Unified theory of extended-period quasiresonant converters

A switching kchniquc for the convetdon of an ordinary switch or quasiresonant switch into ilti extended-piod rcsonanl switch is prcsentcd. The advantages are that a converter operates uiider zero-ciirreent OL zero-voltage switching condilions and can be controlled by either switching frequency or duty iatio or both Ibr thc rcgiilatiori or rlic oulput powcr. Fainilics or cxtcndcd-pcriod circuits have been developed, and lhc thcory or the cxtendcd-pcriod switches is explaind. Analysis, sjmulatioii and experimental test are used to veriry thc thcory. A number or applications including DCDC convcrlew, power factor correction, off-line power supply and trmscutaneous electrical nei-ve stimulalion arc prcscnlcd.