Patent ID: 8120264

Claim:
A discharge lamp lighting circuit for supplying an AC power to a discharge lamp, the discharge lamp comprising: first and second converters for receiving a DC voltage and stepping up the voltage; and a controlling circuit for driving the first and second converters alternately at a first frequency and stopping an operation of the converter that is not driven such that the AC power is supplied to the discharge lamp to execute a lighting operation, wherein the first and second converters are implemented by any of (a) a converter having an insulated-type first transformer, a first switching element connected in series between a DC power supply and a primary winding of the first transformer, and a second switching element connected in series between an output end and a secondary winding of the first transformer, wherein the first and second switching elements are arranged to be driven in synchronism with each other in each half period of the first frequency at a second frequency higher than the first frequency, (b) a converter having an insulated-type second transformer, a third switching element connected in series between the DC power supply and a primary winding of the second transformer, a first rectifying element connected in series between one output end and a secondary winding of the second transformer, and a fourth switching element connected between one output end and the other output end, wherein the converter is arranged so that the fourth switching element is put in an OFF state while the third switching element executes a driving operation, and the fourth switching element is put in an ON state while the third switching element executes a stopping operation, or (c) a converter having an insulated-type third transformer, a fifth switching element connected in series between a DC power supply and a primary winding of the third transformer, a sixth switching element connected in series between an output end and a secondary winding of the third transformer, and a second rectifying element connected in parallel with the sixth switching element, wherein the converter is arranged such that the sixth switching element is put in an OFF state while the fifth switching element executes a driving operation, and the sixth switching element is put in an ON state while the fifth switching element executes a stopping operation.