Pulse injection starting for high intensity discharge metal halide lamps

Claim 1

A light source comprising: a high pressure discharge lamp including a discharge tube having electrodes sealed therein at opposite ends and enclosing a fill material which emits light during discharge; and a starting circuit including a spiral line pulse generator including two conductors and two insulators, each in the form of an elongated sheet, in an alternating and overlapping arrangement which is rolled together in a spiral configuration having a plurality of turns, said spiral line pulse generator including an output terminal coupled to one of said electrodes of said lamp and a pair of input terminals, one of said input terminals and the other of said electrodes of said lamp being adapted for coupling to a source of lamp operating power and for delivering lamp operating power, received from the source, through said spiral line pulse generator to said discharge lamp, means for applying ac voltage between the conductors of said spiral line pulse generator, and a breakdown switch coupled between the conductors of said spiral line generator and arranged to short circuit said conductors at a firing selected to be less than the peak of said ac voltage, and higher than the normal discharge voltage of said lamp whereupon said spiral line pulse generator provides at said output terminal a high voltage, short duration pulse of sufficient energy to initiate discharge in said discharge lamp causing said ac voltage to drop below said firing voltage.