Patent ID: 6879113

Claim:
An electronic ballast for powering an arc discharge lamp load comprising: a power supply generating a high voltage DC signal; a low frequency time varying reference signal; a high voltage, AC voltage controlled current source generating a high frequency, high voltage substantially rectangular signal at a source output by switching the high voltage DC signal based on the low frequency time varying reference signal, the current source comprising a bridge switching circuit with a first leg and a second leg, each leg including two switches in series, at least one current sensor generating current signals proportional to the current in the first leg and the second leg, and a pulse width modulator generating switching signals for each switch in the bridge based on the reference signal and the current signals; and a low pass filter connecting between the first leg and the second leg at a point on each leg between the switches on that leg, the low pass filter having a cutoff frequency between the high frequency and the low frequency, the low pass filter outputting high voltage at the low frequency for driving the arc discharge lamp load.