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I am trying to simulate a phase shifted full bridge converter in LTspice. I had already simulated it in MATLAB Simulink and obtained the desired results, but I am redoing it in LTspice to include the effects of non-ideal components.

In order to avoid the pulse generation, I imported the switching pulses datapoints from Simulink. I have thoroughly checked it and there's no issue with my switching pulses. However, the same circuit in LTspice behaves very weirdly.

This is my model:

enter image description here

First of all the current on primary is weirdly high, around 3kA where as it is 25A peak in Simulink. The current wave on primary side is as shown below:

enter image description here

This is the output DC waveform (I am expecting a stable DC of around 85V as I had obtained in Simulink.)

enter image description here

I suspect it is an issue with the transformer, but I am not able to pin-point it exactly. Any suggestions are greatly appreciated.

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  • \$\begingroup\$ Question - why does your circuit not have an output capacitor? \$\endgroup\$ Apr 3 at 7:08

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Try adding either a ground, or some 1meg to ground, to the primary side. Just because it works it doesn't mean that it should be this way. Also to the individual controlling sources. In SPICE, all nodes need a reference to ground, otherwise a floating node could have any voltage, which will cause problems for the matrix solver (what voltage should it use?). LTspice cheats a bit (tries to help users that don't know) by adding some Gmin to the floating nodes, but that doesn't mean you should accept the results, or even form a reflex out of it.

Also, the Ron for the diode might be a bit too high, try this:

.model d d ron=10m roff=10meg vfwd=0.4 vrev=200 epsilon=0.1 revepsilon=1
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