Lighting control device, lighting device, and vehicle lamp

Abstract

To prevent a light source from being damaged due to flow of an excessive current caused by a load fluctuation when lighting control is performed on a plurality of light sources by a common lighting control device.SOLUTION: A lighting control device 4 for controlling the lighting of a first light source and a second light source having a smaller load than the first light source includes a voltage supply circuit for supplying a drive voltage to each of the first and second light sources, a smoothing capacitor for absorbing ripples in a drive voltage to be supplied from the voltage supply circuit, a first switching element for controlling the flow of current generated by the drive voltage to the first light source, a second switching element for controlling the flow of current generated by the drive voltage to the second light source, a control circuit 12 for outputting a control signal for controlling the first and second switching elements, and a bypass circuit 5 for forming a bypass path for bypassing the current flowing to the second light source. The bypass circuit 5 is set to a conducted state based on a control signal for reducing a load among the control signals to be output from the control circuit 12, thereby forming the bypass path.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention 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 configured by connecting light emitting elements such as LEDs in series, a driving voltage is supplied to the light emitting elements by a voltage supply circuit such as a DC / DC converter. Here, a protection circuit is provided in the voltage supply circuit in order to protect the light emitting elements so that a voltage exceeding the rating is not applied to the light emitting elements.

[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 GND wiring of the input protection circuit, and when a voltage higher than a specified value is applied between the positive terminal and the GND terminal, or when a surge voltage is applied, it absorbs the voltage so that the LEDs can be prevented from being damaged.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] With 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 selectively irradiate light by individually controlling these plurality of light sources according to each function. In this case, in order to realize 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, the number of voltage supply circuits required is equal to the number of functions, resulting in a complicated configuration and an increase in cost. Therefore, a common lighting control device is provided for a plurality of light sources according to the function, and a switching circuit is provided to selectively switch the connection between each of the plurality of light sources and the voltage supply circuit, so that these plurality of light sources emit light according to each function. With such a configuration, the number of voltage supply circuits can be reduced, and complication of the configuration and cost increase can be avoided.

[0006] FIG. 6(a) shows a vehicle lamp 1 including, as an example of the vehicle lamp, 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 low beam light source 3 has fewer light emitting elements than 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 that is a voltage supply circuit for supplying a driving 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 that are switching elements, and capacitors 15 and 16 that are smoothing capacitors for absorbing the ripple generated in the driving voltage supplied from the voltage supply circuit.

[0007] The step-down DC-DC converter 11 receives voltage supply from a power source (not shown), generates a driving voltage, and supplies a driving current 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 by applying this driving voltage to the light emitting elements 21, 22, and 31.

[0008] The control circuit 12 is connected to the control terminals (bases) of the transistors 13 and 14, and controls the conduction state (conduction / cutoff) of the current paths (between the collector and emitter) of the transistors 13 and 14 by supplying control signals to the respective control terminals.

[0009] The control circuit 12 controls the conduction states of the transistors 13 and 14 so as to selectively turn on the high-beam light source 2 and the low-beam light source 3. When selecting the high-beam light source 2, the control circuit 12 outputs a control signal to the control terminal so as to turn on the transistor 13. At this time, since the low-beam light source 3 is not selected, the transistor 14 is controlled to be in a non-conductive state.

[0010] When the transistor 13 is turned on, the driving voltage is applied from the step-down DC-DC converter 11 to the light-emitting elements 21 and 22 of the high-beam light source 2, and a driving current is supplied to the light-emitting elements 21 and 22. At this time, a DC voltage is input from the step-down DC-DC converter 11 to the capacitor 15 connected between the positive electrode wiring 17 and the GND wiring 18, and charges are stored. The capacitor 15 has a capacitance for suppressing the ripple, which is a voltage fluctuation corresponding to the switching of the transistors 13 and 14, which are switching elements, and smoothing the output voltage.

[0011] FIG. 6(b) shows a current curve a at the 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 a current curve b at the 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.

[0012] When the transistor 13 is turned on (ON state), the current value at the connection point A rapidly increases, and a constant driving current, which is the rated current value of the light-emitting elements 21 and 22, is supplied, so that the high-beam light source 2 is turned on. At this time, the transistor 14 is in a non-conductive state (OFF state), and the current value at the connection point B is 0.

[0013] Next, when changing the function from high beam to low beam, the control circuit 12 turns off the transistor 13 to turn off the high-beam light source 2, and turns on the transistor 14 to turn on the low-beam light source 3.

[0014] In FIG. 6(b), when the transistor 13 is turned off (in the OFF state), the current value at the connection point A drops rapidly to zero. In contrast, the current value at the connection point B rises rapidly when the transistor 14 is turned on (in the ON state).

[0015] Here, since the high-beam light source 2 connected to the connection point A has a configuration 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 is 2Vf. In contrast, since the low-beam light source 3 connected to the connection point B is composed of only the light-emitting element 31, the forward voltage of the low-beam light source 3 is Vf, and the load is smaller than that of the high-beam light source 2.

[0016] Therefore, when the transistor 13 is turned off (in the OFF state) and the transistor 14 is turned on (in the ON state), the load decreases. When the load decreases, the charge stored in the capacitor 15 is discharged.

[0017] When the capacitor 15 discharges, a voltage discharged from the capacitor 15 is instantaneously applied to 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. Therefore, a surge current due to the discharge of the capacitor 15 occurs in the current flowing through the connection point B at the rising edge. Since such a surge current is a current value that greatly exceeds the rated current value of the light-emitting element 31, an excessive current flows through the light-emitting element 31, and the light-emitting element 31 may be damaged.

[0018] The present invention has been made in view of the above, and an object thereof is to prevent an excessive current from flowing through a light source due to a load fluctuation and damaging the light source when controlling the lighting of a plurality of light sources by a common lighting control device.

Means for Solving the Problems

[0019] The lighting control device according to the present invention is a lighting control device that controls the lighting of a first light source and a second light source having a smaller load than the first light source. For each of the first light source and the second light source, a voltage supply circuit that supplies a driving voltage, a smoothing capacitor that absorbs the ripple of the driving voltage supplied from the voltage supply circuit, a first switching element that controls the flow of the current generated by the driving voltage to the first light source, a second switching element that controls the flow of the current generated by the driving 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 through the second light source. Among the control signals output from the control circuit, the bypass circuit is brought into a conductive state based on the control signal for reducing the load, thereby forming the bypass path.

Effects of the Invention

[0020] According to the present invention, when controlling the lighting of a plurality of light sources by a common 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 fluctuation and damaging the light source.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0022] 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.

[0023] (First Embodiment) FIG. 1 is a block diagram showing the configuration of a 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 composed of 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 is 2Vf. Since the low-beam light source 3 is composed of a light-emitting element 31, the forward voltage of the low-beam light source 3 is Vf, and since the number of light-emitting elements is smaller than that of the high-beam light source 2, the load is smaller than that of the high-beam light source 2. Note that the number of light-emitting elements constituting the light source is not limited to this, and the high-beam light source 2 may be a string composed of three or more light-emitting elements, and the low-beam light source 3 may be a string composed of two or more light-emitting elements. If the loads between the light sources are different, the number of light-emitting elements constituting the light source can be set as appropriate. Here, it is assumed that each light-emitting element is the same and the forward voltage is the same, but for example, a combination of light-emitting elements with different emission colors may be used. In this case, each light-emitting element has a different forward voltage, and even if the number of lit lamps is the same, the forward voltages are different and the loads are different.

[0024] The lighting control device 4 includes a step-down DC-DC converter 11 that is 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 that are switching elements, and capacitors 15 and 16 that are smoothing capacitors that absorb the ripple generated in the drive voltage supplied from the voltage supply circuit.

[0025] The step-down DC-DC converter 11 receives a voltage supply from a power source (not shown) to generate a drive voltage, and supplies a drive current 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 by applying this drive voltage to the light-emitting elements 21, 22, and 31. Note that the voltage supply circuit is not limited to a step-down type, and a step-up type may be used.

[0026] The control circuit 12 is connected to the control terminals (bases) of the transistor 13 (first switching element) and the transistor 14 (second switching element), and controls the conduction state (conduction / cutoff) of the current paths (between the collector and emitter) of the transistors 13 and 14 by supplying control signals to the respective control terminals. The control circuit 12 controls the conduction states of the transistors 13 and 14 so as to selectively turn on the high-beam light source 2 and the low-beam light source 3. When selecting the high-beam light source 2, the control circuit 12 outputs a control signal to the control terminal so as to turn the transistor 13 into a conduction state. At this time, since the low-beam light source 3 is not selected, the transistor 14 is controlled to be in a non-conduction state. Note that the transistors 13 and 14 may be field-effect transistors.

[0027] When the transistor 13 is turned into a conduction state, a drive voltage is applied from the step-down DC-DC converter 11 to the light-emitting elements 21 and 22 of the high-beam light source 2, and a drive current is supplied to the light-emitting elements 21 and 22. At this time, a DC voltage is input from the step-down DC-DC converter 11 to the capacitor 15, and charges are stored. The capacitor 15 has a capacitance for suppressing a ripple, which is a voltage fluctuation corresponding to the switching of the transistors 13 and 14 that are switching elements, and smoothing the output voltage.

[0028] In FIG. 1 showing the vehicle lamp of the present embodiment, the difference from FIG. 6 is that a bypass circuit 5 is provided. The bypass circuit 5 is connected between the positive electrode wiring 17 and the GND wiring 18 in parallel with the low beam light source 3 (second light source) and the transistor 14 (second switching element) that turns on / off the low beam light source 3. When the function is switched from high beam to low beam, that is, when the lighting state is switched from the high beam light source 2 to the low beam light source 3 and the load decreases instantaneously, the bypass circuit 5 forms a bypass path for bypassing the current flowing through the low beam light source 3. The surge current generated by the discharge from the capacitor 15, which is a smoothing capacitor, flows through 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 GND wiring 18. Also, a capacitor 52 is connected to the base, which is 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 from the control circuit 12 is input to the control terminal of the transistor 51 via the capacitor 52.

[0029] FIG. 2(a) shows the current curve a at the 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 the 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, in the lighting control device 4 of FIG. 1 according to the present embodiment. The horizontal axis is the time axis, and the vertical axis indicates the current value. Also, FIG. 2(b) 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.

[0030] In Fig. 2(b), when the control signal 121 from the control circuit 12 changes from LOW to HIGH at time t1, the transistor 13 is turned on (conducting state). When the transistor 13 is turned on at time t1, the current value at the connection point A rises rapidly and reaches a certain current value which 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 turned on. During this period, the control signal 122 from the control circuit 12 is maintained in the LOW state. Therefore, the transistor 14 is in the non - conducting state (OFF state), and the current value at the connection point B is 0.

[0031] 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 time t2, turning the transistor 13 into the non - conducting state (OFF state). When the transistor 13 is turned into the non - conducting state, the current value at the connection point A rapidly decreases from the rated current value to 0. As a result, the high beam light source 2 is turned off.

[0032] Also, the control signal 122 of the control circuit 12 changes from LOW to HIGH at time t2, turning the transistor 14 into the 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.

[0033] Therefore, when the transistor 13 is turned into the non - conducting state (OFF state) and the transistor 14 is turned into the conducting state (ON state), the load decreases. When the load decreases, the charge stored in the capacitor 15 is discharged.

[0034] When discharging occurs from the capacitor 15, a voltage discharged from the capacitor 15 is instantaneously applied to 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. Therefore, the current flowing through the connection point B generates a surge current due to the discharge of the capacitor 15 at the rising edge.

[0035] In the present embodiment, a bypass circuit 5 including a transistor 51 and a capacitor 52 that forms a bypass path for bypassing the current flowing through the light-emitting element 31 is provided, and by flowing this surge current through the bypass path, damage to the light-emitting element 31 is prevented.

[0036] The control signal 122 is input to the base of the transistor 51 via the capacitor 52. When the input voltage rises due to a rising signal from LOW to HIGH at the time t2, the charging current to the capacitor 52 flows until the charging is completed. This current flows only for a very short period immediately after the rising edge of the control signal 122 and turns on the transistor 51. When the transistor 51 is turned on, a bypass path is formed between the positive electrode wiring 17 and the GND wiring 18. As a result, the driving current flows through the bypass path. Therefore, although the transistor 14 is in the conductive state, the driving current does not flow to the light-emitting element 31 of the light source 3.

[0037] FIG. 3 shows a waveform diagram in which a current curve c flowing through the path formed by the turn-on of the transistor 51 is added to the current curve a at the connection point A and the current curve b at the connection point B in FIG. 2(a). As shown in the current curve c, when a bypass path is formed by the turn-on of the transistor 51 at the time t2, the surge current due to the discharge of the capacitor 15 flows through the bypass path. Therefore, the surge current does not flow to the light-emitting element 31, and damage to the light-emitting element 31 can be prevented.

[0038] The charging current to the capacitor 52 that starts charging due to the rising edge of the control signal 122 gradually decreases with time, and the transistor 51 is turned off. Current starts to flow through the light-emitting element 31 that has its surge current instantaneously bypassed by the bypass path with a delay from t2. As shown by the current curve b, the current value rapidly rises from the time t3 and reaches the rated current value. As a result, the light-emitting element 31 lights up, and the high beam is switched to the low beam. Since the turn-off of the transistor 51 is automatically performed by charging the capacitor 52, the circuit configuration can be simplified. Also, since the turn-off time can be adjusted according to the capacitance of the capacitor 52, the adjustment can be easily performed.

[0039] (Second Embodiment) Next, FIG. 4 shows the second embodiment. In the first embodiment, the control signal 122 that controls the conduction state of the low beam light source 3 was used for the control of the bypass circuit. However, in the second embodiment, the control signal 121 that controls the conduction state of the high beam light source 2 is used for the control of the bypass circuit.

[0040] In the second embodiment, except for the bypass circuit, it is the same as the first embodiment. Therefore, the same components are denoted by the same reference numerals, and the description thereof is omitted.

[0041] The bypass circuit 6 includes transistors 61 and 64, a capacitor 62, and a resistor 63. The transistor 61 (the third switching element) is connected between the positive electrode wiring 17 and the GND wiring 18. When the transistor 61 is made conductive, a bypass path is formed. One terminal of the capacitor 62 is connected to the control terminal of the transistor 61. Also, a resistor 63 and a transistor 64 (the fourth switching element) are connected in series between the positive electrode wiring 17 and the GND 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 that controls the conduction state of the high beam light source 2 is input to the base.

[0042] Next, the operation of the bypass circuit 6 when switching from high beam to low beam will be described. In the lit 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 is changed from the HIGH state to the LOW state. When the control signal 121 becomes LOW, the transistor 13 is turned off, 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 is changed from the LOW state to the HIGH state, and when the control signal 122 becomes HIGH, the transistor 14 is turned on.

[0043] Also, when the control signal 121 input to the base of the transistor 64 of the bypass circuit 6 becomes LOW, the transistor 64 changes from the conducting state to the non-conducting state. When the transistor 64 is in the conducting state, the capacitor 62 is grounded. From this state, when the transistor 64 is turned off, the capacitor 62 starts charging. When charging starts, the charging current to the capacitor 62 flows until charging is completed. This current flows only for a very short period immediately after the fall of the control signal 121 and turns on the transistor 61. When the transistor 61 is turned on, a bypass path is formed between the positive electrode wiring 17 and the GND wiring 18. As a result, the surge current due to the discharge of the capacitor 15 flows through the bypass path. Therefore, even though the transistor 14 is turned on, the drive current does not flow to the light-emitting element 31 of the light source 3.

[0044] The charging current to the capacitor 62 that started charging when the control signal 121 rose gradually decreases with time, and the transistor 61 is turned off. After the surge current is instantaneously bypassed by the bypass path, current starts to flow through the light-emitting element 31, and the current value rapidly rises to reach the rated current value. As a result, the light-emitting element 31 lights up, and the high beam is switched to the low beam.

[0045] According to the present embodiment, similarly to the first embodiment, it is possible to prevent damage to the light source due to the surge current generated by switching the light sources with different loads.

[0046] (Third Embodiment) Next, FIG. 5 shows the third embodiment. 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, a case where the high-beam light source 2 and the low-beam light source 3 are connected in series will be described.

[0047] In the third embodiment, 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 positive electrode wiring 17 and the GND wiring 18. 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. Also, 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.

[0048] When the transistor 81 is in the non-conductive state, a driving current flows through the light-emitting elements 21 and 22. Also, when the transistor 81 is in the conductive state, a bypass path is formed to bypass the light-emitting elements 21 and 22, and the driving current flows through the bypass path and does not flow through the light-emitting elements 21 and 22. Similarly, when the transistor 82 is in the non-conductive state, a driving current flows through the light-emitting element 31. Also, when the transistor 82 is in the conductive state, a bypass path is formed to bypass the light-emitting element 31, and the driving current flows through the bypass path and does not flow through the light-emitting element 31.

[0049] When turning on the high beam light source 2 and turning off the low beam light source 3, the transistor 81 is turned off so that drive current flows through the light emitting elements 21 and 22, and the transistor 82 is turned on so that no drive current flows through the light emitting element 31. Conversely, when turning off the high beam light source 2 and turning on the low beam light source 3, the transistor 81 is turned on so that no drive current flows through the light emitting elements 21 and 22, and the transistor 82 is turned off so that drive current flows through the light emitting element 31.

[0050] Therefore, when turning off the high beam light source 2 and turning on the low beam light source 3, the control signal 121 input to the base of the transistor 82 is changed from the HIGH state to the LOW state, and the control signal 122 input to the base of the transistor 81 is changed from the LOW state to the HIGH state.

[0051] The bypass circuit 7 includes a transistor 71 (a third switching element) and a capacitor 72. The transistor 71 is connected between the positive electrode wiring 17 and the GND wiring 18, and when the transistor 71 is turned on, a bypass path is formed. One terminal of the capacitor 72 is connected to the base which is the control end of the transistor 71. Also, 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.

[0052] 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 is changed from the LOW state to the HIGH state. When the control signal 122 becomes the HIGH state, the transistor 81 is turned on to form a bypass path, 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 121 is changed from the HIGH state to the LOW state. When the control signal 121 becomes the LOW state, the transistor 82 is turned off and the light-emitting element 31 of the low-beam light source 3 is turned on.

[0053] Also, when the control signal 122 input to the capacitor 72 of the bypass circuit 7 becomes the HIGH state, the capacitor 72 starts charging. When charging starts, the charging current to the capacitor 72 flows until charging is completed. This current flows only for a very short period immediately after the rising edge of the control signal 122 and turns on the transistor 71. When the transistor 71 is turned on, a bypass path is formed between the positive electrode wiring 17 and the GND wiring 18. As a result, the surge current due to the discharge of the capacitor 15 flows through the bypass path. Therefore, even though the light-emitting element 31 has become conductive, the drive current does not flow through the light-emitting element 31.

[0054] The charging current to the capacitor 72 that started charging due to the rising edge of the control signal 122 gradually decreases with time, and the transistor 71 is turned off. After the surge current is instantaneously bypassed by the bypass path, current starts to flow through the light-emitting element 31, and the current value rapidly rises to reach the rated current value. As a result, the light-emitting element 31 lights up and the switch from high beam to low beam is made.

[0055] 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. However, if the configuration of the bypass circuit 7 is the same as that of the bypass circuit 6 in the second embodiment, the control signal 121 for controlling the transistor 82 may be input to the control terminal of a transistor corresponding to the transistor 64 that controls the grounding of the capacitor 72.

[0056] According to this embodiment, similar to the first embodiment, it is possible to prevent damage to the light source due to the surge current generated by switching light sources with different loads.

[0057] In the above embodiment, the high beam and the low beam are exemplified as functions, but the function and the light source used for the function are not limited to this. For example, it may be applied to a turn signal lamp, a position lamp, a daytime running lamp, etc. Also, the number of functions and the light sources used for the functions may be a plurality of three or more.

[0058] In the above embodiment, an example of performing alternative lighting control to turn on one of the high beam and the low beam and turn off the other is described. On the other hand, for example, even in a case where some of a plurality of light sources are turned on and other light sources are turned off, if the load decreases due to the change of the light sources to be turned on and off, the present invention can be applied.

[0059] In the above embodiment, a vehicle lamp is described, but it is not limited to this, and it can also be used for other applications such as amusement equipment as an illumination device.

[0060] The embodiments of the present invention have been described above. However, the scope of the present invention is not limited to the above-described embodiments, and includes the scope of the invention described in the claims and its equivalent scope.

Description of Reference Numerals

[0061] 1…Vehicle lighting fixture, 2…High-beam light source, 3…Low-beam light source, 4…Lamp control device, 5, 6, 7…Bypass circuit, 11…Step-down DC-DC converter, 12…Control circuit, 13, 14, 51, 61, 64, 71, 81, 82…Transistor, 15, 16, 52, 62, 72…Capacitor, 17…Positive electrode wiring, 18…GND wiring, 21, 22, 31…Light-emitting element, 63…Resistor, 121, 122…Control signal, A, B…Connection point, a, b, c…Current curve

Claims

1. A lighting control device that performs lighting control on a first light source and a second light source with a smaller load than the first light source, for each of the first light source and the second light source, a voltage supply circuit that supplies a drive voltage, 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 through the second light source, wherein, among the control signals output from the control circuit, the bypass circuit is brought into a conductive state based on the control signal for reducing the load, thereby forming the bypass path. A lighting control device.

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

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

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

5. The first light source and the second light source are selectively controlled for lighting, 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, The bypass circuit inputs the control signal for controlling the conduction state of the first switching element to the control terminal of the third switching element via the capacitor. The lighting control device according to claim 2.

6. The first light source and the second light source are selectively controlled for lighting, 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, The bypass circuit inputs a signal obtained by inverting the control signal for controlling the conduction state of the second switching element to the control terminal of the third switching element via the capacitor. The lighting control device according to claim 2.

7. A fourth switching element is provided that connects the control terminal of the third switching element to the ground potential via the capacitor, The control signal for controlling the conduction state of the first switching element is input to the control terminal of the fourth switching element. The lighting control device according to claim 4.

8. A fourth switching element is provided that connects the control terminal of the third switching element to the ground potential via the capacitor, The control signal for controlling the conduction state of the second switching element is input to the control terminal of the fourth switching element. The lighting control device according to claim 6.

9. A lighting device including 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 using the lighting device according to claim 9.

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