Hello All,
I'm actually working on stability analysis of a multi-outputs flyback controlled with UCC28740 and the feedback was obtained by a type 2 compensation network using Shunt regulator (TL432) and an optocoupler.
In order to complete this study, i'm needing the transfer function of the UCC28740 internal Modulator and of a multiple output flyback converter.
If you could help me with this topic, it would be much appreciated.
Thank you
Yassine
Hello Yassine,
Thank you for your interest in the UCC28740 flyback controller.
Here is a presentation that covers the transfer function for a single output design:
UCC28740 Feedback Loop & Compensation Design.pptx
This presentation is in the native .pptx format because it uses "animation" to clarify some of the concepts. These would get lost if converted to .pdf. So you have to view it in presentation mode, too, because the animation doesn't work when the file is opened in edit mode.
For multiple outputs, this is the only help file that I could find on the topic.
For multi-output designs, we generally refer (by turns-ratio conversion) the parameters of all the outputs to a single dominant output and design it from there. I imagine perturbations on other outputs must be referred to the one that is being regulated.
I hope this helps you with your analysis.
Regards,
Ulrich
Hello Ulrich,
Thank you for the fast and clear response.
I started by deriving the open loop transfer function for all 4 modulation regions. I have some points that needs clarification:
- Slide 11 : For the modulator + Plant Transfer function . The Ip/Ipmax ratio is clear for the FM control mode, but not so much for the AM region. and the Vcs_max should be the image of Ipmax on the CS pin?
- Slide 12 : is neglecting the ESR value of the output capacitance could influence the results.
thank you for the support
