Patent ID: 7479740

Claim:
A balancer coil for discharge lamps comprising: first and second coils wound around a common core in such a manner that currents flowing through the first and second coils generate respective magnetic fluxes in the core, at least one of the first and second coils being operably connected to an electrode of a respective one of the discharge lamps, wherein, during operation of the balancer coil, the respective magnetic fluxes are generated towards one another in the core such that the respective magnetic fluxes are substantially canceled out, a sum of reactances of mutual inductance of the balancer coil are larger than a negative resistance of each of the discharge lamps thereby balancing currents of the discharge lamps, and section winding or oblique winding or concentric winding is applied to each of the first and second coils of the balancer coil so as to make self-resonance frequency of each of the two coils higher than an operational frequency of the discharge lamps.