Patent ID: 8031494

Claim:
A switch-mode power converter including a bias circuit, comprising: a pair of input side power terminals configured to accept power from a power source; a pair of output side power terminals configured to provide power to a load; a power converter power transformer comprising a magnetic core, at least one input side power winding wound on the magnetic core and coupled to an input side of the switch mode power converter, at least one output side power winding wound on the magnetic core and coupled to an output side of the switch mode power converter, said power converter power transformer configured to provide a galvanic break to isolate said input side power terminals from said output side power terminals of said switch-mode power converter; at least one controllable power switch coupled to the input side power winding; a control circuit disposed on said output side of said switch-mode power converter, the control circuit functional to provide a drive signal to activate the controllable power switch; an initial bias primary winding wound on said magnetic core; an initial bias secondary winding also wound on said magnetic core, wherein said initial bias secondary winding shares at least one magnetic path in common with said initial bias primary winding; a driver coupled to said initial bias primary winding, said driver powered by said power source, said driver configured to drive said initial bias primary winding with high frequency pulses when enabled by an enable signal before the controllable power switch is activated by the control circuit; a rectifier coupled to said initial bias secondary winding to provide rectified pulses; and a capacitor coupled to said rectifier, said capacitor configured to smooth said rectified pulses, wherein said rectifier and said capacitor are configured to provide a voltage to power said control circuit during a power converter start-up.