This paper presents the design of practical isolated and non-isolated flyback converters that reduce no-load power to zero. To achieve this goal, low leakage current through the power MOSFET, low transformer distributed capacitance, low synchronous rectification losses, RCD primary snubber optimization, and very low current draw by the control IC will all be examined. A design example is presented to show how the advancement of IC technology can virtually eliminate wasted no-load power. A new transformer winding configuration that is critical to achieving zero no-load power is also presented.
