A method for generating secondary-referenced control power (power convertors)

A method is described that uses a startup oscillator and the principal power components to generate a secondary-referenced voltage for the control circuit of an isolated power converter. The method eliminates the need for a separate housekeeping power supply in these converters. Example designs are presented for a bipolar transistor forward converter, a bipolar transistor flyback converter, a MOSFET forward converter, and a two-MOSFET forward converter. It is concluded that this isolated bootstrapped approach is a simple, cost-effective method for providing secondary-referenced control power.<
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