We have designed 13V,0.35A SMPS using TNY-284 IC and PI Expert Design Tools.
Input Voltage Range: 65VAC-300VAC
Output Voltage : 13V
Output Max Current: 350mA
We have tested the design for 30 samples and everything is ok. But sometimes the 10 Ω/3W fusible resistor burns after switch is turned on. No other components damage and if we replaced the burned fusible resistor with a new one it works again.
We have tried to find the reasons and noted some differences(have to make according to availability of component) between PI expert Design Tools and our design.
Here I have attached the PI Expert suggested design, our schematics and PCB layout and noted differences between them.
So, what can be the reasons behind this problem?