Patent Number: 6,429,604

Title: Power feedback power factor correction scheme for multiple lamp operation

Abstract: A ballast circuit for a single or multiple lamp parallel operation where at each lamp a condition may be controlled such that the amplitude of a resonant inductor current and an output voltage are almost constant in the steady state. The circuit consists of a half-bridge of a DC storage capacitor, a DC blocking capacitor, power transistors which alternately switch on and off and have a 50% duty ratio, and an LLC resonant converter having a resonant inductor and one or more resonant capacitors. The circuit also includes an output transformer providing galvanic isolation for a double path type power feedback scheme. The output transformer produces magnetizing inductance utilized for power feedback circuit optimization and is connected right after the resonant inductor of the half-bridge circuit.

Inventors: Chang; Chin (Yorktown Heights, NY)

Assignee: Koninklijke Philips Electronics N.V.

International Classification: H05B 41/282 (20060101); H05B 41/28 (20060101); H05B 037/00 ()

Expiration Date: 08/06/2019