Importance

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Abstract

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.

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First Claim