TNY 274P

Hi,

The resistor connected between the EN/UV pin and the rectified DC input, programs the undervoltage detection threshold.

This resistor can be adjusted to change the UV detection threshold as necessary. Please see page no.4 of the TinySwitch-III datasheet for details.

http://www.powerint.com/sites/default/files/product-docs/tny274-280.pdf

Regards

PI-Sarek

Hello all,

Currently, we use the TNY254 in a power supply in one of our products but we would like to migrate to the 3rd generation of the Tiny Switch. My questions are related to the snubber circuits that typically have the TNY254 and TNY274 (blue rectangles in the attached image). Why it was decided to change from serie to parallel the new circuit?

And the other one, why it decided to protect the primary side of the transformer instead of the CI?

I hope that you can help me with that.

BR

Hi Pamela Calderon,

Thank you for your interest in using Power Integrations' part.

Regarding your question.  RCD Snubber is basically use in higher power applications like what is recommended in TNY274.  You can also use the RCD snubber for TNY254 but for cost reduction at lower power requirements RC across the MOSFET can be used.  Basically both solutions are protecting the MOSFET from high drain voltage due to transformer leakage inductance.  Hopefully this answers your question.  Thank you and good luck to your project.