Importance

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Abstract

A main power supply unit 10 of this power supply apparatus for laser comprises asingle-phase rectifying circuit 16 for receiving a single-phase AC voltage E.sub.A at a commercial frequency to convert (rectify) it into a direct current, a capacitor 18 for temporarily storing the DC power from the single-phase rectifying circuit 16, a charging circuit 20 connected between the single-phase rectifying circuit 16 and the capacitor 18, and a lamp current supply circuit 22 connected between the capacitor 18 and an excitation lamp 102. The charging circuit 20 includes a switching element 24 for charging connected in parallel with the capacitor between the single-phase rectifying circuit 16 and the capacitor 18, an inductance coil 26 connected in series between the single-phase rectifying circuit 16 and the switching element 24 for charging, and a diode 28 connected in series between the switching element 24 for charging and the capacitor 18. A power-factor control circuit 34 provides a control of switching action of the switching element 18 for charging at a high frequency of 70 kHz for instance so as to allow a charging current I.sub.C supplied to the capacitor 18 to be in phase with a DC voltage E.sub.B output from the single-phase rectifying circuit 16.

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First Claim