A unity power factor high frequency parallel resonant electronic ballast

An electronic-ballast circuit that operates at a 20 kHz resonant frequency with zero voltage switching is described for a metal halide lamp. In order to minimize the switching loss, the ballast employs the zero-voltage switching, scheme in which the switching instants are synchronized with the voltage zero crossing points. For a base driver, self-oscillation is used. The base driver and controller consist of one leg of a transformer, two resistors, and two capacitors, making the ballast more compact, lighter, and more reliable. A prototype ballast for a 175 W metal halide lamp has been fabricated and tested. All the features of the ballast have been verified experimentally.<>