Used for: Isolated supplies where high voltages on switches are acceptable

Literature references


  • Both switches referenced to ground so easy to drive
  • Can be effective for low voltages where peak drain/collector voltage not so high


  • Must use current mode control - voltage mode causes staircase saturation
  • Peak switch voltage = 2 x Vcc + spikes
  • Need centre-tapped primary
  • Need centre tapped secondary unless lossy full bridge rectifier used or current doubler
  • Poor transformer utilisation

sine royer.pdf

Push-pull, self oscillating, sine wave type


  • Primary transistors alternately switch
  • Can be seen as two single ended forward converters operating 180 degrees apart