JP2015185360A - Lighting circuit, lighting device and lighting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting circuit, a lighting device and a lighting system having stable operation. According to an embodiment, a lighting circuit including a power conversion unit, a current cutoff circuit, and a control unit is provided. The power conversion unit is connected to the dimmer via the power supply path, is connected to the lighting load, converts the phase-controlled AC voltage supplied from the dimmer into a DC voltage, and supplies the lighting load. do. The current cutoff circuit has a cutoff state in which the current flowing in the power supply path is cut off and an allowable state in which the current is allowed to flow in the power supply path. The control unit detects an abnormality in the AC voltage, puts the current cutoff circuit in an allowable state when the abnormality is not detected, and puts the current cutoff circuit in a cutoff state when the abnormality is detected. [Selection diagram] Fig. 1

Description

  Embodiments described herein relate generally to a lighting circuit, a lighting device, and a lighting system.

  There is a lighting circuit that is connected to a phase control type dimmer, turns on the illumination load by converting AC power supplied from the dimmer to DC power and supplying it to the illumination load. There is a lighting device including a lighting circuit and a lighting load. There is an illumination system that includes an illumination device and a dimmer. In such a lighting circuit, lighting device, and lighting system, stable operation is desired.

JP 2009-232625 A JP 2012-034569 A

  It is an object of the present invention to provide a lighting circuit, a lighting device, and a lighting system with stable operation.

  According to the embodiment of the present invention, a lighting circuit including a power conversion unit, a current interruption circuit, and a control unit is provided. The power conversion unit is connected to the dimmer via a power supply path and is connected to an illumination load, and converts the phase-controlled AC voltage supplied from the dimmer into a DC voltage to convert the illumination Supply to the load. The current cut-off circuit has a cut-off state in which a current flowing through the power supply path is cut off, and an allowable state in which a current flows through the power supply path. The control unit detects an abnormality of the AC voltage, and when the abnormality is not detected, sets the current interrupt circuit to the allowable state, and when the abnormality is detected, interrupts the current interrupt circuit. Put it in a state.

  According to the embodiments of the present invention, it is possible to provide a lighting circuit, a lighting device, and a lighting system that operate stably.

It is a block diagram which represents typically the illuminating device which concerns on embodiment. It is a graph which represents typically an example of operation | movement of the lighting circuit which concerns on embodiment. It is a circuit diagram showing the lighting circuit concerning an embodiment typically.

Each embodiment will be described below with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between the parts, and the like are not necessarily the same as actual ones. Further, even when the same part is represented, the dimensions and ratios may be represented differently depending on the drawings.
Note that, in the present specification and each drawing, the same elements as those described above with reference to the previous drawings are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

FIG. 1 is a block diagram schematically illustrating a lighting device according to the embodiment.
As illustrated in FIG. 1, the lighting system LS includes a lighting device 10 and a dimmer 3. The lighting device 10 includes a lighting load 12 and a lighting circuit 14. The illumination load 12 includes an illumination light source 16 such as a light-emitting diode (LED). The illumination light source 16 may be, for example, an organic light-emitting diode (OLED). For the illumination light source 16, for example, a light emitting element having a forward voltage drop is used. The illumination load 12 lights the illumination light source 16 by applying an output voltage from the lighting circuit 14 and supplying an output current. The values of the output voltage and the output current are defined according to the illumination light source 16.

  The lighting circuit 14 is connected to the AC power source 2 and the dimmer 3. In the present specification, “connection” means electrical connection, and includes cases where the connection is not physically connected or connection is made via other elements. In addition, the case of magnetic coupling through a transformer or the like is also included in “connection”.

  The AC power source 2 is, for example, a commercial power source. The dimmer 3 is connected to the AC power source 2. The dimmer 3 generates an AC voltage VCT whose conduction angle is controlled from the AC power supply voltage VIN of the AC power supply 2. The dimmer 3 is connected in series between one terminals 4 and 6 of a pair of power supply lines that supply the power supply voltage VIN. That is, the dimmer 3 is a so-called two-wire dimmer. The dimmer 3 is not limited to this, and may be, for example, a 3-wire type or a 4-wire type.

  The lighting circuit 14 has a pair of input terminals 4 and 5 and a pair of output terminals 7 and 8. The lighting circuit 14 is connected to the AC power supply 2 and the dimmer 3 through the input terminals 4 and 5, and is connected to the lighting load 12 through the output terminals 7 and 8.

  The lighting circuit 14 turns on the illumination light source 16 by converting the AC voltage VCT supplied from the dimmer 3 into a DC voltage and outputting it to the illumination load 12. Further, the lighting circuit 14 performs dimming of the illumination light source 16 in synchronization with the AC voltage VCT whose conduction angle is controlled. The dimmer 3 is provided as necessary and can be omitted. When the dimmer 3 is not provided, the power supply voltage VIN of the AC power supply 2 is supplied to the lighting circuit 14.

  As the dimmer 3, a phase adjusting (leading edge) type dimmer is used. The dimmer 3 controls the phase of conduction in a period in which the absolute value of the AC voltage is the maximum value from the zero cross of the AC voltage. That is, in this example, the AC voltage VCT is a phase-controlled AC voltage. The dimmer 3 supplies the phase-controlled AC voltage VCT to the lighting circuit 14.

  The dimmer 3 may be a dimmer corresponding to a light emitting element such as an LED. The dimmer 3 includes a switching element 3s. The dimmer 3 switches between the conduction period and the interruption period of the phase control by turning on and off the switching element 3s. For example, when the switching element 3s is turned on, the AC voltage VCT is in a conduction interval, and when the switching element 3s is turned off, the AC voltage VCT is in a cutoff interval. For example, a triac or a power MOSFET is used as the switching element 3s.

  The dimmer 3 further includes, for example, a zero cross detection unit, a dimming degree setting unit, and a dimming control unit. The zero cross detector detects a zero cross of the power supply voltage VIN. The zero cross detection unit is connected to the dimming control unit, and inputs the detection result of the zero cross to the dimming control unit. The dimming degree setting unit is, for example, a slide switch or a dial switch. The dimming degree setting unit is connected to the dimming control unit. The dimming degree setting corresponding to the operation of the user or the like is input to the dimming control unit.

  For example, the dimming control unit turns on the switching element 3s after a predetermined time has elapsed since the detection of the zero cross. Then, the dimming control unit changes the timing for switching on the switching element 3s according to the set dimming degree. For example, the dimming control unit delays the timing of switching on the switching element 3s as the dimming degree is lower (closer to 0%). The dimming control unit turns off the switching element 3s when the zero cross is detected again. Thereby, the dimmer 3 converts the power supply voltage VIN into a phase-controlled AC voltage VCT.

  In addition, the dimming control unit continues to input a control signal for turning on the switching element 3s to the control terminal of the switching element 3s in the conduction period in which the switching element 3s is turned on. Thereby, for example, when the voltage on the load side is high, the switching element 3s can be prevented from being repeatedly turned on and off.

  The lighting circuit 14 includes a power conversion unit 20, a first power supply path 21a, a control unit 22, a control power supply unit 23, a current adjustment unit 24, a feedback circuit 25, and a current cutoff circuit 26. . The first power supply path 21 a is connected to the pair of input terminals 4 and 5.

  The power conversion unit 20 includes an AC-DC converter 20a, a DC-DC converter 20b, and a second power supply path 21b. The AC-DC converter 20a is connected to the first power supply path 21a. The AC-DC converter 20 a is connected to the dimmer 3 via the first power supply path 21 a and the input terminals 4 and 5. The AC-DC converter 20a converts the AC voltage VCT supplied via the first power supply path 21a into the first DC voltage VDC1.

  The DC-DC converter 20b is connected to the AC-DC converter 20a via the second power supply path 21b. The DC-DC converter 20b converts the first DC voltage VDC1 supplied from the second power supply path 21b into a second DC voltage VDC2 having a predetermined voltage value corresponding to the lighting load 12, and supplies the second DC voltage VDC2 to the lighting load 12. The absolute value of the second DC voltage VDC2 is different from the absolute value of the first DC voltage VDC1. The absolute value of the second DC voltage VDC2 is lower than the absolute value of the first DC voltage VDC1, for example. In this example, the DC-DC converter 20b is a step-down converter. By supplying the second DC voltage VDC2, the illumination light source 16 of the illumination load 12 is turned on. As described above, the power conversion unit 20 is connected to the dimmer 3 and the illumination load 12, converts the phase-controlled AC power supplied from the dimmer 3 into DC power, and supplies the DC power to the illumination load 12.

  The control power supply unit 23 includes a wiring unit 27 connected to the first power supply path 21a. The wiring unit 27 includes a wiring 27 a connected to the input terminal 4 and a wiring 27 b connected to the input terminal 5. The control power supply unit 23 converts the AC voltage VCT input via the wiring unit 27 into a DC drive voltage VDD corresponding to the control unit 22, and supplies the drive voltage VDD to the control unit 22. For example, the wiring unit 27 may be connected to the second power supply path 21b.

  The current adjustment unit 24 has a branch path 28 connected to the first power supply path 21a, and a conductive state in which a part of the current flowing through the first power supply path 21a flows to the branch path 28 and a non-conductive state in which no current flows. And can be switched. Thereby, the current adjustment part 24 adjusts the electric current which flows into the 1st power supply path | route 21a, for example. In this example, the branch path 28 of the current adjustment unit 24 is connected to the first power supply path 21 a via the control power supply unit 23. The branch path 28 may be directly connected to the first power supply path 21 a without going through the control power supply unit 23. The non-conductive state includes a case where a minute current that does not affect the operation flows through the branch path 28. The non-conduction state is a state in which, for example, the current flowing through the branch path 28 is smaller than the conduction state. For example, the branch path 28 may be connected to the second power supply path 21b.

  Control unit 22 detects the conduction angle of AC voltage VCT. The control unit 22 generates a dimming signal DMS corresponding to the detected conduction angle, and inputs the dimming signal DMS to the feedback circuit 25. Thereby, the control part 22 controls the conversion of the electric power by the power converter 20 according to the detected conduction angle. That is, the control unit 22 dims the illumination load 12 according to the detected conduction angle.

  In addition, the control unit 22 generates a control signal CGS according to the detected conduction angle, and inputs the control signal CGS to the current adjustment unit 24, so that the current adjustment unit 24 is turned on and off. Control the switching of In this way, the control unit 22 controls the current adjustment unit 24 and the feedback circuit 25 according to the detected conduction angle, thereby dimming the illumination light source 16 in synchronization with the conduction angle control of the dimmer 3. To do. For example, a microprocessor is used as the control unit 22.

  The feedback circuit 25 is connected to the output terminal 8 on the low potential side of the lighting circuit 14. That is, the feedback circuit 25 is connected to the end portion of the lighting load 12 on the low potential side. The feedback circuit 25 detects a current flowing through the illumination load 12 (illumination light source 16). The feedback circuit 25 feedback-controls the DC-DC converter 20b based on the dimming signal DMS input from the control unit 22 and the detected current.

  The feedback circuit 25 controls the current flowing through the lighting load 12 based on the dimming signal DMS and the detected current. The feedback circuit 25 controls the current flowing through the lighting load 12 to be substantially constant, for example. Thereby, for example, the luminance of the illumination load 12 can be kept practically constant. For example, it is possible to suppress an overcurrent from flowing through the lighting load 12.

  The current cut-off circuit 26 has a cut-off state in which a current flowing through the first power supply path 21a is cut off, and an allowable state in which a current flows through the first power supply path 21a. The cut-off state is a state in which substantially no current flows through the first power supply path 21a. That is, the cut-off state is a state in which substantially no current flows through the lighting circuit 14. The cutoff state may be, for example, a state in which a minute current that does not operate the power conversion unit 20, the control power supply unit 23, the current adjustment unit 24, and the like flows through the first power supply path 21a. In other words, the cut-off state is a state in which the current flowing through the first power supply path 21a is set to a predetermined value or less.

  The current interruption circuit 26 is connected to the control unit 22. The control unit 22 switches between the interruption state and the allowable state of the current interruption circuit 26. The control unit 22 detects an abnormality in the AC voltage VCT based on the detection voltage of the AC voltage VCT. When the controller 22 detects an abnormality in the AC voltage VCT, the controller 22 places the current interrupt circuit 26 in an interrupted state. And the control part 22 makes the electric current interruption circuit 26 a permission state, when the alternating voltage VCT is normal. In other words, the control unit 22 puts the current interrupt circuit 26 in an allowable state in a state where no abnormality of the AC voltage VCT is detected.

  Further, the current interrupt circuit 26 is allowed in the power-off state in which the lighting circuit 14 is not turned on. Thereby, when supplying the alternating voltage VCT to the lighting circuit 14 according to operation of a wall switch etc., it can suppress that an electric current is interrupted | blocked by the electric current interruption circuit 26 used as the interruption | blocking state.

  The control unit 22 includes a phase detection unit 22a, an abnormality detection unit 22b, and a signal generation unit 22c. The phase detector 22a detects the phase of the AC voltage VCT based on the detection voltage of the AC voltage VCT. In other words, the phase detector 22a detects the frequency of the AC voltage VCT. For example, the phase detection unit 22a detects whether the AC voltage VCT (power supply voltage VIN) is 50 Hz or 60 Hz. For example, when the frequency of the power supply voltage VIN is constant, the phase detector 22a may be omitted.

  The abnormality detection unit 22b detects an abnormality in the AC voltage VCT based on the detection voltage of the AC voltage VCT. In other words, the abnormality detection unit 22b detects a malfunction of the dimmer 3. For example, the abnormality detection unit 22b calculates the half-cycle time of the AC voltage VCT based on the detection result of the phase detection unit 22a. Then, the abnormality detection unit 22b determines that the AC voltage VCT is abnormal when the time during which the AC voltage VCT is equal to or less than the predetermined value is longer than the calculated half cycle time. That is, the abnormality detection unit 22b determines that the AC voltage VCT is abnormal when the AC voltage VCT is not output for more than a half cycle.

  For example, when the frequency of the AC voltage VCT is 60 Hz, the abnormality detection unit 22b determines that the AC voltage VCT is abnormal when the time during which the AC voltage VCT is equal to or less than a predetermined value becomes 8.3 ms or more. The method for detecting an abnormality in the AC voltage VCT is not limited to the above, and any method capable of detecting an abnormality in the AC voltage VCT (malfunction of the dimmer 3) may be used.

  The signal generator 22 c generates a control signal that is input to the current interrupt circuit 26. When the abnormality detection unit 22b has not detected an abnormality, the signal generation unit 22c generates a control signal for setting the current interruption circuit 26 to an allowable state and inputs the control signal to the current interruption circuit 26. As a result, in a state where no abnormality is detected, power is supplied to each unit such as the power conversion unit 20, the control power supply unit 23, and the current adjustment unit 24, and each unit operates normally.

  On the other hand, when the abnormality detection unit 22b detects an abnormality, the signal generation unit 22c generates a control signal for setting the current interruption circuit 26 to the interruption state and inputs the control signal to the current interruption circuit 26. Thereby, in the state where abnormality is detected, the power supply to each unit such as the power conversion unit 20, the control power supply unit 23, and the current adjustment unit 24 is cut off, and the operation of each unit is stopped.

FIG. 2 is a graph schematically showing an example of the operation of the lighting circuit according to the embodiment.
FIG. 2 schematically illustrates an example of the AC voltage VCT and the detection voltage Vdet input to the control unit 22. The horizontal axis in FIG. 2 is time, and the vertical axis in FIG. 2 is voltage. However, the scale of the voltage of the detection voltage Vdet is different from the scale of the voltage of the AC voltage VCT. The maximum value of the detection voltage Vdet is smaller than the maximum value of the AC voltage VCT. The detection voltage Vdet is illustrated as a pulsating voltage obtained by full-wave rectification of the AC voltage VCT.

  As shown in FIG. 2, in the dimmer 3 of the phase control method corresponding to the light emitting element, the dimming control unit malfunctions when the zero cross of the power supply voltage VIN is not correctly detected due to a sudden change in the power supply voltage VIN, The conduction angle may remain unstable. For example, as illustrated in FIG. 2, a state where the absolute value of the AC voltage VCT is increased may be maintained in the interruption period.

  As described above, when the absolute value of the AC voltage VCT in the cut-off section becomes high, for example, the lighting circuit 14 cannot properly detect the conduction angle. In the lighting circuit 14 that performs light control by detecting the conduction angle, the output is varied according to the variation of the conduction angle. For this reason, for example, it becomes a factor of occurrence of flicker (continuous change in luminance). For example, dimming is not performed appropriately.

  Further, the dimmer 3 of the two-wire phase control method secures the power of the dimmer 3 itself in the cutoff section. For this reason, if the state where the absolute value of the AC voltage VCT in the cut-off section is increased is maintained, the dimmer 3 cannot secure power. For this reason, when the dimmer 3 falls into the abnormal state as described above, the dimmer 3 tries to secure its own power by losing the output of the AC voltage VCT for about one cycle to one cycle.

  Therefore, the abnormality detection unit 22b determines that the AC voltage VCT is abnormal when the AC voltage VCT is not output for a half cycle or more as described above. Thereby, abnormality of AC voltage VCT can be detected appropriately.

  When the controller 22 detects an abnormality in the AC voltage VCT, the controller 22 places the current interrupt circuit 26 in an interrupted state. Thereby, a current substantially does not flow to the lighting device 10 side. In addition, since there is no path for current flow, no current flows through the dimmer 3. Therefore, when the current interruption circuit 26 is turned off, the dimmer 3 is turned off.

  Further, when the current interruption circuit 26 is turned off, the supply of the drive voltage VDD to the control unit 22 is also cut off, so that the operation of the control unit 22 is also stopped. At this time, the control power supply unit 23 is designed so that the timing for stopping the operation of the control unit 22 is later than the timing for stopping the operation of the dimmer 3. When the controller 22 stops operating, the current interrupt circuit 26 is switched from the interrupted state to the allowed state. As a result, a current flows again through the dimmer 3 and the lighting circuit 14, and the dimmer 3 and the lighting circuit 14 start to operate in the same manner as when the power is turned on.

  As described above, when the current interrupt circuit 26 is turned off, the dimmer 3 and the lighting circuit 14 once stop operation, and the dimmer 3 and the lighting circuit 14 operate again in response to the operation stop of the lighting circuit 14. Start. In other words, the dimmer 3 and the lighting circuit 14 are reset when the current cut-off circuit 26 is turned off. Thereby, the continuation of the abnormal state of AC voltage VCT can be eliminated. Therefore, the lighting circuit 14 according to the present embodiment can obtain a stable operation.

  For example, in a lighting circuit that does not have the current interruption circuit 26, when the abnormality of the AC voltage VCT as described above occurs, it is necessary to turn off the power of the dimmer 3 and the lighting device 10 by operating a wall switch or the like. There is.

  In contrast, in the lighting circuit 14, the dimmer 3 and the lighting circuit 14 are automatically reset. Thereby, in the lighting circuit 14, for example, it is possible to save the user from having to turn the power on and off. In addition, for example, it is possible to prevent the dimmer 3 from being used for a long time in a state where a malfunction occurs.

FIG. 3 is a circuit diagram schematically illustrating a lighting circuit according to the embodiment.
As illustrated in FIG. 3, the AC-DC converter 20 a includes a rectifier circuit 30, a smoothing capacitor 32, an inductor 34, and a filter capacitor 36.

  The rectifier circuit 30 is, for example, a diode bridge. Input terminals 30 a and 30 b of the rectifier circuit 30 are connected to a pair of input terminals 4 and 5. The AC voltage VCT subjected to phase control or reverse phase control is input to the input terminals 30 a and 30 b of the rectifier circuit 30 via the dimmer 3. For example, the rectifier circuit 30 performs full-wave rectification on the AC voltage VCT, and generates a pulsating voltage after full-wave rectification between the high-potential terminal 30c and the low-potential terminal 30d.

  The smoothing capacitor 32 is connected between the high potential terminal 30c and the low potential terminal 30d of the rectifier circuit 30. The smoothing capacitor 32 smoothes the pulsating voltage rectified by the rectifier circuit 30. As a result, the first DC voltage VDC1 appears at both ends of the smoothing capacitor 32.

  The inductor 34 is connected to the input terminal 4 in series. For example, the inductor 34 is connected in series to the first power supply path 21a. The filter capacitor 36 is connected between the input terminals 4 and 5. The filter capacitor 36 is connected in parallel to the first power supply path 21a, for example. The inductor 34 and the filter capacitor 36 remove noise included in the AC voltage VCT, for example.

  The DC-DC converter 20 b is connected to both ends of the smoothing capacitor 32. As a result, the first DC voltage VDC1 is input to the DC-DC converter 20b. The DC-DC converter 20b converts the first DC voltage VDC1 into a second DC voltage VDC2 having a different absolute value, and outputs the second DC voltage VDC2 to the output terminals 7 and 8 of the lighting circuit 14. The illumination load 12 is connected to the output terminals 7 and 8. The illumination load 12 lights the illumination light source 16 with the second DC voltage VDC2 supplied from the lighting circuit 14.

  The DC-DC converter 20b includes, for example, an output element 40, a current control element 41, a rectifier element 42, an inductor 43, a feedback winding (drive element) 44 that drives the output element 40, a coupling capacitor 45, and voltage dividing resistors 46 and 47. An output capacitor 48 and a bias resistor 49.

  The output element 40 and the current control element 41 are, for example, field effect transistors (FETs), for example, high electron mobility transistors (HEMTs), and are normally-on elements.

  The drain of the current control element 41 is electrically connected to the second power supply path 21b through the output element 40. The source of the current control element 41 is electrically connected to the lighting load 12. The gate of the current control element 41 is an electrode for controlling the current flowing between the drain and source of the current control element 41.

  The current control element 41 has a first state in which a current flows between the drain and the source, and a second state in which a current flowing between the drain and the source is smaller than the first state. The first state is, for example, an on state, and the second state is, for example, an off state. The first state is not limited to the on state. The second state is not limited to the off state. The first state may be an arbitrary state in which a relatively large current flows compared to the second state. The second state may be an arbitrary state in which the flowing current is relatively smaller than that of the first state.

  In the current control element 41 which is a normally-on type element, the first state is changed to the second state by reducing the gate potential below the source potential. For example, the current control element 41 changes from an on state to an off state by setting the gate potential to a negative potential relative to the source potential.

  The drain of the output element 40 is connected to the high potential terminal 30 c of the rectifier circuit 30. The source of the output element 40 is connected to the drain of the current control element 41. The gate of the output element 40 is connected to one end of the feedback winding 44 via the coupling capacitor 45.

  The source of the current control element 41 is connected to one end of the inductor 43 and the other end of the feedback winding 44. A voltage obtained by dividing the source potential of the current control element 41 by the voltage dividing resistors 46 and 47 is input to the gate of the current control element 41. A protection diode is connected to the gate of the output element 40 and the gate of the current control element 41.

  The bias resistor 49 is connected between the drain of the output element 40 and the source of the current control element 41, and supplies a DC voltage to the voltage dividing resistors 46 and 47. As a result, a potential lower than that of the source is supplied to the gate of the current control element 41.

  The inductor 43 and the feedback winding 44 are magnetically coupled in such a polarity that a positive voltage is supplied to the gate of the output element 40 when an increasing current flows from one end of the inductor 43 to the other end.

  The rectifying element 42 is connected between the source of the current control element 41 and the low potential terminal 30d of the rectifier circuit 30 with the direction of the current control element 41 from the low potential terminal 30d as the forward direction.

  In this example, a semiconductor element 50 is provided between the rectifying element 42 and the source of the current control element 41. For example, an FET or a GaN-HEMT is used for the semiconductor element 50. The semiconductor element 50 is, for example, a normally-on type. The gate of the semiconductor element 50 is connected to the low potential terminal 30 d of the rectifier circuit 30. Thereby, the semiconductor element 50 is held in an on state.

  The other end of the inductor 43 is connected to the output terminal 7. The low potential terminal 30 d of the rectifier circuit 30 is connected to the output terminal 8. The output capacitor 48 is connected between the output terminal 7 and the output terminal 8. The illumination load 12 is connected in parallel with the output capacitor 48 between the output terminal 7 and the output terminal 8.

  The control power supply unit 23 includes rectifying elements 61 to 63, a resistor 64, a charge storage element 65, a capacitor 66, a regulator 67, a Zener diode 68, and a semiconductor element 70.

  The rectifying elements 61 and 62 are, for example, diodes. The anode of the rectifying element 61 is connected to the high potential terminal 30c of the rectifying circuit 30 through the wiring 27a. The anode of the rectifying element 42 is connected to the low potential terminal 30d of the rectifying circuit 30 through the wiring 27b.

  For the semiconductor element 70, for example, an FET, a GaN-HEMT, or the like is used. Hereinafter, the semiconductor element 70 will be described as an FET. In this example, the semiconductor element 70 is an enhancement type n-channel FET. The semiconductor element 70 has a source, a drain, and a gate. The drain potential is set higher than the source potential. The gate is used to switch between a first state in which a current flows between the source and the drain and a second state in which a current flowing between the source and the drain is smaller than the first state. In the second state, substantially no current flows between the source and the drain. The semiconductor element 70 may be a p-channel type or a depletion type. For example, when the semiconductor element 70 is a p-channel type, the source potential is set higher than the drain potential.

  The drain of the semiconductor element 70 is connected to the cathode of the rectifying element 61 and the cathode of the rectifying element 62. That is, the drain of the semiconductor element 70 is connected to the first power supply path 21 a via the rectifying elements 61 and 62. The source of the semiconductor element 70 is connected to the anode of the rectifying element 63. The gate of the semiconductor element 70 is connected to the cathode of the Zener diode 68. The gate of the semiconductor element 70 is connected to the high potential terminal 30 c of the rectifier circuit 30 through the resistor 64.

  The cathode of the rectifying element 63 is connected to one end of the charge storage element 65 and the input terminal of the regulator 67. The output terminal of the regulator 67 is connected to one end of the control unit 22 and the capacitor 66.

  Currents of respective polarities accompanying application of the AC voltage VCT flow to the drain of the semiconductor element 70 through the rectifying element 61. As a result, a pulsating voltage obtained by full-wave rectification of the AC voltage VCT is applied to the drain of the semiconductor element 70.

  A pulsating voltage is applied to the cathode of the Zener diode 68 via the resistor 64 and the rectifying element 61. Thereby, a substantially constant voltage corresponding to the breakdown voltage of the Zener diode 68 is applied to the gate of the semiconductor element 70. Accordingly, a substantially constant current flows between the drain and source of the semiconductor element 70. The semiconductor element 70 functions as, for example, a constant current element. The semiconductor element 70 adjusts the current flowing through the wiring part 27.

  The charge storage element 65 is connected between the cathode of the rectifying element 63 and the low potential terminal 30 d of the rectifying circuit 30. In this example, the charge storage element 65 is a capacitor. The charge storage element 65 smoothes the pulsating voltage supplied from the source of the semiconductor element 70 via the rectifying element 63 and converts the pulsating voltage into a DC voltage.

  The regulator 67 is a so-called three-terminal regulator including an input terminal, an output terminal, and a common terminal. The input terminal of the regulator 67 is connected to the charge storage element 65. As a result, the DC voltage smoothed by the charge storage element 65 is input to the input terminal of the regulator 67. The output terminal of the regulator 67 is connected to the control unit 22. The common terminal of the regulator 67 is connected to the low potential terminal 30 d of the rectifier circuit 30. The regulator 67 generates a substantially constant DC drive voltage VDD from the input DC voltage, and outputs it to the control unit 22.

  As a result, the drive voltage VDD is supplied to the control unit 22, and the control unit 22 operates. The control power supply unit 23 continues to supply the drive voltage VDD to the control unit 22 for a predetermined time even after the current blocking circuit 26 is cut off by the charge accumulated in the charge storage element 65. In this way, the capacity of the charge storage element 65 is adjusted in the control power supply unit 23. For example, the capacity of the charge storage element 65 is made larger than the capacity of a capacitor or the like included in the dimmer 3. Thereby, the timing which stops operation | movement of the control part 22 can be made later than the timing which stops operation | movement of the light control device 3. FIG. The charge storage element 65 is not limited to a capacitor but may be a storage battery or the like. The charge storage element 65 may be provided separately from, for example, a smoothing capacitor.

  The capacitor 66 is connected to the output terminal of the regulator 67. The capacitor 66 is used for removing noise of the drive voltage VDD, for example. As a result, the drive voltage VDD is supplied to the control unit 22.

  Control power supply unit 23 further includes resistors 71 and 72. One end of the resistor 71 is connected to the cathodes of the rectifying elements 61 and 62. The other end of the resistor 71 is connected to one end of the resistor 72. The other end of the resistor 72 is connected to the low potential terminal 30 d of the rectifier circuit 30. A connection point between the resistors 71 and 72 is connected to the control unit 22. As a result, a voltage corresponding to the voltage dividing ratio of the resistors 71 and 72 is input to the control unit 22 as the detection voltage Vdet for detecting the absolute value of the AC voltage VCT.

  For example, the control unit 22 detects the conduction angle of the AC voltage VCT based on the detection voltage Vdet. The control unit 22 generates a dimming signal DMS based on the detection result, and inputs the dimming signal DMS to the feedback circuit 25. For example, the control unit 22 inputs a PWM signal corresponding to the detected conduction angle to the feedback circuit 25 as the dimming signal DMS.

  Further, as described above, the control unit 22 detects an abnormality in the AC voltage VCT based on the detection voltage Vdet. For example, the control unit 22 determines that the AC voltage VCT is abnormal when the time during which the AC voltage VCT is equal to or less than a predetermined value is longer than the half cycle time of the AC voltage VCT.

  The current adjustment unit 24 includes resistors 75 and 76 and a switching element 78. For the switching element 78, for example, an FET, a GaN-HEMT, or the like is used. Hereinafter, the switching element 78 will be described as an FET.

  One end of the resistor 75 is connected to the source of the semiconductor element 70. The other end of the resistor 75 is connected to the drain of the switching element 78. The gate of the switching element 78 is connected to the control unit 22 via the resistor 76. The control unit 22 inputs a control signal CGS to the gate of the switching element 78. For the switching element 78, for example, a normally-off type is used. For example, the switching element 78 changes from the off state to the on state by switching the control signal CGS input from the control unit 22 from Lo to Hi.

  When the switching element 78 is turned on, a part of the current flowing through the first power supply path 21a flows through the branch path 28 via the rectifying elements 61 and 62 and the semiconductor element 70, for example. That is, when the switching element 78 is turned on, the current adjustment unit 24 is turned on, and when the switching element 78 is turned off, the current adjustment unit 24 is turned off.

  The feedback circuit 25 includes a differential amplifier circuit 80 and a semiconductor element 100. In this example, the semiconductor element 100 is an npn transistor. The semiconductor element 100 is a normally-off type element. The semiconductor element 100 may be a pnp transistor, an FET, or the like. The semiconductor element 100 may be a normally-on type.

  The differential amplifier circuit 80 includes, for example, an operational amplifier 81, a resistor 82, and a capacitor 83. The resistor 82 is connected between the output terminal of the operational amplifier 81 and the inverting input terminal of the operational amplifier 81. The capacitor 83 is connected in parallel with the resistor 82. That is, the differential amplifier circuit 80 has negative feedback.

  The non-inverting input terminal of the operational amplifier 81 is connected to one end of the resistor 84. The other end of the resistor 84 is connected to one end of the resistor 85, one end of the resistor 86, and one end of the capacitor 87. The other end of the capacitor 87 is connected to the low potential terminal 30 d of the rectifier circuit 30. The other end of the resistor 85 is connected to the output terminal 7. The other end of the resistor 86 is connected to the output terminal 8 and one end of the resistor 88. The other end of the resistor 88 is connected to the low potential terminal 30 d of the rectifier circuit 30.

  As a result, a DC voltage obtained by dividing the second DC voltage VDC2 applied between the output terminals 7 and 8 by the resistors 85 and 86 is input to the non-inverting input terminal of the operational amplifier 81 as a detection voltage. That is, the non-inverting input terminal of the operational amplifier 81 is connected to the low potential side end of the illumination load 12. Thereby, the electric current which flows into the illumination light source 16 is detectable. When a light emitting element such as an LED is used for the illumination light source 16, the voltage of the illumination light source 16 is substantially constant according to the forward voltage drop. Therefore, when a light emitting element such as an LED is used for the illumination light source 16, the current flowing through the illumination light source 16 can be appropriately detected by connecting to the end of the illumination load 12 on the low potential side. .

  An inverting input terminal of the operational amplifier 81 is connected to one end of the resistor 90. The other end of the resistor 90 is connected to one end of the resistor 91 and one end of the capacitor 92. The other end of the capacitor 92 is connected to the low potential terminal 30 d of the rectifier circuit 30. The other end of the resistor 91 is connected to the control unit 22. Thus, the inverting input terminal of the operational amplifier 81 is connected to the control unit 22 via the resistors 90 and 91. As a result, the dimming signal DMS from the control unit 22 is input to the inverting input terminal of the operational amplifier 81.

  For example, a DC voltage obtained by smoothing the PWM signal with the capacitor 92 is input to the inverting input terminal of the operational amplifier 81 as the dimming signal DMS. For example, a DC voltage corresponding to the dimming degree of the dimmer 3 is input to the inverting input terminal of the operational amplifier 81 as the dimming signal DMS. The voltage level of the dimming signal DMS is set corresponding to the voltage level of the detection voltage input to the non-inverting input terminal. More specifically, for example, the voltage level of the dimming signal DMS corresponding to the desired dimming level is substantially the same as the voltage level of the detection voltage when the illumination light source 16 emits light with the luminance corresponding to the dimming level. Is set as follows.

  As described above, the detection voltage corresponding to the current flowing through the illumination light source 16 is input to the non-inverting input terminal of the operational amplifier 81, and the dimming signal DMS is input to the inverting input terminal of the operational amplifier 81. As a result, a signal corresponding to the difference between the detection voltage and the dimming signal DMS is output from the output terminal of the operational amplifier 81. As the detection voltage becomes higher than the dimming signal DMS, the output of the operational amplifier 81 also increases. That is, when an overcurrent flows through the illumination light source 16, the output of the operational amplifier 81 increases. Thus, in this example, the dimming signal DMS is used as a reference value. When dimming is not performed, a substantially constant DC voltage serving as a reference value may be input to the inverting input terminal of the operational amplifier 81.

  The collector of the semiconductor element 100 is connected to one end of the voltage dividing resistor 47. The collector of the semiconductor element 100 is electrically connected to the gate of the current control element 41 via the voltage dividing resistor 47. The emitter of the semiconductor element 100 is connected to one end of the resistor 101. The other end of the resistor 101 is connected to the low potential terminal 30 d of the rectifier circuit 30. As a result, the emitter of the semiconductor element 100 is set to a potential lower than the potential of the source of the current control element 41. The base of the semiconductor element 100 is connected to the output terminal of the operational amplifier 81. As a result, the current flowing between the emitter and collector of the semiconductor element 100 is controlled by the output from the operational amplifier 81.

  The semiconductor element 100 has a third state in which a current flows between the collector and the emitter, and a fourth state in which a current flowing between the collector and the emitter is smaller than the third state. The third state is, for example, an on state, and the fourth state is, for example, an off state. The third state is not limited to the on state. The fourth state is not limited to the off state. The third state may be an arbitrary state in which a relatively large current flows compared to the fourth state. The fourth state may be an arbitrary state in which the flowing current is relatively smaller than that in the third state.

  In this example, the semiconductor element 100 is normally-off type, and changes from the fourth state to the third state by setting the base potential higher than the emitter potential. For example, when the base potential is made higher than the emitter potential, the semiconductor element 100 changes from the off state to the on state.

  As described above, when the detection voltage is larger than the dimming signal DMS, the output of the operational amplifier 81 becomes large. Therefore, for example, the semiconductor element 100 is turned on when the detection voltage is larger than the dimming signal DMS, and is turned off when the detection voltage is less than or equal to the dimming signal DMS. For example, as the detection voltage becomes higher than the dimming signal DMS, the current between the emitter and collector of the semiconductor element 100 increases.

  The collector of the semiconductor element 100 is further connected to one end of the resistor 102 and one end of the capacitor 103. The other end of the resistor 102 is connected to the base of the semiconductor element 100. The other end of the capacitor 103 is connected to the low potential terminal 30 d of the rectifier circuit 30. The base of the semiconductor element 100 is further connected to one end of the resistor 104. The other end of the resistor 104 is connected to the low potential terminal 30 d of the rectifier circuit 30. Thus, the reference potential of the feedback circuit 25 is set to the potential of the low potential terminal 30d of the rectifier circuit 30. That is, the reference potential of the feedback circuit 25 is common with the reference potential of the DC-DC converter 20b. The reference potential of the feedback circuit 25 is substantially the same as the reference potential of the DC-DC converter 20b.

  The current interrupt circuit 26 includes a first switching element 111 and a second switching element 112. Each of the switching elements 111 and 112 has a pair of main terminals and a control terminal that controls a current flowing between the main terminals. For each switching element 111, 112, for example, a bipolar transistor or FET is used. Each of the switching elements 111 and 112 is not limited to these and may be any element capable of switching.

  One main terminal of the first switching element 111 is connected to the gate (control terminal) of the semiconductor element 70. The other main terminal of the first switching element 111 is connected to the low potential terminal 30 d of the rectifier circuit 30. A control terminal of the first switching element 111 is connected to the control unit 22.

  When the first switching element 111 is turned on, the potential of the gate of the semiconductor element 70 becomes the potential of the low potential terminal 30d. The potential of the gate of the semiconductor element 70 becomes lower than the potential of the source of the semiconductor element 70. Accordingly, when the first switching element 111 is turned on, the semiconductor element 70 is turned off. Thus, when the first switching element 111 is turned on, no current flows through the control power supply unit 23 and the current adjustment unit 24.

  As described above, the first switching element 111 can block the current flowing through the control power supply unit 23 and the current adjustment unit 24. The configuration of the first switching element 111 is not limited to the above, and may be any configuration capable of interrupting the current flowing through the control power supply unit 23 and the current adjustment unit 24. For example, the first switching element 111 may be connected in series to the wiring unit 27 and the branch path 28. In this case, when the first switching element 111 is turned off, the current flowing through the control power supply unit 23 and the current adjusting unit 24 is interrupted.

  One main terminal of the second switching element 112 is connected to the low potential terminal 30 d of the rectifier circuit 30. The other main terminal of the second switching element 112 is connected to one end of the smoothing capacitor 32. That is, the second switching element 112 is connected between the rectifier circuit 30 and the smoothing capacitor 32. Therefore, when the second switching element 112 is turned off, no current flows through the power conversion unit 20. A control terminal of the second switching element 112 is connected to the control unit 22.

  As described above, the second switching element 112 can block the current flowing through the power conversion unit 20. The configuration of the second switching element 112 is not limited to the above, and may be any configuration capable of interrupting the current flowing through the power conversion unit 20.

  On / off of each of the switching elements 111 and 112 is controlled by the control unit 22. In this example, the current cutoff circuit 26 is cut off by turning on the first switching element 111 and turning off the second switching element 112. Then, when the first switching element 111 is turned off and the second switching element 112 is turned on, the current interrupt circuit 26 is allowed.

  For example, a normally-off type element is used for the first switching element 111, and a normally-on type element is used for the second switching element 112. Thereby, for example, in a state where power is not supplied to the lighting circuit 14, the current interrupt circuit 26 can be allowed.

  The configuration of the current cutoff circuit 26 is not limited to the above, and may be any configuration that can be switched between a cutoff state and an allowable state. For example, the second switching element 112 may be omitted. For example, when an abnormality in the AC voltage VCT is detected, the dimming signal DMS is set to 0%, and the operation of the DC-DC converter 20b is stopped. As a result, no current flows through the DC-DC converter 20b, and the potential of the smoothing capacitor 32 becomes substantially the same as the potential on the input side, so that no current flows through the AC-DC converter 20a. That is, no current flows through the power conversion unit 20 as in the case where the second switching element 112 is turned off. Thus, the second switching element 112 is provided as necessary and can be omitted.

  The current interrupt circuit 26 may be, for example, a switching element provided between the input terminals 4 and 5 and the rectifier circuit 30. In this case, when the switching element is turned off, the current interrupt circuit 26 is interrupted, and when the switching element is turned on, the current interrupt circuit 26 is allowed.

Next, the operation of the lighting circuit 14 will be described.
First, when the dimming degree of the dimmer 3 is set to approximately 100% and the input power supply voltage VIN is transmitted as it is, that is, when the highest first DC voltage VDC1 is input to the DC-DC converter 20b. Will be described.

  When the power supply voltage VIN is supplied to the lighting circuit 14, since the output element 40 and the current control element 41 are normally-on elements, both are turned on. Then, a current flows through the path of the output element 40, the current control element 41, the inductor 43, and the output capacitor 48, and the output capacitor 48 is charged. The voltage across the output capacitor 48, that is, the voltage between the output terminals 7 and 8, is supplied to the illumination light source 16 of the illumination load 12 as the second DC voltage VDC2. Note that since the output element 40 and the current control element 41 are on, a reverse voltage is applied to the rectifying element 42. No current flows through the rectifying element 42.

  When the second DC voltage VDC2 reaches a predetermined voltage, a current flows through the illumination light source 16, and the illumination light source 16 is turned on. At this time, a current flows through the path of the output element 40, the current control element 41, the inductor 43, the output capacitor 48 and the illumination light source 16. For example, when the illumination light source 16 is an LED, the predetermined voltage is a forward voltage drop of the LED and is determined according to the illumination light source 16. Further, when the illumination light source 16 is turned off, no current flows, so the output capacitor 48 holds the value of the output voltage.

  The first DC voltage VDC1 input to the DC-DC converter 20b is sufficiently higher than the second DC voltage VDC2. That is, the potential difference ΔV between the input and output is sufficiently large. For this reason, the current flowing through the inductor 43 increases. Since the feedback winding 44 is magnetically coupled to the inductor 43, an electromotive force having a polarity with a high potential on the coupling capacitor 45 side is induced in the feedback winding 44. Therefore, a positive potential is supplied to the gate of the output element 40 with respect to the source via the coupling capacitor 45, and the output element 40 is kept on.

  When the current flowing through the current control element 41 exceeds the upper limit value, the drain-source voltage of the current control element 41 increases rapidly. Therefore, the gate-source voltage of the output element 40 becomes lower than the threshold voltage, and the output element 40 is turned off. The upper limit value is the saturation current value of the current control element 41 and is defined by the potential input to the gate of the current control element 41. The gate potential of the current control element 41 includes the DC voltage supplied to the voltage dividing resistors 46 and 47 via the bias resistor 49, the voltage of the illumination light source 16, the voltage dividing ratio of the voltage dividing resistors 46 and 47, and the semiconductor element 100. Set by current between emitter and collector. As described above, since the gate potential of the current control element 41 is negative with respect to the source, the saturation current value can be limited to an appropriate value.

  The inductor 43 continues to pass current through the path of the rectifying element 42, the output capacitor 48, and the lighting load 12. At this time, since the inductor 43 releases energy, the current of the inductor 43 decreases. For this reason, an electromotive force having a polarity that causes the coupling capacitor 45 side to have a low potential is induced in the feedback winding 44. A negative potential is supplied to the gate of the output element 40 with respect to the source via the coupling capacitor 45, and the output element 40 maintains the OFF state.

  When the energy stored in the inductor 43 becomes zero, the current flowing through the inductor 43 becomes zero. The direction of the electromotive force induced in the feedback winding 44 is reversed again, and an electromotive force that induces a high potential on the coupling capacitor 45 side is induced. As a result, a potential higher than that of the source is supplied to the gate of the output element 40, and the output element 40 is turned on again. Thereby, it returns to the state which reached said predetermined voltage.

  Thereafter, the above operation is repeated. As a result, the output element 40 is automatically switched on and off, and the illumination light source 16 is supplied with the second DC voltage VDC2 having the power supply voltage VIN lowered. That is, in the lighting circuit 14, the switching frequency of the output element 40 is set by the voltage dividing resistors 46 and 47 and the feedback circuit 25. Further, the current supplied to the illumination light source 16 becomes a substantially constant current whose upper limit value is limited by the current control element 41. Therefore, the illumination light source 16 can be lighted stably.

  The differential amplifier circuit 80 of the feedback circuit 25 changes the base potential of the semiconductor element 100 according to the difference between the detection voltage corresponding to the current flowing through the illumination light source 16 and the dimming signal DMS. The differential amplifier circuit 80 has, for example, a high potential at the base of the semiconductor element 100 when an overcurrent flows through the illumination light source 16 and the voltage level of the detection voltage is higher than a predetermined value with respect to the voltage level of the dimming signal DMS. Is set to substantially turn on the semiconductor element 100.

  When the semiconductor element 100 is turned on, the gate potential of the current control element 41 is set at, for example, the low potential terminal 30d of the rectifier circuit 30. That is, a negative potential is set as the gate potential of the current control element 41, and the current control element 41 is turned off. Thereby, the electric current which flows into the illumination light source 16 becomes small, and it is suppressed that an overcurrent flows into the illumination light source 16. Thus, in this example, the feedback circuit 25 feedback-controls the DC-DC converter 20b based on the detected voltage and the dimming signal DMS.

  When the dimming degree of the dimmer 3 is set to a value smaller than 100% and the input AC voltage VCT is transmitted with the conduction angle controlled, that is, the high first DC voltage VDC1 is input to the DC-DC converter 20b. The same applies to the case where the output element 40 can continue to oscillate. The value of the first DC voltage VDC1 input to the DC-DC converter 20b changes according to the dimming degree of the dimmer 3, and the average value of the output current can be controlled. Therefore, the illumination light source 16 of the illumination load 12 can be dimmed according to the dimming degree.

  Further, when the dimming degree of the dimmer 3 is set to a smaller value, that is, when the first DC voltage VDC1 input to the DC-DC converter 20b is lower, the inductor even if the output element 40 is turned on. Since the potential difference between both ends of 43 is small, the current flowing through the inductor 43 cannot be increased. Therefore, the output element 40 is not turned off and outputs a constant direct current. That is, the lighting circuit 14 operates like a series regulator when the dimming degree of the dimmer 3 is small, that is, when the potential difference ΔV between the input and output is small.

  As described above, the lighting circuit 14 performs a switching operation when the potential difference ΔV is larger than a predetermined value, and operates as a series regulator when the potential difference ΔV is small. When the potential difference ΔV is large, the product of the potential difference ΔV and the current is large, and the loss increases when the series regulator is operated. Therefore, when the potential difference ΔV is large, the switching operation is suitable for low power consumption. When the potential difference ΔV is small, the loss is small, and there is no problem in operating as a series regulator.

  Further, in the lighting circuit 14, when the potential difference ΔV is smaller than a predetermined value, the output element 40 is not turned off, the current vibrates while continuing the on state, and the lighting load 12 is obtained with the average value of the current. The illumination light source 16 is turned on. When the potential difference ΔV is further smaller, the output element 40 outputs a direct current to the illumination load 12 to turn on the illumination light source 16 while continuing the on state. As a result, in the lighting circuit 14, the output current can be continuously changed to zero. For example, in the illumination device 10, the illumination light source 16 of the illumination load 12 can be turned off smoothly.

  In the lighting circuit 14, the output current is continuously increased from the maximum value during the switching operation of the output element 40 to the minimum value when the DC current is output while the output element 40 is kept on according to the potential difference ΔV. Can be changed. For example, in the illumination device 10, the illumination light source 16 can be dimmed continuously in the range of 0 to 100%.

  In the lighting circuit 14, a feedback circuit 25 is connected to the end of the lighting load 12 on the low potential side, a current flowing through the illumination light source 16 is detected, and the operation of the DC-DC converter 20b is feedback-controlled according to the detection result. ing. The voltage of the illumination light source 16 is stabilized to some extent even when an input voltage such as the power supply voltage VIN or the AC voltage VCT is distorted. Therefore, by detecting the current flowing through the illumination light source 16 by connecting the feedback circuit 25 to the low potential end of the illumination load 12 as described above, for example, the current detection accuracy can be improved. For example, when an overcurrent occurs, the current flowing through the illumination light source 16 can be stopped immediately. Furthermore, a negative potential can be easily set for the gate of the normally-on type current control element 41. Thereby, in the lighting circuit 14, more reliable current control and overcurrent protection can be performed.

  In the lighting circuit 14, the reference potential of the feedback circuit 25 is common with the reference potential of the DC-DC converter 20b. Thereby, for example, fluctuations in the second DC voltage VDC2 that is the output voltage can be suppressed.

  The phase detection unit 22a of the control unit 22 detects the phase of the AC voltage VCT based on the detection voltage Vdet of the AC voltage VCT. The abnormality detection unit 22b detects an abnormality in the AC voltage VCT based on the detection voltage of the AC voltage VCT. For example, based on the detection result of the phase detector 22a, the half-cycle time of the AC voltage VCT is calculated, and the AC voltage VCT is less than a predetermined value when the AC voltage VCT is longer than the calculated half-cycle time. VCT is determined to be abnormal.

  When the abnormality detection unit 22b detects an abnormality, the signal generation unit 22c generates a control signal for setting the current interruption circuit 26 to the interruption state, and inputs the control signal to the current interruption circuit 26. For example, a control signal for turning on the first switching element 111 is generated and input to the control terminal of the first switching element 111, and a control signal for turning off the second switching element 112 is generated to generate the second switching element. Input to the control terminal of the element 112. Thereby, the electric current interruption circuit 26 will be in the interruption | blocking state.

  When the current interruption circuit 26 is turned off, the operations of the dimmer 3 and the lighting circuit 14 are reset as described above, and the abnormal state of the AC voltage VCT is eliminated. Thereby, stable operation can be obtained in the dimmer 3 and the lighting circuit 14. For example, it is possible to save the user and the like from turning the power on and off. For example, the dimmer 3 can be prevented from being used for a long time in a state where it malfunctions.

  As described above, the embodiments have been described with reference to specific examples. However, the embodiments are not limited thereto, and various modifications are possible.

  For example, the output element 40 and the current control element 41 are not limited to the GaN-based HEMT. For example, a semiconductor element formed using a semiconductor (wide band gap semiconductor) having a wide band gap such as silicon carbide (SiC), gallium nitride (GaN), or diamond on the semiconductor substrate may be used. Here, the wide band gap semiconductor means a semiconductor having a wider band gap than gallium arsenide (GaAs) having a band gap of about 1.4 eV. For example, a semiconductor having a band gap of 1.5 eV or more, gallium phosphide (GaP, band gap about 2.3 eV), gallium nitride (GaN, band gap about 3.4 eV), diamond (C, band gap about 5.27 eV) , Aluminum nitride (AlN, band gap of about 5.9 eV), silicon carbide (SiC), and the like. Such a wide band gap semiconductor element can be made smaller than a silicon semiconductor element when the breakdown voltage is made equal, so that the parasitic capacitance is small and high speed operation is possible, so that the switching cycle can be shortened, and the winding parts and Capacitors can be miniaturized.

  In the above embodiment, the output element 40 and the current control element 41 are cascode-connected, switching is performed by the output element 40, and current is controlled by the current control element 41. For example, the switching and current control may be performed only by the current control element 41.

  The configuration of the power conversion unit 20 is not limited to the above, and may be any configuration that can change the phase-controlled AC power to DC power. In the above embodiment, the control unit 22 controls the power conversion by the power conversion unit 20 by inputting the dimming signal DMS to the feedback circuit 25. The control method of the power conversion unit 20 by the control unit 22 is not limited to the above, and any method according to the configuration of the power conversion unit 20 may be used. For example, when the power conversion unit 20 is a chopper circuit including a switching element, the power conversion in the power conversion unit 20 may be controlled by controlling the switching of the switching element.

  The illumination light source 16 is not limited to an LED, and may be, for example, an organic EL (Electro-Luminescence) or an OLED (Organic light-emitting diode). A plurality of illumination light sources 16 may be connected to the illumination load 12 in series or in parallel.

  Although several embodiments and examples of the present invention have been described, these embodiments or examples are presented as examples and are not intended to limit the scope of the invention. These novel embodiments or examples can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments or examples and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 2 ... AC power supply, 3 ... Dimmer, 3s ... Switching element, 10 ... Illuminating device, 12 ... Illumination load, 14 ... Lighting circuit, 16 ... Illumination light source, 20 ... Power conversion part, 20a ... AC-DC converter, 20b ... DC-DC converter, 21a ... first power supply path, 21b ... second power supply path, 22 ... control section, 22a ... phase detection section, 22b ... abnormality detection section, 22c ... signal generation section, 23 ... control power supply , 24 ... Current adjustment unit, 25 ... Feedback circuit, 26 ... Current cut-off circuit, 27 ... Wiring unit, 28 ... Branch path, 30 ... Rectifier circuit, 32 ... Smoothing capacitor, 34 ... Inductor, 36 ... Filter capacitor, 40 ... Output element 41 ... Current control element 42 ... Rectifier element 43 ... Inductor 44 ... Feedback winding 45 ... Coupling capacitor, 46, 47 ... voltage dividing resistor, 48 ... output capacitor, 49 ... bias resistor, 50 ... semiconductor element, 61-63 ... rectifier element, 64 ... resistor, 65 ... charge storage element, 66 ... capacitor, 67 ... regulator, 68 ... Zener diode 70 ... Semiconductor element 71, 72 ... Resistor 80 ... Differential amplifier circuit 81 ... Operational amplifier 82, 84-86, 88, 90, 91 ... Resistor 83, 87, 92 ... Capacitor 100 ... Semiconductor Element, 101, 102, 104 ... Resistance, 103 ... Capacitor, 111 ... First switching element, 112 ... Second switching element, LS ... Lighting system

Claims (7)

Power conversion connected to the dimmer through a power supply path and connected to the lighting load, and converting the phase-controlled AC voltage supplied from the dimmer into a DC voltage and supplying the DC voltage to the lighting load And
A current cut-off circuit having a cut-off state that cuts off a current flowing through the power supply path and an allowable state that allows a current to flow through the power supply path;
A control unit that detects an abnormality of the AC voltage, sets the current interrupt circuit to the allowable state when the abnormality is not detected, and sets the current interrupt circuit to the interrupt state when the abnormality is detected. When,
Lighting circuit equipped with. A power supply unit for control connected to the power supply path, converting the AC voltage into a drive voltage corresponding to the control unit, and supplying the drive voltage to the control unit;
The control power supply unit includes a charge storage element, and supplies the drive voltage to the control unit for a predetermined time by the charge stored in the charge storage element when the current interrupt circuit is in the shut-off state. The lighting circuit according to claim 1 which continues. A branch path connected to the power supply path, and switches between a conduction state in which a part of the current flowing through the power supply path flows to the branch path and a non-conduction state in which the current does not flow, and flows to the power supply path A current adjusting unit for adjusting the current;
The lighting circuit according to claim 1, wherein the current interruption circuit includes a first switching element capable of interrupting a current flowing through the current adjustment unit.   The lighting circuit according to claim 3, wherein the current interrupt circuit further includes a second switching element capable of interrupting a current flowing through the power converter. The illumination load has a light emitting element as an illumination light source,
The dimmer includes a switching element that switches between a conduction section and a cutoff section of the AC voltage, and a control signal that turns the switching element on in the conduction section that turns the switching element on. The lighting circuit according to any one of claims 1 to 4, wherein the lighting circuit continues to be input. Lighting load,
The lighting circuit according to any one of claims 1 to 5, wherein power is supplied to the lighting load.
A lighting device comprising: A lighting device according to claim 6;
A dimmer for supplying a phase-controlled AC voltage to the lighting device;
With
The illumination load has a light emitting element as an illumination light source,
The dimmer includes a switching element that switches between a conduction section and a cutoff section of the AC voltage, and a control signal that turns the switching element on in the conduction section that turns the switching element on. Continue to enter into the lighting system.

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