Unified theory of extended-period quasiresonant converters

A switching technique for the conversion of an ordinary switch or quasiresonant switch into an extended-period resonant switch is presented. The advantages are that a converter operates under zero-current or zero-voltage switching conditions and can be controlled by either switching frequency or duty ratio or both for the regulation of the output power. Families of extended-period circuits have been developed, and the theory of the extended-period switches is explained. Analysis, simulation and experimental test are used to verify the theory. A number of applications including DC/DC converters, power factor correction, off-line power supply and transcutaneous electrical nerve stimulation are presented.