Patent ID: 6720740
Filing Date: 2004-04-13
Classification: H05B,Y02B

Abstract:
A discharge lamp ballast circuit having a DC/DC converter circuit that has a switching device for switching a primary current on a fly-back transformer, comprising:a snubber circuit for the switching device; a capacitor connected in parallel with one of the switching device and the fly-back transformer for generating a resonance with a leakage reactor of the fly-back transformer; and a control circuit for driving the switching device in a PFM manner, for performing one of a non-zero voltage switching and a non-zero current switching during a lighting preparation period of the discharge lamp, and for performing one of a zero voltage switching and a zero current switching after the lighting preparation period, wherein the control circuit drives the switching device so that the switching device switches after the voltage on a primary coil of the fly-back transformer reaches a peak value for performing the non-zero voltage switching.