DC to DC converter using quasi-resonance

Claim 1

A DC to DC converter for supplying direct current from a source to a load, in particular one for operating at high frequency and for feeding traveling wave tube amplifiers (TWTA), said converter comprising: a transformer having a primary circuit connectable to the source and containing a primary winding, said transformer having a secondary circuit connectable to the load and containing a secondary winding, said transformer possessing a magnetizing inductance (L m ) and a series inductance (L s ); periodic switching means (S, S 1 , S 2 ) connected in series with said primary winding in said primary circuit of said transformer, said switching means switching between a closed period when said switching means is closed and an open period when said switching means is open; an output capacitor (C o ) connected in parallel in the secondary circuit of said transformer; and an input capacitor (C in ) connected in parallel in the primary circuit of said transformer, the capacitance of said input capacitor (C in ) being much lower than the capacitance of said output capacitor (C o ); said converter possessing parasitic capacitance (C s ) including that of said primary winding and said periodic switching means, said parasitic capacitance being referrable to the primary circuit of said transformer; said input capacitor (C in ) and said series inductance (L s ) of said transformer forming a first circuit in said converter having a resonance period shorter than the on period of said periodic switching means (S, S 1 , S 2 ) and controlling the current through said periodic switching means in the on periods for reducing the current through said periodic switching means to essentially zero when switching occurs in said switching means, and said parasitic capacitance (C s ) of said converter referred to primary circuit of said transformer and said magnetizing inductance (L m ) of said transformer forming a second circuit in said converter having a resonance period shorter than the off period of said periodic switching means and controlling the voltage across said periodic switching means in the off period for reducing the voltage across said periodic switching means to zero when switching occurs in said switching means.