William R Slack

US Patent:

49300610, May 29, 1990

Filed:

Apr 7, 1989

Appl. No.:

7/335012

Inventors:

William F. Slack - Lake Hiawatha NJ
James C. Wadlington - Mendham NJ

Assignee:

AT&T Bell Laboratories - Murray Hill NJ

International Classification:

H02M 112

US Classification:

363 44

Abstract:

An arrangement for improving the power factor at the input of an off-line switching type power supply is operative to extend the duration of the pulse current conducted by the diode rectifiers. A parallel LC ringing circuit is introduced between the AC line and the rectifier of the switching type power supply to enhance the voltage enabling conduction of the rectifying diodes and hence initiate current flow through the rectifying diodes earlier in each half cycle. This extends the conduction interval of the rectifying diodes significantly and enhances the power factor at the input to the switching type power supply.