Push-pull converter


Figure 6 - Push-pull converter

The simple push-pull converter circuit is shown as Figure 6. MOSFET T1 and T2 are switched on alternatively. When T1 switched on, the secondary side of transformer action forward biased diode D2 and the inductor current iL ramps up. The energy is transferred to the output circuit. On the other hand, if T2 switched on, diode D1 will be forward biases, the inductor current iL ramps up again and transfer energy to the output circuit. D3 and D4 for demagnetization purpose. The full transformer primary voltage appears across the switch that both switch off, it should be 2V1. The output voltage is twice that of the forward converter, since there is no separate inductor charging period, and the relation between output voltage Vo and source voltage V1 is:-

Vo = 2D x V1 x (Ns/Np)

where,   Vo is output voltage
             D is duty ratio
             V1 is source input
             Ns is number of secondary winding
             Np is number of primary winding