Light source driving circuit and vehicle lighting fixture

Abstract

To further reduce the lower limit operating voltage of a bypass circuit that operates when a current path including a plurality of light-emitting elements is broken.SOLUTION: A drive circuit for lighting a light source having at least a plurality of light-emitting elements connected in series includes a driver that supplies a drive current to a light source, a bypass circuit connected in parallel to a first circuit that is a part of the plurality of light-emitting elements, and a resistive element connected in parallel to a second circuit that is another part of the plurality of light-emitting elements.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a drive circuit for a light source and a vehicle lamp. [Background technology]

[0002] International Publication No. 2021 / 187260 (Patent Document 1) describes a light source module comprising an LED string including four LEDs (light-emitting diodes) connected in series, an LED driver circuit that receives a battery voltage and supplies a drive current stabilized to a target current to the LED string, and a bypass circuit that is arranged in parallel with a bypassed portion including two adjacent LEDs of the LED string and sinks a bypass current corresponding to the battery voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 187260 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of a specific embodiment of the present disclosure is to provide a technique capable of further reducing the lower limit voltage of a bypass circuit that operates when a current path including a plurality of light-emitting elements is disconnected. [Means for solving the problem]

[0005] (1) A driving circuit according to one embodiment of the present disclosure A drive circuit for lighting a light source including at least a plurality of light emitting elements connected in series, A driver that supplies a drive current to the light source; a bypass circuit connected in parallel to a first circuit that is a part of the plurality of light emitting elements; a resistive element connected in parallel to a second circuit that is another part of the plurality of light emitting elements; A drive circuit including: (2) A lighting fixture according to one aspect of the present disclosure includes: The drive circuit according to (1), a light source including at least a plurality of light emitting elements connected in series and driven by the drive circuit; It is a lighting fixture including.

[0006] In this disclosure, "a state in which component A is connected to component B" includes not only a case in which component A and component B are directly physically connected to each other, but also a case in which component A and component B are indirectly connected to each other via other components that do not substantially affect the electrical connection state between them or that do not impair the function or effect achieved by their combination.

[0007] According to the above configuration, it is possible to further reduce the lower limit voltage of the bypass circuit that operates when a current path including a plurality of light emitting elements is broken. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a circuit diagram of a vehicle lamp according to an embodiment. [Diagram 2] FIG. 2 is a diagram for explaining a circuit operation under normal circumstances. [Diagram 3] FIG. 3 is a diagram for explaining a circuit operation in an abnormal state. [Figure 4] FIG. 4 is a circuit diagram of a vehicle lamp of a comparative example. [Diagram 5] FIG. 5 is a circuit diagram of a vehicle lamp according to a modified embodiment. [Figure 6] FIG. 6 is a circuit diagram of a vehicle lamp according to a modified example. [Figure 7] FIG. 7 is a circuit diagram of a vehicle lamp according to a modified example. [Figure 8] FIG. 8 is a diagram showing another example of the configuration of the bypass circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 1 is a circuit diagram of a vehicle lamp according to an embodiment. The vehicle lamp 100 shown in the figure is mounted on, for example, a two-wheeled vehicle and used as a headlamp. The vehicle lamp 100 operates by receiving power from a battery (power source) 40 mounted on the two-wheeled vehicle, and includes a plurality of light-emitting elements 1, 2, and 3, a driver 10, a bypass circuit 11, a dimmer switch 12, a resistive element 13, and a diode 14. In this embodiment, the light-emitting elements 1, 2, and 3 correspond to a "light source," and the driver 10, the bypass circuit 11, the dimmer switch 12, and the resistive element 13 correspond to a "drive circuit."

[0010] The light-emitting elements 1, 2, and 3 are each a semiconductor light-emitting element such as an LED (Light-Emitting Diode). The light-emitting elements 1, 2, and 3 are connected in series. In this embodiment, a first circuit including the light-emitting elements 1 and 2 is used for emitting a low beam (Lo), and a second circuit including the light-emitting element 3 is used for emitting a high beam (Hi). The light-emitting elements 1, 2, and 3 form a lamp unit, and the lamp unit is installed at a predetermined position in the front of the two-wheeled vehicle.

[0011] The anode of the light-emitting element 1 is connected to the high-voltage terminal of the driver 10, and the cathode is connected to the anode of the light-emitting element 2. The anode of the light-emitting element 2 is connected to the cathode of the light-emitting element 1, and the cathode is connected to the anode of the light-emitting element 3. The anode of the light-emitting element 3 is connected to the cathode of the light-emitting element 2, and the cathode is connected to the low-voltage terminal of the driver 10.

[0012] The driver 10 is, for example, a step-down DC-DC converter, and generates a voltage for driving the light-emitting elements 1 to 3 using a voltage supplied from a battery 40 via a diode 14. A high-voltage side terminal (high potential end) of the driver 10 is connected to the anode of the light-emitting element 1, and a low-voltage side terminal (low potential end) of the driver 10 is connected to the cathode of the light-emitting element 3.

[0013] The bypass circuit 11 is connected between the connection point between the high-voltage terminal of the driver 10 and the anode of the light-emitting element 1, and the dimmer switch 12. The bypass circuit 11 is a circuit for diverting the current flowing from the driver 10 so as to supply it to the light-emitting element 3 when a break occurs in the light-emitting elements 1 and 2 or in a current path (e.g., wiring) including these elements. The bypass circuit 11 is configured to include a thyristor 21, a Zener diode 22, resistors 23 and 24, and a diode 25.

[0014] The thyristor 21 has an anode connected to the high-voltage terminal of the driver 10 and the anode of the light-emitting element 1, and a cathode connected to the dimmer switch 12. In addition, the gate of the thyristor 21 is connected to the connection point between the resistor element 23 and the resistor element 24.

[0015] The diode 25, the Zener diode 22, and the resistance elements 23 and 24 are connected in series in this order, and are connected in parallel as a whole to the thyristor 21. Specifically, the diode 25 is provided to prevent reverse connection, and has an anode connected to the anode of the light-emitting element 1 and the driver 10, and a cathode connected to the cathode of the Zener diode 22.

[0016] The Zener diode 22 has a cathode connected to the cathode of the diode 25, and an anode connected to one end of the resistor element 23. The resistor element 23 has one end connected to the anode of the Zener diode 22, and the other end connected to one end of the resistor element 24. The resistor element 24 has one end connected to the other end of the resistor element 23, and the other end connected to the cathode of the thyristor 21 and the dimmer switch 12. The Zener diode 22 and the resistor elements 23 and 24 correspond to the "operating voltage setting circuit." The diode 25 is not an essential element, and the bypass circuit 11 will operate without any problems even if the diode 25 is omitted.

[0017] The dimmer switch 12 is connected between the bypass circuit 11 and the light-emitting element 3, and between the bypass circuit 11 and the driver 10. This dimmer switch 12 is a mechanical switch for selecting whether to emit only a low beam or both a low beam and a high beam from the light source, and is installed, for example, on a steering wheel operated by the driver.

[0018] The resistive element 13 is connected in parallel with the light-emitting element 3. In detail, one end of the resistive element 13 is connected to the anode of the light-emitting element 3 and the dimmer switch 12, and the other end is connected to the cathode of the light-emitting element 3 and the reference potential side terminal. The diode 14 is connected between the battery 40 and the driver 10.

[0019] FIG. 2 is a diagram for explaining the circuit operation in a normal state. The normal state here refers to a state in which no break occurs in the light-emitting elements 1 and 2 or in the current path (for example, wiring) including these elements, and the bypass circuit 11 is not operating. When low beam and high beam irradiation are selected in the dimmer switch 12, the dimmer switch 12 switches to the side indicated as "Hi" in the figure. In this case, the connection point between the light-emitting element 2 and the light-emitting element 3 (the connection point between the first circuit and the second circuit) is connected to the bypass circuit 11 (second state). Since the wiring in parallel with the light-emitting element 3 and the resistance element 13 inside the dimmer switch 12 is not conductive, all of the light-emitting elements 1, 2, and 3 are turned on. The current path in this case is indicated by a thick dotted line in the figure.

[0020] Furthermore, when only low beam irradiation is selected in the dimmer switch 12, the dimmer switch 12 switches to the side indicated by "Lo" in the figure. In this case, the connection point between the light-emitting element 2 and the light-emitting element 3 (the connection point between the first circuit and the second circuit) is connected to the other end of the resistance element 13 (first state). The wiring in parallel with the light-emitting element 3 and the resistance element 13 inside the dimmer switch 12 is conductive, resulting in a state in which substantially no current flows to the light-emitting element 3, etc., so that the light-emitting elements 1 and 2 are turned on and the light-emitting element 3 is turned off.

[0021] FIG. 3 is a diagram for explaining the circuit operation in an abnormal state. The abnormal state here refers to a state in which a break occurs in the light-emitting elements 1 and 2 or in a current path including these (for example, wiring), and the bypass circuit 11 is operating. In this case, the low beam is not irradiated, but the dimmer switch 12 selects the irradiation of the low beam and the high beam, so that the irradiation of the high beam is maintained. Specifically, the dimmer switch 12 is switched to the side indicated as "Hi" in the figure, and the wiring in parallel with the light-emitting element 3 and the resistance element 13 inside the dimmer switch 12 becomes non-conductive, so that the current path of the light-emitting elements 1 and 2 is bypassed by the bypass circuit 11, and only the light-emitting element 3 is turned on. The current path in this case is indicated by a thick dotted line in the figure. The operation of the bypass circuit 11 in this case will be described in detail below.

[0022] When a break occurs in the light-emitting elements 1 and 2 or in the current path including these, immediately after that, a current flows from the driver 10 to the dimmer switch 12 through the diode 25, the Zener diode 22, the resistor element 23, and the resistor element 24 as shown by the dotted line A in Fig. 3. After that, when the potential generated at the connection point between the resistor element 23 and the resistor element 24 exceeds the threshold voltage of the thyristor 21, a current flows into the gate of the thyristor 21 connected to this connection point, and when the potential exceeds the gate trigger voltage (for example, about 1.0 V), the thyristor 21 turns on (conducts) and maintains this state. As a result, a current flows from the driver 10 to the dimmer switch 12 through the thyristor 21 as shown by the dotted line B in Fig. 3. In both the current paths of the dotted lines A and B, the current path after the dimmer switch 12 is the same, and the current flows into the light-emitting element 3 and the resistor element 13.

[0023] In the bypass circuit 11, the constants of the Zener diode 22, the resistor elements 23, 24, and the resistor element 13 are set so that the operating voltage of the thyristor 21 is higher than the forward voltage Vf of each of the light-emitting elements 1 and 2 in a steady state without a break. The Zener voltage of the Zener diode 22 can be, for example, about 6.8 V. In addition, in the event of a break, each constant is set so that the operating voltage of the thyristor 21 is as low as possible while satisfying the operating conditions in the steady state described above. Considering that the threshold voltage of the thyristor 21 also varies, it is preferable to set each resistance value so that the resistance values ​​of the resistor elements 13 and 23 are smaller than the resistance value of the resistor element 24, as the magnitude relationship of each resistance element. However, if the resistor element 13 is too small, the current flowing through the resistor element 13 will be larger than the current flowing through the light-emitting element 3, so it is preferable to set the resistance value of the resistor element 13 as large as possible while satisfying the above conditions.

[0024] During operation of the bypass circuit 11, the voltage generated across the parallel circuit of the light-emitting element 3 and the resistor element 13 is equal to the voltage generated by current flowing through the resistor element 13. By using a resistor element 13 having a resistance value sufficiently higher than the impedance of the light-emitting element 3 while it is turned on, almost no current flows through the resistor element 13 while the light-emitting element 3 is turned on, and a sufficient amount of light can be obtained from the light-emitting element 3. Specifically, the voltage generated across the parallel circuit of the light-emitting element 3 and the resistor element 13 can be about 0.1 to 0.3 V, depending on the conditions of the circuit elements. Therefore, the lower limit voltage of the operation when the thyristor 21 of the bypass circuit 11 is turned on through the current path indicated by the dotted line A described above can be reduced.

[0025] In contrast, in the case where there is no resistive element 13 connected in parallel to the light-emitting element 3, as in the comparative vehicle lamp 1000 shown in Fig. 4, the voltage generated across the light-emitting element 3 depends on the forward voltage Vf of the light-emitting element, and is, for example, 2 to 3 V. For this reason, the lower limit operating voltage when the thyristor 21 of the bypass circuit 11 is turned on via the current path indicated by the dotted line A becomes relatively high.

[0026] For example, if the lower limit operating voltage in the comparative example shown in Fig. 4 is 11.0V, in this embodiment, it is possible to lower the lower limit operating voltage to about 9.5V, although this depends on the conditions of the circuit elements. When the normal battery voltage of the battery 40 is 12.0V, the lower limit operating voltage in the comparative example has a small margin, and there is a possibility that the bypass circuit 11 will not be able to achieve the intended operation when the battery 40 deteriorates. In contrast, in this embodiment, the lower limit operating voltage is lowered, thereby expanding the margin.

[0027] As described above, according to this embodiment, it is possible to further reduce the lower limit voltage of the bypass circuit that operates when a current path including a plurality of light emitting elements is broken.

[0028] The present disclosure is not limited to the contents of the above-mentioned embodiment, and various modifications can be made within the scope of the gist of the present disclosure. For example, as in a modified vehicular lamp 100a shown in FIG. 5, the connection relationship of each of the light emitting elements 1, 2, 3, the bypass circuit 11, the dimmer switch 12, and the resistive element 13 to the driver 10 may be reversed. Specifically, in the modified vehicular lamp 100a, the light emitting element 3 is connected to the high-voltage terminal of the driver 10, and the light emitting elements 1 and 2 are connected to the low-voltage terminal. The resistive element 13 is connected in parallel to the light emitting element 3. The dimmer switch 12 has one end connected to the high-voltage terminal of the driver 10 and the other end connected to the bypass circuit 11. The bypass circuit 11 has one end connected to the dimmer switch 12 and the other end connected to the low-voltage terminal of the driver 10.

[0029] The circuit operation of the vehicle lamp 100a is basically the same as that of the vehicle lamp 100 of the embodiment described above. That is, in a normal state where there is no break in the current path including the light-emitting elements 1 and 2, the bypass circuit 11 does not operate, and a current flows from the driver 10 to the light-emitting elements 1, 2, and 3, and the light-emitting elements 1, 2, and 3 are turned on. Also, when the dimmer switch 12 is on the Lo side, only the light-emitting elements 1 and 2 are turned on. Also, when there is a break in the current path including the light-emitting elements 1 and 2, a current flows to the bypass circuit 11 via the light-emitting element 3 and the resistor element 13, and the thyristor 21 is turned on, bypassing the light-emitting elements 1 and 2, and a current flows to the driver 10 via the light-emitting element 3, the resistor element 13, the dimmer switch 12, and the bypass circuit 11. As a result, the light-emitting element 3 is kept turned on.

[0030] Also, for example, a two-pole dimmer switch 12b may be used as in a modified vehicle lamp 100b shown in FIG. 6. Specifically, the configuration of the vehicle lamp 100b shown in FIG. 6 is basically the same as that of the vehicle lamp 100 of the above-mentioned embodiment, and is different in that the three-pole dimmer switch 12 in the vehicle lamp 100 is replaced with a two-pole dimmer switch 12b. In the vehicle lamp 100b having this configuration, when the dimmer switch 12b is off (non-conductive state), the light-emitting element 3 and the resistor element 13 are not short-circuited between one end and the other end (second state), so that a current flows through the light-emitting element 3 and the resistor element 13. When the dimmer switch 12b is on (conductive state), the light-emitting element 3 and the resistor element 13 are short-circuited between one end and the other end (first state), so that a current does not substantially flow through the light-emitting element 3 and the resistor element 13. This allows the vehicle lamp 100b to achieve the same operation as the vehicle lamp 100 of the above embodiment. Such a two-pole dimmer switch 12b can also be applied to the vehicle lamp 100a of the above modification (not shown). The dimmer switch 12b can also be replaced with an electronic switch element such as a bipolar transistor or a field effect transistor.

[0031] Moreover, the specific configuration of the bypass circuit 11 in the above-mentioned embodiment and each modified example is an example, and the configuration of the bypass circuit 11 is not limited to the above-mentioned content as long as the same function can be realized. Furthermore, the dimmer switch 12 (or 12b) can be omitted. Specifically, for example, as in the modified example shown in FIG. 7, the bypass circuit 11 can be expressed as a functional block. Furthermore, the dimmer switch 12 (or 12b) can be omitted. In the modified vehicle lamp 100c shown in FIG. 7, when no break occurs in the current path including the light-emitting elements 1 and 2, the bypass circuit 11 does not divert the current, and the current flows through each of the light-emitting elements 1, 2, and 3, and the current flows through the resistor element 13. When a break occurs, the current path of the light-emitting elements 1 and 2 is diverted by the bypass circuit 11, and the current flows through the light-emitting element 3 and the resistor element 13. In a configuration in which the dimmer switch 12 etc. is omitted as shown in FIG. 7, the light-emitting element 3 cannot be switched on and off arbitrarily. However, this can be used as a configuration that allows other light-emitting elements to continue to be lit even if part of the current path of a light-emitting element is broken, for example, in cases where the light-emitting elements 1, 2, and 3 are used to achieve a low beam (or high beam) function rather than the high beam and low beam functions described above, or in cases where the light-emitting elements are used for purposes other than vehicle applications.

[0032] FIG. 8 is a diagram showing another example of the configuration of the bypass circuit. The bypass circuit 11a of the example configuration shown in FIG. 8 includes a disconnection detection circuit 50, a latch circuit (holding circuit) 60, and a bypass element 70. The disconnection detection circuit 50 is a circuit for detecting a disconnection in a current path including the light-emitting elements 1 and 2, and is connected in parallel to the current path including the light-emitting elements 1 and 2. The latch circuit 51 is a circuit for holding a state in which a disconnection is detected by the disconnection detection circuit 50. The bypass element 70 is an element for passing a current to the light-emitting element 3 by bypassing the current path of the light-emitting elements 1 and 2 when a disconnection is detected by the disconnection detection circuit 50 and the state is held by the latch circuit 51. The power supply voltage of the latch circuit 60 may be a battery voltage or an anode voltage of the light-emitting element 1, as long as the voltage can be held when the bypass element 70 is in a conductive state.

[0033] The disconnection detection circuit 50 includes a Zener diode 51, a resistor element 52, and a bipolar transistor (NPN transistor) 53. The Zener diode 51 has a cathode connected to the anode of the light-emitting element 1, and an anode connected to the resistor element 52. The resistor element 52 has one end connected to the Zener diode 51 and the other end connected to the light-emitting element 2. The Zener diode 51 and the resistor element 52 are connected in series, and the whole is connected in parallel to the light-emitting elements 1 and 2. The bipolar transistor 53 has a base connected to the connection point between the Zener diode 51 and the resistor element 52, an emitter connected to the other end of the resistor element 52, and a collector connected to the connection point between the resistor element 64 and the resistor element 65 of the latch circuit 60.

[0034] The latch circuit 60 includes a bipolar transistor (PNP transistor) 61, resistor elements 62, 63, 64, 65, and a bipolar transistor (NPN transistor) 66. The bipolar transistor 61 has a base connected to a connection point between the resistor elements 64 and 65, an anode of the light-emitting element 1 and a cathode and an emitter of the Zener diode 51 connected, and a collector connected to one end of the resistor element 62. The resistor element 62 has one end connected to the collector of the bipolar transistor 61 and the other end connected to one end of the resistor element 63. The resistor element 63 has one end connected to the other end of the resistor element 62 and the other end connected to a reference potential terminal. The resistor element 62 and the resistor element 63 are connected in series. The resistor element 64 has one end connected to the anode of the light-emitting element 1 and the cathode of the Zener diode 51, and the other end connected to one end of the resistor element 65. One end of the resistor element 65 is connected to the other end of the resistor element 64, and the other end is connected to the collector of the bipolar transistor 66. The resistor elements 64 and 65 are connected in series. The bipolar transistor 66 has a base connected to the connection point between the resistor elements 62 and 63, a collector connected to the other end of the resistor element 65, and an emitter connected to the reference potential terminal.

[0035] The bypass element 70 is, for example, a field effect transistor (PMOSFET), with its gate connected to the connection point between the resistor element 65 and the collector of the bipolar transistor 66 of the latch circuit 60, its drain connected to the anode of the light emitting element 1 and the cathode of the Zener diode 51, and its source connected to the other end of the light emitting element 2 and the other end of the resistor element 52. This bypass element 70 is on (conductive state) while the latch circuit 60 is holding its state. Thereby, when a break occurs in the current path of the light emitting elements 1 and 2, a current can flow by bypassing this current path.

[0036] Furthermore, in the above embodiment and modified example, the number of resistive elements connected in parallel to light-emitting element 3, which is a light-emitting element that maintains its illumination even when a current path related to light-emitting elements 1 and 2 is broken, may not be one, but may be multiple. Also, a series connection of a resistive element and a diode or a transistor may be connected in parallel to light-emitting element 3. Also, the number of light-emitting elements that maintain their illumination even when a current path related to light-emitting elements 1 and 2 is broken may be multiple. Similarly, the number of light-emitting elements used for low beam irradiation may be more than two, or may be one.

[0037] In addition, in the above-described embodiment, a headlamp is used as an example of a lamp for use in a two-wheeled vehicle, but the scope of application of the present disclosure is not limited thereto. The present disclosure may be used in various lamps such as headlamps and rear lamps in other vehicles such as four-wheeled vehicles, or as a lamp for lighting the interior of a vehicle. Furthermore, the present disclosure may be used not only for vehicle applications, but also as a lamp for lighting inside a building.

[0038] The present disclosure has the following features. (Appendix 1) A drive circuit for lighting a light source including at least a plurality of light emitting elements connected in series, A driver that supplies a drive current to the light source; a bypass circuit connected in parallel to a first circuit that is a part of the plurality of light emitting elements; a resistive element connected in parallel to a second circuit that is another part of the plurality of light emitting elements; A drive circuit including: (Appendix 2) a switch connected to one end and the other end of the resistor element and to the bypass circuit, the switch being configured to be able to switch between a first state in which a connection point between the first circuit and the second circuit is connected to the other end of the resistor element and a second state in which the connection point is connected to the bypass circuit; 2. The drive circuit of claim 1, further comprising: (Appendix 3) a switch connected to the second circuit in a switchable manner between a first state in which one end and the other end of the second circuit are short-circuited and a second state in which one end and the other end of the second circuit are not short-circuited; 2. The drive circuit of claim 1, further comprising: (Appendix 4) The switch is a mechanical switch. 4. A drive circuit as described in claim 3. (Appendix 5) The switch is an electronic switch element. 4. A drive circuit as described in claim 3. (Appendix 6) The first circuit is connected to a high potential end of the driver, and the second circuit is connected to a low potential end of the driver. 6. The drive circuit according to claim 1. (Appendix 7) The first circuit is connected to a low potential end of the driver, and the second circuit is connected to a high potential end of the driver. 6. The drive circuit according to claim 1. (Appendix 8) the bypass circuit operates such that, when the first circuit is in a non-conductive state, a current flows from the driver to the second circuit, bypassing the first circuit. 8. The drive circuit according to claim 1. (Appendix 9) When both the first circuit and the second circuit are in a conductive state, When the switch is in the first state, the light-emitting element of the first circuit is turned on and the light-emitting element of the second circuit is turned off; When the switch is in the second state, the light-emitting element of the first circuit and the light-emitting element of the second circuit are both turned on. 4. The drive circuit according to claim 2 or 3. (Appendix 10) The number of the light-emitting elements included in the first circuit is relatively greater than the number of the light-emitting elements included in the second circuit. 10. The drive circuit according to any one of claims 1 to 9. (Appendix 11) The bypass circuit includes: a disconnection detection circuit connected in parallel with the first circuit; a holding circuit that holds a state in response to detection of a disconnection by the disconnection detection circuit; a bypass element that causes a current to flow to the second circuit by bypassing the first circuit when the state is being held by the holding circuit; 11. The drive circuit according to any one of claims 1 to 10, comprising: (Appendix 12) The bypass circuit includes: a thyristor having an anode connected to a high potential end of the driver and a cathode connected to the switch; an operating voltage setting circuit including a Zener diode and supplying an operating voltage to the gate of the thyristor; 11. The drive circuit according to any one of claims 1 to 10, comprising: (Appendix 13) A drive circuit according to any one of claims 1 to 12; a light source including at least a plurality of light emitting elements connected in series and driven by the drive circuit; Including lighting fixtures. (Appendix 14) The lamp is a vehicle lamp used in a two-wheeled vehicle. 13. A lamp as described in Appendix 13. [Explanation of symbols]

[0039] 1, 2, 3: light emitting element, 11: bypass circuit, 12: dimmer switch, 13, 23, 24: resistive element, 21: thyristor, 22: Zener diode, 25: diode, 50: battery, 100, 100a: vehicle lamp

Claims

1. A drive circuit for lighting a light source including at least a plurality of light emitting elements connected in series, a driver that supplies a drive current to the light source, a bypass circuit connected in parallel to a first circuit that is a part of the plurality of light emitting elements, a resistance element connected in parallel to a second circuit that is another part of the plurality of light emitting elements, The drive circuit including these.

2. A switch that is connected to one end and the other end of the resistance element and is connected to the bypass circuit, and is configured to be able to switch between a first state in which a connection point between the first circuit and the second circuit is connected to the other end of the resistance element and a second state in which the connection point is connected to the bypass circuit, The drive circuit according to claim 1, further including this.

3. A switch connected to the second circuit so as to be able to switch between a first state in which one end and the other end of the second circuit are short-circuited and a second state in which one end and the other end of the second circuit are not short-circuited, The drive circuit according to claim 1, further including this.

4. The drive circuit according to claim 3, wherein the switch is a mechanical switch. The drive circuit according to claim 3.

5. The drive circuit according to claim 3, wherein the switch is an electronic switch element. The drive circuit according to claim 3.

6. The drive circuit according to claim 1, wherein the first circuit is connected to the high potential end of the driver and the second circuit is connected to the low potential end of the driver. The drive circuit according to claim 1.

7. The drive circuit according to claim 1, wherein the first circuit is connected to the low potential end of the driver and the second circuit is connected to the high potential end of the driver. The drive circuit according to claim 1.

8. The drive circuit according to claim 1, wherein the bypass circuit operates so that when the first circuit becomes non-conductive, current flows from the driver to the second circuit bypassing the first circuit. The drive circuit according to claim 1.

9. When both the first circuit and the second circuit are in a conductive state, when the switch is in the first state, the light emitting elements of the first circuit are lit and the light emitting elements of the second circuit are extinguished, when the switch is in the second state, the light emitting elements of the first circuit and the light emitting elements of the second circuit are both lit, The drive circuit according to claim 2 or 3.

10. The drive circuit according to claim 1, wherein the number of light emitting elements included in the first circuit is relatively larger than the number of light emitting elements included in the second circuit. The drive circuit according to claim 1.

11. The bypass circuit, a disconnection detection circuit connected in parallel with the first circuit, A holding circuit that performs state holding in response to detection of a disconnection by the disconnection detection circuit; A bypass element that bypasses the first circuit and allows current to flow to the second circuit when the state holding by the holding circuit is being performed; The drive circuit according to claim 1, comprising:

12. The bypass circuit includes: A thyristor having an anode connected to the high potential end of the driver and a cathode connected to the switch; A Zener diode, and an operating voltage setting circuit that applies an operating voltage to the gate of the thyristor; The drive circuit according to claim 1, comprising:

13. The drive circuit according to claim 1; A light source including at least a plurality of light emitting elements connected in series and driven by the drive circuit; A lighting fixture comprising:

14. The lighting fixture according to claim 14, wherein the lighting fixture is a vehicle lighting fixture used for a two-wheeled vehicle. The lighting fixture according to claim 13.

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