TNY266 problems

Posted by: ras123 on 10/28/2008

Hi, I have designed a DC adapter using PI Expert 7, with the following specifications using TNY266 (DIP Package) I/P:- 120 to 265 V O/P:- 2.4 V / 2A I followed the design except I used UF4007 instead of FR106 (DB). Without any load it gives correct o/p voltage, but when I loaded output with a 10 Ohm resistor, the circuit burn off (i.e TNY266 shorted). The same repeated twice, so can anybody help me to find out the problem? Please see the design attached with this post.

Files

PIDesign.pdf (70.87 KB)

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Can you attach your design schematic and your layout file? The PI Expert design looks fine and its ok to substitute a UF4007 in place of the FR106 diode for DB.
Also please measure how much leakage you have in your circuit and let me know.

Hi, I followed the same schematics as per the PI Expert design attached. Is the PCB too critical? Can you tell me possible reason for breakdown? Initially I loaded 10 Ohm without the voltage control (i.e. with out 1.4 Volt Zener diode), and it works fine. When I regulated the o/p voltage to 2.4 Volt it also works fine, but while switch on with load (10 Ohm) breakdown occurs. Is any danger to design such low voltage SMPS?

No there is no danger to designing for low powers...
From the PI Expert design files I dont see any problems. I may be able to spot something after looking at your schematic and layout...
maybe you have big loop areas, maybe you have too little heatsinking maybe you connected some parts of the circuit backwards (namely the clamp) I cant tell without looking at your schematic and layout

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