HiperTFS Two transistor Forward...producing the Bode plots for feedback loop

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Hello,
We wish to do a HiperTFS two transistor forward. We appreciate it is Voltage Mode
Please can you direct to where the transfer function is to be found for the Error amplifier and Modulator?
(we are using TL431 feedback, its 390Vin and 48V,5A out)
Kind Regards,

The transfer function for the TFS FB pin is shown on page 9 of the data sheet (Figure 7). There is also an active duty cycle clamp that reduces the max duty cycle according to input voltage, this is also shown in Figure 7.

Thanks,
Actually we seek the expresssion for the transfer function of the error amplifier and modulator of any of your DER designs?
Please help us, since we wish to make out the bode plots. We know the transfer function for a voltage mode 2 tran forward power stage, but need to know the transfer function for eg a TL431 based feedback type error amplifier feeding back into the HiperTFS.
P[lease advise on this?

We need to be able to make out the bode plots before doing the design with the brilliant HiprTFS.

Application note AN-57 (available on the PI web site) might be of some help, though it deals with the TOP-GX rather than the TFS.. Also, there is extensive documentation available on the web regarding loop characteristics of the TL431 used as reference/error amplifier for SMPS, mostly from the companies who make them. Five minutes of web search gets you a lot of references.
Your situation is simplified as the TFS control pin responds directly to the current output of the optocoupler.

Thanks, yes i have the transfer function for TL431/Opto based error amplifiers, its available in the Basso Book, and is no problem. The query is with the modulator, the bit thats inside the HiperTFS.....are you implying that the modulator transfer function is unity? With a voltage mode controller, the modulator transfer function usually depends in some way on the sawtooth waveform amplitude inside the controller.

The TFS-2 data sheet states the duty cycle as a function of current drawn from the FB pin. The overall gain will then depend on the input voltage and XFMR turns ratio.