Transformer Heating problem. IC

Posted by: svrpvarma on 06/06/2013

Hi,

I used TNY290PG for my power supply design generated using PI Design Expert. The input range is 85-265VACand the output is 12V,1.1A(max).

The problem is that the transformer is getting heated up gradually and after about 2 hrs the power is shutdown owing to excess heat in the circuit.The transformer is also designed as per the design generated from the PI Expert design.

This board was supposed to be housed in a casing which will be fixed within a wall.The heat build up happens when the board is not even housed inside a casing.

Please let me know what can be done to reduce the excess heat at the transformer. I've attached the schematic and the transformer design.

Thanks.

Files

PI_Orvito_tny290pg.pdf (156.24 KB)

Orvito Txf - Sp003_ratings.pdf (1.16 MB)

Comments

Could you send me the PI Expert design file please?

Thanks for the reply. The design file is now attached

Could you make sure that it is the transformer that is getting hot and not other components close to the transformer? Did you check the transformer leakage inductance? Maybe its some other component close to the transformer that is getting hot and eventually heating up the transformer too.

Sorry for the late reply. I was conducting more testing to make sure that the transformer is heating. Yes it is the transformer which is getting heated up. The heat is buiding up on the core. The components around transformer get heated up after some time but it is the transformer that is getting heated up first.

Based on our transformer designer's input I also increased the core size from EE19 to EE20. With the EE20, it did get heated up but worked for some more time. With EE19 the board used shutdown within10-15 minutes. With EE20, it worked for more than 1 hour and then shutdown.

It took more time to get the leakage inductance measured, as I do not have LCR meter with me. I finally got the figure from the vendor as 7.6uH with the EE20 transformer and 8uH with the EE19 transformer.

I looked at your schematic and the input bulk capacitance is too small for this application. As an initial test, try powering the board using a high-voltage DC supply and check to see if the problem persists. Also, it could be a layout issue; so try checking all your high-current switching traces.