RCC power supply with remote disabling of oscillation frequency control

摘要

A self-oscillation switching power supply apparatus of the ringing choke converter type comprises a transformer T including a primary winding N1, a secondary winding N2, and a feedback winding NB; a switching transistor Q1 which oscillates in a self-oscillating fashion in response to a feedback signal from the feedback winding NB thereby turning on and off the current flowing through the primary winding; a rectifying and smoothing circuit connected to the secondary winding; an oscillation frequency control circuit including a control transistor Q3 for controlling a control signal input to the switching transistor Q1 thereby controlling the control transistor Q3 so as to extend the off-time in the self-oscillation period of the switching transistor Q1; and an oscillation frequency control disabling circuit for disabling the control of the control transistor Q3 in accordance with a remote signal.