TOP257PN
Hello Sir,
Attached is the circuit. Input voltage range is 250 VAC to 500 VAC. First i loaded with 3.5W resistive load there is no problem, it was working fine. Then i changed the load to 6W then the clamp circuit(as per ciruit attached) blows around 300 VAC. I changed the clamp ciruit to RCD(100K, 1nF/1kV, UF4007). Suddenly around 312 VAC bobbin got some problem. when i replace with new bobbin again starts working. but same thing is happening after 300 VAC. I checked for the continuity of the windings, seems to be perfect. but am not able to fix what happened to the bobbin. pls help me in this issue.
Comments
Hello sir,
I have attached the Xls file. I am not able to conclude what happened to transformer. when i replace it with new one circuit is working. pls help
If replacing the transformer solved the issue, then this indicates that the leakage inductance on this transformer is too high.
Also another thing about your design - I see that you have specified a KP of 0.6 and it returns you a primary inductance of almost 7 mH! Thats too high. That results in too many primary turns and therefore huge leakage inductance.
I would change KP to a slightly higher value - around 0.8 or something.
Some more informatin is needed to ascertain the root cause of this problem.
What is the VOR for this design? What is the primary inductance and the leakage inductance of this transformer. I suspect you have very high leakage. Do you have a PI expert or PIXls design file? what do you mean exactly by the bobbin had some problem?