Vmin great than 70V what drives this requirement?

Posted by: jconey@fele.com on 06/20/2014

Hello,

I'm curious what drives the 70V Vmin requirement in all the Tiny Switch datasheets and design software? I'd like to build a power supply that operates to a lower Vin value than 70V. If the 70V is only driven by the high voltage current source on the drain pin then an alternate source can be created to power the Tiny Switch and a lower than 70V input voltage supply can be created using a Tiny Switch. If some other requirement is driving that 70V minimum I'd like to know.

Also how does one search the forum postings for key words? I can't seem to figure out how to do that.

Thanks,

Comments

Hi,

Please find a design idea from Power Integration for a low input voltage design:

http://www.powerint.com/sites/default/files/PDFFiles/di152.pdf

You could use the search area:

The post in the forum will be included in the search results

Apologies my comment didn't post as expected; I will try again.

Thanks for the comment. I found and understand the design idea. However, when I use the design tool PIXI Designer 9, I get error messages when I take the Vmin below 70V. I want to know what drives that requirement. Is it simply the high voltage source on the drain pin? I would like to know what drives the requirement so I can know what other concerns to pay attention to as I pursue the lower voltage input design.

Thanks,

Hi,

Yes, the constraint is mainly from the internal shunt regulator. Like what the design idea described, you could still use it if you design some external circuits to supply the BP pin with the low input line. Concerning the PI-Xls, it will show errors because of this contraint.

You will need to do your own calculation by taking into account the minimum input voltage.