Switching power source apparatus.

摘要

The positive electrode output terminal of full-wave rectifying circuit 3, primary winding 81 of transformer 8, switch element 9, choke coil 5, and negative electrode output terminal of full-wave rectifying circuit 3 are connected in series in this order, smoothing capacitor 4 is connected parallel to the series circuit of the primary winding 81 and switch element 9, first and second diodes 61, 62 are provided from the input terminal of the full-wave rectifying circuit 3 to the connection point of primary winding 81 and switch element 9, rectifying and smoothing circuit 20 is connected to the secondary winding 82 of the transformer 8, and the control circuit 40 is provided to control the on/off ratio of the switch element 9 so as to stabilize the direct-current output voltage to be supplied to the load 25, and thereby the input characteristic of superior power factor and small input current harmonic currents is realized, while the number of constituent parts intervening in the route of the current of the choke coil 5 is decreased and the conduction loss is reduced. <IMAGE>