JPH0880049A - Dc power supply device - Google Patents

Abstract

PURPOSE: To improve the power factor of a DC power supply device. CONSTITUTION: In the DC power supply device, a capacitor 5 discharges electricity for a period when an FET 1 is brought to an on state, and an output current IOUT1 . is made to flow through load 10 through a DC feeder circuit 8 from a rectifier circuit 7 for a period when the FET 1 is brought to an off state. When the rectified voltage VR of the rectifier circuit 7 exceeds the voltage VC1 of the capacitor 5, a charging current IC1 is made to flow through the capacitor 5 from the rectifier circuit 7. Since an input current IIN1 from an AC power supply 20 is represented by the sum of the output current IOUT1 to the load 10 of the rectifier circuit 7 and the charging current IC1 to the capacitor 5, a quiescent section is shortened and a peak value is formed in a low waveform in the input current IIN1 from the AC power supply 20, thus extremely improving the power factor.

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 more particularly to a direct current power supply device for improving a power factor and generating a stable direct current output.

[0002]

2. Description of the Related Art For example, as shown in FIG.
A capacitor input type in which a capacitor 5 is connected between the positive side terminal 71 and the negative side terminal 72 of the rectifier circuit 7 connected to the rectifier circuit 7, the rectified voltage of the rectifier circuit 7 is smoothed by the capacitor 5, and DC power is supplied to the load 10. A DC power supply device including a rectifying / smoothing circuit has been widely used.

[0003]

By the way, in the conventional DC power supply device, although the extreme fluctuation of the DC voltage to the load 10 can be suppressed, there is a drawback that the power factor is extremely low. That is,
Since the rectified voltage of the rectifier circuit 7 is lower than the voltage of the capacitor 5 while the capacitor 5 is discharging, the charging current from the rectifier circuit 7 to the capacitor 5 does not flow and the rectifier circuit 7 loads the load 10
No current flows to. On the other hand, while the capacitor 5 is being charged,
A charging current flows from the rectifier circuit 7 to the capacitor 5, and a current flows from the rectifier circuit 7 to the load 10. Therefore, the input current from the AC power supply 20 flows only in the section where the charging current is flowing from the rectifying circuit 7 to the capacitor 5. Therefore, the waveform of the input current from the AC power source 20 has a long rest period and a high peak value, so that the power factor was extremely low.

Therefore, an object of the present invention is to provide a DC power supply device capable of improving the power factor and supplying a stable DC output to a load.

[0005]

A DC power supply device according to the present invention is connected between an AC power supply and a rectifying circuit, and is connected between a positive side terminal and a negative side terminal of the rectifying circuit and is connected to both ends of a load. It is equipped with a capacitor. In this DC power supply device, a DC supply circuit that directly connects the rectifier circuit and the load, a rectifying element connected between the rectifier circuit and the capacitor, and a rectifier element connected between the capacitor and the load. A switching element that is turned on when a potential difference between the DC supply circuit and the capacitor reaches a predetermined level, and supplies power from the capacitor to the load when the switching element is on. Electric power is supplied from the DC supply circuit to the load when the switching element is in the OFF state. A charging current control means may be connected in series with the rectifying element.

Further, in another DC power supply device according to the present invention, a DC supply circuit for directly connecting the rectifier circuit and the load, a rectifying element connected between the rectifier circuit and the capacitor, and the capacitor And a load connected between the load and the load, the level detecting means generating an output when the voltage of the AC power supply reaches a predetermined level, and a switching element that is turned on by the output of the level detecting means, Power is supplied from the capacitor to the load when the switching element is in the on state, and power is supplied from the DC supply circuit to the load when the switching element is in the off state. A charging current control means may be connected in series with the rectifying element.

[0007]

When the rectified voltage of the rectifier circuit exceeds the voltage of the capacitor and the switching element is in the off state, the capacitor connected to the rectifier circuit is charged. When the potential difference between the DC supply circuit that directly supplies the DC output of the rectifier circuit to the load and the capacitor reaches a predetermined level, the switching element is turned on and the charge accumulated in the capacitor is discharged to the load. When the potential difference between the DC supply circuit and the capacitor falls below a predetermined level, the switching element is turned off, the capacitor stops discharging to the load, and a current flows from the rectifier circuit to the load via the DC supply circuit. Since the input current from the AC power supply is the sum of the output current to the load of the rectifier circuit and the charging current to the capacitor, the input current from the AC power supply has a shorter rest period and the power factor is improved.

Further, when the charging current control means is provided,
Since the charging current from the rectifier circuit to the capacitor is limited and the peak value of the charging current is reduced, it is possible to further improve the power factor. In another embodiment of the present invention, the switching element is turned on / off based on the voltage of the AC power supply, and power is supplied to the load.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a DC power supply device according to the present invention will be described below with reference to FIGS. 1 to 5, the same parts as those shown in FIG. 8 are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 1, in the DC power supply device of the present embodiment, a DC supply circuit 8 for directly supplying the DC output of the rectifier circuit 7 to the load 10 is formed in the circuit of FIG. A reverse current blocking diode 6 is connected between them as a rectifying element. Further, an FET (field effect transistor) 1 is connected as a switching element between the capacitor 5 and the load 10, and a Zener diode 4 is provided as a gate control circuit between the gate of the FET 1 and the capacitor 5.
And a reverse current blocking diode 12 connected in series with FET1.
Connect.

Next, the operation of the DC power supply device of FIG. 1 will be described with reference to the time chart of FIG. 6 (a) is a rectified voltage V _R of the rectifier circuit 7, the rectified voltage V _R is 6
When the voltage V _C1 of the capacitor 5 in (b) is exceeded, the backflow prevention diode 6 is turned on, and the charging of the capacitor 5 is started. This charging continues until the rectified voltage V _R reaches the peak voltage of the half-sine wave, and the charging current I _C1 shown in FIG. 6 (f) flows. After that, the rectified voltage V _R drops along the half-sine wave, and when the difference between the rectified voltage V _R and the voltage V _{C1 of the} capacitor 5 reaches a predetermined level, the Zener diode 4 is turned on and the FET 1 is also turned on. Becomes That is, when the threshold voltage of the FET1 including a voltage set by the zener diode 4 and V _TH, lower than the rectified voltage V _R the voltage V _C1 -V _{T H} shown in FIG. 6 (c), is V _C1 -V _R Since it exceeds V _TH , FET1 is turned on. As a result, the capacitor 5 starts discharging and the electric charge accumulated in the capacitor 5 is discharged to the load 10. At this time, as shown in FIG. 6D, V _C1 −V _TH appears in the output voltage V _OUT1 . Since the rectified voltage V _R of the rectifier circuit 7 is lower than the voltage V _{C1 of the} capacitor 5, no current is supplied from the rectifier circuit 7 to the load 10 via the DC supply circuit 8. When the charge accumulated in the capacitor 5 is discharged and the difference between the rectified voltage V _R and the voltage V _{C1 of the} capacitor 5 falls below a predetermined level, that is, the rectified voltage V _R of the rectifier circuit 7 becomes V _C1 −V _TH . When the voltage exceeds V _C1 −V _R below V _TH , the Zener diode 4 is turned off,
The FET 1 is also turned off, and the capacitor 5 stops discharging the load 10. Therefore, after this, the output voltage V _OUT1
Appeared rectified voltage V _R of the rectifier circuit 7 is directly in, FIG. 6
As shown in (e), a current I _OUT1 flows from the rectifier circuit 7 to the load 10 via the DC supply circuit 8. This current flows rectified voltage V _R of the rectifier circuit 7 continues to V _C1 -V _TH until below FET1 is turned on. Furthermore, the rectifier circuit 7
When the rectified voltage V _R of V exceeds the voltage V _{C1 of the} capacitor 5,
The backflow prevention diode 6 is turned on, and the charging of the capacitor 5 is restarted. Since the input current I _IN1 from the AC power supply 20 is the sum of the current I _OUT1 supplied from the rectifier circuit 7 to the load 10 via the DC supply circuit 8 and the charging current I _C1 to the capacitor 5, As shown in FIG. 6 (g), the input current I _IN1 has a current waveform with a short rest period and a low peak value, and the power factor is improved.

FIG. 2 shows a second embodiment of the DC power supply device according to the present invention. In the circuit of FIG. 2, a thyristor 2 is connected instead of the FET 1 and the reverse current blocking diode 12 of the circuit of FIG. 1, a zener diode 4 is connected between the gate of the thyristor 2 and the capacitor 5, and a charging current control means is provided. 21 is connected in series with the reverse current blocking diode 6. The reactor 21 may be replaced with a resistor or a constant voltage circuit. Other configurations are similar to those of the circuit of FIG. Next, the operation of the DC power supply device of FIG. 2 will be described based on the time chart of FIG. When the voltage of the capacitor 5 shown in FIG. 7B is V _C2 and the breakover voltage of the thyristor 2 including the voltage set by the Zener diode 4 is V _B , the rectified voltage of the rectifier circuit 7 shown in FIG. When V _R falls below V _C2 −V _B shown in FIG. 7C, V _C2 −V _R becomes V
_The Zener diode 4 is turned on beyond _B and a gate signal is given to the thyristor 2. Therefore, the thyristor 2 is turned on and the capacitor 5 starts discharging. At this time, as shown in FIG. 7D, the voltage V _C2 of the capacitor 5 appears as it is in the output voltage V _OUT2, and the rectified voltage V _R of the rectifier circuit 7 is lower than the voltage V _{C2 of the} capacitor 5, so that the rectification is performed. No current is supplied from the circuit 7 to the load 10. When the rectified voltage V _R of the rectifier circuit 7 approaches the voltage V _{C2 of the} capacitor 5 and the current flowing through the thyristor 2 becomes less than the holding current of the thyristor 2, the thyristor 2 is turned off and the discharge of the capacitor 5 is interrupted. Rectifier circuit 7
When the rectified voltage V _R of V exceeds the voltage V _{C2 of the} capacitor 5,
The reverse current blocking diode 6 is turned on, charging of the capacitor 5 is started, and the charging current I _C2 flows from the rectifier circuit 7 to the capacitor 5 as shown in FIG. This time,
The output voltage V _OUT2 appears rectified voltage V _R of the rectifier circuit 7 as it is, the current I _OUT2 to the load 10 from the rectifying circuit 7 via the DC supply circuit 8 as shown in FIG. 7 (e) flows. This current continues to flow until the rectified voltage V _R of the rectifier circuit 7 becomes lower than V _C2- V _B and the thyristor 2 is turned on.
When the rectified voltage V _R of the rectifying circuit 7 becomes lower than the voltage V _{C2 of the} capacitor 5, the reverse current blocking diode 6 is turned off,
Charging of the capacitor 5 is completed. In the embodiment shown in FIG. 2, as in the case of FIG. 1, the input current I _IN from the AC power supply 20 is also changed.
_For No. 2, the current waveform has a short rest period and a low peak value, as shown in FIG. 7 (g), and the power factor is very good. In the embodiment shown in FIG. 2, the rectifier circuit 7 is formed by the reactor 21.
Fig. 7 (g) shows the peak value of the charging current from the capacitor to the capacitor 5.
As shown in FIG. 6, the power factor improving effect is large compared to the case of the embodiment of FIG. 1 (FIG. 6 (g)).

In the third embodiment of the present invention shown in FIG. 3, the thyristor 2, the Zener diode 4, the reverse current blocking diode 6 and the reactor 21 shown in FIG. 2 are connected to the negative terminal 72 side of the rectifier circuit 7. Indicates. In the fourth embodiment of the present invention shown in FIG. 4, the negative terminal of the load 10 and the capacitor 5 are
FET1 is connected between the capacitor 5 and the capacitor 5 and the rectifier circuit 7
The reverse current blocking diode 6 is connected in series with the negative side terminal 72 of the. Further, an F gate control circuit is provided between the positive terminal 71 of the rectifier circuit 7 and the negative terminal of the capacitor 5.
The bias resistor 11 of the ET1 and the transistor 3 are connected in series, and the connection point between the resistor 11 and the collector of the transistor 3 is connected to the gate of the FET1. Further, the Zener diode 4 and the resistor 13 are connected in series between the negative terminal 72 of the rectifier circuit 7 and the negative terminal of the capacitor 5,
The connection point between the Zener diode 4 and the resistor 13 is connected to the base of the transistor 3. In this circuit, when the rectified voltage of the rectifier circuit 7 becomes higher than the voltage of the capacitor 5,
The capacitor 5 is charged through the reverse current blocking diode 6 and current is directly supplied from the rectifier circuit 7 to the load 10 through the DC supply circuit 8. At this time, since a current flows through the Zener diode 4 and the resistor 13, the transistor 3 is turned on and the FET 1 is turned off. When the rectified voltage of the rectifier circuit 7 becomes lower than the voltage level charged in the capacitor 5, no current flows through the Zener diode 4 and the resistor 13, so that the transistor 3 is turned off, the FET 1 is turned on, and the charge is stored in the capacitor 5. The generated charge is discharged to the load 10.
In FIG. 5 showing the fifth embodiment of the present invention, a diode 12 is provided between the negative side terminal of the load 10 and the negative side terminal of the capacitor 5.
And FET1 are connected in series. Further, a resistor 11, a light receiving transistor 24, and a resistor 13 are connected in series as a gate control circuit between the positive side terminal 71 of the rectifier circuit 7 and the negative side terminal of the capacitor 5, and the resistor 11 and the light receiving transistor 34 are connected. The connection point with the collector is connected to the gate of FET1. Further, the collector of the transistor 3 is connected to the gate of the FET 1, the base is connected to the connection point between the light receiving transistor 24 and the resistor 13, and the emitter is connected to the negative terminal of the capacitor 5. Further, between each cathode of the input voltage rectifying diodes 35 and 36 connected to both ends of the AC power source 20 and the negative side terminal 72 of the rectifier circuit 7, a Zener diode 31 serving as a level detecting means of the AC power source, a resistor 32 and the light receiving transistor 34 and the light emitting diode 33 forming a photo coupler are connected in series. The Zener diode 31 is turned on when the voltage of the AC power supply 20 exceeds a predetermined level, and turns on the transistor 3 via the photocoupler. Therefore, the FET1 is turned off. When the voltage of the AC power supply 20 drops and the Zener diode 31 is in the OFF state, the photocoupler does not operate and the transistor 3
Turns off. Therefore, the FET 1 is turned on, and the charge accumulated in the capacitor 5 is discharged to the load 10.

[0013]

According to the present invention, a circuit for directly applying a rectified voltage from a rectifier circuit to a load without passing a capacitor and a circuit for applying a rectified voltage from the rectifier circuit to a load via a capacitor are provided, The capacitor is charged while the rectified voltage of the circuit is higher than the capacitor voltage, and the power is supplied to the load.Therefore, it is possible to shorten the pause period of the input current from the AC power supply and improve the power factor. Power can be used effectively. In addition, a stable DC voltage can be applied to the load, and the electronic device can always operate normally.

[Brief description of drawings]

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

FIG. 2 is an electric circuit diagram showing a second embodiment of a DC power supply device according to the present invention.

FIG. 3 is an electric circuit diagram showing a third embodiment of the DC power supply device according to the present invention.

FIG. 4 is an electric circuit diagram showing a fourth embodiment of a DC power supply device according to the present invention.

FIG. 5 is an electric circuit diagram showing a DC power supply device according to a fifth embodiment of the present invention.

6 is a time chart showing the voltage and current of each part of the circuit of FIG.

7 is a time chart showing the voltage and current of each part of the circuit of FIG.

FIG. 8 is an electric circuit diagram showing a conventional DC power supply device.

[Explanation of symbols]

1 ... FET, 2 ... Thyristor, 4 ... Zener diode, 5 ... Capacitor, 6, 12 ... Reverse current blocking diode, 7 ... Rectifier circuit, 8 ... DC supply circuit 10 ... load, 20 ... AC power supply, 21 ...
..Reactor (charging current control means), 71 ... Positive side terminal, 72 ... Negative side terminal

Claims (4)

[Claims] 1. A DC power supply device comprising: a rectifier circuit connected to an AC power supply; and a capacitor connected between a positive terminal and a negative terminal of the rectifier circuit and connected to both ends of a load. A direct current supply circuit that directly connects the rectifier circuit and the load; a rectifying element that is connected between the rectifier circuit and the capacitor; a direct current supply circuit that is connected between the capacitor and the load; A switching element that is turned on when the potential difference between the capacitor and the capacitor reaches a predetermined level, and supplies power from the capacitor to the load when the switching element is on, and the switching element is off. A DC power supply device, which supplies power from the DC supply circuit to the load at the time. 2. The DC power supply device according to claim 1, wherein a charging current control means is connected in series with the rectifying element. 3. A DC power supply device comprising: a rectifier circuit connected to an AC power source; and a capacitor connected between a positive side terminal and a negative side terminal of the rectifier circuit and connected to both ends of a load. A DC supply circuit that directly connects the rectifier circuit and the load, a rectifying element that is connected between the rectifier circuit and the capacitor, and a voltage of the AC power supply that is connected between the capacitor and the load. Is provided with a level detection means for generating an output when the level reaches a predetermined level, and a switching element that is turned on by the output of the level detection means, and when the switching element is in the on state, power is supplied from the capacitor to the load. And a DC power supply device that supplies power to the load from the DC supply circuit when the switching element is in an off state. 4. The DC power supply device according to claim 3, wherein a charging current control means is connected in series with the rectifying element.