respectively external inductors l 20 and l 30 have the same value for leakage inductance as l 4 from fig1 a the rest of the circuitry is the same as in fig1 a an advantage of the embodiment in fig1 c as compared to that of fig1 a is that the drive transformer is simpler with only four windings versus five on the other hand two extra components inductances l 20 and l 30 are needed in applications in which a multilayer pcb is used the drive transformer t 1 from fig1 a may be preferable since it eliminates the need for inductances l 20 and l 30 and their associated cost and space on the pcb operations of the fig1 a and 1c circuits are very similar the salient waveforms for operational understanding of the circuit from fig1 a and 1b are provided in fig2 for simplicity it is assumed that all primary switches q 10 q 20 q 30 and q 40 are identical and that synchronous rectifiers s 1 and s 2 are identical as well as are leakage inductances l 1 l 2 and l 4 it should be noted that the invention is not limited to these assumptions also for simplicity it is assumed that leakage inductance l 5 u2248 0 in these waveforms t d1 u2014 time between turning off synchronous rectifier s 2 and turning on.