JP2020057452A - Electric power unit and luminaire - Google Patents

Abstract

To provide an electric power unit capable of performing an appropriate protection operation for an excessive output voltage, while restraining malfunction of the protection operation, and a luminaire.SOLUTION: A lighting device 12 includes a conversion circuit 24, a detection circuit 27, and a microcomputer 25. The conversion circuit 24 converts an input power to supply it to a light source 13. The detection circuit 27 detects an output voltage from the conversion circuit 24. The microcomputer 25 has multiple voltage thresholds, and multiple operation times set according to the voltage thresholds. The microcomputer 25 performs a protection operation when the output voltage detected by the detection circuit 27 exceeds the voltage threshold continuously for the operation time or more. The larger the difference of the voltage threshold from a rated output voltage, the smaller the corresponding operation time.SELECTED DRAWING: Figure 1

Description

  An embodiment of the present invention relates to a power supply device having a conversion circuit for converting input power and supplying the converted power to a load, and a lighting device including the same.

  2. Description of the Related Art Conventionally, a power supply device used for a lighting device such as a downlight includes an AC / DC conversion circuit such as a power factor correction circuit (PFC) that converts an AC input voltage into a constant DC voltage, and a voltage from the AC / DC conversion circuit. And a DC / DC conversion circuit such as a step-down chopper circuit for outputting a DC constant voltage obtained by stepping down to a lighting load. In such a power supply device, when an output voltage from the DC / DC conversion circuit increases due to a failure such as opening or short-circuiting of a lighting load, the output voltage is compared with a predetermined voltage threshold, and the output voltage is compared. When the voltage continuously exceeds a predetermined voltage threshold for a predetermined time or more, there is a protection operation that stops output from the DC / DC conversion circuit.

  When the voltage threshold for performing the protection operation is set to a level slightly exceeding the rated output voltage, for example, if the output voltage overshoots for a short time due to a change in the input voltage or the like, the protection operation may be erroneously performed. is there. On the other hand, if the predetermined time until the start of the protection operation is set longer, depending on the circuit operation and the circuit system, it is not possible to safely protect when an excessive voltage occurs.

Japanese Patent No. 4901104

  The problem to be solved by the present invention is to provide a power supply device capable of appropriately performing a protection operation against an excessive output voltage while suppressing a malfunction of a protection operation, and a lighting device including the same.

  A power supply device according to an embodiment includes a conversion circuit, a detection circuit, and a control unit. The conversion circuit converts the input power and supplies it to the load. The detection circuit detects an output voltage of the conversion circuit. The control unit includes a plurality of voltage thresholds and a plurality of operation times set according to the voltage thresholds. The control unit performs the protection operation when the output voltage detected by the detection circuit continuously exceeds the voltage threshold for more than the operation time. Further, the operation time is shorter as the difference from the rated output voltage corresponds to the larger voltage threshold.

  ADVANTAGE OF THE INVENTION According to this invention, it can be expected that a protection operation | movement is appropriately performed with respect to an excessive output voltage, suppressing the malfunction of a protection operation | movement.

1 is a circuit diagram of a lighting device including a power supply device according to a first embodiment. 3 is a graph showing an output current of a conversion circuit of the power supply device. 4 is a graph illustrating an example of timing of a time change of an output voltage of a conversion circuit of the power supply device and a protection operation by a control unit. It is a circuit diagram of a part of the lighting installation provided with the power supply device which shows a 2nd embodiment.

  Hereinafter, a first embodiment will be described with reference to the drawings.

  In FIG. 1, reference numeral 10 denotes a lighting device. As the lighting device 10, for example, a downlight or the like is used. The lighting device 10 includes a lighting device 12 as a power supply device, a light source module 14 including a light source 13 such as an LED as a lighting load, and a dimmer 15 for setting a dimming degree of the light source 13.

  The lighting device 12 has a pair of input terminals of a rectifier circuit 21 connected to a commercial AC power supply e, which is an external power supply that supplies AC input power of, for example, 100 V, via a filter circuit (not shown). The rectifier circuit 21 rectifies the commercial AC power supply e into a DC power supply and outputs it. The first conversion circuit 22 is connected to a pair of output terminals of the rectification circuit 21. The first conversion circuit 22 is a known power factor improvement circuit for improving the power factor, and is a boost chopper circuit in the present embodiment. The first conversion circuit 22 converts the input voltage to a predetermined first voltage, for example, a first DC constant voltage higher than 160 V, and outputs the same.

The second conversion circuit 23 is connected to the output side of the first conversion circuit 22. In the present embodiment, the second conversion circuit 23 converts the first DC constant voltage input from the first conversion circuit 22 to a predetermined second voltage lower than the first voltage, for example, a second DC constant voltage higher than 42V. This is a step-down chopper circuit for converting and outputting. The first conversion circuit 22 and the second conversion circuit 23 constitute a conversion circuit 24 that converts the input power and supplies the converted power to the light source 13. The second conversion circuit 23 has one end connected to a series circuit of the switching element Q1 and the feedback diode D connected between the output terminals of the first conversion circuit 22 and a connection point between the switching element Q1 and the cathode of the feedback diode D. And an inductor L. The switching element Q1 is made of a semiconductor other than a silicon semiconductor such as gallium nitride (GaN), silicon carbide (SiC), and gallium oxide (Ga ₂ O ₃ ). Therefore, the switching element Q1 has less loss during the switching transition period than the switching element made of a silicon semiconductor. The control terminal of the switching element Q1 is connected to a microcomputer 25 as a control unit via a driver circuit DRV, and the switching element Q1 is switched by a PWM signal S1 output from the microcomputer 25. The switching element Q1 is switched at a predetermined operating frequency by the PWM signal S1, for example, at an operating frequency of 100 kHz or more. (FIG. 2). As described above, the second conversion circuit 23 can reduce the ripple of the current IL, which is the output current, by performing switching driving of the switching element Q1 at the operating frequency of 100 kHz or more.

  The feedback diode D is made of a semiconductor other than a silicon semiconductor, such as silicon carbide (SiC). Therefore, the temperature change of the feedback diode D during the reverse recovery time is smaller than that of the silicon semiconductor. The output terminal of the second conversion circuit 23 is connected to a switch circuit 26 including a switching element Q2 connected in parallel with the output terminal, and is connected to the input terminal of the light source module 14. The microcomputer 25 is connected to a control terminal of the switching element Q2, and the switching element Q2 is switched by a PWM signal S2 output from the microcomputer 25 according to the dimming degree set by the dimmer 15. Switching element Q2 is switched at an operating frequency lower than switching element Q1. Further, the switch circuit 26 generates a PWM signal for controlling the light source 13 by short-circuiting and opening the output terminals of the second conversion circuit 23 by switching of the switching element Q2. That is, the load current I, which is the average current flowing through the light source 13 of the light source module 14, is controlled by the switching of the switching element Q2 to the current IL, which is the output current of the conversion circuit 24 (second conversion circuit 23). Further, a resistor R for detecting the current IL is connected to the second conversion circuit 23 between the anode of the feedback diode D and the switching element Q2 which is one output terminal. The output terminal of the second conversion circuit 23 is connected to a detection circuit 27 that detects the output voltage of the second conversion circuit 23, that is, the output voltage of the conversion circuit 24.

  Further, an inverting input terminal of a comparator 28 is connected between the resistor R of the second conversion circuit 23 and the light source 13, and a predetermined reference voltage from a reference voltage source 29 is supplied to a non-inverting input terminal of the comparator 28. Has been entered. For this reason, the comparator 28 compares the magnitude of the current IL with the predetermined threshold current Ith based on the corresponding voltage. The output terminal of the comparator 28 is connected to the microcomputer 25, and the result of comparison by the comparator 28 is input to the microcomputer 25.

  The microcomputer 25 monitors the peak value of the current IL using, for example, the comparator 28, and sets the duty ratio of the PWM signal S1 according to the monitoring result, that is, based on the signal (voltage signal) input from the comparator 28. Perform feedback control.

  Further, the microcomputer 25 performs a protection operation when a load abnormality occurs, for example, when the light source module 14 is disconnected from the lighting device 12, that is, when the light source 13 is opened or a short circuit is caused by a failure of the light source 13. . In the present embodiment, a plurality of voltage thresholds and a plurality of operation times according to the voltage thresholds are set in the microcomputer 25. Then, when the output voltage detected by the detection circuit 27 becomes large due to a load abnormality, and the output voltage continuously exceeds the voltage threshold for the operation time corresponding to the output voltage, the microcomputer 25 converts the conversion circuit 24 ( A protection operation for reducing or stopping the output of the second conversion circuit 23) is performed.

  In this embodiment, two voltage thresholds and two operation times are set. That is, in the present embodiment, as shown in FIG. 3, the first voltage threshold Vth1 and the second voltage threshold Vth2, which are voltage thresholds set to different values, and the operation time corresponding to each of the voltage thresholds. A first operation time T1 and a second operation time T2 are set. In the present embodiment, the first and second voltage thresholds Vth1 and Vth2 are each in a steady state, that is, a value larger than the rated output voltage V. Further, the second voltage threshold Vth2 is set to be larger than the first voltage threshold Vth1. That is, the second voltage threshold Vth2 is a threshold that is larger than the first voltage threshold Vth1 in a steady state, that is, a difference from the rated output voltage V. These first and second voltage thresholds Vth1 and Vth2 may be fixed values set in advance, or the second voltage threshold Vth2 may be variably set. In this case, the second operation time T2 corresponding to the second voltage threshold Vth2 may be variably set according to the magnitude of the second voltage threshold Vth2. For example, the second operation time T2 may be set to be smaller as the difference between the rated output voltage V and the second voltage threshold Vth2 is larger. When the second operation time T2 is variably set, the second operation time T2 may be obtained by, for example, a mathematical expression or the like stored in advance in a memory (not shown) or may be set based on a table stored in the memory or the like. Further, each of the operation times T1 and T2 may be set to be smaller as the change amount of the output voltage detected by the detection circuit 27 is larger. For example, when the output voltage continuously rises from the rated output voltage V so as to exceed the first voltage threshold Vth1 and reach the second voltage threshold Vth2, the second voltage starts from the timing TM1 at which the first voltage threshold Vth1 is reached. By setting the second operation time T2 so as to be less than the time difference ΔT from the first operation time T1 to the time difference ΔT up to the timing TM2 when the threshold value Vth2 is reached, protection against a sharp rise in output voltage The operation can be reliably performed. For example, for a rated output voltage V of 120 V, the first voltage threshold Vth1 is set to 140 V, the second voltage threshold Vth2 is set to 200 V, the first operation time T1 is set to 100 msec, and the second operation time T2 is set to 40 msec. You.

  Next, the operation of the embodiment will be described.

  When power is supplied from the commercial AC power supply e to the lighting device 12, in the conversion circuit 24, the first conversion circuit 22 operates to boost the AC input voltage to the first DC constant voltage, and the second conversion circuit 23 It operates to drop the first DC constant voltage to the second DC constant voltage. At this time, in the second conversion circuit 23, the PWM signal S1 is output from the microcomputer 25 to the control terminal of the switching element Q1, and the switching element Q1 is switched according to the PWM signal S1.

  In the second conversion circuit 23, when the switching element Q1 is in the ON state, a current IL1 is output from the second conversion circuit 23 via the inductor L from the switching element Q1, and energy is stored in the inductor L. In the off state of the switching element Q1, the energy stored in the inductor L by the current IL1 is released, and the feedback diode D outputs the current IL2 from the second conversion circuit 23 via the inductor L. In this embodiment, the switching element Q1 is switching-driven at an operating frequency of 100 kHz or more, and a current IL (IL = IL1 + IL2) continuously flows through the inductor L as shown in FIG. The microcomputer 25 sets the duty ratio of the PWM signal S1 so that the current IL becomes a constant current while monitoring the peak value of the current IL via the comparator.

  Then, in the switch circuit 26, the PWM signal S2 is output from the microcomputer 25 to the control terminal of the switching element Q2, and the switching element Q2 is switched according to the PWM signal S2, so that the output terminals of the second conversion circuit 23 are short-circuited. By being opened, the load current I flows to the light source 13 according to the dimming degree set by the dimmer 15, and the light source 13 is turned on at the set dimming degree.

  Further, the microcomputer 25 performs a protection operation when the voltage detected by the detection circuit 27 continuously exceeds the voltage threshold. In the present embodiment, in this protection operation, a plurality of voltage thresholds are set, and the operation time set accordingly is reduced as the operation time corresponding to the voltage threshold having a larger difference from the rated output voltage. In the present embodiment, the first and second voltage thresholds Vth1 and Vth2 are set, and the first and second operation times T1 and T2 set in accordance with the first and second thresholds Vth1 and Vth2 have a large difference from the rated output voltage. The operation time T2 is set shorter than the first operation time T1. Therefore, if the output voltage becomes excessively large while slightly preventing the protection operation from being performed accidentally during normal operation, such as when the output voltage overshoots for a short time to slightly exceed the rated output voltage, The protection operation can be activated in a short time, and the protection operation can be performed appropriately.

  In particular, in this embodiment, the switching element Q2 of the switch circuit 26 is connected between the output terminals of the second conversion circuit 23, which is a step-down chopper circuit. Is formed, and a steep rise of the output voltage may occur when the load is abnormal. Therefore, as in the present embodiment, a plurality of voltage thresholds are set, and the operating time set in accordance therewith is reduced as the voltage corresponding to the voltage threshold having a larger difference from the rated output voltage is reduced. Even in the case of the circuit configuration of the lighting device 12 in which the booster circuit is formed on the output side in the event of an abnormality, an appropriate protection operation can be performed.

  When the voltage threshold value and the operation time are respectively set to fixed values set in advance, the microcomputer 25 has a simpler configuration, and the calculation load such as the voltage threshold value and the operation time can be reduced.

  A voltage threshold (second voltage threshold Vth2 in this embodiment) is variably set except for a voltage threshold (first voltage threshold Vth1 in this embodiment) having the smallest difference from the rated output voltage, and this voltage threshold (in this embodiment) When the second operation time T2) is variably set according to the voltage threshold (the second voltage threshold Vth2 in this embodiment), the microcomputer 25 can accurately perform the protection operation according to the change in the output voltage. .

  When the operation time is set to be smaller as the change amount of the output voltage detected by the detection circuit 27 is larger, the protection operation can be performed earlier as the output voltage changes more steeply. 10 can be reliably protected.

  In the first embodiment, the second conversion circuit 23 is a high-side step-down type circuit. However, as in the second embodiment partially shown in FIG. Type circuit. In this case, although the second voltage threshold Vth2 is set to be smaller than the first voltage threshold Vth1, the difference from the rated output voltage is larger for the second voltage threshold Vth2 than for the first voltage threshold Vth1, Similar to the embodiment, by setting the second operation time T2 shorter than the first operation time T1, the same operation and effect can be obtained.

  Further, in each of the above embodiments, the conversion circuit 24 has a configuration including the first conversion circuit 22 that is a step-up chopper circuit and the second conversion circuit 23 that is a step-down chopper circuit, but is not limited thereto. , Or a configuration including other step-up or step-down circuits.

  Although several embodiments of the present invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

10 Lighting equipment
12 Lighting device that is a power supply
13 Load is a light source
24 Conversion circuit
25 Microcontroller as control unit
27 Detection circuit
First operation time, which is T1 operation time
T2 Second operation time, which is the operation time V Rated output voltage
Vth1 First threshold which is voltage threshold
Vth2 Second threshold which is voltage threshold

Claims (5)

A conversion circuit for converting input power and supplying the converted power to a load;
A detection circuit for detecting an output voltage of the conversion circuit;
Comprising a plurality of voltage thresholds and a plurality of operation times set in accordance with the voltage thresholds, and protecting when an output voltage detected by the detection circuit continuously exceeds the voltage thresholds for the operation time or more. A control unit that performs an operation, and the operation time is smaller as the operation time corresponds to the voltage threshold having a larger difference from a rated output voltage;
A power supply device comprising: The power supply device according to claim 1, wherein the voltage threshold and the operation time are fixed values set in advance. The voltage threshold except for the voltage threshold having the smallest difference from the rated output voltage is variably set,
The power supply device according to claim 1, wherein the operation time according to the voltage threshold is variably set according to the voltage threshold. The power supply device according to claim 1, wherein the operation time is set to be smaller as a change amount of the output voltage detected by the detection circuit is larger. A light source that is the load;
A power supply device according to any one of claims 1 to 4;
A lighting device comprising:

Images