DC to DC converter with self-starting flyback oscillator

Claim 1

A DC to DC converter circuit for producing a regulated DC output voltage from an unregulated supply comprising: a flyback oscillator including a transistor having an output circuit connectable across the unregulated supply to periodically conduct current therefrom; output circuit means; transformer means for coupling the output circuit of said oscillator transistor to the output circuit means for receiving and storing eletrical energy therefrom during the interval between said conductivity periods and in amounts which vary with the conductivity period of the oscillator transistor, said transformer means comprising a primary winding in series with the output circuit of the oscillator transistor and a secondary winding in said output circuit means, said primary and secondary windings being magnetically linked; a variable impedance control transistor connected to the input circuit of the oscillator transistor to vary the conductivity period thereof; means for establishing a reference voltage; comparator means connected between the output circuit means, the reference means, and the input circuit of the control transistor to vary the conductivity period according to the energy stored in the output circuit means; and feedback means connected in series with the secondary winding and the output circuit of the control transistor to provide, when connected across said supply, a starting current path for said oscillator transistor.