Patent ID: 6933684
Filing Date: 2005-08-23
Classification: H05B

Abstract:
1. An electronic ballast for a fluorescent lamp tube, comprising: an electro-magnetic compatible filter circuit; a rectifier circuit; a power factor correcting circuit; a DC filter circuit; a DC/AC converter circuit; an adjusting circuit; an output circuit; and a control circuit, wherein the adjusting circuit, the output circuit and the control circuit are coupled between the DC/AC converter circuit and a lamp tube, and the adjusting circuit, the output circuit and the control circuit are configured to limit a voltage across the lamp tube and provide a preheating voltage in a filament preheating stage, and to simultaneously provide a lamp lit voltage and cutoff the preheating voltage after the preheating stage and wherein the DC/AC converter circuit is half-bridge type converter circuit, in which a same polarity end of a primary winding of a transformer in the adjusting circuit is connected in series with a different polarity end of a primary winding of a transformer in the output circuit.