| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting system which can be protected under an abnormal load, reduce rush current, and be miniaturized. SOLUTION: Dc power obtained when an ac power supply Vs is rectified by a rectifier DB1 and then smoothed by a capacitor Co is converted to high-frequency power by a series circuit of the primary winding Np of a transformer T which is connected to the output end of the rectifier DB1 and a switching circuit Q1, and dc power obtained from the high-frequency power via the secondary winding Ns of the transformer T and a diode D1 is supplied to an illumination load IL. The switching element Q1 is PWM controlled by a drive circuit 1 with high frequencies. At startup, the power supply Vcc of the drive circuit 1 is obtained from a first dc voltage V4 obtained by conversion of the ac power supply Vs using a control power circuit 4; after startup the power supply Vcc is obtained from a second dc voltage V2 obtained via a diode D2 and a capacitor C3 from a secondary voltage generated in the feedback winding Nc of the transformer T. |
