Output regulation problem
Posted by: katte swaminath
on
I am Designing SMPS using TNY 274 with following specifications- input- 85-265 VAC output- 1) 5V, 0.75A 2)18V 0.06A Switch- TNY274 core- EE16 Problem- The 18 V output is varing with change in input voltage .It goes to more than 29 V when input volage is 200V I have Attached design file
Files
| Attachment | Size |
|---|---|
| SMPS.uds | 239.5 KB |
To improve the regulation of your 18 V output, you need to add a pre-load to the 18Voutput and/or add a few ohms resistor from pin 7 of transformer to Anode of D7.
The preload will consume some power and reduce your output voltage.
The resistance is series with D7 will reduce your leakage inductance spike and reduce your VOUT.
Another way is to add a zener or a zener in series with a resistor at the output. This circuit will clamp your output voltage and prevent the 18 Vo output to go too high.