having doubt on push pull converter

[rkragunath]

plese help me understanding the push pull converter.the image below shows the topology of the converter i consider,
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In this configuration , the maximum duty cyle for each switch is <50%,so here comes the state where both swithes will be off.
Assume, when q2 is on , there is primary current comprises of load current and magnetizing current and viceversa for the q1 when it is on.

my doubt is when both switches become off, how will be the magnetising current .,

 

[rajudp]

whre is the image?

 

[WimRFP]

Hello,

Are you working on a push-pull converter with center-tapped transformer?

When you are using MOSFETs, the magnetizing current will find its way through the body diode of the MOSFET that was off.

Depending on the leakage inductance of your two windings that form the center-tapped primary, you may need a snubber network to reduce the stress on the MOSFETs.

Some explanation
When the left switch is conducting, voltage on the right switch is twice the supply voltage.

When the left switch goes off, left side voltage starts to rise, right side voltage starts to fall, when left side voltage exceeds twice supply voltage, right side will drop below zero, hence the body diode of the MOSFET will conduct, impeding further rise of left side voltage (when you have very tight coupling between the two windings that form your center-tapped winding).

This behavior also allows you to have series inductance in your load (for example for limiting dI/dt)