Electrical – LTspice- Huge current spikes across MOSFETs in full-bridge inverter

full-bridgeinverterltspice

I have designed a simple full bridge inverter in LTspice. The outputs for voltage and current are as expected however I have huge current spikes across the MOSFETs which I am using as switches and are controlled by PWM. Is there a reason for these spikes? Am I missing something from the circuit?

I have tried a number of different MOSFETs and diodes and increasing the resistance of the MOSFETs reduces the spikes but not by very much.

Here is the graphs I get from LTspice, Id(M1) is the current into mosfet 1 and Is(M1) is the current out, which you can see are far too high the other graphs show the current across the resistor and inductor of the load and the voltage out.

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And here is my circuit

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Thanks in advance

Best Answer

The load is at least 5 ohms so, from a 10 volt supply it cannot take more than 2 amps and this just leaves how you are driving the MOSFETs. If you don't apply a little bit of "dead-time" when changing the PWM polarity you will get a phenomena called "shoot-through". This is because the MOSFETs don't immediately switch-off when disabling them and you can certainly get massive spikes of current when this happens.

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