Patent ID: 7453216

Claim:
A current resonance inverter circuit for a discharge lamp comprising: a step-up transformer; and a current transformer, a primary winding of said step-up transformer having a center tap being connected to a power source, two other terminals of said primary winding being connected to collectors of two transistors, respectively, emitters of said two transistors being connected to respective terminals of a primary winding the current transformer, the current transformer having a center tap, said center tap of said current transformer being connected to a ground side, a secondary winding of said current transformer being connected to bases of said two transistors to detect emitter currents of said two transistors in order to detect a resonance current, thereby performing oscillation, further comprising a secondary side circuit of said step-up transformer including: an inductor with a predetermined leakage inductance value which occurs from said secondary winding; said discharge lamp of said secondary winding; a distributed capacitor of said secondary winding; a capacitor for adjusting a resonance frequency; and a capacitor for handling stray capacitance generated in the vicinity of said discharge lamp, wherein the distributed capacitor, the capacitor for adjusting the resonance frequency, and the capacitor for handling stray capacitance form a secondary side capacitance, the secondary side capacitance and the predetermined leakage inductance value which occurs from said secondary winding included in the step-up transformer constituting a serial resonance circuit having a predetermined Q value, and wherein said discharge lamp is connected in parallel with the said secondary side capacitance, whereby a predetermined step-up ratio is obtained to light said discharge lamp, and a phase of the primary winding current of said step-up transformer is approximately the same as a phase of a real value of the primary winding voltage of said step-up transformer.