Abstract: A regulation technique for regulating at least one auxiliary output of a power supply having a regulated main output. When the auxiliary output reaches a first or a second predetermined value, the feedback circuit of the power supply is adjusted such that the auxiliary output is substantially maintained within the first and second predetermined values.

Abstract: Improved start-up circuitry is disclosed for a switching power supply including transformer inverting circuitry that is responsive to a pulse-width-modulated gating signal for providing a DC output voltage from an AC input voltage. The switching power supply further includes comparing circuitry for comparing the DC output voltage to a reference voltage and providing an error signal proportional to the difference therebetween, and control circuitry for pulse-width modulating the gating signal in response to the error signal. After initial AC power turn-on or after subsequent AC power interruptions, the start-up circuitry momentarily enables the control circuitry to pulse-width modulate the gating signal at a maximum duty cycle. The gating signal is otherwise pulse-width modulated at a minimum duty cycle by the control circuitry until the error signal is established.