124 is provided instead of the DRL PWM generation circuit 122.

  When the DRL / abnormality PWM generation circuit 124 receives a DRL lighting instruction (dimming lighting instruction), the DRL / abnormality PWM generation circuit 124 outputs a PWM signal having a duty ratio of about 15% to 25%, for example, a duty ratio of 25%, to the HLH control circuit 123 The HLH control circuit 123 turns on the left high beam head lamp 93 and the right high beam head lamp 94 with an illuminance of 25% (third illuminance) when the high beam is turned on.

  Further, the DRL / abnormality PWM generation circuit 124 outputs a PWM signal having a duty ratio of about 50% to 70%, for example, a duty ratio of 70%, to the HLH control circuit 123 when a failure of the switch unit SW1 occurs. Then, the HLH control circuit 123 turns on the left high beam head lamp 93 and the right high beam head lamp 94 at 70% illuminance (second illuminance) when the high beam is turned on, dimming to an extent that is not dazzling.

  Since the other configuration is the same as that of the headlamp control circuit 1 shown in FIG. 1, its description is omitted, and the characteristic operation of the headlamp control circuit 1b will be described below.

  FIG. 6 is a list for explaining an example of the operation of the headlamp control circuit 1b. First, when the signal S1 is at a high level and the signal S2 is at a low level, a DRL lighting instruction (a dimming lighting instruction) is received by the lighting instruction receiving terminals 105 and 106. The DRL control circuit 121 outputs a control signal for instructing the dimming mode to the HLH control circuit 123 and the DRL / abnormality PWM generation circuit 124.

  The DRL / abnormality PWM generation circuit 124 receives the control signal instructing the dimming mode from the DRL control circuit 121, and the signal level of the signal S1 received by the lighting instruction receiving terminal 105 is high. In this case, a DRL lighting instruction (a dimming lighting instruction) is received, and a PWM signal having a duty ratio of 25%, for example, is output to the HLH control circuit 123. The HLH control circuit 123 causes the left high beam head lamp 93 and the right high beam head lamp to be output. 94 is lit at an illuminance of 25% when the high beam is lit.

  On the other hand, when the signal S1 is at a low level and the signal S2 is at a high level, a low beam lighting instruction is received by the lighting instruction receiving terminals 105 and 106. When the switch unit SW1 is out of order, the output voltage of the switch unit SW1 does not increase even though the signal S1 is at the low level, and the low-level detection signal S3 is output by the voltage detection unit 131 and the filter 132. Is output to the DRL control circuit 121. Then, a control signal instructing the dimming mode is output from the DRL control circuit 121 to the HLH control circuit 123 and the DRL / abnormality PWM generation circuit 124.

  The DRL / abnormality PWM generation circuit 124 receives the control signal instructing the dimming mode from the DRL control circuit 121, and the signal level of the signal S1 received by the lighting instruction receiving terminal 105 is low. In this case, since it is considered that the switch unit SW1 is out of order, for example, a PWM signal having a duty ratio of 70% is output to the HLH control circuit 123, and the HLH control circuit 123 outputs the left high beam head lamp 93 and the right high beam head lamp. 94 is turned on with an illuminance of 70% when the high beam is turned on.

  As a result, when the switch unit SW1 breaks down, the high beam headlight can be dimmed to the extent that it is not dazzled, and the headlight is dimmed in the daytime to alert the surroundings. When the dimming lighting instruction is received, the high beam headlight can be turned on by dimming the brightness to a level that calls attention to the surroundings.

It is a circuit diagram showing an example of composition of a headlamp control system using a headlamp control circuit concerning a 1st embodiment of the present invention. 3 is a list showing an example of the operation of the headlamp control circuit shown in FIG. 1. It is a signal waveform diagram which shows an example of the output voltage waveform chopped by the self-protection operation | movement of the switch part shown in FIG. FIG. 6 is a circuit diagram showing a modification of the headlamp control circuit shown in FIG. 1. It is a circuit diagram which shows an example of a structure of the headlamp control system using the headlamp control circuit which concerns on the 2nd Embodiment of this invention. 6 is a list showing an example of the operation of the headlamp control circuit shown in FIG. 5.

Explanation of symbols

1, 1a, 1b Head lamp control circuit 2 Left head lamp 3 Right head lamp 6, 7 Operation switch 21 Low beam filament 22 High beam filament 31 Low beam filament 32 High beam filament 91 Left low beam head lamp 92 Right low beam head lamp 93 Head lamp for left high beam 94 Head lamp for right high beam 101, 102, 103, 104 Lamp connection terminal 105, 106 Lighting instruction receiving terminal 115, 117 Self-protection unit 120, 120a High beam lighting control unit 121 DRL control circuit 122 DRL PWM Generation circuit 123 HLH control circuit 124 DRL / abnormal PWM generation circuit 131 Voltage detection unit 132 CR filter SW1, SW1a, SW2 switch unit

Claims (4)

First and second connection terminals for outputting low beam lighting voltages for lighting the first and second light emitting units used as low beam headlamps, respectively;
Third and fourth connection terminals for outputting voltages for lighting the third and fourth light emitting units used as high beam headlamps, respectively;
An instruction receiving unit for receiving a low beam lighting instruction for lighting the low beam headlamp and a high beam lighting instruction for lighting the high beam headlamp;
A low beam switch unit that collectively outputs the low beam lighting voltage to the first and second connection terminals when the instruction reception unit receives the low beam lighting instruction;
A voltage detection unit for detecting an output voltage of the low beam switch unit;
When the high beam lighting instruction is received by the instruction receiving unit, a voltage for lighting the high beam headlamp with a first illuminance is output to the third and fourth connection terminals, and the instruction receiving unit When the low beam lighting instruction is accepted by the voltage detector and the low beam lighting voltage is not detected by the voltage detector, a voltage for lighting the high beam headlamp with a second illuminance darker than the first illuminance, A high beam lighting control unit for outputting to the third and fourth connection terminals ,
The low beam switch unit further includes a self-protection unit that chops the output voltage when an abnormality is detected,
A headlamp control circuit , wherein a low-pass filter is interposed in a signal path from the low beam switch unit to the high beam lighting control unit via the voltage detection unit .   First and second connection terminals for outputting low beam lighting voltages for lighting the first and second light emitting units used as low beam headlamps, respectively;
  Third and fourth connection terminals for outputting voltages for lighting the third and fourth light emitting units used as high beam headlamps, respectively;
  An instruction receiving unit for receiving a low beam lighting instruction for lighting the low beam headlamp and a high beam lighting instruction for lighting the high beam headlamp;
  A low beam switch unit that collectively outputs the low beam lighting voltage to the first and second connection terminals when the instruction reception unit receives the low beam lighting instruction;
  A voltage detection unit for detecting an output voltage of the low beam switch unit;
  When the high beam lighting instruction is received by the instruction receiving unit, a voltage for lighting the high beam headlamp at a first illuminance is output to the third and fourth connection terminals, and the instruction receiving unit When the low beam lighting instruction is received by the voltage detector and the low beam lighting voltage is not detected by the voltage detector, a voltage for lighting the high beam headlamp with a second illuminance that is darker than the first illuminance, A high beam lighting control unit for outputting to the third and fourth connection terminals,
  The instruction receiving unit further receives a dimming lighting instruction for dimming the headlight in the daytime to call attention to the surroundings,
  The high beam lighting control unit, when the dimming lighting instruction is received by the instruction receiving unit, a voltage for lighting the high beam headlamp with a third illuminance darker than the second illuminance, Output to the third and fourth connection terminals
  A headlamp control circuit. The high beam lighting control unit generates a voltage for lighting at the second illuminance by adjusting a duty ratio of a voltage output to the third and fourth connection terminals. Or the headlamp control circuit of 2. The headlamp control circuit according to any one of claims 1 to 3, wherein the low beam switch section is a semiconductor switch.

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