of one switch and the closing of the other to prevent 34 shoot through 34 and assure a zero voltage switching first top switch s22 and first bottom switch s23 have their duty cycle or phase shift with reference to the common switches controlled by a pwm controller not shown which monitors the conditions of output voltage v o1 and varies the duty cycle or phase shift of first top switch s22 and first bottom switch s23 to maintain a tightly regulated output voltage second input subcircuit 58 through n th input subcircuit 64 operate just as described with first input subcircuit 56 just as described above second input subcircuit 58 uses second top switch s24 and second bottom switch s25 in conjunction with common top switch s20 and common bottom switch s21 to control the voltage across second primary winding tp21 additionally output circuits 62 with secondary winding ts21 coupled to second primary winding tp21 and n th output circuit 66 with secondary winding ts n coupled to n th primary winding tp n operate just as described above with respect to output circuit 60 to produce output voltage v o2 and output voltage v on respectively as illustrated by n th input subcircuit 64 with switches san and sab and primary winding tp n.