Patent ID: 6150769
Filing Date: 2000-11-21
Classification: H05B

Abstract:
A ballast circuit for a gas discharge lamp with a tapless feedback circuit, comprising:a) d.c.-to-a.c. converter circuit with means for coupling to a resonant load circuit, for inducing a.c. current therein, said converter circuit comprising:i) a pair of switches serially connected between a bus conductor at a d.c. voltage and a reference conductor, the voltage between a reference node and a control node of each switch determining the conduction state of the associated switch;ii) the respective reference nodes of said switches being connected together at a common node through which said a.c. current flows, and the respective control nodes of said switches being connected together;b) a gate drive arrangement for regeneratively controlling said first and second switches, said arrangement comprising:i) a coupling circuit including an inductor for coupling to said control nodes a feedback signal representing current in said load circuit; andii) a tapless feedback circuit for providing said feedback signal; said feedback circuit comprising a capacitor coupled at one end to said common node in such manner as to conduct load current, and coupled at another end to said inductor.