Lightning circuit

Abstract

To provide a lightning circuit capable of lighting and falling a plurality of light sources while suppressing a cost.SOLUTION: A lightning circuit of a first light source and a second light source, comprises: a first terminal in which a first power supply voltage is a predetermined period application when the first light source is in lighted; a second terminal of a second power supply voltage application when the second light source is in lighted; a switch between the second terminal and second light source; and a switch control circuit that turns off the switch in the case where the first power supply voltage is applied in the predetermined period to the first terminal in a state where the second power supply voltage is applied to the second terminal, and that turns on the switch in the case the first power supply voltage is not applied in the predetermined period to the first terminal. In the case where the switch control circuit is discharged for a first period when the first power supply voltage is applied to the first terminal in the predetermined period, and a capacitor to be charged and a charging voltage are higher than a predetermined threshold value in the second period that is not applied, a determination circuit for turning off the switch is contained, and a time when it exceeds a predetermined threshold value from a charging start to the capacitor is longer than the second period.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a lighting circuit.

Background Art

[0002] In general vehicles, a plurality of light sources (for example, high beam lamps, low beam lamps, DRL (Daytime Running Lamp), clearance lamps, turn signal lamps, etc.) are provided according to the use and function. And the vehicle has a lighting circuit for turning on or off these light sources (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, for example, when there is a light source constituting a turn signal lamp and another light source close to the turn signal lamp, it may be necessary to turn off the other light source while the turn signal lamp repeatedly turns on and off. To perform such control, it is conceivable to use a microcomputer, but using a microcomputer increases the cost of the lighting circuit.

[0005] An object of the present invention is to provide a lighting circuit that can turn on or off a plurality of light sources while suppressing costs.

Means for Solving the Problems

[0006] The main invention of the present invention for achieving the above object is a lighting circuit for lighting a first light source and a second light source used as a turn signal lamp, wherein when the first light source is lit, a first power supply voltage is applied to a first terminal at a predetermined period, when the second light source is lit, a second power supply voltage is applied to a second terminal, a switch located between the second terminal and the second light source, and when the second power supply voltage is applied to the second terminal and the first power supply voltage is applied to the first terminal at the predetermined period, the switch is turned off, and when the first power supply voltage is not applied to the first terminal at the predetermined period, the switch is turned on. The switch control circuit includes a capacitor that is discharged during a first period in which the first power supply voltage is applied to the first terminal in the predetermined period and is charged during a second period in which the first power supply voltage is not applied to the first terminal in the predetermined period, and a determination circuit that turns off the switch when a charging voltage generated in the capacitor is higher than a predetermined threshold value. The time from the start of charging the capacitor until the charging voltage exceeds the predetermined threshold value is longer than the second period. It is a lighting circuit.

Effect of the Invention

[0007] According to the present invention, it is possible to provide a lighting circuit that can light or turn off a plurality of light sources while suppressing costs.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0009] The following matters at least will become clear from the description of this specification and the attached drawings.

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or equivalent components, members, etc. shown in each drawing are denoted by the same reference numerals, and repeated explanations will be omitted as appropriate.

[0011] In addition, in this embodiment, "connection" means a state of being electrically connected unless otherwise specified. For this reason, "connection" includes cases where two components are connected not only by wiring but also, for example, via a resistor.

[0012] =====This Embodiment===== <<<Vehicle Lamp 1>>> FIG. 1 is a diagram showing an example of the configuration of a vehicle lamp 1. The vehicle lamp 1 includes light sources 10 and 20, a lighting circuit 30, an ignition switch SW, and a battery 40.

[0013] The light source 10 is a light source for a turn signal lamp (direction indicator lamp), and intermittently lights (flashes) based on the operation of the direction indicator by a vehicle user (for example, a driver). The light source 10 has a plurality (for example, two) of light emitting elements (here, light emitting diodes (LEDs)) connected in series, and is connected between a terminal Td and a terminal Te of the lighting circuit 30. Note that the terminal Te is grounded (not shown), and the light source 10 lights up when a drive current Iout1 is supplied from the lighting circuit 30 via the terminal Td.

[0014] The light source 20 is a light source for a clearance lamp (width lamp) that notifies the surroundings of the vehicle width and the presence of the vehicle, and is used, for example, when it is dim outside the vehicle. Note that the clearance lamp is often provided at a position close to the turn signal lamp and may be provided in the same housing. The clearance lamp is also referred to as a "small lamp" or a "position lamp". The light source 20 has a plurality of (for example, two) light emitting elements (here, light emitting diodes (LEDs)) connected in series, and is connected between the terminal Tf and the terminal Tg of the lighting circuit 30. Note that the terminal Tg is grounded (not shown), and the light source 20 lights up when the drive current Iout2 is supplied from the lighting circuit 30 via the terminal Tf.

[0015] The lighting circuit 30 is a circuit for controlling the light source 10 and the light source 20, and includes terminals Ta to Tg. The details of the configuration of the lighting circuit 30 in the present embodiment will be described later.

[0016] The lighting circuit 30 lights up or turns off the light source 10 based on the turn power supply voltage Vt applied to the terminal Ta via the power supply line L1a. Note that a switch (not shown), such as a mechanical contact relay or a non-contact relay using a semiconductor element, is provided between the power supply line L1a and the vehicle battery. In the lighting circuit 30, the line connected to the terminal Ta via the diode 101 (described later) is defined as the power supply line L1b.

[0017] Then, the switch is controlled to turn on and off at a predetermined cycle based on the vehicle driver operating the direction indicator or the hazard button. When the switch is on, the voltage of the battery (for example, 8V to 18V) is applied to the power supply line L1a. On the other hand, when the switch is off, the voltage of the battery is no longer applied to the power supply line L1a. As a result, due to the influence of the resistance and the circuit in the lighting circuit 30, the voltage of the power supply line L1a drops to zero.

[0018] Therefore, the turn power supply voltage Vt is a pulsed (rectangular) voltage in which a high level (hereinafter referred to as "H" level) and a low level (hereinafter referred to as "L" level) are alternately repeated at a predetermined period (for example, 1000 ms). In the following description, the turn power supply voltage Vt is also referred to as the turn voltage Vt. The turn voltage Vt is applied to the terminal Ta by turning on and off the switch.

[0019] Also, the lighting circuit 30 lights or extinguishes the light source 20 based on the clearance power supply voltage Vc applied to the terminal Tb via the power supply line L2a. An ignition switch SW is provided between the power supply line L2a and the vehicle battery 40. When the vehicle engine is turned on, the voltage of the battery (for example, 6V to 12V) is applied to the power supply line L2a. On the other hand, when the vehicle engine is stopped (turned off), the application of voltage to the power supply line L2a is stopped. That is, the clearance power supply voltage Vc is at the "H" level when the vehicle engine is on (ON) and at the "L" level when the engine is off (OFF). In the following description, the clearance power supply voltage Vc is also referred to as the CLL voltage Vc. As described above, both the turn voltage Vt and the CLL voltage Vc are voltages supplied from the vehicle battery. Also, the terminal Tc is grounded. In the lighting circuit 30, a line connected to the terminal Tb via a diode 115 (described later) is defined as the power supply line L2b.

[0020] Also, when the turn signal lamp and the clearance lamp are close to each other, it is preferable to turn off the clearance lamp during the blinking period of the turn signal lamp in order to maintain the visibility and emission color of the turn signal lamp.

[0021] <<Configuration of Lighting Circuit 30>> As shown in FIG. 2, the lighting circuit 30 includes resistors 100, 111, 112, diodes 101, 115, a PMOS transistor 110, a capacitor 113, a control circuit 114, and terminals Ta to Tg. Since the terminals Ta to Tg have been described in FIG. 1, their description is omitted. Also, terminal Ta corresponds to the "first terminal", and terminal Tb corresponds to the "second terminal".

[0022] The resistor 100 is an element that limits the drive current Iout1 supplied to the light source 10 when the turn-on voltage Vt at the "H" level is applied to terminal Ta. Note that the light source 10 corresponds to the "first light source", and the turn-on voltage Vt corresponds to the "first power supply voltage".

[0023] The diode 101 is an element that suppresses the lighting circuit 30 from being damaged by allowing current to flow in the opposite direction to the case where the voltage is correctly applied when terminal Ta is grounded and voltage Vt is applied to terminal Tc (i.e., reverse-connected). The anode of the diode 101 is connected to terminal Ta, and the cathode is connected to the resistor 100.

[0024] The PMOS transistor 110 is located between terminal Tb and the light source 20. When it is turned on, it supplies the drive current Iout2 to the light source 20, and when it is turned off, it stops the supply of the drive current Iout2. Note that the PMOS transistor 110 corresponds to the "switch". In this embodiment, a PMOS transistor 110 is used, but as the "switch", a PNP transistor may also be used.

[0025] The resistor 111 is an element that limits the drive current Iout2 supplied to the light source 20 when the PMOS transistor 110 is turned on. Note that the light source 20 corresponds to the "second light source".

[0026] Resistor 112 pulls up the gate electrode of PMOS transistor 110 to the CLL voltage Vc. Also, when the control circuit 114 outputs a voltage Vo that turns on the PMOS transistor 110, resistor 112 generates a voltage between the gate and source of the PMOS transistor 110. Note that the CLL voltage Vc corresponds to the "second power supply voltage".

[0027] Capacitor 113 is an element that stabilizes the voltage generated in resistor 112. Also, diode 115 is an element that suppresses damage to the lighting circuit 30 by allowing current to flow in the opposite direction when the terminal Tb is grounded and a voltage Vc is applied to the terminal Tc (i.e., reverse-connected), as opposed to when the voltage is applied correctly. Diode 115 has its anode connected to terminal Tb and its cathode connected to the source electrode of PMOS transistor 110. Note that the voltage of the power supply line L2b on the cathode side of diode 115 is a voltage Va that is lower than the CLL voltage Vc by the forward voltage of diode 115.

[0028] Control circuit 114 is a circuit that outputs a voltage Vo to turn on and off PMOS transistor 110 and controls whether to supply a drive current Iout2 to light source 20. Specifically, when a rectangular turn voltage Vt is applied to terminal Ta, control circuit 114 outputs a voltage Vo that turns off PMOS transistor 110. On the other hand, when a rectangular turn voltage Vt is not applied to terminal Ta and a CLL voltage Vc is applied to terminal Tb, control circuit 114 outputs a voltage Vo that turns on PMOS transistor 110. Note that when an "L" level CLL voltage Vc is applied to terminal Tb, control circuit 114 turns off PMOS transistor 110. Note that control circuit 114 corresponds to the "switch control circuit".

[0029] As shown in FIG. 3, the control circuit 114 includes a capacitor 150 and a determination circuit 151. The capacitor 150 is charged and discharged according to the turn voltage Vt. Specifically, the capacitor 150 is discharged during a period Tp in which a turn voltage Vt of "H" level is applied to terminal Ta while the CLL voltage Vc is applied to terminal Tb. On the other hand, the capacitor 150 is charged during a period Tp in which a turn voltage Vt of "L" level is applied to terminal Ta while the CLL voltage Vc is applied to terminal Tb. Also, let the voltage generated in the capacitor 150 be the charging voltage Vcap. Note that the period during which the turn voltage Vt of "H" level is applied corresponds to the "first period", and the period during which the turn voltage Vt of "L" level is applied corresponds to the "second period".

[0030] The determination circuit 151 outputs a voltage Vo for turning on and off the PMOS transistor 110 according to the charging voltage Vcap generated in the capacitor 150. Specifically, the determination circuit 151 turns on the PMOS transistor 110 when the charging voltage Vcap of the capacitor 150 is higher than a predetermined threshold value Vth. On the other hand, the determination circuit 151 turns off the PMOS transistor 110 when the charging voltage Vcap of the capacitor 150 is lower than a predetermined threshold value Vth. The determination circuit 151 includes a charge and discharge circuit 200, a voltage dividing circuit (DIV) 201, and a turn on / off circuit 202.

[0031] The charge and discharge circuit 200 is a circuit for charging and discharging the capacitor 150. Specifically, the charge and discharge circuit 200 discharges the capacitor 150 during a period Tp in which a turn voltage Vt of "H" level is applied. On the other hand, the charge and discharge circuit 200 charges the capacitor 150 according to the CLL voltage Vc during a period Tp in which a turn voltage Vt of "L" level is applied. The charge and discharge circuit 200 includes an NPN transistor 300, resistors 301, 304, 305, a Zener diode 302, and a capacitor 303.

[0032] The NPN transistor 300 is an element that is turned on when discharging the capacitor 150 during a period Tp in which a turn-on voltage Vt of "H" level is applied. Specifically, when a turn-on voltage Vt of "H" level is applied to the line L1a, a voltage corresponding to the turn-on voltage Vt is applied to the base electrode of the NPN transistor 300 via the diode 101, the resistor 301, and the Zener diode 302, and the NPN transistor 300 is turned on. Then, the base-emitter voltage of the NPN transistor 300 is stabilized by the capacitor 303.

[0033] On the other hand, when a turn-on voltage Vt of "L" level is applied to the line L1a, the turn-on voltage Vt is applied to the base electrode of the NPN transistor 300 via the diode 101, the resistor 301, and the Zener diode 302, and the NPN transistor 300 is turned off. The Zener diode 302 is an element that reduces the turn-on voltage Vt of "H" level to a voltage level that can be applied to the base electrode of the NPN transistor. Also, the NPN transistor 300 corresponds to a "transistor".

[0034] The resistor 304 is an element that limits the discharge current when the NPN transistor 300 is turned on and the capacitor 150 is discharged. Also, the resistor 304 and the NPN transistor 300 are connected in parallel to the capacitor 150. The resistor 304 corresponds to a "second resistor".

[0035] The resistor 305 is an element that limits the charging current when the capacitor 150 is charged with a voltage Va corresponding to the "H" - level CLL voltage Vc while the NPN transistor 300 is off. Note that the resistance value of the resistor 305 is larger than that of the resistor 304. Also, the resistance value of the resistor 305 is set such that the period Tsh until the capacitor 150 is charged and exceeds a predetermined threshold value Vth is longer than the period Tp (for example, 500 ms) during which the "L" - level turn - on voltage Vt is applied when the light source 10 blinks. In other words, the time Tsh from the start of charging the capacitor 150 until the charging voltage Vcap exceeds the divided - voltage Vdiv (described later) which is the threshold value Vth is longer than the period Tp during which the "L" - level turn - on voltage Vt is applied. Note that the period Tp can be considered to be from 250 ms to 500 ms (that is, the predetermined period is from 500 ms to 1000 ms, and the frequency at which the light source 10 blinks is, on average, 1.5 Hz). Therefore, the time Tsh is set to be longer than the maximum value of the period Tp, for example, 600 ms. Also, the resistor 305 corresponds to the "first resistor".

[0036] The voltage - dividing circuit 201 is a circuit that divides the voltage Va. Specifically, the voltage - dividing circuit 201 includes resistors 310 and 311 that divide the voltage Va, and generates a divided - voltage Vdiv according to the voltage - dividing ratio of the resistors 310 and 311. Note that the divided - voltage Vdiv indicates a predetermined threshold value Vth.

[0037] The on - off circuit 202 is a circuit that generates a voltage Vo for turning the PMOS transistor 110 on and off based on the charging voltage Vcap and the divided - voltage Vdiv. Specifically, when the charging voltage Vcap is higher than the divided - voltage Vdiv, the on - off circuit 202 generates a voltage Vo for turning the PMOS transistor 110 on. On the other hand, when the charging voltage Vcap is lower than the divided - voltage Vdiv, the on - off circuit 202 generates a voltage Vo for turning the PMOS transistor 110 off. The on - off circuit 202 is composed of a comparator 320, an NPN transistor 321, and a resistor 322.

[0038] Comparator 320 is a circuit that compares the charging voltage Vcap with the divided voltage Vdiv and outputs the voltage Von. Specifically, when the charging voltage Vcap is higher than the divided voltage Vdiv, comparator 320 outputs a voltage Von at the "H" level (i.e., voltage Va). On the other hand, when the charging voltage Vcap is lower than the divided voltage Vdiv, comparator 320 outputs a voltage Von at the "L" level (i.e., the ground voltage).

[0039] The NPN transistor 321 is an element that turns on and off according to the voltage Von and turns on and off the PMOS transistor 110. Specifically, the NPN transistor 321 turns on based on the voltage Von at the "H" level and turns on the PMOS transistor. On the other hand, the NPN transistor 321 turns off based on the voltage Von at the "L" level and turns off the PMOS transistor.

[0040] Resistor 322, together with resistor 112 in FIG. 2, constitutes a voltage dividing circuit and generates a voltage Vo that turns on and off the PMOS transistor based on the output of the NPN transistor 321. Specifically, when the NPN transistor 321 is turned on and outputs the ground voltage, resistors 112 and 322 output a voltage Vo obtained by dividing the voltage Va and turn on the PMOS transistor 110. On the other hand, when the NPN transistor 321 is turned off, resistors 112 and 322 set the voltage Vo to the voltage Va and turn off the PMOS transistor 110. This is because resistor 112 pulls up the gate electrode of the PMOS transistor 110.

[0041] <<Operation of the vehicle lamp 1 according to the present embodiment>> FIG. 4 is a diagram for explaining an example of the operation of the vehicle lamp 1 according to the present embodiment. In FIG. 4, between times t0 and t4, the light source 10 blinks and the light source 20 is off. Between times t4 and t6, the light source 10 is off and the light source 20 is on. Between times t6 and t10, the light source 10 blinks when the light source 20 is on. After time t10, the light source 10 is off and the light source 20 is on. It is assumed that the ignition switch SW is off before time t0.

[0042] At time t0, when the "L" level CLL voltage Vc is applied to terminal Tb, the turn signal indicator or hazard button is operated by the vehicle driver, and the "H" level turn voltage Vt is applied to terminal Ta. Also, since the CLL voltage Vc is the ground voltage, the comparator 320 outputs the voltage Von which is the ground voltage, and the NPN transistor 321 turns off. Therefore, the PMOS transistor 110 turns off, so the lighting circuit 30 turns off the light source 20 and turns on the light source 10.

[0043] At time t1, with the "L" level CLL voltage Vc still applied to terminal Tb, the "L" level turn voltage Vt is applied to terminal Ta. Also in this case, since the PMOS transistor 110 turns off, the lighting circuit 30 turns off the light sources 10 and 20.

[0044] At time t2, with the "L" level CLL voltage Vc still applied to terminal Tb, the "H" level turn voltage Vt is applied to terminal Ta. In this case, similar to time t0, the lighting circuit 30 turns off the light source 20 and turns on the light source 10.

[0045] At time t3, with the "L" level CLL voltage Vc still applied to terminal Tb, the "L" level turn voltage Vt is applied to terminal Ta. In this case, similar to time t1, the lighting circuit 30 turns off the light sources 10 and 20.

[0046] At time t4, the driver turns on the ignition switch SW, and the "H" level CLL voltage Vc is applied to terminal Tb. Also, the voltage dividing circuit 201 generates a divided voltage Vdiv obtained by dividing the voltage Va. Then, the charge and discharge circuit 200 starts charging the capacitor 150 with the voltage Va via the resistor 305. On the other hand, since the charging voltage Vcap is lower than the divided voltage Vdiv, the comparator 320 outputs a voltage Von which is the ground voltage, turning off the NPN transistor 321. And based on the voltage Vo which is the voltage Va, the PMOS transistor 110 is turned off. Therefore, when the "H" level turn voltage Vt is not applied, the lighting circuit 30 turns off the light sources 10 and 20.

[0047] At time t5, when the charging voltage Vcap becomes equal to the divided voltage Vdiv, the comparator 320 outputs a voltage Von which is the voltage Va, turning on the NPN transistor 321. And the resistors 112 and 322 in FIG. 3 generate a voltage Vo for turning on the PMOS transistor 110. As a result, the PMOS transistor 110 is turned on, and the lighting circuit 30 turns on the light source 20.

[0048] At time t6, when the "H" level CLL voltage Vc is applied to terminal Tb, the driver of the vehicle operates the direction indicator or the hazard button, and the "H" level turn voltage Vt is applied to terminal Ta. In this case, the NPN transistor 300 is turned on, and the capacitor 150 is discharged. And since the charging voltage Vcap becomes lower than the divided voltage Vdiv, the comparator 320 outputs a voltage Von which is the ground voltage. Then, the NPN transistor 321 is turned off, and the PMOS transistor 110 is also turned off. As a result, the lighting circuit 30 turns off the light source 20 and turns on the light source 10.

[0049] At time t7, while the "H" level CLL voltage Vc is applied to terminal Tb, the "L" level turn voltage Vt is applied to terminal Ta. In this case, the capacitor 150 is charged by the resistor 305, and although the charging voltage Vcap is lower than the divided voltage Vdiv, the charging voltage Vcap rises. However, since the charging voltage Vcap is lower than the divided voltage Vdiv, the comparator 320 outputs the voltage Von which is the ground voltage. Then, the NPN transistor 321 is turned off, and the PMOS transistor 110 is also turned off. As a result, the lighting circuit 30 turns off the light sources 10 and 20.

[0050] At time t8, while the "H" level CLL voltage Vc is applied to terminal Tb, the "H" level turn voltage Vt is applied to terminal Ta. In this case, similar to time t16, the lighting circuit 30 turns off the light source 20 while turning on the light source 10.

[0051] At time t9, while the "H" level CLL voltage Vc is applied to terminal Tb, the "L" level turn voltage Vt is applied to terminal Ta. In this case, similar to time t7, the lighting circuit 30 turns off the light sources 10 and 20. Thus, when the "H" level CLL voltage Vc is applied to terminal Tb and the "H" level turn voltage Vt is applied to terminal Ta while the light source 20 is lit, the light source 20 is turned off and the light source 10 blinks. Thereby, without using a microcomputer, during the blinking period of the turn signal lamp, the clearance lamp can be turned off to maintain the visibility and emission color of the turn signal lamp.

[0052] At time t10, when the charging voltage Vcap of the capacitor 150 that started charging from time t9 becomes equal to the divided voltage Vdiv, the lighting circuit 30 turns on the light source 20 while keeping the light source 10 turned off.

[0053] As described above, generally, when it is necessary to blink the light source 10 (for example, a turn signal lamp) while the light source 20 (for example, a clearance lamp) is lit, the light source 20 will be turned off. And thus, the control for discriminating the lighting and extinguishing of each of the light sources 10 and 20 and giving priority to the lighting of the light source 10 can be performed using a microcomputer. However, using a microcomputer will increase the cost of the lighting circuit 30. Therefore, in the lighting circuit 30 of the present embodiment, the above-described control is performed using an analog circuit without using a microcomputer.

[0054] Thereby, it is possible to provide a lighting circuit that can light or extinguish a plurality of light sources without increasing the cost.

[0055] ===Summary=== As described above, the lighting circuit 30 of the present embodiment has been described. The lighting circuit 30 includes terminals Ta and Tb, a PMOS transistor 110, and a control circuit 114, and the control circuit 114 includes a capacitor 150 and a determination circuit 151. Thereby, it is possible to provide a lighting circuit that can light or extinguish a plurality of light sources while suppressing the cost.

[0056] The determination circuit 151 includes a charge and discharge circuit 200, a voltage dividing circuit 201, and an on-off circuit 202. Thereby, even when it is necessary to light the turn signal lamp while the clearance lamp is lit without using a microcomputer, the visibility and emission color of the turn signal lamp are maintained.

[0057] Further, the charge and discharge circuit 200 includes a resistor 305, a resistor 304, and an NPN transistor 300. Thereby, when a CLL voltage Vc of “H” level is applied to the terminal Tb and a turn voltage Vt of “L” level is applied to the terminal Ta for a time longer than a predetermined time (for example, 600 ms), the light source 20 lights up.

[0058] The above-described embodiments are for facilitating the understanding of the present invention and are not for limiting the interpretation of the present invention. Further, the present invention can be changed and improved without departing from its gist, and it goes without saying that equivalents of the present invention are included therein.

Explanation of Signs

[0059] 1 Vehicle lamp 10, 20 Light source 30 Lighting circuit 40 Battery 100, 111, 112, 301, 304, 305, 310, 311, 322 Resistor 110 Transistor 113, 150, 303 Capacitor 114 Control circuit 151 Judgment circuit 200 Charge and discharge circuit 201 Voltage dividing circuit 202 On-off circuit 300, 321 NPN transistor 302 Zener diode 320 Comparator

Claims

1. A lighting circuit that lights a first light source and a second light source used as a turn signal lamp, When lighting the first light source, a first terminal to which a first power supply voltage is applied at a predetermined period, When lighting the second light source, a second terminal to which a second power supply voltage is applied, A switch located between the second terminal and the second light source, When the first power supply voltage is applied to the first terminal at the predetermined period in a state where the second power supply voltage is applied to the second terminal, the switch is turned off, and when the first power supply voltage is not applied to the first terminal at the predetermined period, a switch control circuit that turns on the switch, Comprising, The switch control circuit, A capacitor that is discharged during a first period in which the first power supply voltage is applied to the first terminal in the predetermined period and is charged during a second period in which the first power supply voltage is not applied to the first terminal in the predetermined period, A determination circuit that turns on the switch when a charging voltage generated in the capacitor is higher than a predetermined threshold value, Including, The time from the start of charging the capacitor until the charging voltage exceeds the predetermined threshold value is longer than the second period, Lighting circuit.

2. The lighting circuit according to claim 1, The determination circuit, A charge and discharge circuit that discharges the capacitor during the first period and charges the capacitor according to the second power supply voltage during the second period, A voltage dividing circuit that divides the second power supply voltage, An on-off circuit that turns the switch on and off based on the charging voltage generated in the capacitor and the divided voltage of the voltage dividing circuit, Lighting circuit including.

3. The lighting circuit according to claim 2, The charge and discharge circuit, A first resistor connected between the second terminal and the capacitor, A second resistor and a transistor connected in parallel to the capacitor, Including, The transistor is turned on during the first period and turned off during the second period, The resistance value of the first resistor is larger than the resistance value of the second resistor, The on-off circuit, When the charging voltage is higher than the divided voltage, the switch is turned on, and when the charging voltage is lower than the divided voltage, the switch is turned off, Lighting circuit.

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