The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 26, 1997
Filed:
Jun. 20, 1995
Fumiaki Nakao, Kosai, JP;
Tetsuya Suzuki, Tahara-cho, JP;
Katsuo Yamada, Kosai, JP;
Shoichi Wakao, Hamamatsu, JP;
FDK Corporation, Tokyo, JP;
Abstract
In a switching power supply a stable dc output voltage having a higher power factor is obtained even for an unstable ac input voltage using a sufficiently broadened duty ratio of the switching signal. The switching power supply include a rectifying circuit 10 for full-wave rectifying an ac input voltage to output a pulsating current, a chopper circuit having a switching device Q1 driven at a sufficiently higher frequency than that of the ac input voltage, an inductor L1 connected in series with the switching device Q1 between output terminals of the rectifying circuit 10, and a capacitor C1 for smoothing a current fed through the inductor L1 to supply a stabilized dc output voltage, an error amplifier 11 and a multiplier 12 for providing a threshold level signal having a full-wave rectified waveform, in which the phase thereof is the same as that of the ac input voltage, and an amplitude corresponding to an error voltage included in an output voltage of the chopper circuit, a comparator 13 for comparing the current of the switching device Q1 with the threshold level signal, and a monostable multivibrator 20 for driving the switching device Q1 according to the output signal of the comparator 13. The turn off time of Q1 becomes shorter when the immediately preceding turn on time becomes longer.