TinySwitch-4 (TNY286DG) dropped output voltage.
Posted by: elnino1947 on Sat, 05/29/2021
- Hello i am using TinySwitch-4(TNY286DG) for a power supply application target for input range of 85V to 500V AC 45Hz to 65Hz. With two isolated 5V outputs, the regulated output(where optocoupler feedback is present), rated current is 1.5A. I am also using FET stacking to increase my operating voltage beyond max drain voltage as recommended.
- With no load or light load conditions the output performs with satisfactory output.
- With around 80% to 100% (full load condition) my output voltage drops to about 4V and sometimes down to 3V(depends on load) at certain voltage ranges namely from about 100V to 200V range, below 100V and above 200V the performance is again improved , and again at around 320V the output dips a bit ( some ripples)(not much of a concern in my application).
- What's interesting to note that when the output voltage dropped(3v and 4v condition) I removed the optocoupler series resistor(R23) thus removing feedback and yet no change was observed (the output voltage should have risen exponentially here).
- This seems some kind of situation where the tiny switch is somehow saturated hence my first conclusion was the input voltage isn't enough but then the output is completely fine below 100V which ruled out this theory.
- I have attached some waveforms and the schematic for the same below, the schematic was generated using PI expert and FET stacking was added manually to increase operation range
|Output 4V input somewhere between 100V to 200V(1).jpg||92.44 KB|
|Output 4V input somewhere between 100V to 200V.jpg||239.28 KB|
|Output 5v input above 250V.jpg||264.19 KB|