Lighting circuits and vehicle lighting fixtures

Abstract

This invention provides a lighting circuit that suppresses variations in the drive current when illuminating a light source by changing the drive current. [Solution] The lighting circuit comprises a first drive circuit, a second drive circuit, and first and second power lines that supply power to the first and second drive circuits, wherein the first drive circuit supplies a first drive current of a first value to the light source in a first mode in which a power supply voltage is applied to the first power line, and supplies a first drive current smaller than the first value to the light source in a second mode in which the power supply voltage is applied to the second power line, and the second drive circuit supplies a second drive current of a second value to the light source in the first mode, and stops supplying the second drive current in the second mode.

Description

Technical Field

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

Background Art

[0002] There is a vehicle having a lamp that lights a predetermined light source as, for example, a stop lamp or a tail lamp darker than the stop lamp (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, the current value of the drive current when lighting the light source as a stop lamp is about 8 times the current value of the drive current when lighting the light source as a tail lamp. In this case, when controlling the current value using the functions provided in a general drive circuit, variations may occur in the drive current when lighting the light source as a tail lamp.

[0005] An object of the present invention is to provide a lighting circuit that suppresses variations in the drive current when lighting a light source by changing the drive current.

Means for Solving the Problems

[0006] The first main aspect of the present invention that achieves the above objective is a lighting circuit comprising a first drive circuit, a second drive circuit, and first and second power lines that supply power to the first and second drive circuits, wherein the first drive circuit supplies a first drive current of a first value to a light source in a first mode in which a power supply voltage is applied to the first power line, and supplies a first drive current smaller than the first value to the light source in a second mode in which the power supply voltage is applied to the second power line, and the second drive circuit supplies a second drive current of a second value to the light source in the first mode, and stops supplying the second drive current in the second mode.

[0007] A second main aspect of the present invention that achieves the above objective is a vehicle lighting device comprising a light source and a lighting circuit, wherein the lighting circuit includes a first drive circuit, a second drive circuit, a first power line supplying power to the first drive circuit, and a second power line supplying power to the second drive circuit, wherein the first drive circuit supplies a first drive current of a first value to the light source in a first mode in which a power supply voltage is applied to the first power line, and supplies a first drive current smaller than the first value to the light source in a second mode in which the power supply voltage is applied to the second power line, and the second drive circuit supplies a second drive current of a second value to the light source in the first mode, and stops supplying the second drive current in the second mode. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a lighting circuit that suppresses variations in the drive current when lighting a light source by changing the drive current. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of the configuration of a vehicle lighting fixture 1a. [Figure 2] This figure shows an example of the configuration of the first drive circuit 106. [Figure 3] This figure shows an example of the configuration of the second drive circuit 109 and the third drive circuit 112. [Figure 4] This figure shows an example of the configuration of the first control circuit 116. [Figure 5] This figure shows an example of the configuration of the second control circuit 117. [Figure 6] This figure shows an example of the operation of the lighting circuit 10a. [Figure 7] This figure shows an example of the configuration of vehicle lighting fixture 1b. [Figure 8] This figure shows an example of the configuration of the first drive circuit 600. [Figure 9] This figure shows an example of the configuration of the first control circuit 601. [Figure 10] This diagram shows an example of the operation of the lighting circuit 10b. [Figure 11] This is a diagram showing an example of the configuration of vehicle lighting fixture 1c. [Figure 12] This figure shows an example of the configuration of the first drive circuit 800. [Figure 13] This figure shows an example of the operation of the lighting circuit 10c. [Modes for carrying out the invention]

[0010] The following matters become clear from this specification and the accompanying drawings:

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The same or equivalent components, members, etc., shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted as appropriate.

[0012] Furthermore, in this embodiment, "connection" refers to a state in which two components are electrically connected unless otherwise specified. Therefore, "connection" includes not only cases where two components are connected not only by wiring, but also, for example, by a resistor.

[0013] =====This Embodiment (First Embodiment)===== <<Configuration of vehicle lighting fixture 1a>> FIG. 1 is a diagram showing an example of the configuration of the vehicle lamp 1a of the present embodiment. The vehicle lamp 1a includes switches SW1 and SW2, a lighting circuit 10a, and a light source 20.

[0014] The light source 20 is lit by being supplied with a drive current Iout obtained by adding drive currents Iout1, Iout2, and Iout3 from the lighting circuit 10a. In the present embodiment, the light source 20 is provided at the rear end of the vehicle body and lights up as a stop lamp or a tail lamp darker than the stop lamp.

[0015] The light source 20 includes a plurality (for example, three) of light emitting elements (for example, light emitting diodes (LEDs)) 30 to 32. However, the light emitting element is not limited to an LED, and may be, for example, other semiconductor light emitting elements such as a laser diode (LD) or an organic EL element.

[0016] Also, although details will be described later, when the light source 20 lights up as a stop lamp, the lighting circuit 10a supplies a drive current Iout having a predetermined current value I0 to the light source 20. On the other hand, when the light source 20 lights up as a tail lamp, the lighting circuit 10a supplies a drive current Iout having a predetermined current value I1 (for example, a current value 1 / 8 of the predetermined current value I0) to the light source 20. As a result, the stop lamp lights up brighter than the tail lamp.

[0017] <<Lighting Circuit 10a>> The lighting circuit 10a is applied to the vehicle lighting fixture 1a and is a circuit that controls the lighting and extinguishing of the light source 20 of the vehicle lighting fixture 1a. A power supply voltage Vbat (hereinafter also simply referred to as voltage Vbat) of, for example, 24V from the vehicle battery is applied to the power supply line L1 of the lighting circuit 10a via switch SW1. A voltage Vbat is also applied to the power supply line L2 of the lighting circuit 10a from the vehicle battery via switch SW2. Power supply lines L1 and L2 each supply power to the first drive circuit 106, the second drive circuit 109, and the third drive circuit 112, respectively. The voltage of power supply line L1 is denoted as voltage VL1, and the voltage of power supply line L2 is denoted as voltage VL2. Power supply line L1 corresponds to the "first power supply line," and power supply line L2 corresponds to the "second power supply line."

[0018] Furthermore, although the voltages VL1 and VL2 are denoted differently for convenience, the on-resistance of switches SW1 and SW2 is sufficiently small, so when switches SW1 and SW2 are turned on, the voltage levels of VL1 and VL2 are the same as the voltage level of Vbat.

[0019] The lighting circuit 10a then supplies a drive current Iout based on the on / off state of switches SW1 and SW2, and turns the light source 20 on or off as a stop lamp or tail lamp. <<Configuration of lighting circuit 10a>> The lighting circuit 10a includes capacitors 100, 104, 107, 110, 113, diodes 101, 102, 105, a first drive circuit 106, resistors 108, 111, 114, 115, a second drive circuit 109, a third drive circuit 112, a first control circuit 116, and a second control circuit 117.

[0020] Capacitor 100 is an element that stabilizes the voltage VL1 of the power line L1 and is installed between the power line L1 and ground. Diode 101 is an element that prevents voltage from being generated in the power line L1 when switch SW1 is off, and its anode is connected to the power line L1. Diode 102 is an element that prevents voltage from being applied to the power line L1 from the first control circuit 116, and its anode is connected to the power line L1 and its cathode is connected to the first control circuit 116. The voltage on the cathode side of diode 102 is denoted as voltage V2.

[0021] When switch SW1 or SW2 is turned on, a voltage Vbat is applied to the power line L3 to which the cathode of diode 101 is connected. Zener diode 103 is a component that clamps the voltage of power line L3, with its cathode connected to power line L3 and its anode connected to ground.

[0022] Capacitor 104 is an element that stabilizes the voltage VL2 of the power line L2 and is installed between the power line L2 and ground. Diode 105 is an element that prevents voltage from being generated in the power line L2 when the switch SW2 is off, with its anode connected to the power line L2 and its cathode connected to the power line L3.

[0023] <<<First drive circuit 106>>> The first drive circuit 106 supplies a drive current Iout1 to the light source 20, causing the light source 20 to light up or turn off as a stop lamp or tail lamp. Specifically, when a voltage Vbat is applied to the power line L1, a drive current Iout1 with a predetermined current value Ia is supplied to the light source 20 based on the voltage VL1. As will be described in detail later, in this case, drive currents Iout2 and Iout3 from the second drive circuit 109 and the third drive circuit 112 are also supplied to the light source 20, and as a result, the light source 20 lights up as a stop lamp. The case in which the light source 20 lights up as a stop lamp is called the "stop lighting mode," and the stop lighting mode corresponds to the "first mode." Also, the drive current Iout1 corresponds to the "first drive current," and the predetermined current value Ia corresponds to the "first value."

[0024] On the other hand, when a voltage Vbat is applied to the power line L2, the first drive circuit 106 supplies a drive current Iout1 to the light source 20 with a predetermined current value Ib that is smaller than a predetermined current value Ia, based on the voltage VL2. As will be described in detail later, in this case, the supply of drive currents Iout2 and Iout3 from the second drive circuit 109 and the third drive circuit 112 is stopped, and as a result, the light source 20 lights up as a tail lamp. The case in which the light source 20 lights up as a tail lamp is called the "tail lamp lighting mode," and the tail lamp lighting mode corresponds to the "second mode."

[0025] Furthermore, when both voltage VL1 and voltage VL2 are applied, the first drive circuit 106 supplies a drive current Iout1 of a predetermined current value Ia to the light source 20. As will be described in detail later, in this case, drive currents Iout2 and Iout3 from the second drive circuit 109 and the third drive circuit 112 are also supplied to the light source 20, and as a result, the light source 20 lights up as a stop lamp.

[0026] Furthermore, as shown in Figure 2, the first drive circuit 106 includes a variable resistor circuit 200, an integrated circuit 201, a capacitor 202, and a resistor 203.

[0027] The variable resistor circuit 200 is a circuit for changing the current value of the drive current Iout1 supplied by the integrated circuit 201, which will be described later. The variable resistor circuit 200 includes resistors 210, 212, 213, a PMOS transistor 211, a Zener diode 214, and a capacitor 215.

[0028] The resistor 210 is placed between terminal VINF of the integrated circuit 201 and the power line L3, and supplies a current to terminal VINF corresponding to the voltage difference between terminal VIN and terminal VINF of the integrated circuit 201.

[0029] When the PMOS transistor 211 is turned on, it connects resistors 210 and 212 in parallel, reducing the resistance of the variable resistor circuit 200. Specifically, when the voltage Vcntl from the first control circuit 116 (described later) is at ground level, the PMOS transistor 211 turns on, and the resistance of the variable resistor circuit 200 becomes the resistance of resistors 210 and 212 connected in parallel. On the other hand, when the voltage Vcntl is not at ground level, the PMOS transistor 211 turns off, and the resistance of the variable resistor circuit 200 becomes the resistance of resistor 210, increasing.

[0030] Resistor 213 is a component that pulls up the gate electrode of PMOS transistor 211 and turns off PMOS transistor 211 when the voltage Vcntl is not at ground level. Zener diode 214 is a component that clamps the gate-source voltage of PMOS transistor 211 and protects PMOS transistor 211 when the voltage Vcntl is at ground level. Capacitor 215 is a component that stabilizes the voltage clamped by Zener diode 214 when the voltage Vcntl is at ground level.

[0031] The integrated circuit 201 is a circuit for supplying a drive current Iout1 to the light source 20. Specifically, the integrated circuit 201 supplies a drive current Iout1 corresponding to the current supplied to terminal VINF to the light source 20 from terminal IOUT. Furthermore, as shown in Figure 2, when a voltage corresponding to voltage VL3 is applied to terminal CRT via resistor 203, the integrated circuit 201 constantly flows a current corresponding to the current supplied to terminal VINF as the drive current Iout1. Since a predetermined voltage difference is generated between terminals VINF and VIN, the current supplied to terminal VINF increases or decreases according to the resistance value of the variable resistor circuit 200. In other words, the integrated circuit 201 outputs a drive current Iout1 corresponding to the resistance value of the variable resistor circuit 200. The integrated circuit 201 corresponds to the "first output circuit".

[0032] Furthermore, capacitor 202 is an element that stabilizes the voltage output from terminal VIN. Also, voltage VL3 is applied to terminal PBUS via resistor 115 in Figure 1. When integrated circuit 201 detects that an abnormality has occurred in the light source 20 (for example, a break in the wire or a short circuit), integrated circuit 201 outputs a ground-level signal from terminal PBUS to notify the outside that an abnormality has occurred in the light source 20. In this case, when the voltage level of terminal PBUS becomes the ground level, integrated circuit 201 stops supplying the drive current Iout1. Note that terminal DISC is not used in this embodiment, so its description is omitted.

[0033] The capacitor 107 in Figure 1 is an element that stabilizes the voltage Vo1 output by the first drive circuit 106, and is provided between terminal IOUT and ground. The resistor 108 is an element that limits the drive current Iout1, and is provided between terminal IOUT and the light source 20. The first drive circuit 106 is a step-down drive circuit that outputs a voltage Vo1 lower than the voltage VL3.

[0034] <<<Second drive circuit 109>>> The second drive circuit 109 supplies a drive current Iout2 to the light source 20, causing the light source 20 to light up or turn off as a stop lamp. Specifically, when a voltage Vbat is applied to the power line L1, i.e., in stop lighting mode, a drive current Iout2 of a predetermined current value Ic is supplied to the light source 20 based on the voltage VL1. As will be described in detail later, in this case, drive currents Iout1 and Iout2 from the first drive circuit 106 and the third drive circuit 112 are also constantly supplied to the light source 20, and as a result, the light source 20 lights up as a stop lamp. Note that the drive currents Iout2 and Iout3 correspond to the "second drive current," and the predetermined current value Ic corresponds to the "second value."

[0035] On the other hand, when a voltage Vbat is applied to the power line L2, i.e., in taillight mode, the second drive circuit 109 stops supplying the drive current Iout1. As will be described in detail later, in this case, only the drive current Iout1 from the first drive circuit 106 is always supplied to the light source 20, and as a result, the light source 20 lights up as a taillight.

[0036] Furthermore, when both voltages VL1 and VL2 are applied, the second drive circuit 109 supplies a drive current Iout2 of a predetermined current value Ic to the light source 20. As will be described in detail later, in this case, drive currents Iout1 and Iout3 from the first drive circuit 106 and the third drive circuit 112 are also supplied to the light source 20, and as a result, the light source 20 lights up as a stop lamp.

[0037] Furthermore, as shown in Figure 3, the second drive circuit 109 includes resistors 300, 301, an integrated circuit 302, a capacitor 303, and a resistor 304.

[0038] Resistors 300 and 301 are provided between terminal VINF of the integrated circuit 302 and the power line L3, and supply current to terminal VINF according to the voltage difference between terminal VIN and terminal VINF of the integrated circuit 302. Resistors 300 and 301 correspond to "predetermined resistances".

[0039] The integrated circuit 302 supplies a drive current Iout2 corresponding to the current supplied to terminal VINF to the light source 20 via terminal IOUT. Specifically, as shown in Figure 3, when a voltage corresponding to voltage VL3 is applied to terminal CRT via resistor 304, the integrated circuit 302 constantly supplies a current corresponding to the current supplied to terminal VINF as the drive current Iout2. On the other hand, when a ground-level voltage Vshut is applied to terminal CRT, the integrated circuit 302 stops supplying the drive current Iout2. The integrated circuit 302 corresponds to the "second output circuit," and the drive currents Iout2 and Iout3 correspond to the "second drive current."

[0040] Furthermore, capacitor 303 is an element that stabilizes the voltage output from terminal VIN. Also, voltage VL3 is applied to terminal PBUS via resistor 115 in Figure 1. When integrated circuit 302 detects that an abnormality has occurred in the light source 20, integrated circuit 302 outputs a ground-level signal from terminal PBUS to notify the outside that an abnormality has occurred in the light source 20. In this case, when the voltage level of terminal PBUS becomes the ground level, integrated circuit 302 stops supplying the drive current Iout2. Note that terminal DISC is not used in this embodiment, so its description is omitted. Similarly, the third drive circuit 112 is the same as the second drive circuit 109, so its description is omitted.

[0041] Capacitor 110 in Figure 1 is an element that stabilizes the voltage Vo2 output by the second drive circuit 109 and is provided between terminal IOUT and ground. Resistor 111 is an element that limits the drive current Iout2 and is provided between terminal IOUT and light source 20. Similarly, capacitor 113 is an element that stabilizes the voltage Vo3 output by the third drive circuit 112 and is provided between terminal IOUT and ground. Resistor 114 is an element that limits the drive current Iout3 and is provided between terminal IOUT and light source 20. Furthermore, the second drive circuit 109 and the third drive circuit 112 are step-down drive circuits that output voltages Vo2 and Vo3 lower than voltage VL3.

[0042] <<<First control circuit 116>>> The first control circuit 116 controls the first drive circuit 106, specifically the variable resistor circuit 200 shown in Figure 2. Specifically, in stop-light mode, the first control circuit 116 outputs a ground-level voltage Vcntl. On the other hand, in tail-light mode, the first control circuit 116 sets its output to a high-impedance state (hereinafter referred to as "Hi-Z").

[0043] Thus, in the stop-light mode, the first control circuit 116 controls the variable resistor circuit 200 so that the light source 20 lights up as a stop lamp. On the other hand, in the tail-light mode, when no voltage VL1 is applied to the power line L1, the first control circuit 116 controls the variable resistor circuit 200 so that the light source 20 lights up as a tail lamp. In other words, in the stop-light mode, the first control circuit 116 controls the variable resistor circuit 200 so that the drive current Iout1 becomes a predetermined current value Ia, and in the tail-light mode, so that the drive current Iout1 becomes smaller than the predetermined current value Ia (for example, to a predetermined current value Ib).

[0044] As shown in Figure 4, the first control circuit 116 includes resistors 400 and 403, a Zener diode 401, a capacitor 402, and an NPN transistor 404.

[0045] Resistor 400 is a component that limits the current from diode 102 in Figure 1, and is placed between the cathode of diode 102 and the cathode of Zener diode 401. Zener diode 401 is a component that prevents the NPN transistor 404 (described later) from turning on when the voltage VL1 is below a predetermined level, and its anode is connected to the base of NPN transistor 404.

[0046] Capacitor 402 is an element that stabilizes the base-emitter voltage of NPN transistor 404 and is provided between the base of NPN transistor 404 and ground. Resistor 403 is an element that pulls down the base of NPN transistor 404 and is provided between the base of NPN transistor 404 and ground.

[0047] The NPN transistor 404 turns on when switch SW1 in Figure 1 is turned on and a voltage Vbat is applied to the power line L1, setting its collector voltage (i.e., voltage Vcntl) to ground level. On the other hand, when switch SW1 is turned off and no voltage Vbat is applied to the power line L1, the NPN transistor 404 sets its collector to Hi-Z. The voltage applied to the base of the NPN transistor 404 is denoted as voltage V1.

[0048] <<<Second control circuit 117>>> The second control circuit 117 controls the second drive circuit 109 and the third drive circuit 112 in Figure 1. Specifically, when switch SW2 is turned on and a voltage Vbat is applied to the power line L2, i.e., in tail-light mode, the second control circuit 117 outputs a voltage Vshut at ground level. On the other hand, when switch SW1 is turned on and a voltage Vbat is applied to the power line L1, i.e., in stop-light mode, the second control circuit 117 sets its output to Hi-Z regardless of whether switch SW2 is turned on or not. In this way, the second control circuit 117 controls its output so that the operation of the light source 20 lighting up as a stop lamp is prioritized when a voltage Vbat is applied to the power line L1.

[0049] As shown in Figure 5, the second control circuit 117 includes a diode 500, resistors 501 and 502, a Zener diode 503, a capacitor 504, an NMOS transistor 505, and an NPN transistor 506.

[0050] Diode 500 is an element that prevents voltage from being applied to the power line L2 from the second control circuit 117. Its anode is connected to the power line L2, and its cathode is connected to resistor 501. Resistors 501 and 502 are elements that divide the voltage from diode 500. Resistor 502 is placed between resistor 501 and ground, and the voltage at the connection point of resistors 501 and 502 is applied to the gate of NMOS transistor 505.

[0051] The Zener diode 503 is a component that clamps the voltage at the connection point of resistors 501 and 502, and is provided between the connection point of resistors 501 and 502 and ground. The capacitor 504 is a component that stabilizes the gate voltage of the NMOS transistor 505, and is provided between the gate of the NMOS transistor 505 and ground. The NPN transistor 506 has its collector connected to the gate of the NMOS transistor 505, its emitter is grounded, and a voltage V1 is applied to its base.

[0052] When switch SW2 is turned on and voltage Vbat is applied to power line L2, NMOS transistor 505 turns on and sets its drain voltage (i.e., Vshut) to ground level. On the other hand, when switch SW2 is turned off and voltage VL2 is not applied to power line L2, NMOS transistor 505 turns off. Alternatively, when switch SW1 is turned on and voltage Vbat is applied to power line L1, NPN transistor 506 turns on, and NMOS transistor 505 turns off.

[0053] <<Operation of lighting circuit 10a>> Figure 6 shows an example of the operation of the lighting circuit 10a. Note that before time t0, switches SW1 and SW2 are off, and the light source 20 is off.

[0054] At time t0, when switch SW1 is turned on and voltage Vbat is applied to power line L1, the first control circuit 116 outputs a ground-level voltage Vcntl, turning on the PMOS transistor 211 of the variable resistor circuit 200 and lowering the resistance value of the variable resistor circuit 200. As the resistance value of the variable resistor circuit 200 decreases, the current supplied to terminal VINF of the integrated circuit 201 increases. Then, the first drive circuit 106 supplies a drive current Iout1 with a predetermined current value Ia to the light source 20. Also, because voltage Vbat is applied to power line L1, the second control circuit 117 sets its output to Hi-Z. Therefore, the second drive circuit 109 and the third drive circuit 112 output drive currents Iout2 and Iout3 with predetermined current values ​​Ic to the light source 20. As a result, the light source 20 lights up as a stop lamp.

[0055] At time t1, when switch SW1 is turned off, switch SW2 is turned on, and a voltage Vbat is applied to power line L2, the first control circuit 116 sets its output to Hi-Z. In this case, resistor 213 of the variable resistor circuit 200 pulls up the gate of PMOS transistor 211, causing PMOS transistor 211 to turn off and increasing the resistance value of the variable resistor circuit 200. As the resistance value of the variable resistor circuit 200 increases, the current supplied to terminal VINF of integrated circuit 201 decreases. The first drive circuit 106 then supplies a drive current Iout1 of a predetermined current value Ib to the light source 20. Also, since a voltage Vbat is not applied to power line L1 and a voltage Vbat is applied to power line L2, the second control circuit 117 outputs a ground-level voltage Vshut. Therefore, the second drive circuit 109 and the third drive circuit 112 stop supplying drive currents Iout2 and Iout3. As a result, the light source 20 lights up as a tail lamp.

[0056] At time t2, when switches SW1 and SW2 are turned on and voltage Vbat is applied to power lines L1 and L2, the first control circuit 116 outputs a ground-level voltage Vcntl, turning on the PMOS transistor 211 of the variable resistor circuit 200 and lowering the resistance value of the variable resistor circuit 200. As the resistance value of the variable resistor circuit 200 decreases, the current supplied to terminal VINF of the integrated circuit 201 increases. The first drive circuit 106 then supplies a drive current Iout1 with a predetermined current value Ia to the light source 20. Also, because voltage Vbat is applied to power line L1, the second control circuit 117 sets its output to Hi-Z. Therefore, the second drive circuit 109 and the third drive circuit 112 output drive currents Iout2 and Iout3 with predetermined current values ​​Ic to the light source 20. As a result, the light source 20 lights up as a stop lamp.

[0057] As described above, when the lighting circuit 10a lights the light source 20 as a tail lamp, it causes the first drive circuit 106 to supply a drive current Iout1 with a predetermined current value Ib that is smaller than a predetermined current value Ia to the light source 20. At the same time, the lighting circuit 10a stops supplying drive currents Iout2 and Iout3 to the second drive circuit 109 and the third drive circuit 112. This makes it possible to provide a lighting circuit that suppresses variations in drive current when lighting the light source by changing the drive current.

[0058] ==Torture== <<Configuration of vehicle lighting fixture 1b (second embodiment)>> Figure 7 shows an example of the configuration of the vehicle lighting fixture 1b of the second embodiment. The vehicle lighting fixture 1b includes switches SW1 and SW2, a lighting circuit 10b, and a light source 20. Note that the switches SW1 and SW2 and the light source 20 are the same as in the case of vehicle lighting fixture 1a, so their explanation is omitted.

[0059] <<Lighting circuit 10b>> The lighting circuit 10b is applied to the vehicle light fixture 1b and is a circuit that controls the lighting and extinguishing of the light source 20 of the vehicle light fixture 1b. A power supply voltage Vbat (hereinafter also simply referred to as voltage Vbat) of, for example, 24V from the vehicle battery is applied to the power line L1 of the lighting circuit 10b via switch SW1. A voltage Vbat is also applied to the power line L2 of the lighting circuit 10b from the vehicle battery via switch SW2. The lighting circuit 10b then supplies a drive current Iout based on the on / off status of switches SW1 and SW2, and lights up or extinguishes the light source 20 as a stop lamp or tail lamp.

[0060] <<Configuration of lighting circuit 10b>> The lighting circuit 10b includes capacitors 100, 104, 107, 110, 113, diodes 101, 102, 105, a first drive circuit 600, resistors 108, 111, 114, 115, a second drive circuit 109, a third drive circuit 112, a first control circuit 601, and a second control circuit 117. Note that, except for the first drive circuit 600 and the first control circuit 601, the components are the same as those in the lighting circuit 10a, and therefore their explanation is omitted.

[0061] <<<First drive circuit 600>>> The first drive circuit 600 supplies a drive current Iout1 to the light source 20, causing the light source 20 to light up or turn off as a stop lamp or tail lamp. Specifically, when a voltage Vbat is applied to the power line L1, a drive current Iout1 with a predetermined current value Ia is supplied to the light source 20 based on the voltage VL1. As will be described in detail later, in this case, drive currents Iout1 and Iout2 from the second drive circuit 109 and the third drive circuit 112 are also supplied to the light source 20, and as a result, the light source 20 lights up as a stop lamp.

[0062] On the other hand, when a voltage Vbat is applied to the power line L2, the first drive circuit 600 supplies a drive current Iout1 to the light source 20 that is smaller (averaged) than a predetermined current value Ia, based on the voltage VL2. As will be described in detail later, in this case, the supply of drive currents Iout1 and Iout2 from the second drive circuit 109 and the third drive circuit 112 is stopped, and as a result, the light source 20 lights up as a tail lamp.

[0063] Furthermore, when both voltage VL1 and voltage VL2 are applied, the first drive circuit 600 supplies a drive current Iout1 of a predetermined current value Ia to the light source 20. As will be described in detail later, in this case, drive currents Iout2 and Iout3 from the second drive circuit 109 and the third drive circuit 112 are also supplied to the light source 20, and as a result, the light source 20 lights up as a stop lamp.

[0064] Furthermore, as shown in Figure 8, the first drive circuit 600 includes an integrated circuit 201, capacitors 202 and 702, resistors 210, 700 and 703, and a diode 701. Resistors 210 and 700 are connected in parallel and are provided between terminal VINF of the integrated circuit 201 and the power supply line L3. The resistance value of resistor 700 is the same as that of resistor 212 in Figure 2.

[0065] When a voltage Vbat is applied to the power line L1, diode 701 applies a predetermined voltage level to terminal CRT of integrated circuit 201 based on voltage V2. On the other hand, when no voltage Vbat is applied to the power line L1, diode 701 does not apply any voltage to terminal CRT of integrated circuit 201.

[0066] Furthermore, capacitor 702 and resistor 703 are used to generate a triangular wave as a voltage Vcrt generated at terminal CRT. Capacitor 702 is placed between terminal CRT of the integrated circuit 201 and ground, and resistor 703 is placed between terminal CRT of the integrated circuit 201 and terminal DISC. Note that capacitor 702 and resistor 703 correspond to a "setting circuit".

[0067] When no voltage is applied to terminal CRT, integrated circuit 201 supplies a predetermined current from terminal CRT to capacitor 702, increasing the voltage Vcrt. On the other hand, when the voltage Vcrt reaches a predetermined level, integrated circuit 201 outputs a ground-level voltage from terminal DISC, discharging capacitor 702 through resistor 703. Therefore, integrated circuit 201 charges capacitor 702 with a predetermined current and discharges it through resistor 703, generating a predetermined triangular wave as voltage Vcrt at terminal CRT, corresponding to the capacitance value of capacitor 702 and the resistance value of resistor 703.

[0068] Furthermore, in tail-lighting mode, the integrated circuit 201 outputs a drive current Iout1 that is smaller than a predetermined current value Ia (for example, an average predetermined current value Id) based on the duty cycle determined by the triangular wave. Therefore, the capacitor 702 and resistor 703 are elements that set the duty cycle.

[0069] <<<First control circuit 601>>> The first control circuit 601 controls the second control circuit 117. Specifically, the first control circuit 601 outputs the voltage V1 used by the second control circuit 117. As shown in Figure 9, the first control circuit 601 includes resistors 400, 403, a Zener diode 401, and a capacitor 402. Furthermore, since the first control circuit 601 is the same as the first control circuit 116 except that it does not have an NPN transistor 404, its description is omitted.

[0070] <<Operation of lighting circuit 10b>> Figure 10 shows an example of the operation of the lighting circuit 10b. Note that before time t10, switches SW1 and SW2 are off, and the light source 20 is off. The operation at times t10 and t12 is the same as the operation at times t0 and t2, so the explanation is omitted. Also, since the first drive circuit 600 does not have a configuration equivalent to the variable resistor circuit 200, the voltage Vcntl is not shown.

[0071] At time t11, switch SW1 is turned off and switch SW2 is turned on, and voltage Vbat is applied to power line L2. Since voltage V2 is not applied to terminal CRT via diode 701, integrated circuit 201 generates a voltage Vcrt which is a triangular wave determined by capacitor 702 and resistor 703. Then, during the period when voltage Vcrt decreases, integrated circuit 201 supplies a drive current Iout1 of a predetermined current value Ia to the light source 20. That is, when the drive current Iout1 is averaged, it becomes a current of a predetermined current value Id. Therefore, the first drive circuit 600 supplies a drive current Iout1 of a predetermined current value Id (when averaged) to the light source 20. Also, since voltage Vbat is not applied to power line L1 and voltage Vbat is applied to power line L2, the second control circuit 117 outputs a voltage Vshut at ground level. Therefore, the second drive circuit 109 and the third drive circuit 112 stop supplying drive currents Iout2 and Iout3. As a result, the light source 20 lights up as a taillight.

[0072] As described above, when the light source 20 is lit as a tail lamp, only the first drive circuit 600 is operated, so even if the drive current Iout1 fluctuates, the overall fluctuation is suppressed compared to when the second drive circuit 109 and the third drive circuit 112 are also operated simultaneously. This makes it possible to provide a lighting circuit that suppresses fluctuations in the drive current when lighting the light source by changing the drive current. <<Configuration of Vehicle Lighting Device 1c (Third Embodiment)>> Figure 11 shows an example of the configuration of the vehicle lighting fixture 1c of the third embodiment. The vehicle lighting fixture 1c comprises switches SW1 and SW2, a lighting circuit 10c, and a light source 20. Note that the switches SW1 and SW2 and the light source 20 are the same as in the case of vehicle lighting fixture 1a, so their explanation is omitted.

[0073] <<Lighting circuit 10c>> The lighting circuit 10c is applied to the vehicle light fixture 1c and is a circuit that controls the lighting and extinguishing of the light source 20 of the vehicle light fixture 1c. A power supply voltage Vbat (hereinafter also simply referred to as voltage Vbat) of, for example, 24V from the vehicle battery is applied to the power line L1 of the lighting circuit 10c via switch SW1. Similarly, a voltage Vbat is applied to the power line L2 of the lighting circuit 10b from the vehicle battery via switch SW2. The lighting circuit 10b then supplies a drive current Iout based on the on / off status of switches SW1 and SW2, and lights up or extinguishes the light source 20 as a stop lamp or tail lamp.

[0074] <<Configuration of lighting circuit 10c>> The lighting circuit 10c comprises capacitors 100, 104, 107, 110, 113, diodes 101, 102, 105, a first drive circuit 800, resistors 108, 111, 114, 115, a second drive circuit 109, a third drive circuit 112, a first control circuit 116, and a second control circuit 117. Note that, except for the first drive circuit 800, the components are the same as those in the lighting circuit 10a, and therefore their explanation is omitted.

[0075] <<<First drive circuit 800>>> The first drive circuit 800 supplies a drive current Iout1 to the light source 20, causing the light source 20 to light up or turn off as a stop lamp or tail lamp. Specifically, when a voltage Vbat is applied to the power line L1, a drive current Iout1 with a predetermined current value Ia is supplied to the light source 20 based on the voltage VL1. As will be described in detail later, in this case, drive currents Iout1 and Iout2 from the second drive circuit 109 and the third drive circuit 112 are also supplied to the light source 20, and as a result, the light source 20 lights up as a stop lamp.

[0076] On the other hand, when a voltage Vbat is applied to the power line L2, the first drive circuit 800 supplies a drive current Iout1 to the light source 20 that is smaller (averaged) than a predetermined current value Ia and has a predetermined current value Ie, based on the voltage VL2. As will be described in detail later, in this case, the supply of drive currents Iout1 and Iout2 from the second drive circuit 109 and the third drive circuit 112 is stopped, and as a result, the light source 20 lights up as a tail lamp.

[0077] Furthermore, when both voltage VL1 and voltage VL2 are applied, the first drive circuit 800 supplies a drive current Iout1 of a predetermined current value Ia to the light source 20. As will be described in detail later, in this case, drive currents Iout2 and Iout3 from the second drive circuit 109 and the third drive circuit 112 are also supplied to the light source 20, and as a result, the light source 20 lights up as a stop lamp.

[0078] Furthermore, as shown in Figure 12, the first drive circuit 800 includes a variable resistor circuit 200, an integrated circuit 201, capacitors 202 and 702, a resistor 703, and a diode 701. Note that the configuration of the first drive circuit 800 is a combination of the configurations of the first drive circuits 106 and 600, so a detailed explanation is omitted.

[0079] <<Operation of lighting circuit 10c>> Figure 13 shows an example of the operation of the lighting circuit 10c. Note that before time t20, switches SW1 and SW2 are off, and the light source 20 is off. Furthermore, the operation at times t20 and t22 is the same as that at times t0 and t2, so the explanation is omitted.

[0080] At time t21, switch SW1 is turned off and switch SW2 is turned on, and voltage Vbat is applied to power line L2. Since voltage V2 is not applied to terminal CRT via diode 701, integrated circuit 201 generates voltage Vcrt, which is a triangular wave determined by capacitor 702 and resistor 703. Then, during the period when voltage Vcrt decreases, integrated circuit 201 supplies a drive current Iout1 of a predetermined current value Ib to the light source 20. That is, when the drive current Iout1 is averaged, it becomes a current of a predetermined current value Ie. Therefore, the first drive circuit 800 supplies a drive current Iout1 of a predetermined current value Ie (when averaged) to the light source 20. Also, since voltage Vbat is not applied to power line L1 and voltage Vbat is applied to power line L2, the second control circuit 117 outputs a voltage Vshut at ground level. Therefore, the second drive circuit 109 and the third drive circuit 112 stop supplying drive currents Iout2 and Iout3. As a result, the light source 20 lights up as a taillight.

[0081] As described above, when the light source 20 is lit as a tail lamp, only the first drive circuit 800 is operated, so even if the drive current Iout1 fluctuates, the overall fluctuation is suppressed compared to when the second drive circuit 109 and the third drive circuit 112 are also operated simultaneously. This makes it possible to provide a lighting circuit that suppresses fluctuations in the drive current when lighting the light source by changing the drive current.

[0082] Furthermore, although the above-described embodiment described the case in which a predetermined light source is illuminated as a stop lamp or tail lamp, lighting circuits 10a to 10c can also be used to illuminate a predetermined light source as a daytime running lamp or clearance lamp.

[0083] ===Summary=== The lighting circuit 10a of this embodiment has been described above. The lighting circuit 10a comprises a first drive circuit 106, a second drive circuit 109, a third drive circuit 112, and power lines L1 and L2. In the stop lighting mode, the first drive circuit 106 supplies a drive current Iout1 with a predetermined current value Ia to the light source 20, and in the tail lighting mode, it supplies a drive current Iout1 with a predetermined current value Ib that is smaller than the predetermined current value Ia to the light source 20. In addition, the second drive circuit 109 and the third drive circuit 112 supply drive currents Iout2 and Iout3 with predetermined current values ​​Ic to the light source 20 in the stop lighting mode, and stop supplying drive currents Iout2 and Iout3 in the tail lighting mode. This makes it possible to provide a lighting circuit that suppresses variations in drive current when lighting the light source by changing the drive current.

[0084] Furthermore, the lighting circuit 10a includes a first control circuit 116 that controls the first drive circuit 106. The first drive circuit 106 includes a variable resistor circuit 200 and an integrated circuit 201. The first control circuit 116 controls the variable resistor circuit 200 so that in stop lighting mode, the drive current Iout becomes a predetermined current value Ia, and in tail lighting mode, the drive current Iout1 becomes a predetermined current value Ib, which is smaller than the predetermined current value Ia. As a result, the drive current Iout1 is always supplied to the light source 20, so the drive current can be changed to a small value without using a derating function.

[0085] Furthermore, the first drive circuit 600 includes a capacitor 702, a resistor 703, and an integrated circuit 201. This allows the derating function to be used when reducing the drive current Iout1. In addition, in tail-lighting mode, the supply of drive currents Iout2 and Iout3 is stopped, which suppresses variations in the drive current Iout.

[0086] Furthermore, the lighting circuit 10c includes a first control circuit 116 that controls the first drive circuit 800. The first drive circuit 800 includes a variable resistor circuit 200, a capacitor 702 and a resistor 703, and an integrated circuit 201. The first control circuit 116 controls the variable resistor circuit 200 so that in stop lighting mode, the drive current Iout becomes a predetermined current value Ia, and in tail lighting mode, the drive current Iout1 becomes a predetermined current value Ib, which is smaller than the predetermined current value Ia. This makes it less likely for the drive current Iout to fluctuate even if it is changed to further reduce it.

[0087] Furthermore, the second drive circuit 109 and the third drive circuit 112 include an integrated circuit 302 that outputs drive currents Iout2 and Iout3 according to the resistance values ​​of resistors 300 and 301. The integrated circuit 302 outputs drive currents Iout2 and Iout3 with a predetermined current value Ic in stop lighting mode, and stops supplying drive currents Iout2 and Iout3 in tail lighting mode. This suppresses variations in drive current when in tail lighting mode.

[0088] Furthermore, the lighting circuit 10a includes a second control circuit 117 that, when the power supply voltage Vbat is applied to the power supply lines L1 and L2, causes the first drive circuit 106 to supply a drive current Iout1 with a predetermined current value Ia, and the second drive circuit 109 and the third drive circuit 112 to supply drive currents Iout2 and Iout3 with predetermined current values ​​Ic. This enables the lighting circuit 10a to operate with priority given to the stop lighting mode.

[0089] Furthermore, the first drive circuit 106, the second drive circuit 109, and the third drive circuit 112 are step-down drive circuits that output voltages Vo1, Vo2, and Vo3 lower than the power supply voltage Vbat. This makes it possible to manufacture the lighting circuit 10a at a lower cost than using a step-up converter or a step-up / step-down converter.

[0090] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. Furthermore, the present invention may be modified or improved without departing from its spirit, and it goes without saying that equivalents thereof are included. [Explanation of symbols]

[0091] 1a,1b,1c Vehicle lights 10a, 10b, 10c lighting circuit 20 light source 30, 31, 32 Light-emitting elements 100, 104, 107, 110, 113, 202, 215, 303, 402, 504, 702 Capacitors 101, 102, 105, 500, 701 diodes 103,214,401,503 Zener diodes 106,600,800 First drive circuit 108, 111, 114, 115, 203, 210, 212, 213, 300, 301, 304, 400, 403, 501, 502, 700, 703 resistors 109 Second drive circuit 112 Third drive circuit 116,601 First control circuit 117 Second Control Circuit 200 Variable Resistor Circuit 201,302 integrated circuits 211 PMOS transistors 404,506 NPN transistors 505 NMOS transistors

Claims

1. A lighting circuit comprising a first drive circuit, a second drive circuit, and first and second power lines that supply power to the first and second drive circuits, The first drive circuit is, In the first mode, when the power supply voltage is applied to the first power supply line, a first drive current of a first value is supplied to the light source, and in the second mode, when the power supply voltage is applied to the second power supply line, a first drive current smaller than the first value is supplied to the light source. The second drive circuit is, In the first mode, a second drive current of a second value is supplied to the light source, and in the second mode, the supply of the second drive current is stopped. Lighting circuit.

2. A lighting circuit according to claim 1, The system includes a first control circuit for controlling the first drive circuit, The first drive circuit is, A variable resistor circuit and A first output circuit that outputs the first drive current corresponding to the resistance value of the variable resistor circuit, Includes, The first control circuit is, In the first mode, the variable resistor circuit is controlled such that the first drive current becomes the first value, and in the second mode, the first drive current becomes smaller than the first value. Lighting circuit.

3. A lighting circuit according to claim 1, The first drive circuit is, A setting circuit for setting the duty cycle, In the second mode, a first output circuit outputs a first drive current smaller than the first value based on the duty cycle, including, Lighting circuit.

4. A lighting circuit according to claim 1, The system includes a first control circuit for controlling the first drive circuit, The first drive circuit is, A variable resistor circuit and A setting circuit for setting the duty cycle, In the first mode, a first output circuit outputs a first drive current corresponding to the resistance value of the variable resistor circuit, and in the second mode, a first output circuit outputs a first drive current corresponding to the resistance value of the variable resistor circuit and the duty cycle, Includes, The first control circuit is, In the first mode, the variable resistor circuit is controlled such that the first drive current becomes the first value, and in the second mode, the first drive current becomes smaller than the first value. Lighting circuit.

5. A lighting circuit according to any one of claims 1 to 4, The second drive circuit is, A second output circuit that outputs the second drive current corresponding to the resistance value of a predetermined resistor, Includes, The second output circuit is, In the first mode, the second drive current of the second value is output, and in the second mode, the supply of the second drive current is stopped. Lighting circuit.

6. The lighting circuit according to claim 5, When the power supply voltage is applied to the first and second power supply lines, the second control circuit causes the first drive circuit to supply a first drive current of a first value and the second drive circuit to supply a second drive current of a second value. A lighting circuit equipped with the following features.

7. A lighting circuit according to claim 1, The first and second drive circuits are step-down drive circuits that output a voltage lower than the power supply voltage. Lighting circuit.

8. Vehicle lighting fixtures, Light source and Lighting circuit and Equipped with, The aforementioned lighting circuit is First drive circuit and The second drive circuit and A first power supply line that supplies power to the first drive circuit, A second power supply line that supplies power to the second drive circuit, Includes, The first drive circuit is, In the first mode, when the power supply voltage is applied to the first power supply line, a first drive current of a first value is supplied to the light source, and in the second mode, when the power supply voltage is applied to the second power supply line, a first drive current smaller than the first value is supplied to the light source. The second drive circuit is, In the first mode, a second drive current of a second value is supplied to the light source, and in the second mode, the supply of the second drive current is stopped. Vehicle lighting fixtures.

Images