JP2011073509A - On-vehicle lamp lighting control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an on-vehicle lamp lighting control circuit which executes the lighting control of a plurality of on-vehicle lamps in adequate brightness without complicating its wiring structure. <P>SOLUTION: When the pulse width of the pulse voltage is variable, and a kind of a plurality of on-vehicle lamps with the common pulse voltage being supplied thereto are different, a relay switch 21 is connected in series to on-vehicle lamp, for example, a light emitting diode L3 of a license plate lamp 11. When the pulse voltage to be supplied from a lamp drive circuit 1 is of the short pulse shape, the switch is set to be in a constantly contact state, and the pulse voltage from the lamp drive circuit 1 is supplied to the light emitting diode L3. Further, when the pulse voltage to be supplied has a duty ratio of 100%, the relay switch 21 is subjected to PWM (Pulse Width Modulation) drive, and the pulse voltage is supplied to the light emitting diode L3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an in-vehicle lamp lighting control circuit that performs lighting control of any of a plurality of in-vehicle lamps supplied with a common pulse voltage.

  The vehicle includes a plurality of on-vehicle lamps such as a headlamp, a direction indicator lamp, a tail lamp, and a stop lamp. As the number of in-vehicle lamps increases, the cost also increases. Therefore, Patent Document 1 discloses an invention that can reduce the number of in-vehicle lamps and reduce the cost. In Patent Document 1, the brightness of a plurality of lamps is changed according to the application by controlling the power supply time to the lamps by PWM (Pulse Width Modulation) control. According to Patent Document 1, for example, the number of lamps can be reduced by using a tail lamp as a stop lamp.

JP 2003-72456 A

  However, it is necessary to mount in-vehicle lamps such as high-mount stop lamps and license plate lamps in recent vehicles, but these in-vehicle lamps cannot be used as tail lamps and stop lamps. For this reason, when a high-mount stop lamp or the like is mounted on a vehicle, it is necessary to further prepare a circuit different from the circuit of Patent Document 1 for controlling lighting of the tail lamp and the stop lamp. In this case, there arises a problem that the wiring space and cost increase. Further, when the above-described circuits for controlling the lighting of each on-vehicle lamp are combined into one, the wiring structure may be complicated.

  The present invention has been made in view of such circumstances, and an object of the present invention is to control lighting of a plurality of in-vehicle lamps with appropriate brightness without complicating the wiring structure. It is to provide a circuit.

    An on-vehicle lamp lighting control circuit according to the present invention includes a switch connected in series with any of a plurality of on-vehicle lamps to which a common pulse voltage is supplied, and switching means for switching the switch according to the pulse width of the pulse voltage. It is characterized by providing.

  When the pulse width of the pulse voltage is variable and the types of multiple in-vehicle lamps supplied with a common pulse voltage are different, when the pulse voltage is a pulse width suitable for the brightness of any in-vehicle lamp, The other on-vehicle lamps are supplied with a pulse voltage having a pulse width not suitable for brightness. Therefore, the present invention switches the switch connected in series to the in-vehicle lamp according to the pulse width of the supplied pulse voltage, that is, the time during which the voltage is supplied, so that the pulse voltage not suitable for brightness is switched. Can be prevented from being supplied to in-vehicle lamps connected in series. As a result, even if the types of the plurality of in-vehicle lamps are different, the power supply lines of the in-vehicle lamps can be shared, so that the complexity of the wiring structure can be suppressed. In addition, by sharing the power line, a new in-vehicle lamp can be easily added, and the design can be easily changed.

  Moreover, when it is not necessary to turn on a vehicle-mounted lamp, it can avoid lighting a vehicle-mounted lamp by supplying the pulse voltage which is not suitable for brightness. Thereby, the vehicle-mounted lamp which connected the switch in series can be lighted at an appropriate timing.

  The on-vehicle lamp lighting control circuit according to the present invention further includes means for smoothing the supplied pulse voltage, and a comparator for comparing the smoothed voltage with a threshold voltage, and the switching means includes the comparator. As a result of comparison, when the smoothed voltage is high, the switch is connected, and when the smoothed voltage is low, the switch is cut off.

  In the present invention, when the smoothed voltage is larger than the threshold voltage, the switch is in the connected state, and when it is smaller, the switch is in the cut-off state. By smoothing the pulse voltage, the rise of the voltage increases smoothly. Therefore, when a voltage with a small pulse width is supplied, the smoothed voltage does not become larger than the threshold voltage. Thereby, since the switch is cut off, it is possible to prevent a voltage having a small pulse width from being supplied to the in-vehicle lamp.

  The on-vehicle lamp lighting control circuit according to the present invention is characterized in that the switch is connected in series to a high-mount stop lamp.

  In the present invention, a high-mount stop lamp can be newly added without complicating the wiring structure.

    The on-vehicle lamp lighting control circuit according to the present invention further includes means for smoothing the supplied pulse voltage, and a comparator for comparing the smoothed voltage with a threshold voltage, and the switching means includes the comparator. As a result of comparison, when the smoothed voltage is high, the switch is alternately connected and disconnected, and when the smoothed voltage is low, the switch is connected. .

  In the present invention, the pulse voltage is smoothed and compared with the threshold voltage. By smoothing, the voltage rises smoothly and takes time to become larger than the threshold voltage. For this reason, when a voltage with a small pulse width is supplied, the voltage does not become larger than the threshold voltage because the voltage falls before it becomes larger than the threshold voltage. In this case, since the switch is connected, the supplied pulse voltage is supplied as it is to the in-vehicle lamp. On the other hand, when a voltage with a large pulse width is supplied, the smoothed voltage becomes larger than the threshold voltage with the passage of time, and when it becomes larger, the switch is alternately switched between a connected state and a cut-off state. That is, the switch is PWM driven. Thereby, a pulsed voltage can be supplied to the on-vehicle lamp. Therefore, a pulsed voltage can be supplied to the light source regardless of the pulse width of the supplied pulse voltage.

  The on-vehicle lamp lighting control circuit according to the present invention is characterized in that the switch is connected in series to a license plate lamp.

  In the present invention, a license plate lamp can be newly added without complicating the wiring structure.

  Even if the types of the plurality of in-vehicle lamps are different, the power supply lines of the in-vehicle lamps can be shared, so that the complexity of the wiring structure can be suppressed. In addition, by sharing the power line, a new in-vehicle lamp can be easily added, and the design can be easily changed.

It is a schematic diagram which shows the structure of the vehicle-mounted lamp lighting control system provided with the vehicle-mounted lamp lighting control circuit which concerns on this invention. It is a circuit diagram which shows the structure of the control circuit for licenses. It is a timing chart of the voltage in each part of the control circuit for licenses. It is a circuit diagram which shows the structure of the control circuit for a stop. It is a timing chart of the voltage in each part of the control circuit for stop.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of an in-vehicle lamp lighting control circuit according to the invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing a configuration of an in-vehicle lamp lighting control system including an in-vehicle lamp lighting control circuit according to the present invention. The in-vehicle lamp lighting control system is a system that controls lighting of the rear lamps 10L and 10R, the license plate lamp 11, and the high-mount stop lamp 12. The rear lamps 10L and 10R are provided on the left and right of the rear part of the vehicle, and function as stop lamps and tail lamps by changing the brightness. Specifically, when the rear lamps 10L and 10R function as stop lamps, the rear lamps 10L and 10R light up more brightly (for example, five times the brightness) than when they function as tail lamps. The stop lamp is a lamp that lights up when the brake is depressed. The tail lamp is a lamp for notifying the following vehicle of the existence of the own vehicle at night or the like.

  The license plate lamp 11 is lit in conjunction with the tail lamp. The high-mount stop lamp 12 is a lamp that is installed at a high position at the rear of the vehicle (for example, at the top of the rear window) and lights in conjunction with the stop lamp. The license plate lamp 11 is a lamp for irradiating the license plate at the rear of the vehicle.

  Each of these lamps 10 to 12 includes current limiting resistors (hereinafter referred to as resistors) R1, R2, R3, and R4 and light emitting diodes L1, L2, L3, and L4, and the light emitting diodes L1, L2, L3, and L4 are grounded. It has a configuration connected in series. Each of the lamps 10 to 12 is lit when a voltage is applied from the power source Vb to the light emitting diodes L1, L2, L3, and L4. The number of light-emitting diodes included in each of the lamps 10 to 12 and the resistance value of the current limiting resistor are appropriately changed depending on the type or characteristics of each of the lamps 10 to 12.

  The in-vehicle lamp lighting control system includes a lamp driving circuit 1, a license control circuit (in-vehicle lamp lighting control circuit) 2, a stop control circuit (in-vehicle lamp lighting control circuit) 3, and the like. The lamp driving circuit 1 is connected between the power supply Vb and each of the lamps 10 to 12, and is a circuit that applies a voltage to the lamps 10 to 12 from the power supply Vb or cuts off the lamp. The lamp driving circuit 1 includes, for example, a switch (SW) 1a such as a MOS-type FET (Field-Effect Transistor) and a control unit 1b that controls the switching operation of the switch 1a.

  The switch 1a is connected between the power supply Vb and the lamps 10 to 12, and electrically connects or disconnects the power supply Vb and the lamps 10 to 12. Specifically, the power source Vb is connected to one of the contacts of the switch 1a, and the other is connected to the resistors R1 and R2 of the rear lamps 10L and 10R, the license control circuit 2 provided in the license plate lamp 11, and the high mount stop. Each of the stop control circuits 3 included in the lamp 12 is connected.

  The control unit 1b is a microcomputer including a CPU (Central Processing Unit) and a ROM (Read Only Memory). The control unit 1b is connected to a stop lamp switch (hereinafter referred to as stop SW) 15 for turning on and off the stop lamp and a tail lamp switch (hereinafter referred to as tail SW) 16 for turning on and off the tail lamp. The controller 1b detects the on / off state of the SWs 15 and 16, and controls the switching operation of the switch 1a.

  Specifically, the control unit 1b generates a pulse voltage having a different duty ratio in accordance with on / off of the stop SW 15 and the tail SW 16, and controls the switching operation of the switch 1a. When the stop SW 15 is turned on, the control unit 1b generates a pulse voltage having a duty ratio that can be turned on with sufficient brightness to cause the rear lamps 10L and 10R to function as a stop lamp, and the switching operation of the switch 1a. To control. In the present embodiment, the control unit 1b generates a pulse voltage with a duty ratio of 100%. In this case, the switch 1a is always on, and the rear lamps 10L and 10R connected to the switch 1a are lit as stop lamps.

  On the other hand, when the tail SW 16 is turned on, the control unit 1b generates a pulse voltage having a duty ratio capable of lighting the rear lamps 10L and 10R with sufficient brightness to cause the rear lamps 10L and 10R to function as a tail lamp, and switches the switch 1a. Control the behavior. In the present embodiment, the control unit 1b generates a pulse voltage with a duty ratio of 20%. In this case, the switch 1a is PWM driven. As a result, a pulse-shaped voltage whose duty ratio is adjusted (hereinafter referred to as pulse voltage) is applied to the rear lamps 10L and 10R connected to the switch 1a, and the rear lamps 10L and 10R are stopped. Lights as a tail lamp with reduced brightness compared to when it lights as a lamp.

  In this embodiment, the control unit 1b as a microcomputer controls the switching operation of the switch 1a. However, an ASIC (Application Specific Integrated Circuit) manufactured specifically for switching the switch 1a is used. May be used.

  The license control circuit 2 is mounted on the license plate lamp 11, and is connected between the switch 1a of the lamp driving circuit 1 and the resistor R3. The license control circuit 2 is a circuit for normally lighting the license plate lamp 11 regardless of the switching operation of the switch 1a. Specifically, as described above, different voltages are output from the lamp driving circuit 1 and applied to the license plate lamp 11 when the stop SW 15 is on and when the tail SW 16 is on. Therefore, the license control circuit 2 supplies a voltage for normally lighting the license plate lamp 11 to the light emitting diode L3 regardless of the voltage supplied from the lamp driving circuit 1.

  The stop control circuit 3 is mounted on the high-mount stop lamp 12, and is connected between the switch 1a of the lamp drive circuit 1 and the resistor R4. The stop control circuit 3 is a circuit for operating the high-mount stop lamp 12 normally regardless of the switching operation of the switch 1a. Similar to the license control circuit 2, the stop control circuit 3 supplies a voltage for normally lighting the high-mount stop lamp 12 to the light emitting diode L4 regardless of the voltage supplied from the lamp driving circuit 1.

  Hereinafter, specific configurations of the license control circuit 2 and the stop control circuit 3 will be described in detail. In the following description, the voltage input from the lamp driving circuit 1 to the license control circuit 2 and the stop control circuit 3 is the voltage Vin, and the voltage output from the license control circuit 2 and the stop control circuit 3 is the voltage Vout. And

  FIG. 2 is a circuit diagram showing a configuration of the license control circuit 2.

  The license control circuit 2 has a b-contact type relay switch 21. The relay switch 21 includes a relay contact 21a and a relay coil 21b, and the relay contact 21a is connected between the lamp driving circuit 1 (specifically, the switch 1a) and the resistor R3. One end of the relay coil 21 b is connected between the relay contact 21 a and the lamp drive circuit 1, and the other end is connected to the PWM drive circuit 22. An FET or a semiconductor relay may be used in place of the relay switch 21.

  The PWM drive circuit 22 is a circuit that controls the switching operation of the relay switch 21. The PWM drive circuit 22 is connected to the collector terminal of the transistor 28 whose emitter is grounded. When the transistor 28 described later is turned on, a current flows between the emitter and the collector. The PWM drive circuit 22 has a switch that electrically connects or disconnects the relay coil 21 and the collector terminal of the transistor 28, and performs switching control of the switch in accordance with on / off of the transistor 28.

  When the transistor 28 is on, the PWM drive circuit 22 performs switching control to repeatedly connect or disconnect the relay coil 21b and the transistor 28 electrically. As a result, the state where the current flows through the relay coil 21b and the state where the current does not flow are alternately repeated, and the relay contact 21a alternately becomes a contact state and a non-contact state. That is, the PWM drive circuit 22 PWM drives the relay switch 21 when the transistor 28 is on. Thereby, the voltage Vin input to the relay switch 21 becomes a pulse voltage (voltage Vout) and is supplied to the light emitting diode L3.

  On the other hand, when the transistor 28 is off, no current flows between the emitter and collector of the transistor 28. Therefore, even if the relay coil 21b and the transistor 28 are electrically connected, no current flows through the relay coil 21b. . Therefore, the relay contact 21a is always in a contact state. As a result, the voltage Vin is directly output from the relay switch 21 as the voltage Vout and supplied to the light emitting diode L3.

  The license control circuit 2 includes diodes 24 a and 24 b connected in parallel, and each anode is connected to the switch 1 a of the lamp driving circuit 1. The cathode of the diode 24a is connected to the (+) input of the comparator 26 through a low-pass filter 23 composed of a resistor 23a and a capacitor 23b. Therefore, the voltage V + obtained by smoothing the voltage Vin is input to the (+) input of the comparator 26.

  The cathode of the diode 24b is connected to each of the voltage dividing resistors 25a and 25b, the capacitor 29, and the resistor 27a connected in series. Between the voltage dividing resistors 25a and 25b connected in series, the (−) input of the comparator 26 is connected. That is, the voltage V− obtained by dividing the voltage Vin is input to the (−) input of the comparator 26.

  The comparator 26 compares the two input voltages V + and V−, and outputs a signal level voltage Vcp corresponding to the comparison result. Specifically, the comparator 26 outputs the Hi voltage Vcp when the voltage V + is large, and outputs the Low voltage Vcp when the voltage V− is large. The output terminal of the comparator 26 is connected to each of the resistors 27b and 27c. The resistor 27b is connected to the base of the transistor 28, and the resistor 27c is grounded.

  The transistor 28 is grounded at the emitter, and the collector is connected to the PWM drive circuit 22. The transistor 28 is turned on or off according to the voltage Vcp from the comparator 26. Specifically, when the voltage Vcp from the comparator 26 is Hi, the base current of the transistor 28 flows and the transistor 28 is turned on. As a result, a current flows between the emitter and collector of the transistor 28. On the other hand, when the voltage Vcp from the comparator 26 is Low, the base current of the transistor 28 stops flowing, and the transistor 28 is turned off. As a result, no current flows between the emitter and collector of the transistor 28.

  FIG. 3 is a timing chart of voltages in each part of the license control circuit 2. FIG. 3 shows a timing chart of the voltage Vin, the voltages V + and V−, the voltage Vcp, the voltage Vp, and the voltage Vout in order from the top. The voltage Vp is a voltage between the PWM drive circuit 22 and the transistor 28.

  When the tail SW 16 is on, that is, when the rear lamps 10L and 10R are lit as tail lamps, the pulsed voltage Vin is input to the license control circuit 2. The comparator 26 receives a voltage V + obtained by smoothing the voltage Vin by the low-pass filter 23 and a voltage V- obtained by dividing the voltage Vin. The comparator 26 compares the voltage V + and the voltage V− and outputs a voltage Vcp.

  Since the voltage Vin is a voltage obtained by smoothing the voltage Vin by the low-pass filter 23, the voltage V + increases smoothly when the voltage Vin rises and decreases smoothly when the voltage Vin falls. On the other hand, the voltage V− has a pulse shape with the same duty ratio as the voltage Vin. Therefore, when the voltage Vin rises, the voltage V + increases smoothly, and thus becomes smaller than the voltage V− that has become Hi, and the voltage V + becomes larger than the voltage V− over time. When the voltage Vin falls, the voltage V + decreases smoothly and thus becomes larger than the low voltage V-. When the tail SW 16 is on, the voltage Vin has a pulse shape, so that the voltage Vin and the voltage V− become Low before the voltage V + becomes larger than the voltage V−. Therefore, the comparator 26 outputs the Hi voltage Vcp at the timing when the voltage V− becomes Low, and outputs the Low voltage Vcp at the timing when the voltage V− becomes Hi.

  When the comparator 26 outputs the low voltage Vcp, the transistor 28 is turned off, so that no current flows between the emitter and collector of the transistor 28. When the Hi voltage Vcp is output, the transistor 28 is turned on, but since the voltage Vin is Low, no current flows through the relay coil 21b. As a result, the relay contact 21a is always in a contact state. As a result, the voltage Vin is supplied as it is to the light emitting diode L3 as the voltage Vout.

  On the other hand, when the stop SW 15 is on, that is, when the rear lamps 10L and 10R are turned on as stop lamps, the voltage Vin having a duty ratio of 100% is input to the license control circuit 2. At this time, since the voltage Vin increases smoothly by being smoothed by the low-pass filter 23 as described above, the voltage V− of Hi is larger than the voltage V + at the time of rising of the voltage Vin, and the comparator 26 has a low voltage. Outputs Vcp. As a result, the transistor 28 is turned off, so that no current flows between the emitter and collector of the transistor 28. As a result, no current flows through the relay coil 21b as described above, the relay contact 21a is always in contact, and the voltage Vout that is the same as the voltage Vin is output from the relay switch 21 and supplied to the light emitting diode L3.

  When time elapses from the input of the voltage Vin, the smoothed voltage V + becomes larger than the divided voltage V−, and the comparator 26 outputs the Hi voltage Vcp. As a result, the transistor 28 is turned on, and a current flows between the emitter and collector of the transistor 28. At this time, the PWM drive circuit 22 drives the relay switch 21 by PWM by repeating energization and interruption of the flowing current as described above. As a result, the voltage Vin becomes a pulsed voltage Vout and is supplied to the light emitting diode L3. The PWM drive circuit 22 drives the relay switch 21 by PWM so that the same pulse voltage as the pulse voltage output from the lamp drive circuit 1 is output from the license control circuit 2 when the tail SW 16 is on. Thus, the license control circuit 2 can supply the same pulse voltage to the light emitting diode L3 as when the tail lamp is lit even when the rear lamps 10L and 10R are lit as stop lamps.

  When the stop SW 15 and the tail SW 16 are off, that is, when the rear lamps 10L and 10R are turned off, no voltage is supplied to the license control circuit 2, so no voltage is supplied to the light emitting diode L3. not light.

  As described above, the license control circuit 2 can always supply the same pulse voltage to the light emitting diode L3 regardless of which of the stop SW15 and the tail SW16 is on. As a result, since the license plate lamp 11 is always lit with the same brightness, the license plate lamp 11 can be prevented from becoming too bright.

  FIG. 4 is a circuit diagram showing a configuration of the stop control circuit 3.

  The stop control circuit 3 has an a-contact type relay switch 31. The relay switch 31 includes a relay contact 31a and a relay coil 31b, and the relay contact 31a is connected between the lamp driving circuit 1 (specifically, the switch 1a) and the resistor R4. One end of the relay coil 31b is connected to the lamp drive circuit 1 side from the relay contact 31a, and the other end is connected to a transistor 38 whose emitter is grounded. Therefore, current flows through the relay coil 31b when the transistor 38 is on, and no current flows through the relay coil 31b when the transistor 38 is off. Note that an FET or a semiconductor relay may be used instead of the relay switch 31.

  The stop control circuit 3 includes diodes 32 a and 32 b connected in parallel, and each anode is connected to the switch 1 a of the lamp driving circuit 1. The cathode of the diode 32a is connected to the (+) input of the comparator 35 through a low-pass filter 33 including a resistor 33a and a capacitor 33b. Therefore, the voltage V + obtained by smoothing the voltage Vin is input to the (+) input of the comparator 35.

  The cathode of the diode 32 b is connected to each of the voltage dividing resistors 34 a and 34 b connected in series and the capacitor 36. Between the voltage-dividing resistors 34a and 34b connected in series, the (−) input of the comparator 35 is connected. That is, the voltage V− obtained by dividing the voltage Vin is input to the (−) input of the comparator 35.

  The comparator 35 compares the two input voltages V + and V−, and outputs a voltage Vcp corresponding to the comparison result. Specifically, the comparator 35 outputs the Hi voltage Vcp when the voltage V + is large, and outputs the Low voltage Vcp when the voltage V− is large. The output terminal of the comparator 35 is connected to the resistors 37a and 37b. The resistor 37a is connected to the base of the transistor 38, and the resistor 37b is grounded.

  The transistor 38 is grounded at the emitter, and the collector is connected to the relay coil 31 b of the relay switch 31. The transistor 38 is turned on or off according to the voltage Vcp from the comparator 35. Specifically, when the output voltage Vcp of the comparator 35 is Hi, the base current of the transistor 38 flows and the transistor 38 is turned on. As a result, a current flows between the emitter and collector of the transistor 38. On the other hand, when the output voltage Vcp of the comparator 35 is Low, the base current of the transistor 38 stops flowing, and the transistor 38 is turned off. As a result, no current flows between the emitter and collector of the transistor 38.

  FIG. 5 is a timing chart of the voltage at each part of the stop control circuit 3. FIG. 5 shows a timing chart of the voltage Vin, the voltages V + and V−, the voltage Vcp, and the voltage Vout in order from the top.

  When the stop SW 15 is on, that is, when the rear lamps 10L and 10R are turned on as stop lamps, the voltage Vin having a duty ratio of 100% is input to the license control circuit 2. At this time, the voltage V + and the voltage V− are input to the comparator 35. As described with reference to FIG. 3, when the voltage Vin is input, the voltage V− is higher than the voltage V +, and therefore the comparator 35 outputs the low voltage Vcp. As a result, since the transistor 38 is off, no current flows between the emitter and collector of the transistor 38. Thereby, since no current flows through the relay coil 31b, the relay contact 31a is always in a non-contact state, no voltage is supplied to the light emitting diode L4, and the license plate lamp 11 is not lit.

  When time elapses from the input of the voltage Vin, the smoothed voltage V + becomes larger than the voltage V-, and the comparator 35 outputs the Hi voltage Vcp. As a result, the transistor 38 is turned on, and a current flows between the emitter and collector of the transistor 38. As a result, a current flows through the relay coil 31b, the relay contact 31a enters a contact state, and the voltage Vin is directly output from the relay switch 31 as the voltage Vout and supplied to the light emitting diode L4.

  When the stop SW 15 and tail SW 16 are off, that is, when the rear lamps 10L and 10R are turned off, no voltage is supplied to the stop control circuit 3, so no voltage is supplied to the light emitting diode L4, and the license plate lamp 11 not light.

  When the tail SW 16 is on, that is, when the rear lamps 10L and 10R are lit as tail lamps, the pulsed voltage Vin is input to the stop control circuit 3. When the voltage Vin is Hi, the voltage V− is larger than the voltage V + when the voltage Vin is input as described above, and the comparator 35 outputs the Low voltage Vcp. When the voltage Vin becomes Low, the voltage Vin is smoothly reduced by being smoothed by the low-pass filter 32. Therefore, the voltage V + is larger than the voltage V-, and the comparator 26 outputs the Hi voltage Vcp.

  When the comparator 35 outputs the low voltage Vcp, the transistor 38 is turned off, so that no current flows between the emitter and collector of the transistor 38. Further, when outputting the Hi voltage Vcp, the transistor 38 is turned on, but since the voltage Vin is Low, no current flows through the relay coil 31b. As a result, the relay contact 31a is always in a non-contact state. Thereby, since the voltage Vin is interrupted by the relay switch 21, no voltage is supplied to the light emitting diode L3, and the high-mount stop lamp 12 is not lit.

  As described above, the stop control circuit 3 can turn on the high-mount stop lamp 12 in conjunction with the stop lamp by supplying a voltage to the light emitting diode L4 only when the stop SW 15 is on. When the tail SW 16 is on, the high-mount stop lamp 12 can be prevented from lighting by cutting off the voltage from the lamp driving circuit 1.

  The preferred embodiment of the present invention has been specifically described above, but each configuration, operation, and the like can be changed as appropriate, and are not limited to the above-described embodiment. For example, the elements constituting the license control circuit 2 and the stop control circuit 3 can be appropriately changed. Moreover, the magnitude | size of each resistance etc., the pulse width of the pulse voltage supplied from the lamp drive circuit 1, etc. can be suitably changed with the kind etc. of vehicle-mounted lamp. Furthermore, in the above-described embodiment, values such as the duty ratio are specifically shown, but these numerical values are examples and can be appropriately changed.

1 Lamp drive circuit 2 License control circuit (on-vehicle lamp lighting control circuit)
DESCRIPTION OF SYMBOLS 11 License plate lamp 12 High mount stop lamp 21 Relay switch 22 PWM drive circuit 26 Comparator 3 Stop control circuit (vehicle lamp lighting control circuit)
31 Relay switch 35 Comparator

Claims (5)

A switch connected in series with any of a plurality of in-vehicle lamps supplied with a common pulse voltage;
A vehicle-mounted lamp lighting control circuit comprising: switching means for switching the switch according to a pulse width of the pulse voltage. Means for smoothing the supplied pulse voltage;
A comparator for comparing the smoothed voltage with a threshold voltage;
The switching means is
As a result of comparison by the comparator, if the smoothed voltage is high, the switch is connected,
The on-vehicle lamp lighting control circuit according to claim 1, wherein when the smoothed voltage is low, the switch is turned off.   The on-vehicle lamp lighting control circuit according to claim 1, wherein the switch is connected in series to a high-mount stop lamp. Means for smoothing the supplied pulse voltage;
A comparator for comparing the smoothed voltage with a threshold voltage;
The switching means is
As a result of comparison by the comparator, when the smoothed voltage is high, the switch is alternately connected and disconnected,
The in-vehicle lamp lighting control circuit according to claim 1, wherein when the smoothed voltage is low, the switch is brought into a connected state.   5. The on-vehicle lamp lighting control circuit according to claim 1, wherein the switch is connected in series to a license plate lamp.

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