Pulse switching tandem flyback voltage converter

Abstract

The power supply converts a high wide ranging AC or DC voltage into a low regulated output voltage. Input rectifiers and filters are provided to rectify and filter the AC and to pass the DC voltage. An integrated switching circuit converts the filtered DC voltage into brief pulses whose duty cycle is varied by a first regulator as an inverse function of the filtered DC voltage. The pulses are employed to produce a DC output voltage by a tandem flyback circuit connected to the filtered DC voltage and comprising an electronic switch connected in series with a first inductor across the filtered voltage and having a gate supplied with the pulses, a capacitor and a first diode connected in series across the first inductor for receiving the discharge thereof, a second inductor and a second diode connected in series with the electronic switch and the capacitor whereby the capacitor is discharged through the second inductor, and output rectifier and a filter connected across the second inductor to produce a filtered DC output, a secondary winding coupled to the second inductor and connected through a rectifier and a filter to supply DC operating voltage to the integrated switching circuit during normal operation, and a diode and a resister connected between the filtered high voltage DC and the integrated switching circuit to supply operating power thereto during start-up.