Author Topic: DCDC Push Pull Feedback Compensation calculation  (Read 554 times)

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Offline Echo88Topic starter

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DCDC Push Pull Feedback Compensation calculation
« on: July 07, 2020, 01:55:25 pm »
Is there a simulation tool/calculator/easy way to calculate the needed capacitor/resistor-values which are needed to get a correct feedback compensation in Push-Pull DCDC-topologies?
I found the following document which details the usage of the often used TL431 in the feedback path, but failed to find the described design tool: https://www.onsemi.com/pub/Collateral/TND381-D.PDF
https://www.poweresim.com seems to be a very good tool and also calculates the (quite convoluted) TL431-feedback RC-network, but i cant reproduce the poweresim-results in LTSpice with, for example, an LT1683. Also it seems to only have one optocoupler available and diodes like "PED2A100" which im unable to find datasheets for.

Anyway: Is it absolutely necessary for me to learn poles/zero-calculation before being able to simulate push pull DCDC with well working feedback?
 

Offline David Hess

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Re: DCDC Push Pull Feedback Compensation calculation
« Reply #1 on: July 07, 2020, 08:18:35 pm »
You can find the values empirically.  Or you can use a Bode plot to find the values.  Sometimes where I have unknowns, I have found the values empirically and then used them to work back to a Bode plot of the open loop response which allowed me to calculate the unknown values.
 


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