LM5156H: How to realize OVP with secondary side regulation flyback topology

Kelly Bai

Part Number: LM5156H
Other Parts Discussed in Thread: LM5156

hi team,

LM5156 uses FB pin for OVP function, but if we want to use flyback with secondary side regulation topology, how can I realize OVP function?

thanks.

over 2 years ago

0 Brigitte over 2 years ago

TI__Guru 58225 points

Hello Kelly,

In general I think you would need to implement the overvoltage protection on the secondary side, but it might be possible that it works still when using the opto coupler signal on the FB node and not on the COMP pin. I personally never tested this.

Another possibility would be to use a primary side regulated flyback.

Best regards,
Brigitte

0 Kelly Bai over 2 years ago in reply to Brigitte

TI__Intellectual 1330 points

Hi Brigitte,

Do you mean connect as below way? then how to set compensation network?

+1 Brigitte over 2 years ago in reply to Kelly Bai

TI__Guru 58225 points

Hello Kelly,

Not exactly. More similar to this one: https://www.ti.com/lit/df/slur567/slur567.pdf

At the end you need to translate the Optocoupler current signal into a voltage signal to influence FB. But I do not have the details on hand how to calculate the components for LM5156.

I would recommend to use a PSR flyback.

Best regards,
Brigitte

0 Stefan Schauer over 2 years ago in reply to Brigitte

TI__Mastermind 42271 points

Hi Kelly,

I have not seen an update on this thread for the last 28days.
So I assume the issue is solved.
In this case it would be great to press the is solved button.

If there is still something open, just let me know with the new details.

Best regards,

Stefan

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LM5156H: How to realize OVP with secondary side regulation flyback topology