The circuit is intended for simple, non-isolated applications. The isolated flyback or single switch forward could certainly be used but not to any cost advantage due to additional voltage/current stress issues and generally more complex and/or additional magnetics. Tests performed on the circuit show a significant efficiency advantage over the conventional buck when low output voltages (high conversion ratios) are desired. The use of Schottky diodes or a synchronous rectifier for the freewheel diode additionally improves efficiency. EMI generation is significantly less than an isolated flyback or forward configuration.
The relative FET withstand voltage must increase for a given voltage stress %.
This increases its Rdson and thus its losses for a given FET voltage stress %. Also increased on time (increased duty cycle)conduction losses as switch + inductor must provide Volt-Second energy storage.
This is offset by this designs primary side current reduction relative to output average current. also on the positive side of things the diode withstand voltage or synch rectifier withstand voltage is reduced allowing reduced freewheeling conduction losses. Has anybody workedthisout in spreadsheet (or Mathcad workbook) form to see if and where any efficiency gain are at and where the optimum sweet spot or range is located? Using different voltage withstanding diodes, switches and sync rectifiers?
NASA's Orion Flight Software Production Systems Manager Darrel G. Raines joins Planet Analog Editor Steve Taranovich and Embedded.com Editor Max Maxfield to talk about embedded flight software used in Orion Spacecraft, part of NASA's Mars mission. Live radio show and live chat. Get your questions ready.
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