A method and system for providing synchronous rectification in power converters that includes controlling turnoff of a synchronous rectifier according to a timing signal representative of the switching time of a switch that is coupled to input of the power converter. Such a timing signal may be obtained directly or indirectly in various ways; for example, by sensing the voltage across the primary switch, or by sensing the drive voltage of the primary switch. Additional alternatives in an isolated converter having a transformer with a primary winding that is selectively coupled to the electrical power source includes sensing the primary winding voltage, for example, by directly sensing the primary voltage or by sensing the voltage across an auxiliary winding that is closely coupled to the primary winding.