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Resistor inductor on inverter

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franticEB

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Hi,
i've found an old inverter schematic with an inductor and resistor on high mosfets' drain as figure below

hbridgerl.jpg

I try to reproduce it without RL circuit and mosfets become hot (80° over ambient) for conduction and switching losses as in my calculations.

Then i tried to mount the RL circuit and temperature rise on mosfets was very low (30° over ambient).

I did not understand how this circuit (RL red circle in figure) acts and how you can calculate component values.

Could you help me? I don't found anything (tutorial or application note on this subject).

This RL also allow me to increase switching frequency...

Parameters:
Fswitching=50Khz
Pout=150Wrms
 

KlausST

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Hi,

Maybe the RL prevents from high current during cross conducting of two fets.
But i don't know...

Klaus
 

ishtifar

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Hello franticEB,
Z(L) = jwL

For DC circuit, w=0 and so the resistor at the drain is actually shorted. Which is why the there is no power dissipation through the resistor and it stays cooler. Thanks.
 

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