| 摘要 |
PROBLEM TO BE SOLVED: To reduce change of envelope waveform of a lamp current, and improve a peak factor by controlling an inverter circuit based on information relating to the envelope waveform. SOLUTION: A voltage of a commercial power supply E is rectified by a rectifier circuit, it is smoothed by a capacitor C1, and power is supplied to an inverter circuit 2. At the inverter circuit 2, a control circuit 4 controls a field effect transistor Q1 by a zero-voltage switching for high frequency switching based on resonance of a parallel resonance circuit of a primary winding Tr11 of an inverter transformer Tr1 and a capacitor C2, and an output of an output winding Tr22 of a detection transformer Tr2, so a fluorescent lamp FL is high frequencylighted. A current detected by a detection winding Tr13 is smoothed by a capacitor C5 to be an envelope current to be inputted to a base of a transistor Q2. In the case where an envelpe current value is increased, an output of the inverter circuit 2 is decreased, thereby a peak factor is improved. |
