Feedback loop for TOPswitch-HX

Posted by: treez on 07/09/2023

Hi,

In the attached AN-57, do you know what is the "K(TL431)" value? (page 14).....the open loop gain of the TL431.

We are trying to stabilise a 20W TOP256GN Flyback, and need to know the K(TL431) so we can calculate the feedback bodes.

Files

an57.pdf (3.25 MB)

Comments

As such.... i assume that by the "open loop gain of the TL431", the AN-57 means Z(FB)/Z(in) of the TL431 circuit in Fig 5, page 4 of the AN-57 Application note.....

where:

Z(FB) = 1/(2.pi.f.CF1)

and

Z(IN) = RF2

?

(The AN-57 App Note is attached in the Top Post here)

Hi,

Thank you for showing interest in Power Integrations' products.

The open-loop gain referred to in AN-57 Page14 is the gain of the TL431 itself.

Please refer to the datasheet of the specific TL431 device you are using in your design.

Typically, manufacturers provide an open-loop voltage gain vs frequency chart in their datasheets.