Lighting power source with controlled charging operation for driving capacitor

摘要

A lighting power source provides AC or DC power as needed to power an electric light source. A first switching element and a diode are coupled in series across output ends of a DC power source, with a second switching element coupled across the diode. An inductor forms an output loop with the diode. A driving capacitor has a first end coupled to a node between the first switching element and the diode. A charging power source is coupled to a second end of the driving capacitor and supplied with power from the DC power source. During a charging operation, a control circuit charges the driving capacitor by turning on the second switching element while maintaining the first switching element in an OFF state. During a normal operation which follows the charging operation the control circuit repeatedly turns on/off the first switching element while maintaining the second switching element in the OFF state.