Inverter for operating a gaseous discharge lamp

Claim 1

A dc to ac inverter with power limiting for operation of a gaseous discharge light source through pre-ignition, arc stabilization, warm-up, and final run states comprising: A. input terminals for connection to a dc electrical source, B. output terminals for connection to a gas discharge light source, C. a transformer comprising: (1) a core of substantially linear magnetic material for main flux pursuing a main magnetic path, aperture means in a localized region of said core defining a second magnetic path, (2) a main primary winding and a main secondary winding associated with said main magnetic path, said main windings being loosely coupled to provide an equivalent output inductance having significant ballasting effect, (3) magnetic state responsive control winding means comprising a primary and a secondary control winding traversing said aperture means, said secondary control winding being coupled through said second magnetic path to said primary control winding, substantially uncoupled to main flux in the absence of saturation effects, and producing an output which reverses in sense at a predetermined flux level, D. transistor switching means serially coupled with said main primary winding across said input terminals for producing a periodic output in said main output winding with substantial harmonic content, and responsive to said control winding to limit the average current supplied to said light source, said current limiting effect in combination with said equivalent output inductance precluding excessive power dissipation during warm-up and final run states of the lamp, and E. capacitive means connected in shunt with said output winding and across said output terminals to resonate with said equivalent inductance at a prescribed harmonic to produce the enhanced output voltage required for pre-ignition and arc stabilization.