| 摘要 |
The present invention describes a method and circuitry for igniting high frequency operated, high intensity discharge lamps by means of a dual resonant circuit driven by a nonsinusoidal waveform; typically a square wave in the preferred embodiment. A capacitor in series with the lamp is selected to resonate at the fundamental frequency of the applied waveform when the lamp is in the on condition, providing thereby the high frequency power to the lamp for its normal operation. A capacitor in parallel with the lamp is chosen to resonate at a higher harmonic of the applied frequency, typically the third harmonic, when the lamp is in the off condition. Hysteresis heating causes the ignition voltage of the lamp to decrease as higher frequency power is applied, leading to ignition of the lamp at the third harmonic without applying to the lamp one or more pulses of high voltage. An alternative embodiment of the present invention uses dc offset circuitry to apply dc voltage to the lamp at typically an integral multiple of the peak value of the alternating applied voltage.
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