TopSwitch IC for AC-DC converter with a transformer that has only one primary and secondary winding
Posted by: triedgetech
on
There's a suitable AC-DC converter schematic given:
https://www.power.com/sites/default/files/PDFFiles/rdr242.pdf
However, it utilizes a transformer with secondary auxiliary winding, and I wanted to build a circuit with a transformer that only has one secondary winding, such as 7508170310.
Do you know if it will be possible to modify rdr242 schematic with TOP266VG to ensure it works with another transformer?
My needs:
Input: 90-240VAC
Output: 12V, 1A
The only way you can get the TOPSwitch to work with a two-winding transformer would be to use a non-isolated feedback setup between the primary and secondary side of the supply.If you are OK with a design that is only good for providing primary-referred power, this might be OK. If you need a design with safety isolation between primary and secondary, NOT OK.
A primary-referred bias winding is essential for use with most SMPS controllers in order to provide operating power to the controller as well as (in some cases) bias for the phototransistor side of the optocoupler for feedback.The bias winding power is especially important for designs requiring low no-load input power.
In the case of the TOPSwitch, the optocoupler output transistor not only provides the feedback signal, but also operating power for the TOPSwitch. Without this power source, there is no feedback and sustaining power for the TOPSwitch, and it will sit in autorestart mode forever...