Elegant Design Solutions Inc.

George A Ellison

Kenneth D Sexton

Robert A Hocker

James R Kellogg

Patrick W McCurry

Karl Boekelheide

A computer-controlled, uninterruptible power supply system is disclosed. The system selectively operates from more than one input source of power, e.g. an AC line input, an external DC input and internal batteries. The system is of the type which utilizes one or more switch mode converters and is well suited for use in computer systems. The switch mode regulator has a PWM clock signal and provides a PWM drive signal. The PWM clock signal frequency is substantially greater than the PWM drive signal frequency. Transferring between the DC power sources is done in a manner substantially transparent to the regulator and the load, generally as follows. A signal indicating a transfer to a selected one of the DC power sources is gated in response to the PWM clock signal to form a first logic signal that is synchronized to the PWM clock signal. The first logic signal is gated in response to the PWM drive signal so as to form a second logic signal that is further synchronized to the PWM drive signal. Finally, the PWM drive signal is gated to a selected switching circuit responsive to the second logic signal, so that transfers between the DC power sources are fully synchronized to the PWM clock signal and to the PWM drive signal.

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Salem, OR, United States of America

George A Ellison