Regulated transistorized DC to DC converter and parallel operation of plurality of converters

A DC to DC converter comprising a control circuit energizable by a source of DC current and having a first pair of output terminals connected in series with said source of DC current and one half of a center-tapped primary winding of a first transformer and a second pair of output terminals connected in series with said source of DC current and the other half of said center-tapped primary winding, said control circuit producing pulses alternately in the two halves of the center-tapped primary winding, said first transformer having a center-tapped secondary winding with each half of said secondary winding being connected to electronic switching means for causing pulses of current to flow from said source of DC current alternately in two halves of a center-tapped primary winding of a second transformer, said second transformer having a secondary winding connected to a full wave rectifier having an output connected to an output filter for providing a smooth DC output from the converter, each of said pairs of output terminals being fed by an output transistor fed, in turn, by a driver transistor having an input fed by substantially square wave pulses and across which is connected a capacitor so that the pulses appearing at the output terminals of the control circuit are trapezoidal shaped and thus have substantially no harmonics of radio frequency, said control circuit comprising a unijunction oscillator driving a flip-flop and a one-shot multivibrator and feeding a first input of each of two three-input AND gates, said flip-flop having one output feeding a second input of one of said AND gates and a second output feeding a second input of the other of said AND gates and said one-shot multivibrator having a pulse output feeding a third input of each of said AND gates, each AND gate being associated with a different one of the pairs of outputs of the control circuit and, when enabled, resulting in current flow from its associated pair of output terminals, said converter further comprising feedback means responsive to current flow in the output of the converter for regulating the pulse duration of the one-shot multivibrator and hence the duration of time that the AND gates are enabled, said unijunction oscillator comprising a programmable unijunction transistor and said control circuit comprising a sync. frequency line, means responsive to firing of the programmable unijunction transistor for producing a pulse on the sync. frequency line and means responsive to reception of a pulse on the sync. frequency line for firing the programmable unijunction transistor.