Patent ID: 7282868

Claim:
An inverter circuit for discharge lamps for multi-lamp lighting said circuit comprising: at least two coils connected to a secondary winding of a step-up transformer of the inverter circuit, the at least two coils being arranged and magnetically coupled to each other to form a shunt transformer for shunting current such that magnetic fluxes generated by the at least two coils are opposed to each other to cancel out, the at least two coils being configured to ensure a sufficient inductance for the shunting transformer, discharge lamps connected to said coils, respectively, with currents flowing therethrough being balanced with each other, wherein a large number of discharge lamps are arranged as backlights in a surface light source, an electric conductor being arranged adjacent to said discharge lamps, wherein the discharge lamps arranged as said backlights have a negative resistance characteristic, the inductance of the shunting transformer is sufficient to cause a reactance of the inductance of said shunt transformer to exceed the negative resistance of each of said discharge lamps arranged as said backlights during the current balancing operation, thereby causing each of said discharge lamps to be lit, said reactance being in an operating frequency of the inverter circuit, a shunt circuit is formed by arranging a plurality of shunt transformers such that shunt coils of the plurality of shunt transformers are connected to form a multi-tier structure, shunt coils associated with at least one tier in the multi-tier structure being operably connected to the discharge lamps, and a reactance value of an upper shunt coil is sequentially reduced in comparison with that of a lower shunt coil, whereby a number of turns of shunt coils is progressively reduced.