Lighting circuit and lighting device

Abstract

The present invention selectively drives a first light source and a second light source to emit light with a simple configuration. This lighting circuit supplies a driving current to the first light source and the second light source. The lighting circuit comprises: a lighting drive circuit which performs first lighting driving that is connected to a first power supply line and supplies a driving current to the first light source according to a voltage level of the first power supply line, and second lighting drive that is connected to a second power supply line and supplies a driving current to the second light source according to a voltage level of the second power supply line; a detection circuit that detects lighting of the first light source on the basis of a voltage of the first power supply line; and a cutoff circuit that has a switch connected to the second power supply line and opens the switch to cut off the second power supply line when the detection circuit detects the lighting of the first light source.

Description

Lighting circuit and lighting device

[0001] The technology disclosed in this specification relates to a lighting circuit and a lighting device.

[0002] Conventionally, lighting circuits that selectively drive and turn on a plurality of light sources have been known. For example, a vehicle lamp includes various lamps as light sources, such as headlights, daytime running lamps, clearance lamps, turn signal lamps, tail lamps, and stop lamps, and a lighting circuit. The lighting circuit selectively drives and turns on the daytime running lamps and the clearance lamps, for example. In conventional lighting circuits, a shutoff circuit is provided between an output line that supplies drive current from a light-projecting drive circuit to the daytime running lamps, and the shutoff circuit is configured to shut off the output line when the clearance lamps are turned on (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2018-198173

[0004] However, in conventional lighting circuits, as described above, the interrupter circuit is provided in the output line between the lighting drive circuit and the light source, which means that the circuit configuration between the daytime running lamp and the lighting drive circuit is easily affected. Note that this problem is not limited to daytime running lamps and clearance lamps, but is also a common problem with lighting circuits that selectively drive the lighting of multiple other types of light sources.

[0005] This specification discloses a technique that can solve the above-mentioned problems.

[0006] The technology disclosed in this specification can be realized, for example, in the following forms.

[0007] (1) A lighting circuit disclosed in this specification is a lighting circuit that supplies drive currents to a first light source and a second light source. The lighting circuit includes: a lighting drive circuit connected to a first power supply line that performs a first lighting drive that supplies a drive current to the first light source in accordance with a voltage level of the first power supply line; a lighting drive circuit connected to a second power supply line that performs a second lighting drive that supplies a drive current to the second light source in accordance with a voltage level of the second power supply line; a detection circuit that detects lighting of the first light source based on the voltage of the first power supply line; and a shutoff circuit that has a switch connected to the second power supply line and that opens the switch to shut off the second power supply line when the detection circuit detects lighting of the first light source.

[0008] In this lighting circuit, the cutoff circuit (switch) for disabling the second lighting drive for the second light source is provided in the power supply line between the external device and the lighting drive circuit, rather than in the output line (current supply line) between the lighting drive circuit and the light source. Therefore, with this lighting circuit, it is possible to selectively drive the first light source and the second light source with a simple configuration that is less affected by the circuit configuration between the second light source and the lighting drive circuit, compared to a configuration in which, for example, a cutoff circuit is provided in the output line between the lighting drive circuit and the light source.

[0009] (2) In the above-described lighting circuit, the lighting drive circuit may have a reverse connection protection diode electrically connected to the second power supply line, and a reverse connection protection FET may be electrically connected to the second power supply line upstream of the detection circuit and the cutoff circuit. When an external device is reverse-connected to the second power supply line, it is necessary to protect the detection circuit and the cutoff circuit (switch) electrically connected to the second power supply line. In contrast, this lighting circuit can achieve reverse connection protection while preventing a voltage drop caused by the diode from preventing the lighting drive circuit from receiving a voltage sufficient to light the second light source, compared to a configuration in which a reverse connection protection diode is also connected upstream of the switch and the detection circuit.

[0010] (3) In the lighting circuit described above, a negative surge protection diode may be electrically connected to the second power supply line in a stage preceding the detection circuit and the cutoff circuit. In a configuration in which a reverse connection protection FET is electrically connected to the second power supply line, a negative surge may pass through the reverse connection protection FET, making it impossible to protect the detection circuit and the cutoff circuit. In contrast, with this lighting circuit, even if a negative surge passes through the reverse connection protection FET, the detection circuit and the cutoff circuit can be protected by the negative surge protection diode.

[0011] (4) In the lighting circuit described above, the lighting drive circuit may have a positive surge protection capacitor electrically connected to the second power supply line, and a positive surge protection Zener diode may be electrically connected to the second power supply line upstream of the detection circuit and the interruption circuit. When a positive surge occurs on the second power supply line, it is necessary to protect the detection circuit and the interruption circuit (switch) electrically connected to the second power supply line. In contrast, this lighting circuit can reduce the inrush current flowing through the second power supply line compared to a configuration in which a positive surge protection capacitor is also connected upstream of the switch and the detection circuit.

[0012] (5) The lighting device may be configured to include the first light source, the second light source, and the lighting circuit. With this configuration, the first light source and the second light source can be selectively driven to light using a simple configuration that is not easily affected by the circuit configuration of the second light source and the lighting drive circuit.

[0013] (6) In the lighting device described above, the lighting device may be mounted on a vehicle, the light-emitting surface of the first light source and the light-emitting surface of the second light source may be disposed adjacent to each other or may be shared, the first light source may be a light source for a turn signal lamp, and the second light source may be a light source for a daytime running lamp. With this configuration, the turn signal lamp and the daytime running lamp can be selectively driven to light using a simple configuration that is not easily affected by the circuit configuration of the daytime running lamp and the lighting drive circuit.

[0014] The technology disclosed in this specification can be realized in various forms, for example, in the form of a lighting circuit, a lamp device including the lighting circuit and multiple light sources, etc.

[0015] 2A is an example of a common light-emitting surface of the light source unit, and FIG. 2B is an example of a configuration in which the light-emitting surfaces of the turn signal lamps and the daytime running lamps are arranged close to each other. FIG. 2B is a time chart showing the transition of the on / off states of the turn signal lamps and the daytime running lamps. FIG. 2C is an explanatory diagram showing the circuit configuration of a lighting circuit.

[0016] A. Embodiments: A-1. Configuration of Vehicle Lamp 10: Fig. 1 is a block diagram showing a schematic configuration of a vehicle lamp 10 in this embodiment. As shown in Fig. 1, the vehicle lamp 10 is a lamp mounted on a vehicle, and includes a light source unit 21 and a lighting circuit 40. The vehicle lamp 10 is an example of a lighting device.

[0017] The light source unit 21 includes turn signal lamps 20 and daytime running lamps 30. The turn signal lamps 20 function as direction indicators and illuminate in various patterns to indicate left or right turns, lane changes, and the like. Specifically, the turn signal lamps 20 have a configuration in which, for example, multiple first light-emitting elements 22 (such as LEDs) are connected in series. The daytime running lamps 30 function as daytime running lights and, in principle, are always illuminated while the vehicle is traveling. Specifically, the daytime running lamps 30 have a configuration in which, for example, multiple second light-emitting elements 32 (such as LEDs) are connected in series. The turn signal lamps 20 are an example of a first light source, and the daytime running lamps 30 are an example of a second light source.

[0018] 2A and 2B are explanatory diagrams showing the light-emitting surface of the light source unit 21. Fig. 2A illustrates a common light-emitting surface 24 of the light source unit 21. The common light-emitting surface 24 is the light-emitting surface of the turn signal lamps 20 and also the light-emitting surface of the daytime running lamps 30. Specifically, behind the common light-emitting surface 24, a plurality of first light-emitting elements 22 and a plurality of second light-emitting elements 32 are arranged side by side along the extension direction of the common light-emitting surface 24.

[0019] 2B illustrates a configuration in which the light-emitting surface 24A of the turn signal lamp 20 and the light-emitting surface 24B of the daytime running lamp 30 are disposed in close proximity to each other. Behind the light-emitting surface 24A, a plurality of first light-emitting elements 22 are disposed in a row along the extension direction of the light-emitting surface 24A. Behind the light-emitting surface 24B, a plurality of second light-emitting elements 32 are disposed in a row along the extension direction of the light-emitting surface 24B. In a configuration in which the light-emitting surface of the turn signal lamp 20 and the light-emitting surface of the daytime running lamp 30 are shared or disposed in close proximity to each other, for example, legal regulations may require that the daytime running lamp 30 be turned off while the turn signal lamp 20 is on.

[0020] The lighting circuit 40 is a circuit that supplies drive current to the turn signal lamps 20 and the daytime running lamps 30. The lighting circuit 40 includes a lighting drive circuit 50 and an arbitration circuit 60. In this embodiment, the lighting drive circuit 50 and the arbitration circuit 60 are formed on different circuit boards and are electrically connected to each other via wiring. Therefore, by electrically connecting the arbitration circuit 60 between the lighting circuit 40 and the ECU 80 (described below), the daytime running lamps 30 can be turned off while the turn signal lamps 20 are turned on.

[0021] The lighting drive circuit 50 has an input terminal P7 electrically connected to a turn power line Lt connected to an ECU (Electronic Control Unit) 80 for the vehicle. The ECU 80 supplies a turn signal St for the turn signal lamp 20 to the turn power line Lt. The turn signal St for the turn signal lamp 20 has a turn voltage Vt for turning on the turn signal lamp 20. In this embodiment, the turn signal St for the turn signal lamp 20 is a pulse signal in which the turn voltage Vt changes in a pulsed manner (see FIG. 3 described below). The lighting drive circuit 50 is electrically connected to the turn signal lamp 20 (first light-emitting element 22). When the turn voltage Vt is applied to the turn power line Lt, the lighting drive circuit 50 supplies a drive current to the turn signal lamp 20 to turn it on.

[0022] Furthermore, the lighting drive circuit 50 has an input terminal P8 electrically connected to a DRL power supply line Ld connected to the ECU 80. The ECU 80 supplies a daytime running lamp 30 illumination instruction signal Sd to the DRL power supply line Ld. The daytime running lamp 30 illumination instruction signal Sd has a DRL voltage Vd for turning on the daytime running lamps 30. In this embodiment, the daytime running lamp 30 illumination instruction signal Sd is a signal in which the DRL voltage Vd is at a substantially constant level (see FIG. 3 , described below). The lighting drive circuit 50 is electrically connected to the daytime running lamps 30 (second light-emitting element 32). When the DRL voltage Vd is supplied to the DRL power supply line Ld, the lighting drive circuit 50 supplies a drive current to the daytime running lamps 30 to turn on the lamps.

[0023] The lighting drive circuit 50 has an input terminal P9 electrically connected to a GND line Lg connected to the ECU 80. In this embodiment, the ECU 80 does not perform control to turn off the daytime running lamps 30 while the turn signal lamps 20 are on.

[0024] The arbitration circuit 60 is electrically connected between the ECU 80 and the lighting drive circuit 50. Specifically, the TURN power supply line Lt is formed on the substrate of the arbitration circuit 60 from the input terminal P1, led out of the arbitration circuit 60 via the output terminal P4, and electrically connected to the input terminal P7 of the lighting drive circuit 50. The DRL power supply line Ld is formed on the substrate of the arbitration circuit 60 from the input terminal P2, led out of the arbitration circuit 60 via the output terminal P5, and electrically connected to the input terminal P8 of the lighting drive circuit 50. The GND line Lg is formed on the substrate of the arbitration circuit 60 from the input terminal P3, led out of the arbitration circuit 60 via the output terminal P6, and electrically connected to the input terminal P9 of the lighting drive circuit 50.

[0025] The lighting circuit 40 includes a switch 62, an on / off control circuit 64, a detection circuit 66, a timer circuit 68, and a constant voltage circuit 70. The switch 62 and the on / off control circuit 64 are an example of a shutoff circuit.

[0026] The switch 62 is connected to the DRL power supply line Ld. When the switch 62 is closed, the light-on instruction signal Sd from the ECU 80 can be supplied to the lighting drive circuit 50 via the DRL power supply line Ld. When the switch 62 is open, the DRL power supply line Ld is interrupted, and the light-on instruction signal Sd from the ECU 80 is prohibited from being supplied to the lighting drive circuit 50. In other words, when the switch 62 is open, the daytime running lamps 30 are turned off regardless of whether the light-on instruction signal Sd from the ECU 80 is present or absent.

[0027] The detection circuit 66 detects the illumination of the turn signal lamps 20 based on the output of the turn voltage Vt on the turn power line Lt. That is, the detection circuit 66 detects whether or not a turn-on instruction signal St is output from the ECU 80. When the detection circuit 66 detects the turn-on instruction signal St, a detection signal indicating the detection of the turn-on instruction signal St is provided to the on / off control circuit 64 via the timer circuit 68. The on / off control circuit 64 closes the switch 62 when it does not receive the detection signal, and opens the switch 62 when it receives the detection signal. As a result, the daytime running lamps 30 are extinguished while the turn signal lamps 20 are illuminated. In this embodiment, when the turn-on instruction signal St is received from the ECU 80, the turn signal lamps 20 are illuminated instantaneously (e.g., several milliseconds or more, but not more than several tens of milliseconds) shorter than a monitoring time Tm (described later).

[0028] The timer circuit 68 begins counting a monitoring time (e.g., 350 ms or more, 400 ms) from the point at which it no longer receives a detection signal from the detection circuit 66. The timer circuit 68 outputs an allowance instruction to the on / off control circuit 64 to allow the switch 62 to change from an open state to a closed state, provided that the state of not receiving a detection signal continues for a monitoring time tm (longer than the off time of the TURN voltage Vt). After opening the switch 62, the on / off control circuit 64 maintains the switch 62 in the open state until it receives an allowance instruction from the on / off control circuit 64. Upon receiving the allowance instruction, the on / off control circuit 64 returns the switch 62 to the closed state. In this way, the daytime running lamps 30 are allowed to turn on only after the turn signal lamps 20 have been completely extinguished, effectively preventing the turn signal lamps 20 and the daytime running lamps 30 from turning on simultaneously.

[0029] The constant voltage circuit 70 is connected between the DRL power supply line Ld and the GND line Lg, and generates a constant voltage to be supplied to the timer circuit 68. The timer circuit 68 counts a period of time corresponding to the constant voltage supplied from the constant voltage circuit 70 as a monitoring time. The arbitration circuit 60 is equipped with an input filter 72 and an output filter 76 as countermeasures against static electricity on the TURN power supply line Lt. The arbitration circuit 60 is also equipped with an input filter 74 and an output filter 78 as countermeasures against static electricity on the DRL power supply line Ld.

[0030] FIG. 3 is a time chart showing the transition of the on / off states of the turn signal lamps 20 and the daytime running lamps 30. As shown in FIG. 3, the ECU 80 does not output the turn-on instruction signal St or the turn-on instruction signal Sd during the period prior to time t0, so both the turn signal lamps 20 ("TURN" in FIG. 3) and the daytime running lamps 30 ("DRL" in FIG. 3) are off ("OFF" in FIG. 3). When the turn-on instruction signal Sd is output from the ECU 80 at time t0, the timer circuit 68 in the arbitration circuit 60 functions and turns on the daytime running lamps 30 ("ON" in FIG. 3, see time t1) provided that a state in which a detection signal indicating that the turn signal lamps 20 are turned on has continued for a monitoring time tm. In this way, in this embodiment, simultaneous illumination of the turn signal lamps 20 and the daytime running lamps 30 is reliably avoided even when the daytime running lamps 30 are turned on individually.

[0031] Next, when the ECU 80 outputs a turn-on instruction signal St while the daytime running lamps 30 are on, the switch 62 in the arbitration circuit 60 opens. This causes the daytime running lamps 30 to turn off and the turn signal lamps 20 to turn on, despite the fact that the ECU 80 is outputting a turn-on instruction signal Sd (see time t2). In this embodiment, the turn-on instruction signal St is a pulse signal, so the turn signal lamps 20 pulse-on. When the ECU 80 no longer outputs the turn-on instruction signal St, the turn signal lamps 20 turn off (see time t3). However, at this point, the daytime running lamps 30 do not turn on. As described above, the timer circuit 68 in the arbitration circuit 60 functions, and the daytime running lamps 30 turn on (see time t4) if the state in which a detection signal indicating that the turn signal lamps 20 are on has not been received continues for the monitoring time tm.

[0032] A-2. Configuration for Protecting the Lighting Circuit 40: FIG. 4 is an explanatory diagram showing the circuit configuration of the lighting circuit 40. Note that the GND line Lg is omitted from FIG. 4. As shown in FIG. 4, in the lighting drive circuit 50, a diode 56 and a positive surge protection capacitor 58 are electrically connected to the connection line between the input terminal P7 and the turn signal lamp 20. The diode 56 serves to protect the internal circuitry of the lighting drive circuit 50 in the event that an external device (such as the ECU 80) is electrically reverse-connected to the TURN power supply line Lt. The positive surge protection capacitor 58 serves to absorb surges and remove conducted noise from the TURN power supply line Lt. In addition, in the lighting drive circuit 50, a diode 52 and a positive surge protection capacitor 54 are electrically connected to the connection line between the input terminal P8 and the daytime running lamp 30. The diode 52 serves to protect the internal circuitry of the lighting drive circuit 50 in the event that an external device (such as the ECU 80) is electrically reverse-connected to the DRL power supply line Ld. The positive surge protection capacitor 54 serves to absorb surges and remove conducted noise from the DRL power supply line Ld.

[0033] The switch 62 has a cutoff FET (field effect transistor) 62 a. A Zener diode 62 d, a capacitor 62 c, and a resistor element 62 d are connected in parallel between the drain and source of the cutoff FET 62 a. The on / off control circuit 64 has a transistor 64 a, and controls the on / off of the cutoff FET 62 a of the switch 62 based on the presence or absence of a detection signal from a timer circuit 68.

[0034] A-2-1. Reverse Connection Protection Configuration: In the arbitration circuit 60, a reverse connection protection diode 69 is electrically connected between the input terminal P1 and the timer circuit 68. The reverse connection protection diode 69 serves to protect internal circuits such as the detection circuit 66 in the event that an external device (such as the ECU 80) is electrically reverse-connected to the TURN power line Lt. Meanwhile, a reverse connection protection FET 92 is electrically connected between the input terminal P2 and the switch 62. The gate of the reverse connection protection FET 92 is connected to ground via a resistor 94. A capacitor 96 and a Zener diode 98 are connected in parallel between the gate and source of the reverse connection protection FET 92. In a normal connection state in which the positive terminal of a power supply (not shown) is electrically connected to the input terminal P1 and the input terminal P3 is electrically connected to the negative terminal of the power supply, the reverse connection protection FET 92 is turned on, and current flows normally through the drain-source path of the reverse connection protection FET 92. On the other hand, in a reverse connection state in which the positive terminal of the power supply is electrically connected to the input terminal P3 and the negative terminal of the power supply is electrically connected to the input terminal P1, the body diode of the reverse connection protection FET 92 blocks the drain-source path of the reverse connection protection FET 92, and the reverse connection protection FET 92 does not turn on but remains in the off state. However, the voltage drop due to the on resistance of the reverse connection protection FET 92 is extremely small compared to the voltage drop of the reverse connection protection diode 69.

[0035] If a reverse connection protection diode were connected instead of the reverse connection protection FET 92, a voltage drop corresponding to the combined resistance of the voltage drop of the reverse connection protection diode and the voltage drop of the diode 52 would lower the voltage supplied to the daytime running lamps 30 (second light-emitting element 32), potentially preventing the supply of a voltage sufficient to light the daytime running lamps 30. In contrast, in this embodiment, the voltage drop due to the on-resistance of the reverse connection protection FET 92 is relatively small, making it possible to achieve reverse connection protection while preventing the daytime running lamps 30 from failing to light due to a voltage drop caused by the diode.

[0036] A-2-2. Configuration for Negative Surge Protection: In the arbitration circuit 60, a negative surge protection diode 110 is further electrically connected between the input terminal P2 and the switch 62. Specifically, the negative surge protection diode 110 is connected between the DRL power supply line Ld and the constant voltage circuit 70. The anode of the negative surge protection diode 110 is electrically connected to the DRL power supply line Ld, and the cathode of the negative surge protection diode 110 is electrically connected to the constant voltage circuit 70.

[0037] In a configuration in which the reverse connection protection FET 92 is electrically connected to the DRL power supply line Ld, a negative surge may pass through the reverse connection protection FET 92 and be input to downstream circuits (such as the constant voltage circuit 70), potentially damaging the semiconductor elements (such as transistors) that make up these circuits. In contrast, in this embodiment, even if a negative surge passes through the reverse connection protection FET, the downstream circuits (the detection circuit 66, the shutoff circuit, and the constant voltage circuit 70) can be protected by the negative surge protection diode 110.

[0038] A-2-3. Configuration for Positive Surge Protection: In the arbitration circuit 60, a positive surge protection Zener diode 100 is further electrically connected between the input terminal P2 and the switch 62. The cathode of the positive surge protection Zener diode 100 is electrically connected to the DRL power supply line Ld, and the anode of the positive surge protection Zener diode 100 is electrically connected to ground.

[0039] Here, when a positive surge occurs in the DRL power supply line Ld, it is necessary to protect the switch 62 and detection circuit 66 electrically connected to the DRL power supply line Ld. If a positive surge protection capacitor were connected instead of the positive surge protection Zener diode 100, an inrush current would flow through the DRL power supply line Ld, which could have adverse effects such as damage to circuit electronic components (such as the switch 62) or failure of vehicle systems (such as the ECU 80 and body control module). In contrast, according to this embodiment, the positive surge protection Zener diode 100 is connected upstream of the switch 62, etc., so the inrush current flowing through the DRL power supply line Ld can be reduced.

[0040] A-3. Advantages of this embodiment: As described above, in the lighting circuit 40 of the vehicle lamp 10 according to this embodiment, the interrupter circuit (switch 62) for disabling the lighting drive for the daytime running lamps 30 is provided in the power supply line between the ECU 80 and the lighting drive circuit 50, rather than in the output line between the lighting drive circuit 50 and the light source unit 21 (daytime running lamps 30). Therefore, according to this embodiment, compared to a configuration in which the interrupter circuit is provided in the output line, it is possible to selectively drive the turn signal lamps 20 and the daytime running lamps 30 to light using a simple configuration that is less affected by the circuit configuration between the daytime running lamps 30 and the lighting drive circuit 50.

[0041] B. Modifications: The technology disclosed in this specification is not limited to the above-described embodiment, and can be modified in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0042] The configuration of the vehicular lamp 10 in the above embodiment is merely an example, and various modifications are possible. For example, in the above embodiment, the vehicular lamp 10 is used as an example of a lighting device, but the lighting device may be a device disposed on a moving body other than a vehicle or a fixed device. Furthermore, in the above embodiment, the first light source and the second light source are used as an example of a turn signal lamp 20 and a daytime running lamp 30, but the first light source and the second light source are not limited to these, and other types of light sources, such as headlights, clearance lamps, tail lamps, and stop lamps, may also be used. Furthermore, the light source is not limited to an LED, and may be configured to include other light-emitting elements, such as a halogen lamp.

[0043] In the above embodiment, the lighting drive circuit 50 and the arbitration circuit 60 are configured to be formed on different substrates, but they may be configured to be formed on a common substrate. In the above embodiment, a reverse connection protection diode may be connected instead of the reverse connection protection FET 92. Furthermore, in the above embodiment, at least one of the positive surge protection Zener diode 100 and the negative surge protection diode 110 may not be provided.

[0044] This international application claims priority based on Japanese Patent Application No. 2023-171055, filed on October 2, 2023, the entire contents of which are incorporated herein by reference.

[0045] The above descriptions of specific embodiments of the present invention have been presented for purposes of illustration. They are not intended to be exhaustive or to limit the invention to the precise forms described. Numerous modifications and variations will be apparent to those skilled in the art in light of the above description.

[0046] 10: Vehicle lamp 20: Turn signal lamp 21: Light source unit 22: First light-emitting element 24: Common light-emitting surface 24A, 24B: Light-emitting surfaces 30: Daytime running lamp 32: Second light-emitting element 40: Lighting circuit 50: Lighting drive circuit 54: Positive surge protection capacitor 58: Positive surge protection capacitor 60: Arbitration circuit 62: Switch 62a: Interrupter FET 62a: Interrupter FET (field-effect transistor) 62c: Capacitor 62d: Zener diode 64: On / off control circuit 64a: Transistor 66: Detection circuit 68: Timer circuit 69: Reverse connection protection diode 70: Constant voltage circuit 80: ECU 92: Reverse connection protection FET 100: Positive surge protection Zener diode 110: Negative surge protection diode Ld: DRL power line Lg: GND line Lt: TURN power line

Claims

1. A lighting circuit that supplies a drive current to a first light source and a second light source, comprising: a lighting drive circuit connected to a first power supply line and performing a first lighting drive that supplies a drive current to the first light source in accordance with a voltage level of the first power supply line; and a second lighting drive connected to a second power supply line and performing a second lighting drive that supplies a drive current to the second light source in accordance with a voltage level of the second power supply line; a detection circuit that detects lighting of the first light source based on the voltage of the first power supply line; and a shutoff circuit that has a switch connected to the second power supply line and opens the switch to shut off the second power supply line when the detection circuit detects lighting of the first light source.

2. A lighting circuit as claimed in claim 1, wherein the lighting drive circuit has a reverse connection protection diode electrically connected to the second power supply line, and a reverse connection protection FET is electrically connected to the second power supply line in a stage upstream of the detection circuit and the cutoff circuit.

3. A lighting circuit as claimed in claim 2, wherein a negative surge protection diode is electrically connected to the second power supply line in a stage upstream of the detection circuit and the cutoff circuit.

4. A lighting circuit as claimed in claim 1, wherein the lighting drive circuit has a positive surge protection capacitor electrically connected to the second power supply line, and a positive surge protection Zener diode is electrically connected to the second power supply line in a stage upstream of the detection circuit and the cutoff circuit.

5. A lighting device comprising: the first light source; the second light source; and the lighting circuit according to any one of claims 1 to 4.

6. A lighting device as claimed in claim 5, wherein the lighting device is mounted on a vehicle, the light emitting surface of the first light source and the light emitting surface of the second light source are arranged in close proximity to each other or are shared, the first light source is a light source for a turn signal lamp, and the second light source is a light source for a daytime running lamp.

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