Power supply device and lighting fixture

Abstract

To provide a power supply device and a lighting fixture capable of improving reliability.SOLUTION: A power supply device includes a first circuit 271, a second circuit 272, and a control circuit 273. The first circuit 271 converts an input voltage input from a power supply PS into a predetermined output voltage V2. The second circuit 272 is provided in a stage subsequent to the first circuit 271 and supplies a constant current to a light source module 10. The control circuit 273 controls the first circuit 271 and the second circuit 272 according to a dimming signal Sig1 from the outside. The first circuit 271 has a switching element Q1 that uses a semiconductor including silicon carbide as a material and performs high frequency switching operation. When the dimming signal Sig1 instructs to stop supply of the constant current from the second circuit 272 to the light source module 10, the control circuit 273 causes the switching element Q1 of the first circuit 271 to stop the high frequency switching operation for at least a certain period.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure generally relates to a power supply device and a lighting fixture, and more particularly to a power supply device and a lighting fixture including a switching element that performs a high-frequency switching operation.

Background Art

[0002] The lighting device described in Patent Document 1 includes a rectifier circuit, a power factor improvement circuit, a first detection circuit, and a control circuit. The rectifier circuit has a rectifier and rectifies the input voltage. The power factor improvement circuit includes a switching element, smoothes the output voltage of the rectifier circuit, boosts it to a predetermined boosted voltage, and improves the input power factor. The first detection circuit detects a first detection value proportional to the input voltage or input current to the power factor improvement circuit. The control circuit reduces the boosted voltage of the power factor improvement circuit when the first detection value is smaller than a predetermined value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a lighting device as described in Patent Document 1, when the power factor improvement circuit continues to operate in a standby mode in which the current to the light source module is stopped while the input voltage is supplied, the corrosion of the switching element included in the power factor improvement circuit may progress rapidly, and the reliability may decrease.

[0005] In view of the above reasons, the present disclosure is made, and an object thereof is to provide a power supply device and a lighting fixture capable of improving reliability.

Means for Solving the Problems

[0006] A power supply device according to one aspect of the present disclosure includes a first circuit that converts an input voltage input from a power supply into a predetermined output voltage, a second circuit provided downstream of the first circuit that supplies a constant current to a light source module, and a control circuit that controls the first circuit and the second circuit in response to a dimming signal from the outside. The first circuit has a switching element made of a semiconductor containing silicon carbide and performing a high-frequency switching operation. When the control circuit is instructed to stop the supply of the constant current from the second circuit to the light source module by the dimming signal, the control circuit stops the high-frequency switching operation of the switching element in the first circuit for at least a certain period.

[0007] A lighting fixture according to one aspect of the present disclosure includes the power supply device and the light source module.

Advantages of the Invention

[0008] The power supply device and the lighting fixture of the present disclosure can improve reliability.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0010] The power supply device 2 according to an embodiment of the present disclosure and the lighting fixture A1 including the power supply device 2 will be described in detail with reference to the drawings. However, each drawing described in the following embodiments is a schematic diagram, and the respective ratios of the sizes and thicknesses of the respective components do not necessarily reflect the actual dimensional ratios. Note that the configurations described in the following embodiments are merely examples of the present disclosure. The present disclosure is not limited to the following embodiments, and various modifications can be made according to the design and the like as long as the effects of the present disclosure can be achieved.

[0011] (Embodiment 1) (1) Outline As shown in FIGS. 1 to 3, the power supply device 2 according to Embodiment 1 includes a first circuit 271, a second circuit 272, and a control circuit 273.

[0012] The first circuit 271 converts an input voltage input from a power supply PS into a predetermined output voltage V2.

[0013] The second circuit 272 is provided at a subsequent stage of the first circuit 271 and supplies a constant current to the light source module 10.

[0014] The control circuit 273 controls the first circuit 271 and the second circuit 272 in accordance with a dimming signal Sig1 from the outside.

[0015] The first circuit 271 has a switching element Q1 made of a semiconductor containing silicon carbide and performing a high-frequency switching operation.

[0016] When the control circuit 273 is instructed to stop the supply of the constant current from the second circuit 272 to the light source module 10 by the dimming signal Sig1, the control circuit 273 stops the high-frequency switching operation of the switching element Q1 of the first circuit 271 for at least a certain period.

[0017] Here, it has been experimentally confirmed that when the switching element Q1 made of a semiconductor containing silicon carbide performs a high-frequency switching operation, corrosion of a part of the semiconductor containing silicon carbide is promoted.

[0018] According to the above configuration, when the supply of a constant current to the light source module 10 is instructed by the dimming signal Sig1, by stopping the high-frequency switching operation of the switching element Q1 for at least a certain period, corrosion of the semiconductor containing silicon carbide, which is the material of the switching element Q1, can be suppressed. Thereby, a decrease in the performance of the switching element Q1 can be suppressed, and as a result, the reliability of the power supply device 2 can be improved.

[0019] (2) Details The lighting fixture A1 according to the embodiment (hereinafter abbreviated as the lighting fixture A1) is a floodlight mainly used for lighting (floodlighting) soccer stadiums, various stadiums, school playgrounds, and the like. In the following description, unless otherwise specified, the up-down, front-back, and left-right directions indicated by arrows in FIG. 1 and the like are defined as the up-down, front-back, and left-right directions of the lighting fixture A1.

[0020] The lighting fixture A1 includes a power supply device 2 and, for example, two light source units 1. The lighting fixture A1 further includes a pair of connecting members 4 that connect the two light source units 1 and a support member 3 that supports the two light source units 1 (see FIGS. 1 and 2). It is assumed that the two light source units 1 have the same structure. Note that the lighting fixture A1 may include one light source unit 1 or three or more light source units 1.

[0021] (2-1) Light Source Unit The two light source units 1 have the same configuration.

[0022] As shown in FIG. 1, each light source unit 1 includes a light source module 10, a cover 11, a heat dissipation block 12, and a frame body 13.

[0023] The light source module 10 is, for example, a light source module in which a plurality of light emitting elements (LEDs) 100 are mounted on the front surface (the surface) of a flat substrate 101. The plurality of light emitting elements 100 mounted on the light source module 10 emit light by the power supplied from the power supply device 2 to the light source unit 1. However, the light emitting element 100 is not limited to an LED, and may be an organic electroluminescence element, a semiconductor laser element, or the like. The substrate 101 is, for example, a metal base substrate based on an aluminum plate.

[0024] As shown in FIG. 1, the cover 11 is arranged to cover the light source module 10 from the front. The cover 11 is formed of a synthetic resin having translucency such as an acrylic resin or a polycarbonate resin. A plurality of lenses corresponding one-to-one to the plurality of light emitting elements 100 are provided on the rear surface of the cover 11 (not shown). Each of the plurality of lenses provided on the rear surface of the cover 11 has, for example, a collimating function of making the light output from the corresponding light emitting element 100 approach parallel light.

[0025] The heat dissipation block 12 has a base portion 120 and a plurality of heat dissipation plates 121 (see FIGS. 1 and 2). The base portion 120 is formed, for example, in a rectangular flat plate shape from an aluminum alloy. The light source module 10 is attached to the front surface of the base portion 120 using a plurality of screws, whereby the substrate 101 of the light source module 10 and the base portion 120 are mechanically and thermally connected.

[0026] The plurality of heat dissipation plates 121 are formed, for example, in a flat plate shape from an aluminum alloy. These plurality of heat dissipation plates 121 are attached to the rear surface of the base portion 120 at regular intervals as shown in FIG. 2.

[0027] The heat dissipation block 12 can suppress the temperature rise of the light source module 10 and improve the luminous efficiency by efficiently dissipating the heat generated by the plurality of light emitting elements 100 during lighting.

[0028] The frame body 13 is formed in a rectangular cylindrical shape. The frame body 13 is formed, for example, by aluminum die casting or the like. The frame body 13 holds the cover 11 on the inside.

[0029] (2-2) Connecting member The pair of connecting members 4 have the same configuration.

[0030] The connecting member 4 is fastened to the side surfaces of the base portions 120 of the two light source units 1 arranged one above the other with a plurality of fastening parts (hexagon bolts or the like) 46.

[0031] As a result, the two light source units 1 are connected by a pair of connecting members 4 in a state of being arranged in two upper and lower rows (see FIG. 1).

[0032] (2-3) Power supply device As shown in FIG. 1, the power supply device 2 is fixed to the two light source units 1 by a pair of fixing bases 6.

[0033] As shown in FIGS. 2 and 3, the power supply device 2 includes a housing 20 and a power supply circuit 27 housed in the housing 20.

[0034] The housing 20 includes a box-shaped case body 21 with one side (rear side) open and a case lid 22 that closes the opening surface (rear side) of the case body 21. Both the case body 21 and the case lid 22 are formed of an aluminum alloy.

[0035] Case side attachment portions 23 are provided one by one on the left and right side surfaces of the case body 21. Each case side attachment portion 23 is formed in a columnar shape and is integrally formed with the case body 21 so as to protrude in the left-right direction from approximately the center in the up-down direction on the left and right side surfaces of the case body 21.

[0036] Two power supply lines P1 are led out from the bottom surface of the housing 20 (see Fig. 2). One power supply line P1 is electrically connected to the lower light source unit 1 to supply the direct current output from the power supply device 2 to the lower light source unit 1. The other power supply line P1 is electrically connected to the upper light source unit 1 to supply the direct current output from the power supply device 2 to the upper light source unit 1.

[0037] The case lid 22 is formed in a rectangular flat plate shape. The case lid 22 is placed on the opening surface of the case body 21 so as to overlap the rear end surface of the case body 21, and is screwed to the case body 21 with a plurality of screws (see Fig. 2). The power supply circuit 27 is housed in the internal space surrounded by the case body 21 and the case lid 22.

[0038] As shown in Fig. 3, the power supply circuit 27 includes a rectifier circuit 270, a first circuit 271, a second circuit 272 provided at the subsequent stage of the first circuit 271, and a control circuit 273.

[0039] The control circuit 273 includes a first drive circuit 274, a second drive circuit 275, a drive control circuit 276, a voltage detection circuit 277, and a communication unit 278. The drive control circuit 276 is connected to the first drive circuit 274, the second drive circuit 275, the voltage detection circuit 277, and the communication unit 278 that receives the dimming signal Sig1 from the outside.

[0040] The drive control circuit 276 controls the first drive circuit 274 and the second drive circuit 275 based on the voltage detection result of the voltage detection circuit 277 and the reception result of the communication unit 278. The drive control circuit 276 mainly includes a microcontroller having one or more processors and one or more memories as main components. The drive control circuit 276 controls the first drive circuit 274 and the second drive circuit 275 by transmitting control signals to the first drive circuit 274 and the second drive circuit 275. The control signals transmitted from the drive control circuit 276 to the first drive circuit 274 and the second drive circuit 275 include, for example, PWM signals, analog voltage signals, digital signals transmitted by UART, etc.

[0041] The rectifier circuit 270 includes, for example, a plurality of diodes connected in a full-bridge configuration. The rectifier circuit 270 full-wave rectifies an input voltage (alternating current voltage Vac) input from a power supply PS which is an alternating current power supply, and outputs a direct current rectified voltage V1.

[0042] The first circuit 271 has, for example, a boost circuit BC that boosts the rectified voltage V1 to a predetermined output voltage V2.

[0043] As shown in FIG. 3, the boost circuit BC includes a capacitor C1, an inductor L1, a switching element Q1, a diode D1, and a smoothing capacitor C2.

[0044] The switching element Q1 is, for example, an n-channel type MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). Note that the switching element Q1 is not limited to an n-channel type MOSFET, and may be a p-channel type MOSFET, or an IGBT (Insulated Gate Bipolar Transistor) or the like.

[0045] The capacitor C1 is connected between the output terminals of the rectifier circuit 270, and the rectified voltage V1 is applied between the positive and negative electrodes of the capacitor C1.

[0046] The first end of the inductor L1 is connected to the positive electrode of the capacitor C1, and the second end of the inductor L1 is connected to the anode of the diode D1.

[0047] The cathode of the diode D1 is connected to the positive electrode of the smoothing capacitor C2. The negative electrode of the smoothing capacitor C2 is connected to the negative electrode of the capacitor C1.

[0048] The drain of the switching element Q1 is connected to the connection point between the inductor L1 and the diode D1, and the source of the switching element Q1 is connected to the negative electrode of the capacitor C1.

[0049] The gate of the switching element Q1 is connected to a first drive circuit 274 included in the control circuit 273. The first drive circuit 274 drives the switching element Q1 to turn on / off by applying a gate voltage between the gate and source of the switching element Q1. More specifically, the drive control circuit 276 controls the first drive circuit 274 to drive the switching element Q1 to turn on / off.

[0050] When the switching element Q1 turns on, a current flows through a path from the positive output terminal of the rectifier circuit 270, through the inductor L1 and the switching element Q1, to the negative output terminal of the rectifier circuit 270. Due to this current, magnetic energy is stored in the inductor L1. Next, when the switching element Q1 turns off, the magnetic energy of the inductor L1 is released, and a current flows through a path from the second terminal of the inductor L1, through the diode D1, the smoothing capacitor C2, and the capacitor C1, to the first terminal of the inductor L1. Due to this current, an output voltage V2 obtained by boosting the rectified voltage V1 is generated across the smoothing capacitor C2. The magnitude of the output voltage V2 is adjusted by making the duty ratio (the ratio of the on-time to the switching period) of the switching element Q1 variable.

[0051] The switching element Q1 includes a semiconductor chip 7 (see FIG. 4) mainly made of a semiconductor containing silicon carbide (SiC). The semiconductor chip 7 is housed within the package of the switching element Q1. Note that FIG. 4 is a cross-sectional view of the peripheral portion of the semiconductor chip 7.

[0052] As shown in FIG. 4, the semiconductor chip 7 has a semiconductor layer 70 made of silicon carbide, a first electrode 71, a second electrode 72, and a protective film 73.

[0053] The semiconductor layer 70 includes a first layer Ly1 made of an n-type semiconductor obtained by doping silicon carbide with impurities (such as aluminum and boron), a second layer Ly2 made of a p-type semiconductor obtained by doping silicon carbide with impurities (such as phosphorus and arsenic), and a third layer Ly3 made of an n-type semiconductor. More specifically, the semiconductor layer 70 is formed by providing the second layer Ly2 on the surface F1 of the first layer Ly1 and providing the third layer Ly3 on the surface F2 of the second layer Ly2. Note that the structure of the semiconductor chip 7 described above is an example in the case where the switching element Q1 is an n-channel MOSFET. When the switching element Q1 is an element different from an n-channel MOSFET, the structure of the semiconductor chip 7 is different from the above structure.

[0054] The first electrode 71 is provided so as to be in contact with the back surface Rv1 of the first layer Ly1. In the present embodiment, the switching element Q1 is an n-channel MOSFET, and the first electrode 71 is the drain of the n-channel MOSFET.

[0055] The second electrode 72 is provided in contact with the second layer Ly2 and the third layer Ly3. In the present embodiment, the second electrode 72 is the source of the n-channel MOSFET.

[0056] Also, although not shown, the semiconductor chip 7 has a third electrode that contacts the second layer Ly2 and the third layer Ly3 via an insulating layer. The third electrode is the gate of the n-channel MOSFET.

[0057] When a voltage (gate voltage) equal to or higher than a predetermined value is applied between the second electrode 72 as the source and the third electrode as the gate, a channel that electrically connects the first layer Ly1 and the third layer Ly3 is formed in the second layer Ly2. As a result, the first electrode 71 and the second electrode 72 are electrically connected through the channel formed in the second layer Ly2. That is, when a voltage is applied between the second electrode 72 and the third electrode, the switching element Q1 is turned on, and current flows from the first electrode 71 to the second electrode 72. On the other hand, when a voltage equal to or higher than a predetermined value is not applied between the second electrode 72 and the third electrode, the first electrode 71 and the second electrode 72 are insulated. That is, when a voltage equal to or higher than a predetermined value is not applied between the second electrode 72 and the third electrode, the switching element Q1 is turned off, and no current flows from the first electrode 71 to the second electrode 72. In other words, the second layer Ly2 in which the channel is formed is a conduction part Cn1 through which current flows in the switching element Q1 in response to a high-frequency switching operation.

[0058] Further, the semiconductor layer 70 further has a guard ring part G1. The guard ring part G1 is provided around the second layer Ly2 which is the conduction part Cn1. The guard ring part G1 is composed of a p-type semiconductor formed in an annular shape. The p-type semiconductor constituting the guard ring part G1 is, for example, a p-type semiconductor made of silicon carbide. The guard ring part G1 suppresses a decrease in the breakdown voltage performance of the switching element Q1 by alleviating the electric field concentration at the peripheral part of the semiconductor chip 7.

[0059] Note that the diode D1 also includes a semiconductor chip mainly made of a semiconductor containing silicon carbide, similar to the switching element Q1. Also, the semiconductor chip included in the diode D1 has a conduction part through which current flows in response to the high-frequency switching operation of the switching element Q1, and a guard ring part provided around the conduction part.

[0060] The protective film 73 is a so-called passivation film formed on the semiconductor layer 70 so as to cover at least the guard ring part G1. The protective film 73 is a passivation film made of polyimide.

[0061] The second circuit 272 is provided downstream of the first circuit 271. The second circuit 272 supplies a current Iout to the light source module 10.

[0062] The second circuit 272 is, for example, a step-down circuit.

[0063] As shown in FIG. 3, the second circuit 272 includes a switching element Q2, a diode D2, an inductor L2, and a smoothing capacitor C3. The switching element Q2 is, for example, an n-channel MOSFET. Note that the switching element Q1 is not limited to an n-channel MOSFET and may be a p-channel MOSFET or an IGBT or the like.

[0064] The cathode of the diode D2 is connected to the positive electrode of the smoothing capacitor C2. Also, the cathode of the diode D2 is connected to the positive electrode of the smoothing capacitor C3.

[0065] The anode of the diode D2 is connected to the drain of the switching element Q2.

[0066] The source of the switching element Q2 is connected to the negative electrode of the smoothing capacitor C2.

[0067] The gate of the switching element Q2 is connected to a second drive circuit 275 included in the control circuit 273. The second drive circuit 275 drives the switching element Q2 on / off by applying a gate voltage between the gate and source of the switching element Q2. More specifically, the drive control circuit 276 controls the second drive circuit 275 to drive the switching element Q2 on / off.

[0068] The first end of the inductor L2 is connected to the connection point between the anode of the diode D2 and the drain of the switching element Q2. Also, the second end of the inductor L2 is connected to the negative electrode of the smoothing capacitor C3.

[0069] A light source module 10 on which a plurality of light emitting elements 100 are mounted is connected between both electrodes (positive electrode and negative electrode) of a smoothing capacitor C3.

[0070] Also, a voltage detection circuit 277 included in a control circuit 273 is connected to the positive electrode of the smoothing capacitor C2, the cathode of the diode D2, and the smoothing capacitor C3. The voltage detection circuit 277 detects the output voltage V2.

[0071] The drive control circuit 276 controls the switching element Q2 to be turned on / off in the second drive circuit 275 in, for example, the current critical mode. Here, the current critical mode is a control method in which the switching element Q2 is turned on again when the current (regenerative current) flowing from the inductor L2 to the light source module 10 becomes zero when the switching element Q2 is off.

[0072] When the switching element Q2 is on, a current Iout flows through a path from the positive electrode of the smoothing capacitor C2, through the light source module 10 and the inductor L2, and toward the negative electrode of the smoothing capacitor C2. By this current Iout, magnetic energy is stored in the inductor L2.

[0073] The second drive circuit 275 turns off the switching element Q2 when the magnitude of the current Iout reaches a target value. Here, for detecting the magnitude of the current Iout when the switching element Q2 is on, for example, the voltage across both ends of a resistance element connected between the source of the switching element Q2 and the ground may be used for detection.

[0074] When the switching element Q2 is turned off, the magnetic energy of the inductor L2 is released, and the current Iout is supplied from the first end of the inductor L2, through the diode D2, to the light source module 10.

[0075] Also, when the current Iout becomes zero, the second drive circuit 275 turns on the switching element Q2 again. Here, for detecting the magnitude of the current Iout when the switching element Q2 is off, for example, the voltage across both ends of a resistance element connected between the first end of the inductor L2 and the anode of the diode D2 may be used for detection.

[0076] By the second drive circuit 275 switching the switching element Q2 as described above, the magnitude of the current Iout flowing through the light source module 10 can be made to match the target value. That is, the second circuit 272 can supply a constant current to the light source module 10.

[0077] The communication unit 278 is a communication module that receives a dimming signal Sig1 transmitted from the outside (such as a remote controller). The dimming signal Sig1 is, for example, an infrared signal. The dimming signal Sig1 instructs the lighting / extinguishing of the light source module 10. Also, the dimming signal Sig1 instructs the target value of the magnitude of the current Iout. That is, the dimming signal Sig1 instructs the target value of the brightness of the light source module 10.

[0078] (2-3-1) Operation example of the power supply device in the standby mode Next, an operation example of the power supply device 2 when the lighting fixture A1 is in the standby mode will be described. Here, the standby mode is a mode in which the light source module 10 is maintained in the extinguished state with an AC voltage Vac input from the power supply PS to the rectifier circuit 270.

[0079] When the communication unit 278 receives a dimming signal Sig1 instructing the stop of the supply of the constant current from the second circuit 272 to the light source module 10, the lighting fixture A1 enters the standby mode.

[0080] When the lighting fixture A1 enters the standby mode, the drive control circuit 276 of the control circuit 273 stops the high-frequency switching operation of the switching element Q2 of the second circuit 272 and stops the supply of the constant current to the light source module 10. When the drive control circuit 276 stops the supply of the constant current, the light source module 10 is extinguished.

[0081] Further, when the drive control circuit 276 is instructed by the dimming signal Sig1 to stop the supply of the constant current from the second circuit 272 to the light source module 10, the drive control circuit 276 intermittently performs a high-frequency switching operation on the switching element Q1 of the first circuit 271. More specifically, when the drive control circuit 276 is instructed by the dimming signal Sig1 to stop the supply of the constant current from the second circuit 272 to the light source module 10, the drive control circuit 276 causes the switching element Q1 to perform a high-frequency switching operation according to the output voltage V2 detected by the voltage detection circuit 277. When the output voltage V2 exceeds a predetermined threshold value (first threshold value), the drive control circuit 276 stops the high-frequency switching operation of the switching element Q1. Here, "exceeding the predetermined first threshold value" means, for example, that the output voltage V2 reaches a first voltage that is equal to or higher than the first threshold value. Thereafter, when the output voltage V2 decreases and falls below the first threshold value, the drive control circuit 276 causes the switching element Q1 to perform a high-frequency switching operation. Here, "falling below the predetermined first threshold value" means, for example, that the output voltage V2 reaches a second voltage that is lower than the first threshold value. Thereby, the value of the output voltage V2 is maintained at a value close to the first threshold value. Here, the first threshold value is set to be higher than 0V and lower than the value of the output voltage V2 when the light source module 10 is lit.

[0082] In this way, in the standby mode, the drive control circuit 276 intermittently performs a high-frequency switching operation on the switching element Q1, that is, stops the high-frequency switching operation of the switching element Q1 for at least a certain period. Thereby, corrosion of the semiconductor including silicon carbide, which is the material of the switching element Q1, due to the high-frequency switching operation of the switching element Q1 can be suppressed. Further, since the value of the output voltage V2 is maintained at a value close to the first threshold value, when the supply of the constant current from the second circuit 272 to the light source module 10 is instructed to start by the dimming signal Sig1, the supply of the constant current from the second circuit 272 to the light source module 10 can be quickly resumed.

[0083] (2-4) Support member As shown in FIGS. 1 and 2, the support member 3 includes a fixing portion 30, a pair of arm portions 31 that rise obliquely upward from both left and right ends of the fixing portion 30, and a mounting portion 32 provided at the tips (upper ends) of the pair of arm portions 31. However, the support member 3 integrally forms the fixing portion 30, the pair of arm portions 31, and the pair of mounting portions 32 by processing a metal plate.

[0084] The fixing portion 30 is fixed to a pedestal Z1 (see FIG. 1), which is a surface to be fixed, using bolts or the like.

[0085] The pair of arm portions 31 rise obliquely upward and forward from both left and right ends of the fixing portion 30. A mounting portion 32 is integrally provided at the tip of each arm portion 31.

[0086] The pair of mounting portions 32 are respectively attached to a pair of case-side mounting portions 23 of the housing 20 using bolts or the like. For example, the left mounting portion 32 of the pair of mounting portions 32 is attached to the case-side mounting portion 23 via a display member 5. The display member 5 is a metal disc with graduations engraved thereon.

[0087] (3) Modification The above-described embodiment is merely one of various embodiments of the present disclosure. The above-described embodiment can be variously modified according to the design and the like as long as the object of the present disclosure can be achieved.

[0088] Hereinafter, modifications of the embodiment will be described. Hereinafter, the above-described embodiment may also be referred to as a "basic example". The above basic example and the modifications described below can be applied in appropriate combinations.

[0089] The drive control circuit 276 in the present disclosure includes a computer system. The computer system mainly includes a processor and a memory as hardware. By the processor executing a program recorded in the memory of the computer system, the function as the drive control circuit 276 in the present disclosure is realized. The program may be pre-recorded in the memory of the computer system, may be provided through a telecommunication line, or may be provided by being recorded on a non-transitory recording medium such as a memory card, an optical disk, or a hard disk drive that can be read by the computer system. The processor of the computer system is composed of one or more electronic circuits including a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). The integrated circuits such as the IC or LSI mentioned here have different names depending on the degree of integration, and include integrated circuits called system LSI, VLSI (Very Large Scale Integration), or ULSI (Ultra Large Scale Integration). Furthermore, for an FPGA (Field-Programmable Gate Array) that is programmed after the manufacture of the LSI, or a logic device capable of reconfiguring the bonding relationship inside the LSI or reconfiguring the circuit section inside the LSI, it can also be adopted as a processor. The plurality of electronic circuits may be integrated on one chip, or may be provided dispersedly on a plurality of chips. The plurality of chips may be integrated in one device, or may be provided dispersedly in a plurality of devices.

[0090] (Embodiment 2) In the power supply device 2 according to Embodiment 2, the circuit configuration of the power supply circuit 27 is different from that of the power supply device 2 according to Embodiment 1. Hereinafter, the power supply circuit 27 of the power supply device 2 according to Embodiment 2 is described as the power supply circuit 27a.

[0091] As shown in FIG. 5, the power supply circuit 27a includes a first circuit 271a, a second circuit 272a provided at the subsequent stage of the first circuit 271a, and a control circuit 273a.

[0092] The control circuit 273a includes a first drive circuit 274a, a second drive circuit 275a, a drive control circuit 276a, a voltage detection circuit 277a, and a communication unit 278a. The drive control circuit 276a is connected to the first drive circuit 274a, the second drive circuit 275a, the voltage detection circuit 277a, and the communication unit 278a that receives a dimming signal from the outside.

[0093] Based on the voltage detection result of the voltage detection circuit 277a and the reception result of the communication unit 278a, the drive control circuit 276a controls the first drive circuit 274a and the second drive circuit 275a. The drive control circuit 276a mainly includes a microcontroller having one or more processors and one or more memories as main components.

[0094] The first circuit 271a includes a buck circuit SD that steps down a DC voltage Vdc input from a power supply PSa, which is a DC power supply for example, to a predetermined output voltage V2a.

[0095] As shown in FIG. 5, the buck circuit SD includes a switching element Q3, a diode D3, an inductor L3, and a smoothing capacitor C4.

[0096] The switching element Q3 is, for example, an n-channel MOSFET. Note that the switching element Q3 is not limited to an n-channel MOSFET, and may be a p-channel MOSFET or an IGBT or the like. Also, similar to the switching element Q1 in Embodiment 1, the switching element Q3 includes a semiconductor chip 7 (see FIG. 4) mainly made of a semiconductor containing silicon carbide.

[0097] The drain of the switching element Q3 is connected to the positive electrode of the power supply PSa. Also, the source of the switching element Q3 is connected to the cathode of the diode D3.

[0098] The gate of the switching element Q3 is connected to the first drive circuit 274a included in the control circuit 273a. The first drive circuit 274a drives the switching element Q3 to be turned on / off by applying a gate voltage between the gate and source of the switching element Q3. More specifically, the drive control circuit 276a controls the first drive circuit 274a to drive the switching element Q3 to be turned on / off.

[0099] The anode of the diode D3 is connected to the negative electrode of the power supply PSa.

[0100] The first end of the inductor L3 is connected to the connection point between the source of the switching element Q3 and the cathode of the diode D3.

[0101] The second end of the inductor L3 is connected to the positive electrode of the smoothing capacitor C4 and the light source module 10.

[0102] The negative electrode of the smoothing capacitor C4 is connected to the anode of the diode D3 and the negative electrode of the power supply PSa. Also, the negative electrode of the smoothing capacitor C4 is connected to the light source module 10 via the second circuit 272a.

[0103] When the switching element Q3 is on, a current Iout flows through a path from the positive electrode of the power supply PSa, through the inductor L3, the light source module 10, and the second circuit 272a, to the negative electrode of the power supply PSa. Due to this current, magnetic energy is stored in the inductor L3.

[0104] When the switching element Q3 is off, the magnetic energy of the inductor L3 is released, and a current Iout flows through a path from the second end of the inductor L3, through the light source module 10, the second circuit 272a, and the diode D3, to the first end of the inductor L3.

[0105] Due to the current Iout, an output voltage V2a appears across the smoothing capacitor C4, which is a stepped-down voltage of the DC voltage Vdc input from the power supply PSa. The magnitude of the output voltage V2a is adjusted by making the duty ratio of the switching element Q3 variable.

[0106] The second circuit 272a includes a switching element Q4, an operational amplifier OP1, and a resistive element R1.

[0107] The switching element Q4 is, for example, an n-channel MOSFET. Note that the switching element Q1 is not limited to an n-channel MOSFET and may be a p-channel MOSFET or an IGBT or the like.

[0108] The drain of the switching element Q4 is connected to the light source module 10. Also, the source of the switching element Q4 is connected to the first end of the resistive element R1.

[0109] The second end of the resistive element R1 is connected to the negative electrode of the smoothing capacitor C4, the anode of the diode D3, and the negative electrode of the power supply PSa.

[0110] The output terminal of the operational amplifier OP1 is connected to the gate of the switching element Q4. The inverting input terminal of the operational amplifier OP1 is connected to the connection point between the source of the switching element Q4 and the first end of the resistive element R1. The non-inverting input terminal of the operational amplifier OP1 is connected to the second drive circuit 275a of the control circuit 273a. The second drive circuit 275a inputs a control voltage to the non-inverting input terminal of the operational amplifier OP1.

[0111] The operational amplifier OP1 adjusts the output voltage (gate voltage) to the gate of the switching element Q4 so that the voltage across the resistor element R1, which is proportional to the drain current (current Iout) of the switching element Q4, matches the control voltage. For example, if the drain current of the switching element Q4 increases, the output voltage of the operational amplifier OP1 decreases, and the on-resistance between the drain and source of the switching element Q4 increases. As a result, the drain current decreases. Also, if the drain current of the switching element Q4 decreases, the output voltage of the operational amplifier OP1 increases, and the on-resistance between the drain and source of the switching element Q4 decreases. As a result, the drain current increases. That is, the second circuit 272a can supply a constant current to the light source module 10 by matching the current Iout to a target value corresponding to the control voltage.

[0112] Also, a voltage detection circuit 277a included in the control circuit 273a is connected to the connection point between the second end of the inductor L3 and the positive electrode of the smoothing capacitor C4. The voltage detection circuit 277a detects the output voltage V2a.

[0113] The communication unit 278a is a communication module that receives a dimming signal Sig1 transmitted from the outside (such as a remote controller).

[0114] When the communication unit 278a receives a dimming signal Sig1 that instructs the stop of the supply of the constant current from the second circuit 272a to the light source module 10, the lighting fixture A1 enters the standby mode.

[0115] When the lighting fixture A1 enters the standby mode, the drive control circuit 276a turns off the switching element Q4 of the second circuit 272a to stop the supply of the constant current to the light source module 10. When the drive control circuit 276a stops the supply of the constant current, the light source module 10 turns off.

[0116] When the drive control circuit 276a is instructed by the dimming signal Sig1 to stop the supply of a constant current from the second circuit 272a to the light source module 10, the drive control circuit 276a causes the switching element Q3 to perform a high-frequency switching operation according to the output voltage V2a detected by the voltage detection circuit 277a. When the output voltage V2a exceeds a predetermined threshold value (second threshold value), the drive control circuit 276a stops the high-frequency switching operation of the switching element Q3. Here, "exceeding the predetermined second threshold value" means, for example, that the output voltage V2a reaches a first voltage that is equal to or higher than the second threshold value. Thereafter, when the output voltage V2a decreases and falls below the second threshold value, the drive control circuit 276a causes the switching element Q3 to perform a high-frequency switching operation. Here, "falling below the predetermined second threshold value" means, for example, that the output voltage V2a reaches a second voltage that is lower than the second threshold value. Thereby, the value of the output voltage V2a is maintained at a value close to the second threshold value. The second threshold value is set to be higher than 0V and lower than the value of the output voltage V2a when the light source module 10 is lit.

[0117] In this way, in the standby mode, the drive control circuit 276a intermittently performs a high-frequency switching operation on the switching element Q3, that is, stops the high-frequency switching operation of the switching element Q3 for at least a certain period. Thereby, corrosion of the semiconductor including silicon carbide, which is the material of the switching element Q3, due to the high-frequency switching operation of the switching element Q3 can be suppressed. Further, since the value of the output voltage V2a is maintained at a value close to the second threshold value, when the start of the supply of a constant current from the second circuit 272a to the light source module 10 is instructed, the drive control circuit 276a can quickly resume the supply of a constant current from the second circuit 272a to the light source module 10.

[0118] (Summary) The power supply device (2) of the first aspect includes a first circuit (271, 271a), a second circuit (272, 272a), and a control circuit (273, 273a). The first circuit (271, 271a) converts an input voltage input from a power supply (PS, PSA) into a predetermined output voltage (V2, V2a). The second circuit (272, 272a) is provided downstream of the first circuit (271, 271a) and supplies a constant current to the light source module (10). The control circuit (273, 273a) controls the first circuit (271, 271a) and the second circuit (272, 272a) according to a dimming signal (Sig1) from the outside. The first circuit (271, 271a) is made of a semiconductor containing silicon carbide and has switching elements (Q1, Q3) that perform high-frequency switching operations. When the control circuit (273, 273a) is instructed to stop supplying a constant current from the second circuit (272, 272a) to the light source module (10) by the dimming signal (Sig1), the control circuit (273, 273a) stops the high-frequency switching operation of the switching elements (Q1, Q3) of the first circuit (271, 271a) for at least a certain period.

[0119] According to this aspect, when the supply of the constant current to the light source module (10) is instructed to stop by the dimming signal (Sig1), by stopping the high-frequency switching operation of the switching elements (Q1, Q3) for at least a certain period, corrosion of the semiconductor containing silicon carbide, which is the material of the switching elements (Q1, Q3), can be suppressed. Thereby, deterioration of the performance of the switching elements (Q1, Q3) can be suppressed, and as a result, the reliability of the power supply device (2) can be improved.

[0120] In the power supply device (2) of the second aspect, in the first aspect, the first circuit (271) has a boost circuit (BC) that boosts the input voltage to the output voltage (V2). The boost circuit (BC) includes a switching element (Q1).

[0121] According to this aspect, the input voltage input from the power supply (PS) can be boosted and converted into a predetermined output voltage (V2).

[0122] In the power supply device (2) according to the third aspect, in the first aspect, the first circuit (271a) has a step-down circuit (SD) that steps down the input voltage to the output voltage (V2a). The step-down circuit (SD) includes a switching element (Q3).

[0123] According to this aspect, the input voltage input from the power supply (PSa) can be stepped down and converted into a predetermined output voltage (V2a).

[0124] In the power supply device (2) according to the fourth aspect, in any of the first to third aspects, the switching elements (Q1, Q3) have a conduction part (Cn1) through which current flows in response to a high-frequency switching operation, and a guard ring part (G1) provided around the conduction part (Cn1).

[0125] According to this aspect, the guard ring part (G1) can mitigate the electric field concentration around the conduction part (Cn1).

[0126] In the power supply device (2) according to the fifth aspect, in the fourth aspect, the switching elements (Q1, Q3) are made of polyimide and further have a protective film (73) that covers at least the guard ring part (G1).

[0127] According to this aspect, corrosion of the guard ring part (G1) can be suppressed.

[0128] In the power supply device (2) according to the sixth aspect, in any of the first to fifth aspects, when the control circuits (273, 273a) are instructed to stop the supply of a constant current from the second circuit (272, 272a) to the light source module (10) by the dimming signal (Sig1), the switching elements (Q1, Q3) of the first circuit (271, 271a) are made to perform a high-frequency switching operation intermittently.

[0129] According to this aspect, while maintaining the output voltages (V2, V2a) of the first circuit (271, 271a) at a predetermined value, degradation of the performance of the switching elements (Q1, Q3) can be suppressed.

[0130] In the power supply device (2) of the seventh aspect, in the sixth aspect, when the control circuit (273, 273a) is instructed to stop the supply of a constant current from the second circuit (272, 272a) to the light source module (10) by the dimming signal (Sig1), if the output voltage (V2, V2a) exceeds a predetermined threshold value, the switching element (Q1, Q3) is stopped from performing a high-frequency switching operation, and if the output voltage (V2, V2a) is below the threshold value, the switching element (Q1, Q3) is made to perform a high-frequency switching operation.

[0131] According to this aspect, it is possible to suppress a decrease in the performance of the switching element (Q1, Q3) while maintaining the output voltage (V2, V2a) of the first circuit (271, 271a) at a value close to the threshold value.

[0132] The lighting fixture (A1) of the eighth aspect includes the power supply device (2) of any one of the first to seventh aspects and the light source module (10).

[0133] According to this aspect, when the supply of a constant current to the light source module (10) is instructed to stop by the dimming signal (Sig1), by stopping the high-frequency switching operation of the switching element (Q1, Q3) for at least a certain period, corrosion of the semiconductor including silicon carbide, which is the material of the switching element (Q1, Q3), can be suppressed. As a result, a decrease in the performance of the switching element (Q1, Q3) can be suppressed, and thus, the reliability of the lighting fixture (A1) can be improved.

[0134] Note that the second to seventh aspects are not essential configurations of the power supply device (2) and can be omitted as appropriate.

Explanation of Reference Numerals

[0135] 2 Power supply device 10 Light source module 73 Protective film 271, 271a First circuit 272, 272a Second circuit 273, 273a Control circuit A1 Lighting fixture BC Boost Circuit Cn1 Conductive Part G1 Guard Ring Part PS, PSa Power Supply Q1, Q3 Switching Elements SD Buck Circuit Sig1 Dimming Signal V2, V2a Output Voltage

Claims

1. A first circuit that converts an input voltage input from a power source into a predetermined output voltage; A second circuit provided at a subsequent stage of the first circuit and supplying a constant current to a light source module; A control circuit that controls the first circuit and the second circuit in response to a dimming signal from the outside, comprising: The first circuit is made of a semiconductor containing silicon carbide and has a switching element that performs a high-frequency switching operation; When the control circuit is instructed to stop supplying the constant current from the second circuit to the light source module by the dimming signal, the control circuit stops the high-frequency switching operation of the switching element in the first circuit for at least a certain period; A power supply device.

2. The first circuit has a boost circuit that boosts the input voltage to the output voltage; The boost circuit includes the switching element; The power supply device according to claim 1.

3. The first circuit has a buck circuit that steps down the input voltage to the output voltage; The buck circuit includes the switching element; The power supply device according to claim 1.

4. The switching element: Has a conduction portion through which current flows in response to the high-frequency switching operation; And a guard ring portion provided around the conduction portion; The power supply device according to any one of claims 1 to 3.

5. The switching element is made of polyimide and further has a protective film that covers at least the guard ring portion; The power supply device according to claim 4.

6. When the control circuit is instructed to stop supplying the constant current from the second circuit to the light source module by the dimming signal, the control circuit causes the switching element in the first circuit to perform the high-frequency switching operation intermittently; The power supply device according to any one of claims 1 to 3.

7. When the control circuit is instructed to stop supplying the constant current from the second circuit to the light source module by the dimming signal, When the output voltage exceeds a predetermined threshold value, the control circuit stops the high-frequency switching operation of the switching element; When the output voltage is lower than the threshold value, the control circuit causes the switching element to perform the high-frequency switching operation; The power supply device according to claim 6.

8. An illumination device comprising: the power supply device according to any one of claims 1 to 3; and The light source module. An illumination device.

Images