JPH0591744A - Switching regulator - Google Patents

Abstract

PURPOSE:To improve an input power factor and to reduce a rush current at the time of connecting an input of a power source by providing a diode connected between an input rectifier and an input capacitor for preventing charging of the input capacitor by a rectified voltage from the rectifier. CONSTITUTION:A half-wave rectified tertiary winding voltage appears at the cathode side of a diode 12 of a switching regulator to charge an input capacitor 3 through a reactor 14. Energy charged in the capacitor 3 is supplied at the trough part of a waveform rectified by a main full-wave rectifier 2 from the capacitor 3 to a switching transformer 4 and a switching element 5 through a diode 13 to continue the switching operation thereby holding the output. On the other hand, since the diode 13 prevents the capacitor 3 from being charged by the voltage rectified by the rectifier 2, a peak current does not flow, thereby improving a power factor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator with improved input power factor and inrush current.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing the structure of a conventional switching regulator. In FIG. 4, 1 is an input AC terminal, 2 is a main full-wave rectifier, 3 is an input capacitor, 4 is a switching transformer, 5 is a switching element, and 6 and 7.
Is a high frequency rectifier, 8 is a reactor, 9 is an output capacitor, 10 is an output terminal, and 11 is a drive circuit for driving the control circuit and the switching element 5.

In the switching regulator configured as described above, the switching transformer 4 and the switching element 5 draw a current from the input capacitor 3 as needed. On the other hand, the main full-wave rectifier 2 temporarily supplies the peak current shown in the input current waveform of FIG. 5 to the input capacitor 3 every half cycle near the peak time of each voltage shown in the input voltage waveform of FIG. However, it has a drawback that the input power factor is lowered. Further, since the input capacitor 3 is rapidly charged when the AC power is turned on, there is a drawback that an inrush current as shown in the input current of FIG. 6 occurs.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a switching regulator that improves the input power factor and reduces the inrush current when the power input is turned on. .

[0005]

In order to solve the above problems, the present invention has an input capacitor, a switching transformer and a switching element connected to an output terminal of an input rectifier for rectifying an input AC voltage, and a secondary side of the switching transformer. A switching regulator in which an output rectifier is connected to the switching transformer, a tertiary winding provided in the switching transformer, a rectifier and a reactor connected between an output terminal of the tertiary winding and the input capacitor, and the input rectifier And a diode connected between the input capacitor and the input capacitor to prevent the rectified voltage from the input rectifier from charging the input capacitor.

[0006]

By the above means, the switching transformer is provided with a tertiary winding, the tertiary winding is half-wave or full-wave rectified, and the rectified voltage is charged into the input capacitor through the reactor, and the main full-wave rectifier is operated. By supplying energy from the input capacitor to the switching transformer and the switching element in the valley portion of the waveform subjected to full-wave rectification, the input power factor is improved and the inrush current when the power input is turned on is reduced.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the construction of an embodiment of the present invention. In FIG. 1, 1 is an input AC terminal, 2 is a main full-wave rectifier, 3 is an input capacitor, 4 is a switching transformer, 5 is a switching element, 6 and 7 are high-frequency rectifiers, 8
Is a reactor, 9 is an output capacitor, 10 is an output terminal,
11 is a drive circuit for driving the control circuit and the switching element 5, 12 and 13 are diodes, 14 is a reactor, and 15 is a tertiary winding of the switching transformer 4.

That is, a tertiary winding rectified voltage obtained by half-wave rectifying the tertiary winding voltage as shown in FIG. 2 is generated on the cathode side of the diode 12. The tertiary winding rectified voltage may be a full-wave rectified voltage of the tertiary winding voltage. The input capacitor 3 is charged through the reactor 14 with the tertiary winding rectified voltage. The energy charged in the input capacitor 3 is supplied from the input capacitor 3 to the switching transformer 4 and the switching element 5 through the diode 13 at the valley portion of the waveform rectified by the main full-wave rectifier 2 to continue the switching operation and output. Keep stable. On the other hand, since the diode 13 prevents the voltage rectified by the main full-wave rectifier 2 from being charged in the input capacitor 3, the peak current as shown in the input current waveform of FIG. The input current waveform becomes as shown in, and the power factor is improved. The above operation is performed even when the power is turned on as shown in FIG.
Since an inrush current as shown in the input current of 1 does not flow, a steady current, that is, an input current without an inrush current as shown in FIG. 3 can be obtained from the beginning. The present invention is not limited to the above embodiment, but can be applied to, for example, bridge type, push-pull type, flyback type and other switching systems.

[0010]

As described above, according to the present invention, by adding the tertiary winding of the switching transformer, the diode and the reactor, it is possible to easily improve the power factor and prevent the inrush current when the power is turned on. Can be done.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention.

FIG. 2 is a waveform diagram showing an example of a tertiary winding rectified voltage according to the present invention.

FIG. 3 is a waveform diagram showing an example of an input current according to the present invention.

FIG. 4 is a diagram illustrating a configuration of a conventional switching regulator.

FIG. 5 is a waveform diagram showing an input voltage waveform and an input current waveform of a conventional switching regulator.

FIG. 6 is a waveform diagram showing an input voltage and an input current of a conventional switching regulator.

[Explanation of symbols]

1 ... Input AC terminal, 2 ... Main full-wave rectifier, 3 ... Input capacitor, 4 ... Switching transformer, 5 ... Switching element, 6, 7 ... High frequency rectifier, 8 ... Reactor, 9 ...
Output capacitor, 10 ... Output terminal, 11 ... Drive circuit for driving control circuit and switching element 5, 12, 13 ... Diode, 14 ... Reactor, 15
... The tertiary winding of the switching transformer 4.

Claims (1)

[Claims] 1. An input capacitor, a switching transformer, and a switching element are connected to an output terminal of an input rectifier that rectifies an input AC voltage, and a switching transformer of 2
In a switching regulator in which an output rectifier is connected to the secondary side, 3
A secondary winding, a rectifier and a reactor connected between the output terminal of this tertiary winding and the input capacitor, and a rectified voltage from the input rectifier connected between the input rectifier and the input capacitor charges the input capacitor. A switching regulator, comprising: