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:
Mar. 20, 1990
Filed:
Jan. 10, 1989
Charles O Forge, Los Altos, CA (US);
Uniphase Corporation, San Jose, CA (US);
Abstract
A DC switch mode power supply operating from an AC input power source typically has an input stage which includes a rectifier for rectifying the AC input power waveform to provide a DC voltage to the switch mode power supply. This rectifier includes a capacitive storage circuit for storing the DC power to be supplied to the switch mode power supply. To protect the circuit against current surges during start-up, normally an open relay is provided in parallel with a current limiting resistor. This resistor can burn out under some circumstances. This invention replaces the resistor with a capacitor divider circuit containing at least one capacitor in series between the storage capacitor and one of the terminals from the input power supply. A second capacitor can also be provided in parallel with the storage capacitor and one of the diodes of the rectifier. Another diode of the rectifier is in series with the storage capacitor. The resulting circuit limits the initial current surge to the storage capacitor and also functions as a charge pump to make possible the storage of a charge on the storage capacitor greater than the peak input voltage.