Charles Edgar Powers

US Patent:

49721240, Nov 20, 1990

Filed:

Apr 12, 1990

Appl. No.:

7/464205

Inventors:

Charles D. Powers - Pasadena CA

International Classification:

H05B 3702

US Classification:

315219

Abstract:

A current fed half-bridge parallel resonant inverter for powering one or more discharge-type lamps is comprised of a bifilar wound current feed choke placed in series with a transformer whose secondary resonates with a capacitance placed across the secondary. The bifilar current feed choke is connected in such a way as to insure that that current flows through alternate windings on alternate half cycles of the inverter. Each half of the primary circuit is comprised of one winding of the current feed choke, transformer primary winding, and a switch such as a transistor or the like. An inherent feature of the half-bridge design is that the two halves of the primary circuit operate at different DC offsets. A means is provided for alternately switching the switches of each half of the primary circuit on and off through additional windings of the transformer. A further winding is provided on the transformer to detect lamp ignition through detection of the frequency shift of the inverter caused as current through the lamp after ignition begins to flow through the reactive current limiting element in series with the lamp.