Abstract: A circuit for driving a light emitting diode (LED) comprises: an alternating voltage power supply, comprising a triac dimmer having a firing angle and output terminals that provide power to the LED; a zero crossing detector that detects a polarity change of the alternating voltage provided by the alternating voltage power supply and provides a zero crossing output signal indicative of the zero crossing; a timer triggered by the zero crossing output signal that generates a timer output signal during a time period of the timer; and LED power circuitry that reduces current to the light emitting diode based upon timing characteristics of the timer output signal.

Abstract: In order to suppress a peak of an excessive current and suppress a variation in a resonance voltage of a resonator, which are likely to occur immediately after a discharge lamp starts lighting, in a case where a high-frequency current continuously flows asymmetrically with respect to a zero current instead of flowing symmetrically on positive and negative sides immediately after the lighting since electrodes of the discharge lamp are not evenly warmed, the resonance voltage and the high-frequency current are finely adjusted in a resonance voltage and high-frequency current setting method including setting a drive frequency of an inverter circuit and varying output from a down-converter.