Transfer function of full bridge inverter and LLC circuit.

Hello everyone, I'm new at deriving transfer function and trying to derive the same for following circuit. Circuit contains full bridge inverter circuit with input as 50VDC (50% Duty cycle used to drive mosfets). output of inverter circuit is given to LLC circuit. I've derived transfer function of individual LLC circuit but not able derive for full bridge inverter. Can any one describe how to derive transfer function of full bridge inverter circuit or combine transfer function of full bridge and LLC circuit ?

Note : Input is 50Vdc supply and output of combine circuit is voltage across 100E resistor.

[SALAH alatai]

have you got it ? if yes pls share it. thanks

Answer 1

[Joel Van Sickel]

As there are switching devices, you either need to use averaging techniques to extract it analytically (do it by hand) or you can solve it in the frequency domain:

https://www.mathworks.com/company/newsletters/articles/estimating-the-frequency-response-of-a-power-electronics-model.html

This will give you the frequency response, and you can choose the correct order transfer function and using system identification to fit a transfer function to that frequency response. (start with 3rd order as there are 2 inductors and 1 capacitor).

Regards,

Joel

[Stanley Ugwuoti]

Thank you for this article embedded in your answer. I'm guessing that this approach is also applicable to variable frequency drives, only with a difference that it contains cascaded AC-DC-AC stages.

[Joel Van Sickel]

yes, you an use the same approach for any converter regardless of topology.