Lighting device and lighting fixture

Abstract

To suppress flicker at a time of turning off a circuit component while downsizing a circuit component.SOLUTION: A lighting device 4 includes an AC / DC conversion unit 410, a first control unit 411, a control power supply unit 412, a DC conversion unit 420, and a second control unit 421. The AC / DC conversion unit 410 includes a choke coil L1. The control power supply unit 412 includes an auxiliary winding L2 magnetically coupled to the choke coil L1. The first control unit 411 controls a switching element Q1 to make a voltage across a smoothing capacitor C1 constant when an AC voltage Vac is supplied. When it is detected that a supply of the AC voltage Vac is stopped based on the voltage induced in an auxiliary winding L2, the second control unit 421 controls the DC conversion unit 420 to stop the output of the second DC voltage V2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a lighting device and a lighting fixture, and more particularly to a lighting device that supplies DC power to light a light source, and a lighting fixture that includes the lighting device. [Background technology]

[0002] Conventionally, in lighting fixtures that use LEDs as light sources, a lighting device that lights the light source includes an AC / DC conversion circuit that converts AC power supplied from an AC power source such as a commercial power source into DC power. Such AC / DC conversion circuits are configured with switching power supply circuits such as a flyback converter or a buck-boost converter (see, for example, Patent Document 1).

[0003] The switching power supply circuit includes a semiconductor switching element, a choke coil, a diode, a smoothing capacitor, etc. The switching power supply circuit also includes a drive circuit that switches the semiconductor switching element.

[0004] The output stage of a switching power supply circuit is usually provided with a smoothing electrolytic capacitor, so immediately after the AC power supply is stopped, the light source may emit light for a short period of time due to the charge stored in the electrolytic capacitor (hereinafter, this may be referred to as "flickering when the light is off").

[0005] In order to avoid the above-mentioned flickering when the light is turned off, conventional lighting devices immediately stop supplying DC power to the light source when they detect an interruption in the power supply from the AC power source, thereby turning off the light source. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-110696 Summary of the Invention [Problem to be solved by the invention]

[0007] Conventional lighting devices have a first auxiliary winding and a second auxiliary winding magnetically coupled to a choke coil of a switching power supply circuit. The voltage induced in the first auxiliary winding is used to power the driving circuit of the switching power supply circuit. The voltage induced in the second auxiliary winding is used to detect an interruption in the power supply from the AC power supply.

[0008] However, in conventional lighting devices, the circuit components, including the choke coil and two auxiliary windings, are large and the number of leads is increased, making it difficult to secure space for mounting them on a printed wiring board.

[0009] An object of the present disclosure is to provide a lighting device and a lighting fixture that can reduce flickering when the light is off while miniaturizing circuit components. [Means for solving the problem]

[0010] A lighting device according to one aspect of the present disclosure includes an AC / DC converter, a first control unit, a control power supply unit, a DC converter, and a second control unit. The AC / DC converter converts AC voltage supplied from an external power supply into a first DC voltage. The first control unit controls the AC / DC converter. The control power supply unit generates a control voltage for operating the first control unit. The DC converter converts the first DC voltage into a second DC voltage supplied to a light source. The second control unit controls the DC converter. The AC / DC converter includes a choke coil, a switching element that switches on and off the current supplied to the choke coil from the external power supply, a diode that rectifies a voltage induced in the choke coil, and a smoothing capacitor that smoothes the voltage rectified by the diode. The control power supply unit includes an auxiliary winding magnetically coupled to the choke coil and a constant voltage unit that constant-voltage-regulates the voltage induced in the auxiliary winding. The first control unit controls the switching element to maintain a constant voltage across the smoothing capacitor when the AC voltage is being supplied, and the second control unit controls the DC conversion unit to stop outputting the second DC voltage when detecting that the supply of the AC voltage has stopped based on the voltage induced in the auxiliary winding.

[0011] A lighting fixture according to one aspect of the present disclosure includes the lighting device and a light source that is turned on by the lighting device. [Effects of the Invention]

[0012] The lighting device and lighting fixture of the present disclosure have the advantage of being able to reduce the size of circuit components while suppressing flickering when the light is off. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a circuit diagram of a lighting device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a perspective view of a lighting fixture according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is an exploded perspective view of the lighting fixture. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, lighting devices and lighting fixtures according to embodiments of the present disclosure will be described in detail with reference to the drawings. However, the drawings described in the following embodiments are schematic diagrams, and the ratios of the sizes and thicknesses of the 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 are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0015] (1) Overview The lighting device 4 according to the embodiment includes an AC / DC converter 410, a first control unit 411, a control power supply unit 412, a DC converter 420, and a second control unit 421 (see FIG. 1).

[0016] The AC / DC converter 410 converts an AC voltage Vac supplied from an external power source (for example, a commercial power system) into a first DC voltage V1. The first control unit 411 controls the AC / DC converter 410. The control power supply unit 412 generates a control voltage for operating the first control unit 411.

[0017] The DC converter 420 converts the first DC voltage V1 into a second DC voltage V2 that is supplied to the light source (LED 20). The second controller 421 controls the DC converter 420.

[0018] The AC / DC converter 410 includes a choke coil L1, a switching element Q1 that switches on and off the current supplied to the choke coil L1 from an external power supply, a diode D1 that rectifies the voltage induced in the choke coil L1, and a smoothing capacitor C1 that smoothes the voltage rectified by the diode D1. That is, the AC / DC converter 410 includes a step-up / step-down chopper circuit (buck-boost converter).

[0019] The control power supply unit 412 includes an auxiliary winding L2 magnetically coupled to the choke coil L1, and a constant voltage unit 413 that constant-voltages the voltage induced in the auxiliary winding L2. The constant voltage unit 413 includes, for example, a Zener diode.

[0020] The first control unit 411 controls the switching element Q1 to make the voltage across the smoothing capacitor C1 constant when the AC voltage Vac is supplied. The second control unit 421 controls the DC conversion unit 420 to stop outputting the second DC voltage V2 when it detects that the supply of the AC voltage Vac has stopped based on the voltage induced in the auxiliary winding L2.

[0021] In other words, when the lighting device 4 according to the embodiment detects that the supply of the AC voltage Vac has stopped based on the voltage induced in the auxiliary winding L2, it causes the second control unit 421 to control the DC conversion unit 420 to stop outputting the second DC voltage V2, thereby suppressing flickering when the light is turned off.

[0022] Here, if the control power supply unit 412 provides an auxiliary winding for detecting the cessation of the supply of AC voltage Vac in addition to the auxiliary winding L2 for generating the control voltage, this will result in an increase in the size of the circuit components including the choke coil L1 and the two auxiliary windings and an increase in the number of leads.

[0023] In contrast, lighting device 4 according to the embodiment causes second control unit 421 to detect that the supply of AC voltage Vac has stopped based on the voltage induced in auxiliary winding L2 for generating the control voltage. As a result, lighting device 4 according to the embodiment can reduce flickering when the light is off while miniaturizing circuit components.

[0024] Furthermore, the lighting fixture A1 according to the embodiment includes the lighting device 4 according to the embodiment and a light source (LED 20) that is turned on by the lighting device 4 according to the embodiment (see FIG. 3).

[0025] Thus, the lighting fixture A1 according to the embodiment includes the lighting device 4 according to the embodiment, and therefore, it is possible to reduce the size of the circuit components and suppress flickering when the light is turned off.

[0026] (2)Details A lighting device 4 according to the embodiment (hereinafter simply referred to as lighting device 4) is configured to light a light source (LED 20) included in a lighting fixture A1 according to the embodiment.

[0027] (2-1) Lighting equipment The lighting fixture A1 according to the embodiment (hereinafter simply referred to as lighting fixture A1) is a so-called spotlight that is detachably attached to a lighting wiring duct (also referred to as a lighting duct) (see FIG. 2). However, the lighting fixture A1 is not limited to a spotlight that is detachably attached to a lighting wiring duct. In the following description, the front-rear, left-right, and up-down directions of the lighting fixture A1 are defined in a state in which the axial direction (longitudinal direction) of the fixture body 1 and the longitudinal direction of the arm 5 are perpendicular to each other, as shown in FIG. 2. That is, the longitudinal direction of the arm 5 is defined as the up-down direction, the axial direction of the fixture body 1 (the direction perpendicular to the longitudinal direction of the arm 5) is defined as the front-rear direction, and the direction perpendicular to the up-down direction and the front-rear direction is defined as the left-right direction (see the arrows in FIG. 2).

[0028] The lighting fixture A1 comprises a lighting fixture B1, an arm 5, and a plug unit 8 (see Figure 2). The plug unit 8 is mechanically, electrically, and detachably attached to a lighting wiring duct installed on a ceiling or the like. The arm 5 is rotatably attached to the bottom of the plug unit 8. The rotation axis of the arm 5 is parallel to the vertical direction. The lighting fixture B1 is supported by the arm 5 so that it can rotate within a plane that includes the vertical and front-to-back directions. However, the rotation range of the lighting fixture B1 is within a range of approximately 90 degrees from a position (see Figure 2) where the axial direction of the fixture body 1 is perpendicular to the longitudinal direction (vertical direction) of the arm 5 to a position where the axial direction of the fixture body 1 is parallel to the longitudinal direction (vertical direction) of the arm 5.

[0029] (2-2) Lighting equipment The lighting fixture B1 includes a fixture body 1, a light source unit 2, a lens unit 3, a lighting device 4, an end cover 6, etc. (see FIGS. 2 and 3).

[0030] (2-3) Device body The appliance body 1 has a first body portion 11 and a second body portion 12. The first body portion 11 and the second body portion 12 are each formed by aluminum alloy die-casting into a cylindrical shape with both ends open. The first body portion 11 and the second body portion 12 have the same diameter but different axial lengths. The second body portion 12 is formed to have a longer axial length than the first body portion 11. However, the first body portion 11 and the second body portion 12 are not limited to being aluminum alloy die-casting, and may be formed from other metals, synthetic resins, or the like.

[0031] A rectangular slit 120 is formed in the second main body portion 12 from the rear end to the center in the axial direction. The width (left-right distance) of the slit 120 is wider than the width of the arm 5 (see FIG. 2).

[0032] (2-4) Light source unit The light source unit 2 includes an LED 20 as a light source, a holder 21, a pair of connectors 22, a heat conduction sheet, and a unit body 24 (see FIG. 3).

[0033] The LED 20 is a COB (Chip on Board) type white LED for illumination. However, the light source is not limited to an LED, and may be an organic electroluminescence element, a semiconductor laser element, or the like.

[0034] The unit body 24 is formed into a disk shape by die-casting an aluminum alloy, but the material of the unit body 24 is not limited to die-casting an aluminum alloy, and it may be formed from other metals or synthetic resins.

[0035] A rectangular recess is provided in the center of the front surface of unit body 24. A rectangular heat conduction sheet is housed in this recess. Also, a screw insertion hole 241 and a screw hole 242 are provided on both the left and right ends of unit body 24 (see FIG. 3).

[0036] A holder 21 for holding the LED 20 is attached to the front of the unit body 24. The holder 21 is made of synthetic resin and is formed in the shape of a frame with a square window in the center. The holder 21 holds the LED 20 by fitting it into the window. However, the holder 21 may be made of a material other than synthetic resin, such as metal or ceramic. The LED 20 held by the holder 21 and attached to the unit body 24 is thermally connected to the unit body 24 via the thermal conduction sheet by being in close contact with the thermal conduction sheet.

[0037] (2-5) Lens unit The lens unit 3 includes a lens, a lens holder, a cover 32, a rotor 33, and the like (see FIG. 3).

[0038] The lens is a Fresnel lens made of a light-transmitting synthetic resin such as silicone resin, acrylic resin, polycarbonate resin, etc. However, the lens may be made of a material other than synthetic resin, such as inorganic glass.

[0039] The lens holder is made of synthetic resin and has a circular shape, and holds the lens by surrounding the lens.

[0040] The cover 32 is formed in a disk shape from a translucent synthetic resin such as an acrylic resin. The cover 32 is attached to the rotor 33 as described below. The cover 32 covers the front surface of the rotor 33 to prevent insects from entering the rotor 33 (see FIG. 2).

[0041] The rotor 33 has a cylindrical portion and an annular operating portion 331 provided at the front end of the cylindrical portion (see FIG. 2). A lens and a lens holder are housed inside the cylindrical portion.

[0042] The lens unit 3 is housed in the first body portion 11 of the device main body 1, as will be described later (see FIGS. 2 and 3). Here, the lens unit 3 moves back and forth within the cylindrical portion by operating the operating portion 331 to rotate the rotor 33. In other words, the lens unit 3 can adjust the irradiation range of the light emitted from the LED 20 and collected by the lens by operating the operating portion 331 to change the relative distance between the LED 20 and the lens.

[0043] (2-6) Structure of lighting device The lighting device 4 has an AC / DC conversion block 4A and a DC conversion block 4B (see FIG. 3).

[0044] The AC / DC conversion block 4A has an AC / DC conversion unit 410 that converts AC voltage (AC power) supplied from an external power source via the lighting wiring duct and plug unit 8 into DC voltage (DC power). The AC / DC conversion unit 410 is composed of a first printed circuit board 41 having a plurality of circuit components mounted on a double-sided printed wiring board. The AC / DC conversion block 4A also has a first heat sink 43 to which the first printed circuit board 41 is attached, and a first heat conduction member 45 interposed between the first printed circuit board 41 and the first heat sink 43 (see FIG. 3).

[0045] The first heat sink 43 is formed into a flat plate shape using a metal plate (for example, an aluminum plate) that is a good conductor of heat. The first heat conduction member 45 is formed, for example, from a silicone rubber sheet material that has excellent thermal conductivity and electrical insulation properties. Three female threads are provided on the first heat sink 43. The AC / DC conversion block 4A is assembled by placing the first heat conduction member 45 on the surface of the first heat sink 43, and then placing the first printed circuit board 41 on the surface of the first heat conduction member 45, and then screwing three mounting screws into the three female threads one by one.

[0046] The DC conversion block 4B has a DC conversion unit 420 that converts (steps down) the DC voltage output from the AC / DC conversion block 4A into a DC voltage suitable for the LEDs 20. The DC conversion unit 420 is composed of a second printed circuit board 42, which is a double-sided printed wiring board on which multiple circuit components are mounted. The DC conversion block 4B also has a second heat sink 44 to which the second printed circuit board 42 is attached, and a second heat conduction member 46 interposed between the second printed circuit board 42 and the second heat sink 44 (see FIG. 3).

[0047] The second heat sink 44 is formed into a rectangular shape from a metal plate (for example, an aluminum plate) that is a good conductor of heat. A pair of bent portions is provided at one longitudinal end of the second heat sink 44. A protruding piece is provided between the pair of bent portions. A female screw is provided at each of the corners of the second heat sink 44 and on the protruding piece.

[0048] The second heat conduction member 46 is formed of, for example, a silicone rubber sheet material that has excellent thermal conductivity and electrical insulation. The DC conversion block 4B is assembled by placing the second heat conduction member 46 on the surface of the second heat sink 44, and then placing the second printed circuit board 42 on the surface of the second heat conduction member 46, and screwing two mounting screws into the two female threads (see FIG. 3).

[0049] (2-7) End cover The end cover 6 has a cover plate 60, an attachment portion 61, a first boss 64, and a second boss 65 (see FIG. 3). The cover plate 60, the attachment portion 61, the first boss 64, and the second boss 65 are integrally formed by aluminum alloy die-casting.

[0050] The mounting portion 61 is configured to rotatably mount the arm 5 to the end cover 6. Two screw holes 610 are provided on the front surface of the mounting portion 61, spaced apart in the left-right direction (see FIG. 3). That is, the AC-DC conversion block 4A is mounted to the end cover 6 by screwing the first heat sink 43 into these two screw holes 610. Furthermore, recesses 611 are provided on both ends of the mounting portion 61 in the left-right direction. Each recess 611 has one screw hole 612 provided in the bottom surface (see FIG. 3).

[0051] The first boss 64 is formed in a roughly pyramidal shape. The first boss 64 is formed integrally with the cover plate 60 so as to protrude forward from the lower end of the front surface of the cover plate 60 (see FIG. 3). A screw hole 640 is formed in the tip surface (front surface) of the first boss 64. The second boss 65 is formed in a roughly prismatic shape. The second boss 65 is formed integrally with the cover plate 60 so as to protrude forward from both sides of the first boss 64 at the lower end of the front surface of the cover plate 60. Two screw holes 650 are formed in the tip surface (front surface) of the second boss 65. These two screw holes 650 are provided one on each side of the first boss 64 when viewed from the front (see FIG. 3).

[0052] The DC conversion block 4B is attached to the second boss 65. That is, two screws are inserted one by one into the screw insertion holes in a pair of cut-and-raised portions of the second heat sink 44, and then screwed into the two screw holes one by one, thereby fixing the second heat sink 44 to the end cover 6.

[0053] The end cover 6 is attached to the second main body portion 12 by being screwed into the screw hole 640 of the first boss 64 and the two screw holes 612 of the attachment portion 61 .

[0054] (2-8) Circuit configuration of lighting device As described above, the lighting device 4 has an AC / DC conversion block 4A and a DC conversion block 4B (see FIG. 1).

[0055] (2-8-1) Circuit configuration of AC / DC conversion block The AC / DC conversion block 4A has a pair of first input terminals T11, T12, a full-wave rectifier 414, an AC / DC conversion unit 410, a first control unit 411, a constant voltage unit 413, and three first output terminals T21, T22, and T23.

[0056] The pair of first input terminals T11, T12 are electrically connected to an external power supply and receive an AC voltage Vac from the external power supply. The full-wave rectifier 414 is, for example, a diode bridge. The full-wave rectifier 414 full-wave rectifies the AC voltage Vac applied to the pair of first input terminals T11, T12.

[0057] The AC / DC converter 410 includes a switching element Q1, a choke coil L1, a diode D1, and a smoothing capacitor C1. The switching element Q1 is an enhancement-type N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor). However, the switching element Q1 may be a semiconductor switching element other than a MOSFET, such as a bipolar transistor. The drain of the switching element Q1 is electrically connected to the high-potential output terminal of the full-wave rectifier 414. The source of the switching element Q1 is electrically connected to the cathode of the diode D1 and one end (winding start) of the choke coil L1. The other end (winding end) of the choke coil L1 is electrically connected to the low-potential output terminal of the full-wave rectifier 414 and the positive terminal of the smoothing capacitor C1. The anode of the diode D1 is electrically connected to the negative terminal of the smoothing capacitor C1. The positive terminal of the smoothing capacitor C1 is electrically connected to the first output terminal T22, and the negative terminal of the smoothing capacitor C1 is electrically connected to the first output terminal T21.

[0058] That is, the AC / DC conversion unit 410 is configured as a step-up / step-down chopper circuit (buck-boost converter) that can boost the pulsating voltage input from the full-wave rectifier 414 to a voltage higher than its peak value and can lower the voltage to a voltage lower than its peak value. However, the AC / DC conversion unit 410 has an output voltage (first DC voltage V1) whose polarity is inverted with respect to the input voltage (pulsating voltage). That is, the first output terminal T22 has a higher potential than the first output terminal T21.

[0059] The first control unit 411 turns on and off the switching element Q1 by switching the gate-source voltage of the switching element Q1 between high and low. The first control unit 411 is an integrated circuit configured to perform PWM (pulse width modulation) control on the switching element Q1 so that the voltage across the smoothing capacitor C1 (first DC voltage V1) matches a target value.

[0060] The control power supply unit 412 generates a control voltage for operating the first control unit 411. The control power supply unit 412 has an auxiliary winding L2 magnetically coupled to the choke coil L1, and a constant voltage unit 413 that constant-voltages the voltage induced in the auxiliary winding L2. A first end (winding end) of the auxiliary winding L2 is electrically connected to the constant voltage unit 413. A second end (winding beginning) of the auxiliary winding L2 is electrically connected to the cathode of the diode D1. The constant voltage unit 413 has, for example, a capacitor and a Zener diode electrically connected in parallel. The control power supply unit 412 is configured so that the voltage induced in the auxiliary winding L2 in response to switching of the switching element Q1 is constant-voltage using the constant voltage unit 413.

[0061] Here, a first end of the auxiliary winding L2 is electrically connected to a first output terminal T23 via one or more resistors R1 and R2 (two in the illustrated example). That is, a voltage (hereinafter referred to as a first detection voltage Vx) obtained by dividing the sum of the voltage induced in the auxiliary winding L2 and the forward voltage of the diode D1 by two resistors R1 and R2 and three resistors R3, R4, and R5 (described later) of the DC conversion block 4B is applied between the first output terminals T21 and T23. Here, when the voltage induced in the auxiliary winding L2 is VL2, the forward voltage of the diode D1 is VD1, and the resistance values ​​of the five resistors R1, R2, R3, R4, and R5 are r1, r2, r3, r4, and r5, the first detection voltage Vx is expressed by the following equation 1:

[0062] Vx=(VL2+VD1)×(r3+r4+r5) / (r1+r2+r3+r4+r5)...Formula 1

[0063] (2-8-2) Circuit configuration of DC conversion block The DC conversion block 4B has three second input terminals T31, T32, and T33, a DC conversion unit 420, a second control unit 421, a plurality of (three in the illustrated example) resistors R3, R4, and R5, a peak hold unit 422, and a pair of second output terminals T41 and T42. Although not shown, the DC conversion block 4B has a circuit that generates an operating power supply for the DC conversion unit 420 and the second control unit 421 by stepping down and stabilizing the first DC voltage V1 supplied from the AC-DC conversion block 4A.

[0064] The second input terminal T31 is electrically connected to the first output terminal T22 on the high potential side via an electric wire. The second input terminal T32 is electrically connected to the first output terminal T21 on the low potential side via an electric wire. The second input terminal T33 is electrically connected to the first output terminal T23 via an electric wire.

[0065] The DC converter 420 converts the first DC voltage V1 input to the two second input terminals T31 and T32 into a second DC voltage V2. The second DC voltage V2 is lower than the first DC voltage V1.

[0066] The DC conversion unit 420 has a switching circuit unit 423, a diode D2, a choke coil L3, and a smoothing capacitor C2. The switching circuit unit 423 has an LED driver IC in which a switching element Q2, a logic circuit 4230 that controls the switching of the switching element Q2, and the like are integrated into a single package. Note that an LED driver IC manufactured by Infineon Technologies (model number: ILD8150E), for example, is suitable as such an LED driver IC.

[0067] The switching element Q2 is an enhancement-type N-channel MOSFET. The drain of the switching element Q2 is electrically connected to the second input terminal T31. The source of the switching element Q2 is electrically connected to the cathode of the diode D2 and a first end (winding start) of the choke coil L3. The second end (winding end) of the choke coil L3 is electrically connected to the positive terminal of the smoothing capacitor C2. The anode of the diode D2 and the negative terminal of the smoothing capacitor C2 are electrically connected to the second input terminal T32. The second output terminal T41 is electrically connected to the positive terminal of the smoothing capacitor C2, and the second output terminal T42 is electrically connected to the negative terminal of the smoothing capacitor C2. That is, the DC conversion unit 420 is configured as a step-down chopper circuit (buck converter) and steps down the first DC voltage V1 to a second DC voltage V2. The second DC voltage V2 is a voltage equal to or higher than the voltage required to light the LED 20.

[0068] The logic circuit 4230 turns the switching element Q2 on and off by switching the gate-source voltage of the switching element Q2 between high and low. The logic circuit 4230 PWM controls the switching element Q2 so that the current flowing from the second output terminals T41 and T42 to the LED 20 matches a target value. The logic circuit 4230 can change the target value in response to a dimming signal input from an external device.

[0069] Furthermore, the logic circuit 4230 is configured to stop the switching of the switching element Q2 and immediately turn off the switching element Q2 when a shutdown signal is input from the outside.

[0070] The three resistors R3, R4, and R5 are electrically connected in series between the two second input terminals T33 and T32. The first end of the resistor R3 is electrically connected to the second input terminal T33, and the second end of the resistor R5 is electrically connected to the second input terminal T32. The first end of the resistor R4 is electrically connected to the second end of the resistor R3, and the second end of the resistor R4 is electrically connected to the first end of the resistor R5. The three resistors R3, R4, and R5 divide the first detection voltage Vx input to the two second input terminals T32 and T33. In other words, the three resistors R3, R4, and R5, together with the two resistors R1 and R2 of the AC-DC conversion block 4A, form a voltage divider that divides the voltage induced in the auxiliary winding L2.

[0071] The peak hold unit 422 has a diode D3, a capacitor C3, and a resistor R6. The anode of the diode D3 is electrically connected to the connection point of the two resistors R4 and R5. The cathode of the diode D3 is electrically connected to a first end of the resistor R6 and a first end of the capacitor C3. The second end of the resistor R6 and a second end of the capacitor C3 are electrically connected to the second input terminal T32. In other words, the peak hold unit 422 is configured to hold the peak value of the voltage across the resistor R5 as the voltage across the capacitor C3 (hereinafter referred to as the second detection voltage Vxx). The second detection voltage Vxx is expressed by the following equation 2:

[0072] Vxx=(VL2+VD1)×r5 / (r1+r2+r3+r4+r5)...Formula 2

[0073] The second control unit 421 is configured as an integrated circuit. The second control unit 421 converts the analog second detection voltage Vxx received from the input port into a digital value. The second control unit 421 compares the digital value of the second detection voltage Vxx with a threshold value, and determines that the supply of the AC voltage Vac has stopped when the digital value is less than the threshold value. In other words, the second control unit 421 is configured to detect that the supply of the AC voltage Vac has stopped based on the voltage induced in the auxiliary winding L2 (second detection voltage Vxx).

[0074] When the second control unit 421 detects that the supply of the AC voltage Vac has stopped, it outputs a shutdown signal to the switching circuit unit 423 to immediately stop the DC conversion unit 420. As a result, the lighting device 4 can suppress the phenomenon (flickering when turned off) in which the LED 20 emits light for only a short time due to the charge stored in the smoothing capacitor C1 of the AC / DC conversion unit 410 after the supply of the AC voltage Vac has stopped.

[0075] (3) Advantages of the embodiment As described above, when the lighting device 4 detects that the supply of the AC voltage Vac has stopped based on the voltage induced in the auxiliary winding L2 of the choke coil L1, the lighting device 4 immediately stops switching the switching element Q2. As a result, the lighting device 4 can suppress flickering when the light is turned off due to the stop of the supply of the AC voltage Vac.

[0076] Here, if the control power supply unit 412 provides an auxiliary winding for detecting the cessation of the supply of AC voltage Vac in addition to the auxiliary winding L2 for generating the control voltage, this will result in an increase in the size of the circuit components including the choke coil L1 and the two auxiliary windings and an increase in the number of leads.

[0077] In response to this, lighting device 4 causes second control unit 421 to detect that the supply of AC voltage Vac has stopped based on the voltage induced in auxiliary winding L2 for generating the control voltage. As a result, lighting device 4 has the advantage of being able to reduce the size of circuit components while suppressing flickering when the light is off.

[0078] The lighting device 4 further includes a voltage divider (resistors R1, R2, R3, R4, and R5) that divides the voltage induced in the auxiliary winding L2. The lighting device 4 then causes the second control unit 421 to detect that the supply of the AC voltage Vac has stopped based on the voltage (second detection voltage Vxx) divided by the voltage divider. For example, if the second control unit 421 is caused to detect that the supply of the AC voltage Vac has stopped without dividing the voltage induced in the auxiliary winding L2, it is necessary to reduce the turns ratio of the auxiliary winding L2 to the choke coil L1. However, reducing the turns ratio of the auxiliary winding L2 to the choke coil L1 may result in a decrease in the control voltage generated by the control power supply unit 412.

[0079] Thus, since the lighting device 4 divides the voltage induced in the auxiliary winding L2 using the voltage divider, the lighting device 4 can cause the second control unit 421 to detect that the supply of the AC voltage Vac has stopped without reducing the turns ratio of the auxiliary winding L2 to the choke coil L1. As a result, the lighting device 4 can cause the second control unit 421 to detect that the supply of the AC voltage Vac has stopped while preventing a drop in the control voltage generated by the control power supply unit 412.

[0080] The lighting device 4 also includes a peak hold unit 422 that holds the peak value of the voltage divided by the voltage divider. The second control unit 421 detects that the supply of the AC voltage Vac has stopped by comparing the peak value (second detection voltage Vxx) held by the peak hold unit 422 with a threshold value. The voltage induced in the auxiliary winding L2 (first detection voltage Vx) fluctuates depending on the on / off state of the switching element Q1. Therefore, by holding the peak value of the first detection voltage Vx in the peak hold unit 422, the lighting device 4 can allow the second control unit 421 to detect that the supply of the AC voltage Vac has stopped without being affected by fluctuations in the first detection voltage Vx.

[0081] Furthermore, the lighting device 4 causes the peak hold unit 422 to hold the peak value of the voltage across resistor R5, which has the lowest potential among the multiple resistors R1, R2, R3, R4, and R5 (see FIG. 1). Note that the resistance value of resistor R5, which has the lowest potential, is preferably the smallest among the resistance values ​​of the multiple resistors R1, R2, R3, R4, and R5. In other words, the lighting device 4 causes the peak hold unit 422 to hold the peak value of the voltage across resistor R5, which has the smallest resistance and the lowest potential, and therefore can keep the voltage input to the second control unit 421 (second detection voltage Vxx) low.

[0082] The lighting device 4 further includes a first printed circuit board 41 that forms the AC / DC converter 410, the first control unit 411, and the control power supply 412, and a second printed circuit board 42 that forms the DC converter 420 and the second control unit 421. Of the multiple resistors R1, R2, R3, R4, and R5 in the voltage divider, one or more resistors R3, R4, and R5, including the resistor R5 with the lowest potential, are provided on the second printed circuit board 42. Furthermore, the lighting device 4 includes the remaining resistors R1 and R2, excluding the one or more resistors R3, R4, and R5 with the lowest potential, on the first printed circuit board 41 (see FIG. 1). In other words, since the lighting device 4 has resistors R1 and R2 on the first printed circuit board 41 that divide the relatively high voltage (the voltage induced in the auxiliary winding L2), the voltage input to the second printed circuit board 42 (the first detection voltage Vx) can be kept low.

[0083] Here, the AC / DC converter 410 is configured as a step-up / step-down chopper circuit that can boost the pulsating voltage input from the full-wave rectifier 414 to a voltage higher than its peak value and can lower the voltage to a voltage lower than the peak value. Thus, since the lighting device 4 is equipped with the AC / DC converter 410 configured as a step-up / step-down chopper circuit, it can generate an appropriate output voltage (first DC voltage V1) with a simpler circuit configuration than when a step-up chopper circuit (boost converter) and a step-down chopper circuit are combined.

[0084] The DC conversion unit 420 is configured as a step-down chopper circuit (buck converter) and steps down the first DC voltage V1 to a second DC voltage V2. The second DC voltage V2 is a voltage equal to or higher than the voltage required to light the LEDs 20. Thus, since the lighting device 4 includes the DC conversion unit 420 configured as a step-down chopper circuit, the current supplied from the DC conversion unit 420 to the LEDs 20 can be easily adjusted.

[0085] (4) Summary A lighting device (4) according to a first aspect of the present disclosure includes an AC / DC converter (410), a first control unit (411), a control power supply unit (412), a DC converter (420), and a second control unit (421). The AC / DC converter (410) converts an AC voltage (Vac) supplied from an external power supply into a first DC voltage (V1). The first control unit (411) controls the AC / DC converter (410). The control power supply unit (412) generates a control voltage for operating the first control unit (411). The DC converter (420) converts the first DC voltage (V1) into a second DC voltage (V2) supplied to a light source (LED 20). The second control unit (421) controls the DC converter (420). The AC / DC converter (410) includes a choke coil (L1), a switching element (Q1) that switches on and off a current supplied to the choke coil (L1) from an external power supply, a diode (D1) that rectifies a voltage induced in the choke coil (L1), and a smoothing capacitor (C1) that smoothes the voltage rectified by the diode (D1). The control power supply (412) includes an auxiliary winding (L2) magnetically coupled to the choke coil (L1), and a constant voltage unit (413) that constant-voltage-regulating the voltage induced in the auxiliary winding (L2). The first control unit (411) controls the switching element (Q1) to constant-voltage the voltage across the smoothing capacitor (C1) when an AC voltage (Vac) is supplied. When the second control unit (421) detects that the supply of the AC voltage (Vac) has stopped based on the voltage induced in the auxiliary winding (L2), it controls the DC conversion unit (420) to stop outputting the second DC voltage (V2).

[0086] The lighting device (4) according to the first aspect causes the second control unit (421) to detect that the supply of the AC voltage (Vac) has stopped, based on the voltage induced in the auxiliary winding (L2) for generating the control voltage. As a result, the lighting device (4) according to the first aspect can reduce flickering when the light is off while miniaturizing the circuit components.

[0087] A lighting device (4) according to a second aspect of the present disclosure can be realized in combination with the first aspect. The lighting device (4) according to the second aspect preferably further includes a voltage divider (resistors R1, R2, R3, R4, R5) that divides the voltage induced in the auxiliary winding (L2). The second control unit (421) preferably detects that the supply of the AC voltage (Vac) has stopped based on the voltage obtained by dividing the voltage by the voltage divider.

[0088] In the lighting device (4) according to the second aspect, the voltage induced in the auxiliary winding (L2) is divided by the voltage divider, and therefore the second control unit (421) can detect that the supply of the AC voltage (Vac) has stopped without reducing the turns ratio of the auxiliary winding (L2) to the choke coil (L1). As a result, the lighting device (4) according to the second aspect can prevent a drop in the control voltage generated by the control power supply unit (412) and cause the second control unit (421) to detect that the supply of the AC voltage (Vac) has stopped.

[0089] A lighting device (4) according to a third aspect of the present disclosure can be realized in combination with the second aspect. The lighting device (4) according to the third aspect preferably further includes a peak hold unit (422) that holds a peak value of the voltage divided by the voltage divider. The second control unit (421) preferably detects that the supply of the AC voltage (Vac) has stopped by comparing the peak value held by the peak hold unit (422) with a threshold value.

[0090] The lighting device (4) according to the third aspect can cause the second control unit (421) to detect that the supply of the AC voltage (Vac) has stopped without being affected by fluctuations in the voltage divided by the voltage divider (first detection voltage Vx).

[0091] A lighting device (4) according to a fourth aspect of the present disclosure can be realized in combination with the third aspect. In the lighting device (4) according to the fourth aspect, the voltage divider preferably has a plurality of resistors (R1, R2, R3, R4, R5) electrically connected in series. The peak hold unit (422) preferably holds the peak value of the voltage across the resistor (R5) having the lowest potential among the plurality of resistors (R1, R2, R3, R4, R5). The resistance value of the resistor (R5) having the lowest potential is preferably the smallest among the resistance values ​​of the plurality of resistors (R1, R2, R3, R4, R5).

[0092] The lighting device (4) according to the fourth aspect has the peak hold unit (422) hold the peak value of the voltage across the resistor (R5) having the smallest resistance and the lowest potential, and therefore can keep the voltage (second detection voltage Vxx) input to the second control unit (421) low.

[0093] A lighting device (4) according to a fifth aspect of the present disclosure can be realized by combining it with the fourth aspect. The lighting device (4) according to the fifth aspect preferably further includes a first printed circuit board (41) that forms an AC / DC converter (410), a first control unit (411), and a control power supply unit (412), and a second printed circuit board (42) that forms a DC converter (420) and a second control unit (421). Of the multiple resistors (R1, R2, R3, R4, R5) included in the voltage divider, one or more resistors (R3, R4, R5), including the resistor (R5) with the lowest potential, are preferably provided on the second printed circuit board (42). Of the plurality of resistors (R1, R2, R3, R4, R5), it is preferable that the remaining resistors (R1, R2) except for one or more resistors (R3, R4, R5) including the resistor (R5) with the lowest potential are provided on the first printed circuit board (41).

[0094] The lighting device (4) according to the fifth aspect has resistors (R1, R2) on the first printed circuit board (41) that divide a relatively high voltage (the voltage induced in the auxiliary winding L2), and therefore can keep the voltage (first detection voltage Vx) input to the second printed circuit board (42) low.

[0095] A lighting device (4) according to a sixth aspect of the present disclosure can be realized by combining it with any one of the first to fifth aspects. In the lighting device (4) according to the sixth aspect, it is preferable that the AC / DC converter (410) has a step-up / step-down chopper circuit.

[0096] The lighting device (4) according to the sixth aspect can generate an appropriate output voltage (first DC voltage V1) with a simpler circuit configuration than when a step-up chopper circuit (boost converter) and a step-down chopper circuit are combined.

[0097] A lighting device (4) according to a seventh aspect of the present disclosure can be realized by combining it with the sixth aspect. In the lighting device (4) according to the seventh aspect, it is preferable that the DC conversion unit (420) has a step-down chopper circuit.

[0098] The lighting device (4) according to the seventh aspect includes a DC converter (420) configured with a step-down chopper circuit, and therefore can easily adjust the current supplied from the DC converter (420) to the light source.

[0099] A lighting fixture (A1) according to an eighth aspect of the present disclosure includes the lighting device (4) according to any one of the first to seventh aspects and a light source that is turned on by the lighting device (4).

[0100] The lighting fixture (A1) according to the eighth aspect includes the lighting device (4) according to any one of the first to seventh aspects, and therefore can reduce flickering when the light is off while miniaturizing the circuit components.

[0101] A lighting fixture (A1) according to a ninth aspect of the present disclosure can be realized by combining it with the eighth aspect. Preferably, the lighting fixture (A1) according to the ninth aspect further includes a lighting device (4) and a fixture body (1) that houses a light source.

[0102] The lighting fixture (A1) according to the ninth aspect can be made compact by accommodating the light source and the lighting device (4) in the fixture body (1). [Explanation of symbols]

[0103] A1 Lighting fixture 1. Device body 4 Lighting device 20 LEDs (light source) 41 First printed circuit board 42 Second Printed Circuit Board 410 AC / DC converter 411 First Control Section 412 Control power supply unit 413 Constant voltage section 420 DC conversion unit 421 Second Control Section 422 Peak hold section Vac AC voltage V1 First DC voltage V2 Second DC voltage L1 choke coil L2 Auxiliary winding Q1 switching element D1 Diode C1 smoothing capacitor R1, R2, R3, R4, R5 resistors (voltage divider)

Claims

1. an AC / DC converter that converts an AC voltage supplied from an external power supply into a first DC voltage; a first control unit that controls the AC / DC converter; a control power supply unit that generates a control voltage for operating the first control unit; a DC converter that converts the first DC voltage into a second DC voltage that is supplied to a light source; a second control unit that controls the DC conversion unit; Equipped with The AC / DC converter unit is A choke coil, a switching element that turns on and off the current supplied from the external power supply to the choke coil; a diode that rectifies the voltage induced in the choke coil; a smoothing capacitor that smoothes the voltage rectified by the diode; and The control power supply unit an auxiliary winding magnetically coupled to the choke coil; a constant voltage unit that constants the voltage induced in the auxiliary winding; and the first control unit controls the switching element to make the voltage across the smoothing capacitor constant when the AC voltage is supplied; the second control unit controls the DC conversion unit to stop outputting the second DC voltage when detecting that the supply of the AC voltage has stopped based on the voltage induced in the auxiliary winding. Lighting device.

2. a voltage dividing unit that divides the voltage induced in the auxiliary winding, the second control unit detects that the supply of the AC voltage has stopped based on a voltage obtained by dividing the voltage by the voltage dividing unit. The lighting device according to claim 1.

3. a peak hold unit that holds a peak value of the voltage divided by the voltage divider, the second control unit detects that the supply of the AC voltage has stopped by comparing the peak value held by the peak hold unit with a threshold value. The lighting device according to claim 2.

4. the voltage dividing unit has a plurality of resistors electrically connected in series, the peak hold unit holds a peak value of a voltage across both ends of a resistor having the lowest potential among the plurality of resistors, the resistance value of the resistor with the lowest potential is the smallest value among the resistance values ​​of the plurality of resistors; The lighting device according to claim 3.

5. a first printed circuit board forming the AC / DC converter, the first control unit, and the control power supply unit; a second printed circuit board forming the DC converter and the second controller; Further provided with one or more resistors including the resistor with the lowest potential among the plurality of resistors included in the voltage dividing unit are provided on the second printed circuit board; the remaining resistors of the plurality of resistors, excluding one or more resistors including the resistor with the lowest potential, are provided on the first printed circuit board; The lighting device according to claim 4.

6. The AC / DC converter has a step-up / step-down chopper circuit. A lighting device according to any one of claims 1 to 5.

7. The DC converter includes a step-down chopper circuit. The lighting device according to claim 6.

8. A lighting device according to any one of claims 1 to 5; a light source that is turned on by the lighting device; Equipped with Lighting fixtures.

9. Further provided is a fixture body that houses the lighting device and the light source.

9. The lighting fixture of claim 8.

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