Lighting circuit and vehicle lamp

Abstract

To provide a lightning circuit which can detect an abnormality with a simple configuration.SOLUTION: A lightning circuit applied to a lamp fitting including a first light source and a second light source serially connected to the first light source comprises: a first switch which is provided in parallel to the first light source; a second switch which is provided in parallel to the second light source; a drive circuit which supplies the drive current to the first and second light sources; and a control circuit which controls on / off of the first and second switches to turn on or off the first and second light sources. The control circuit, in a first period in which the one of the first and second light sources is turned off and the other of the first and second light sources is turned on in such a state that the one of the first and second light sources is intermittently turned on, detects an abnormality in the other of the light sources on the basis of the output voltage of the drive circuit.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent Document 1 discloses a lighting circuit suitable for a lamp (for example, a vehicle lamp) that controls the lighting of two light sources connected in series and is capable of detecting abnormalities in the two light sources. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-87830 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the lighting circuit of Patent Document 1, voltage detection circuits (voltage divider circuits) are provided at two points (upstream of each light source) in the current path of the drive current, and abnormalities in each light source are detected based on the output of the two voltage divider circuits. Therefore, two voltage divider circuits are required, and two analog-to-digital conversion circuits (A / D conversion circuits) that convert the output of the voltage divider circuits into a digital signal are also required.

[0005] An object of the present invention is to provide a lighting circuit capable of detecting an abnormality with a simpler configuration. [Means for solving the problem]

[0006] The main present invention for solving the above-mentioned problems is a lighting circuit applied to a lamp including a first light source and a second light source connected in series to the first light source, the lighting circuit including a first switch provided in parallel to the first light source, a second switch provided in parallel to the second light source, a drive circuit that supplies drive current to the first and second light sources, and a control circuit that turns on or off the first and second light sources by controlling the on / off of the first and second switches, wherein the control circuit detects an abnormality in one of the first and second light sources based on the output voltage of the drive circuit during a first period in which one of the first and second light sources is turned on and the other of the first and second light sources is turned on while the one light source is turned off in a state in which the one of the first and second light sources is intermittently turned on. Effect of the Invention

[0007] According to the present invention, it is possible to provide a lighting circuit capable of detecting an abnormality with a simple configuration. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram of a vehicle lamp 1 using a lighting circuit 40 of the present embodiment. [Diagram 2] FIG. 4 is a diagram showing an example of a functional block realized by a microcomputer 45. [Diagram 3] 5 is a diagram for explaining an abnormality detection operation by the lighting circuit 40 of the present embodiment. FIG. [Figure 4] FIG. 11 is an explanatory diagram for determining an abnormality. [Diagram 5] This is to explain a modified example of the operation of the lighting circuit 40 in detecting an abnormality. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] At least the following points will become apparent from the description of this specification and the accompanying drawings.

[0010] ===== Implementation form ===== <<Configuration of vehicle lamp 1>> FIG. 1 is a diagram showing an example of the configuration of a vehicle lamp 1 using a lighting circuit 40 according to the present embodiment.

[0011] The vehicular lamp 1 is a lamp that turns on a first light source 10 and a second light source 20 based on a voltage Vbat of a vehicle battery 2. The vehicular lamp 1 includes the first light source 10, the second light source 20, and a lighting circuit .

[0012] <1st light source 10> The first light source 10 is, for example, a light source for low beam, and is connected between terminals E and F (described later) of the lighting circuit 40. Note that the low beam is intended to illuminate the vicinity of the vehicle, and light distribution regulations are established so as not to cause glare to oncoming vehicles or preceding vehicles, and is mainly used when traveling in urban areas.

[0013] The first light source 10 has at least one light emitting element 11. In this embodiment, a light emitting diode (LED) is used as the light emitting element 11. However, the light emitting element 11 is not limited to an LED, and may be, for example, another semiconductor light emitting element such as a laser diode (LD) or an organic EL element. Note that the same element (LED) as the light emitting element 11 is used for the light emitting element 21 of the second light source 20 described later.

[0014] 1, for simplicity, the number of light emitting elements 11 in the first light source 10 is one, but in this embodiment, the first light source 10 has a plurality of light emitting elements 11 (e.g., six) connected in series. The voltage (forward voltage) generated by turning on the first light source 10 is designated as voltage VF1.

[0015] <Second light source 20> The second light source 20 is, for example, a light source for high beam, and is connected between terminal G and terminal H (described later) of the lighting circuit 40. Note that the high beam illuminates a wide range and a long distance ahead of the vehicle, and is mainly used when traveling at high speed on a road with few oncoming vehicles or preceding vehicles. As described later, since terminal F and terminal G are connected in the lighting circuit 40, the second light source 20 is connected in series with the first light source 10.

[0016] Moreover, the second light source 20 has at least one light emitting element 21. For simplification, the number of light emitting elements 21 in the second light source 20 is one in Fig. 1, but in the second light source 20 of this embodiment, a plurality of light emitting elements 21 (e.g., three) are connected in series. Moreover, a voltage (forward voltage) generated by turning on the second light source 20 is designated as a voltage VF2.

[0017] If the number of light-emitting elements 11 in the first light source 10 differs from the number of light-emitting elements 21 in the second light source 20, the values ​​of voltage VF1 and voltage VF2 will differ. In the lighting circuit 40 of this embodiment, even if the values ​​of voltage VF1 and voltage VF2 are significantly different, it is possible to reliably detect an abnormality for each light source. Note that even if voltage VF1 and voltage VF2 are the same (the number of light-emitting elements 11 and light-emitting elements 21 are the same), it is possible to similarly detect an abnormality.

[0018] <Lighting circuit 40> The lighting circuit 40 is a circuit that turns on the first light source 10 and the second light source 20 in accordance with an instruction from a control device (not shown: hereinafter also referred to as a vehicle-side ECU) provided on the vehicle side. The lighting circuit 40 of this embodiment includes a drive circuit 41, a voltage dividing circuit 42, a memory circuit 44, a microcomputer 45, switches SW1 and SW2, and terminals A to H. The lighting circuit 40 is a module in which the above-mentioned circuits and terminals are attached to a board.

[0019] The terminal A is a terminal connected to the positive electrode of the battery 2 via the lighting switch SW0, and when the lighting switch SW0 is turned on, a power supply voltage (voltage Vbat) is applied from the battery 2.

[0020] Terminal B is a terminal connected to the negative electrode of battery 2, and a ground level voltage is applied from battery 2.

[0021] A control signal S1 is input from the vehicle ECU to the terminal C. The control signal S1 is a signal that instructs the first light source 10 and the second light source 20 to be turned on or off.

[0022] The terminal D is a terminal for outputting a detection signal S2 to the vehicle-side ECU. The detection signal S2 is a signal indicating that an abnormality has been detected in at least one of the first light source 10 and the second light source 20.

[0023] Terminals E and F are terminals for connecting the first light source 10. Furthermore, an output voltage Vout of a drive circuit 41 is applied to terminal E.

[0024] The terminal G and the terminal H are terminals for connecting the second light source 20. In the lighting circuit 40, the terminal G is connected to the terminal F, and the terminal H is connected to the terminal B.

[0025] The switch SW1 is a switch provided between terminals E and F (in other words, in parallel with the first light source 10) and corresponds to a "first switch." When the switch SW1 is on (conducting), a path is formed through which a current is supplied to the second light source 20, bypassing the first light source 10. As a result, no current is supplied to the first light source 10, so the first light source 10 is not turned on and is in an extinguished state. On the other hand, when the switch SW1 is off (non-conducting), a current is supplied to the first light source 10, so that the first light source 10 is turned on.

[0026] The switch SW2 is a switch provided between the terminal G and the terminal H (in other words, in parallel to the second light source 20), and corresponds to a "second switch." When the switch SW2 is on, a path that bypasses the second light source 20 is formed. As a result, no current is supplied to the second light source 20, so the second light source 20 is not turned on and is in an extinguished state. On the other hand, when the switch SW2 is off, a current is supplied to the second light source 20, so that the second light source 20 is turned on.

[0027] The drive circuit 41 is a circuit (constant current circuit) that supplies a drive current for lighting the first light source 10 and the second light source 20 based on the voltage Vbat of the battery 2, and is provided between terminals A and E. The drive circuit 41 is configured, for example, with a step-down switching regulator (DC-DC converter). Note that the drive circuit 41 is not limited to a step-down type, and may be a step-up type. Furthermore, the drive circuit 41 is not limited to a switching regulator, and may be, for example, a linear regulator.

[0028] The voltage dividing circuit 42 is a circuit that divides the voltage of a node N between the drive circuit 41 and a terminal E (the output voltage Vout of the drive circuit 41). The voltage dividing circuit 42 is configured to include, for example, two resistors connected in series between the node N and the ground (GND). The voltage of the node N (the output voltage Vout) is divided by the two resistors.

[0029] The memory circuit 44 is a circuit that stores programs and various data for executing the control in the microcomputer 45, and is configured with, for example, a semiconductor memory. The memory circuit 44 also stores data related to the voltage VF1 of the first light source 10, data related to the voltage VF2 of the second light source 20, and the like.

[0030] However, the voltage VF1 of the first light source 10 and the voltage VF2 of the second light source 20 are not always constant, but vary due to individual differences and temperature. For this reason, the values ​​of the voltages VF1 and VF2 are stored in the memory circuit 44 as normal ranges having upper and lower limits. In the following, the normal range corresponding to the voltage VF1 is referred to as range R1, and the normal range corresponding to the voltage VF2 is referred to as range R2. The range R1 corresponds to the "first range", and the range R2 corresponds to the "second range". The ranges R1 and R2 are converted into values ​​(ranges) corresponding to the voltage division ratio (resistance ratio) of the voltage division circuit 42 and stored in the memory circuit 44.

[0031] As shown in FIG. 1, in the lighting circuit 40 of the present embodiment, the memory circuit 44 is provided separately from the microcomputer 45. However, this is not limited thereto, and the memory circuit 44 and the microcomputer 45 may be integrally configured.

[0032] <About Micon 45> The microcomputer 45 is a circuit that controls the operation of the vehicle lamp 1, and corresponds to a "control circuit." In this embodiment, a sampling mode is provided when the first light source 10 and the second light source 20 are turned on. In the sampling mode, the microcomputer 45 turns on and off the switches SW1 and SW2 at a predetermined period T (described later) to intermittently turn on the first light source 10 and the second light source 20, respectively.

[0033] Fig. 2 is a diagram showing an example of functional blocks realized by the microcomputer 45. Note that the microcomputer 45 is realized as a hardware configuration by elements and circuits including a computer CPU and memory, and as a software configuration by a computer program, etc., but in Fig. 2, it is shown as a functional block realized by the cooperation of these elements as appropriate. The microcomputer 45 of the present embodiment includes a control unit 451, a detection unit 452, and a transmission unit 453.

[0034] The control unit 451 turns on and off the switches SW1 and SW2 based on a control signal S1 input from a vehicle-side ECU (not shown). In other words, the control unit 451 turns on or off the first light source 10 by controlling the on / off of the switch SW1. The control unit 451 also turns on or off the second light source 20 by controlling the on / off of the switch SW2.

[0035] The detection unit 452 detects the presence or absence of an abnormality in the first light source 10 and the second light source 20 based on the output (divided voltage of the output voltage Vout) of the voltage dividing circuit 42. In this embodiment, the input port of the microcomputer 45 connected to the voltage dividing circuit 42 is configured as an A / D conversion input port having an analog-digital conversion function, and the output of the voltage dividing circuit 42 is converted into a digital signal (digital data) at the input port of the microcomputer 45. However, this is not limited to this, and for example, an A / D conversion circuit may be provided in the voltage dividing circuit 42 to input a digital signal.

[0036] Then, the detection unit 452 compares the data acquired from the voltage-dividing circuit 42 with the data stored in the memory circuit 44. As described above, the value of the range (ranges R1, R2) stored in the memory circuit 44 is converted according to the voltage division ratio of the voltage-dividing circuit 42. Therefore, the comparison of the data of the voltage-dividing circuit 42 with the data of the memory circuit 44 in the detection unit 452 is equivalent to comparing the output voltage Vout of the drive circuit 41 with the actual normal range (ranges R1, R2).

[0037] The detection unit 452 detects an abnormality in the first light source 10 based on whether the output voltage Vout is within a range R1. Also, based on whether the output voltage Vout is within a range R2, the detection unit 452 detects an abnormality in the second light source 20. The timing (period) of detecting an abnormality in each light source will be described later.

[0038] When an abnormality is detected by the detection unit 452, the transmission unit 453 transmits a detection signal S2 indicating that an abnormality has been detected to a vehicle-side ECU (not shown).

[0039] <<About abnormality detection>> Fig. 3 is a diagram for explaining the operation of abnormality detection by the lighting circuit 40 of the present embodiment. In the pulse waveforms of the switches SW1 and SW2 shown in Fig. 3, a "high level" indicates an on state (conducting state), and a "low level" indicates an off state (non-conducting state).

[0040] The cycle T shown in the figure is a short period of, for example, 5 ms, and in this cycle T, periods (periods TA and TC) are provided in which the first light source 10 and the second light source 20 are turned off. That is, in the cycle T, the first light source 10 and the second light source 20 are controlled to be turned on intermittently. Before time t0 in Figure 3, both the first light source 10 and the second light source 20 are turned on, and at time t0, the sampling mode is entered.

[0041] During a period TA from time t0 to time t1, the control unit 451 of the microcomputer 45 turns off the switch SW1 and turns on the switch SW2. That is, the first light source 10 is turned on and the second light source 20 is turned off. Therefore, during the period TA, if the first light source 10 is normal, the voltage of the node N becomes VF1. The detection unit 452 of the microcomputer 45 compares the output of the voltage dividing circuit 42 with the data of the storage circuit 44, and detects whether the output voltage Vout of the drive circuit 41 is included in a range R1 corresponding to the voltage VF1.

[0042] During a period TB from time t1 to time t2, the control unit 451 of the microcomputer 45 turns off both the switch SW1 and the switch SW2. That is, the first light source 10 and the second light source 20 are both turned on. Therefore, during the period TB, if the first light source 10 and the second light source 20 are both normal, the voltage of the node N becomes (VF1+VF2). Note that in this embodiment, no abnormality detection of each light source is performed during this period TB. The reason for this will be described later.

[0043] During a period TC from time t2 to time t3, the control unit 451 of the microcomputer 45 turns on the switch SW1 and turns off the switch SW2. That is, the first light source 10 is turned off and the second light source 20 is turned on. Therefore, during the period TC, if the second light source 20 is normal, the voltage of the node N becomes VF2. The detection unit 452 of the microcomputer 45 compares the output of the voltage dividing circuit 42 with the data of the storage circuit 44, and detects whether the output voltage Vout of the drive circuit 41 is included in a range R2 corresponding to the voltage VF2.

[0044] Thereafter, the same process is repeated in the cycle T. As a result, the first light source 10 and the second light source 20 are turned on intermittently at different timings. The cycle T corresponds to a "predetermined cycle", one of the periods TA and TC (for example, the period TA) corresponds to a "first period", and the other (for example, the period TC) corresponds to a "second period". The period TB corresponds to a "third period".

[0045] FIG. 4 is an explanatory diagram of abnormality determination. The figure shows a range R1 of the voltage VF1 when the first light source 10 is turned on normally, and a range R2 of the voltage VF2 when the second light source 20 is turned on normally. In this embodiment, the number of light-emitting elements 11 of the first light source 10 is different from the number of light-emitting elements 21 of the second light source 20, and therefore the range R1 and the range R2 are different.

[0046] The detection unit 452 of the microcomputer 45 can ascertain the light source (either the first light source 10 or the second light source 20) that is the target of abnormality detection based on the period (period TA, period TC) during which abnormality detection is performed. Then, the detection unit 452 determines that the output voltage Vout is "normal" if it is within the normal range of the light source, and determines that the output voltage Vout is "abnormal" if it is not within the normal range.

[0047] For example, in a period TA in which the first light source 10 is turned on and the second light source 20 is turned off, the detection unit 452 detects whether the output voltage Vout (the voltage at node N) is within range R1. Specifically, when the output voltage Vout is the voltage indicated by the dashed line in the figure, it is within range R1, so the detection unit 452 determines that the first light source 10 is normal. When the output voltage Vout is the voltage indicated by the dashed line in the figure, it is not within range R1, so the detection unit 452 determines that the first light source 10 is abnormal.

[0048] Furthermore, in a period TC in which the second light source 20 is turned on and the first light source 10 is turned off, the detection unit 452 detects whether or not the output voltage Vout (the voltage at node N) is within range R2. Specifically, when the output voltage Vout is the voltage indicated by the dashed line in the figure, it is within range R2, so the detection unit 452 determines that the second light source 20 is normal. When the output voltage Vout is the voltage indicated by the dashed line in the figure, it is not within range R2, so the detection unit 452 determines that the second light source 20 is abnormal.

[0049] As described above, in the period TB in which both the first light source 10 and the second light source 20 are turned on, the detection unit 452 does not detect an abnormality. This is because if the normal range of (VF1+VF2) is set and an abnormality is detected in the period TB, the detection may not be performed correctly. For example, when VF2>VF1, if the light emitting element 11 of the first light source 10 is shorted, the output voltage Vout becomes VF2. There is a risk that the value of the voltage VF2 at this time will be included in the normal range of (VF1+VF2), and if it is included in the normal range, an abnormality in the first light source 10 cannot be detected.

[0050] If the output voltage Vout is higher than the upper limit of the normal range (for example, when it is the MAX value), it can be determined that the abnormality is due to an open circuit (disconnection) of the light-emitting element (light-emitting element 11, 21). If the output voltage Vout is lower than the lower limit of the normal range (for example, when it is zero), it can be determined that the abnormality is due to a short circuit (short circuit) of the light-emitting element (light-emitting element 11, 21). In this way, it is possible to distinguish between an open circuit and a short circuit and detect them.

[0051] When the detection unit 452 detects that an abnormality has occurred in either the first light source 10 or the second light source 20, the transmission unit 453 transmits a detection signal S2 indicating the result to the vehicle-side ECU.

[0052] When the vehicle-side ECU receives the detection signal S2, it notifies the driver or the like that an abnormality has occurred. Examples of notification methods include visual notification such as light emission or display, auditory notification such as sound, and tactile notification such as vibration, and the vehicle-side ECU uses any of these methods to notify the driver or the like.

[0053] As described above, the lighting circuit 40 of this embodiment can detect an abnormality in each of the first light source 10 and the second light source 20 using only the voltage at one point (node ​​N) in the current path of the drive current. That is, only one voltage divider circuit 42 and one A / D conversion circuit (in this embodiment, the A / D conversion input port of the microcomputer 45) are required. Therefore, with a simple configuration, it is possible to detect an abnormality in each light source.

[0054] <<Modifications>> FIG. 5 is a diagram for explaining a modified example of the operation of the lighting circuit 40 for detecting an abnormality. The configuration of the vehicle lamp 1 (the first light source 10, the second light source 20, and the lighting circuit 40) is the same as that of the above-described embodiment, and the same reference numerals are used.

[0055] In this modification, the turn-off time of the first light source 10 and the second light source 20 is made longer (the turn-on time is made shorter) than in the above embodiment.

[0056] During periods TD and TE from time t10 to time t12, the control unit 451 of the microcomputer 45 turns off the switch SW1 and turns on the switch SW2. That is, the first light source 10 is turned on and the second light source 20 is turned off. During these periods TD and TE, if the first light source 10 is normal, the voltage of the node N becomes VF1.

[0057] During the period TD, the detection unit 452 of the microcomputer 45 compares the output of the voltage dividing circuit 42 with the data of the storage circuit 44, and detects whether the output voltage Vout of the drive circuit 41 is included in the range R1 corresponding to the voltage VF1. Note that abnormality detection may be performed during the period TE.

[0058] In a period TF from time t12 to time t13, the control unit 451 of the microcomputer 45 turns on both the switch SW1 and the switch SW2. That is, the first light source 10 and the second light source 20 are both turned off. As a result, the voltage of the node N becomes the ground potential (earth). In this period TF, no abnormality detection is performed.

[0059] During a period TG from time t13 to time t14, the control unit 451 of the microcomputer 45 turns on the switch SW1 and turns off the switch SW2. That is, the first light source 10 is turned off and the second light source 20 is turned on. During this period TG, if the second light source 20 is normal, the voltage of the node N becomes VF2. The detection unit 452 of the microcomputer 45 compares the output of the voltage dividing circuit 42 with the data of the storage circuit 44, and detects whether the output voltage Vout of the drive circuit 41 is included in a range R2 corresponding to the voltage VF2.

[0060] Thereafter, the same process is repeated in the cycle T. As a result, the first light source 10 and the second light source 20 are each intermittently turned on. In this modified example, the first light source 10 and the second light source 20 are turned on for a shorter period (the turned off period is longer) compared to the above-mentioned embodiment (FIG. 3). Also, there is no period when both are turned on, but there is a period when both are turned off (period TG). Therefore, it is darker than the above-mentioned embodiment. Note that the cycle T corresponds to a "predetermined cycle", and one of the periods TD and TG (for example, the period TD) corresponds to a "first period", and the other (for example, the period TG) corresponds to a "second period".

[0061] In this modified example as well, by providing a period during which one of the first light source 10 and the second light source 20 is turned on and the other is turned off, it is possible to detect abnormalities in the first light source 10 and the second light source 20.

[0062] =====Summary===== The vehicle lamp 1 of this embodiment has been described above. The lighting circuit 40 of the vehicle lamp 1 includes a switch SW1 provided in parallel to the first light source 10, a switch SW2 provided in parallel to the second light source 20, a drive circuit 41 that supplies drive current to the first light source 10 and the second light source 20, and a microcomputer 45 that controls the on / off of the switches SW1 and SW2 to turn on or off the first light source 10 and the second light source 20, respectively. In a state in which one light source (e.g., the second light source 20) is intermittently turned on, the microcomputer 45 turns off the second light source 20 and detects an abnormality in the first light source 10 based on the output voltage Vout of the drive circuit 41 during a period TA in which the first light source 10 is turned on while one of the light sources (e.g., the second light source 20) is turned on. This makes it possible to detect an abnormality in the first light source 10 with a simple configuration.

[0063] Furthermore, in a state where the other light source (for example, the first light source 10) is intermittently turned on, the microcomputer 45 detects an abnormality in the second light source 20 based on the output voltage Vout of the drive circuit 41 during a period TC in which the first light source 10 is turned off and the second light source 20 is turned on. This makes it possible to detect an abnormality in the second light source 20 with a simple configuration.

[0064] Furthermore, the microcomputer 45 repeats on / off control of the switches SW1 and SW2 in a cycle T so that the first light source 10 and the second light source 20 are turned on intermittently, and the periods TA and TC are each included in the cycle T. This makes it possible to detect abnormalities in the first light source 10 and the second light source 20 with a simple configuration.

[0065] The cycle T includes a period TB during which both the first light source 10 and the second light source 20 are turned on. This allows the light to be bright even when each light source is turned on intermittently. By not detecting abnormalities in the first light source 10 and the second light source 20 during this period TB, erroneous detection can be suppressed.

[0066] Furthermore, during the period TA, the microcomputer 45 detects an abnormality in the first light source 10 based on whether the output voltage Vout is within the range R1, and during the period TC, the microcomputer 45 detects an abnormality in the second light source 20 based on whether the output voltage Vout is within the range R2. This makes it possible to reliably detect abnormalities in the first light source 10 and the second light source 20.

[0067] Moreover, the first light source 10 has at least one light emitting element 11, and the second light source 20 has at least one light emitting element 21. In the lighting circuit 40 of the present embodiment, even if the number of light emitting elements 11 of the first light source 10 and the number of light emitting elements 21 of the second light source 20 are different, it is possible to reliably detect an abnormality in each light source, which is more effective than the above case.

[0068] The lighting circuit 40 of the present embodiment is suitable for a lamp (vehicle lamp 1) used in a vehicle. However, the present invention is not limited to this, and may be applied to a lamp such as a street lamp. In this case, the same effect can be obtained.

[0069] In the above embodiment, the first light source 10 is a light source for low beam, and the second light source 20 is a light source for high beam, but this is not limited thereto. For example, the first light source 10 may be a light source for high beam, and the second light source 20 may be a light source for low beam.

[0070] Furthermore, the combination of lamps is not limited to low beam and high beam, and may be other combinations (for example, Daytime Running Lamps (DRLs), Clearance Lamps (CLLs), turn signal lamps, etc.). Note that DRLs are lamps that turn on during the day to inform pedestrians and drivers of oncoming vehicles of the presence of a moving vehicle. CLLs are lamps that are installed on the front of a vehicle to indicate the width of the vehicle and its presence. Turn signal lamps are lamps that flash to inform drivers of vehicles ahead and behind that the vehicle is turning or changing course.

[0071] In addition, in the above embodiment, there are two light sources (the first light source 10 and the second light source 20), but this is not limiting and there may be three or more light sources. In this case, too, an abnormality in each light source can be detected by performing a similar control.

[0072] The above-mentioned embodiment is for the purpose of facilitating understanding of the present invention, and is not intended to limit the present invention. Furthermore, the present invention can be modified or improved without departing from the spirit of the present invention, and it goes without saying that the present invention includes equivalents thereof. [Explanation of symbols]

[0073] 1 Vehicle lighting fixtures 2 Battery 10 1st light source 11 Light emitting element 20 Second light source 21 Light emitting element 40 Lighting circuit 41 Drive circuit 42 Voltage divider circuit 44 Memory circuit 45 Microcomputer 451 Control Unit 452 Detector 453 Transmitter SW0 Illuminated switch SW1, SW2 switches A~F terminals

Claims

1. A lighting circuit applied to a lamp including a first light source and a second light source connected in series to the first light source, a first switch provided in parallel with the first light source; a second switch provided in parallel with the second light source; a drive circuit for supplying a drive current to the first and second light sources; a control circuit that controls the first and second switches to be turned on or off, thereby turning on or off the first and second light sources, respectively; Equipped with the control circuit, in a state in which one of the first and second light sources is intermittently turned on, detects an abnormality in the other of the first and second light sources based on whether or not an output voltage of the drive circuit is within a first range during a first period in which the one of the first and second light sources is turned off and the other of the first and second light sources is turned on; in a state in which the other light source is intermittently turned on, during a second period in which the other light source is turned off and the one light source is turned on, detecting an abnormality in the one light source based on whether the output voltage is within a second range different from the first range. Lighting circuit.

2. 2. The lighting circuit according to claim 1, the control circuit repeats on / off control of the first and second switches at a predetermined cycle so that the one and the other light sources are turned on intermittently; The first and second periods are each included in the predetermined cycle. Lighting circuit.

3. 3. The lighting circuit according to claim 2, The predetermined cycle includes a third period in which both the first and second light sources are turned on. Lighting circuit.

4. The lighting circuit according to any one of claims 1 to 3, The first and second light sources each have at least one light emitting element; The number of the light-emitting elements of the first light source is different from the number of the light-emitting elements of the second light source. Lighting circuit.

5. The lighting circuit according to any one of claims 1 to 4, The lamp is a vehicle lamp used in a vehicle. Lighting circuit.

6. The first and second light sources; A lighting circuit according to any one of claims 1 to 5; A vehicle lamp comprising:

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