PURPOSE: To reduce the size and the weight of a flyback type ringing choke converter by using the base-driving winding of a converter transformer as a secondary winding in combination.

CONSTITUTION: A ringing choke converter is composed of a constant-voltage controller having first∼second switching transistors (Tr) Q1∼Q2. a converter transformer TS, its primary winding L1, secondary winding L2, an oscillation time constant regulating resistor R1 and capacitor C2, and a constant voltage control Tr Q3. In this case, positive feedback voltage supplying means including a series circuit of a resistor R1 and a capacitor C2 is provided between one end of the winding L2 of the transformer TS and the Trs Q1, Q2. This means uses the base driving winding L3 of the transformer TS as the secondary winding L2 in combination, and supplies its induced voltage as a positive feedback voltage to the base of the Tr Q1. Thus, as the ON/OFF time ratio of the Trs Q1, Q2 is varied, even if a load current increases at the time of small input voltage, an output voltage does not lower.