Switching power source device

Claim 1

A switching power source device comprising: a rectifying smoothing circuit including a small-capacitance capacitor as a circuit for rectifying and smoothing a commercial ac input power source, a resonant frequency controlled type resonant converter circuit including a self-oscillating circuit for switching controlling of an output of said rectifying smoothing circuit with a fixed switching frequency, a converter-driven transformer having a primary circuit and a secondary circuit, said secondary circuit being connected to said resonant converter circuit for on-off control of the rectified and smoothed input power source, a power-source regulating transformer circuit section including a primary circuit connected to said primary winding of said converter-driven transformer, a secondary winding insulated with respect to said primary winding, and a control winding having the direction of winding at right angles to the winding direction of said primary and secondary windings, a controller for controlling the control current of said control winding of said power-source regulating transformer circuit section in a direction of rendering the average value of the dc output voltage of said transformer circuit section constant, and a rectifying smoothing circuit including a rectifying smoothing capacitor determining the ripple voltage of the dc output voltage of said transformer circuit section in conjunction with a load power.