JPH07131984A - Dc power supply equipment - Google Patents

Abstract

PURPOSE:To reduce a cost for a DC power supply equipment capable of improving an input current waveform and a power factor and also to suppress an increase in higher harmonics component in the input current waveform even though an input AC voltage is high. CONSTITUTION:A switching element 15 is connected to the output of a rectifying circuit 8 for full-wave rectifying AC voltage through a reactor 13. An error output between an output voltage and a reference voltage is synthesized with chopping wave, further instantaneous values of the AC voltage which are synthesized only when the AC voltage is high is given to one of the input terminals of a comparator 25, and a detected value of a current flowing through the switching element 15 is given to the other input terminal of the comparator. A flip-flop 31 is set by the rising of the triangular wave and reset by an output of the comparator 25 to produce PWM wave, and the switching element 15 is ON-OFF controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply device capable of easily achieving improvement of a current waveform in an AC input line.

[0002]

2. Description of the Related Art Turning on a switching element such as a switching regulator or an inverter connected to a rectifier circuit
In order to correct the distortion of the voltage waveform of the AC input line due to the OFF operation, it is known to connect a reactor to the power supply line and control ON / OFF of the switching element connected between the pair of DC output lines of the rectifier circuit. (For example, JP-A-63-190557).

By the way, in the conventional device, it is necessary to form a signal corresponding to the difference between the output voltage and the reference voltage and to multiply this signal by the reference sine wave, which inevitably leads to a complicated circuit configuration. The cost is high.

In order to solve the above problems, the applicant of the present application proposed the DC power supply device shown in FIG. 1 by Japanese Patent Application No. 1-139658.

Next, the DC power supply device of FIG. 1 will be described. This device has a pair of AC power supply terminals 1 and 2 to which a commercial AC power supply of, for example, 50 Hz is connected. The high frequency removing filter 3 connected to the power supply terminals 1 and 2 is composed of reactors 4 and 5 connected in series to the lines and capacitors 6 and 7 connected between a pair of lines.

A full-wave rectifier circuit 8 is provided at the output stage of the filter 3.
Are connected. A reactor 13 as an energy storage element and a reverse current blocking diode 14 are connected in series to one of the pair of DC lines 11 and 12 between the rectifier circuit 8 and the pair of DC output terminals 9 and 10. Output terminal of reactor 13 and lower DC line 12
A switching element 15 composed of an FET and a current detection resistor 16 as a current detector are connected between the and.
The smoothing capacitor 16a is connected between the output terminals 9 and 10 in the output stage of the reverse current blocking diode 14.

Voltage detection circuit 19 including resistors 17 and 18
Is connected between the output terminals 9 and 10, and the voltage detection line 20 is connected to the differential amplifier 22 of the switching element control circuit 21.
Connected to one of the input terminals. A reference voltage source 23 is connected to the other input terminal of the differential amplifier 22.

The current detection line 24 derived from one end of the current detection resistor 16 is connected to one input terminal of the voltage comparator 25. To the other input terminal of the voltage comparator 25, a combining circuit 29 including resistors 27 and 28 is connected to obtain a combined waveform of the triangular wave (sawtooth wave) of the triangular wave generating circuit 26 and the differential output of the differential amplifier 22. ing.

The control pulse forming circuit 30 comprises an RS flip-flop 31, a set signal generating circuit 32 and a reset signal forming circuit 33. The set signal generation circuit 32 forms a set trigger signal in synchronization with the triangular wave of the triangular wave generation circuit 26, and outputs the set trigger signal to the set terminal S of the flip-flop 31.
Give to. Although the set signal generation circuit 32 is shown to be controlled by the triangular wave generation circuit 26 in FIG. 1, a reference oscillator is incorporated in the set signal generation circuit 32, and the flip-flop 31 of the flip-flop 31 is output based on the output clock of the reference oscillator. The triangular wave generation circuit 26 may be controlled while forming the set signal. The reset signal forming circuit 33 outputs a reset trigger pulse to the reset terminal R of the flip-flop 31 in response to the change of the output state of the comparator 25.
Give to. The Q output terminal of the flip-flop 31 is an FET
Is connected to the control terminal (gate) of the switching element 15.

[0010]

[Operation] Next, the operation of the circuit of FIG. 1 will be described with reference to the waveforms of FIG. When a sinusoidal AC voltage is applied to the power supply terminals 1 and 2, the full-wave rectified voltage waveform shown in FIG. 2A is obtained at the output stage of the rectifier circuit 8. If this voltage waveform is interrupted by the switching element 15 at a frequency sufficiently higher than the power supply frequency (for example, 20 kHz of several Hz or more), the switching element 15
As shown in FIG. 2B, a current having an amplitude (peak) corresponding to the amplitude of the voltage waveform intermittently flows through the device. As a result, the waveform of the current flowing through the power supply terminals 1 and 2 becomes an approximate sine wave corresponding to the voltage waveform as shown in FIG.

By the way, it is desirable that the duty of the control pulse for intermittently controlling the switching element 15 is small when the amplitude of the sine wave is large, and is large when the amplitude is small in order to bring the current waveform close to the sine wave. Also,
The switching element 15 is preferably used not only for improving the current waveform but also for controlling the output voltage in order to simplify the circuit configuration. In order to achieve these, the current detection waveform is input to the comparator 25 and the composite wave of the triangular wave and the differential output is input.

Since the reactor 13 is provided, the current flowing through the switching element 15 increases with time during the ON period of the switching element 15 as shown in FIG. 2B. During the off period of the switching element 15, the energy stored in the reactor 13 passes through the diode 14 and the capacitor 16a.
Given to. At this time, since the capacitor 16a is charged with the sum of the voltage of the reactor 13 and the power supply voltage,
The charging voltage of the capacitor 16a becomes higher than the power supply voltage. The DC voltage shown in FIG. 2D obtained between the output terminals 9 and 10 is compared with the DC reference voltage of the reference voltage source 23, and the differential output voltage corresponding to the difference is as shown in FIG. can get. As shown in FIG. 2 (F), a triangular wave (sawtooth wave) having a downward slope is obtained from the triangular wave generating circuit 26 at a high frequency (for example, 20 kHz). Figure 2 (F)
The triangular wave of is combined with the differential output of FIG.
The combined wave shown by the solid line in (H) is input to the comparator 25. In the comparator 25, the current detection waveform of FIG. 2B (the waveform shown by the dotted line in FIG. 2H) and the waveform of FIG.
The sawtooth wave shown by the solid line in (H) is compared, and when the current detection wave reaches the composite wave, the output of the comparator 25 is converted and the output line of the reset signal forming circuit 33 is shown in FIG.
The reset trigger pulse shown in (I) is obtained. From the set signal generation circuit 32, a set trigger pulse is generated in synchronization with the rising edge of the triangular wave as shown in FIG.
As a result, the control pulse shown in FIG. 2 (J) is generated from the flip-flop 31, and the switching element 15 is turned on / off correspondingly. Since the current detection waveform of the switching element 15 whose peak value changes with respect to the amplitude of the sine wave voltage is input to the comparator 25, the duty of the control pulse of the switching element 15 becomes small during the period when the amplitude of the AC voltage is large, Conversely, when the amplitude of the AC voltage is small, the duty of the control pulse becomes large. Further, the duty of the control pulse changes in inverse proportion to the output voltage.

[0013]

In the apparatus of FIG. 1,
When the amplitude level of the input AC voltage is low, an input current approximate to a sine wave can be passed as shown by the solid line in FIG. However, when the input AC voltage becomes high, the ON time width of the switching element becomes narrow because the output voltage is controlled to be constant. However, the ON time width of the switching element cannot be sufficiently narrowed at the maximum value of the amplitude of the AC voltage and in the vicinity thereof due to control delay or the like.
As shown by the dotted line in (C), an input current having a large number of harmonic components (particularly, third-order, fifth-order, and other odd-numbered harmonics) flows.

The above-mentioned problems are caused by the triangular wave generating circuit 26.
When the circuit of FIG. 1 is modified so that the output of the above is combined with the voltage of the current detection resistor 16 and input to the comparator 25,
Alternatively, this also occurs when the circuit of FIG. 1 is modified so that the output of the error amplifier 22 controls the triangular wave generation circuit 26.

An object of the present invention is to provide a DC power supply device which can improve the input current waveform satisfactorily and at low cost even when the input AC voltage is high.

[0016]

The present invention for achieving the above object provides an AC power supply terminal to which a sinusoidal AC voltage is supplied, a rectifying circuit connected to the AC power supply terminal, and the AC power supply terminal. In series with an AC power supply line between the rectifier circuit and the DC output line of the rectifier circuit
Alternatively, an inductance circuit element connected in parallel and arranged on the output side of the rectifier circuit, and turned on / off with a cycle shorter than the cycle of the AC voltage of the AC power supply terminal, and the inductance circuit element. A switching element for controlling the storage and release of energy with respect to, a smoothing capacitor provided on the output side of the switching element, a voltage detection circuit for detecting a DC output voltage smoothed by the smoothing capacitor, and the switching A current detector for detecting a current flowing through the element or the reactor, a reference voltage source, and a difference forming a voltage corresponding to a difference between the reference voltage of the reference voltage source and the detection voltage obtained from the voltage detection circuit. A signal forming circuit and a triangular wave generating circuit for generating a triangular wave at a frequency sufficiently higher than the AC voltage of the AC power supply terminal, A combination circuit that forms a combined voltage of the output voltage of the differential signal forming circuit and the triangular wave, and a voltage that generates a voltage comparison output of the current detection waveform obtained from the current detector and the combined voltage obtained from the combination circuit. A comparator and a control pulse for switching the switching element from an off state to an on state in synchronization with the triangular wave and for switching the switching element from an on state to an off state in synchronization with the output of the voltage comparator; In a direct-current power supply device including a control pulse forming circuit for supplying to a switching element, an alternating-current voltage amplitude information detecting means for obtaining a voltage including amplitude information of the alternating-current voltage, and the amplitude of the alternating-current voltage exceeds a predetermined value Sometimes for controlling the voltage level of the composite voltage to limit the amplitude of the input current flowing through the AC power supply terminal Those related to the direct current power supply apparatus characterized by a connected voltage-current nonlinearity element is provided between said combining circuit and the AC voltage amplitude information detecting means. The inductance circuit element is, for example, a reactor or a transformer. The difference signal forming circuit is, for example, the differential amplifier (error amplifier) 22 of the embodiment. As described in claim 2, comparing the combined value of the triangular wave and the current detection waveform with the differential output,
The control pulse can be controlled. Further, as described in claim 3, the inclination of the triangular wave can be controlled by the output of the difference signal.

[0017]

In any of the first, second, and third aspects of the invention, when the amplitude of the input AC voltage becomes higher than a predetermined value, the current of the voltage-current nonlinear element increases, and the input current waveform The control is such that the maximum value of the amplitude and the level in the vicinity thereof are lowered. That is, the comparator input is corrected based on the instantaneous value of the AC voltage. As a result, the increase of the harmonic component of the input current (in particular, the odd harmonic component of the third order, the fifth order, etc.) is suppressed.

[0018]

[First Embodiment] Next, a DC power supply device according to a first embodiment of the present invention will be described with reference to FIGS. However, FIG.
In FIG. 1, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The DC power supply device of FIG. 3 is the same as the device of FIG. 1, except that an AC voltage amplitude information detection circuit 60, a zener diode 61 as a voltage / current nonlinear element, a reverse current blocking diode 62, and a resistor 63 are provided. It has a circuit configuration in which a diode 64 for obtaining the control voltage Vcc and a capacitor 65 are added, and is otherwise configured the same as in FIG.

The AC voltage amplitude information detection circuit 60 includes a secondary winding 66 of the reactor 13, a small capacity capacitor 68 connected in parallel to the secondary winding 66 via a rectifying diode 67, and a voltage dividing resistor. It consists of 69 and 71. Since one end of the capacitor 68 is connected to the ground line 12 and the other end thereof is connected to the ground line 12 via the voltage dividing resistors 69 and 70, the capacitor 68 is connected to the detection line 71 connected between the voltage dividing resistors 69 and 70. A detection voltage corresponding to the voltage of the capacitor 68 is obtained.

A series circuit of a Zener diode 61, a backflow prevention diode 62 and a resistor 63 is connected between the detection line 61 and the output terminal of the synthesizing circuit 29. In addition,
The Zener diode 61 has a directionality with respect to the Zener voltage that conducts when the input AC voltage becomes higher than a predetermined value.

[0022]

[Operation] When the amplitude of the sine wave AC voltage between the AC power supply terminals 1 and 2 in the circuit of FIG. 3 is relatively low, the Zener diode 61 is kept off, so that the circuit operates in the same manner as the circuit of FIG. The states of points A to J of 3 are A to J of the circuit of FIG.
Similar to the point, it changes as shown in (A) to (J) of FIG.
The input current has an approximate sine wave as shown by the solid line in FIG. 2 (C), and the power factor is almost 1.

In the circuit of FIG. 3, when the amplitude of the input AC voltage and the output voltage of the rectifying circuit 8 shown in FIG. 4 (A) become higher than a predetermined value, the Zener diode 61 becomes conductive and the line 72 on the cathode side is turned on. The electric potential changes as shown in FIG. That is, a voltage corresponding to the output voltage of the rectifier circuit 8 is obtained at the secondary winding 66 of the reactor 13, and this voltage is applied to the capacitor 68. The capacitor 68 is a high frequency filter for returning a waveform intermittently turned on / off by the switching element 15 to a sine wave. As a result, the voltage corresponding to FIG. 4A is obtained at the capacitor 68. The voltage of the capacitor 68 is divided by the resistors 69 and 70 and sent to the line 71. The potential of the line 71 is negative with respect to the ground line 12, and changes with a sine wave. When a voltage equal to or higher than a predetermined zener voltage is applied to the zener diode 61 at or near the maximum amplitude of the AC voltage, the zener diode 61 becomes conductive and the potential of the line 72 is changed to that shown in FIG.
As shown in FIG. 4B, the output voltage of the synthesis circuit 29, that is, the input voltage of the lower input terminal of the comparator 25 becomes negative as shown in FIG.
As shown in (C), the maximum value of the sine wave, that is, 90 degrees, and the vicinity thereof are low. As a result, the on-time width of the switching element 15 becomes narrow, and the waveform of the current flowing through the input terminal 1 becomes a waveform with the maximum amplitude limited, that is, a waveform with a low harmonic component, as shown in FIG.

[0024]

[Second Embodiment] Next, a DC power supply device according to a second embodiment will be described with reference to FIGS. However, FIG. 5 and FIG.
7 to 13 to be described later, the same reference numerals are given to the substantially same parts as those in FIGS. 1 to 3, and the description thereof will be omitted.

In the circuit of FIG. 5, in order to combine the triangular wave having the upper right slope of FIG. 6 (F) obtained from the triangular wave generation circuit 26 and the current detection waveform of FIG. 6 (B) obtained from the current detection resistor 16, A combining circuit 29 including resistors 27 and 28a is provided, and a resistor 6 is provided between the output terminal and the line 71.
3, a diode 62, and a zener diode 61 are connected in series, and the output line of the combining circuit 29 is connected to the comparator 25. Similar to FIG. 2, when the input AC voltage is relatively low, a waveform as shown in principle in FIG. 6 (H) is obtained from the combining circuit 29, and this waveform and the differential output in FIG. 6 (G) are compared. 25 compared, FIG. 6 (H)
6 reaches the level of the differential output, the output of the comparator 25 is changed, and the reset signal forming circuit 33 generates the reset pulse of FIG. 6 (I). Therefore, the same effect as that of the first embodiment can be obtained. When the input AC voltage is high, the Zener diode 61 as in FIG.
The conduction of the input current causes the operation of limiting the amplitude of the input current. The second embodiment is more resistant to noise than the first embodiment.

[0026]

[Third Embodiment] In the embodiment shown in FIGS. 7 and 8, the comparator 25 includes a current detection line 24 and a triangular wave generating circuit 2.
6 and the output terminal of the differential amplifier 22 is connected to the inclination control terminal of the triangular wave generation circuit 26. The triangular wave generation circuit 26 outputs a triangular wave having a slope opposite to the current detection waveform shown in FIG. 8B as shown in FIG. 8F. The output lines of the triangular wave generation circuit 26 are resistors 27, 6
It is connected to a synthesizing circuit 29 composed of 3 and the triangular wave and the correction signal are synthesized and become the input of the comparator 25. The resistor 26 is connected to the line 71 via the diode 62 and the Zener diode 61. As a result, when the Zener diode 61 is off, the output of the comparator 25 changes according to the same principle as in FIG. 3, and at the intersection of the triangular wave shown by the solid line in FIG. 8F and the current detection waveform shown by the dotted line in FIG. 8H.
The reset pulse shown in FIG. 8 is generated, and the control pulse shown in FIG.

The duty control based on the change in the output voltage is achieved by controlling the inclination of the triangular wave. If the output voltage rises due to a light load after time t1 in FIG. 8, the slope of the triangular wave becomes gentle, the width of the control pulse shown in FIG. 8 (I) becomes narrow, and the output voltage returns to the reference value. Be done. Further, when the input AC voltage becomes higher than that in FIG. 8, the Zener diode 61 is turned on, and the same operation as in FIG. 4 is performed.
Also in the third embodiment, the same operational effect as in the first embodiment can be obtained.

[0028]

MODIFICATION The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible. (1) As shown in FIG. 9, the reactor 13 may be connected to the AC input line of the rectifier circuit 8. (2) As shown in FIG. 10, a transformer primary winding 13a and a secondary winding 13b are provided in place of the reactor 13, and a switching element 15 is connected in series to the primary winding 13a to accumulate in the transformer. Secondary winding 13
It may be configured to emit at b. (3) As shown in FIG. 11, the switching element 15 is connected in series to the line 11, and the reactor 13 is connected to the line 1.
You may connect between 1 and 12. (4) As shown in FIG. 12, the transformer primary winding 13a as an inductance element and the secondary winding 13b may be insulated and separated. (5) As shown in FIG. 13, in addition to the diode 14, a smoothing circuit including a diode 51 and a reactor 52 may be provided at the output stage of the secondary winding 13b as an inductance element. The voltage conversion circuit using the switching element 15 can be further modified in various ways. (6) When the output voltage is low, the voltage detection line 20 may be directly connected to the output terminal 9 by omitting the voltage dividing circuit of the resistors 17 and 18. (7) Apply the voltage applied to the detection line 71 to the reactor 13
May be obtained by dividing the output of the rectifier circuit 8 or the like, instead of detecting using That is, any method may be used as long as the instantaneous value of the AC voltage can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a conventional DC power supply device.

FIG. 2 is a waveform diagram showing states of points A to J in FIG.

FIG. 3 is a circuit diagram showing a DC power supply device according to a first embodiment.

FIG. 4 is a waveform diagram showing a state of each part when the AC voltage of the circuit of FIG. 3 is high.

FIG. 5 is a circuit diagram showing a DC power supply device of a second embodiment.

FIG. 6 is a waveform diagram showing states at points A to J in FIG. 5 when the AC voltage is low.

FIG. 7 is a circuit diagram showing a DC power supply device according to a third embodiment.

8 is a waveform diagram showing states of points A to I in FIG. 7 when the AC voltage is low.

FIG. 9 is a circuit diagram showing a part of a DC power supply device of a modified example.

FIG. 10 is a circuit diagram showing a part of a DC power supply device of another modification.

FIG. 11 is a circuit diagram showing a part of a DC power supply device of still another modification.

FIG. 12 is a circuit diagram showing a part of a DC power supply device of still another modification.

FIG. 13 is a circuit diagram showing a part of a DC power supply device of still another modification.

[Explanation of symbols]

 15 Switching element 25 Comparator 61 Zener diode

Claims (3)

[Claims] 1. An AC power supply terminal to which a sinusoidal AC voltage is supplied, a rectifier circuit connected to the AC power supply terminal, and an AC power supply line between the AC power supply terminal and the rectifier circuit in series or An inductance circuit element connected in series and / or in parallel to a DC output line of the rectifier circuit, and arranged on the output side of the rectifier circuit, and having a cycle shorter than the cycle of the AC voltage of the AC power supply terminal. Switching element that is turned on and off to control energy storage and release with respect to the inductance circuit element, a smoothing capacitor provided on the output side of the switching element, and a DC output smoothed by the smoothing capacitor. A voltage detection circuit for detecting a voltage, a current detector for detecting a current flowing through the switching element or the reactor, A voltage source, a difference signal forming circuit that forms a voltage corresponding to the difference between the reference voltage of the reference voltage source and the detection voltage obtained from the voltage detection circuit, and a frequency sufficiently higher than the AC voltage of the AC power supply terminal. A triangular wave generating circuit for generating a triangular wave at, a combining circuit for forming a combined voltage of the output voltage of the difference signal forming circuit and the triangular wave, a current detection waveform obtained from the current detector, and a combining obtained from the combining circuit. A voltage comparator that generates a voltage comparison output with a voltage, and switches the switching element from an off state to an on state in synchronization with the triangular wave, and switches the switching element from an on state to an off state in synchronization with the output of the voltage comparator. In a DC power supply device comprising a control pulse forming circuit for forming a control pulse for converting to AC voltage amplitude information detection means for obtaining a voltage including amplitude information of the AC voltage, and to limit the amplitude of the input current flowing through the AC power supply terminal when the amplitude of the AC voltage becomes a predetermined value or more. A DC power supply device comprising: a voltage-current non-linear element connected between the AC voltage amplitude information detection means and the synthesizing circuit for controlling the voltage level of the synthesized voltage. 2. An AC power supply terminal to which a sinusoidal AC voltage is supplied, a rectifier circuit connected to the AC power supply terminal, and an AC power supply line between the AC power supply terminal and the rectifier circuit in series or An inductance circuit element connected in series and / or in parallel to a DC output line of the rectifier circuit, and arranged on the output side of the rectifier circuit, and having a cycle shorter than the cycle of the AC voltage of the AC power supply terminal. Switching element that is turned on and off to control energy storage and release with respect to the inductance circuit element, a smoothing capacitor provided on the output side of the switching element, and a DC output smoothed by the smoothing capacitor. A voltage detection circuit for detecting a voltage, a current detector for detecting a current flowing through the switching element or the reactor, A voltage source, a difference signal forming circuit that forms a voltage corresponding to the difference between the reference voltage of the reference voltage source and the detection voltage obtained from the voltage detection circuit, and a frequency sufficiently higher than the AC voltage of the AC power supply terminal. A triangular wave generating circuit that generates a triangular wave at, a combining circuit that forms a combined voltage of the current detection waveform obtained from the current detector and the triangular wave, and a difference signal obtained from the difference signal forming circuit and the combining circuit A voltage comparator for generating a voltage comparison output with the combined voltage, and switching the switching element from the off state to the on state in synchronization with the triangular wave, and switching the switching element from the on state in synchronization with the output of the voltage comparator. A DC power supply device having a control pulse forming circuit for forming a control pulse for switching to an OFF state and giving the control pulse to the switching element. An AC voltage amplitude information detecting means for obtaining a voltage including amplitude information of the AC voltage; and limiting an amplitude of an input current flowing through the AC power supply terminal when the amplitude of the AC voltage becomes a predetermined value or more. A DC power supply characterized in that a voltage-current non-linear element connected between the AC voltage amplitude information detection means and the synthesizing circuit is provided to control the voltage level of the synthesized voltage. apparatus. 3. An AC power supply terminal to which a sinusoidal AC voltage is supplied, a rectifier circuit connected to the AC power supply terminal, and an AC power supply line between the AC power supply terminal and the rectifier circuit in series or An inductance circuit element connected in series and / or in parallel to a DC output line of the rectifier circuit, and arranged on the output side of the rectifier circuit, and having a cycle shorter than the cycle of the AC voltage of the AC power supply terminal. Switching element that is turned on and off to control energy storage and release with respect to the inductance circuit element, a smoothing capacitor provided on the output side of the switching element, and a DC output smoothed by the smoothing capacitor. A voltage detection circuit for detecting a voltage, a current detector for detecting a current flowing through the switching element or the reactor, A voltage source, a difference signal forming circuit that forms a voltage corresponding to the difference between the reference voltage of the reference voltage source and the detection voltage obtained from the voltage detection circuit, and a frequency sufficiently higher than the AC voltage of the AC power supply terminal. A triangular wave generating circuit that is formed so that the slope of the triangular wave changes in response to the output of the difference signal forming circuit, and the triangular wave and the current obtained from the triangular wave generating circuit. A voltage comparator that generates a voltage comparison output with a current detection waveform obtained from a detector, and switches the switching element from an off state to an on state in synchronization with the triangular wave, and synchronizes with the output of the voltage comparator. The switching element is switched from the off state to the on state, and the switching element is switched from the on state to the off state in synchronization with the output of the voltage comparator. In a DC power supply device comprising a control pulse forming circuit for forming a control pulse to be exchanged and giving it to the switching element, an AC voltage amplitude information detecting unit for obtaining a voltage including amplitude information of the AC voltage, and the AC voltage. For controlling the voltage level of the output of the difference signal forming circuit or the output of the triangular wave generating circuit so as to limit the amplitude of the input current flowing through the AC power supply terminal when the amplitude of the above becomes equal to or more than a predetermined value. A DC power supply, characterized in that a voltage-current non-linear element connected between the AC voltage amplitude information detection means and the output line of the difference signal forming circuit or the output line of the triangular wave generating circuit is provided. apparatus.