277VAC
Posted by: willreed
on
We would like to use the LNK304 in a buck converter outputing 15V at 70mA. Our input voltage can range from 90VAC to 277VAC +10%. The application note shows an input of 265VAC max. Is there a modification we should make to the standard buck circuit to allow for 277VAC use?
Also, what is the minimum load required for the 70mA version?
Thank you very much,
Will
For a buck converter, the reason because the maximum input voltage is 265 has to do that universal voltage range is usually from 85 to 265VAC.
I think it is very possible the design works with 277VAC. Juts to be fully sure, check the DRAIN to SOURCE voltage of the controller with 277VAC.
Check it in steady state, start up, transient load and overload conditions. You should never exceed 700V. In order to compensate for thermal variations, it is good idea never have more than 650 V under any circumstance.
Do the same for all the diodes. Check they voltage does not exceed they MAX reverse voltage.
For the minimum load it depends on your allowed tolerance for the output voltage.
You can gradually reduce the output load and see when the output voltage goes beyond your specific MAX VOUT. At that point you calculate the needed resistance to be added as a preload.