JP2020021615A - Lighting device and illumination system - Google Patents

Abstract

To suppress variation in chromaticity of light source colors.SOLUTION: A lighting device includes a lighting circuit that supplies a forward current If to a light emitting element through a pair of terminals for an LED having a parasitic capacitance (capacitance) between the pair of terminals. The lighting device includes a control circuit that controls the lighting circuit, alternately switches between a first period T1 for supplying a DC current to the LED and a second period T2 for not supplying the DC current to the LED, and changes the ratio of the first period T1 per unit time to the second period T2. The lighting device includes a forced off circuit that discharges an electric charge stored in the parasitic capacitance without passing through the LED when the lighting circuit is switched from the first period T1 to the second period T2.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lighting device and a lighting system, and more particularly, to a lighting device for lighting a light emitting element having capacitance, and a lighting system including the lighting device.

  As a conventional example, a lighting device described in Patent Document 1 is exemplified. The lighting device described in Patent Document 1 includes a power supply circuit, a plurality of lighting circuits including a red light source lighting circuit, a green light source lighting circuit, and a blue light source lighting circuit, and a control circuit. The red light source lighting circuit lights a light emitting element (red light emitting diode) that emits red light. The green light source lighting circuit lights a light emitting element (green light emitting diode) that emits green light. The blue light source lighting circuit lights a light emitting element (blue light emitting diode) that emits blue light. The control circuit controls the PWM of the red light source lighting circuit, the green light source lighting circuit, and the blue light source lighting circuit, thereby dimming the emission color of the light source unit including the red light source lighting circuit, the green light source lighting circuit, and the blue light source lighting circuit. .

JP 2017-195191 A

  By the way, when the power supply from the lighting circuit to the light emitting element (LED) is turned on / off as in the above-described conventional example, the electric charge stored in the inter-terminal capacitance (parasitic capacitance) of the LED (Light Emitting Diode) is discharged. The current continues to flow to the LED until. On the other hand, the LED has a characteristic that the chromaticity of the light source color changes according to the magnitude of the flowing current. Therefore, when the lighting circuit performs PWM control, when switching from a period in which current is supplied to the LED (on period) to a period in which no current is supplied to the LED (off period), discharge current from the parasitic capacitance of the LED flows. The chromaticity of the light source color changes when the camera is turned on. As a result, it is difficult for the lighting device as in the conventional example to suppress the variation in the chromaticity of the light source color.

  An object of the present invention is to provide a lighting device and a lighting system capable of suppressing variation in chromaticity of a light source color.

  A lighting device according to one embodiment of the present invention includes a lighting circuit that supplies a direct current to the light-emitting element through the pair of terminals with respect to the light-emitting element having capacitance between the pair of terminals. The lighting device controls the lighting circuit, alternately switches a first period in which the DC current is supplied to the light emitting element and a second period in which the DC current is not supplied to the light emitting element, and And a control circuit for changing a ratio between the first period and the second period. The lighting device includes a forced off circuit that discharges the charge stored in the capacitance without passing through the light emitting element when the lighting circuit is switched from the first period to the second period. .

  The lighting system according to one embodiment of the present invention includes the lighting device, one or more light-emitting elements having a capacitance between a pair of terminals, and a DC current supplied from the lighting device through the pair of terminals. Having.

  The lighting device and the lighting system of the present invention have an effect that variation in chromaticity of a light source color can be suppressed.

FIG. 1 is a circuit diagram of a lighting device and a lighting system according to the first embodiment. FIG. 2 is a time chart for explaining the operation of the above lighting device. FIG. 3 is a time chart for explaining the operation of the above lighting device. FIG. 4 is a circuit diagram of a lighting device and a lighting system according to the second embodiment. FIG. 5 is a circuit diagram of a variation of the lighting device and the lighting system of the above. FIG. 6 is a circuit diagram of a lighting device and a lighting system according to the third embodiment. FIG. 7 is a time chart for explaining the operation of the above lighting device.

  A lighting device and a lighting system according to an embodiment will be described in detail with reference to the drawings. However, each drawing described in the following embodiment is a schematic drawing, and the ratio of the size and thickness of each component does not necessarily reflect the actual dimensional ratio. Note that the configurations described in the following embodiments are merely examples of the present invention. The present invention is not limited to the following embodiments, and various changes can be made according to the design and the like as long as the effects of the present invention can be achieved.

(Embodiment 1)
The lighting device 1 according to the first embodiment includes a lighting circuit 2, a control circuit 3, and a forced off circuit 4, as shown in FIG. The lighting system 6 according to the first embodiment includes the lighting device 1 and the LEDs 5 that are light-emitting elements.

  The LED 5 is, for example, a white LED for illumination. However, the light source color of the LED 5 may be a light source color other than white, for example, red, green, or blue. The LED 5 has a parasitic capacitance 50 (electrostatic capacitance) between a pair of terminals (a cathode terminal and an anode terminal). However, the light emitting element is not limited to the LED, and may be, for example, an organic electroluminescent element. Note that a capacitor may be electrically connected between the cathode terminal and the anode terminal of the LED 5 in order to suppress the fluctuation of the voltage applied to the LED 5. In this case, the capacitance of the capacitor and the parasitic capacitance 50 correspond to the capacitance of the LED 5.

  The lighting circuit 2 includes a constant current source 20 and a pair of first switches 21. The positive electrode of the constant current source 20 is electrically connected to the anode terminal of the LED 5 via one first switch 21. The negative electrode of the constant current source 20 is electrically connected to the cathode terminal of the LED 5 via the other first switch 21.

  The forced off circuit 4 includes a DC power supply 40 and a pair of second switches 41. The positive electrode of the DC power supply 40 is electrically connected to the cathode terminal of the LED 5 via one second switch 41. The negative electrode of the DC power supply 40 is electrically connected to the anode terminal of the LED 5 via the other second switch 41.

  The control circuit 3 turns on and off the pair of first switches 21 in conjunction with each other. The control circuit 3 turns on and off the pair of second switches 41 in conjunction with each other. The control circuit 3 receives an operation command from an external device such as an operation device (not shown), controls the lighting circuit 2 in accordance with the dimming level specified by the received operation command, and controls the light amount of the LED 5.

  Next, the operation of the lighting device 1 will be described with reference to the time charts of FIGS. In the time charts of FIGS. 2 and 3, the uppermost waveform shows the on / off state of the first switch 21, the second waveform from the top shows the forward current If of the LED 5, and the third waveform from the top. Represents the light quantity of the LED 5. The fourth waveform from the top indicates the on / off state of the second switch 41, and the fifth waveform from the top indicates the discharge current Id of the parasitic capacitance 50. Further, the second waveform from the bottom shows the x coordinate on the chromaticity diagram of the light emitted from the LED 5, and the lower waveform shows the y coordinate on the chromaticity diagram of the light emitted from the LED 5. .

  When the dimming level specified by the operation command is 100%, the control circuit 3 maintains the pair of first switches 21 in an on state and maintains the pair of second switches 41 in an off state. The lighting circuit 2 supplies a constant forward current If (the rated current of the LED 5) from the constant current source 20 to light the LED 5 (rated lighting) by keeping the pair of first switches 21 in the ON state.

  Further, when the dimming level specified by the operation command is 50%, the control circuit 3 maintains the pair of first switches 21 in the ON state during the predetermined first period T1, and sets the pair of second switches 41 is kept off (see FIG. 2). In the first period T1, the constant current source 20 supplies the rated forward current If to make the LED 5 light up at the rated speed. Further, when the first period T1 ends, the control circuit 3 turns off the pair of first switches 21 and turns on the pair of second switches 41. When the dimming level is 50%, the control circuit 3 keeps the pair of first switches 21 in the off state in the second period T2 having the same time length as the first period T1. That is, in the second period T2, the forward current If is not supplied from the constant current source 20 to the LED 5. Here, the control circuit 3 turns on and off the pair of first switches 21 so as to switch between the first period T1 and the second period T2 at a fixed period T0 (T0 = T1 + T2). According to the technical standards of the Electrical Appliance and Material Safety Law relating to LEDs, the repetition frequency of light output needs to be 500 Hz or more. Therefore, the period T0 is preferably equal to or less than about 2 milliseconds.

  As described above, when the first period T1 in which the rated forward current If flows through the LED 5 becomes half the period T0, the amount of light emitted from the LED 5 per unit time (for example, one second) also becomes half. As a result, the lighting device 1 can light the LED 5 at a dimming level of 50%.

  Here, in the first period T1, charges are accumulated in the parasitic capacitance 50 of the LED 5. The electric charge accumulated in the parasitic capacitance 50 in the first period T1 is discharged by turning off the pair of first switches 21. When the forced off circuit 4 is not provided, the electric charge accumulated in the parasitic capacitance 50 is discharged from the anode terminal of the LED 5 through the cathode terminal. As a result, the LED 5 is turned on during a period (transient period) until the charge stored in the parasitic capacitance 50 is exhausted. Since the peak value of the current flowing to the LED 5 during the transition period is larger than the rated forward current If, the color of the light (light source color) emitted from the LED 5 during the transition period is the light source when the rated forward current If flows. It will be out of color.

  On the other hand, the lighting device 1 includes a forced off circuit 4. The pair of second switches 41 of the forced off circuit 4 are controlled by the control circuit during a period (third period T3) that is sufficiently shorter than the period T0 and can discharge the charges of the parasitic capacitance 50 from the start of the second period T2. 3 is maintained in the on state (see FIG. 2). During the third period T3, the pair of second switches 41 are maintained in the ON state, so that the DC voltage of the DC power supply 40 is applied in the opposite direction between the anode terminal and the cathode terminal of the LED 5. Therefore, the electric charge accumulated in the LED 5 during the first period T1 is discharged through the pair of second switches 41 and the DC power supply 40. That is, the forced off circuit 4 discharges the electric charge accumulated in the parasitic capacitance 50 during the first period T1 without passing through the LED 5. As a result, the lighting device 1 can turn off the LED 5 from the time when the first period T1 is switched to the second period T2.

  Here, the control circuit 3 shortens the first period T1 and extends the second period T2 as the dimming level decreases. In other words, the control circuit 3 increases or decreases the ratio (duty ratio) of the first period T1 to the period T0 according to the dimming level. If the dimming level specified by the operation command is the lower limit (for example, 5%), the control circuit 3 sets the ratio of the first period T1 to the cycle T0 to the lower limit (for example, 5%) (FIG. 3). reference).

  As described above, in the lighting device 1, the control circuit 3 controls the pair of first switches 21 of the lighting circuit 2 by PWM (Pulse Width Modulation), thereby dimming the LED 5. In the lighting device 1, when the control circuit 3 switches the pair of first switches 21 from the on state to the off state, the forcible off circuit 4 transfers the electric charge accumulated in the parasitic capacitance 50 of the LED 5 without passing through the LED 5. Discharge. As a result, the lighting device 1 can suppress the variation in the color of the light emitted from the LED 5 (the variation in the chromaticity of the light source color), as compared with the case where the forced off circuit 4 is not provided.

  Incidentally, it is preferable that the forced off circuit 4 includes a current limiting element inserted in a path for discharging the electric charge stored in the parasitic capacitance 50. The current limiting element is preferably, for example, a resistor. The forced off circuit 4 can protect the circuit elements of the forced off circuit 4 such as the DC power supply 40 and the pair of second switches 41 by limiting the discharge current of the parasitic capacitance 50 by the current limiting element. it can.

(Embodiment 2)
The lighting device 1 according to the second embodiment includes three lighting circuits 2, a control circuit 3, and three forced off circuits 4, as shown in FIG. The lighting system 6 according to the second embodiment includes the lighting device 1 and three LEDs 5.

  The lighting system 6 illuminates the three LEDs 5 with the DC power supplied from the DC power supply circuit 71 to illuminate. The DC power supply circuit 71 converts AC power supplied from the AC power supply 70 into DC power. Further, it is preferable that the DC power supply circuit 71 is configured by, for example, a full-wave rectifier, a smoothing capacitor, a power factor improving circuit (a boost chopper circuit), and the like. Note that, instead of the AC power supply 70 and the DC power supply circuit 71, DC power may be supplied to the lighting system 6 from a DC power supply such as a storage battery.

  The three LEDs 5 are a first LED 5A whose light source color is red, a second LED 5B whose light source color is green, and a third LED 5C whose light source color is blue. The first LED 5A has a first parasitic capacitance 50A. The second LED 5B has a second parasitic capacitance 50B. The third LED 5C has a third parasitic capacitance 50C. However, the number (type) of the LEDs 5 is not limited to three. For example, the LED 5 may be two types of white LEDs (for example, a light bulb color LED and a neutral white LED) having different correlated color temperatures of the light source colors. Alternatively, an LED of a light source color other than red, green, and blue (for example, white) may be included.

  The lighting device 1 includes three lighting circuits 2, a control circuit 3, and three forced off circuits 4. Note that the three lighting circuits 2 may be referred to as a first lighting circuit 2A, a second lighting circuit 2B, and a third lighting circuit 2C. The three forced off circuits 4 may be referred to as a first forced off circuit 4A, a second forced off circuit 4B, and a third forced off circuit 4C.

  The first lighting circuit 2A has a constant current source (not shown) and a pair of first switches (not shown), like the lighting circuit 2 in the lighting device 1 of the first embodiment. The constant current source is preferably a switching power supply circuit (for example, a step-down chopper circuit, a step-up / step-down chopper circuit, or an isolated DC-DC converter). Preferably, the first switch is a semiconductor switching element such as a bipolar transistor or a field effect transistor. The constant current source supplies a constant current (for example, a rated forward current of the first LED 5A) to the first LED 5A when the pair of first switches is in an ON state, and turns on the first LED 5A (rated lighting). ).

  The second lighting circuit 2B has a constant current source (not shown) and a pair of first switches (not shown), like the lighting circuit 2 in the lighting device 1 of the first embodiment. The constant current source is preferably a switching power supply circuit, as in the first lighting circuit 2A. Preferably, the first switch is a semiconductor switching element such as a bipolar transistor or a field effect transistor. The constant current source supplies a constant current (for example, a rated forward current of the second LED 5B) to the second LED 5B when the pair of first switches is in an on state, and turns on the second LED 5B (rated lighting). ).

  The third lighting circuit 2C has a constant current source (not shown) and a pair of first switches (not shown), like the lighting circuit 2 in the lighting device 1 of the first embodiment. The constant current source is preferably a switching power supply circuit, like the first lighting circuit 2A and the second lighting circuit 2B. Preferably, the first switch is a semiconductor switching element such as a bipolar transistor or a field effect transistor. The constant current source supplies a constant current (for example, a rated forward current of the third LED 5C) to the third LED 5C when the pair of first switches are in an on state to light the third LED 5C (rated lighting). ).

  The first forced off circuit 4A has a DC power supply (not shown) and a pair of second switches (not shown), similarly to the forced off circuit 4 in the lighting device 1 of the first embodiment. The first forced off circuit 4A discharges the electric charge accumulated in the first parasitic capacitance 50A when the pair of second switches is on. The second forced off circuit 4B has a DC power supply (not shown) and a pair of second switches (not shown), similarly to the forced off circuit 4 in the lighting device 1 of the first embodiment. The second forced off circuit 4B discharges the electric charge accumulated in the second parasitic capacitance 50B when the pair of second switches is on. The third forced off circuit 4C has a DC power supply (not shown) and a pair of second switches (not shown), similarly to the forced off circuit 4 in the lighting device 1 of the first embodiment. The third forcible off circuit 4C discharges the electric charge accumulated in the third parasitic capacitance 50c when the pair of second switches is on. It is preferable that the DC power supply included in each of the first to third forced off circuits 4A to 4C is a switching power supply circuit that steps up, steps down, or steps up or down the DC voltage supplied from the DC power supply circuit 71. The second switch included in each of the first to third forced off circuits 4A to 4C is preferably a semiconductor switching element such as a bipolar transistor or a field effect transistor.

  The control circuit 3 PWM-controls a pair of first switches included in each of the first lighting circuit 2A, the second lighting circuit 2B, and the third lighting circuit 2C according to the dimming level specified by the operation command. I do. That is, the control circuit 3 increases / decreases the average value per unit time of the output current of each of the first lighting circuit 2A, the second lighting circuit 2B, and the third lighting circuit 2C, so that the first LED 5A, The light amount of each of the second LED 5B and the third LED 5C is separately adjusted. Further, the control circuit 3 adjusts (tones) the ratio of the light amount of each of the first LED 5A, the second LED 5B, and the third LED 5C according to the toning instruction value instructed by the operation command. Here, the toning instruction value is a value that indicates the color (chromaticity) of the light emitted by the illumination system 6. Specifically, it is a ratio of the light amount of the first LED 5A, the light amount of the second LED 5B, and the light amount of the third LED 5C required to reproduce the light color indicated by the toning instruction value. That is, the light color of the illumination system 6 is determined by the ratio of the light amount of the first LED 5A, the light amount of the second LED 5B, and the light amount of the third LED 5C.

  When switching the pair of first switches of the first lighting circuit 2A from the ON state to the OFF state, the control circuit 3 switches the second switch of the first forced OFF circuit 4A from the OFF state to the ON state. While the pair of second switches of the first forced off circuit 4A is maintained in the on state by the control circuit 3, the electric charge accumulated in the first parasitic capacitance 50A is transferred via the first forced off circuit 4A. Discharged. That is, the first forced off circuit 4A discharges the electric charge accumulated in the first parasitic capacitance 50A during the first period without passing through the first LED 5A. As a result, the lighting device 1 can turn off the first LED 5A from the point in time when the lighting period is switched from the first period to the second period.

  Further, when switching the pair of first switches of each of the second and third lighting circuits 2B and 2C from the ON state to the OFF state, the control circuit 3 sets each of the second and third forced OFF circuits 4B and 4C. Is switched from the off state to the on state. While the pair of second switches of the second and third forced off circuits 4B and 4C are kept on by the control circuit 3, the electric charges accumulated in the second and third parasitic capacitances 50B and 50C are: It is discharged through the second and third forced off circuits 4B and 4C. That is, the second and third forced off circuits 4B and 4C do not pass the charges accumulated in the second and third parasitic capacitances 50B and 50C during the first period without passing through the second and third LEDs 5B and 5C. Discharge. As a result, the lighting device 1 can turn off the second and third LEDs 5B and 5C from the time when the first period is switched to the second period.

  As described above, in the lighting device 1 according to the second embodiment, the control circuit 3 performs the PWM control on the pair of first switches 21 of each of the three lighting circuits 2, so that the light emitted and mixed from the three LEDs 5 is mixed. Dimming and toning. In the lighting device 1, when the control circuit 3 switches the pair of first switches 21 from the on state to the off state, each of the three forced off circuits 4 is accumulated in the parasitic capacitance 50 of each of the three LEDs 5. The electric charge is discharged without passing through each LED 5. As a result, compared to the case where the lighting device 1 is not provided with the forced off circuit 4, the variation in the color of the light emitted from each LED 5 and the mixed light (variation in the chromaticity of the light source color) can be suppressed. it can.

  Here, a modified example of the lighting device 1 and the lighting system 6 according to the second embodiment will be described. In the lighting device 1 of the modified example, as shown in FIG. 5, the electric charge accumulated in the first to third parasitic capacitances 50 </ b> A to 50 </ b> C is discharged by one forced off circuit 4. That is, the forcible off circuit 4 in the modification has a DC power supply (not shown) and three pairs of second switches. However, one second switch of each of the three pairs of second switches may be shared. That is, it is preferable that the forced off circuit 4 has one DC power supply and four second switches.

  In the lighting device 1 and the lighting system 6 of the above modified example, the number of the forced off circuits 4 is reduced from three to one, so that the manufacturing cost of the lighting device 1 and the lighting system 6 can be reduced.

(Embodiment 3)
As shown in FIG. 6, the lighting device 1 and the lighting system 6 according to the third embodiment are characterized in the configuration of the forced off circuit 4. 6 and in common.

  As shown in FIG. 6, the forced off circuit 4 according to the third embodiment includes a capacitor 42 corresponding to a DC power supply, a current-limiting resistor 43, and a pair of third switches 44. The capacitor 42 is preferably an electrolytic capacitor or an electric double layer capacitor.

  The positive electrode of the capacitor 42 is electrically connected to the anode terminal of the LED 5 via one third switch 44. The positive electrode of the capacitor 42 is electrically connected to the cathode terminal of the LED 5 via one second switch 41. The negative electrode of the capacitor 42 is electrically connected to the cathode terminal of the LED 5 via the resistor 43 and the other third switch 44. Further, the negative electrode of the capacitor 42 is electrically connected to the anode terminal of the LED 5 via the resistor 43 and the other second switch 41. The pair of third switches 44 are turned on and off in conjunction with each other by the control circuit 3.

  The control circuit 3 turns on the pair of first switches 21 and the pair of third switches 44 in the first period T1. In the first period T1 in which the pair of first switches 21 are on, a forward current flows from the constant current source 20 to the LED 5 via the pair of first switches 21, and the LED 5 is turned on. In the first period T1, the output current (DC current) of the constant current source 20 flows to the forced off circuit 4 via the pair of first switches 21 and the pair of third switches 44, so that the capacitor 42 is charged. You.

  The control circuit 3 turns off the pair of first switches 21 and the pair of third switches 44 during the second period T2. Further, when shifting from the first period T1 to the second period T2, the control circuit 3 turns off the pair of first switches 21 and the pair of third switches 44 during the third period T3, The second switch 41 is kept on. In the third period T3, since the voltage between both ends of the capacitor 42 is applied to the parasitic capacitance 50 during the first period T1, the charge stored in the parasitic capacitance 50 during the first period T1 is forced to pass through the LED 5 without passing through the LED 5. 4 discharge. As a result, the lighting device 1 can turn off the LED 5 from the time when the first period is switched to the second period.

  As described above, the lighting device 1 and the lighting system 6 according to the third embodiment discharge the electric charge accumulated in the parasitic capacitance 50 of the LED 5 by the forced off circuit 4 without passing through the LED 5, so that the light emitted from the LED 5 Can be suppressed. Moreover, since the lighting device 1 and the lighting system 6 of the third embodiment use the capacitor 42 as a DC power supply, the manufacturing cost can be reduced by simplifying the circuit configuration as compared with the case where the switching power supply circuit is a DC power supply. Can be.

  As described above, in the lighting device (1) according to the first embodiment, the direct current is applied to the light emitting element through the pair of terminals with respect to the light emitting element (LED 5) having the capacitance (parasitic capacitance 50) between the pair of terminals. And a lighting circuit (2) for supplying (forward current If). A lighting device (1) according to a first aspect includes a control circuit (3). The control circuit (3) controls the lighting circuit (2) to alternately switch a first period (T1) for supplying a DC current to the light emitting element and a second period (T2) for not supplying a DC current to the light emitting element. In addition, the ratio between the first period (T1) and the second period (T2) per unit time is changed. The lighting device (1) according to the first aspect emits the charge stored in the capacitance when the lighting circuit (2) is switched from the first period (T1) to the second period (T2). A forced off circuit (4) for discharging without passing through the element is provided.

  In the lighting device (1) according to the first aspect, the forced off circuit (4) discharges the electric charge accumulated in the capacitance during the first period (T1) without passing through the light emitting element. The light emitting element can be turned off at the time when the period is switched from (T1) to the second period (T2). As a result, the lighting device (1) according to the first aspect can suppress variation in the chromaticity of the light source color.

  The lighting device (1) according to the second aspect can be realized by a combination with the first aspect. In the lighting device (1) according to the second aspect, a first lighting circuit (2A) and a second lighting circuit (2B), which are lighting circuits (2), and a first lighting circuit (4), which is a forced off circuit (4). It is preferable to include a forced off circuit (4A) and a second forced off circuit (4B). It is preferable that the first lighting circuit (2A) supplies a direct current to the first light emitting element having the first light source color among the plurality of light emitting elements. It is preferable that the second lighting circuit (2B) supplies a DC current to a second light emitting element having a second light source color having a chromaticity different from the first light source color among the plurality of light emitting elements. When the first lighting circuit (2A) is switched from the first period (T1) to the second period (T2), the first forced off circuit (4A) reduces the capacitance of the first light emitting element. It is preferable to discharge the stored charge without passing through the first light emitting element. When the second lighting circuit (2B) is switched from the first period (T1) to the second period (T2), the second forced off circuit (4B) reduces the capacitance of the second light emitting element. It is preferable to discharge the stored charge without passing through the second light emitting element.

  The lighting device (1) according to the second aspect suppresses a variation in chromaticity of each light source color of the first light emitting element and the second light emitting element having different light source colors, so that the first light emitting element Variations in the chromaticity of the color of the light in which the light and the light of the second light emitting element are mixed can be suppressed.

  The lighting device (1) according to the third aspect can be realized by a combination with the first aspect. The lighting device (1) according to the third aspect preferably includes a first lighting circuit (2A) and a second lighting circuit (2B), which are lighting circuits (2). It is preferable that the first lighting circuit (2A) supplies a direct current to the first light emitting element having the first light source color among the plurality of light emitting elements. It is preferable that the second lighting circuit (2B) supplies a DC current to a second light emitting element having a second light source color having a chromaticity different from the first light source color among the plurality of light emitting elements. When the first lighting circuit (2A) and the second lighting circuit (2B) are switched from the first period (T1) to the second period (T2), the first light emitting element is turned on. It is preferable that electric charge stored in the capacitance of the second light-emitting element be discharged without passing through the first light-emitting element and the second light-emitting element.

  The lighting device (1) according to the third aspect discharges the electric charges stored in the capacitance of the first light emitting element and the capacitance of the second light emitting element by one forced off circuit (4). In addition, the number of the forced off circuits (4) can be reduced to reduce the manufacturing cost.

  The lighting device (1) according to the fourth aspect can be realized by a combination with any of the first to third aspects. In the lighting device (1) according to the fourth aspect, the forced off circuit (4) may include a current limiting element (resistor 43) inserted in a path for discharging the charge stored in the capacitance. preferable.

  The lighting device (1) according to the fourth aspect electrically protects the circuit element of the forced off circuit (4) by limiting the discharge current of the capacitance by the current limiting element (the resistor 43). be able to.

  The lighting device (1) according to the fifth aspect can be realized by a combination with any one of the first to fourth aspects. In the lighting device (1) according to the fifth aspect, the forced off circuit (4) preferably includes a circuit or a circuit element that applies a reverse DC voltage between the pair of terminals.

  The lighting device (1) according to the fifth aspect can quickly discharge the charge accumulated in the capacitance by applying a reverse DC voltage between the pair of terminals of the light emitting element.

  The lighting device (1) according to the sixth aspect can be realized by a combination with the fifth aspect. In the lighting device (1) according to the sixth aspect, the circuit element is preferably a capacitor (42).

  The lighting device (1) according to the sixth aspect stores the electric charge in the capacitor (42) during the first period (T1), so that the voltage across the capacitor (42) is applied in the opposite direction between the pair of terminals of the light emitting element. Can be applied. As a result, the lighting device (1) according to the sixth aspect can quickly discharge the charge accumulated in the capacitance while simplifying the circuit configuration of the forced off circuit (4).

  The lighting device (1) according to the seventh aspect can be realized by a combination with the fifth aspect. In the lighting device (1) according to the seventh aspect, the circuit is preferably a switching power supply circuit.

  The lighting device (1) according to the seventh aspect stabilizes the operation of the forced off circuit (4) by keeping the DC voltage applied to the capacitance from the forced off circuit (4) constant by the switching power supply circuit. Can be done.

  The lighting device (1) according to the eighth aspect can be realized by a combination with any one of the first to seventh aspects. In the lighting device (1) according to the eighth aspect, the capacitance preferably includes a parasitic capacitance (50) of the light emitting element.

  The lighting device (1) according to the eighth aspect can suppress variation in chromaticity of a light source color.

  A lighting system (6) according to a ninth aspect has the lighting device (1) according to any one of the first to eighth aspects, and a capacitance between a pair of terminals, and through a pair of terminals. And one or more light emitting elements (LED5) to which a direct current is supplied from the lighting device (1).

  The lighting system (6) according to the ninth aspect turns off the light-emitting element from the point in time when the first period (T1) is switched to the second period (T2), thereby suppressing variation in the chromaticity of the light source color. .

Reference Signs List 1 lighting device 2 lighting circuit 2A first lighting circuit 2B second lighting circuit 3 control circuit 4 forced off circuit 4A first forced off circuit 4B second forced off circuit 5 LED (light emitting element)
6 Lighting system 42 Capacitor 43 Resistor (current limiting element)
50 Parasitic capacitance (capacitance)
T1 First period T2 Second period

Claims (9)

For a light emitting element having a capacitance between a pair of terminals, a lighting circuit for supplying a direct current to the light emitting element through the pair of terminals,
Controlling the lighting circuit to alternately switch a first period for supplying the DC current to the light emitting element and a second period for not supplying the DC current to the light emitting element, and the first period per unit time; And a control circuit for changing the ratio of the second period,
When the lighting circuit is switched from the first period to the second period, the charge stored in the capacitance is discharged without passing through the light emitting element.
Lighting device. A first lighting circuit and a second lighting circuit, which are the lighting circuits;
A first forced off circuit and a second forced off circuit, which are the forced off circuits,
The first lighting circuit supplies a direct current to a first light emitting element having a first light source color among a plurality of the light emitting elements,
The second lighting circuit supplies a direct current to a second light emitting element having a second light source color having a different chromaticity from the first light source color among the plurality of light emitting elements,
When the first lighting circuit is switched from the first period to the second period, the first forcible off circuit stores the electric charge stored in the capacitance of the first light emitting element. Discharging without passing through the first light emitting element;
When the second lighting circuit is switched from the first period to the second period, the second forcible off circuit stores the electric charge stored in the capacitance of the second light emitting element. Discharging without passing through the second light emitting element;
The lighting device according to claim 1. A first lighting circuit and a second lighting circuit, which are the lighting circuits,
The first lighting circuit supplies a direct current to a first light emitting element having a first light source color among a plurality of the light emitting elements,
The second lighting circuit supplies a direct current to a second light emitting element having a second light source color having a different chromaticity from the first light source color among the plurality of light emitting elements,
The forced off circuit includes the first light emitting element and the second light emitting element when the first lighting circuit and the second lighting circuit are switched from the first period to the second period. Discharging the electric charge stored in the capacitance without passing through the first light emitting element and the second light emitting element;
The lighting device according to claim 1. The forced off circuit has a current limiting element inserted in a path for discharging the charge stored in the capacitance.
The lighting device according to claim 1. The forced off circuit has a circuit or a circuit element for applying a reverse DC voltage between the pair of terminals,
The lighting device according to claim 1. The circuit element is a capacitor;
The lighting device according to claim 5. The circuit is a switching power supply circuit,
The lighting device according to claim 5. The capacitance includes a parasitic capacitance of the light emitting element,
The lighting device according to claim 1. A lighting device according to any one of claims 1 to 8,
Having a capacitance between a pair of terminals, having one or more light emitting elements to which a direct current is supplied from the lighting device through the pair of terminals,
Lighting system.

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