JP2001320880A - Rectifying power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a control apparatus for converting an AC input current waveform of the rectifying power supply to a sine wave. SOLUTION: A control apparatus is formed using a current feed forward control method for injecting an information SI corresponding to the peak value of an input current sensed with DCCT to a control loop of a rectifying power supply output, an error amplifying circuit D1, a pulse converting circuit D2 and a semiconductor switch Q to form a constant voltage feedback control circuit of an output DC voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectified power supply for converting AC power into DC power, and more particularly, to a rectified power supply having a function of suppressing harmonic components contained in an AC input current.

[0002]

2. Description of the Related Art A non-linear load supplied with power from a commercial power system has a characteristic that even when a sine wave voltage is applied, a flowing current becomes a distorted wave containing a large amount of harmonic components. The distorted wave current induces harmonic pollution through the commercial power system. In order to eliminate the occurrence of this pollution, it is effective to suppress the generation of the harmonic current in each electronic device which is a harmonic generation source, and a response is required of a manufacturer of the electronic device. Specifically, it is necessary to take measures to prevent the harmonic current from flowing to the rectified power supply that is provided at the power receiving end of each electronic device and converts an AC voltage to a DC voltage and supplies power to an electronic circuit in the electronic device. Have been.

First, a description will be given of a conventional constant voltage rectifier power supply having no function of suppressing harmonics of an AC input current shown in FIG.
An AC power supply 1 is generally a commercial AC power supply.
2 is a rectified power supply. 3 is a load. The rectification power supply 2 includes a diode rectification circuit 21, a control conversion circuit 22 including a step-up chopper, and a control device CONTX1. 21
And 22 constitute a power conversion circuit for converting an AC voltage into a DC voltage.

Next, the operation of the power conversion circuit will be described.
While the semiconductor switch Q is turned on, the AC power supply 1
DC voltage VDC obtained by rectifying voltage VAC is applied to reactor L, and current IDC increases. During this time, the electric power stored in the capacitor C is supplied to the load 3, and the voltage VC gradually decreases. Next, when the switch Q is turned off, the reactor L
, A voltage of the polarity shown is induced, and this and the DC voltage VDC
The capacitor C is charged with the sum of the above voltages, that is, the voltage boosted from VDC. During this time, the current of the reactor L decreases. Further, the capacitor C is charged with the remaining current obtained by subtracting the discharge current to the load 3 from the current L, and the voltage VC increases. When the switch Q is turned on again, the state returns to the initial state. By repeating the on / off operation of the switch Q, the voltage of the capacitor C, that is, the power supply voltage to the load 3 is kept constant.

Next, the control unit CONTX1 will be described. The voltage VC1 obtained by dividing the output voltage VC and the voltage EREF of the reference DC voltage source E are input to the error amplifier D1 and the signal S
Get MODV. Using this signal SMODV as a modulation signal, the output signal SC of the high-frequency triangular-wave signal generator OSC and a pulse converter D2 composed of a comparator are input to SM.
An ON signal is output during the period of ODV> SC, and SMODV <S
In the period C, a pulse-width-modulated signal SPWM that becomes an off signal (zero voltage) is obtained. The semiconductor switch Q is turned on and off by the SPWM.

FIG. 9 shows the waveforms of the input and output signals of the pulse converter D2 and the voltage and current waveforms of the input and output of the power conversion circuit.
The pulse width control signal SPWM becomes high level during a period when the level of the modulation signal SMODV is higher than the high frequency triangular wave signal SC, and the SPWM becomes zero level in other periods. SMO
SP when DV signal level increases from solid line to dashed line
The width of the high level of the WM is expanded. Also, as indicated by the broken line, S
As the MODV decreases, the width of the SPWM decreases. Signal S
The current IDC flowing through the reactor L is increased or decreased by changing the width of the PWM.

The following relationship exists between the input and output of the error amplifier D1. SMODV = EREF + (EREF−VC1) × GV (1) Here, GV is the amplification factor of D1. When the output voltage VC1 becomes lower than the reference voltage EREF, SMODV increases above EREF, and the pulse width of the SPWM signal obtained by using this as a modulation signal is expanded. When VC1 becomes higher than EREF, SMODV becomes smaller than EREF, and the pulse width of SPWM is reduced.

In this rectified power supply, the output voltage VC is controlled to be constant. However, as shown in the figure, even if the amplitude of the input power supply voltage VAC changes sinusoidally, the modulation signal SMODV is constant, so that the input AC current The waveform of IAC cannot be controlled. In other words, the waveform of the AC input current IAC is a pulsed distortion wave containing a large amount of harmonic components.

An electronic circuit having the same function as that of the control device CONTX1, that is, receiving an output DC voltage and outputting a pulse signal subjected to pulse width modulation, is integrated and put on the market as a semiconductor integrated circuit IC for a switching power supply. I have. Although this integration contributes to the simplification and downsizing of the switching power supply, the input current of the power conversion circuit cannot be converted into a sine wave with this IC alone.

Next, a description will be given of a technique for suppressing a harmonic of an input current waveform required to be applied to a rectified power supply having a constant voltage.
As a means for suppressing harmonics included in the AC current waveform, a method of converting a current waveform into a sine wave is used. It is most desirable that the current waveform be sinusoidal, that is, only the fundamental frequency component, since it does not contain harmonics. The principle of the sine wave technology will be described with reference to FIG. The input current waveform of the constant voltage rectified power supply in FIG. 8 has a pulse shape as shown by the solid line IAC in FIG. In order to convert the IAC into a sine wave, a current feedback control loop is configured to perform a follow-up control so that the instantaneous value of the IAC matches the reference sine wave pattern I × SIN (ωT). Here, I is the amplitude of the current, and ωT is the frequency of the input AC voltage. By this follow-up control, the current amplitude is suppressed in a large current range as shown by the arrow in the drawing, and the current amplitude is increased during a period when the current is not flowing or is small even if it is flowing. The effective value of the input current required by the rectified power supply is ensured by adjusting the amplitude I of the reference sine wave.

FIG. 11 shows an example of the configuration of a constant voltage rectifier power supply that performs current waveform tracking control. The control device CONTX2 is C in FIG.
The configuration is such that ICONTX is added to ONTX1. An oscillator D6 generates a half-wave sine wave signal SIN synchronized with the AC input voltage. The signal SMODV for controlling the constant voltage and the SIN is input to the multiplier D5, and a signal ISIN obtained by multiplying the signal SMODV is output. Sine wave current reference I × SIN (ω
T) (FIG. 10), the magnitude of the amplitude I is determined by the signal SMODV for controlling the output DC voltage to be constant, and the similar sinusoidal waveform SIN (ωT) is determined by the signal SIN synchronized with the AC input.

A current flowing through the reactor L is measured by a DC current transformer DCCT, which is a current sensor, and is converted into a voltage. If necessary, a current signal SI amplified by an amplifier D4 is obtained. An error amplifier D3 amplifies the difference between the current reference ISIN and the current signal SI to obtain a signal SMODI. SMODI is used as a modulation signal, and this and the high-frequency triangular-wave signal SC are input to a pulse converter D2 to obtain a PWM signal SPWM that is pulse-width modulated. With this signal SPWM, the semiconductor switch Q of the rectified power supply
Is turned on and off. FIG. 12 shows the operation waveform of each part of the rectified power supply. The waveform of the modulation signal SMODI has a lower level at the center of the sine wave half-wave output and acts so as to suppress the amplitude of the current IDC.
Acts to increase the amplitude of C. That is, it acts so as to approach a sine wave.

Comparing the modulated signal which is the input of the pulse converter D2, when the constant voltage control shown in FIG.
In contrast to the ODV, in the case of the current waveform control of FIG. 12, the instantaneous value changes like SMODI, and this change has the effect of making the input current waveform a sine wave.

In the rectified power supply shown in FIG. 11, a DC sensor which is a DC sensor is used to obtain information on the current IDC flowing through the reactor L.
Although CT is used, other methods have been used. FIG.
In this example, a current transformer CT as an AC sensor is inserted into an AC input circuit of a diode rectifier circuit to obtain current information.
Since the output of the CT is an AC voltage, the voltage signal is rectified and converted into a DC signal to obtain a current signal required by the control unit CONTX2.

A so-called boost chopper for boosting and outputting an input voltage is used for the control conversion circuit 22 shown in FIGS. 8 and 11, and various circuits are practically used for this control conversion circuit. . Fig. 1 for lower input voltage and output
The so-called step-down chopper 23 is also used as a control conversion circuit.

FIG. 15 shows an example of a power conversion circuit in which a control rectifier 24 is constructed by integrating both the diode rectifier circuit 21 and the boost chopper 22 in FIG. During the period when the AC voltage has the polarity shown, the reactor L and the semiconductor switch Q3
And the diode D2 operate as a step-up chopper, and the reactor L, the semiconductor switch Q2, and the diode D3 operate as a step-up chopper during a period when the AC voltage has a polarity opposite to that shown in the figure. The SPWM signal from the control device CONTX2 determines the polarity of the AC voltage VAC and gives it to Q2 or Q3.

In a rectified power supply, it may be required to insulate the input and the output in a DC manner. FIG. 16 shows a configuration example of the rectified power supply in this case. Push-pull DC-DC
A converter 25 is used instead of the control conversion circuit 22 of FIG. The semiconductor switches Q4 and Q5 are alternately high-frequency switched to generate a high-frequency alternating current, which is
The primary and secondary windings transform the voltage to a desired level and rectify and smooth the output on the secondary side to obtain an isolated DC voltage. It is necessary to insulate the output side and the input side by this circuit, and the control device (CONTX2 in FIG. 11) is separated into an input part CONTX4 and an output part CONTX3, and the both are electrically insulated. For this insulation, a method is generally employed in which an electric signal is converted into an optical signal and transmitted and received. Transmission and reception of optical signals are performed using a photocoupler.

[0018]

In order to suppress the harmonic current with the conventional rectified power supply, a sine wave signal generator synchronized with the AC input voltage is required, and the amplitude of the sine wave signal is reduced. The control device becomes complicated because a multiplier for controlling is required. This imposes a heavy burden on small-capacity rectified power supplies provided in small electronic devices such as televisions and personal computers. Therefore, a control technology capable of suppressing the harmonic current with a simple control device without using a reference sine wave signal synchronized with the AC input voltage and without using a multiplier for controlling the amplitude of the sine wave signal is realized. That is the task.

[0019]

In order to obtain a simpler control device as compared with the conventional current feedback control method,
Uses feed-forward current control technology that can take a simple configuration. That is, the input current waveform is converted into a sine wave without using the reference current waveform signal and the multiplier.

First, the technical background and principle of the present invention will be described. (1) In a rectified power supply that efficiently converts power using a semiconductor switch, the input active power is proportional to the output power according to the law of conservation of energy. (2) Therefore, even if the waveform of the input current is manipulated, the fundamental wave current component in phase with the voltage does not change.

A conventional current waveform shaping technique that constitutes a conventional input current waveform feedback control loop makes the in-phase fundamental wave current component determined by (2) obvious and uses this as a reference current pattern I × SIN (ωT) (FIG. Use as 10)
It is a method of generating a sine wave current by controlling the instantaneous value of the actual current to follow this pattern, and generating no harmonics.
This is a direct sinusoidal control method. Control actions are taken to suppress the pressure at the center and increase the pressure at both ends, as indicated by the arrows in FIG.

In contrast, the present invention uses the principle of an active filter. This is a method in which a sinusoidal current having the same phase as the voltage is not revealed, that is, a sinusoidal current pattern is not used. The harmonic current component is suppressed by suppressing the amplitude of the pulse current, and as a result, the in-phase fundamental wave current, which is the remaining component, emerges. This is a technique that provides the effect of an active filter, and is an indirect current waveform shaping method.

This is shown by voltage and current waveforms in FIG. By suppressing the peak value of the pulse current, a fundamental wave current component included in the pulse current emerges as a result. It does not take the action of directly increasing the pulse width as indicated by the dashed arrow, but by suppressing the peak of the current waveform, the fundamental wave component becomes dominant, as if the pulse width was increased. In order to suppress the peak of the current, a feed-forward control technique of adding or subtracting instantaneous information of the current to a feedback loop of the constant voltage control is used.

Hereinafter, a specific method for reducing the peak value of the pulse current which is the input of the rectified power supply by feedforward control will be described with reference to an embodiment. According to the present invention, information proportional to the instantaneous value of the pulse current is taken in and the semiconductor switch is turned on and off. As a result, the higher the instantaneous value of the current is, the higher the suppression effect is, so that the peak value of the current waveform is suppressed.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a rectified power supply comprising a power conversion circuit and a control device for controlling the power conversion circuit. The power conversion circuit comprises a semiconductor switch, a diode, a reactor and a capacitor, and converts an AC voltage into a DC voltage. After converting and outputting, the control device generates a PWM control signal from the modulation signal and outputs the PWM control signal to the semiconductor switch. The modulation signal is obtained by adding or subtracting a signal proportional to the current flowing through the reactor to the constant voltage feedback control circuit. It is characterized by generating.

A first example of a control device constituting the present invention is as follows.
A modulation signal is generated by amplifying a difference between a signal obtained by adding a signal proportional to a current flowing through a reactor of the power conversion circuit to a DC voltage output from the power conversion circuit and a DC reference signal.

A second example of the control device constituting the present invention is as follows.
Using a semiconductor integrated circuit for a switching power supply having a DC voltage input terminal and generating a PWM control signal, adding a signal proportional to a current flowing through a reactor constituting the power conversion circuit to a DC voltage of a power conversion circuit output The obtained signal is input to the DC voltage input terminal.

A third example of the control device constituting the present invention is as follows.
A modulation signal is generated by subtracting a signal proportional to a current flowing through a reactor constituting the power conversion circuit from a signal obtained by amplifying a difference between a DC voltage of a power conversion circuit output and a DC reference signal. I have.

[0029]

FIG. 2 shows an example of a rectified power supply using a diode rectifier circuit 21 as a power conversion circuit and a boost chopper as a control conversion circuit 22 as a first embodiment of the present invention. Control device CO
NT1 uses an amplifier D4 as a conventional control unit CONT of FIG.
The configuration is added to X1.

FIG. 3 is a waveform example for explaining the rectified power supply of FIG. The operation will be described. 2, an AC voltage VAC of an AC power supply 1 is converted into a DC voltage VDC by a diode rectifier 21. The control conversion circuit 22 uses the DC voltage V
It receives DC and converts it into a constant DC voltage VC to feed the load 3. The semiconductor switch Q constituting the control device 22 is a control device CO
Upon receiving the drive signal SPWM from the NT1, it is turned on during the period when the voltage of the SPWM is output, and is turned off during the period when the voltage is not output.

During the period when Q is on, voltage VDC is applied to reactor L, and current IDC flowing through L gradually increases.
Increases the amount of energy stored in the vehicle. During this time, the load 3 is supplied with the voltage VC of the capacitor C, and the VC gradually decreases. Next, when the semiconductor switch Q turns off, the current IDC of the reactor L flows to the capacitor C through the diode D. During this time, a voltage having the illustrated polarity is induced in the reactor L, and this voltage and VDC are added to charge the capacitor C. That is, the input voltage VDC is boosted to become the voltage VC of the capacitor C. As the energy stored in reactor L is released, current IDC decreases. Further, the voltage VC increases with the charging of the capacitor C. Next, the semiconductor switch Q is turned on again to return to the initial state. Hereinafter, this cycle is repeated.

When the ratio between the ON period and the OFF period of the semiconductor switch Q is changed, the DC output voltage VC changes, and the input current IDC and IAC change according to the law of conservation of energy. The drive signal SPW which is the output of the control device CONT1
M keeps the DC output voltage VC constant and the input current I
The on / off ratio is adjusted so that the AC waveform becomes a sine wave.

Next, the operation of the control unit CONT1 will be described. A voltage VC1 obtained by dividing the DC output voltage VC as necessary into an error amplifier D1 and a signal ERE serving as a reference for the DC output.
And F, and amplifies the difference to output a signal SMODV. SMODV is a signal that maintains VC at a desired level, and is constant in a steady state. DC current transformer DC
CT senses the current IDC flowing through the reactor L,
If necessary, the signal is amplified using the amplifier D4 to obtain a voltage signal SI proportional to the current IDC. The signal SI is subtracted from the signal SMODV to obtain a signal SMODI, which is used as a modulation signal.

The modulated signal SMOD is supplied to the pulse converter D2.
I and a high-frequency triangular wave signal SC are input to drive signal SPW
Get M. SPWM is an ON signal when SC <SMODI, and is an OFF signal when SC> SOMDI. FIG. 3 shows waveform examples of these signals. The modulation signal SMODI has a level lower than the signal SMODV by SI. The degree of this level decrease is proportional to the amplitude of the current IDC of the reactor L. Therefore, the greater the instantaneous level of the amplitude of the IDC, the greater the effect of reducing the current IDC.

The modulation signal SMODI is obtained by subtracting (subtracting) the signal SI proportional to the instantaneous current of the reactor from SMODV, which is the output of the amplifier D1 that amplifies the error between the output voltage VC1 and the reference voltage EREF. Are in a relationship. SMODI = SMODV−SI = EREF + (EREF−VC1) × GV−SI (2) where GV is the amplification factor of the error amplifier D1. Compared to the constant voltage control device (Equation (1)), the pulse converter D
2, the signal SMODI used as the modulation signal is reduced by the current signal SI. This causes a change in the instantaneous value of the current waveform corresponding to SI. That is, an effect of current waveform shaping can be obtained.

Next, a second embodiment of the present invention shown in FIG. 4 will be described. Equation (2) can be modified as follows. SMODI = EREF + ｛EREF− (VC1 + SI /
GV)｝ × GV This equation shows that the same effect as equation (2) can be obtained even if the current signal is added at the input side of the error amplifier D1. However, the level of the current signal is set as low as SI / GV. FIG. 4 shows an embodiment adopting this method. Here, the relationship with the signal in FIG. 2 is SIO = SI / GV.

Next, a third embodiment of the present invention shown in FIG. 5 will be described. A resistor SR is used instead of the DCCT of FIG. The voltage drop (SR × IDC) generated in the resistor SR is a voltage signal proportional to the current IDC flowing through the reactor L, and is information similar to the signal SI (FIG. 2) or SIO (FIG. 4) from the DCCT. Since the voltage dividing resistor of the output voltage sensor and the SR of the current sensor are directly connected, the voltage reference point (GND) is shifted to the diode rectifier circuit side as shown in FIG. 5 so that the sum of the two voltages (VC1 + SR × IDC) ) Can be easily obtained. If the sum voltage is used as an input to the amplifier circuit D1, the same effect as in the embodiment of FIG. 4 can be obtained.

The control device CO in the embodiment shown in FIGS.
NT2 may have the same configuration as the conventional control device CONTX1 of FIG. Therefore, a semiconductor integrated circuit IC for switching power supply control having no input current waveform shaping function on the market can be adopted as the CONT2. This can greatly simplify the control device.

In the above embodiments, the current sensor for sensing the current flowing through the reactor of the control conversion circuit 22 is provided in the circuit 22, but if voltage information similar to the current waveform obtained here can be obtained, The same effect as that of the embodiment can be obtained by sensing with another part, for example, an AC input circuit as shown in FIG.

In the control device which is a component of the present invention, the control conversion circuit 22 used in combination is not limited to the step-up chopper. A similar effect can be obtained by combining a step-down chopper (for example, 23 in FIG. 14) or a control rectifier (for example, 24 in FIG. 15) in which 21 and 22 are integrated.

The load 3 shown in the embodiment of the present invention is not limited to a passive circuit. When a high precision voltage with little ripple and noise is required for the DC output, a DC-DC converter 4 is provided on the output side of the rectified power supply 2 of the present invention as shown in FIG. And DC-DC
The converter 4 employs a method of increasing the accuracy and sharing the insulation between the input and output. As a result, a rectified power supply that generates less harmonic current at the input, is insulated from the input, and has an arbitrary voltage level can be configured. This is an example in which a DC-DC converter is used as the load 3. The load 31 is a load of the DC-DC converter.

When an AC output is required as in a constant voltage / constant frequency power supply CVCF or a high frequency inverter, a DC-AC converter 5, a so-called inverter, is provided on the output side of the rectified power supply 2 of the present invention as shown in FIG. A method of providing a high-precision alternating current by providing it is adopted. As a result, an AC power supply that generates an AC having a small frequency of the input harmonic current and an AC having a desired frequency or high frequency and voltage accuracy is configured. This is an example in which a DC-AC converter is used as the load 3. The load 32 is a load of the DC-AC converter.

In the drawings so far, a bipolar transistor is illustrated as the semiconductor switch Q constituting the control conversion circuit 22, but a power MOSFET, IGBT, GT used as a semiconductor switch in a general power converter.
Similar effects can be obtained by replacing the power semiconductor element such as O.

[0044]

In the rectified power supply, a control device is constructed by injecting a voltage signal proportional to the instantaneous value of the current flowing through the reactor of the control conversion circuit into the constant voltage feedback control circuit. Thus, the waveform distortion of the AC input current can be reduced without complicating the configuration. For example, when a conventional feedback control circuit is configured to control the input current waveform, a sine wave voltage signal generation circuit synchronized with the input AC voltage, a multiplication circuit that varies the amplitude of the sine wave voltage signal, and the like are used. Although necessary, they are not used in the present invention. Therefore, it contributes to improving the reliability of the device and reducing the cost of the device. When the present invention is applied to a small-capacity rectified power supply provided in home appliances and electronic devices, a great effect is obtained. In particular, if a combination of semiconductor integrated circuits for controlling switching power supplies on the market is used, rectification power supplies that must be mounted in the device space of extremely limited electronic equipment will greatly contribute to miniaturization. .

[Brief description of the drawings]

FIG. 1 is a drawing for explaining the principle of the present invention.

FIG. 2 shows a first embodiment of the present invention.

FIG. 3 is an operation waveform diagram for explaining the first embodiment of the present invention.

FIG. 4 shows a second embodiment of the present invention.

FIG. 5 shows a third embodiment of the present invention.

FIG. 6 shows a fourth embodiment of the present invention.

FIG. 7 shows a fifth embodiment of the present invention.

FIG. 8 is a conventional example of a rectified power supply for controlling the output to a constant voltage.

FIG. 9 is an operation waveform diagram for explaining FIG. 8;

FIG. 10 is a current waveform diagram showing the effect of feedback control.

FIG. 11 is a conventional example of a rectified power supply that performs feedback control of an input current waveform.

FIG. 12 is an operation waveform diagram illustrating the conventional example of FIG.

FIG. 13 is a conventional example in which a current sensor is arranged in an AC circuit.

FIG. 14 is a conventional example of a step-down chopper circuit forming a control conversion circuit of a rectified power supply.

FIG. 15 shows a conventional example in which a diode rectification circuit of a rectification power supply and a control conversion circuit are integrated.

FIG. 16 is a conventional example in which a control conversion circuit of a rectified power supply has an insulation function between input and output.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 AC power supply 2 Rectifier power supply 21 Diode rectifier circuit 22 Control converter circuit CONT controller 3 Load L Reactor C Capacitor Q Semiconductor switch D Diode E Reference DC voltage source D1, D3 Error amplifier D2 Pulse converter D4 Amplifier OSC high-frequency triangular wave signal generator DCCT DC current transformer CT Current transformer SR Current detection resistor VAC AC voltage at input IAC AC current at input VDC DC output voltage of diode rectifier circuit IDC Current flowing through reactor L VC1 Input signal voltage of controller SPWM Pulse width modulated signal

Claims (4)

[Claims] The power conversion circuit comprises a semiconductor switch, a diode, a reactor, and a capacitor, converts an AC voltage into a DC voltage, and outputs the DC voltage. Creates a PWM control signal from the modulation signal and outputs it to the semiconductor switch,
A rectified power supply, wherein the modulation signal is generated by adding or subtracting a signal proportional to a current flowing through the reactor to or from a constant voltage feedback control circuit. 2. The control device according to claim 1, further comprising: amplifying a difference between a signal obtained by adding a signal proportional to a current flowing through a reactor of the power conversion circuit to a DC voltage output from the power conversion circuit and a DC reference signal. The rectified power supply according to claim 1, wherein: 3. The control device has a DC voltage input terminal and a PW
A signal obtained by adding a signal proportional to a current flowing through a reactor constituting the power conversion circuit to a DC voltage output from a power conversion circuit using a semiconductor integrated circuit for a switching power supply that generates an M control signal, 2. The rectified power supply according to claim 1, wherein the rectified power is input to an input terminal. 4. The control device subtracts a signal proportional to a current flowing through a reactor constituting the power conversion circuit from a signal obtained by amplifying a difference between a DC voltage output from the power conversion circuit and a DC reference signal. 2. A signal as a modulation signal.
Rectified power supply.