Patent ID: 7724555

Claim:
A converter, comprising: at least one input line operative to receive power from a first supply, at least one output line operative to supply power to a first load with a positive current, a push-pull switching conversion circuit for converting input power into output power and including: one or more input switches each having a switch control input, a transformer having primary windings responsive to the input switches, two independently controlled synchronous rectifiers operatively connected to secondary windings of the transformer each having a switch control input and an output operatively connected to the output line of the converter in a push-pull configuration, one or more energy storage elements operatively connected to the output line of the converter, and a fixed-frequency synchronous rectifier control circuit having an output operatively connected to each of the synchronous rectifiers via its switch control input to independently control them, and including circuitry operative to cause the synchronous rectifiers to selectively both: a) pass a negative current when stepping to a reduced load, and b) block the negative current when stepping to an increased load during operation of the converter after startup but before shutdown.