JPH1052047A - Power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply unit which can continue operation easily even if a temporary overload condition occurs, when a generator having small output capacity is connected to the input side of a cyclo converter. SOLUTION: A control signal is generated, which controls the amplitude of a sinewave outputted from a sinewave oscillator 13 by an amplitude control circuit 12 according to a control function from a control function calculating circuit 11, and a target wave is outputted according to the control signal by a target wave output circuit 14. The upper and the lower limit values are set for an outputted value from the target wave output circuit 14, so that a larger value than a prescribed upper limit value or a smaller value than a prescribed lower limit value is inhibited from being outputted. Therefore, as an outputted value from a comparator 9 increases to increase the proportional coefficient of a proportional function outputted from a control function computing circuit 11, the wave outputted from the target wave output circuit 14 is shaped from a sinewave to a rectangular wave, so that the waveform outputted from this power supply unit is shaped into a rectangular wave from a sinewave.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply used as a single-phase AC power supply of a commercial frequency or the like, and more particularly to a power supply using a cycloconverter whose input side is constituted by a generator having relatively small output power. In this case, the present invention relates to a countermeasure against withstand voltage of the converter due to a no-load voltage rise caused by a load characteristic.

[0002]

2. Description of the Related Art A device called a cycloconverter is known as a device for directly converting AC power of a constant frequency into AC power of another different frequency.

[0003] Such a conventional cycloconverter normally uses the output of a power line of a commercial frequency or a generator with a large output as an input (for example, Japanese Patent Publication No. 60-16060).
-9429), and is generally used for driving an AC motor.

Hereinafter, the operation principle of the cycloconverter will be described with reference to FIGS.

FIG. 6 is an electric circuit diagram showing an example of the configuration of a conventional cycloconverter.

As shown in FIG. 1, a cycloconverter CC has 12 thyristors SCR.
k ± (k = 1,..., 6), a positive current is output from a bridge circuit (hereinafter referred to as “positive converter”) BC1 composed of six thyristors SCRk +, and the remaining six Circuit (hereinafter referred to as "negative converter") B composed of the thyristor SCRk-
C2 outputs a negative current.

For example, 27 poles driven by an internal combustion engine (of which 3 poles are used to generate a synchronization signal for controlling each gate of the thyristors SCRk ±)
Of the three-phase generator of the three-phase generator is cycloconverter CC
, An AC of 9 cycles is obtained for one rotation of the crankshaft. When the range of the engine speed is set to, for example, 1200 rpm to 4500 rpm (that is, 20 Hz to 75 Hz), the above 3
The frequency of the phase AC output is 180 times, nine times the engine speed.
Hz to 675 Hz.

[0008] The three-pole coil (hereinafter, this coil is called a "sub coil" and the other coil is called a "main coil"
3) (U-phase, V-phase, and W-phase currents) obtained from each of the primary sides of the six photocouplers PCk (k = 1,..., 6) as shown in FIG. Light emitting diode (LED) and six diodes Dk (k = 1,..., 6)
And a three-phase full-wave rectifier circuit FR
Supplied to The three-phase current full-wave rectified by the three-phase full-wave rectifier circuit FR is converted into light by the primary-side LED, and the light output is supplied to each of the secondary-side optical sensors (not shown) of the photocoupler PCk. Is converted to That is,
A current corresponding to the three-phase current that has been full-wave rectified by the three-phase full-wave rectifier circuit FR is extracted by the secondary-side optical sensor. The extracted current is used to generate a synchronization signal (for example, a sawtooth wave) for controlling the conduction angle of each gate of the thyristors SCRk ±, as described later.

FIG. 8 shows the transition of the voltage applied between the U phase, V phase and W phase in FIG.
It is a figure which shows the timing which Ck turns on.

Each line voltage (U-V, U-W, V-W, V
−U, WU, WV) change as shown in FIG. 8, the output waveform that has been full-wave rectified by the three-phase full-wave rectifier circuit FR is the output voltage of each line obtained from the main coil. It is 1/6 of the cycle. For example, if the phase angle is between 60 ° and 120 °
, That is, when the U-V voltage is higher than the other line voltages, the photocouplers PC1 and PC5 are turned on in pairs (the other photocouplers are turned off), and thus 3
A voltage corresponding to the U-V voltage is output from the phase full-wave rectifier circuit FR. That is, since a voltage corresponding to the maximum value of each line voltage is output from the three-phase full-wave rectifier circuit FR, the cycle of this voltage is 60 °, and the cycle of the main coil voltage is 1 °. / 6.

FIG. 8 also shows the timing of turning on each gate of the thyristor SCRk ±, and FIG. 8 shows that the conduction angle of each gate is set in the range of 120 ° to 0 °. The timing at which it is performed is shown.

When a current is output from cycloconverter CC according to this timing, positive converter B
While each gate of C1 is ignited, the cycloconverter C
When absorbing (supplying) current to C, the negative converter B
Each gate of C2 is fired.

It is not necessary to perform the ignition continuously over the range shown in the figure, and the same operation can be obtained even if a pulse shown by oblique lines in the figure is applied to the gate.

FIG. 9 shows that each of the thyristors SC of the positive or negative converters BC1 and BC2 has conduction angles α = 120 ° and 60 °.
It is a figure showing a waveform outputted from cycloconverter CC when Rk ± is fired.

In FIG. 1, (a) shows a conduction angle α = 12.
The waveform output from the cycloconverter CC when each thyristor SCRk + of the positive converter BC1 is fired at 0 ° is shown, and (b) shows the firing of each thyristor SCRk− of the negative converter BC2 at a conduction angle α = 120 °. Shows the waveform output from the cycloconverter CC when
(C) shows a waveform output from the cycloconverter CC when each thyristor SCRk + of the positive converter BC1 is fired at a conduction angle α = 60 °, and (d) shows a negative converter at a conduction angle α = 60 °. Each thyristor SCR of BC2
The waveform output from the cycloconverter CC when k- is fired is shown.

For example, when each thyristor SCRk + of positive converter BC1 is fired at conduction angle α = 120 °, the waveform output from cycloconverter CC has a full-wave rectified waveform as shown in FIG. Becomes Further, when the conduction angle α = 60 °, each thyristor S of the positive converter BC1
When the CRk + is fired, the waveform output from the cycloconverter CC becomes a waveform containing a large amount of harmonic components as shown in FIG.
When a high-cut filter is connected to the output side of C, this harmonic component is removed, and the average voltage is output. As described above, when the input generator is a 27-pole three-phase generator and the engine speed is 3600 rpm, the frequency of the fundamental wave of the harmonic is as follows.

60 Hz (= 3600 rpm) × 9th harmonic ×
3 phase × 2 (full wave) = 3.24 kHz Then, the conduction angle α of the positive converter BC1 is set to 0 ° to 120 °.
By changing the angle in the range of °, the cycloconverter CC can output any positive voltage having an average voltage in the range of 0 V to the full-wave rectified voltage. Also, by changing the conduction angle α of the negative converter BC2 in the same manner, the cyclo converter CC can output any negative voltage whose average voltage is in the range of 0 V to the full-wave rectified voltage.

Next, a method of changing the conduction angle α in the range of 0 ° to 120 ° will be described.

FIG. 10 is a diagram showing a reference sawtooth wave generated for controlling the conduction angle α. The reference sawtooth wave in FIG. 10 is detected by the secondary-side optical sensor of the photocoupler PCk in FIG. Is generated based on the applied current.

Thyristor SCR1 of positive converter BC1
The reference sawtooth wave corresponding to + has a conduction angle α of 120 ° or more.
In the range of 0 °, a sawtooth wave which becomes 0V when α = 0 ° corresponds. Then, sawtooth waves having a phase difference of 60 ° are respectively applied to the thyristors SCR1 +, 6+, 2+,
4+, 3+, and 5+ correspond to each thyristor SCRk + in this order.

On the other hand, the thyristor S of the negative converter BC2
For the CR1-, a sawtooth wave is generated which is vertically symmetrical with respect to the thyristor SCR1 + and whose phase is shifted by 180 °. Then, similarly to the positive converter BC1, the sawtooth waves having a phase difference of 60 °
-, 6-, 2-, 4-, 3-, 5- correspond to each thyristor SCRk- in this order.

As described above, the reference waveform is composed of 12 sawtooth waves corresponding to each thyristor SCRk ± of the positive and negative converters BC1 and BC2. These sawtooth waves are compared with the target waveform r by 12 types of comparators (not shown), and the intersection (for example, the point TO in the thyristor SCR1 +) is set in each thyristor SCR.
The conduction angle is k ±.

By taking a sine wave as the target wave and changing the conduction angle α to a sine wave, a sine wave output can be obtained from the cycloconverter CC as shown in FIG. If the frequency of the input waveform is, for example, 540
Hz, and when a sine wave output of 50 Hz is obtained from this input waveform, a waveform obtained by connecting about 65 parts of the input sine wave together.

[0024]

When the output of the cycloconverter is used as such a sinusoidal single-phase alternating current, the cycloconverter does not have a place for storing energy. Will also change sinusoidally.

Therefore, when a small-sized output, for example, a generator of several hundred to several kW is connected to the input side of the cycloconverter to output a single-phase sine wave, the input energy can be used except for the peak portion of the sine wave. Because of this, the utilization efficiency is very poor, and the output that can be taken out as single-phase AC becomes very small.

In particular, when a magnet generator is used as the above-mentioned small-output generator, its energy is limited. For example, even if a temporary large current at the time of starting when a motor load is connected is overloaded, There were problems such as inoperability due to the state.

The present invention has been made in view of the above-mentioned problems, and when a generator having a small output capacity is connected to the input side of a cycloconverter, even if a temporary overload state occurs,
An object of the present invention is to provide a power supply device capable of continuing operation without difficulty.

[0028]

In order to achieve the above object, the present invention provides a three-phase generator and a three-phase winding output of the generator, which are connected in anti-parallel to each other to output a single-phase current. And a set of variable control bridge circuits constituting a cycloconverter. The variable control bridge circuits connected in anti-parallel to each other are alternately switched every half cycle of the current supplied to the load to operate the single phase. In a power supply device that outputs an alternating current, the output voltage waveform of the variable bridge circuit is changed from a sine wave to a rectangular wave whose maximum amplitude is limited by the output voltage as the load increases.

A three-phase generator, and a set of variable control bridge circuits connected to the three-phase winding output of the generator and connected in anti-parallel to each other to constitute a cycloconverter for outputting a single-phase current; A power supply device that outputs a single-phase AC current by alternately switching the variable control bridge circuits connected in antiparallel to each other every half cycle of the current supplied to the load. A target waveform of a drive signal for operating to output AC power is changed from a sine wave to a rectangular wave as the load increases.

Further, preferably, the three-phase generator is a magnet generator having a permanent magnet rotor.

Preferably, the amplitude of the target wave is changed based on a comparison result between the output voltage of the cycloconverter and a set voltage, and the upper limit or the lower limit of the amplitude is limited. The wave shape is changed from a sine wave to a rectangular wave.

[0032]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a power supply device according to an embodiment of the present invention. In the figure, components corresponding to the components described in FIG. , The description of which is omitted.

In FIG. 1, reference numerals 1 and 2 denote output windings wound independently on the stator of the AC generator, respectively.
Reference numeral 1 denotes a three-phase main output winding (main coil), and reference numeral 2 denotes a three-phase auxiliary output winding (sub coil).

FIG. 2 is a sectional view of the AC generator.
In the figure, the three-phase main coil 1 is located at 2 in the area A1.
The three-phase sub-coil 2 is composed of a single-pole coil,
It is composed of coils of three poles in two. The rotor R is formed with eight pairs of permanent magnet magnetic poles, and is configured to be rotationally driven by an internal combustion engine (not shown).

Returning to FIG. 1, the three output terminals U, V, and W of the three-phase main coil 1 are connected to the positive and negative converters B, respectively.
The output side of the cycloconverter CC is connected to an LC filter 3 for removing harmonic components of the output current, and the output side of the LC filter 3 is connected to the input terminals U, V, W of C1 and BC2. The output is connected to an output voltage detection circuit 5 for detecting a voltage corresponding to the current from which the harmonic component has been removed. The negative input terminal of the output voltage detection circuit 5 is connected to the ground GND of the control system.
The output voltage detection circuit 5 is configured to obtain a single-phase output from both positive and negative input terminals.

The output side of the output voltage detecting circuit 5 is connected to an approximate effective value calculating circuit 8 for calculating and outputting an approximate effective value of the output voltage. Connected to the negative input terminal of A reference voltage output circuit 10 for outputting a reference voltage value of the present power supply device is connected to a positive input terminal of the comparator 9, and an output side of the comparator 9 is
Control function according to the comparison result (for example, proportional function)
And a control function calculation circuit 11 for calculating and outputting.

The output side of the control function operation circuit 11 is connected to an amplitude control circuit 12 for controlling the amplitude of a sine wave having a commercial frequency of 50 Hz or 60 Hz output from a sine wave oscillator 13. Is also connected to the output side of the sine wave oscillator 13. The amplitude control circuit 12 outputs an amplitude control signal for controlling the amplitude of the sine wave output from the sine wave oscillator 13 according to the control function output from the control function operation circuit 11.

The output side of the amplitude control circuit 12 is connected to a target wave output circuit 14 for outputting a target wave according to the output signal (amplitude control signal). The output side of the target wave output circuit 14 is connected to a cycloconverter CC. Each thyristor S constituting
Conduction angle control unit 15 for controlling the conduction angle of the gate of CRk ±
And the positive input terminal of the comparator 16.

The conduction angle control unit 15 includes a positive converter BC1
Gate control unit 15a for controlling the conduction angle of the gate of each thyristor SCRk + (hereinafter referred to as "positive gate")
And a negative gate control unit 15b that controls a conduction angle of a gate (hereinafter, referred to as a “negative gate”) of each thyristor SCRk− of the negative converter BC2.

Each of the gate control units 15a and 15b has six comparators (not shown). Each of the comparators, as described with reference to FIG. (Reference sawtooth wave), and when the two coincide, the gate is fired.

The output side of the output voltage detecting circuit 5 is connected to the negative side input terminal of the comparator 16, and the output side of the comparator 16 is connected to the positive gate control section 15a and the negative gate control section 15a.
b. The comparator 16 compares the voltage output from the output voltage detection circuit 5 with the target wave, and outputs a high (H) level signal or a low (L) level signal according to the comparison result.

When the comparator 16 outputs an H-level signal, the positive gate controller 15a operates, while the negative gate controller 15b stops. When an L-level signal is output, conversely, The positive gate control unit 15a is configured to stop, while the negative gate control unit 15b is configured to operate.

The output side of the three-phase subcoil 2 is connected to, for example, a synchronization signal forming circuit 18 having the three-phase full-wave rectifier circuit FR shown in FIG. Synchronization signal forming circuit 18
Generates and outputs a sawtooth wave shown in FIG. 3 according to the three-phase output from the three-phase subcoil 2.

FIG. 3 is a diagram showing an example of a sawtooth wave in which the conduction angle can be controlled within the range when the control range of the conduction angle of each thyristor SCRk ± is 120 ° to -60 °. 10 differs from the sawtooth wave of FIG. 10 in that the width of the sawtooth wave is enlarged. The reason why the control range of the conduction angle of each thyristor SCRk ± is extended to the negative side with respect to the conventional cycloconverter CC is as follows.

In the conventional cycloconverter CC,
When a control is performed to lower the output voltage when a capacitive load is connected to the output terminal and there is a positive potential on the load side, a discontinuous point occurs in the relationship between the conduction angle of each thyristor SCRk ± and the output voltage. Occurred, and the output voltage could not be stably maintained. That is, in order to lower the output voltage when a positive potential is present on the load side, it is necessary to absorb the positive charge of the load.
Limits the conduction angle α to the range of 120 ° to 0 °, the positive converter BC1 cannot absorb the positive charge of the load, and therefore must be absorbed by the negative converter BC2. When the positive charge is absorbed by the negative converter BC2, as described above, the output current from the negative converter BC2 is -full-wave rectified voltage to 0V, so that the positive potential of the load rapidly drops to 0V. As a result, a discontinuous point occurs in the output voltage. At this time, if the conduction angle is increased from 120 ° to −60 °, the negative converter BC
Since the charge of the load can be absorbed up to the positive voltage in Step 2, no discontinuity point occurs in the output voltage, and the stability of the control can be maintained.

However, when the conduction angle is expanded to the negative side in this way, as shown in FIG.
1 and BC2, the intersection of the target wave r and the sawtooth wave becomes two points TO1 and TO2, and selects either the positive or negative converters BC1 and BC2 and the corresponding thyristor SCRK. I couldn't decide if I should fire the ± gate. Therefore, in the present embodiment, as described above, one of the positive and negative converters BC1 and BC2 is selected according to the comparison result of the comparator 16.

The output side of the synchronizing signal forming circuit 18 is connected to a positive gate control unit 15a and a negative gate control unit 15b. Here, each connection line connecting the synchronization signal forming circuit 18 and each of the gate control units 15a and 15b is composed of six signal lines, and each signal line is connected to the gate control unit 15a and 15b, respectively. Each of the comparators is connected to a sawtooth wave having the timing described with reference to FIG.

The outputs of the six comparators of the positive gate control section 15a are connected to the respective thyristors S of the positive converter BC1.
The outputs of the six comparators of the negative gate controller 15b are connected to the negative converter BC2, respectively.
Of each thyristor SCRk-.

In the present embodiment, the synchronizing signal forming circuit 18 is configured to form a synchronizing signal in accordance with the three-phase output from the three-phase sub-coil 2. However, the present invention is not limited to this.
A single-phase subcoil may be used in place of the phase subcoil 2, and a synchronization signal (reference sawtooth wave) may be formed according to the single-phase output.

Hereinafter, the operation of the power supply device configured as described above will be described.

When the rotor R is driven to rotate by the engine, a voltage is applied between the phases of the three-phase main coil 1 as described above. When each gate of the thyristor SCRk ± is fired by the conduction angle control unit 15, a current is output from the cycloconverter CC in response to the ignition, and the current is filtered by the filter 3 to remove its harmonic components, and the output voltage is reduced. The detection circuit 5 detects the voltage. Each of the detected voltages is output by the approximate effective value calculation circuit 8 after calculating the approximate effective value voltage.

The approximate effective value voltage is calculated by the comparator 9
It is compared with the reference voltage value output from the reference voltage output circuit 10, and a control function (proportional function) is calculated and output by the control function calculation circuit 11 according to the comparison result. More specifically, as the output value from the comparator 9 increases, the control function operation circuit 11
As the difference between the reference voltage output from the circuit and the approximate effective value from the approximate effective value calculation circuit 8 increases, a proportional function that increases the proportional coefficient is calculated and output.

In accordance with the calculated and output control function, the amplitude control circuit 12 generates a control signal for controlling the amplitude of a 50 Hz or 60 Hz sine wave output from the sine wave oscillator 13, and generates a target signal. The wave output circuit 14 outputs a target wave according to the control signal. Here, the output value from the target wave output circuit 14 is provided with upper and lower limits, so that the target wave output circuit 14 cannot output a value larger than the predetermined upper limit or a value smaller than the predetermined lower limit. It is configured. That is, as the output value from the comparator 9 increases and the proportional coefficient of the proportional function output from the control function operation circuit 11 increases, the shape of the target wave output from the target wave output circuit 14 changes from a sine wave. It is transformed into a square wave.

The target wave output from the target wave output circuit 14 is compared with the detection voltage output from the output voltage detection circuit 5 by the comparator 16, and when the voltage of the target wave is higher than the detection voltage, the comparison is performed. When the H level signal is output from the comparator 16 and the positive gate control unit 15a is selected to operate, while the voltage of the target wave is lower than the detection voltage, the L level signal is output from the comparator 16 and , The negative gate controller 15b is selected to operate.

In each of the comparators of the selected gate control unit out of the positive gate control unit 15a and the negative gate control unit 15b, the target wave from the target wave output circuit 14 and the sawtooth wave from the synchronization signal forming circuit 18 are output. The two are compared, and when they match, a one-shot pulse having a predetermined width is output to the gate of the thyristor SCRk ±, and the conduction angle is controlled.

FIG. 5 is a diagram showing an example of a 50 Hz output waveform generated by the power supply device of the present embodiment.
(A) shows an output waveform at the time of no load, (b) shows an output waveform at the time of rated load, and (c) shows an output waveform at the time of overload.

As shown in the figure, when a temporary overload occurs, for example, the reference voltage output from the reference voltage output circuit 10 and the approximate effective value calculation circuit 8 The output waveform is transformed from a sine wave to a rectangular wave according to the difference from the approximate effective value.

In the present embodiment, the shape of the target wave is changed from a sine wave to a rectangular wave in accordance with the state of the load. However, the present invention is not limited to this, and the output voltage is limited by the maximum amplitude. When the power supply device is configured as described above, the amplitude of the target wave may be increased according to the state of the load.

As described above, in the present embodiment, when the load is temporarily increased, the output is increased to near the upper limit of the total input energy from the generator in response to this. Even when a temporary overload state occurs, the operation can be continued without difficulty.

[0061]

As described above, according to the present invention,
As the output waveform of the variable bridge circuit changes from a sine wave to a rectangular wave whose maximum amplitude is limited by the output voltage as the load increases, when a generator with a small output capacity is connected to the input side of the cycloconverter, Even if a temporary overload state occurs, there is an effect that the operation can be continued without difficulty.

The target wave of the drive signal for operating the variable bridge circuit to output AC power changes from a sine wave to a rectangular wave as the load increases, and accordingly, the output waveform output from the power supply unit Also transforms from a sine wave to a rectangular wave, so that an effect similar to the above effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a power supply device according to an embodiment of the present invention.

FIG. 2 is a sectional view of the alternator of FIG. 1;

FIG. 3 shows a control range of the conduction angle of each thyristor of FIG.
It is a figure which shows an example of the sawtooth wave which can perform the conduction | electrical_connection angle control in this range when it is 0 degree --60 degree.

FIG. 4 is a diagram for explaining a problem that occurs when the conduction angle is set to 120 ° to −60 °.

FIG. 5 is a diagram showing an example of a 50 Hz output waveform generated by the power supply device of FIG. 1;

FIG. 6 is an electric circuit diagram showing an example of a configuration of a conventional cycloconverter.

FIG. 7 is an electric circuit diagram showing a configuration of a bridge-type three-phase full-wave rectifier circuit.

8 is a diagram showing a transition of a voltage applied between U phase, V phase and W phase in FIG. 6 or 7, a timing when a photocoupler is turned on, and a timing when each gate of a thyristor is fired.

FIG. 9 is a diagram showing waveforms output from the cycloconverter when the thyristors of the positive or negative converter are fired at conduction angles α = 120 ° and 60 °.

FIG. 10 is a diagram showing a reference sawtooth wave generated for controlling a conduction angle.

FIG. 11 is a diagram illustrating a 50 Hz sine wave generated by the cycloconverter of FIG. 6;

[Explanation of symbols]

 Reference Signs List 1 3 phase main coil (3 phase output winding) 5 output voltage detection circuit 14 target wave output circuit 15 conduction angle control unit 16 comparator BC1 positive converter (variable control bridge) BC2 negative converter (variable control bridge) CC cyclo converter

Claims (4)

[Claims] 1. A three-phase generator, and a set of variable control bridge circuits connected to the three-phase winding output of the generator, connected in anti-parallel to each other, and forming a cycloconverter that outputs a single-phase current. A power supply device that outputs a single-phase AC current by alternately switching the variable control bridge circuits connected in antiparallel to each other every half cycle of the current supplied to the load. A power supply device that changes an output voltage waveform from a sine wave to a rectangular wave whose maximum amplitude is limited by the output voltage as the load increases. 2. A three-phase generator, and a set of variable control bridge circuits connected to the three-phase winding output of the generator, connected in antiparallel to each other, and constituting a cycloconverter that outputs a single-phase current. A power supply device that outputs a single-phase AC current by alternately switching the variable control bridge circuits connected in antiparallel to each other every half cycle of the current supplied to the load. A power supply device, wherein a target waveform of a drive signal for operating and outputting AC power is changed from a sine wave to a rectangular wave as the load increases. 3. The generator according to claim 1, wherein the three-phase generator is a magnet generator having a permanent magnet rotor.
The power supply device according to any one of the above. 4. A method for changing the amplitude of the target wave based on a result of comparison between the output voltage of the cycloconverter and a set voltage, and limiting an upper limit or a lower limit of the amplitude so that the shape of the target wave is sinusoidal. The power supply device according to claim 2, wherein the power is changed from a wave to a rectangular wave.