US 7,023,679 B2 · Overvoltage fly-back resonant-type converter

Abstract

A power supply system is implemented without adding a filter circuit by configuring an overvoltage protection circuit without a thyristor. A sub-loop control circuit is added to an AC/DC converter. The sub-loop control circuit is configured such that a photoreceptor side transistor of a photocoupler 26 has the collector terminal connected to the gate terminal of a MOS-FET 2 via a resistor 38, and the emitter terminal connected to the base terminal of a transistor 3, and that the phototransmitter side of the photocoupler 26 is connected to an operational amplifier 39, resistors 40–43, and a Zener diode 44. In addition, in a DC—DC converter, a Zener diode 45 is connected across the input of the converter and the non-inverting input terminal of a comparator 33 with the anode of the Zener diode being connected to the non-inverting input terminal.

Claims3

Dependent claims

An AC/DC converter comprising:

a switching device for switching supply of a DC voltage to a primary side of a transformer, said DC voltage being obtained by rectifying and smoothing an AC voltage fed from a commercial power supply;
a rectifier circuit for rectifying a secondary side output of said transformer;
a first control circuit for controlling said switching device based on a detected voltage of an output terminal such that the voltage of the output terminal becomes a constant output;
and
a second control circuit for controlling said switching device based on the detected voltage of the output terminal such that the voltage of the output terminal becomes a predetermined voltage higher than the constant output voltage, when said first control circuit fails to control the voltage of the output terminal to become the constant output voltage.

2 more elements

Dependencies are inferred from the claim text.

Overvoltage fly-back resonant-type converter

Life of this patent

Overvoltage fly-back resonant-type converter

Life of this patent

Abstract

Claims3