JPH05168240A - Switching regulator - Google Patents

Abstract

PURPOSE:To obtain a switching regulator which improves the input power factor and which lightens the rush current at the time of power input. CONSTITUTION:An input capacitor 3, a switching transformer 4, and a switching element 5 are connected to the output terminal of a main full wave rectifier 2, which rectifies input AC voltage. Furthermore, this is a switching regulator where high frequency rectifiers 6 and 7a are connected to the secondary side of the switching transistor 4. And, this is constituted, being equipped with a transformer 15 connected in parallel with the switching transformer 4, a diode 12 and a reactor 14 connected between the output terminal of the secondary winding of this transformer 15 for charge and the input capacitor 3, and a diode 13 being connected between a main full wave rectifier 2 and the input capacitor 3 and hindering the rectified voltage from the main full wave rectifier 2 being charged in the input capacitor 3.

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 an object of the present invention is 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 having an output rectifier connected to a charging transformer connected in parallel with the switching transformer, a rectifier and a reactor connected between an output terminal of a secondary winding of the charging transformer and the input capacitor. And a diode connected between the input rectifier and the input capacitor to prevent the rectified voltage from the input rectifier from being charged in the input capacitor.

[0006]

By the above means, a charging transformer is provided in parallel with the switching transformer, the output voltage of the secondary winding of the charging transformer is half-wave or full-wave rectified, and this rectified voltage is input to the input capacitor via the reactor. By charging and supplying energy to the switching transformer and switching element from the input capacitor in the valley portion of the waveform that is full-wave rectified from the main full-wave rectifier, the input power factor is improved and the inrush current when the power input is turned on is reduced. To do.

[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 charging transformer.

That is, a charging transformer rectified voltage obtained by half-wave rectifying the output voltage of the secondary winding of the charging transformer 15 as shown in FIG. 2 is generated on the cathode side of the diode 12. This charging transformer rectified voltage is the charging transformer 15
It may be a voltage obtained by full-wave rectifying the output voltage of the secondary winding. The input capacitor 3 is charged through the reactor 14 with the charging transformer rectified voltage. The energy charged in the input capacitor 3 is transferred from the input capacitor 3 to the diode 1 at the valley portion of the waveform rectified by the main full-wave rectifier 2.
3 is supplied to the switching transformer 4 and the switching element 5 to continue the switching operation and keep the output 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 leads to the fact that the inrush current as shown in the input current of FIG. 6 does not flow even when the power input is turned on. Therefore, the steady current, that is, the input current without the inrush current as shown in FIG. 3 is obtained from the beginning. You can 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 charging transformer, the diode and the reactor, the power factor can be easily improved and the inrush current at power-on can be prevented economically. Out.

[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 charging transformer 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
… A charging transformer.

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 having an output rectifier connected to the secondary side, a charging transformer connected in parallel with the switching transformer, and a rectifier connected between an output terminal of a secondary winding of the charging transformer and the input capacitor. And a reactor, and a diode connected between the input rectifier and the input capacitor to prevent a rectified voltage from the input rectifier from charging the input capacitor.