Lighting control device, lighting device, and vehicle lamp

Abstract

The invention provides a lighting control device, a lighting device and a vehicle lamp. The purpose of the present invention is to prevent damage to a plurality of light sources caused by an excessive current flowing due to load fluctuations when lighting control is performed on the plurality of light sources by a common lighting control device. The lighting control device performs lighting control of a first light source and a second light source having a smaller load than the first light source, and includes: a voltage supply circuit that supplies a drive voltage to the first light source and the second light source; a smoothing capacitor that absorbs ripples of the drive voltage supplied from the voltage supply circuit; a first switching element that controls the flow of the current generated by the drive voltage to the first light source; a second switching element that controls the flow of the current generated by the drive voltage to the second light source; a control circuit that outputs a control signal that controls the first switching element and the second switching element; and a bypass circuit that forms a bypass path that bypasses a current flowing to the second light source, and that forms the bypass path by turning the bypass circuit into a conductive state in accordance with a control signal for reducing the load among the control signals.

Description

Technical Field

[0001] The present disclosure relates to a lighting control device, a lighting device, and a vehicle lamp. Background Art

[0002] In a lighting control device for a vehicle lamp, in order to drive a light emitting string formed by connecting light emitting elements such as LEDs in series, a driving voltage is supplied to the light emitting elements through a voltage supply circuit such as a DC / DC converter. Here, in order to protect the light emitting elements from applying a voltage exceeding the rated value, a protection circuit is provided in the voltage supply circuit.

[0003] Patent Document 1 discloses a vehicle lamp in which a plurality of LEDs are connected in parallel to a power supply including an input protection circuit. A Zener diode and a capacitor are connected between the positive wiring and the ground wiring of the input protection circuit, and when a high voltage equal to or higher than a specified value or a surge voltage is applied between the positive terminal and the ground terminal, the voltage is absorbed, and damage to the LEDs can be prevented.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2009-6981 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] Due to the high functionality of vehicle lamps, it is necessary to prepare a plurality of light sources such as a high beam light source and a low beam light source, and these plurality of light sources are individually controlled according to each function to selectively irradiate light. In this case, in order to implement a plurality of functions, a lighting control device is provided for each light source. However, if a lighting control device is provided for each function, a voltage supply circuit corresponding to the number of functions is required, so the structure becomes complicated and the cost increases. Therefore, a common lighting control device is configured for a plurality of light sources corresponding to functions, and a switch circuit is provided to selectively switch the connection of each of the plurality of light sources to the voltage supply circuit, whereby these plurality of light sources emit light according to each function. According to this structure, the number of voltage supply circuits can be reduced, and complication of the structure and cost increase can be avoided.

[0009] Figure 6(a) As an example of the vehicle lamp described above, a vehicle lamp 1 is shown which includes a high-beam light source 2 and a low-beam light source 3, and a lighting control device 4 that controls the lighting of the high-beam light source 2 and the low-beam light source 3. The high-beam light source 2 is a light-emitting string composed of light-emitting elements 21 and 22 connected in series, and the low-beam light source 3 is composed of a light-emitting element 31. Since the number of light-emitting elements of the low-beam light source 3 is smaller than that of the high-beam light source 2, the load is smaller than that of the high-beam light source 2. The lighting control device 4 includes: a step-down DC-DC converter 11 as a voltage supply circuit that supplies a drive voltage to the high-beam light source 2 and the low-beam light source 3; a control circuit 12 that controls the lighting and extinguishing of the high-beam light source 2 and the low-beam light source 3; transistors 13 and 14 as switching elements; and capacitors 15 and 16 as smoothing capacitors that absorb the ripple generated from the drive voltage supplied from the voltage supply circuit.

[0010] The step-down DC-DC converter 11 receives a voltage supply from a power source (not shown) and generates a drive voltage, and applies the drive voltage to each of the light-emitting elements 21, 22, and 31 of the high-beam light source 2 and the low-beam light source 3, thereby supplying a drive current to each of the light-emitting elements 21, 22, and 31.

[0011] The control circuit 12 is connected to the control terminals (bases) of the transistors 13 and 14, and controls the conduction state (on / off) of the current paths (collector-emitter) of the transistors 13 and 14 by supplying control signals to the control terminals.

[0012] The control circuit 12 controls the conduction states of the transistors 13 and 14 so that the high-beam light source 2 and the low-beam light source 3 are selectively lit. When the high-beam light source 2 is selected, the control circuit 12 outputs a control signal to the control terminal so that the transistor 13 becomes conductive. At this time, since the low-beam light source 3 is not selected, the transistor 14 is controlled to be non-conductive.

[0013] When the transistor 13 becomes conductive, the drive voltage is applied to the light-emitting elements 21 and 22 of the high-beam light source 2 from the step-down DC-DC converter 11, and a drive current is supplied to the light-emitting elements 21 and 22. At this time, a DC voltage is input to the capacitor 15 connected between the positive wiring 17 and the ground wiring 18 from the step-down DC-DC converter 11, and the charge is accumulated. The capacitor 15 has a capacitance that suppresses the voltage fluctuation (ripple) corresponding to the switching of the transistors 13 and 14 as switching elements and smoothes the output voltage.

[0014] Figure 6Part (b) shows the current curve a at connection point A, which is the connection point between the positive electrode wiring 17 of the step-down DC-DC converter 11 and the high beam light source 2, and the current curve b at connection point B, which is the connection point between the positive electrode wiring 17 of the step-down DC-DC converter 11 and the low beam light source 3.

[0015] When the transistor 13 becomes conductive (ON state), the current value at connection point A rises sharply, and a fixed drive current, which is the rated current value of the light-emitting elements 21 and 22, is supplied to turn on the high beam light source 2. At this time, the transistor 14 is set to a non-conductive state (OFF state), and the current value at connection point B is 0.

[0016] Next, when changing the function from high beam to low beam, the control circuit 12 turns off the high beam light source 2 by making the transistor 13 non-conductive (OFF state), and turns on the low beam light source 3 by making the transistor 14 conductive (ON state).

[0017] In Figure 6 Part (b), by making the transistor 13 non-conductive (OFF state), the current value at connection point A drops sharply to 0. In contrast, the current value at connection point B rises sharply because the transistor 14 becomes conductive (ON state).

[0018] Here, since the high beam light source 2 connected to connection point A has a structure in which the light-emitting elements 21 and 22 are connected in series, when the forward voltage of the light-emitting element is Vf, the forward voltage of the high beam light source 2 becomes 2Vf. In contrast, since the low beam light source 3 connected to connection point B consists only of the light-emitting element 31, the forward voltage of the low beam light source 3 becomes Vf, and the load is smaller than that of the high beam light source 2.

[0019] Therefore, by making the transistor 13 non-conductive (OFF state) and the transistor 14 conductive (ON state), the load is reduced. By reducing the load, the charge stored in the capacitor 15 is discharged.

[0020] By discharging from the capacitor 15, in addition to the drive voltage from the step-down DC-DC converter 11, a voltage discharged from the capacitor 15 is instantaneously applied to the light-emitting element 31 of the low beam light source 3. Therefore, a surge current caused by the discharge of the capacitor 15 is generated when the current flowing through connection point B rises. This surge current is a current value that greatly exceeds the rated current value of the light-emitting element 31, so an excessive current flows through the light-emitting element 31, and the light-emitting element 31 may be damaged.

[0021] The present invention has been completed in view of the above circumstances, and an object thereof is to prevent an excessive current from flowing through a light source due to a load change when controlling the lighting of a plurality of light sources by a shared lighting control device, thereby damaging the light source.

[0022] Means for Solving the Problem

[0023] The lighting control device of the present invention controls the lighting of a first light source and a second light source having a smaller load than the first light source. The lighting control device includes: a voltage supply circuit that supplies a drive voltage to the first light source and the second light source respectively; a smoothing capacitor that absorbs the ripple of the drive voltage supplied from the voltage supply circuit; a first switching element that controls the flow of the current generated by the drive voltage to the first light source; a second switching element that controls the flow of the current generated by the drive voltage to the second light source; a control circuit that outputs a control signal for controlling the first switching element and the second switching element; and a bypass circuit that forms a bypass path for bypassing the current flowing to the second light source. According to the control signal for reducing the load among the control signals output from the control circuit, the bypass circuit is made conductive, thereby forming the bypass path.

[0024] Advantageous Effects of the Invention

[0025] According to the present invention, when controlling the lighting of a plurality of light sources by a shared lighting control device, by providing a bypass circuit that forms a bypass path, it is possible to prevent an excessive current from flowing through the light source due to a load change, thereby damaging the light source. Description of the Drawings

[0026] Figure 1 It is a block diagram showing the structure of a vehicle lamp according to a first embodiment of the present invention.

[0027] Figure 2 It is a waveform diagram showing the current value input to a light-emitting element during driving. (a) is a waveform diagram showing the current value after removing the surge current through a bypass path, and (b) is a waveform diagram of a control signal for controlling the light emission of the light-emitting element.

[0028] Figure 3 is in Figure 2 The waveform diagram of (a) is a waveform diagram after adding the waveform of the current flowing through the bypass path.

[0029] Figure 4 It is a block diagram showing the structure of a vehicle lamp according to a second embodiment of the present invention.

[0030] Figure 5 It is a block diagram showing the structure of a vehicle lamp according to a third embodiment of the present invention.

[0031] Figure 6 (a) is a block diagram showing the structure of a vehicle lamp of the prior art, and (b) is a waveform diagram showing the current value input to the light-emitting element during driving.

[0032] Description of Reference Numerals

[0033] 1... Vehicle lamp, 2... High-beam light source, 3... Low-beam light source, 4... Lighting control device, 5, 6, 7... Bypass circuits, 11... Step-down DC-DC converter, 12... Control circuit, 13, 14, 51, 61, 64, 71, 81, 82... Transistors, 15, 16, 52, 62, 72... Capacitors, 17... Positive electrode wiring, 18... Ground wiring, 21, 22, 31... Light-emitting elements, 63... Resistor, 121, 122... Control signals, A, B... Connection points, a, b, c... Current curves Detailed Embodiment

[0034] Hereinafter, a vehicle lamp according to an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same or equivalent parts are denoted by the same reference numerals.

[0035] (First Embodiment)

[0036] Figure 1 is a block diagram showing the structure of the vehicle lamp 1. The vehicle lamp 1 includes a high-beam light source 2 (first light source) and a low-beam light source 3 (second light source), and a lighting control device 4 that controls the lighting of the high-beam light source 2 and the low-beam light source 3. The high-beam light source 2 is a light-emitting string formed by light-emitting elements 21 and 22 connected in series. When the forward voltage of the light-emitting element is Vf, the forward voltage of the string becomes 2Vf. Since the low-beam light source 3 is composed of the light-emitting element 31, the forward voltage of the low-beam light source 3 is Vf, and the number of light-emitting elements is smaller than that of the high-beam light source 2, so the load is smaller than that of the high-beam light source 2. In addition, the number of light-emitting elements constituting the light source is not limited to this. The string of the high-beam light source 2 may be composed of three or more light-emitting elements, and the string of the low-beam light source 3 may be composed of two or more light-emitting elements, as long as the loads between the light sources are different, and the number of light-emitting elements constituting the light source can be appropriately set. Here, each light-emitting element is the same and has the same forward voltage, but for example, it may be a combination of light-emitting elements with different emission colors. In this case, each light-emitting element has a different forward voltage, and even if the number of lamps is the same, the forward voltage is different and the load is also different.

[0037] The lighting control device 4 includes: a step-down DC-DC converter 11 as a voltage supply circuit, which supplies a driving voltage to the high-beam light source 2 and the low-beam light source 3; a control circuit 12, which controls the lighting and extinguishing of the high-beam light source 2 and the low-beam light source 3; transistors 13, 14 as switching elements; and capacitors 15, 16 as smoothing capacitors, which absorb the ripple generated from the driving voltage supplied by the voltage supply circuit.

[0038] The step-down DC-DC converter 11 receives a voltage supply from a power source (not shown) to generate a driving voltage, and applies the driving voltage to the respective light-emitting elements 21, 22, 31 of the high-beam light source 2 and the low-beam light source 3, thereby supplying a driving current to the respective light-emitting elements 21, 22, 31. In addition, as the voltage supply circuit, not limited to the step-down type, it may also be a boost type.

[0039] The control circuit 12 is connected to the control terminals (bases) of the transistor 13 (the first switching element) and the transistor 14 (the second switching element), and controls the conduction state (on / off) of the current paths (collector / emitter) of the respective transistors 13, 14 by supplying control signals to the respective control terminals. The control circuit 12 controls the conduction states of the respective transistors 13, 14 in such a way that the high-beam light source 2 and the low-beam light source 3 are selectively lit. When the high-beam light source 2 is selected, the control circuit 12 outputs a control signal to the control terminal to make the transistor 13 in the conduction state. At this time, since the low-beam light source 3 is not selected, it is controlled to make the transistor 14 in the non-conduction state. In addition, the transistors 13, 14 may also be field-effect transistors.

[0040] When the transistor 13 becomes in the conduction state, the driving voltage is applied to the light-emitting elements 21, 22 of the high-beam light source 2 from the step-down DC-DC converter 11, and a driving current is supplied to the light-emitting elements 21, 22. At this time, a DC voltage is input from the step-down DC-DC converter 11 to the capacitor 15, and the charge is accumulated. The capacitor 15 has a capacitance that suppresses the voltage fluctuation (ripple) corresponding to the switching of the transistors 13, 14 as switching elements and smoothes the output voltage.

[0041] In the vehicle lamp showing this embodiment Figure 1 among Figure 6The difference lies in that a bypass circuit 5 is provided. The bypass circuit 5 is connected in parallel between the positive electrode wiring 17 and the ground wiring 18 with the low-beam light source 3 (second light source) and the transistor 14 (second switching element) that turns the low-beam light source 3 on and off. When switching the function from high beam to low beam, that is, at the moment when the lighting state is switched from the high-beam light source 2 to the low-beam light source 3 and the load decreases, the bypass circuit 5 forms a bypass path for bypassing the current flowing to the low-beam light source 3. The surge current generated due to the discharge from the capacitor 15 serving as a smoothing capacitor flows into the bypass path formed by the bypass circuit 5. Specifically, the bypass circuit 5 includes a transistor 51 (third switching element) and a capacitor 52. The collector of the transistor 51 is connected to the positive electrode wiring 17, and the emitter is connected to the ground wiring 18. In addition, the capacitor 52 is connected to the base serving as the control terminal of the transistor 51. The other end of the capacitor 52 is connected to the control circuit 12, and a control signal for controlling the conduction state of the transistor 14 is input from the control circuit 12 to the control terminal of the transistor 51 via the capacitor 52.

[0042] Figure 2 (a) of shows in the lighting control device 4 of the present embodiment Figure 1 the current curve a at the connection point A between the positive electrode wiring 17 of the step-down DC-DC converter 11 and the high-beam light source 2 and the current curve b at the connection point B between the positive electrode wiring 17 of the step-down DC-DC converter 11 and the low-beam light source 3. The horizontal axis is the time axis, and the vertical axis represents the current value. In addition, Figure 2 (b) of is a waveform diagram showing the control signal 121 input from the control circuit 12 to the control terminal of the transistor 13 and the control signal 122 input from the control circuit 12 to the control terminal of the transistor 14.

[0043] In Figure 2 (b) of, when the control signal 121 from the control circuit 12 changes from "low" to "high" at the moment t1, the transistor 13 becomes in a conduction state (ON state). If the transistor 13 becomes in a conduction state (ON state) at the moment t1, the current value at the connection point A rises sharply and reaches a fixed current value that is the rated current value of the light-emitting elements 21 and 22. When the rated current value is reached, this current value is maintained. By supplying the drive current of this rated current value, the high-beam light source 2 is lit. During this period, the control signal 122 from the control circuit 12 is maintained in the "low" state. Therefore, the transistor 14 is set to a non-conduction state (OFF state), and the current value at the connection point B is 0.

[0044] Next, when changing the function from high beam to low beam, the control signal 121 of the control circuit 12 changes from "high" to "low" at the moment t2, making the transistor 13 in a non-conducting state (OFF state). By making the transistor 13 in a non-conducting state, the current value at the connection point A rapidly decreases from the rated current value to 0. Thus, the high-beam light source 2 is extinguished.

[0045] In addition, the control signal 122 of the control circuit 12 changes from "low" to "high" at the moment t2, making the transistor 14 in a conducting state (ON state). Here, as described above, the forward voltage of the high-beam light source 2 connected to the connection point A is 2Vf, while the forward voltage of the low-beam light source 3 connected to the connection point B is Vf, and the load is smaller compared to the high-beam light source 2.

[0046] Therefore, by making the transistor 13 in a non-conducting state (OFF state) and the transistor 14 in a conducting state (ON state), the load is reduced. By reducing the load, the charge stored in the capacitor 15 is discharged.

[0047] By discharging from the capacitor 15, in the light-emitting element 31 of the low-beam light source 3, in addition to the driving voltage from the step-down DC-DC converter 11, a voltage discharged from the capacitor 15 is instantaneously applied. Therefore, a surge current caused by the discharge of the capacitor 15 is generated when the current flowing through the connection point B rises.

[0048] In the present embodiment, by providing the bypass circuit 5, the surge current is made to flow into the bypass path, thereby preventing damage to the light-emitting element 31. The bypass circuit 5 is composed of a transistor 51 and a capacitor 52 that form a bypass path for bypassing the current flowing through the light-emitting element 31.

[0049] The control signal 122 is input to the base of the transistor 51 via the capacitor 52. At the moment t2, when the input voltage rises due to the rising signal from "low" to "high", a charging current flowing into the capacitor 52 flows until the charging is completed. This current flows only during a very short period just after the control signal 122 rises, making the transistor 51 conductive. By making the transistor 51 conductive, a bypass path is formed between the positive electrode wiring 17 and the ground wiring 18. Thus, the drive current flows into the bypass path. Therefore, although the transistor 14 is in a conducting state, the drive current does not flow through the light-emitting element 31 of the light source 3.

[0050] Figure 3 Indicated in Figure 2The waveform diagrams of current curves a at connection point A and current curve b at connection point B in (a) are supplemented with the current curve c flowing through the path formed by the conduction of transistor 51. As shown by the current curve c, at the moment of t2, when the bypass path is formed by the conduction of transistor 51, the surge current caused by the discharge of capacitor 15 flows into the bypass path. Therefore, the surge current does not flow into the light-emitting element 31, and damage to the light-emitting element 31 can be prevented.

[0051] With the rising of the control signal 122, the charging current flowing into the capacitor 52 that has started charging gradually decreases with time, and the transistor 51 is turned off. In the light-emitting element 31 where the surge current is instantaneously bypassed by the bypass path, current starts to flow with a delay from t2. As shown by the current curve b, the current value rapidly rises from the moment of t3 and reaches the rated current value. Thereby, the light-emitting element 31 lights up, and the high beam is switched to the low beam. Since the transistor 51 is automatically turned off by charging the capacitor 52, the circuit structure can be simplified. In addition, the cut-off time can be adjusted by the capacitance of the capacitor 52, so it can be easily adjusted.

[0052] (Second Embodiment)

[0053] Next, Figure 4 The second embodiment is shown. In the first embodiment, the control signal 122 for controlling the conduction state of the low-beam light source 3 is used for the control of the bypass circuit, but in the second embodiment, the control signal 121 for controlling the conduction state of the high-beam light source 2 is used for the control of the bypass circuit.

[0054] Except for the bypass circuit, the second embodiment is the same as the first embodiment. Therefore, the same reference numerals are used for the same structures, and the description is omitted.

[0055] The bypass circuit 6 includes transistors 61, 64, capacitor 62, and resistor 63. The transistor 61 (the third switching element) is connected between the positive electrode wiring 17 and the ground wiring 18. By making the transistor 61 in the conduction state, a bypass path is formed. One terminal of the capacitor 62 is connected to the control terminal of the transistor 61. In addition, a resistor 63 and a transistor 64 (the fourth switching element) are connected in series between the positive electrode wiring 17 and the ground wiring 18, and the other terminal of the capacitor 62 is connected to the connection point between the resistor 63 and the transistor 64. The base, which is the control terminal of the transistor 64, is connected to the control circuit 12, and the control signal 121 for controlling the conduction state of the high-beam light source 2 is input to this base.

[0056] Next, the operation of the bypass circuit 6 when switching from high beam to low beam will be described. In the illuminated state of the high-beam light source 2, the control signal 121 is in the "high" state. When switching from high beam to low beam, the control signal 121 changes from the "high" state to the "low" state. By the control signal 121 becoming the "low" state, the transistor 13 becomes non-conductive, and the light-emitting elements 21 and 22 of the high-beam light source 2 are turned off. At the same time, the control signal 122 changes from the "low" state to the "high" state, and by the control signal 122 becoming the "high" state, the transistor 14 becomes conductive.

[0057] In addition, by the control signal 121 input to the base of the transistor 64 of the bypass circuit 6 becoming the "low" state, the transistor 64 changes from the conductive state to the non-conductive state. When the transistor 64 is in the conductive state, the capacitor 62 is in the grounded state. From this state, the transistor 64 becomes non-conductive, and thus the capacitor 62 starts to charge. When the charging starts, the charging current flowing to the capacitor 62 flows until the charging is completed. This current flows only for a very short period immediately after the control signal 121 drops, turning on the transistor 61. By the transistor 61 being turned on, a bypass path is formed between the positive wiring 17 and the ground wiring 18. Thus, the surge current caused by the discharge of the capacitor 15 flows into the bypass path. Therefore, although the transistor 14 becomes conductive, the drive current does not flow through the light-emitting element 31 of the light source 3.

[0058] By the drop of the control signal 121, the charging current flowing to the capacitor 62 that has started charging gradually decreases with time, and the transistor 61 is cut off. After the surge current is instantaneously bypassed by the bypass path, the current starts to flow through the light-emitting element 31, and the current value rises sharply to reach the rated current value. Thus, the light-emitting element 31 is illuminated, and the switch is made from high beam to low beam.

[0059] According to the present embodiment, as in the first embodiment, it is possible to prevent damage to the light source caused by the surge current generated due to the switching of light sources with different loads.

[0060] (Third Embodiment)

[0061] Next, Figure 5 The third embodiment will be described. In the first and second embodiments, the high-beam light source 2 and the low-beam light source 3 are connected in parallel, but in the third embodiment, the case where the high-beam light source 2 and the low-beam light source 3 are connected in series will be described.

[0062] In the third embodiment, between the positive electrode wiring 17 and the ground wiring 18, the light-emitting elements 21 and 22 of the high-beam light source 2 and the light-emitting element 31 of the low-beam light source 3 are connected in series. Between the anode of the light-emitting element 21 and the cathode of the light-emitting element 22, a transistor 81 (first switching element) is connected in parallel with the light-emitting elements 21 and 22. Further, between the anode and the cathode of the light-emitting element 31, a transistor 82 (second switching element) is connected in parallel with the light-emitting element 31.

[0063] When the transistor 81 is in the non-conducting state, a state is formed in which the drive current flows through the light-emitting elements 21 and 22. Further, by making the transistor 81 in the conducting state, a bypass path for bypassing the light-emitting elements 21 and 22 is formed, and a state is formed in which the drive current flows to the bypass path and does not flow to the light-emitting elements 21 and 22. Similarly, when the transistor 82 is in the non-conducting state, a state is formed in which the drive current flows through the light-emitting element 31. Further, by making the transistor 82 in the conducting state, a bypass path for bypassing the light-emitting element 31 is formed, and a state is formed in which the drive current flows to the bypass path and does not flow to the light-emitting element 31.

[0064] When the high-beam light source 2 is lit and the low-beam light source 3 is extinguished, the transistor 81 is made in the non-conducting state so that the drive current flows through the light-emitting elements 21 and 22, and the transistor 82 is made in the conducting state so that the drive current does not flow through the light-emitting element 31. Conversely, when the high-beam light source 2 is extinguished and the low-beam light source 3 is lit, the transistor 81 is made in the conducting state so that the drive current does not flow through the light-emitting elements 21 and 22, and the transistor 82 is made in the non-conducting state so that the drive current flows through the light-emitting element 31.

[0065] Therefore, when the high-beam light source 2 is extinguished and the low-beam light source 3 is lit, the control signal 121 input to the base of the transistor 82 changes from the "high" state to the "low" state, and the control signal 122 input to the base of the transistor 81 changes from the "low" state to the "high" state.

[0066] The bypass circuit 7 includes a transistor 71 (third switching element) and a capacitor 72. The transistor 71 is connected between the positive electrode wiring 17 and the ground wiring 18, and a bypass path is formed by making the transistor 71 in the conducting state. One terminal of the capacitor 72 is connected to the control terminal, i.e., the base, of the transistor 71. Further, the other terminal of the capacitor 72 is connected to the control circuit 12. The control signal 122 input to the base of the transistor 81 is input to the base of the transistor 71 via the capacitor 72.

[0067] Next, the operation of the bypass circuit 7 when switching from high beam to low beam will be described. When the high-beam light source 2 is in the lit state, the control signal 121 is in the "high" state and the control signal 122 is in the "low" state. When switching from high beam to low beam, the control signal 122 changes from the "low" state to the "high" state. By making the control signal 122 in the "high" state, the transistor 81 becomes conductive to form a bypass path, and the light-emitting elements 21 and 22 of the high-beam light source 2 go out. At the same time, the control signal 121 changes from the "high" state to the "low" state, and when the control signal 121 becomes the "low" state, the transistor 82 becomes non-conductive, and the light-emitting element 31 of the low-beam light source 3 becomes conductive.

[0068] In addition, by making the control signal 122 input to the capacitor 72 of the bypass circuit 7 in the "high" state, the capacitor 72 starts to charge. When the charging starts, the charging current flowing into the capacitor 72 flows until the charging is completed. This current flows only during a very short period just after the control signal 122 rises, making the transistor 71 conductive. By making the transistor 71 conductive, a bypass path is formed between the positive wiring 17 and the ground wiring 18. As a result, the surge current caused by the discharge of the capacitor 15 flows into the bypass path. Therefore, although the light-emitting element 31 becomes conductive, the drive current does not flow through the light-emitting element 31.

[0069] With the rise of the control signal 122, the charging current flowing into the capacitor 72 that has started charging gradually decreases with time, and the transistor 71 is cut off. After the surge current is instantaneously bypassed by the bypass path, the current starts to flow through the light-emitting element 31, and the current value rises sharply to reach the rated current value. Thereby, the light-emitting element 31 lights up, and the switch is made from high beam to low beam.

[0070] In addition, in the above-described embodiment, the control signal 122 for controlling the transistor 81 is input to the control terminal of the transistor 71 of the bypass circuit 7, but the structure of the bypass circuit 7 may be the same as that of the bypass circuit 6 in the second embodiment, and the control signal 121 for controlling the transistor 82 may be input to the control terminal of the transistor corresponding to the transistor 64 that grounds the capacitor 72.

[0071] According to the present embodiment, similarly to the first embodiment, it is possible to prevent damage to the light source caused by the surge current generated due to the switching of light sources with different loads.

[0072] In the above-described embodiment, high beam and low beam are listed as functions, but the functions and the light sources for these functions are not limited thereto. For example, it can also be applied to turn signals, position lights, daytime running lights, etc. In addition, the number of functions and the light sources for these functions can also be more than three.

[0073] In addition, in the above-described embodiment, an example of performing lighting control by alternatively lighting either the high beam or the low beam and extinguishing the other has been described. In contrast, for example, even when several of the plurality of light sources are lit and the other light sources are extinguished, the present invention can be applied as long as the load is reduced by the change in the lit and extinguished light sources.

[0074] In addition, in the above-described embodiment, a vehicle lamp has been described, but it is not limited thereto, and as a lighting device, it can also be used for other purposes such as game devices.

[0075] The present invention can be implemented in various embodiments and variations without departing from the broad spirit and scope of the present invention. In addition, the above-described embodiments are for explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is not represented by the embodiments but by the claims. And various variations implemented within the scope of the claims and the equivalent inventive meaning are regarded as being within the scope of the present invention.

[0076] This application claims priority based on Japanese Patent Application No. 2024-6648 filed on January 19, 2024, and the entire specification, claims, abstract, and drawings of Japanese Patent Application No. 2024-6648 are incorporated herein by reference.

Claims

1. A lighting control device controls the lighting of a first light source and a second light source with a load smaller than the first light source, wherein, The lighting control device has: a voltage supply circuit that supplies drive voltages to the first light source and the second light source respectively; a smoothing capacitor that absorbs the ripple of the drive voltage supplied from the voltage supply circuit; a first switching element that controls the flow of the current generated by the drive voltage to the first light source; a second switching element that controls the flow of the current generated by the drive voltage to the second light source; a control circuit that outputs control signals for controlling the first switching element and the second switching element; and a bypass circuit that forms a bypass path for bypassing the current flowing to the second light source, and makes the bypass circuit in a conductive state according to the control signal for reducing the load in the control signals output from the control circuit, thereby forming the bypass path.

2. The lighting control device according to claim 1, wherein the bypass circuit includes: a third switching element; and a capacitor connected to the control terminal of the third switching element, and inputs the control signal to the control terminal of the third switching element via the capacitor.

3. The lighting control device according to claim 2, wherein the first light source and the second light source are alternately controlled to be lit, the first light source and the second light source are connected in parallel, the first switching element is connected in series with the first light source, the second switching element is connected in series with the second light source, and the bypass circuit inputs the control signal for controlling the on-state of the second switching element to the control terminal of the third switching element via the capacitor.

4. The lighting control device according to claim 2, wherein the first light source and the second light source are alternately controlled to be lit, the first light source and the second light source are connected in parallel, the first switching element is connected in series with the first light source, the second switching element is connected in series with the second light source, and the bypass circuit inputs the signal obtained by inverting the control signal for controlling the on-state of the first switching element to the control terminal of the third switching element via the capacitor.

5. The lighting control device according to claim 2, wherein the first light source and the second light source are alternately controlled to be lit, the first light source and the second light source are connected in series, the first switching element is connected in parallel with the first light source, the second switching element is connected in parallel with the second light source, and the bypass circuit inputs the control signal for controlling the on-state of the first switching element to the control terminal of the third switching element via the capacitor.

6. The lighting control device according to claim 2, wherein the first light source and the second light source are alternately controlled to be lit, the first light source and the second light source are connected in series, the first switching element is connected in parallel with the first light source, the second switching element is connected in parallel with the second light source, and the bypass circuit inputs the signal obtained by inverting the control signal for controlling the on-state of the second switching element to the control terminal of the third switching element via the capacitor.

7. The lighting control device according to claim 4, wherein, the lighting control device includes a fourth switching element that connects the control terminal of the third switching element to the ground potential via the capacitor, and inputs the control signal for controlling the conduction state of the first switching element to the control terminal of the fourth switching element.

8. The lighting control device according to claim 6, wherein, the lighting control device includes a fourth switching element that connects the control terminal of the third switching element to the ground potential via the capacitor, and inputs the control signal for controlling the conduction state of the second switching element to the control terminal of the fourth switching element.

9. A lighting device, wherein, The lighting device includes: the lighting control device according to any one of claims 1 to 8; and the first light source and the second light source.

10. A vehicle lamp configured by using the lighting device according to claim 9.

Images