JPH10285923A - Power unit and method for controlling its voltage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly efficient power unit which has a high power factor and is constituted to maintain a stable DC output even when a power failure, such as the momentary voltage breakage, etc., of commercial power supply occurs and a method for controlling the voltage of the power unit. SOLUTION: A power unit is provided with a first converter which generates a DC voltage by rectifying and smoothing the output of a transformer T1 by impressing a pulsating current obtained by rectifying the alternating current of a commercial power source upon the transformer T1 and, at the same time, controls the output of the transformer T1 to a constant voltage based on the value of the DC voltage detected by means of a first voltage detecting circuit 102, and a second converter which supplies its output to a load by boosting the output of the first converter and, at the same time, performs constant- voltage control based on the terminal voltage of the load detected by means of a second voltage detecting circuit 202 and sets the set output voltage value of the second converter to a value lower than that of the voltage supplied to the load through the first and the second converters while the second converter stops the boosting operations.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device and a voltage control method in the power supply device.
The present invention relates to a high power factor power supply for supplying DC power to electronic equipment and a voltage control method in the power supply.

[0002]

2. Description of the Related Art Heretofore, as a DC power supply for electronic equipment, a switching type DC power supply which stabilizes a voltage by switching control has been used. In the switching method, particularly, a method in which a pulsating current obtained by rectifying the input commercial AC is applied to a transformer and applied to the transformer, and the output of the transformer is rectified and smoothed to obtain a DC, has a high power factor with a simple circuit configuration. It can be used for small capacity applications.

FIG. 4 is a circuit diagram showing the configuration of a conventional one-converter high power factor type switching power supply having an output stabilizing circuit. The switching power supply includes input power supply terminals 1 and 2, output terminals 3 and 4, a rectifier stack DM1, a choke coil L1, and capacitors C1 and C.
2, a transistor Q1, a transformer T1, a diode D1, a PWM (Pulse Width Modulation: pulse width modulation) circuit 101, a voltage detection circuit 102, and a photocoupler PHC1.

The input power supply terminals 1 and 2 have one side connected to a commercial AC power supply and the other side connected to an AC terminal of the rectifier stack DM1. Rectifier stack DM1 +
The terminal is connected to one terminal of the capacitor C1 and one terminal of the primary winding N1 of the transformer T1 via the choke coil L1. The negative terminal of the rectifier stack DM1 is connected to the other terminal of the capacitor C1 and the transistor Q1.
Connected to the emitter terminal of The collector terminal of the transistor Q1 is connected to the other terminal of the primary winding N1 of the transformer T1. A drive signal output from the PWM circuit 101 is connected between the base terminal and the emitter terminal of the transistor Q1.

[0005] One terminal of the secondary winding N2 of the transformer T1 is connected to one terminal of a filter capacitor C2 via a rectifying diode D1. One terminal of the capacitor C2 is connected to the output terminal 3. The other terminal of the secondary winding N2 of the transformer T1 is connected to the other terminal of the capacitor C2. The other terminal of the capacitor C2 is connected to the output terminal 4. The output smoothed by the filter including the capacitor C2 is supplied from the output terminals 3 and 4 to a predetermined load.

To detect the output voltage to the load,
A voltage detection circuit 102 is connected in parallel with a load (not shown) connected to the output terminals 3 and 4. Voltage detection circuit 10
2 is a PWM circuit 101 via a photocoupler PHC1.
It is connected to the. The detection value detected by the voltage detection circuit 102 is output to the PWM circuit 1 via the photocoupler PHC1.
01 is returned. The PWM circuit 101 controls a switching duty ratio or a frequency of a drive pulse applied to the base terminal of the transistor Q1 according to a value detected by the voltage detection circuit 102. That is, the transistor Q1 is driven by the output of the PWM circuit 101.

Next, the operation of the circuit shown in FIG. 4 will be described. When a commercial power supply is connected to the input power supply terminals 1 and 2, the commercial power supply current is rectified by the rectifier stack DM1,
A pulsating voltage is applied to the primary winding N1 of the transformer T1 via a noise filter circuit including a choke coil L1 and a capacitor C1, and is intermittently turned on and off by a transistor Q1. Energy is stored in the transformer T1 when the transistor Q1 is turned on, and is output from the secondary winding N2 of the transformer T1 via the diode D1 when the transistor Q1 is turned off. This operation is repeated to output power. The output from the diode D1 is smoothed by a smoothing capacitor C2 and converted into a direct current. The converted DC is supplied from the output terminals 3 and 4 to the load.

[0008]

However, the above-mentioned prior art has the following problems. That is, in the conventional switching power supply device, the switching is performed without smoothing the pulsating current obtained by rectifying the commercial AC input to the input power supply terminal. Significantly improved. But,
When the commercial AC input to the input power supply terminal is lost due to a power supply failure such as instantaneous voltage cutoff, the output voltage fluctuates significantly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is intended to maintain a stable DC output with high efficiency and high power factor even when a power supply failure such as instantaneous voltage cutoff of a commercial power supply occurs. It is an object to provide a power supply device and a voltage control method in the power supply device.

[0010]

In order to achieve the above object, a first aspect of the present invention is a power supply apparatus for stabilizing the voltage of a commercial AC power supply, which applies a rectified pulsating flow of the commercial AC to a transformer. First voltage control means for rectifying and smoothing the output of the transformer to generate a DC voltage, and performing constant voltage control of the output of the transformer based on the detected DC voltage; and boosting the output of the first voltage control means. Operating and supplying an output to the load, and a second voltage control means for performing a constant voltage control based on the detected terminal voltage of the load, and a set output voltage value of the second voltage control means, In a state where the boosting operation of the second voltage control means is stopped, the voltage is set to be lower than the voltage value supplied to the load via the first and second voltage control means.

According to a second aspect of the present invention, the first voltage control means includes a first switch element for switching the pulsating flow, and a first switch element for detecting a voltage value of the DC voltage. And a second voltage control means, the second voltage control means, a second switch element for switching the output of the first voltage control means, and a second voltage detection for detecting the terminal voltage of the load Means.

In order to achieve the above object, a third aspect of the present invention is characterized in that a bypass diode is provided between the input and output of the second constant voltage control means.

According to a fourth aspect of the present invention, there is provided a voltage control method for a power supply apparatus for stabilizing a voltage of a commercial AC power supply, the method comprising applying a rectified pulsating flow of the commercial AC power to the transformer. A first voltage control step of rectifying and smoothing the output to generate a DC voltage, and performing a constant voltage control of the transformer output based on the detected DC voltage, and a step-up operation of the output of the first voltage control step. And performing a constant voltage control based on the detected terminal voltage of the load, and setting a set output voltage value of the second voltage control step to the second voltage control step. In the voltage control step, the voltage is set to be lower than the voltage supplied to the load through the first and second voltage control steps when the boosting operation is stopped.

In order to achieve the above object, the invention according to claim 5 is characterized in that the first voltage control step includes a first switching step for switching the pulsating flow, and a first switching step for detecting a voltage value of the DC voltage. Wherein the second voltage control step comprises: a second switching step of switching an output of the first voltage control step; and a second voltage detection step of detecting a terminal voltage of the load. And a step.

[0015]

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

[1] First Embodiment First, the configuration of a DC power supply according to a first embodiment will be described with reference to FIG. In FIG. 1, the same reference numerals are given to the same or corresponding components as those in the conventional example of FIG. The DC power supply according to the first embodiment includes input power terminals 1 and 2.
, Output terminals 3 and 4, rectifier stack DM1, choke coils L1 and L2, and capacitors C1, C2 and C3.
, Transistors Q1, Q2, transformer T1, diodes D1, D2, first PWM circuit 101, second PWM circuit 201, first voltage detection circuit 102,
The configuration includes a second voltage detection circuit 202 and a photocoupler PHC1.

The DC power supply according to the first embodiment is
A pulsating current obtained by rectifying a commercial AC is intermittently applied by a switch element and applied to a transformer T1, and a first converter (described later) that rectifies and smoothes the output of the transformer T1 to generate a DC voltage.
Between the first converter output and the load, a step-up converter as a voltage compensation circuit is inserted as a second converter (described later), and the second converter output is supplied to the load. The setting output voltage value is set to be lower than the voltage value supplied to the load via the second converter from the first converter in a state where the second converter stops the boosting operation. .

The input power supply terminals 1 and 2 are connected on one side to a commercial AC power supply and connected on the other side to the AC terminals of the rectifier stack DM1. The + terminal of the rectifier stack DM1 is
It is connected to one terminal of a primary winding N1 of a transformer T1 via a noise filter composed of a choke coil L1 and a capacitor C1. The negative terminal of the rectifier stack DM1 is connected to the other terminal of the capacitor C1 and the transistor Q1.
1 is connected to one emitter terminal.

The collector terminal of the transistor Q1 is connected to the other terminal of the primary winding N1 of the transformer T1. A drive signal output from the first PWM circuit 101 is connected between the base terminal and the emitter terminal of the transistor Q1. The above-described values of the choke coil L1 and the capacitor C1 are appropriately determined based on a required leakage noise level to a commercial line and a ripple current flowing through the capacitor C1 due to a switching operation of the transistor Q1.

One terminal of the secondary winding N2 of the transformer T1 is connected to one terminal of a capacitor C2 via a rectifying diode D1. In addition, 2 of the transformer T1
The other terminal of the next winding N2 is connected to the other terminal of the capacitor C2. Both ends of the capacitor C2 become the first converter output and are applied to the second converter in the next stage. The capacity of the capacitor C2 described above is appropriately determined depending on the required holding time and the like.

In order to detect the voltage value of the output of the first converter, the first voltage detection circuit 1 is connected in parallel with the capacitor C2.
02 is connected. The value detected by the first voltage detection circuit 102 is fed back to the first PWM circuit 101 via the photocoupler PHC1. The first PWM circuit 101 controls a switching duty ratio or a frequency of a driving pulse applied to the base terminal of the transistor Q1 according to a detection value of the first voltage detection circuit 102. That is, the transistor Q1 is driven by the output of the first PWM circuit 101. In order to control the terminal voltage of the capacitor C2 to be constant, a constant voltage control circuit including the first voltage detection circuit 102, the first PWM circuit 101, and the like is provided.

The second converter connects the positive side output of the first converter output to one terminal of the choke coil L2, and the other terminal of the choke coil L2 is connected to the collector terminal of the transistor Q2 and the diode D2. Connected to the anode terminal. The cathode terminal of the diode D2 is connected to one terminal of the capacitor C3.

The minus side output of the first converter output is the emitter terminal of the transistor Q2 and the capacitor C
3 is connected to the other terminal. Further, the capacitor C
Output terminals 3 and 4 are connected in parallel with 3. A load (not shown) is connected to the output terminals 3 and 4. In order to detect the terminal voltage of the load, the second voltage detection circuit 202
Are connected in parallel with the load. Second voltage detection circuit 2
The output of 02 is connected to the second PWM circuit 201. The output of the second PWM circuit 201 is a transistor Q
2 between the base terminal and the emitter terminal. To control the load voltage to be constant, a constant voltage control circuit including the second voltage detection circuit 202, the second PWM circuit 201, and the like is provided.

Next, the basic operation of each unit in the DC power supply according to the first embodiment configured as described above will be described. When a commercial power supply is connected to the input power supply terminals 1 and 2, the first converter rectifies the commercial alternating current by the rectifier stack DM1 and outputs the choke coils L1 and L2.
The pulsating voltage is applied to the primary winding N1 of the transformer T1 via the noise filter circuit composed of When the transistor Q1 is turned on, power is stored in the transformer T1, and when the transistor Q1 is turned off, power is transmitted from the secondary winding N2 of the transformer T1 to the capacitor C2 via the diode D1 and stored. This operation is repeated to transmit power. The electric power stored in the capacitor C2 is applied to the second converter in the next stage.

In order to keep the terminal voltage of the capacitor C2 constant, the DC power supply is provided with a constant voltage control circuit. The constant voltage control circuit includes the first voltage detection circuit 102, the first PWM circuit 101, and the like as described above, and stabilizes the voltage by controlling the switching operation of the transistor Q1. First voltage detection circuit 102
Is composed of an operational amplifier, a transistor, and the like, compares the terminal voltage of the capacitor C2 with a reference voltage, and outputs an error voltage to the first PWM circuit 101 via the photocoupler PHC1. The first PWM circuit 101 determines the drive pulse of the transistor Q1 based on the error voltage, and stabilizes the voltage by adjusting the drive pulse width and the duty ratio of the transistor Q1 drive pulse.

When a voltage is applied to the input of the second converter, when the transistor Q2 is turned on, the choke coil L2
And when the transistor Q2 is turned off, the diode D2
To the capacitor C3 and accumulate it. The power stored in the capacitor C3 is supplied to a load (not shown) connected to the output terminals 3, 4.

In order to control the load voltage to be constant, the DC power supply is provided with a constant voltage control circuit. The constant voltage control circuit includes the second voltage detection circuit 202 as described above,
The second PWM circuit 201 includes a second PWM circuit 201 and the like, compares a load voltage with a reference voltage, and outputs an error voltage to the second PWM circuit 20.
Output to 1. The second PWM circuit 201 determines the drive pulse of the transistor Q2 based on the error voltage, outputs a drive pulse, and controls the pulse width and the duty ratio of the drive pulse of the transistor Q2 so that the load voltage becomes constant. The amount of power is adjusted so that the target voltage is stabilized.

Here, the operation of each part of the DC power supply device in the state of commercial AC will be described with reference to FIG. FIG.
(A) is the waveform of the power supply voltage of the commercial power supply, (B) is the waveform of the output voltage when the commercial power supply is cut off in the conventional example, and (C) is the output voltage waveform of the present invention when the commercial power supply is cut off. Hereinafter, a case where the commercial power supply voltage is in a stable state and a case where a voltage fluctuation such as an instantaneous interruption occurs in the commercial power supply voltage will be described separately.

(1) When the commercial power supply voltage is in a stable state When the commercial power supply voltage is in a stable state, the voltage applied to the input of the second converter of the DC power supply is equal to the choke coil L2. The voltage generated in the capacitor C2 via the diode D2 is applied to the load from the output terminals 3 and 4. At this time, the first converter of the DC power supply device is set so that the voltage value of the load voltage is equal to or higher than the detection set value of the second voltage detection circuit 202.

Therefore, since a voltage higher than the target voltage is generated at the output of the second converter, the second voltage detection circuit 202 attempts to reduce the output voltage by using the second PW
It instructs the M circuit 201 to shorten the pulse width. Therefore, the transistor Q2 is almost turned off, the second converter does not operate, and the voltage generated in the capacitor C2 is loaded from the output terminals 3, 4 via the choke coil L2 and the diode D2 in the second converter. (Not shown).

As described above, in a state where the commercial power supply voltage is stable, a loss occurs due to a voltage drop due to the choke coil L2 and the diode D2 in the second converter, but the operation of the second converter is stopped. Thus, power can be supplied to the load while suppressing voltage loss.

(2) When a voltage fluctuation such as an instantaneous interruption occurs in the commercial power supply voltage The commercial power supply voltage is cut off, the voltage generated in the capacitor C2 decreases, and the voltage value of the load voltage is changed to the second voltage detection circuit 20.
2, the second voltage detection circuit 202
Is trying to raise the output voltage, the second PWM circuit 2
In order to instruct 01 to increase the pulse width, transistor Q2 starts a switching operation, and the second converter performs a boosting operation.

By the boosting operation of the second converter, the output voltage can be maintained at a predetermined voltage even if the voltage value decreases as long as the charge of the capacitor C2 remains. That is, the waveform of the output voltage when the commercial power supply is cut off in the conventional example is the waveform shown in FIG. 2B, whereas the waveform of the output voltage when the commercial power supply is cut off in the first embodiment of the present invention is shown in FIG. 2 (C).

As described above, when the commercial power supply voltage is abnormal, the second converter operates to compensate for a decrease in the output voltage, so that the voltage stability is significantly improved as compared with the conventional example. Can be.

As described above, according to the first embodiment, the DC power supply converts the commercial AC into the rectifier stack DM1.
The rectified pulsating current is switched by the transistor Q1 and applied to the transformer T1, the output of the transformer T1 is rectified and smoothed to generate a DC voltage, and the voltage value of the DC voltage is detected by the first voltage detection circuit 102. A first converter for controlling the transistor Q1 to turn on and off to perform constant voltage control of the output of the transformer T1, and an output of the first converter as an input to turn on and off the transistor Q2 to perform a boosting operation. And a second converter that detects the terminal voltage of the load with the second voltage detection circuit 202 and performs constant voltage control, and sets the set output voltage value of the second converter to the second Is set to a voltage lower than the voltage supplied to the load via the first and second converters in a state where the step-up operation is stopped. It is possible to maintain the DC output of a power failure such as instantaneous voltage block is stabilized even if it occurs.

That is, the high-efficiency and high-power factor features of the single-converter high-power-factor power supply that obtains a DC voltage by performing high-frequency switching control of the pulsating current obtained by rectifying the commercial AC with a switch element are not impaired. It is possible to realize a high-performance DC power supply that overcomes the disadvantage of being vulnerable to fluctuations in the input commercial power supply.

In the first embodiment, a bipolar transistor is used as a switch element for performing switching control in a DC power supply device. However, the present invention is not limited to this. A FET (Field Effect Transistor) or a GTO is used.
Other switch elements such as (Gate Turn Off Tyhyristor) may be used.

[2] Second Embodiment First, the configuration of a DC power supply according to a second embodiment will be described with reference to FIG. In FIG. 3, the same or corresponding components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals. The DC power supply according to the second embodiment includes input power supply terminals 1, 2, output terminals 3, 4, a rectifier stack DM1, choke coils L1, L2, capacitors C1, C2, C3, and a transistor Q1. , Q2, a transformer T1, diodes D1, D2, D3 and a first P
A WM circuit 101, a second PWM circuit 201, a first voltage detection circuit 102, a second voltage detection circuit 202,
The configuration includes a photocoupler PHC1.

The difference between the DC power supply according to the second embodiment and the DC power supply according to the first embodiment is that the DC power supply
The point is that a diode D3 for bypass is connected between the terminal and the + terminal of the capacitor C3 which is the output of the second converter. That is, in FIG. 3, the anode terminal of the diode D3 is connected to the + terminal of the capacitor C2, and the cathode terminal of the diode D3 is connected to the + terminal of the capacitor C3. The other configuration is the same as that of the first embodiment shown in FIG. 1, and the description of the connection and function of each unit is omitted.

Next, the operation of the DC power supply according to the second embodiment configured as described above will be described.
The basic operation of this apparatus is the same as that of the first embodiment, and the description is omitted. Here, differences from the first embodiment will be described. Hereinafter, a case where the commercial power supply voltage is in a stable state and a case where a voltage fluctuation such as an instantaneous interruption occurs in the commercial power supply voltage will be described separately.

(1) When the commercial power supply voltage is in a stable state When the commercial power supply voltage is in a stable state, the voltage applied to the input of the second converter of the DC power supply is equal to the choke coil L2. The voltage generated in the capacitor C2 via the diode D2 is applied to the load from the output terminals 3 and 4. At this time, the first converter is set so that the voltage value of the load voltage is equal to or higher than the detection set value of the second voltage detection circuit 202.

Accordingly, since a voltage higher than the target voltage is generated at the output of the second converter, the second voltage detection circuit 202 attempts to lower the output voltage by using the second PW
It instructs the M circuit 201 to shorten the pulse width. Therefore, the transistor Q2 is almost turned off, the second converter does not operate, and the voltage generated at the capacitor C2 is output from the output terminals 3, 4 to the load (not shown) via the diode D3.

As described above, when the commercial power supply voltage is stable, the operation of the second converter is stopped and the diode D3 is connected to the bypass diode, as in the first embodiment. By functioning as, the first converter output is bypassed to the second converter output with a slight voltage drop, so that power can be supplied to the load more efficiently than in the first embodiment.

(2) When a voltage fluctuation such as interruption occurs in the commercial power supply voltage As in the first embodiment, the commercial power supply voltage is interrupted and the voltage generated in the capacitor C2 decreases, and the load voltage decreases. When the voltage value decreases to the set value of the second voltage detection circuit 202, the second voltage detection circuit 202 instructs the second PWM circuit 201 to increase the pulse width to increase the output voltage. Therefore, the transistor Q2 starts the switching operation, and the second converter performs the boosting operation.

By the boosting operation of the second converter, the output voltage can be kept at a predetermined voltage even if the voltage value decreases as long as the charge of the capacitor C2 remains. That is, the waveform of the output voltage when the commercial power supply is cut off in the conventional example is the waveform shown in FIG. 2B, whereas the waveform of the output voltage when the commercial power supply is cut off in the second embodiment of the present invention is shown in FIG. 2 (C).

As described above, when the commercial power supply voltage is abnormal, the second converter operates to compensate for a decrease in the output voltage, so that the voltage stability is significantly improved as compared with the conventional example. Can be. Also, by providing a bypass diode D3 between the input and output of the second converter,
Since the first converter output is bypassed to the second converter output with a small voltage drop, power can be supplied to the load more efficiently.

As described above, according to the second embodiment, the DC power supply converts the commercial AC into the rectifier stack DM1.
The rectified pulsating current is switched by the transistor Q1 and applied to the transformer T1, the output of the transformer T1 is rectified and smoothed to generate a DC voltage, and the voltage value of the DC voltage is detected by the first voltage detection circuit 102. A first converter for controlling the transistor Q1 to turn on and off to perform constant voltage control of the output of the transformer T1, and an output of the first converter as an input to turn on and off the transistor Q2 to perform a boosting operation. And a second converter that detects the terminal voltage of the load with the second voltage detection circuit 202 and performs constant voltage control, and sets the set output voltage value of the second converter to the second Is set to a voltage lower than the voltage supplied to the load via the first and second converters in a state where the step-up operation is stopped. It is possible to maintain the DC output of a power failure such as instantaneous voltage block is stabilized even if it occurs.

That is, the high-efficiency and high-power-factor characteristics of a single-converter high-power-factor power supply that obtains a DC voltage by performing high-frequency switching control of a pulsating current obtained by rectifying a commercial alternating current with a switch element are not impaired. It is possible to realize a high-performance DC power supply that overcomes the disadvantage of being vulnerable to fluctuations in the input commercial power supply.

Since the bypass diode D3 is provided between the input and the output of the second converter, the output of the first converter can be bypassed to the output of the second converter with a slight voltage drop. Thereby, power can be more efficiently supplied to the load.

In the second embodiment, a bipolar transistor is used as a switch element for performing switching control in a DC power supply device. However, the present invention is not limited to this. Another switch element such as an FET or GTO may be used. You may.

[0051]

As described above, according to the first aspect of the present invention, in a power supply device for stabilizing the voltage of a commercial AC power supply, a pulsating current obtained by rectifying a commercial AC power is applied to a transformer, and the output of the transformer is reduced. Rectifying and smoothing to generate a DC voltage, and performing a constant voltage control of the transformer output based on the detected DC voltage, and a step-up operation of the output of the first voltage control means. And a second voltage control means for performing constant voltage control based on the detected terminal voltage of the load, and setting a set output voltage value of the second voltage control means to the second voltage control means. Since the voltage control means is set to a voltage lower than the voltage supplied to the load via the first and second voltage control means in a state in which the boosting operation is stopped, the voltage of the power supply is high efficiency and high power factor and instantaneous voltage cut-off of the commercial power supply. Stable DC output even if a power supply failure occurs It can be maintained. That is, without losing the features of high efficiency and high power factor, which is an advantage of a 1-converter high power factor power supply that obtains a DC voltage by performing high frequency switching control of a pulsating current obtained by rectifying a commercial AC by a switch element.
It is possible to realize a high-performance power supply device overcoming the disadvantage of being vulnerable to fluctuations in the input commercial power supply.

According to the second aspect of the present invention, the first voltage control means includes a first switch element for switching the pulsating flow, and a first voltage detection means for detecting a voltage value of the DC voltage. And the second voltage control means includes a second switch element for switching an output of the first voltage control means, and a second voltage detection means for detecting a terminal voltage of the load. Thus, the same effect as the first aspect of the invention can be obtained.

According to the third aspect of the present invention, since the bypass diode is provided between the input and output of the second constant voltage control means, the same effect as that of the first aspect of the present invention can be obtained. The first converter output can be bypassed to the second converter output with a small voltage drop,
Further, power can be efficiently supplied to the load.

According to a fourth aspect of the present invention, in the voltage control method for a power supply apparatus for stabilizing the voltage of a commercial AC power supply, a pulsating current obtained by rectifying the commercial AC is applied to a transformer to rectify and smooth the output of the transformer. A first voltage control step of performing constant voltage control of the transformer output based on the detected DC voltage, and performing a boosting operation of the output of the first voltage control step to output the load to the load. Supply and
A second voltage control step of performing constant voltage control based on the detected terminal voltage of the load, and setting a set output voltage value of the second voltage control step to a step-up operation stopped state of the second voltage control step. In order to set the voltage lower than the voltage supplied to the load through the first and second voltage control steps, even if a power failure such as instantaneous voltage interruption of the commercial power supply with high efficiency and high power factor occurs A stable DC output can be maintained.

According to the fifth aspect of the present invention, the first voltage control step includes a first switching step of switching the pulsating flow, and a first voltage detection step of detecting a voltage value of the DC voltage. And the second voltage control step includes a second switching step of switching an output of the first voltage control step, and a second voltage detection step of detecting a terminal voltage of the load. Thus, the same effect as that of the fourth aspect is obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a DC power supply according to a first embodiment of the present invention.

FIGS. 2A and 2B are explanatory diagrams showing various waveforms according to the first embodiment of the present invention, wherein FIG. 2A is an explanatory diagram showing a power supply voltage waveform of a commercial power supply, and FIG. FIG. 7C is an explanatory diagram showing a waveform of the output voltage at the time, and FIG. 7C is an explanatory diagram showing a waveform of the output voltage when the commercial power is cut off in the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of a DC power supply device according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a DC power supply device according to a conventional example.

[Explanation of symbols]

 1, 2 input power supply terminal 3, 4 output terminal 101 first PWM circuit 102 first voltage detection circuit 201 second PWM circuit 202 second voltage detection circuit C1, C2, C3 capacitors D1, D2, D3 diode DM1 Rectifier stack L1, L2 Choke coil PHC1 Photocoupler Q1, Q2 Transistor T1 Transformer

Claims (5)

[Claims] 1. A power supply device for stabilizing the voltage of a commercial AC power supply, wherein a pulsating current obtained by rectifying a commercial AC power is applied to a transformer, the output of the transformer is rectified and smoothed, and a DC voltage is generated. A first voltage control unit that performs constant voltage control of the transformer output based on a voltage, and performs a boosting operation of an output of the first voltage control unit to supply an output to a load; Second voltage control means for performing constant voltage control based on the output voltage value of the second voltage control means, the first and the second in the state of step-up operation stop of the second voltage control means A power supply device set to be lower than a voltage value supplied to a load via the voltage control means. 2. The method according to claim 1, wherein the first voltage control means has a first switch element for switching the pulsating flow, and a first voltage detection means for detecting a voltage value of the DC voltage. 2. The voltage control device according to claim 1, further comprising a second switch element for switching an output of the first voltage control device, and a second voltage detection device for detecting a terminal voltage of the load. The power supply as described. 3. The power supply device according to claim 1, wherein a bypass diode is provided between an input and an output of the second constant voltage control means. 4. A voltage control method in a power supply device for stabilizing a voltage of a commercial AC power supply, wherein a pulsating current obtained by rectifying a commercial AC power is applied to a transformer to rectify and smooth the output of the transformer to generate a DC voltage. A first voltage control step of performing constant voltage control of the transformer output based on the detected DC voltage, and performing a boosting operation of the output of the first voltage control step to supply the output to the load, and A second voltage control step of performing a constant voltage control based on the terminal voltage of the second voltage control step, the set output voltage value of the second voltage control step, the step-up operation of the second voltage control step in the stop state of the second voltage control step A voltage control method in a power supply device, wherein the voltage is set to be lower than a voltage value supplied to a load through first and second voltage control steps. 5. The first voltage control step includes: a first switching step of switching the pulsating flow;
A first voltage detection step of detecting a voltage value of the DC voltage, the second voltage control step is a second switching step of switching the output of the first voltage control step, the load 5. The voltage control method according to claim 4, further comprising a second voltage detection step of detecting the terminal voltage of the power supply device.