the converter delivers current to an intermittently energized load and includes a coupled inductor having a primary winding , a secondary winding and a feedback winding . a switching transistor is coupled in series with the primary winding of the inductor and switches between conductive and non - conductive states to control the flow of current through the primary winding . a positive drive circuit provides positive bias voltage to the switching transistor . a current limiting circuit senses the voltage across the base - emitter junction of the switching transistor to measure the primary winding current , removes the positive bias voltage when the primary winding current reaches a predetermined value , and thereby switches the transistor out of the conductive state into the non - conductive state . a semiconductor switch includes a control lead coupled to a voltage divider which applies a scaled voltage to the control lead causing the semiconductor switch to conduct when the switching transistor base - emitter voltage reaches a predetermined current limit voltage representative of a preselected switching transistor collector current limit . the semiconductor switch then shunts the positive bias voltage away from the switching transistor base and switches that transistor into the non - conductive state .