Lighting device, lighting device driving method, and vehicle lamp

Abstract

To suppress change in color tone of emitted light in a lighting device using a light emitting element.SOLUTION: A lighting device includes at least one first light emitting element, at least one second light emitting element emitting light in a color different from that of the first light emitting element, a power supply circuit connected to the first light emitting element and the second light emitting element and supplying a driving voltage to the first light emitting element and the second light emitting element, and a control circuit that controls the flow of the current generated by the drive voltage to each of the first light emitting element and the second light emitting element, and the control circuit controls the current flow such that a first current flows through the first light emitting element and the second light emitting element is in a non-conducting state during the first period, and controls current flow such that a second current relatively smaller than the first current flows through the first light emitting element and a third current flows through the second light emitting element in a second period following the first period.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a lighting device, a driving method for a lighting device, and a vehicle lamp. [Background technology]

[0002] Japanese Patent No. 6151523 (Patent Document 1) describes a drive circuit that includes a DC-DC converter that applies a DC voltage to a light-emitting section in which multiple semiconductor light-emitting elements are connected in series, and a constant current source that is connected in parallel to at least one of the multiple semiconductor light-emitting elements, and is configured to pass a relatively low idle current through the semiconductor light-emitting element connected in parallel to this constant current source during the period when the constant current source is turned on.

[0003] However, during a period when an idle current is flowing through a portion (at least one) of the multiple semiconductor light-emitting elements, the light color of the semiconductor light-emitting element may fluctuate, and the color of the emitted light from the entire light-emitting unit may also change. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6151523 Summary of the Invention [Problem to be solved by the invention]

[0005] One of the objects of a specific embodiment of the present disclosure is to suppress changes in the color of emitted light from a lighting device or the like that uses a light-emitting element. [Means for solving the problem]

[0006] [1] An illumination device according to one aspect of the present disclosure includes: (a) at least one first light-emitting element; (b) at least one second light-emitting element emitting a different light color from the first light-emitting element; (c) a power supply circuit connected to the first light-emitting element and the second light-emitting element and supplying a drive voltage to the first light-emitting element and the second light-emitting element; and (d) a control circuit controlling a flow of a current generated by the drive voltage to each of the first light-emitting element and the second light-emitting element, wherein (e) the control circuit controls the flow of the current so that, during a first period, a first current flows through the first light-emitting element and the second light-emitting element is in a non-conductive state, and controls the flow of the current so that, during a second period following the first period, a second current relatively smaller than the first current flows through the first light-emitting element and a third current flows through the second light-emitting element. [2] A method for driving a lighting device according to one aspect of the present disclosure includes: (a) driving a lighting device including at least one first light-emitting element and at least one second light-emitting element having a different emission color from the first light-emitting element; a power supply circuit for supplying a driving voltage to the first light emitting element and the second light emitting element, the power supply circuit controlling a flow of a current to the first light emitting element and the second light emitting element, the flow A method for driving a lighting device, comprising: (b) controlling the flow of current so that a first current flows through the first light-emitting element and the second light-emitting element is in a non-conductive state during a first period; and (c) controlling the flow of current so that a second current relatively smaller than the first current flows through the first light-emitting element and a third current flows through the second light-emitting element during a second period following the first period. [3] A vehicle lamp according to one aspect of the present disclosure is a vehicle lamp configured using the lighting device according to [1] above.

[0007] According to the above configuration, it is possible to suppress changes in the color of emitted light in an illumination device or the like that uses a light-emitting element. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a configuration of a vehicle lamp according to an embodiment. [Diagram 2] FIG. 2 is a circuit diagram showing an example of the configuration of each constant current circuit. [Diagram 3]FIG. 3 is a schematic perspective view showing a configuration example of a light emitter including each light emitting element. [Figure 4] FIG. 4 is a waveform diagram for explaining the current flowing through each light-emitting element. [Diagram 5] Fig. 5(A) is a diagram for explaining the circuit operation in a period T1, and Fig. 5(B) is a diagram for explaining the circuit operation in a period T2. [Figure 6] FIG. 6 is a waveform diagram for explaining the current flowing through each light-emitting element. [Figure 7] FIG. 7 shows an example of a circuit configuration in which a plurality of light-emitting elements for correction are connected in parallel. [Figure 8] FIG. 8 shows an example of a circuit configuration in which a plurality of light-emitting elements for correction are connected in series. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 1 is a block diagram showing the configuration of a vehicle lamp according to an embodiment. The vehicle lamp shown in the figure is a type of lighting device, and is mounted on a vehicle for use as, for example, a vehicle width lamp, a daytime running light, etc. This vehicle lamp includes a drive circuit 1 that receives power from a power source 2 such as a vehicle battery and generates a drive voltage, and light-emitting elements 3 and 4 that operate by the drive voltage generated by the drive circuit 1.

[0010] The drive circuit 1 includes a power supply circuit 10, a controller 11, two PWM circuits 12 and 13, and two constant current circuits 14 and 15. The PWM circuits 12 and 13 correspond to a first pulse generating circuit and a second pulse generating circuit, and these circuits and the controller 11 form a pulse signal supply circuit.

[0011] The power supply circuit 10 is connected to each of the light-emitting elements 3, 4, and generates drive voltages for each of the light-emitting elements 3, 4 using the DC voltage supplied from the power supply 2 and supplies the drive voltages to each of the light-emitting elements 3, 4. As this power supply circuit 10, for example, a step-up type, step-down type, or step-up / step-down type DC-DC converter can be used.

[0012] The controller 11 is connected to the power supply circuit 10 and the PWM circuits 12 and 13, operates by receiving a voltage generated by the power supply circuit 10, and controls the operations of the PWM circuits 12 and 13. The controller 11 can be configured using, for example, a microcomputer including a processor or an FPGA.

[0013] The PWM circuit 12 is connected to the power supply circuit 10, the controller 11, and the constant current circuit 14, and generates a pulse signal for switching on and off the constant current generation operation of the constant current circuit 14.

[0014] The PWM circuit 13 is connected to the power supply circuit 10, the controller 11, and the constant current circuit 15, and generates a pulse signal for switching the constant current generation operation of the constant current circuit 15 on and off.

[0015] The constant current circuit 14 is connected to the PWM circuit 12 and connected in parallel to the light-emitting element 4, and operates to switch the constant current generation operation between on (generation) and off (non-generation) in response to the pulse signal supplied from the PWM circuit 12.

[0016] The constant current circuit 15 is connected to the PWM circuit 13 and is connected in series with the light-emitting element 4, and operates such that the constant current generating operation is switched between on (generation) and off (non-generation) in response to the pulse signal supplied from the PWM circuit 13. More specifically, the constant current circuit 15 is connected to one end (cathode) of the light-emitting element 4. The series circuit consisting of the light-emitting element 4 and the constant current circuit 15 is connected in parallel to the light-emitting element 3.

[0017] The light-emitting element 3 is a semiconductor light-emitting element such as an LED (Light Emitting Diode), which is connected to a power supply circuit 10 and operates to emit light by a drive voltage supplied from the power supply circuit 10. In this embodiment, the light-emitting element 3 is a white LED that emits white light, and is configured to include a blue LED and a phosphor that partially converts the light emitted from the blue LED into yellow light, and creates pseudo-white light by mixing the light emitted from the blue LED and the light emitted from the phosphor.

[0018] The light-emitting element 4 is a semiconductor light-emitting element such as an LED (Light Emitting Diode), is connected to a power supply circuit 10, and is operated by a driving voltage supplied from the power supply circuit 10 to emit light. In this embodiment, the light-emitting element 4 emits light of a different color from that of the light-emitting element 3, and is, for example, a blue LED that emits blue light.

[0019] As shown in the figure, the light-emitting element 3 and the light-emitting element 4 are connected in parallel with each other, and one end (anode) of each is connected to the high potential end of the power supply circuit 10. The other end (cathode) of the light-emitting element 3 is connected to the reference potential end (low potential end), and the other end (cathode) of the light-emitting element 4 is connected to the reference potential end via the constant current circuit 15.

[0020] 2 is a circuit diagram showing an example of the configuration of each constant current circuit. The constant current circuit 14 in the illustrated example is configured to include a field effect transistor 20 connected in parallel to the light emitting element 4, a resistive element 21 connected between one of the current input / output terminals (source / drain) of the field effect transistor 20 and a control terminal (gate), and a resistive element 22 connected between the control terminal of the field effect transistor 20 and the PWM circuit 12. In the constant current circuit 14, the on (conducting) and off (non-conducting) of the field effect transistor are controlled in response to a pulse signal (PWM signal) from the PWM circuit 12, and a constant current flows when the constant current circuit 14 is on, and no current flows when the constant current circuit 14 is off.

[0021] The constant current circuit 15 is configured to include a field effect transistor 23 connected in series to the light emitting element 4, a resistive element 24 connected between one of the current input / output terminals (source / drain) of the field effect transistor 23 and a control terminal (gate), and a resistive element 25 connected between the control terminal of the field effect transistor 23 and the PWM circuit 13. In the constant current circuit 15, the on (conducting) and off (non-conducting) of the field effect transistor are controlled in response to a pulse signal (PWM signal) from the PWM circuit 13, so that a constant current flows when the transistor is on, and no current flows when the transistor is off.

[0022] FIG. 3 is a schematic perspective view showing an example of the configuration of a light-emitting body including each light-emitting element. The illustrated light-emitting body includes an acrylic plate (light guide plate) 30, a reflector 31 arranged on one side of the acrylic plate 30, and a diffuser 32 arranged on the other side of the acrylic plate 30. Each light-emitting element 3, 4 is arranged on one of the sides of the acrylic plate 30, and each light-emitting surface is arranged so that light can be emitted into the inside of the acrylic plate 30. Although omitted for convenience of illustration, it is assumed that a reflective film is provided on each side of the acrylic plate 30. The light emitted from each light-emitting element 3, 4 is repeatedly reflected inside the acrylic plate 30, and finally exits from the other side of the acrylic plate 30 through the diffuser 32. At that time, the light emitted from each light-emitting element 3, 4 is mixed through reflection by the reflector 31 and diffusion by the diffuser 32, and the color of the light emitted from the other side of the acrylic plate 30 is a mixed color of the colors of the respective lights. In other words, the light emitted from each of the light emitting elements 3 and 4 can be mixed by appropriate reflecting surfaces or light diffusing surfaces and emitted from the same emission surface.

[0023] As will be described in detail later, when the color of the light emitted from the light-emitting element 3 shifts from the original white color to closer to yellow due to a decrease in the current flowing through the light-emitting element 3, the mixed color can be corrected to approach white by mixing with the blue light emitted from the light-emitting element 4. From this perspective, it is desirable that the emission color of the light-emitting element 4 is a color that is complementary to the color that the emission color of the light-emitting element 3 approaches when it shifts due to a decrease in current. In this embodiment, a light-emitting element that emits blue light that is complementary to the yellow color that the emission color of the light-emitting element 3 approaches when it shifts is used as the light-emitting element 4.

[0024] FIG. 4 is a waveform diagram for explaining the current flowing through each light-emitting element. In the figure, the upper waveform diagram is a waveform diagram of the current I1 flowing through the light-emitting element 3, and the lower waveform diagram is a waveform diagram of the current I2 flowing through the light-emitting element 4. As shown in the figure, in this embodiment, the light-emitting element 3 is driven so that a period T including a period T1 in which a relatively large current flows and a period T2 in which a relatively small current flows is repeatedly generated. The period T is set to a length corresponding to, for example, several tens of hertz to several hundreds of hertz, and the light emitted from the light-emitting element 3 is recognized by the human eye as a light that is substantially continuously turned on. In the example shown in the figure, a case in which the lengths of the periods T1 and T2 are equal (when the duty ratio is 50%) is shown. In this way, by performing driving (i.e., PWM driving) in which the lengths of the periods T1 and T2 are set to be variable, the effective brightness of the light-emitting element 3 can be controlled. However, since the current I1 becomes small in the period T2, the phenomenon occurs in which the light-emitting color of the light-emitting element 3 shifts from white to yellow as described above.

[0025] In contrast, in this embodiment, in period T2 when the current I1 of the light-emitting element 3 is relatively small, a current I2 flows through the light-emitting element 4 to compensate for this. This causes blue light to be emitted from the light-emitting element 4. Then, this blue light from the light-emitting element 4 is mixed with the white light (white light shifted toward yellow) from the light-emitting element 3, so that the mixed color of the composite light can be corrected to approach white.

[0026] 4, the current I2 in the period T1 is 0, but the current I2 in the period T1 may be greater than 0. However, the magnitude of the current I2 is set to be relatively smaller than that in the period T2.

[0027] 5(A) is a diagram for explaining the circuit operation in period T1. In period T1, the constant current circuit 15 is controlled by a pulse signal from the PWM circuit 13 so that at least the constant current circuit 15 is turned off. In this embodiment, the constant current circuit 14 is also controlled by the PWM circuit 12 so that the constant current circuit 14 is turned off. As a result, no current flows through the current path including the light-emitting element 4, and the light-emitting element 4 is in a non-conductive state, so that the entire current I0 generated by the drive voltage of the power supply circuit 10 flows to the light-emitting element 3. As a result, the light-emitting element 3 emits white light.

[0028] 5(B) is a diagram for explaining the circuit operation in period T2. In period T2, the constant current circuits 14, 15 are controlled by pulse signals from the PWM circuits 12, 13 so that both of the constant current circuits 14, 15 are turned on. The total current I0 is divided into current I1 and current I2 at a predetermined ratio according to the current (constant current) flowing through the constant current circuit 15. The light-emitting element 3 is provided with current I1, which is relatively smaller than the total current I0, and emits light according to the magnitude of the current. At this time, the emission color of the light-emitting element 3 shifts due to the decrease in current.

[0029] In addition, the current I2 flowing into the current path including the light emitting element 4 is changed to a current I 2-1 and current I 2-2 The light emitting element 4 is fed with a current I 2-1 flows, and blue light is emitted from the light-emitting element 4 according to its magnitude. As a result, the shifted emission color of the light-emitting element 3 is mixed with the emission color of the light-emitting element 4, and the overall light is corrected to approach white. The degree of color correction is determined by the current I 2-1 The luminance of the light from the light-emitting element 4 can be adjusted by appropriately setting the magnitude of the current I 2-2The current I flows through the light-emitting element 4. 2-1 and the current I flowing through the constant current circuit 14 2-2 The current I2 obtained by rejoining these currents merges with the current I1 flowing through the light-emitting element 3 to become a total current I0, which then flows to the reference potential terminal.

[0030] In the example of the waveform diagram shown in Fig. 4, the periods T1 and T2 have the same length (duty ratio 50%), but the lengths of both periods may be different as shown in Fig. 6. Even in this case, by making the current I2 flow to the light-emitting element 4 in a complementary manner to the current I1 of the light-emitting element 3 in the period T2 when the current I1 is relatively decreased, dimming can be achieved with little change in color (chromaticity) within one cycle T.

[0031] Incidentally, in the past, when the light-emitting element was PWM-controlled, depending on the blinking cycle, the timing of the camera's photography (exposure timing) and the timing of the light-emitting element's turning off may overlap, resulting in the light-emitting element being unable to be photographed in its lit state. In recent years, since images of the vehicle periphery photographed by a camera are used in various controls, it may be inconvenient if the light-emitting element is unable to be photographed in its lit state. In this regard, the vehicle lamp of this embodiment is illuminated at a constant current value even during period T2, and photographed by the camera in a constantly lit state, so that the secondary effect of eliminating the above-mentioned inconvenience can be obtained.

[0032] According to the above-described embodiment, it is possible to suppress changes in the color of emitted light in a vehicle lamp (illumination device) that uses a light-emitting element.

[0033] 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, the circuit configuration of the above-mentioned embodiment is an example and is not limited thereto. For example, a switching element may be connected in parallel to the light-emitting element 4, and the switching element may be switched on (conducting) and off (non-conducting). In addition, although one light-emitting element is used to correct the color of the light-emitting element 3 in the above-mentioned embodiment, multiple light-emitting elements for correction may be provided.

[0034] 7 is a circuit configuration example in the case where a plurality of light-emitting elements for correction are connected in parallel. In the illustrated example, the light-emitting elements 4a, 4b, and 4c for correction are connected in parallel, and the constant current circuits 14a, 14b, and 14c are connected in parallel to each other. The constant current circuit 15 is connected in series to the light-emitting element 4a. Although not illustrated, a PWM circuit for controlling the constant current circuits 14a, 14b, and 14c is also provided, and a pulse signal is given to each of the constant current circuits 14a, etc. In this configuration example, the light-emitting elements 4a, 4b, and 4c may emit light of different colors (e.g., red, green, blue, etc.) or the same color. Furthermore, the light-emitting elements 4a, etc. may emit light at the same or different timings.

[0035] FIG. 8 shows a circuit configuration example in which a plurality of light-emitting elements for correction are connected in series. In the illustrated example, the light-emitting elements 4a, 4b, and 4c for correction are connected in series, and the constant current circuits 14a, 14b, and 14c are connected in parallel to each of them. The constant current circuit 15 is connected in series to the light-emitting element 4c. Although not shown, a PWM circuit for controlling the constant current circuits 14a, 14b, and 14c is also provided, and a pulse signal is given to each of the constant current circuits 14a, etc. In this configuration example, the light-emitting elements 4a, 4b, and 4c may emit light of different colors (e.g., red, green, blue, etc.) or the same color. The light-emitting elements 4a, etc. may emit light at the same or different timings.

[0036] In addition, in the above embodiment, only one each of the light-emitting element 3 and the light-emitting element 4 is shown, but each of the light-emitting element 3 and the light-emitting element 4 may be replaced with a light-emitting element group consisting of a plurality of light-emitting elements. In this case, the light-emitting elements in each light-emitting element group may be connected in series or in parallel.

[0037] Furthermore, in the above embodiment, an LED is given as an example of a light emitting element, but the light emitting element is not limited to this and may be, for example, a laser diode.

[0038] Furthermore, in the above-described embodiment, a vehicle lamp is given as an example of a lighting device, but the contents of the present disclosure can be applied to lighting devices in general. [Explanation of symbols]

[0039] 1: drive circuit, 2: power supply, 3, 4: light emitting element, 10: power supply circuit, 11: controller, 12, 13: PWM circuit, 14, 15: constant current circuit

Claims

1. At least one first light emitting element; At least one second light emitting element having a different emission color from the first light emitting element; a power supply circuit connected to the first light emitting element and the second light emitting element and configured to supply a driving voltage to the first light emitting element and the second light emitting element; a control circuit for controlling a flow of a current generated by the driving voltage to each of the first light emitting element and the second light emitting element; Including, the control circuit controls the flow of current so that a first current flows through the first light-emitting element and the second light-emitting element is in a non-conductive state during a first period, and controls the flow of current so that a second current relatively smaller than the first current flows through the first light-emitting element and a third current flows through the second light-emitting element during a second period following the first period. Lighting equipment.

2. A cycle consisting of the first period and the second period occurs repeatedly, The control circuit controls the flow of the current during each period.

10. The lighting device of claim 1.

3. the first light-emitting element shifts a color of light emitted in the first period so as to approach a specific color in the second period; The second light-emitting element has a color tone of an emitted light that is complementary to the specific color.

3. The lighting device according to claim 1 or 2.

4. The first light emitting element and the second light emitting element are connected in parallel, The control circuit includes: a first constant current source connected in parallel to the second light emitting element; A second constant current source connected in series to the second light emitting element; a pulse signal supply circuit that generates a pulse signal for switching on / off operations of the first constant current source and the second constant current source and supplies the pulse signal to each of the first constant current source and the second constant current source; The lighting device according to claim 1 , further comprising:

5. The pulse signal supply circuit includes: a first pulse generating circuit that supplies the pulse signal to the first constant current source; a second pulse generating circuit that supplies the pulse signal to the second constant current source; The lighting device of claim 4 , comprising:

6. A method for driving a lighting device including at least one first light-emitting element and at least one second light-emitting element having a different emission color from the first light-emitting element, the method comprising controlling a flow of a current to each of the first light-emitting element and the second light-emitting element, the flow being generated by a driving voltage supplied to the first light-emitting element and the second light-emitting element by a power supply circuit, the method comprising: controlling a flow of the current such that a first current flows through the first light emitting element and the second light emitting element is in a non-conducting state during a first period; and controlling the flow of the current so that, in a second period following the first period, a second current relatively smaller than the first current flows through the first light emitting element and a third current flows through the second light emitting element. A method for driving a lighting device.

7. A vehicle lamp comprising the lighting device according to any one of claims 1 to 6.

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