H bridge voltage output is not a square wave when then load is inductive

Good morning,

I came across this problem while I was simulating a DC-DC converter with simulink. I start with a 800 V constant voltage supply and then I implemented an h bridge using mosfets ( but I get the same problem using IGBTs) and I'm using as a load an inductor wich simulates the mutual inductance of the high frequency transformer. If try with no load I obtain a 800 V square wave output after the h bridge but with the inductor load the voltage it's not, I didn't expect this behaviour, because it should still obtain a square wave. What can I do?

Answer 1

[Joel Van Sickel]

This is correct behavior. You have resistance in your devices. When you first place a voltage across the inductor, it's current can't change immediately, but as it starts to cunduct more, there is a higher voltage drop across the transistor, which slightly lowers the voltage output of your inverter. As you change your switch and diode paramters, you can change slightly how this looks, but nothing is wrong with this simulation.