Inrush current Protection in transformers

alfacliff

Joined Dec 13, 2013
2,458
and then you need a power supply and timer circuit for the gate and different switching so it comes up before the main supply is turnted on by the mosfet. that adds to the complexity and cost too.
 
Can you post a plot of the results of simulation showing the beginning turn on with a few cycles of the PWM drive waveform and on the same plot, the current through L1?
 

Alec_t

Joined Sep 17, 2013
14,280
I need the MOSFET M5 and resistance R5 in parallel so that during the start the current flows through the resistor R12 and the transformer .
No, you don't. Current can't flow through the transformer unless the M1 and M4 FETs are conducting, and since they are switched at 50kHz the transformer inductance will present a high impedance restricting the current.
Even if the transformer could pass current at startup the inductance would mean that the current would ramp up, like this:
 

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