Lighting circuit and vehicle lamp

Abstract

This lighting circuit is applied to a vehicle lamp that includes a first light source and a second light source. The lighting circuit comprises: a first drive circuit that supplies a first drive current to the first light source on the basis of a first voltage applied to a first line, and supplies a second drive current, which is greater than the first drive current, to the first light source on the basis of a second voltage applied to a second line; a second drive circuit that, on the basis of a third voltage applied to a third line on a predetermined cycle in a first period, supplies a third drive current to the second light source on the predetermined cycle; and a control circuit that controls the first drive circuit on the basis of the third voltage applied to the third line on the predetermined cycle in the first period, such that the first light source is lit alternately with the second light source at a brightness corresponding to the first drive current.

Description

Lighting circuit and vehicle lighting fixture

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

[0002] For example, there is a vehicle having a lamp that lights up a first light source for a daytime running lamp or clearance lamp and a second light source for a turn signal lamp on the same light-emitting surface (for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-049515

[0004] In such a vehicle, for example, when the second light source flashes, it is required by law to alternately flash the first light source as a clearance lamp. However, if such control is performed using a microcomputer, for example, the circuit configuration of the lighting circuit becomes complicated.

[0005] An object of the present invention is to provide a lighting circuit that can easily realize alternate flashing of turn signal lamps and clearance lamps.

[0006] A first main aspect of the present invention that achieves the above-mentioned object is a lighting circuit that is applied to a vehicle lamp including a first light source and a second light source, the lighting circuit comprising: a first drive circuit that supplies a first drive current to the first light source based on a first voltage applied to a first line, and supplies a second drive current that is larger than the first drive current to the first light source based on a second voltage applied to a second line; a second drive circuit that supplies a third drive current to the second light source at a predetermined cycle based on a third voltage applied to a third line at the predetermined cycle during a first period; and a control circuit that controls the first drive circuit so that the first light source and the second light source are alternately lit at a brightness that corresponds to the first drive current, based on the third voltage applied to the third line at the predetermined cycle during the first period.

[0007] A second main aspect of the present invention that achieves the above-mentioned object is a vehicular lamp comprising a first light source, a second light source, and a lighting circuit that lights the first and second light sources, wherein the lighting circuit includes a first driving circuit that supplies a first driving current to the first light source based on a first voltage applied to a first line and supplies a second driving current that is larger than the first driving current to the first light source based on a second voltage applied to a second line, a second driving circuit that supplies a third driving current to the second light source at a predetermined cycle based on a third voltage applied to a third line at the predetermined cycle during a first period, and a control circuit that controls the first driving circuit so that the first light source and the second light source are alternately lit at a brightness that corresponds to the first driving current, based on the third voltage applied to the third line at the predetermined cycle during the first period.

[0008] According to the present invention, it is possible to provide a lighting circuit that can easily realize alternate flashing of turn signal lamps and clearance lamps.

[0009] FIG. 1 is a diagram showing an example of the configuration of a vehicle lamp 1. FIG. 2 is a diagram showing an example of the front of a vehicle. FIG. 3 is a diagram showing an example of the configuration of a lighting circuit 30a (30b). FIG. 4 is a diagram showing an example of the configuration of a control circuit 120a. FIG. 5 is a diagram showing an example of the operation of the lighting circuit 30a. FIG. 6 is a diagram showing an example of the operation of the lighting circuit 30a. FIG. 7 is a diagram showing an example of the operation of the lighting circuit 30a. FIG. 8 is a diagram showing an example of the configuration of a control circuit 120b. FIG. 9 is a diagram showing an example of the operation of the lighting circuit 30b. FIG. 10 is a diagram showing the lighting states of a first light source 10 and a second light source 20.

[0010] <Cross-Reference to Related Applications> This application claims priority to Japanese Patent Application No. 2024-100583, filed on June 21, 2024, the contents of which are incorporated by reference.

[0011] At least the following matters will become clear from the description of this specification and the accompanying drawings.

[0012] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The same or equivalent components, members, etc. shown in the drawings will be designated by the same reference numerals, and redundant descriptions will be omitted where appropriate.

[0013] In this embodiment, "connection" refers to an electrically connected state unless otherwise specified. Therefore, "connection" includes not only a case where two components are connected via wiring, but also a case where two components are connected via, for example, a resistor.

[0014] 1 is a diagram showing an example of the configuration of a vehicle lamp 1 according to this embodiment. The vehicle lamp 1 includes a first light source 10, a second light source 20, and a lighting circuit 30a.

[0015] The first light source 10 is illuminated by receiving a drive current Iout1 from the lighting circuit 30a. In this embodiment, the first light source 10 is used as a clearance lamp (hereinafter also referred to as CLL) and a daytime running lamp (hereinafter also referred to as DRL). The clearance lamp is a lamp that indicates the width of the vehicle and its presence, and is also called a sidelight or small lamp. The daytime running lamp is a lamp that is illuminated during the day to notify pedestrians, drivers of oncoming vehicles, and the like of the presence of a moving vehicle, and is also called a daytime running lamp. As will be described later, the daytime running lamp is illuminated brighter than the clearance lamp.

[0016] The first light source 10 includes a plurality of (e.g., six) light-emitting elements (e.g., light-emitting diodes (LEDs)) 11 to 16. However, the light-emitting elements are not limited to LEDs, and may be other semiconductor light-emitting elements such as laser diodes (LDs) or organic EL elements.

[0017] Furthermore, as will be described in detail later, when the first light source 10 is turned on as a clearance lamp, the lighting circuit 30a supplies a drive current Iout1 having a predetermined current value Ic (e.g., several tens of mA) (on average) to the first light source 10. On the other hand, when the first light source 10 is turned on as a daytime running lamp, the lighting circuit 30a supplies a drive current Iout1 having a predetermined current value Id (e.g., several hundred mA) that is larger than the predetermined current value Ic to the first light source 10. As a result, the daytime running lamp is turned on brighter than the clearance lamp.

[0018] The second light source 20 is illuminated by receiving a drive current Iout2 from the lighting circuit 30a. In this embodiment, the second light source 20 is used as a turn signal lamp. A turn signal lamp is a vehicular direction indicator lamp that is illuminated when a driver of a vehicle operates a turn signal (not shown). Furthermore, if a turn signal lamp fails, it is required by law to rapidly flash a turn signal lamp other than the failed lamp (called a "high flasher") to notify those around the vehicle of the failure of the turn signal lamp.

[0019] The second light source 20 includes a plurality of (e.g., three) light-emitting elements (e.g., light-emitting diodes (LEDs)) 21 to 23. However, the light-emitting elements are not limited to LEDs, and may be, for example, other semiconductor light-emitting elements such as laser diodes (LDs) or organic EL elements.

[0020] 2 is a diagram showing an example of the front of a vehicle, and depicts lamps 1a and 1b. Lamp 1a is provided with, for example, a high beam lamp 50a and a light-emitting surface 51a on which the first light source 10 and the second light source 20 are arranged. The same applies to lamp 1b.

[0021] In this way, when the first light source 10 and the second light source 20 are arranged on the same light-emitting surface, if the clearance lamp (first light source 10) is lit when the turn signal lamp (second light source 20) flashes, the light emitted from the turn signal lamp may appear white. Since regulations require the light emitted from the turn signal lamp to be amber, it is necessary to avoid having the first light source 10 and the second light source 20 lit at the same time.

[0022] Therefore, the lighting circuit 30a of this embodiment controls the first light source 10 to be turned off when the second light source 20 is turned on, and controls the first light source 10 to be turned on as a clearance lamp when the second light source 20 is turned off. The lighting circuit 30a will be described below.

[0023] <<Lighting Circuit 30a>> The lighting circuit 30a is applied to the vehicle lamp 1 and is a circuit that controls the turning on and off of the first light source 10 and the second light source 20 of the vehicle lamp 1. A power supply voltage Vbat (hereinafter also simply referred to as voltage Vbat) from a vehicle battery 40 is applied to terminals Ta and Tb of the lighting circuit 30a via switches SWd and SWc, respectively. The voltage applied to terminal Ta via switch SWd is referred to as voltage Vd, and the voltage applied to terminal Tb via switch SWc is referred to as voltage Vc. The line to which voltage Vc is applied is referred to as line L1, and the line to which voltage Vd is applied is referred to as line L2. The line L1 corresponds to the "first line," the line L2 corresponds to the "second line," the voltage Vc corresponds to the "first voltage," and the voltage Vd corresponds to the "second voltage."

[0024] For convenience, the voltages Vd and Vc are denoted differently, but the on-resistance of the switches SWd and SWc is sufficiently small, so when the switches SWd and SWc are each on, the voltage levels of the voltages Vd and Vc are the same as the voltage level of the voltage Vbat.

[0025] The lighting circuit 30a supplies a driving current Iout1 based on the on / off of the switches SWd and SWc, and turns on or off the first light source 10 provided between the terminal Td and the ground as a daytime running lamp or a clearance lamp.

[0026] A power supply voltage Vbat (hereinafter simply referred to as voltage Vbat) is applied to a terminal Tc of the lighting circuit 30a from a vehicle battery 40 via a switch SWt. The voltage applied to the terminal Tc is referred to as voltage Vt. The line to which voltage Vt is applied is referred to as line L3.

[0027] The voltage Vt is applied so that a period (e.g., 400 ms) during which the voltage Vbat is not applied and a period (e.g., 400 ms) during which the voltage Vbat is applied are repeated at a predetermined cycle (e.g., 800 ms). The switch SWt is turned on during the period during which the voltage Vt is applied at the predetermined cycle. The line L3 corresponds to the "third line," the voltage Vt corresponds to the "third voltage," and the period during which the voltage Vt is applied at the predetermined cycle corresponds to the "first period."

[0028] For convenience, the voltage Vt is expressed differently from the voltages Vd and Vc, but because the on-resistance of the switch (not shown) is sufficiently small, the voltage level of the voltage Vt when the switch SWt is on is the same as the voltage level of the voltage Vbat.

[0029] The lighting circuit 30a supplies a driving current Iout2 based on the voltage Vt, and turns on or off the second light source 20 provided between the terminal Te and the ground.

[0030] 3 is a diagram showing an example of the configuration of the lighting circuit 30a. The lighting circuit 30a includes a first drive circuit 100, a second drive circuit 110, a control circuit 120a, and a determination circuit 130.

[0031] <<First Drive Circuit 100>> The first drive circuit 100 turns on or off the first light source 10. Specifically, when a voltage Vc is applied to the line L1, the first drive circuit 100 supplies a drive current Iout1 of a predetermined current value Ic to the first light source 10 based on the voltage Vc. As a result, the first light source 10 lights up as a clearance lamp.

[0032] On the other hand, when voltage Vd is applied to line L2, the first drive circuit 100 supplies drive current Iout1 of a predetermined current value Id to the first light source 10 based on the voltage Vd. Note that when both voltages Vc and Vd are applied, the first drive circuit 100 supplies drive current Iout1 of the predetermined current value Id to the first light source 10. As a result, the first light source 10 lights up as a daytime running lamp.

[0033] The first drive circuit 100 also includes a switch 140 and a current output circuit 141. The drive current Iout1 having the predetermined current value Ic corresponds to the "first drive current," and the drive current Iout1 having the predetermined current value Id corresponds to the "second drive current."

[0034] <<Switch 140 >> The switch 140 causes the current output circuit 141 to output a drive current Iout1 having either a predetermined current value Id or Ic to the first light source 10. The switch 140 includes an NPN transistor 150 and a capacitor 151.

[0035] The emitter of the NPN transistor 150 is grounded, and one end of the capacitor 151 and the cathode of a diode 175 (described later) are connected to the base. When the voltage Vt is not applied to the line L3 and the voltage Vd is applied to the line L2, a voltage corresponding to the voltage Vd is applied to the base via the diode 175, turning the NPN transistor 150 on, as will be described in detail later.

[0036] In this case, the control circuit 120a (described later) sets the line that outputs the signal Scntl to a high impedance state (hereinafter referred to as a "Hi-Z state"), as will be described in detail later. When the control circuit 120a sets the line that outputs the signal Scntl to a Hi-Z state, the control of the switch 140 by the control circuit 120a is stopped.

[0037] On the other hand, the NPN transistor 150 is turned off when the voltage Vd is not applied to the line L2. Also, when the voltage Vt is applied at a predetermined cycle, the control circuit 120a outputs a low-level (hereinafter referred to as "L") signal Scntl, so the NPN transistor 150 is turned off.

[0038] Capacitor 151 is an element for stabilizing the base-emitter voltage of NPN transistor 150, and is provided between the base of NPN transistor 150 and ground. Note that the state of switch 140 when NPN transistor 150 is on corresponds to the "first state," and the state of switch 140 when NPN transistor 150 is off corresponds to the "second state."

[0039] <<Current Output Circuit 141>> The current output circuit 141 outputs a drive current Iout1 of either a predetermined current value Id or Ic to the first light source 10 based on the on / off state of the NPN transistor 150. Specifically, when the NPN transistor 150 is on, the current output circuit 141 outputs the drive current Iout1 of the predetermined current value Id to the first light source 10, and when the NPN transistor 150 is off, the current output circuit 141 outputs the drive current Iout1 of the predetermined current value Ic to the first light source 10.

[0040] The current output circuit 141 includes diodes 160, 161, and 175, an input filter 162, a DC-DC converter 163, an output filter 164, an LED driver 165, an integrated circuit 166, resistors 167 to 169, 171, 172, and 174, and capacitors 170 and 173.

[0041] The anode of the diode 160 is connected to the terminal Ta, and the cathode is connected to the input filter 162. Therefore, the diode 160 prevents the voltage Vc from being applied to the terminal Ta when the voltage Vc is applied to the line L1 and the voltage Vd is not applied to the line L2.

[0042] The diode 161 has an anode connected to the terminal Tb and a cathode connected to the input filter 162. Therefore, the diode 161 prevents the voltage Vd from being applied to the terminal Tb when the voltage Vd is applied to the line L2 and the voltage Vc is not applied to the line L1.

[0043] When at least one of voltage Vd and voltage Vc is applied, input filter 162 removes noise from the applied voltage and applies the voltage to DC-DC converter 163. When voltage Vc is applied to line L1, voltage Vbat is applied to input filter 162, when voltage Vd is applied to line L2, voltage Vbat is similarly applied, and when voltages Vd and Vc are applied, voltage Vbat is similarly applied.

[0044] The DC-DC converter (DC-DC) 163 boosts or lowers the noise-removed voltage based on a signal from an LED driver 165 (described later), and outputs a current of a predetermined current value Ic or Id to the output filter 164.

[0045] An output filter 164 removes noise from the current from the DC-DC converter 163 and outputs the current to the first light source 10 as a drive current Iout1.

[0046] An LED driver (LED DRV) 165 controls the start or stop of current output from the DC-DC converter 163 based on a signal from an integrated circuit 166 (described later). When a control circuit 120a (described later) outputs an "L" level signal Soff, the LED driver 165 causes the DC-DC converter 163 to stop current output based on the divided voltage of resistors 172 and 174. A capacitor 173 is provided to stabilize the signal from the LED driver 165.

[0047] The integrated circuit (PWM IC) 166 outputs a PWM signal or a DC signal having a duty corresponding to the voltage divided by the resistors 167 and 168 to the LED driver 165. Specifically, when the NPN transistor 150 is turned off, the integrated circuit 166 charges and discharges the capacitor 170 via the resistor 169, and makes the voltage at the connection point between the resistor 169 and the capacitor 170 an oscillation voltage (for example, a triangular wave). In this case, the integrated circuit 166 outputs a PWM signal having a duty corresponding to the voltage divided by the resistors 167 and 168 to the LED driver 165 based on a comparison between the oscillation voltage and a reference voltage.

[0048] On the other hand, when the NPN transistor 150 is turned on, the integrated circuit 166 outputs a DC signal to the LED driver 165 based on the voltage divided by the resistors 169 and 171 .

[0049] The anode of the diode 175 is connected to the line L2, and the cathode is connected to the base of the NPN transistor 150. Therefore, when the voltage Vd is applied to the line L2, the diode 175 turns on the NPN transistor 150 unless the control circuit 120a outputs an "L" level signal Scntl. On the other hand, when the voltage Vd is not applied to the line L2, the diode 175 is not involved in the on / off of the NPN transistor 150.

[0050] Therefore, when the NPN transistor 150 is turned off, the current output circuit 141 controls the DC-DC converter 163 to start or stop current output based on the PWM signal from the integrated circuit 166, and outputs a drive current Iout1 of a predetermined current value Ic to the first light source 10.

[0051] On the other hand, when the NPN transistor 150 is turned on, the current output circuit 141 operates the DC-DC converter 163 based on the DC signal from the integrated circuit 166 and outputs a drive current Iout1 of a predetermined current value Id to the first light source .

[0052] <<Second Drive Circuit 110>> The second drive circuit 110 turns on or off the second light source 20. Specifically, when a voltage Vt is applied to the line L3, the second drive circuit 110 supplies a drive current Iout2 to the second light source 20 based on the voltage Vt. The second drive circuit 110 also includes a capacitor 180, a diode 181, an input filter 182, a DC-DC converter 183, an output filter 184, and an LED driver 185. The drive current Iout2 corresponds to a "third drive current."

[0053] The capacitor 180 is provided between the line L3 and the ground, and is an element for protecting the internal circuit when static electricity is applied to the terminal Tc. Note that a capacitor (not shown) may be similarly provided between each of the lines L2 and L3 and the ground.

[0054] The diode 181 has an anode connected to the line L3 and a cathode connected to the control circuit 120a and the input filter 182. The diode 181 is an element for protecting the circuit even when the terminal Tc is grounded and a voltage Vt is applied to a terminal (not shown) that should be connected to ground (i.e., reverse connection).

[0055] When the voltage Vt is applied, the input filter 182 removes noise from the applied voltage and applies the voltage to the DC-DC converter 183 .

[0056] The DC-DC converter (DC-DC) 183 increases or decreases the voltage from which noise has been removed based on a signal from an LED driver 185 (described later), and outputs a current to the second light source 20 .

[0057] An output filter 184 removes noise from the current from the DC-DC converter 183 and supplies the current to the second light source 20 as a drive current Iout2.

[0058] An LED driver (LED DRV) 185 causes a DC-DC converter 183 to output a current based on the voltage from the input filter 182 .

[0059] <<Control Circuit 120a>> The control circuit 120a controls the first drive circuit 100 based on the voltage Vt. Note that, as will be described in detail later, the control circuit 120a is configured with an analog circuit.

[0060] <<Determination Circuit 130>> The determination circuit 130 determines whether or not an abnormality has occurred that prevents the supply of drive current Iout2 to the second light source 20 (for example, a disconnection of the second light source 20). Specifically, the determination circuit 130 determines that an abnormality (for example, a disconnection) has occurred in the second light source 20 when the output voltage of the DC-DC converter 183 exceeds a predetermined voltage (for example, 45 V). The determination circuit 130 includes a comparator 190 and a latch circuit 191.

[0061] The comparator 190 outputs a high-level (hereinafter referred to as "H" level) signal Sf when the voltage corresponding to the output voltage of the DC-DC converter 183 exceeds a reference voltage corresponding to a predetermined voltage (for example, 45 V). On the other hand, the comparator 190 outputs an "L" level signal Sf when the output voltage of the DC-DC converter 183 is less than the predetermined voltage. In this embodiment, the comparator 190 exists independently, but the LED driver 185 may also include elements of the comparator 190 internally.

[0062] The latch circuit (Latch) 191 latches the signal Sf, and when the comparator 190 outputs a signal Sf at a high level, it outputs a signal Lout at a low level; otherwise, it puts the line through which the signal Lout is output into a Hi-Z state.

[0063] In this way, when the determination circuit 130 determines that an abnormality has occurred that prevents the supply of the drive current Iout2 to the second light source 20 (for example, a disconnection of the second light source 20), it outputs an "L" level signal Lout. In this case, the current output circuit 141 operates regardless of the period during which the voltage Vt is applied to the line L3, and the first drive circuit 100 operates to light the first light source 10 at a brightness corresponding to the predetermined current value Ic, i.e., as a clearance lamp, based on either the voltage Vc or Vd during the period during which the voltage Vt is applied at a predetermined cycle.

[0064] 4 is a diagram showing an example of the configuration of the control circuit 120a. The control circuit 120a controls the first drive circuit 100 based on the voltage Vt, and when an abnormality (e.g., a break) occurs in the second light source 20, causes the DC-DC converter 163 to output a current via the LED driver 165. The control circuit 120a includes a switch control circuit 200a and an output control circuit 201.

[0065] <<Switch Control Circuit 200a>> The switch control circuit 200a is a circuit that outputs a signal Scntl that controls the NPN transistor 150. Specifically, during a period in which the voltage Vt is applied to the line L3 at a predetermined cycle, the switch control circuit 200a outputs an “L” level signal Scntl to turn off the NPN transistor 150. On the other hand, when the voltage Vt is not applied or an abnormality occurs in the second light source 20, the switch control circuit 200a sets the line that outputs the signal Scntl to a Hi-Z state, and the NPN transistor 150 turns on and off depending on whether the voltage Vd is applied to the line L2.

[0066] The switch control circuit 200 a includes resistors 210 , 214 , and 215 , a Zener diode 211 , a diode 212 , capacitors 213 and 217 , and an NMOS transistor 216 .

[0067] The resistor 210 is provided between the line L 3 and the Zener diode 211 and functions as a gate resistor of the NMOS transistor 216 .

[0068] The Zener diode 211 has a cathode connected to the resistor 210 and an anode connected to the anode of the diode 212. Therefore, the Zener diode 211 prevents the NMOS transistor 216 from being turned on when the voltage level of the voltage Vt is low enough that the LED driver 165 does not operate (for example, lower than 5 V). Note that when the voltage level of the voltage Vt (i.e., the voltage level of the voltage Vbat) is higher than 6 V, it is required to ensure the lighting of the first light source 10 and the second light source 20, and furthermore, when the voltage level of the voltage Vt is higher than 9 V, it is required to ensure the performance of the lighting circuit 30a.

[0069] The diode 212 has an anode connected to the anode of the Zener diode 211 and a cathode connected to one end of the capacitor 213. Therefore, the diode 212 suppresses current from flowing from the capacitor 213 to the line L3 when the capacitor 213 is charged with the voltage Vt.

[0070] The capacitor 213 is provided between the cathode of the diode 212 and the ground. Therefore, the capacitor 213 is charged when the voltage Vt is applied to the line L3, and is an element that turns on the NMOS transistor 216 (described later) even during a period when the voltage Vt is not applied (for example, 400 ms), causing the NMOS transistor 216 to output an "L" level signal Scntl.

[0071] Resistor 214 is provided between the cathode of diode 212 and ground. Resistor 214 has a resistance value large enough to prevent capacitor 213 from discharging during a period (e.g., 400 ms) when voltage Vt, which is applied at a predetermined cycle, is not applied, and discharges capacitor 213 when voltage Vt is no longer applied at the predetermined cycle.

[0072] The resistor 215 is provided between the cathode of the diode 212 and the gate of the NMOS transistor 216 , and functions as a gate resistor of the NMOS transistor 216 .

[0073] The NMOS transistor 216 has a gate connected to the resistor 215, a source connected to ground, and a drain connected to the base of the NPN transistor 150. Therefore, the NMOS transistor 216 outputs a signal Scntl that controls the switch 140. When the voltage Vt is applied to the line L3 at a predetermined cycle, the NMOS transistor 216 turns on and outputs the signal Scntl at an "L" level. On the other hand, when the voltage Vt is not applied to the line L3 at a predetermined cycle, the NMOS transistor 216 turns off and puts the line that outputs the signal Scntl into a Hi-Z state.

[0074] The capacitor 217 is provided between the gate of the NMOS transistor 216 and the ground, and is an element that stabilizes the gate-source voltage of the NMOS transistor 216 .

[0075] <<Output Control Circuit 201>> The output control circuit 201 controls the voltage of the line between the LED driver 165 and the integrated circuit 166, and controls whether or not the current output circuit 141 outputs the drive current Iout1 to the first light source 10. Specifically, the output control circuit 201 stops the operation of the current output circuit 141 during the period in which the voltage Vt is applied to the line L3 during which the voltage Vt is applied at a predetermined cycle, and operates the current output circuit 141 during the period in which the voltage Vt is not applied to the line L3.

[0076] Therefore, the output control circuit 201 controls the first drive circuit 100 to alternately light the first light source 10 as a clearance lamp with the second light source 20, based on the voltage Vt applied to the line L3 during the period in which the voltage Vt is applied at a predetermined cycle. The output control circuit 201 includes resistors 220, 224, 227, and 228, a Zener diode 221, NPN transistors 222 and 226, a capacitor 223, and an NMOS transistor 229.

[0077] The resistor 220 is provided between the line L 3 and the cathode of the Zener diode 221 , and limits the current that flows between the base and emitter of the NPN transistor 222 via the Zener diode 221 .

[0078] The Zener diode 221 has a cathode connected to the resistor 220 and an anode connected to the base of the NPN transistor 222. Therefore, similar to the Zener diode 211, the Zener diode 221 prevents the NPN transistor 222 from being turned on when the voltage level of the voltage Vt is low enough that the LED driver 165 does not operate (for example, lower than 5 V).

[0079] The NPN transistor 222 has a base connected to the anode of the Zener diode 221 and one end of the capacitor 223, an emitter grounded, and a collector connected via the resistor 174 to the line between the LED driver 165 and the integrated circuit 166. Therefore, the NPN transistor 222 is turned on and outputs an "L" level signal Soff while the voltage Vt is applied to the line L3.

[0080] On the other hand, during the period when the voltage Vt is not applied to the line L3, the NPN transistor 222 is turned off, and the line that outputs the signal Soff is set to a Hi-Z state. That is, when the voltage Vt is applied, the NPN transistor 222 stops the operation of the current output circuit 141 and turns off the first light source 10. On the other hand, when the voltage Vt is not applied, the NPN transistor 222 operates the current output circuit 141 and outputs the drive current Iout1 to the first light source 10.

[0081] The capacitor 223 is provided between the base of the NPN transistor 222 and the ground, and stabilizes the base-emitter voltage of the NPN transistor 222 .

[0082] The resistor 224 is provided between the line to which the voltage Vcc is applied and the anode of the diode 225 and the base of the NPN transistor 226, and the diode 225 is provided between the resistor 224 and the latch circuit 191. Therefore, when the determination circuit 130 determines that there is an abnormality (for example, a break) in the second light source 20 and outputs an "L" level signal Lout, the resistor 224 and the diode 225 turn off the NPN transistor 226.

[0083] On the other hand, when the judgment circuit 130 does not determine that the second light source 20 is abnormal (for example, a broken wire) and sets the line that outputs the signal Lout to a Hi-Z state, the resistor 224 and the diode 225 apply a voltage Vcc to the base of the NPN transistor 226 via the resistor 224, turning it on.

[0084] The NPN transistor 226 has a base connected to the connection point of the resistor 224 and the diode 225, an emitter grounded, and a collector connected to the connection point of the resistors 227 and 228. Therefore, the NPN transistor 226 is turned on when the latch circuit 191 puts the line that outputs the signal Lout into a Hi-Z state, and is turned off when the latch circuit 191 outputs the signal Lout at an "L" level.

[0085] Resistor 227 is provided between a line to which voltage Vcc is applied and resistor 228, and resistor 228 is provided between resistor 227 and ground. Therefore, resistors 227 and 228 form a voltage divider circuit for turning on NMOS transistor 229 when NPN transistor 226 is off. On the other hand, when NPN transistor 226 is on, resistors 227 and 228 turn off NMOS transistor 229 because the voltage level at the connection point of resistors 227 and 228 becomes the ground level.

[0086] The NMOS transistor 229 has a gate connected to the connection point of the resistors 227 and 228, a source grounded, and a drain connected to the connection point of the resistor 220 and the Zener diode 221. Therefore, when the determination circuit 130 determines that the second light source 20 is abnormal (for example, a broken wire), the NMOS transistor 229 turns off the NPN transistor 222 and puts the line from which the signal Soff is output into a Hi-Z state. As a result, when the determination circuit 130 determines that the second light source 20 is abnormal (for example, a broken wire), the LED driver 165 operates the DC-DC converter 163 based on the state of the switch 140.

[0087] Therefore, when the determination circuit 130 determines that the second light source 20 is abnormal (for example, broken), the output control circuit 201 operates the current output circuit 141 regardless of the period during which the voltage Vt is applied to the line L3.

[0088] <<Normal Operation of the Lighting Circuit 30a>> Fig. 5 is a diagram showing an example of the operation of the lighting circuit 30a. Note that in Fig. 5, it is assumed that an abnormality that prevents the supply of the drive current Iout2 to the second light source 20 (for example, a break in the second light source 20) does not occur. Fig. 5 also shows the operation when the voltage Vd is applied.

[0089] 3 is turned on at time t0, voltage Vd is applied to line L2, and voltage Vt is not applied to line L3, so that NPN transistor 150 is turned on. When NPN transistor 150 is turned on, the divided voltage of resistors 169 and 171 is applied to integrated circuit 166, so that integrated circuit 166 outputs a DC signal to LED driver 165.

[0090] Then, the LED driver 165 causes the DC-DC converter 163 to output a current of a predetermined current value Id. Therefore, the current output circuit 141 outputs a drive current Iout1 of the predetermined current value Id to the first light source 10. The first light source 10 then lights up as a daytime running lamp. That is, when the NPN transistor 150 is turned on, the current output circuit 141 outputs to the first light source 10 the drive current Iout1 of the predetermined current value Id that lights up the first light source 10 as a daytime running lamp.

[0091] 3, the NMOS transistor 216 is turned on, and the NPN transistor 150 is turned off. When the NPN transistor 150 is turned off, the integrated circuit 166 outputs a PWM signal, and the LED driver 165 controls the start or stop of current output from the DC-DC converter 163 based on the PWM signal.

[0092] However, while the voltage Vt is being applied, the NPN transistor 222 in FIG. 4 is turned on and outputs a signal Soff at an "L" level, so that the divided voltage of the resistors 172 and 174 in FIG. 3 is applied to the LED driver 165. The LED driver 165 then causes the DC-DC converter 163 to stop outputting current, and the first light source 10 is turned off. Meanwhile, the second light source 20 is turned on based on the voltage Vt. In other words, when the voltage Vt is being applied and the NPN transistor 150 is turned off, the current output circuit 141 turns off the first light source 10, but the second light source 20 is turned on.

[0093] 3, even if the voltage Vt is not applied to the line L3 in Fig. 3, the NMOS transistor 216 is turned on during the period in which the voltage Vt is applied at a predetermined cycle, and therefore the NPN transistor 150 is turned off. When the NPN transistor 150 is turned off, the integrated circuit 166 outputs a PWM signal, and the LED driver 165 controls the start or stop of current output from the DC-DC converter 163 based on the PWM signal.

[0094] Furthermore, at time t2, because the voltage Vt is not applied, the NPN transistor 222 in FIG. 4 is turned off, and the line through which the signal Soff is output is set to a Hi-Z state. Therefore, the LED driver 165 causes the DC-DC converter 163 to output a current of a predetermined current value Ic, and the first light source 10 is turned on. Meanwhile, the second light source 20 is turned off based on the voltage Vt. In other words, when the voltage Vt is not applied and the NPN transistor 150 is turned off, the current output circuit 141 turns on the first light source 10 as a clearance lamp, and the second light source 20 is turned off.

[0095] At time t3, as in the case of time t1, when the voltage Vt is applied, when the NPN transistor 150 is turned off, the current output circuit 141 turns off the first light source 10 but turns on the second light source 20.

[0096] At time t4, similarly to time t2, when the voltage Vt is not applied, the NPN transistor 150 turns off, and the current output circuit 141 turns on the first light source 10 and turns off the second light source 20.

[0097] At times t5 and t6, the lighting circuit 30a operates in the same manner as at times t1 and t2.

[0098] At time t7, when the switch SWt is turned off, the lighting circuit 30a operates in the same manner as at time t0.

[0099] In this way, the lighting circuit 30a configured with an analog circuit can realize alternate flashing of the first light source 10 and the second light source 20 without using a microcomputer. This makes it possible to provide a lighting circuit that can easily realize alternate flashing of the turn signal and the clearance lamp.

[0100] Fig. 6 is a diagram showing an example of the operation of the lighting circuit 30a. Note that Fig. 6 assumes that an abnormality that prevents the supply of the drive current Iout2 to the second light source 20 (for example, a break in the second light source 20) does not occur in the second light source 20. Fig. 6 also shows the operation when the voltage Vc is applied.

[0101] 3 is turned on, voltage Vc is applied to line L1 and voltage Vt is not applied to line L3, so that NPN transistor 150 is turned off. When NPN transistor 150 is turned off, integrated circuit 166 outputs a PWM signal, and LED driver 165 controls start or stop of current output from DC-DC converter 163 based on the PWM signal.

[0102] Then, the LED driver 165 causes the DC-DC converter 163 to output a current of a predetermined current value Ic. Therefore, the current output circuit 141 outputs a drive current Iout1 of the predetermined current value Ic to the first light source 10. Then, the first light source 10 lights up as a clearance lamp. In other words, when the NPN transistor 150 is turned off, the current output circuit 141 outputs to the first light source 10 the drive current Iout1 of the predetermined current value Ic that lights up the first light source 10 as a clearance lamp.

[0103] 3, the NMOS transistor 216 is turned on, and the NPN transistor 150 remains off. When the NPN transistor 150 turns off, the integrated circuit 166 outputs a PWM signal, and the LED driver 165 controls the start or stop of current output from the DC-DC converter 163 based on the PWM signal.

[0104] However, while the voltage Vt is being applied, the NPN transistor 222 in FIG. 4 is turned on and outputs a signal Soff at an "L" level, so that the divided voltage of the resistors 172 and 174 in FIG. 3 is applied to the LED driver 165. The LED driver 165 then causes the DC-DC converter 163 to stop outputting current, and the first light source 10 is turned off. Meanwhile, the second light source 20 is turned on based on the voltage Vt. In other words, when the voltage Vt is being applied and the NPN transistor 150 is turned off, the current output circuit 141 turns off the first light source 10, but the second light source 20 is turned on.

[0105] 3, even if the voltage Vt is not applied to the line L3 in Fig. 3, the NMOS transistor 216 is turned on during the period in which the voltage Vt is applied at a predetermined cycle, and therefore the NPN transistor 150 is turned off. When the NPN transistor 150 is turned off, the integrated circuit 166 outputs a PWM signal, and the LED driver 165 controls the start or stop of current output from the DC-DC converter 163 based on the PWM signal.

[0106] Furthermore, at time t12, because the voltage Vt is not applied, the NPN transistor 222 in FIG. 4 is turned off, and the line through which the signal Soff is output is set to a Hi-Z state. Therefore, the LED driver 165 causes the DC-DC converter 163 to output a current of a predetermined current value Ic, and the first light source 10 is turned on. Meanwhile, the second light source 20 is turned off based on the voltage Vt. In other words, when the voltage Vt is not applied and the NPN transistor 150 is turned off, the current output circuit 141 turns on the first light source 10 as a clearance lamp, and the second light source 20 is turned off.

[0107] At time t13, as in the case of time t11, when the voltage Vt is applied, when the NPN transistor 150 is turned off, the current output circuit 141 turns off the first light source 10 but turns on the second light source 20.

[0108] At time t14, similarly to the case of time t12, when the voltage Vt is not applied, the NPN transistor 150 turns off, and the current output circuit 141 turns on the first light source 10 and turns off the second light source 20.

[0109] At times t15 and t16, the lighting circuit 30a operates in the same manner as at times t11 and t12.

[0110] At time t17, when the switch SWt is turned off, the lighting circuit 30a operates in the same manner as at time t10.

[0111] In this way, the lighting circuit 30a configured with an analog circuit can realize alternate flashing of the first light source 10 and the second light source 20 without using a microcomputer. This makes it possible to provide a lighting circuit that can easily realize alternate flashing of the turn signal and the clearance lamp.

[0112] <<Operation of the lighting circuit 30a when an abnormality occurs in the second light source 20>> Figure 7 is a diagram showing an example of the operation of the lighting circuit 30a. It is assumed that, at time t24 in Figure 7, an abnormality occurs in the second light source 20, preventing the supply of the drive current Iout2 to the second light source 20 (for example, a disconnection in the second light source 20). Figure 7 also shows the operation when the voltage Vd is applied. The operation from times t20 to t23 in Figure 7 is the same as the operation from times t0 to t3 in Figure 5, and the operation at time t25 is the same as the operation at time t7 in Figure 5, except that the determination circuit 130 outputs a signal Lout at an "L" level.

[0113] At time t24, when an abnormality occurs in the second light source 20 in the lighting fixture 1a in Fig. 2, the second light source 20 in the lighting fixture 1a is turned off. Meanwhile, before times t24 to t25, in order to light the second light source 20 in the lighting fixture 1b with a high flasher, the voltage Vt is applied at a period shorter than the predetermined period, and the NMOS transistor 216 in Fig. 4 outputs the signal Scntl at the "L" level. As a result, the NPN transistor 150 is turned off, and the integrated circuit 166 outputs a PWM signal.

[0114] Furthermore, the output control circuit 201 sets the line that outputs the signal Soff to a Hi-Z state based on the "L" level signal Lout, and the LED driver 165 causes the DC-DC converter 163 to output a current of a predetermined current value Ic. Then, the first drive circuit 100 lights up the first light source 10 as a clearance lamp with a drive current Iout1 of the predetermined current value Ic.

[0115] As a result, the lighting circuit 30a can turn on the first light source 10 as a daytime running lamp during the period when the voltage Vt is not being periodically applied, and can turn on the first light source 10 in the lamp 1a as a clearance lamp and the second light source 20 in the lamp 1b as a high flasher before time t24-t25.

[0116] FIG. 8 is a diagram showing an example of the operation of the lighting circuit 30a. It is assumed that, at time t34 in FIG. 8, an abnormality occurs in the second light source 20, preventing the supply of the drive current Iout2 to the second light source 20 (e.g., a disconnection in the second light source 20). FIG. 8 is also a diagram showing the operation when the voltage Vc is applied. The operation from time t30 to t33 in FIG. 8 is the same as the operation from time t10 to t13 in FIG. 6, and the operation from time t34 to before t35 in FIG. 8 is the same as the operation from time t24 to before t25 in FIG. 7.

[0117] 6. The operation at time t35 is the same as the operation at time t17 in Fig. 6, except that the determination circuit 130 outputs a signal Lout at an "L" level. The difference between the operation in Fig. 7 and the operation in Fig. 8 is that during the period when the voltage Vt is not periodically applied, the first drive circuit 100 lights up the first light source 10 as a clearance lamp with a drive current Iout1 having a predetermined current value Ic.

[0118] As a result, the lighting circuit 30a can light the first light source 10 as a clearance lamp during the period when the voltage Vt is not periodically applied, and can light the first light source 10 in the lamp 1a as a clearance lamp and light the second light source 20 in the lamp 1b as a high flasher before time t34-t35.

[0119] 3 is a diagram showing an example of the configuration of the lighting circuit 30b. The lighting circuit 30b includes a first drive circuit 100, a second drive circuit 110, a control circuit 120b, and a determination circuit 130.

[0120] 9 is a diagram showing an example of the configuration of the control circuit 120b. The control circuit 120b controls the first drive circuit 100 based on the voltage Vt, and when an abnormality (e.g., a break) occurs in the second light source 20, causes the DC-DC converter 163 to output a current via the LED driver 165. The control circuit 120b includes a switch control circuit 200b and an output control circuit 201.

[0121] <<Switch Control Circuit 200b>> The switch control circuit 200b is a circuit that outputs a signal Scntl that controls the NPN transistor 150. Specifically, the switch control circuit 200b outputs an “L” level signal Scntl to turn off the NPN transistor 150 during a period in which the voltage Vt is applied to the line L3 at a predetermined cycle.

[0122] On the other hand, when an abnormality occurs in the second light source 20, the switch control circuit 200b sets the line that outputs the signal Scntl to a Hi-Z state, and the NPN transistor 150 turns on and off depending on whether or not the voltage Vd is applied to the line L2. The switch control circuit 200b includes resistors 210, 214, and 215, a Zener diode 211, a diode 212, capacitors 213 and 217, an NMOS transistor 216, and a discharge circuit 218.

[0123] <<Discharge Circuit 218>> When an abnormality occurs in the second light source 20, the discharge circuit 218 puts the line that outputs the signal Scntl to the NMOS transistor 216 into a Hi-Z state, and when the voltage Vd is applied, causes the first drive circuit 100 to supply a drive current Iout1 of a predetermined current value Id to the first light source 10.

[0124] On the other hand, when an abnormality occurs in the second light source 20, the discharge circuit 218 puts the line that outputs the signal Scntl to the NMOS transistor 216 into a Hi-Z state, and when the voltage Vc is applied, causes the first drive circuit 100 to supply a drive current Iout1 of a predetermined current value Ic to the first light source 10. The discharge circuit 218 includes resistors 300 and 302, an NPN transistor 301, and an NMOS transistor 303.

[0125] Resistor 300 is provided between a line to which voltage Vcc is applied and the collector of NPN transistor 301, and NPN transistor 301 has a base connected to the anode of diode 225, an emitter grounded, and a collector connected to resistor 300.

[0126] The resistor 302 is provided between the ground and the connection point between the resistor 300 and the collector of the NPN transistor 301. The NMOS transistor 303 has a gate connected to the connection point between the resistor 300 and the collector of the NPN transistor 301, a source grounded, and a drain connected to the gate of the NMOS transistor 216.

[0127] Therefore, when the determination circuit 130 determines that the second light source 20 is abnormal, outputs a signal Lout at the "L" level, and turns off the NPN transistor 301, the resistor 300, together with the resistor 302, turns on the NMOS transistor 303.

[0128] Furthermore, when the determination circuit 130 outputs a signal Lout at an "L" level and the NMOS transistor 303 is turned on, the capacitor 213 is always discharged, so the line that outputs the signal Scntl is set to a Hi-Z state. On the other hand, when the second light source 20 is normal, the NMOS transistor 303 is turned off and the capacitor 213 is not discharged, so the NMOS transistor 216 turns on and off based on the voltage Vt.

[0129] <<Operation of the lighting circuit 30b when an abnormality occurs in the second light source 20>> Figure 10 is a diagram showing an example of the operation of the lighting circuit 30b. It is assumed that at time t44 in Figure 10, an abnormality occurs in the second light source 20 such that the drive current Iout2 cannot be supplied to the second light source 20 (for example, a break in the second light source 20). Figure 10 is also a diagram showing the operation when the voltage Vd is applied.

[0130] Furthermore, the operation from time t40 to t43 in FIG. 10 is the same as the operation from time t0 to t3 in FIG. 5, and the operation at time t45 is the same as the operation at time t7 in FIG. 5, except that the determination circuit 130 outputs an “L” level signal Lout.

[0131] At time t44, when an abnormality occurs in the second light source 20 in the lamp 1a in Fig. 2, the second light source 20 in the lamp 1a is turned off. Meanwhile, before times t44 to t45, the voltage Vt is applied at a period shorter than the predetermined period to light the second light source 20 in the lamp 1b with a high flasher. However, because the discharge circuit 218 discharges the capacitor 213, the NMOS transistor 216 in Fig. 9 puts the line that outputs the signal Scntl into a Hi-Z state.

[0132] Furthermore, because voltage Vd is applied to line L2, NPN transistor 150 is turned on, and integrated circuit 166 outputs a DC signal. Furthermore, output control circuit 201 sets the line that outputs signal Soff to a Hi-Z state based on signal Lout at the "L" level, and LED driver 165 causes DC-DC converter 163 to output a current of predetermined current value Id. Then, first drive circuit 100 lights first light source 10 as a daytime running lamp with drive current Iout1 of predetermined current value Id.

[0133] As a result, the lighting circuit 30b lights the first light source 10 as a daytime running lamp during the period when the voltage Vt is not being periodically applied, and lights the first light source 10 in the lamp 1a as a daytime running lamp before time t44 to t45, and lights the second light source 20 in the lamp 1b with a high flasher.

[0134] Fig. 11 is a diagram showing an example of the operation of the lighting circuit 30b. It is assumed that at time t54 in Fig. 11, an abnormality occurs in the second light source 20, preventing the supply of the drive current Iout2 to the second light source 20 (for example, a break in the second light source 20). Fig. 11 also shows the operation when the voltage Vc is applied.

[0135] 11 is the same as the operation from time t10 to t13 in Fig. 6, and the operation at time t55 is the same as the operation at time t17 in Fig. 6, except that the determination circuit 130 outputs an "L" level signal Lout. The difference between the operations in Fig. 10 and Fig. 11 is that during a period in which the voltage Vt is not periodically applied and after an abnormality occurs in the second light source 20, the first drive circuit 100 is controlled so that the first light source 10 is turned on as a clearance lamp with a drive current Iout1 of a predetermined current value Ic.

[0136] As a result, the lighting circuit 30b can light the first light source 10 as a clearance lamp during the period when the voltage Vt is not being applied periodically, and can light the first light source 10 in the lamp 1a as a clearance lamp and light the second light source 20 in the lamp 1b as a high flasher before times t44 to t45.

[0137] <<Lighting Patterns of Lighting Fixtures 1a, 1b by Pattern>> Fig. 12 is a diagram summarizing the lighting states of the first light source 10 and the second light source 20 by pattern. Patterns 1 to 7 are lighting patterns when the second light source 20 of the lighting fixture 1a is normal. Patterns 8 to 11 are lighting patterns of the lighting fixture 1b when an abnormality occurs in the second light source 20 of the lighting fixture 1a. Patterns 12 to 18 are lighting patterns of the lighting fixture 1a when an abnormality occurs in the second light source 20 of the lighting fixture 1a.

[0138] Patterns 1 to 6 show the operation of the lighting circuit 30a when there is no abnormality in the second light source 20, and patterns 7 to 11 show the operation of the lighting circuit 30a on the lighting fixture 1b side when there is an abnormality in the second light source 20 of the lighting fixture 1a. Patterns 12 to 18 show the operation of the lighting circuit 30a of the lighting fixture 1a when there is an abnormality in the second light source 20 of the lighting fixture 1a.

[0139] Pattern 1 is a pattern in which switch SWd is turned on, switches SWc and SWt are turned off, and the daytime running lamps are turned on alone, which corresponds to the operation at time t0 in Figure 5, and only the first light source 10 is turned on as a daytime running lamp.

[0140] Pattern 2 is a pattern in which switch SWc is turned on, switches SWd and SWt are turned off, and the clearance lamp is turned on alone, which corresponds to the operation at time t10 in FIG. 6, and only the first light source 10 is turned on as the clearance lamp.

[0141] Pattern 3 is a pattern in which the switches SWd and SWc are turned on, the switch SWt is turned off, and only the first light source 10 is turned on as a daytime running lamp.

[0142] Pattern 4 is a pattern in which the switches SWd and SWc are turned off, the switch SWt is turned on, and only the second light source 20 is turned on.

[0143] Pattern 5 is a pattern in which switches SWd and SWt are turned on, switch SWc is turned off, and voltage Vt is applied at a predetermined cycle, and corresponds to the operation from time t1 to time t7 in Fig. 5. Furthermore, first light source 10 is turned on as a clearance lamp, and first light source 10 and second light source 20 alternately blink.

[0144] Pattern 6 is a pattern when switches SWc and SWt are turned on, switch SWd is turned off, and voltage Vt is applied at a predetermined period, which corresponds to the operation from time t11 to time t17 in Figure 6, and the first light source 10 is lit as a clearance lamp while the first light source 10 and the second light source 20 flash alternately.

[0145] Pattern 7 is a pattern when switches SWd, SWc, and SWt are turned on and voltage Vt is applied at a predetermined period, and the first light source 10 lights up as a clearance lamp while the first light source 10 and the second light source 20 flash alternately.

[0146] Pattern 8 is a pattern when, on the lighting fixture 1b side, the switches SWd and SWt are turned on, the switch SWc is turned off, and the voltage Vt is applied in the high flasher mode.

[0147] Pattern 9 is a pattern when, on the lighting fixture 1b side, the switches SWc and SWt are turned on, the switch SWd is turned off, and the voltage Vt is applied in the high flasher mode.

[0148] Pattern 10 is a pattern when the switches SWd, SWc, and SWt are turned on on the lighting fixture 1b side and the voltage Vt is applied in high flasher mode.

[0149] Pattern 11 is a pattern when, on the lighting fixture 1b side, the switch SWt is turned on, the switches SWd and SWc are turned off, and the voltage Vt is applied in the high flasher mode.

[0150] Pattern 12 is a pattern when, on the lighting fixture 1a side, switches SWd and SWt are turned on, switch SWc is turned off, and voltage Vt is applied by the high flasher, which corresponds to the operation from time t24 to t25 in Figure 7, and the first light source 10 is turned on as a clearance lamp and the second light source 20 is turned off.

[0151] Pattern 13 is a pattern when, on the lighting fixture 1a side, switches SWc and SWt are turned on, switch SWd is turned off, and voltage Vt is applied by the high flasher, and corresponds to the operation from time t34 to t35 in Figure 8, in which the first light source 10 is lit as a clearance lamp and the second light source 20 is turned off.

[0152] Pattern 14 is a pattern when switches SWd, SWc, and SWt are turned on on the lighting fixture 1a side and voltage Vt is applied in high flasher mode, in which the first light source 10 is lit as a clearance lamp and the second light source 20 is turned off.

[0153] Pattern 15 is a pattern when, on the lighting fixture 1a side, the switch SWt is turned on, the switches SWd and SWc are turned off, and the voltage Vt is applied in high flasher mode, and the first light source 10 and the second light source 20 are turned off.

[0154] Pattern 16 is a pattern when, on the lighting fixture 1a side, switches SWd and SWt are turned on, switch SWc is turned off, and voltage Vt is applied by the high flasher, and corresponds to the operation from time t44 to t45 in Figure 10, in which the first light source 10 is turned on as a daytime running lamp and the second light source 20 is turned off.

[0155] Pattern 17 is a pattern when, on the lighting fixture 1a side, switches SWc and SWt are turned on, switch SWd is turned off, and voltage Vt is applied by the high flasher, and corresponds to the operation from time t54 to t55 in Figure 11, in which the first light source 10 is lit as a clearance lamp and the second light source 20 is turned off.

[0156] Pattern 18 is a pattern when switches SWd, SWc, and SWt are turned on on the lamp 1a side and voltage Vt is applied with high flasher, in which case the first light source 10 is lit as a daytime running lamp and the second light source 20 is turned off.

[0157] Summary The above describes the lighting circuit 30a of this embodiment. The lighting circuit 30a includes a first drive circuit 100, a second drive circuit 110, and a control circuit 120a. This makes it possible to provide a lighting circuit that satisfies the regulatory requirement that the turn signal lamps emit amber light and that easily achieves alternate flashing of the turn signal lamps and clearance lamps.

[0158] Furthermore, when an abnormality (e.g., a disconnection) occurs in the second light source 20, the control circuit 120a controls the first drive circuit 100 so that the first light source 10 is turned on at a brightness (clearance lamp) according to a predetermined current value Ic based on either the voltage Vd or Vc during the period in which the voltage Vt is applied at a predetermined cycle. This allows the first light source 10 to be turned on when the second light source 20 is not turned on.

[0159] Furthermore, when an abnormality (e.g., a disconnection) occurs in the second light source 20, the control circuit 120a controls the first drive circuit 100 based on either the voltage Vd or Vc so that the first light source 10 is illuminated at a brightness corresponding to a predetermined current value Ic (clearance lamp) during the period in which the voltage Vt is applied at a predetermined cycle. Furthermore, when an abnormality (e.g., a disconnection) occurs in the second light source 20, the control circuit 120b controls the first drive circuit 100 based on either the voltage Vd or Vc so that the first light source 10 is illuminated at a brightness corresponding to a predetermined current value Id (daytime running lamp) during the period in which the voltage Vt is applied at a predetermined cycle. Therefore, depending on the customer's request, the illumination of the first light source 10 when an abnormality occurs in the second light source 20 can be switched to a daytime running lamp or a clearance lamp depending on the presence or absence of the discharge circuit 218.

[0160] The first drive circuit 100 includes a switch 140 and a current output circuit 141, and the control circuit 120a includes a switch control circuit 200a and an output control circuit 201. This makes it possible to provide a lighting circuit that can easily achieve alternate flashing of the turn signal lamps and the clearance lamps.

[0161] Furthermore, the lighting circuit 30a includes a determination circuit 130, and when the output control circuit 201 determines that an abnormality (e.g., a break) has occurred in the second light source 20, it operates the current output circuit 141 regardless of the period during which the voltage Vt is applied to the line L3. This allows the first light source 10 to be turned on when the second light source 20 does not light up.

[0162] Furthermore, the lighting circuit 30b includes a determination circuit 130, and when it is determined that an abnormality (e.g., a break) has occurred in the second light source 20, the switch control circuit 200b stops controlling the switch 140, and when it is determined that an abnormality has occurred in the second light source 20, the output control circuit 201 operates the current output circuit 141 regardless of the period during which the voltage Vt is applied to the line L3. This makes it possible to switch the illumination of the first light source 10 to either a daytime running lamp or a clearance lamp depending on the presence or absence of the discharge circuit 218, according to customer requests, when an abnormality has occurred in the second light source 20.

[0163] Furthermore, the voltages Vd, Vc, and Vt have the same level. This allows the first light source 10 and the second light source 20 to be turned on by the battery 40 alone.

[0164] Furthermore, when the voltage Vc is applied to the line L1 and the voltage Vd is applied to the line L2, the first drive circuit 100 supplies a drive current Iout1 of a predetermined current value Id to the first light source 10. This allows priority to be given to lighting the first light source 10 as a daytime running lamp.

[0165] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. Furthermore, the present invention may be modified or improved without departing from the spirit thereof, and the present invention includes equivalents thereof.

[0166] REFERENCE SIGNS LIST 1 Vehicle lamp 1a, 1b Lamp 10 First light source 20 Second light source 30a, 30b Lighting circuit 40 Battery 50a, 50b Lamp 51a, 51b Light-emitting surface 100 First drive circuit 110 Second drive circuit 120a, 120b Control circuit 130 Determination circuit 140 Switch 141 Current output circuit 150, 222, 226, 301 NPN transistor 151, 170, 173, 180, 213, 217, 223 Capacitor 160, 161 Diode 162, 182 Input filter 163, 183 DC-DC converter 164, 184 Output filter 165, 185 LED driver 166 Integrated circuit 167 to 169, 171, 172, 174, 210, 214, 215, 220, 224, 227, 228, 300, 302 Resistors 175, 181, 212, 225 Diodes 190 Comparator 191 Latch circuit 200a, 200b Switch control circuit 201 Output control circuit 211, 221 Zener diodes 216, 229, 303 NMOS transistor 218 Discharge circuit

Claims

1. A lighting circuit applicable to a vehicle lamp including a first light source and a second light source, comprising: a first drive circuit that supplies a first drive current to the first light source based on a first voltage applied to a first line, and that supplies a second drive current larger than the first drive current to the first light source based on a second voltage applied to a second line; a second drive circuit that supplies a third drive current to the second light source at a predetermined cycle based on a third voltage applied to a third line at the predetermined cycle during a first period; and a control circuit that controls the first drive circuit so that the first light source and the second light source are alternately lit at a brightness according to the first drive current, based on the third voltage applied to the third line at the predetermined cycle during the first period.

2. A lighting circuit as claimed in claim 1, wherein when an abnormality occurs in which the third drive current cannot be supplied to the second light source, the control circuit controls the first drive circuit so that the first light source is lit at a brightness corresponding to the first drive current during the first period, based on either the first or second voltage.

3. A lighting circuit as claimed in claim 1, wherein when an abnormality occurs in which the third drive current cannot be supplied to the second light source, the control circuit controls the first drive circuit based on either the first or second voltage during the first period so that the first light source is lit at a brightness corresponding to the first or second drive current.

4. A lighting circuit as claimed in claim 1, wherein the first drive circuit includes: a switch that is in a first state when the first voltage is applied to the first line and in a second state when the second voltage is applied to the second line; and a current output circuit that outputs the first drive current when the switch is in the first state and outputs the second drive current when the switch is in the second state; and the control circuit includes: a switch control circuit that sets the switch to the first state during the first period; and an output control circuit that stops operation of the current output circuit during a period during which the third voltage is applied to the third line and operates the current output circuit during a period when the third voltage is not applied to the third line.

5. A lighting circuit as claimed in claim 4, further comprising a determination circuit for determining whether an abnormality has occurred that prevents the third drive current from being supplied to the second light source, and wherein, when it is determined that the abnormality has occurred in the second light source, the output control circuit operates the current output circuit regardless of the period during which the third voltage is being applied to the third line.

6. A lighting circuit according to claim 4, further comprising a determination circuit for determining whether an abnormality has occurred that prevents the supply of the third drive current to the second light source, wherein the switch control circuit stops control of the switch when it is determined that the abnormality has occurred in the second light source, and the output control circuit operates the current output circuit regardless of the period during which the third voltage is being applied to the third line when it is determined that the abnormality has occurred in the second light source.

7. A lighting circuit according to claim 1, wherein the first to third voltages have the same level.

8. A lighting circuit according to claim 1, wherein the first drive circuit supplies the second drive current to the first light source when a first voltage is applied to the first line and the second voltage is applied to the second line.

9. A vehicular lamp comprising: a first light source; a second light source; and a lighting circuit that lights up the first and second light sources, wherein the lighting circuit includes: a first driving circuit that supplies a first driving current to the first light source based on a first voltage applied to a first line, and that supplies a second driving current larger than the first driving current to the first light source based on a second voltage applied to a second line; a second driving circuit that supplies a third driving current to the second light source at a predetermined cycle based on a third voltage applied to a third line at the predetermined cycle during a first period; and a control circuit that controls the first driving circuit so that the first light source and the second light source are alternately turned on at a brightness according to the first driving current, based on the third voltage applied to the third line at the predetermined cycle during the first period.

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