Switching power-supply device

Patent metadata

Field	Value
Publication number	US-2016294293-A1
Application number	US-201514972084-A
Country	US
Kind code	A1
Filing date	Dec 17, 2015
Priority date	Mar 30, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

A switching power-supply device applies a DC voltage to a primary winding of a transformer and performs a switching operation of a switching element connected to a primary winding to generate and output an output voltage to a load, and the switching power-supply device includes: an error amplifier, which compares the output voltage with a reference voltage and sends an error voltage as a feedback signal to a primary side; a frequency generation circuit, which generate a switching frequency according to the feedback signal; an off timing determination circuit, which determines a timing at which the switching element is turned off, by comparing the feedback signal with a current flowing through the switching element; and a frequency correction circuit, which corrects the switching frequency generated by the frequency generation circuit, according to an on-duty of the switching element.

First claim

What is claimed is:

1 . A switching power-supply device, which applies a DC voltage obtained by rectifying input voltage of AC power source to a primary winding of a transformer and performs a switching operation of a switching element connected to the primary winding of the transformer to generate a pulse voltage on a secondary winding of the transformer and output an output voltage to a load, the output voltage being rectified and smoothed by a rectification and smoothing circuit of a secondary side having a rectifier diode and a smoothing capacitor, the switching power-supply device comprising:
an error amplifier, which compares the output voltage with a reference voltage and sends an error voltage as a feedback signal to a primary side; a frequency generation circuit, which generate a switching frequency according to the feedback signal; an off timing determination circuit, which determines a timing at which the switching element is turned off, by comparing the feedback signal with a current flowing through the switching element; and a frequency correction circuit, which corrects the switching frequency generated by the frequency generation circuit, according to an on-duty of the switching element.

2 . The switching power-supply device according to claim 1 ,
wherein the frequency correction circuit generates a correcting current increased as the on-duty increases, and wherein the frequency correction circuit superimposes the correcting current on a current flowing through the switching element, which is compared with the feedback signal by the off timing determination circuit.

3 . The switching power-supply device according to claim 2 ,
wherein the frequency correction circuit generates the correcting current from a predetermined on-duty.

Assignees

• Sanken Electric Co Ltd

Inventors

• Hayakawa Akira
• Shimada Masaaki

Classifications

• H02M3/28 Primary

  using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC · CPC title

• H02M3/33523 Primary

  with galvanic isolation between input and output of both the power stage and the feedback loop · CPC title

• H02M1/10

  Arrangements incorporating converting means for enabling loads to be operated at will from different kinds of power supplies, e.g. from AC or DC · CPC title

• H02M7/04

  by static converters · CPC title

• H02M1/007

  Plural converter units in cascade (push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826) · CPC title