Lighting circuit

Abstract

To provide a lighting circuit which can simultaneously turn off a plurality of light sources.SOLUTION: There is provided a lighting circuit applied to a vehicle lamp including a plurality of light sources having a first light source connected to a power supply line and a second light source serially connected to the first light source and connected to a ground line. The lighting circuit includes: a first switch which is provided between the power supply line and the ground line; a second switch which is provided between a node on the power supply line side of the second light source and the ground line; and a control circuit which turns on or turns off each of the first and second light sources by controlling on / off of each of the plurality of switches including the first and second switches.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] As a lighting circuit for a vehicle lamp, for example, there is one that is applied to a vehicle turn signal lamp (hereinafter referred to as a "turn signal lamp") that uses a so-called sequential method technology in which multiple light sources each equipped with a light-emitting element are arranged and turned on in sequence (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6800581 [Patent Document 2] Patent No. 6687540 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, when multiple light sources are connected in series and turned on sequentially, a switch (e.g., a transistor) is connected in parallel to each of the multiple light sources, and the on / off of the corresponding light source is controlled by turning on and off each switch (see Fig. 3 of Patent Document 1 and Figs. 9 and 10 of Patent Document 2). In this case, for example, there is a risk that multiple light sources cannot be turned off simultaneously (there will be a discrepancy in the timing of turning them off) due to variations in the characteristics and operation of each switch.

[0005] An object of the present invention is to provide a lighting circuit capable of simultaneously turning off a plurality of light sources. [Means for solving the problem]

[0006] The main present invention for solving the above-mentioned problems is a lighting circuit applied to a vehicle lamp having a plurality of light sources including a first light source connected to a power supply line and a second light source connected in series to the first light source and connected to a ground line, the lighting circuit comprising a first switch provided between the power supply line and the ground line, a second switch provided between a node of the second light source on the power supply line side and the ground line, and a control circuit that controls the on / off of each of the plurality of switches including the first and second switches to turn on or off each of the first and second light sources. Effect of the Invention

[0007] According to the present invention, it is possible to provide a lighting circuit capable of simultaneously turning off a plurality of light sources. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing an example of a lighting unit 10 mounted on a vehicle 1. [Diagram 2] 1 is a schematic block diagram showing an example of a system configuration of a turn signal lamp 10A. [Diagram 3] 2 is a schematic block diagram showing an example of the configuration of a movable unit 11. FIG. [Figure 4] 1 is a diagram showing a schematic diagram of the connection relationship between light sources 21 to 24 (light emitting elements D1 to D4) and NMOS transistors Q1 to Q4. [Diagram 5] 2 is a schematic block diagram showing an example of the configuration of a lighting circuit 16. FIG. [Figure 6] 4 is a time chart for explaining the operation of the lighting circuit 15. 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 turn signal lamp 10A>> Fig. 1 is a diagram showing an example of a lighting unit 10 mounted on a vehicle 1. Fig. 2 is a schematic block diagram showing an example of a system configuration of a turn signal lamp 10A.

[0011] 1, a fixed part 4 that is a part of the vehicle body and a movable part 3 (a trunk door in this embodiment) that can be opened and closed relative to the fixed part 4 are provided at the rear of the vehicle body. Note that, although the trunk door is used as an example of the movable part 3 here, this is not limiting. For example, in the case of a hatchback type vehicle, the hatchback door corresponds to the movable part 3.

[0012] The lighting unit 10 is a vehicle lamp provided at the rear of the vehicle body of the vehicle 1, and is configured with movable unit units 11, 13 provided on the movable part 3, and fixed unit units 12, 14 provided on the fixed part 4. As shown in FIG. 1, the lighting unit 10 is configured symmetrically with respect to the center of the width direction (left-right direction) of the vehicle 1. Specifically, the movable unit 11 and the fixed unit 12 are provided on the right side of the vehicle 1, and the movable unit 13 and the fixed unit 14 are provided on the left side. The movable unit 11 and the movable unit 13, and the fixed unit 12 and the fixed unit 14 are each arranged symmetrically with respect to the center of the width direction of the vehicle 1. Symmetric In the following description, the right side portion (shown in enlarged form) will be mainly described, but the left side portion has a similar configuration.

[0013] The lighting unit 10 includes a turn signal lamp 10A. The turn signal lamp 10A is a vehicular direction indicator light indicated by diagonal lines in the enlarged view of Fig. 1, and is disposed so as to straddle the fixed part 4 and the movable part 3 of the vehicle 1. The lighting unit 10 also includes a tail lamp, a brake lamp, etc. in addition to the turn signal lamp 10A.

[0014] As shown in FIG. 2, the turn signal lamp 10A includes lighting circuits 15 and 16, a light source 20, and a light source 30.

[0015] The light source 20 is a light source including a light emitting element, and is provided on the movable part 3. In this embodiment, the light source 20 is divided into four light sources (light sources 21 to 24), which are arranged side by side in a substantially horizontal direction (the width direction of the vehicle 1) as shown in FIG.

[0016] 2, the light sources 21 to 24 are connected in series between the terminals E and I of the lighting circuit 15 (in other words, between the power supply line L1 and the ground line L2). A light emitting element is arranged in each light source. Specifically, a light emitting element D1 is arranged in the light source 21, a light emitting element D2 is arranged in the light source 22, a light emitting element D3 is arranged in the light source 23, and a light emitting element D4 is arranged in the light source 24. Since the light sources 21 to 24 are connected in series, the light emitting elements D1 to D4 are also connected in series.

[0017] The configuration of the light sources 21 to 24 is not limited to the above, and each of them may include at least one light emitting element. For example, a plurality of light emitting elements may be connected in series to one light source. Also, a plurality of light emitting elements may be connected in parallel to one light source. Also, the number of light emitting elements and the connection method may differ for each light source. Also, the number of light sources included in the light source 20 is not limited to four, but may be at least two or more. For example, it may be three or five or more. In this embodiment, the light source 21 corresponds to the "first light source", and the light source 24 corresponds to the "second light source". Also, for example, the light source 22 corresponds to the "third light source".

[0018] The light source 30 is a light source that is turned on after the light source 20 is turned on, and is provided on the fixed part 4. The light source 30 has four light-emitting elements (D5 to D8) arranged in series and is connected between the terminals S and T of the lighting circuit 16. The light source 30 is provided in parallel with the light source 20 of the movable part 3. The configuration of the light source 30 is not limited to the one described above, and it is sufficient that the light source 30 includes at least one light-emitting element. In this embodiment, the light source 30 corresponds to a "fourth light source."

[0019] The lighting circuit 15 is applied to a vehicle lamp (lighting unit 10 in this embodiment) and is a circuit for lighting each light-emitting element of the light source 20, and is provided on the movable part 3. The lighting circuit 16 is applied to a vehicle lamp and is a circuit for lighting each light-emitting element of the light source 30, and is provided on the fixed part 4.

[0020] In this embodiment, the lighting circuit 15 and the light source 20 are provided in the movable part 3, but they may be provided in the fixed part 4. Similarly, the lighting circuit 16 and the light source 30 may be provided in the movable part 3. That is, when the lighting circuit 16 and the light source 30 are provided in one of the movable part 3 and the fixed part 4, the lighting circuit 15 and the light source 20 are provided in the other of the movable part 3 and the fixed part 4. The configurations of the lighting circuits 15 and 16 will be described later.

[0021] The lighting circuits 15, 16 of the present embodiment sequentially light the light sources 20 and 30 constituting the turn signal lamp 10A, based on an instruction from an ECU (electronic control unit) (not shown) on the vehicle side.

[0022] A power supply line L0 is also supplied to the lighting circuits 15 and 16. A power supply voltage Vbat of a vehicle battery (not shown) is applied to the power supply line L0 based on instructions from the ECU. The lighting circuits 15 and 16 operate based on the voltage of this power supply line L0. The power supply line L0 is a wiring that supplies power to the internal circuits of the lighting circuits 15 and 16. A line (ground line L2) that sets the internal circuits to the ground level is also supplied to the lighting circuits 15 and 16.

[0023] For example, when the driver of the vehicle 1 operates a turn signal (not shown) to turn on the turn signal lamp 10A of the lighting unit 10, the ECU applies a power supply voltage Vbat to the power supply line L0 at a predetermined period Tx (see FIG. 6). Hereinafter, the voltage applied to the power supply line L0 is referred to as a turn voltage Vt. The turn voltage Vt is a voltage that includes a low level (hereinafter, L level) period during which the power supply voltage Vbat is not applied, and a high level (hereinafter, H level) period during which the power supply voltage Vbat is applied.

[0024] When the level of the turn voltage Vt becomes the H level, the lighting circuits 15 and 16 respectively light the light source 20 (light sources 21 to 24) and the light source 30 at different timings.

[0025] As described later, the lighting circuit 15 transmits a signal S1 indicating that control of lighting of the light source 20 has ended to the lighting circuit 16. Furthermore, if an abnormality (e.g., a disconnection) is detected in the light source 30 (any of the light-emitting elements D5 to D8), the lighting circuit 16 transmits a signal S2 (e.g., L level) indicating that an abnormality exists to the lighting circuit 15. Furthermore, if no abnormality is detected, the lighting circuit 16 transmits a signal S2 (e.g., H level) indicating that the light source 30 is lighting normally to the lighting circuit 15.

[0026] <<Configuration of lighting circuit 15>> Fig. 3 is a schematic block diagram showing an example of the configuration of the lighting circuit 15. Fig. 4 is a diagram showing a schematic connection relationship between the light sources 21-24 (light-emitting elements D1-D4) and the NMOS transistors Q1-Q4. The lighting circuit 15 includes a DC-DC converter 40, a control circuit 41, a disconnection detection circuit 42, gate drive circuits 43a-43d, voltage divider circuits 44-47, NMOS transistors Q1-Q4, and terminals A-H.

[0027] The DC-DC converter 40 is a converter that generates a drive current Iout based on a turn voltage Vt applied to the power supply line L0 and supplies the drive current Iout via the output side power supply line L1 to the light emitting elements of each light source of the light source 20. Note that a step-up / step-down converter is used for the DC-DC converter 40.

[0028] As described above, the light sources 21 to 24 are connected in series between the power supply line L1 and the ground line L2. Therefore, regardless of the number of light sources to be turned on, the drive current Iout supplied by the DC-DC converter 40 is constant (for example, 200 mA). On the other hand, the output voltage Vout changes according to the number of light sources to be turned on. The DC-DC converter 40 of this embodiment is a step-up / step-down converter, and can make the output voltage Vout lower (step-down) or higher (step-up) than the input voltage (power supply voltage Vbat). In this embodiment, the DC-DC converter 40 corresponds to a "step-up / step-down converter." Note that the configuration of a step-up / step-down converter is well known, so a description thereof will be omitted.

[0029] The control circuit 41 is a circuit that controls the operation of the DC-DC converter 40 and controls the on / off of the NMOS transistors Q1 to Q4 to turn on or off each of the light sources 21 to 24. The control circuit 41 includes a timer circuit (not shown) that generates timing for implementing the sequential method. For example, the control circuit 41 includes a circuit (power supply synchronization timer) that controls the timing for operating the DC-DC converter 40 (timing for starting lighting) and a circuit (sequential timer) that sequentially changes the levels of the signals S10 to S13. When the turn voltage Vt becomes H level, the control circuit 41 changes the levels of the signals S10 to S13 at appropriate timings to control the on / off of the NMOS transistors Q1 to Q4 (details will be described later). The control circuit 41 also outputs a signal S1 indicating that the control of the lighting of the light source 20 has ended to the lighting circuit 16 of the fixed unit 4.

[0030] The output terminals of the signals S10 to S13 from the control circuit 41 are open drain outputs, and each signal is in a high impedance state when turning off each of the light sources 21 to 24. On the other hand, when turning on each of the light sources 21 to 24, each signal is set to L level.

[0031] The disconnection detection circuit 42 is a circuit that detects the presence or absence of an abnormality in the light sources 21-24 (here, disconnection of the light emitting elements D1-D4) based on the output voltage Vout. For example, it can be configured with a voltage dividing resistor (not shown) that divides the output voltage Vout of the power supply line L1, and a comparator (not shown) that compares the divided voltage with a reference voltage. When a disconnection occurs, the resistance becomes very high, and the divided voltage also becomes high. Therefore, the presence or absence of a disconnection can be detected by comparing the divided voltage with the reference voltage. When a disconnection is detected, the disconnection detection circuit 42 outputs a signal S3 (for example, at an L level) indicating that there is an abnormality in the light source 20 (any of the light sources 21-24) to the gate drive circuit 43a.

[0032] The gate drive circuit 43a is a circuit that controls the voltage applied to the gate of the NMOS transistor Q1 based on the signals S2, S3, and S10 (in other words, controls the on / off state of the NMOS transistor Q1), and is configured, for example, with a logic circuit that performs logical operations on the signals. This embodiment When either a signal S3 indicating that there is a break in the light source 30 (disconnection in the light emitting elements D1 to D4) or a signal S2 indicating that there is an abnormality in the light source 30 (disconnection in the light emitting elements D5 to D8) is input, the output becomes high impedance and the NMOS transistor Q1 is forcibly turned on regardless of the signal S10. The gate drive circuit 43a corresponds to the "drive circuit".

[0033] Furthermore, the gate drive circuit 43b controls the voltage applied to the gate of the NMOS transistor Q2 based on the signal S11. Similarly, the gate drive circuit 43c controls the voltage applied to the gate of the NMOS transistor Q3 based on the signal S12, and the gate drive circuit 43d controls the voltage applied to the gate of the NMOS transistor Q4 based on the signal S13.

[0034] The voltage dividing circuits 44-47 are circuits for turning on the NMOS transistors Q1-Q4, respectively, when the signals S10-S13 are in a high impedance state. The voltage dividing circuits 44-47 generate divided voltages to turn on the NMOS transistors Q1-Q4, respectively, during the period when the power supply voltage Vbat is applied as the turn voltage Vt.

[0035] Specifically, the voltage dividing circuit 44 includes resistors R11 and R12, the voltage dividing circuit 45 includes resistors R13 and R14, the voltage dividing circuit 46 includes resistors R15 and R16, and the voltage dividing circuit 47 includes resistors R17 and R18. The resistors R11 and R12, the resistors R13 and R14, the resistors R15 and R16, and the resistors R17 and R18 each divide a voltage Vcc (e.g., 10V) generated based on the power supply voltage Vbat during a period in which the power supply voltage Vbat (e.g., 12V) is applied as the turn voltage Vt. At this time, the resistance value of each resistor (resistors R11 to R18) is set so as to generate a divided voltage that turns on each of the NMOS transistors Q1 to Q4.

[0036] The NMOS transistors Q1 to Q4 have a function of switching on and off in response to a voltage applied to their gates. In this embodiment, the NMOS transistors Q1 to Q4 are elements that control the lighting or extinguishing of the light sources 21 to 24. Furthermore, the NMOS transistor Q1 in this embodiment also has a function of turning off all of the light sources 21 to 24.

[0037] The NMOS transistor Q1 is provided between a node N1 of the power supply line L1 between the DC-DC converter 40 and the light emitting element D1, and a ground line L2. The NMOS transistor Q2 is provided between a node N2 of the power supply line L1 between the light emitting elements D1 and D2, and a ground line L2. The NMOS transistor Q3 is provided between a node N3 of the power supply line L1 between the light emitting elements D2 and D3, and a ground line L2. L2 The NMOS transistor Q4 is provided between a node N4 of the power supply line L1 between the light emitting elements D3 and D4 and the ground line L2.

[0038] The NMOS transistor Q1 corresponds to a "first switch", and the NMOS transistor Q4 corresponds to a "second switch". For example, the NMOS transistor Q2 corresponds to a "third switch". The node N4 corresponds to a "node on the power line side of the second light source", and the node N2 corresponds to a "node on the ground side of the first light source".

[0039] <<Configuration of lighting circuit 16>> 5 is a schematic block diagram showing an example of the configuration of the lighting circuit 16. The lighting circuit 16 includes a DC-DC converter 60, a control circuit 61, a disconnection detection circuit 62, and terminals P to T.

[0040] The DC-DC converter 60 is a converter that supplies a drive current to the light emitting elements D5 to D8 of the light source 30 based on the turn voltage Vt applied to the power supply line L0. The DC-DC converter 60 may be a step-up converter or a step-down converter.

[0041] The control circuit 61 is a circuit that controls the operation of the DC-DC converter 60. 15 When the control circuit 61 receives the signal S1 from the power supply 62, the control circuit 61 operates the DC-DC converter 60.

[0042] The disconnection detection circuit 62 is a circuit similar to the disconnection detection circuit 42, and detects an abnormality of the light source 30 (light-emitting elements D5 to D8 When the output voltage of the DC-DC converter 60 becomes higher than a predetermined level, it detects that any of the light emitting elements D5 to D8 is disconnected. This detection result is sent to the lighting circuit 15 as a signal S2 indicating that there is an abnormality in the light source 30.

[0043] <<Operation of lighting circuit 15>> 6 is a time chart for explaining the operation of the lighting circuit 15. In addition, in the signals S10 to S13, the hatched portions indicate high impedance.

[0044] For example, when a turn indicator (not shown) is operated to flash a turn signal lamp, a turn voltage Vt that changes between 0 V and a power supply voltage Vbat at a predetermined period Tx (e.g., 700 ms) is generated and applied to the power supply line L0.

[0045] In the cycle Tx, the period during which the turn voltage Vt is 0V and the period of the power supply voltage Vbat are each half the cycle Tx (350 ms). As a result, the power supply voltage Vbat is applied to the power supply line L0 for half the cycle Tx. In addition, since the DC-DC converter 40 supplies a constant drive current Iout to the light sources 21-24, the output voltage Vout is depicted as increasing in a stepped manner as the light sources 21-24 are sequentially turned on.

[0046] First, at time t0, the turn voltage Vt becomes H level (power supply voltage Vbat), which starts up the DC-DC converter 40 of the lighting circuit 15, and the light source 20 becomes capable of being supplied with the driving current Iout.

[0047] When the turn voltage Vt becomes H level, the control circuit 41 of the lighting circuit 15 puts the signals S10 to S13 into a high impedance state, and then starts sequential lighting operation. When the signal S10 is in a high impedance state, the output of the gate drive circuit 43a also becomes high impedance. Similarly, when the signals S11 to S13 are in a high impedance state, the output of the gate drive circuits 43b to 43d also becomes high impedance. At this time, each of the voltage divider circuits 44 to 47 generates a divided voltage to turn on each of the NMOS transistors Q1 to Q4, so that each of the voltages Vg1 to Vg4 becomes a voltage (H level) that turns on each of the NMOS transistors Q1 to Q4. As a result, the NMOS transistors Q1 to Q4 are turned on, and the light sources 21 to 24 are turned off.

[0048] After that, at time t1, the control circuit 41 sets the output of the signal S10 to the L level. This causes the output of the gate drive circuit 43a to become the L level, and the divided voltage of the voltage divider circuit 44 and the voltage Vg1 also become the L level. Therefore, the NMOS transistor Q1 turns off and the light source 21 turns on. At this time, the NMOS transistors Q2 to Q4 are on, and the light sources 22 to 24 remain off.

[0049] Furthermore, at time t2, a predetermined time after time t1, the control circuit 41 sets the output of the signal S11 to L level. As a result, the output of the gate drive circuit 43b becomes L level, and the divided voltage of the voltage divider circuit 45 and the voltage Vg2 become L level. Therefore, the NMOS transistor Q2 turns off and the light source 22 turns on. In this embodiment, until the light source 22 turns on, the DC-DC converter 40 steps down the turn voltage Vt (power supply voltage Vbat) and outputs the output voltage Vout according to the light sources 21 and 22.

[0050] Furthermore, at time t3, a predetermined time after time t2, the control circuit 41 sets the output of the signal S12 to L level. As a result, the output of the gate drive circuit 43c becomes L level, and the divided voltage of the voltage divider circuit 46 and the voltage Vg3 become L level. Therefore, the NMOS transistor Q3 turns off and the light source 23 lights up. At this time, the DC-DC converter 40 boosts the turn voltage Vt (power supply voltage Vbat) and outputs the output voltage Vout according to the light sources 21 to 23.

[0051] At time t4, which is a predetermined time after time t3, the control circuit 41 sets the output of the signal S13 to the L level. As a result, the output of the gate drive circuit 43d becomes the L level, and the voltage divider circuit 47 The divided voltage and the voltage Vg4 go to the L level, so that the NMOS transistor Q4 turns off and the light source 24 turns on.

[0052] Although not shown in the figure, the control circuit 41 outputs a signal S1 indicating that control of the lighting of the light source 20 has ended to the lighting circuit 16 after setting the output of the signal S13 to an L level. Upon receiving the signal S1, the control circuit 61 of the lighting circuit 16 operates the DC-DC converter 60 at a predetermined time after time t4 to supply a drive current to the light source 30. As a result, all of the light sources 20 (light sources 21 to 24) and 30 are lit.

[0053] Then, at time t5, the turn voltage Vt becomes the L level (0 V), and the outputs of the DC-DC converters 40 and 60 also become 0 V. 24 ) and all of the light sources 30 are turned off. Then, when the turn voltage Vt becomes the H level at time t6, the same operation as that from time t0 onwards is repeated.

[0054] If the disconnection detection circuit 42 detects that one of the light sources 21-24 is disconnected at times t1-t4, the disconnection detection circuit 42 outputs a signal S3 indicating an abnormality to the gate drive circuit 43a. When the gate drive circuit 43a receives the signal S3 indicating an abnormality, it outputs high impedance regardless of the level of the signal S10. Therefore, the divided voltage of the voltage divider circuit 44 is applied to the gate of the NMOS transistor Q1, and the NMOS transistor Q1 is turned on. As a result, the drive current Iout does not flow to each light source (light sources 21-24) of the light source 20, and each light source of the light source 20 is turned off all at once.

[0055] Furthermore, when a signal S2 indicating an abnormality in the light source 30 is received from the lighting circuit 16, the gate drive circuit 43a outputs a high impedance regardless of the signal S10. In this case as well, the NMOS transistor Q1 is turned on, so that the light sources 20 are simultaneously turned off.

[0056] In this manner, in this embodiment, all the light sources (light sources 21 to 24) of the light source 20 can be turned off simultaneously by simply turning on the NMOS transistor Q1, and there is no discrepancy in the timing of turning off the light sources 21 to 24 compared to the case where each of the light sources 21 to 24 is turned off individually.

[0057] If the DC-DC converter 40 is a boost converter, it cannot step down the voltage, so the potential on the most downstream side of the path of the drive current Iout in the light source 20 (here, the cathode side of the light-emitting element D4 of the light source 24) is applied to the positive input of the DC-DC converter 40. In this way, even when there are only a few light sources to be turned on, the DC-DC converter 40 can step up the voltage based on the potential on the cathode side of the light-emitting element D4 and output an appropriate output voltage Vout. However, in this case, since the potential on the cathode side of the light-emitting element D4 of the light source 24 is not the ground potential, it is difficult to design a lighting circuit to control the turning on and off of the light sources 21 to 24.

[0058] For example, if an NMOS transistor is provided in parallel with each light source, the threshold voltage for turning on the NMOS transistor becomes high. In particular, if an NMOS transistor is provided in parallel with each of a number of light sources connected in series, control is difficult because the threshold voltages of the NMOS transistors are different. For this reason, PMOS transistors are used as the transistors connected in parallel to the light sources. However, with PMOS transistors, the number of components in the control circuit increases, and the NMOS transistors become more expensive. S Circuit design becomes more difficult than in the case of transistors.

[0059] In contrast, in this embodiment, since the DC-DC converter 40 is step-up / step-down compatible, the potential on the most downstream side of the current path in the light source 20 (here, the cathode side of the light emitting element D4 of the light source 24) can be set to the ground potential. This allows the NMOS transistors Q1 to Q4 to be used as transistors that turn on or off each light source (light sources 21 to 24). In addition, in this embodiment, the source of each of the NMOS transistors Q1 to Q4 is grounded, and they are not connected in parallel to the light sources 21 to 24. Therefore, in this embodiment, the NMOS transistors Q1 to Q4 can be controlled to be turned on and off with the same voltage, making it easier to design the lighting circuit 15. Also, as described above, the light sources 21 to 24 can be turned off all at once by simply turning on the NMOS transistor Q1 on the most upstream side in the path of the drive current Iout. Therefore, in the lighting circuit 15, a circuit for turning off the light sources 21 to 24 all at once can be easily designed.

[0060] ===== Variations ===== In the above embodiment, the light sources 21 to 24 are turned on in sequence, but this is not limited to the above. For example, the NMOS transistors may be turned on in the order of Q4, Q3, Q2, and Q1 from a state in which the light sources 21 to 24 are all turned on by turning off all the NMOS transistors. In this case, the light sources 21 to 24 are turned off in sequence from a state in which they are all turned on.

[0061] In addition, the DC-DC converter 40 in the above embodiment is a step-up / step-down converter, but is not limited to this. For example, a step-up converter and a step-down converter may be combined. In this case, the turn voltage Vt is stepped up by the step-up converter, and then stepped down by the step-down converter, so that an appropriate output voltage Vout can be applied to the light source 20.

[0062] In addition, in the above-described embodiment, the multiple light sources are arranged across the movable part 3 and the fixed part 4 of the vehicle 1, but this is not limited thereto. For example, multiple light sources (and lighting circuits) may be arranged on either the movable part 3 or the fixed part 4 and turned on in a sequential manner.

[0063] =====Summary===== The lighting circuit 15 of this embodiment has been described above. The lighting circuit 15 is a lighting circuit applied to the lighting unit 10 having the light source 20 including the light source 21 connected to the power supply line L1 and the light source 24 connected in series to the light source 21 and connected to the ground line L2, and includes an NMOS transistor Q1 provided between the power supply line L1 and the ground line L2, an NMOS transistor Q4 provided between the node N4 on the power supply line L1 side of the light source 24 and the ground line L2, and a control circuit 41 that controls the on / off of each of a plurality of NMOS transistors including the NMOS transistors Q1 and Q4 to turn on or off each of the light source 21 and the light source 24. As a result, by turning on the NMOS transistor Q1, all the light sources (light sources 21 to 24) can be turned off at the same time.

[0064] Also, an NMOS transistor Q2 is provided between a node N2 on the ground side of the light source 21 and a ground line L2, the light source 20 includes a light source 22 provided between the node N2 and the light source 24, the above-mentioned multiple NMOS transistors include NMOS transistors Q1, Q2, Q4, and the control circuit 41 controls the on / off of each of the NMOS transistors Q1, Q2, Q4 to turn on or off each of the light sources 21, 22, 24. This makes it possible to control the on / off of each of the light sources even when there are three or more light sources, and also to turn off all the light sources at once.

[0065] Moreover, the control circuit 41 turns off the NMOS transistor Q1, and then controls the on / off of the NMOS transistors Q2 to Q4 so that the light sources 21 to 24 included in the light source 20 are turned on in sequence. This makes it possible to turn on the light sources 21 to 24 in sequence in a sequential manner.

[0066] In addition, the control circuit 41 controls the on / off of each of the multiple NMOS transistors so that the light sources 21 to 24 are turned off in sequence, and then turns on the NMOS transistor Q1. This makes it possible to turn off the light sources 21 to 24 in sequence from a state in which all of them are turned on.

[0067] Furthermore, the DC-DC converter 40 that supplies the drive current Iout to the light sources 21-24 is a step-up / step-down converter, and the switches that turn on or off the light sources 21-24 are each composed of NMOS transistors Q1-Q4. As a result, the DC-DC converter 40 is capable of step-up and step-down, and can output an appropriate output voltage Vout according to the number of light sources to be turned on. Furthermore, since the NMOS transistors Q1-Q4 are used as switches, the circuit configuration is simpler than when PMOS transistors are used.

[0068] Also included is a gate drive circuit 43a that turns on the NMOS transistor Q1 based on a signal S3 that indicates that an abnormality has occurred in any of the light sources 21 to 24. This makes it possible to simultaneously turn off all of the light sources when an abnormality occurs in any of the light sources 21 to 24.

[0069] Gate drive circuit 43 a turns on the NMOS transistor Q1 based on a signal S2 indicating that there is an abnormality in the light source 30 provided in the fixed part 4 of the vehicle 1, and the light sources 21 to 24 are provided in the movable part 3 which can be opened and closed with respect to the fixed part 4. In this way, when there is an abnormality in the light source 30 of the fixed part 4, all the light sources of the movable part 3 can be turned off all at once.

[0070] 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]

[0071] 1 vehicle 3 Moving parts 4 Fixed part 10 Lighting Unit 10A turn signal lamp 11,13 Movable unit 12,14 Fixed unit 15,16 Lighting circuit 20 light source 21~24 Light source 30 light source 40,60 DC-DC converter 41,61 Control circuit 42,62 Open circuit detection circuit 43a~43d Gate drive circuit D1 to D8 Light emitting elements Q1~Q4 NMOS transistors R11~R18 Resistor Vt Turn voltage L0,L1 power lines L2 Ground line

Claims

1. A lighting circuit applied to a vehicle lamp having a plurality of light sources including a first light source connected to a power supply line and a second light source connected in series to the first light source and connected to a ground line, a first switch provided between the power supply line and the ground line; a second switch provided between a node on the power supply line side of the second light source and the ground line; a control circuit that turns on or off each of the first and second light sources by controlling on / off of each of a plurality of switches including the first and second switches; a step-up / step-down converter for supplying a drive current to the plurality of light sources; Each of the plurality of switches is an NMOS transistor. Lighting circuit.

2. A lighting circuit applied to a vehicle lamp having a plurality of light sources including a first light source connected to a power line and a second light source connected in series to the first light source and connected to a ground line, a first switch provided between the power supply line and the ground line; a second switch provided between a node on the power supply line side of the second light source and the ground line; a control circuit that turns on or off each of the first and second light sources by controlling on / off of each of a plurality of switches including the first and second switches; a drive circuit that turns on the first switch based on a signal indicating that any one of the plurality of light sources has an abnormality; A lighting circuit comprising:

3. 3. The lighting circuit according to claim 2, The drive circuit includes: turning on the first switch based on a signal indicating that there is an abnormality in a fourth light source provided on one of a fixed portion of a vehicle and a movable portion that is openable and closable relative to the fixed portion; The plurality of light sources are provided on the other of the fixed portion and the movable portion. Lighting circuit.

4. The lighting circuit according to claim 2 or 3, a step-up / step-down converter for supplying a drive current to the plurality of light sources; Each of the plurality of switches is an NMOS transistor. Lighting circuit.

5. The lighting circuit according to any one of claims 1 to 4, a third switch provided between a node on a ground side of the first light source and the ground line; the plurality of light sources includes a third light source provided between a node on a ground side of the first light source and the second light source, the plurality of switches include the first to third switches, The control circuit controls the on / off of each of the plurality of switches to turn on or off each of the first to third light sources. Lighting circuit.

6. The lighting circuit according to any one of claims 1 to 5, the control circuit turns off the first switch, and then controls on / off of a switch other than the first switch among the plurality of switches so that the plurality of light sources are turned on in sequence; Lighting circuit.

7. The lighting circuit according to any one of claims 1 to 5, the control circuit controls the on / off of each of the plurality of switches so that the plurality of light sources that are turned on are sequentially turned off, and then turns on the first switch. Lighting circuit.

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