US Patent 7173831 Power converter having a primary side switching circuit

In one embodiment, an apparatus includes a transformer having a primary winding and a secondary winding and a switching circuit to facilitate a periodic application of an input voltage to the primary winding. The switching circuit includes an active switch and a capacitor commonly coupled to the primary winding. In one embodiment, the apparatus further includes a synchronous rectification circuit coupled to the secondary winding to generate a rectified signal, an output filter coupled to the synchronous rectification circuit to provide an output voltage in response to the rectified signal, and a control circuit coupled to the output filter to receive the output voltage and coupled in a switching control relationship with the active switch and the synchronous rectification circuit.