Importance

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Abstract

A high pressure discharge lamp ballast includes an AC power supply means for supplying a square wave alternating current to a high pressure discharge lamp having a bulb in which first and second electrodes are disposed so as to face each other. In the high pressure discharge lamp ballast, one modulation period (T0) of the square wave alternating current supplied by the AC power supply means comprises a first asymmetrical current period (T1) for melting a protrusion formed at the tip of the first electrode and growing a protrusion formed at the tip of the second electrode, a symmetrical current period (Ts) for conducting current having a positive-negative symmetrical square wave, and a second asymmetrical current period (T2) for growing the first protrusion and melting the second protrusion.

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First Claim