JPH0678542A - Power factor improving power supply - Google Patents

Abstract

(57) [Abstract] [Purpose] In a switching type DC stabilized power supply used for various electronic devices, there is no obstacle to other electronic devices and transmission equipment due to inrush current, power factor and harmonic distortion current. An object of the present invention is to provide a power factor improving power supply device capable of widening a conduction angle. [Configuration] A smoothing capacitor after rectification of the AC input power supply 1 is not owned, and a transformer 4 performs a feedforward switching operation by a first switching element 5 and a choke 8 performs a flyback switching operation by a second switching element 17. By alternating them, an alternating current always flows so that the conduction angle is widened and the power factor can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power factor improving power supply device capable of widening the conduction angle of an AC input current.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram of a typical conventional feedforward type power supply device. In FIG. 3, 1 is an AC input power source, 2 is a noise filter, 3 is a rectifier circuit, 4 is a transformer, 5 is a switching element, 6, 7, 11, and 18 are diodes, 8 is a choke, and 9, 12 and 20 are capacitors. Reference numeral 10 is a control circuit, and 19 is a resistor.

The operation of the feedforward type power supply device configured as described above will be described below. The AC input power supply 1 is converted into a DC power supply by the rectifier circuit 3 and the capacitor 20 via the noise filter 2.

By the high frequency switching operation of the switching element 5, the capacitor 20 is attached to the primary winding 4a of the transformer 4.
A rectangular wave of voltage level is applied across the
A rectangular wave output that is stepped down or boosted to a desired voltage is obtained in the next winding 4b, and this rectangular wave output is rectified and smoothed by the diodes 6 and 7, the choke 8 and the capacitor 9 to obtain a DC output.

The control circuit 10 receives a DC output and outputs a control signal for switching the switching element 5 at a high frequency to stabilize the DC output.

By the winding 4c of the transformer 4 and the diode 18, the excitation energy when the switching element 5 is turned on is fed back to the DC input power source of the capacitor 20 when the switching element 5 is turned off. Diode 11 and capacitor 1
2. The resistor 19 is a snubber that prevents a surge voltage from being applied to both ends of the switching element 5 when the switching element 5 is turned off.

The AC input voltage waveform of the conventional power supply device is shown in FIG.
(A), AC input current waveform is shown in FIG.

[0008]

However, in the above conventional configuration, since the capacitor 20 is owned, the AC input current does not flow for the entire period as shown in FIG.
Since only the vicinity of the peak value of the AC input voltage waveform of (a) flows as the charging current to the capacitor 20, the peak value of the AC input current is large, the input power factor is small as 0.6, and the inrush current at the time of inputting is It was large and the input harmonic distortion current was also large, which was a hindrance to other electronic devices and power transmission equipment.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a power factor improving power supply device capable of widening the conduction angle of an AC input current.

[0010]

In order to achieve the above object, a power factor improving power supply device of the present invention comprises a rectifier circuit to which an AC input power source is connected via a noise filter and an input terminal of the rectifier circuit. A series circuit of a capacitor, a resistor and a diode connected thereto, a series circuit of a primary winding of a transformer connected between output terminals of the rectifier circuit and a first switching element for performing a feedforward switching operation,
A rectifying and smoothing circuit composed of a diode, a choke, and a capacitor connected to the secondary winding of the transformer, a series circuit of a diode and a capacitor connected in parallel to the primary winding of the transformer, and a connection of the diode and the capacitor. From the point, one is a series circuit of a winding that is magnetically coupled to the choke connected to the negative terminal of the rectifier circuit and a second switching element that performs a flyback switching operation, and the other is a series circuit of the capacitor, a resistor, and a diode. A diode connected to a connection point of a capacitor and a resistor in the circuit, and an AC input voltage and a DC output voltage which are connected to the first switching element and the second switching element to input a feedforward switching control signal and a flyback switching control. Control circuit that alternately generates signals to stabilize the DC output voltage And it has a consisting of configuration.

[0011]

In the present invention, of the absolute value sine wave voltage obtained by rectifying the AC input voltage of the sine wave, it is divided into a voltage period higher than a certain voltage level V1 and a voltage period lower than a certain voltage level V1. The output of the secondary winding of the transformer is rectified and smoothed by operating the transformer by feedforward switching, and a DC output is obtained. During a voltage period lower than V1, the choke is magnetically coupled by the second switching element.
The secondary winding is operated by flyback switching and the output of the secondary winding of the choke is rectified to obtain a DC output.

The voltage applied to the primary winding of the transformer during the feedforward switching operation is higher than the V1 voltage of the absolute value sine wave voltage, and the voltage applied to the primary winding of the choke during the flyback switching operation is During the feedforward switching operation, when the first switching element is off, the voltage generated by the excitation energy across the primary winding of the transformer is charged in the capacitor and the voltage lower than the V1 voltage of the absolute value sine wave voltage. It is an added value.

By operating in this way, it always operates by feed-forward switching or fly-back switching, and the voltage applied to the primary winding of the transformer or the primary winding of the choke is never zero during both switching operations. An AC input current flows, the conduction angle becomes wider than that of the conventional power supply, the power factor can be improved to 0.9, and the harmonic distortion current can be reduced. Further, the inrush current when the AC input power is turned on is reduced, the commercial frequency ripple voltage of the DC output voltage is also reduced, and the holding time after the AC input power is cut off can be secured.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit of a power factor correction power supply device according to an embodiment of the present invention. 1 in FIG.
Is an AC input power source, 2 is a noise filter, 3 is a rectifier circuit,
4 is a transformer, 5, 17 are first and second switching elements, 6, 7, 11, 13, 16 are diodes, 8 is a choke, 9, 12, 14 are capacitors, 10 is a control circuit,
Reference numeral 15 is a resistance.

The operation of the power factor correction power supply device configured as described above will be described. The AC input power source 1 is turned on and is converted into an absolute value sine wave voltage by the rectifier circuit 3 via the noise filter 2. The control circuit 10 receives an AC input voltage and supplies a signal to the gate of the second switching element 17 from the control circuit 10 when the absolute value sine wave voltage is lower than a certain voltage level V1. A rectangular wave voltage is applied to the flyback switching operation.

The voltage applied to the primary winding 8a is a voltage obtained by rectifying the AC input voltage by a half-wave voltage of the diode 16 and the capacitor 14 and charging the capacitor 12 through the diode 13, and the AC input voltage is full-wave rectified. It becomes the added value with the applied voltage. The voltage appearing on the secondary winding 8b of the choke 8 is rectified and smoothed by the diode 7 and the capacitor 9 to obtain a DC output. The resistor 15 is for limiting the inrush current that charges the capacitor 14 when the AC input power supply 1 is turned on.

When the absolute sine wave voltage exceeds the V1 voltage, a signal is applied from the control circuit 10 to the gate of the first switching element 5 to apply a rectangular wave voltage to the primary winding 4a of the transformer 4 to perform a feedforward switching operation. do.
The voltage applied to the primary winding 4a is the absolute value sine wave voltage in the voltage period higher than V1.

The voltage appearing on the secondary winding 4b of the transformer 4 is rectified and smoothed by the diodes 6 and 7, the secondary winding 8b of the choke 8 and the capacitor 9 to obtain a DC output. During the feedforward switching operation, when the first switching element 5 is off, the voltage generated by the excitation energy across the primary winding 4a of the transformer 4 is charged in the capacitor 12 through the diode 11 and the primary winding of the choke 8 during the flyback switching operation. It is a part of the voltage applied to the line 8a. The noise filter 2 removes high frequency components corresponding to small changes in the AC input current.

In the steady state, as shown in FIG. 2A, the feed-forward switching operation by the first switching element 5 is performed while the absolute value sine wave voltage is higher than V1, and V
During a period lower than one voltage, the control circuit 10 alternately applies signals to the first and second switching elements 5 and 17 so that the flyback switching operation is performed by the second switching element 17 to stabilize the DC output. .

FIG. 2B shows an AC input current waveform in a steady state. Since this control circuit 10 has only a role of stabilizing the DC output voltage, the AC input current is large when the AC input voltage is low, and the AC input current is small when the AC input voltage is high. Compared with the AC input current waveform of the conventional power supply device of (b), the conduction angle is wide and the power factor is greatly improved.

[0021]

As described above, the present invention does not have a smoothing capacitor after rectification of an AC input power source, and a feedforward switching operation by a first switching element for a transformer and a flyback by a second switching element for a choke. By alternating the switching operation, the AC input current always flows, the conduction angle is widened, and the power factor can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power factor correction power supply device according to an embodiment of the present invention.

2A and 2B are waveform diagrams for explaining the operation of the power factor correction power supply device in the same embodiment.

FIG. 3 is a circuit diagram of a conventional typical feedforward type power supply device.

4A and 4B are waveform diagrams for explaining the operation of the power supply device in the conventional example.

[Explanation of symbols]

 1 AC Input Power Supply 2 Noise Filter 3 Rectifier Circuit 4 Transformer 5 First Switching Element 6, 7, 11, 13, 16 Diode 8 Choke 9, 12, 14 Capacitor 10 Control Circuit 15 Resistor 17 Second Switching Element

Claims (1)

[Claims] 1. A rectifier circuit to which an AC input power source is connected via a noise filter, a series circuit of a capacitor, a resistor and a diode connected between the input terminals of the rectifier circuit, and an output terminal of the rectifier circuit. First to perform feedforward switching operation with the primary winding of the connected transformer
, A series circuit of switching elements, a rectifying and smoothing circuit composed of a diode, a choke and a capacitor connected to the secondary winding of the transformer, and a series circuit of a diode and a capacitor connected in parallel to the primary winding of the transformer. And a series circuit of a second switching element for performing flyback switching operation, one of which is a connection point of the diode and the capacitor, the other is a winding which is magnetically coupled to the choke and which is connected to the negative terminal of the rectifier circuit, and the other is a switching circuit. A diode connected to the connection point of the capacitor and the resistor in the series circuit of the capacitor, the resistor, and the diode, and the AC input voltage and the DC output voltage that are connected to the first switching element and the second switching element, and feed forward Alternately generate a switching control signal and a flyback switching control signal. Power factor becomes a flow output voltage from the control circuit for stabilizing improved power supply.