PMP22764: Zenor diode in flyback application (D7)

Gary Teng

Part Number: PMP22764
Other Parts Discussed in Thread: LM51551

Tool/software:

Hi Sir,

My customer is designing LM51551 in their isolated flyback circuit. They want to confirm what's the function about D7 in design? And is it possible to change it to 5.6V ziner diode?

Thanks and regards,

Gary Teng

10 months ago

0 Gary Teng 10 months ago

Genius 6000 points

Hi Sir,

Any comment about that?

Regards,

Gary

0 Carlos Rodriguez 10 months ago

TI__Prodigy 170 points

Hey Gary,

The function of D7 is to regulate the voltage source that provides current for the COMP pin through R18. This comes from VCC that is a higher voltage and can vary significantly.

You can increase the Zener diode to 5.6V but increase R18 to 2.74k to keep the current being drawn similar to what we now have with the 5.1V Zener.

Regards,

Carlos

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PMP22764: Zenor diode in flyback application (D7)