Energy conserving drive circuit for switched mode converter utilizing current snubber apparatus

Claim 1

A switched mode power converter comprising, in combination: transformer means; main power switch means, connected to said transformer means, for controlling conduction of primary current therethrough in accordance with an input control signal supplied thereto; and non-dissipative snubber means, connected to said transformer means and said main power switch means, for converting transformer leakage inductance energy to drive said main power switch, said non-dissipative snubber means comprising, a first capacitor C1 charged by said transformer leakage inductance energy upon each turn-OFF of said main power switch; a second layer capacitor C2 charged in increments through C1 until a given threshold charge level is reached in C2 after a plurality of ON-OFF cycles of said main power switch; an inductor connected to said C1 and C2 capacitors for limiting discharge of C1 through said main power switch means when the latter is in an ON condition; and a diode connected between C1 and C2 and poled in series-aiding direction from C1 to C2 to permit charging of C2 through C1 but to prevent discharge of C2 through C1 whereby the snubber means acts as a step-down voltage device to supply useful low voltages to said switch means in a non-dissipative fashion.