Pseudo push-pull dc:dc power converter topology

Abstract

A pseudo-push-pull DC:DC converter topology replaces one primary switching transistor with a high speed passively switched diode coupled between one end of a transformer first primary winding and ground. A second primary winding is coupled to ground via a solid state switch that is driven with a control circuit that outputs a single drive signal of slightly less than 50% duty cycle. The other ends of the first and the second transformer primaries are coupleable to a source of Vin. The topology includes a gapped transformer whose transformer core stores sufficient electromagnetic energy when the solid state switch is turned-on by the control circuit to drive a load coupled to the transformer secondary when the solid state switch is turned-off. When the solid state switch is turned-off by the control circuit, the diode self-biases on, coupling the first transformer primary winding between Vin and ground, as though a perfectly driven solid state switch were turned-on. Converter secondary or output voltage rectification is very efficient in that a pseudo-push-pull signal is generated, without requiring a complicated prior art push-pull control circuit on the primary side.