JP2017070002A - Dc/ac conversion circuit and power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such the problem that it is difficult to achieve higher efficiency in the conventional DC/AC conversion circuit.SOLUTION: A DC/AC conversion circuit according to the present invention includes: a second inverter which is connected between high potential side power supply wiring and low potential side power supply wiring in series; a first capacitor which is connected to a first inverter in parallel; a second capacitor which is connected to the second inverter in parallel; a first voltage detecting unit which detects a first voltage generated at both ends of the first capacitor; a second voltage detecting unit which detects a second voltage generated at both ends of the second capacitor; a correction value generating unit which generates a correction value corresponding to a voltage difference between the first voltage and the second voltage; a first PWM signal control unit which generates a PWM signal to be output to the first inverter by adding the correction value to a duty instruction value; and a second PWM signal control unit which generates a PWM signal to be output to the second inverter by subtracting the correction value from the duty instruction value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a DC / AC conversion circuit and a power supply device, and more particularly to a DC / AC conversion circuit and a power supply device that generate an AC voltage from a DC voltage by an inverter circuit.

  An example of a power supply device is disclosed in Patent Documents 1 and 2. The power supply device described in Patent Document 1 generates an AC voltage based on the step-down voltage using an inverter circuit after stepping down a DC voltage generated by a solar cell using a converter circuit.

  Moreover, the power supply device described in Patent Document 2 steps down DC voltages generated by a plurality of solar cells by a plurality of converters to other voltages, respectively. Then, after synthesizing a plurality of stepped-down DC voltages, an AC voltage is generated using an inverter circuit.

JP 2004-147472 A JP 2004-215439 A

  Power supply devices are required to have high efficiency. As one means for improving the efficiency, it is conceivable to increase the DC voltage input to the inverter circuit. However, when the DC voltage input to the inverter circuit is increased, high voltage elements must be used for the switching elements and capacitors used in the inverter circuit. However, there is a problem that a high breakdown voltage switching element has a large power loss and causes a reduction in efficiency. Furthermore, the high withstand voltage circuit element has a problem that the volume is large and the volume of the apparatus is increased.

  One aspect of the DC / AC converter circuit according to the present invention includes a high potential side power supply line to which a high potential side DC voltage is input, a low potential side power supply line to which a low potential side DC voltage is input, and the high potential side power supply. A first inverter connected between the wiring and the series node, a second inverter connected between the series node and the low-potential side power supply wiring, and the first inverter are connected in parallel. A first capacitor; a second capacitor connected in parallel with the second inverter; a first voltage detector for detecting a first voltage generated across the first capacitor; and the second capacitor A second voltage detector for detecting a second voltage generated across the capacitor, and a correction value for generating a correction value according to the magnitude of the voltage difference between the first voltage and the second voltage A generating unit; the first inverter; and the second inverter. A first PWM signal control unit that outputs to the first inverter a PWM signal having a duty ratio corresponding to a duty value obtained by adding the correction value to a duty instruction value that sets a duty ratio of a PWM signal that controls the inverter; And a second PWM signal control unit that outputs a PWM signal having a duty ratio corresponding to a duty value obtained by subtracting the correction value from the duty instruction value to the second inverter.

  One aspect of a power supply device according to the present invention includes at least the above-described DC-AC conversion circuit, converts an AC signal supplied from the outside into a DC signal, and supplies the DC signal to the DC-AC conversion circuit, and the DC-AC conversion The circuit includes a converter circuit that converts the AC voltage output by the first inverter and the second inverter into a DC voltage, and configures the converted DC voltage to drive a load.

  ADVANTAGE OF THE INVENTION According to this invention, the efficiency of an inverter circuit can be improved, utilizing a circuit element with a low breakdown voltage.

1 is a circuit diagram of a DC / AC conversion circuit according to a first exemplary embodiment; 1 is a block diagram of a power supply device according to a first exemplary embodiment.

Embodiment 1
Embodiments of the present invention will be described below with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Moreover, in each drawing, the same code | symbol is attached | subjected to the same element and duplication description is abbreviate | omitted as needed.

  FIG. 1 shows a circuit diagram of an AC / DC converter circuit 1 according to the first exemplary embodiment. As shown in FIG. 1, the AC / DC converter circuit 1 according to the first embodiment includes a first inverter 10, a second inverter 20, a first voltage detection unit 30, a first PWM signal control unit 31, and a first inverter. 2 voltage detector 40, second PWM signal controller 41, correction value generator 50, first capacitor C1, and second capacitor C2. The AC / DC converter circuit 1 has input terminals TM1 and TM2, and an input voltage Vin is applied via the input terminals TM1 and TM2. The input terminal TM1 is connected to the high potential side power supply wiring NDH, and the input terminal TM2 is connected to the low potential side power supply wiring NDL. In the following description, a voltage applied to the high potential side power supply wiring NDH is referred to as a high potential side DC voltage, and a voltage applied to the low potential side power supply wiring NDL is referred to as a low potential side DC voltage. Further, the voltage difference between the high potential side DC voltage and the low potential side DC voltage becomes the input voltage Vin.

  The first inverter 10 is connected between the high potential side power supply wiring NDH and the series node NDM. The second inverter 20 is connected between the series node NDM and the low potential side power supply wiring NDL. That is, the first inverter 10 and the second inverter 20 are connected in series between the high potential side power supply wiring NDH and the low potential side power supply wiring NDL.

  The first capacitor C1 is connected between the high potential side power supply wiring NDH and the series node NDM. The second capacitor C2 is connected between the series node NDM and the low potential side power supply wiring NDL. That is, the first capacitor C11 is connected in parallel with the first inverter 10, and the second capacitor C2 is connected in parallel with the second inverter. From another point of view, the first capacitor C1 and the second capacitor C2 are connected in series between the high potential side power supply wiring NDH and the low potential side power supply wiring NDL.

  The first voltage detector 30 detects the first voltage Vc1 generated at both ends of the first capacitor C1. The second voltage detector 40 detects the second voltage Vc2 generated at both ends of the second capacitor C2. The correction value generation unit 50 generates a correction value OFS according to the voltage difference between the first voltage Vc1 and the second voltage Vc2. For example, the correction value generation unit 50 generates the correction value OFS based on the difference obtained by subtracting the first voltage Vc1 from the second voltage Vc2.

  The first PWM signal control unit 31 outputs a PWM (Pulse Width Modulation) signal for controlling the first inverter 10. The first PWM signal control unit 31 receives the duty instruction value for setting the duty ratio of the PWM signal applied to the first inverter 10 and the correction value OFS output from the correction value generation unit 50. Then, the first PWM signal control unit 31 supplies the first inverter 10 with the duty instruction value corrected by the correction value OFS. Specifically, the first PWM signal control unit 31 outputs to the first inverter 10 a PWM signal having a duty ratio corresponding to a duty value obtained by adding the correction value OFS to the duty instruction value.

  The second PWM signal control unit 41 outputs a PWM signal for controlling the second inverter 20. The second PWM signal control unit 41 receives the duty instruction value for setting the duty ratio of the PWM signal applied to the second inverter 20 and the correction value OFS output from the correction value generation unit 50. Then, the second PWM signal control unit 41 supplies the second inverter 20 with the duty instruction value corrected by the correction value OFS. Specifically, the second PWM signal control unit 41 outputs to the second inverter 20 a PWM signal having a duty ratio corresponding to the duty value obtained by adding the correction value OFS to the duty instruction value.

  Note that the duty instruction value received by the first PWM signal control unit 31 and the duty instruction value received by the second PWM signal control unit 41 specify the same duty ratio. In addition, the duty instruction value is generated by an output voltage control unit (not shown).

  Subsequently, circuit configurations of the first inverter 10, the second inverter 20, the correction value generation unit 50, the first PWM signal control unit 31, and the second PWM signal control unit 41 will be described.

  The first inverter 10 includes switching transistors TR11 to TR14 and a transformer T11. The switching transistors TR11 to TR14 are transistors of the same conductivity type. The switching transistor TR11 and the switching transistor TR12 are connected in series between the high potential side power supply wiring NDH and the series node NDM. The switching transistor TR13 and the switching transistor TR14 are connected in series between the high potential side power supply wiring NDH and the series node NDM. A node connecting the switching transistor TR11 and the switching transistor TR12 is connected to one end of the primary coil of the transformer T11. A node connecting the switching transistor TR13 and the switching transistor TR14 is connected to the other end of the primary coil of the transformer T11. In the first inverter 10, the switching transistor TR11 and the switching transistor TR14 are driven by a PWM signal having the same phase, and the switching transistor TR12 and the switching transistor TR13 are driven by a PWM signal having a phase reversed from that of the switching transistors TR11 and TR14. The PWM signal for driving the switching transistors TR11 to TR14 is generated by the first PWM signal control unit 31. That is, in the first inverter 10, the switching transistors TR11 to TR14 and the primary coil of the transformer T11 constitute an H-bridge type drive circuit. The first inverter 10 generates a first AC voltage Vo1 at both ends of the secondary coil of the transformer T11.

  The second inverter 20 includes switching transistors TR21 to TR24 and a transformer T21. The switching transistors TR21 to TR24 are transistors of the same conductivity type. Switching transistor TR21 and switching transistor TR22 are connected in series between series node NDM and low-potential-side power supply line NDL. The switching transistor TR23 and the switching transistor TR24 are connected in series between the series node NDM and the low potential side power supply wiring NDL. A node connecting the switching transistor TR21 and the switching transistor TR22 is connected to one end of the primary side coil of the transformer T21. A node connecting the switching transistor TR23 and the switching transistor TR24 is connected to the other end of the primary coil of the transformer T21. In the second inverter 20, the switching transistor TR21 and the switching transistor TR24 are driven by a PWM signal having the same phase, and the switching transistor TR22 and the switching transistor TR23 are driven by a PWM signal having a phase reversed from that of the switching transistors TR21 and TR24. The PWM signal for driving the switching transistors TR21 to TR24 is generated by the second PWM signal control unit 41. That is, in the second inverter 20, the switching transistors TR21 to TR24 and the primary coil of the transformer T21 constitute an H bridge type drive circuit. The second inverter 20 generates a second AC voltage Vo2 at both ends of the secondary coil of the transformer T21.

  In the AC / DC converter circuit 1 according to the first embodiment, the PWM output from the first PWM signal control unit 31 and the second PWM signal control unit 41 in the steady operation state in which the amplitudes of the AC voltages Vo1 and Vo2 are stable. The duty instruction value is given so that the duty of the signal is 50%.

  The correction value generation unit 50 includes a voltage difference detection unit 51, an error amplifier 52, and a level shifter 53. The voltage difference detector 51 detects the voltage difference between the first voltage Vc1 and the second voltage Vc2 and outputs the detected voltage difference to the error amplifier error amplifier 52. In the AC / DC converter circuit 1 according to the first exemplary embodiment, the voltage difference detection unit 51 outputs a voltage value obtained by subtracting the first voltage Vc1 from the second voltage Vc2 to the error amplifier 52. The error amplifier 52 amplifies the voltage output from the voltage difference detection unit 51 to generate a correction value. The level shifter 53 converts the voltage range of the correction value output from the error amplifier 52 into a voltage in a voltage range suitable for the first PWM signal control unit 31, and also converts the voltage range of the correction value output from the error amplifier 52 into the second voltage range. Is converted to a voltage in a voltage range suitable for the PWM signal control unit 41. In FIG. 1, the same correction value OFS is given to the first PWM signal control unit 31 and the second PWM signal control unit 41, but this is the same as the first PWM signal control unit 31 and the second PWM signal control unit 41. This is to indicate that the correction value given to the signal control unit 41 is a value having the same meaning (for example, the same correction amount) for the first PWM signal control unit 31 and the second PWM signal control unit 41. The voltage is different on mounting.

  The first PWM signal control unit 31 includes an adder 32 and a first PWM signal generation unit 33. The adder 32 outputs a value obtained by adding the correction value OFS to the duty instruction value to the first PWM signal generation unit 33 as a corrected duty instruction value. The first PWM signal generation unit 33 generates a PWM signal having a duty ratio corresponding to the duty instruction value output from the adder 32 and supplies the PWM signal to the first inverter 10.

  The second PWM signal control unit 41 includes a subtractor 42 and a second PWM signal generation unit 43. The subtractor 42 outputs a value obtained by subtracting the correction value OFS from the duty instruction value to the second PWM signal generation unit 43 as a corrected duty instruction value. The second PWM signal generation unit 43 generates a PWM signal having a duty ratio corresponding to the duty instruction value output from the second PWM signal generation unit 43 and supplies the PWM signal to the second inverter 20.

  Next, the operation of the AC / DC converter circuit 1 according to the first embodiment will be described. The AC / DC converter circuit 1 according to the first embodiment generates AC voltages Vo1 and Vo2 based on the input voltage Vin. Further, in the AC / DC converter circuit 1 according to the first exemplary embodiment, the correction value generation unit 50 causes the first voltage Vc1 generated at both ends of the first capacitor C1 and the second voltage generated at both ends of the second capacitor C2. The deviation from the voltage Vc1 of 2 is eliminated. Here, the operation of generating the alternating voltages Vo1 and Vo2 from the input voltage Vin is based on the PWM signals output from the first PWM signal control unit 31 and the second PWM signal control unit 41, and switching transistors TR11 to TR14, TR21 to Since the operation is performed by driving the TR 24, the operation is substantially the same as that of a general inverter circuit, and thus the description thereof is omitted here. On the other hand, the operation of eliminating the difference between the first voltage Vc1 generated at both ends of the first capacitor C1 and the second voltage Vc2 generated at both ends of the second capacitor C2 is the operation of the AC / DC converter circuit 1. Since this is one of the features, it will be described in detail below.

  Note that the deviation between the first voltage Vc1 and the second voltage Vc2 is, for example, element variation between the first inverter 10 and the second inverter 20, variation in a circuit to which the AC voltages Vo1 and Vo2 are applied, and the like. Caused by

  The AC / DC converter circuit 1 according to the first exemplary embodiment acquires the first voltage Vc1 and the second voltage Vc2 by the first voltage detector 30 and the second voltage detector 40, and the correction value generator 50. Calculates a correction value OFS indicating a correction amount according to the magnitude of the voltage difference between the first voltage Vc1 and the second voltage Vc2. Then, the duty ratio of the PWM signal that drives the first inverter 10 and the second inverter 20 is corrected by the correction value OFS. Here, the first PWM signal control unit 31 outputs, to the first inverter 10, a PWM signal having a duty ratio that is a value obtained by adding the correction value OFS to the duty ratio of the uncorrected PWM signal. Further, the second PWM signal control unit 41 outputs to the second inverter 20 a PWM signal having a duty ratio obtained by subtracting the correction value OFS from the duty ratio of the uncorrected PWM signal.

  As a result, the AC / DC converter circuit 1 according to the first embodiment makes the driving capability of the first inverter 10 smaller than that of the second inverter 20 when the first voltage Vc1 is larger than the second voltage Vc2. Thus, the voltage difference between the first voltage Vc1 and the second voltage Vc2 is reduced. On the other hand, in the AC / DC converter circuit 1 according to the first embodiment, when the second voltage Vc2 is larger than the first voltage Vc1, the driving capability of the second inverter 20 is made smaller than that of the first inverter 10. Thus, the voltage difference between the first voltage Vc1 and the second voltage Vc2 is reduced.

  From the above description, in the AC / DC converter circuit 1 according to the first embodiment, the inverter circuit is connected in series between the high-potential-side power supply line NDH to which the input voltage Vin is applied and the low-potential-side power supply line NDL. In the AC / DC converter circuit 1 according to the first embodiment, two capacitors are connected in series between the high-potential side power supply line NDH to which the input voltage Vin is applied and the low-potential side power supply line NDL. Thereby, in the AC / DC converter circuit 1 according to the first exemplary embodiment, the input voltage Vin can be distributed to each inverter and each capacitor. It can be made smaller than Vin. Thereby, in the AC / DC converter circuit 1 according to the first exemplary embodiment, an element having a withstand voltage lower than the input voltage Vin can be used as a circuit element and a capacitor constituting the inverter circuit.

  Moreover, the efficiency of the AC / DC converter circuit 1 can be increased by configuring the inverter circuit with elements having a low withstand voltage. Furthermore, the volume at the time of mounting of the AC / DC converter circuit 1 can be suppressed by configuring the inverter circuit with an element having a low withstand voltage.

  Further, in the AC / DC converter circuit 1 according to the first embodiment, even if the duty of the PWM signal for operating the first inverter 10 and the second inverter 20 is fixed to 50% in the steady operation state, the first inverter 10 and the voltage applied to the second inverter 20 can be made uniform. That is, in the AC / DC converter circuit 1 according to the first embodiment, complicated control such as controlling the duty ratio of the PWM signal is performed in order to align the voltages applied to the first inverter 10 and the second inverter 20. It is unnecessary.

  Further, the AC / DC conversion circuit 1 according to the first embodiment includes the correction value generation unit 50, the first PWM signal control unit 31, and the second PWM signal control unit 41, so that both ends of the first capacitor C1. The voltage shift between the first voltage Vc1 and the second voltage Vc2 generated at both ends of the second capacitor Vc2 can be eliminated. In this way, by eliminating the deviation between the first voltage Vc1 and the second voltage Vc2, the element constituting the first inverter 10, the element constituting the second inverter 20, the first capacitor C1, and As the second capacitor C2, the withstand voltage margin is reduced, and the use of a low withstand voltage element is facilitated.

  Further, the AC / DC converter circuit 1 according to the first embodiment does not use a pulse signal in order to eliminate the deviation between the first voltage Vc1 and the second voltage Vc2, thereby increasing switching noise. There is no.

  Here, the AC / DC converter circuit 1 according to the first embodiment is suitable for use as an inverter circuit in the power supply device. FIG. 3 shows a block diagram of a power supply device using the AC / DC converter circuit 1 according to the first embodiment. As shown in FIG. 3, in the power supply device using the AC / DC converter circuit 1 according to the first embodiment, a DC signal (for example, the input voltage Vin) given to the AC / DC converter circuit 1 is changed to an external AC signal Vs. It is generated by the AC / DC conversion circuit 3 for conversion. In the power supply device according to the first embodiment, the converter circuit 4 is used to convert the two AC signals Vo1 and Vo2 output from the AC / DC converter circuit 1 into DC voltages, and to synthesize the converted DC voltages. The output voltage VL given to the load 5 is generated by

  As described above, by using the AC / DC converter circuit 1 according to the first embodiment, it is possible to realize a reduction in the size and efficiency of the power supply device.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 AC / DC conversion circuit 2 AC power supply 3 AC / DC conversion circuit 4 Converter circuit 5 Load 10 1st inverter 20 2nd inverter 30 1st voltage detection part 31 1st PWM signal control part 32 Adder 33 1st PWM signal generation unit 40 Second voltage detection unit 41 Second PWM signal control unit 42 Subtractor 43 Second PWM signal generation unit 50 Correction value generation unit 51 Voltage difference detection unit 52 Error amplifier 53 Level shifter NDH High potential side power supply Wiring NDL Low-potential side power supply wiring NDM Series node

Claims (4)

A high potential side power supply wiring to which a high potential side DC voltage is input;
Low potential side power supply wiring to which the low potential side DC voltage is input,
A first inverter connected between the high potential side power supply wiring and a series node;
A second inverter connected between the series node and the low potential side power supply wiring;
A first capacitor connected in parallel with the first inverter;
A second capacitor connected in parallel with the second inverter;
A first voltage detector for detecting a first voltage generated across the first capacitor;
A second voltage detector for detecting a second voltage generated across the second capacitor;
A correction value generating unit that generates a correction value according to the magnitude of the voltage difference between the first voltage and the second voltage;
A PWM signal having a duty ratio corresponding to a duty value obtained by adding the correction value to a duty instruction value for setting a duty ratio of a PWM signal for controlling the first inverter and the second inverter is output to the first inverter. A first PWM signal controller that
A second PWM signal control unit that outputs a PWM signal having a duty ratio corresponding to a duty value obtained by subtracting the correction value from the duty instruction value to the second inverter;
A DC-AC conversion circuit.   The DC / AC conversion circuit according to claim 1, wherein the correction value generation unit generates the correction value according to a difference value obtained by subtracting the first voltage from the second voltage.   The said 1st inverter and the said 2nd inverter respectively comprise the H bridge type drive circuit which drives the primary side coil of the transformer provided correspondingly by these switching transistors. DC / AC converter circuit. DC-AC conversion circuit according to any one of claims 1 to 3,
An AC / DC converter circuit that converts an AC signal applied from the outside into a DC signal and applies the signal to the DC / AC converter circuit;
A converter circuit for converting the AC voltage output by the first inverter and the second inverter to a DC voltage by the DC / AC conversion circuit, and forming the converted DC voltage to drive a load;
A power supply unit having

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