Self-oscillation type switching power supply

摘要

A self-oscillation type switching power supply comprises a transformer having a primary winding, a secondary winding, a feedback winding, and a control winding as necessary, a switching transistor interrupting a current in said primary winding, a control transistor controlling a positive feedback signal from said feedback winding to the switching transistor, and a time constant circuit charged by a starting voltage of said feedback winding or said control winding with a predetermined time constant and further applying a control voltage to said control transistor. The self-oscillation type switching power supply further comprises an impedance circuit which blocks a reverse bias from said feedback winding or said control winding to said control transistor, disposed between a control voltage input block to said control transistor and said time constant circuit.