Patent ID: 6051934
Filing Date: 2000-04-18
Classification: H05B,Y02B,Y10S

Abstract:
A ballast circuit for a gas discharge lamp with high speed gate drive circuitry, comprising:(a) a resonant load circuit including a resonant inductance, a resonant capacitance, and means for connecting to a gas discharge lamp;(b) a d.c.-to-a.c. converter circuit coupled to said 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; and(c) a gate drive arrangement for regeneratively controlling said switches, comprising:(i) a driving inductor connected between said common node and said control nodes and mutually coupled to an inductor in said resonant load circuit for sensing current in said circuit; and(ii) a bidirectional voltage clamp connected between said common node and said control nodes;(d) said clamp comprising:(i) a first Zener diode with an associated, serially connected, one-way current valve connected between said control nodes and said common node, and poled in one direction;(ii) a second Zener diode with an associated, serially connected, one-way current valve connected between said control nodes and said common node, and poled in an opposite direction;(iii) said valves being connected to their associated Zener diodes in such manner as to prevent said diodes from operating in a forward-biased mode; and(iv) said valves having shorter reverse recovery times than reverse recovery times of their associated Zener diodes.