HEATING ISSUE

Posted by: Vysakh on 07/30/2013

Hi,

Myself Vysakh and I'm a hardware design engineer in TES Electronic Solutions.

I've selected a linkswitch (LNK302D) for my new design for a low power buck application.

And I've respected the same refferance design which is provided in the datasheet except two changes(which I made for our design).

1. The refferance design is for 12V and I changed it to 16V by changing the feedback resistor.

2. I've not used a diode rectifier in betweeen the input resistor and capacitor. We are using a bridge rectifier in the input section of our design and the rectified output is directly driven to the buck input resistor RF1(mensioned in the datasheet) which I'm using a 10E 2W value.

Now I've a heating problem while loading our system.

The input resistor is heating up immediately while loading and it causes fumes also. So I'm not able to load our system for a long time and I have no idea about this heating issue. I need to fix this problem ASAP until I cannot proceed the remaing things.

So, Could you please help me for fixing this problem ?

Comments

Could you upload your schematic?

Thanks

Hi,

Please find the attached LINKSWITCH schematic.

Input to the buck converter is driven from a bridge rectifier and it will vary from 127V to 212V.

Our output voltage is set for 16V and the output capacitor which is mentioned in the schematic is a couple of 47uF/16V in which the voltage rating is comparably low. So we have tried the same circuit with a 25V rated output capacitor too.

But it doesn't make any difference in the resistor heating issue.

Expecting your valuable comment ASAP.

Regards

Vysakh

PLS make sure the voltage rating of all the input cap and output cap are high enough, and double check the polarity of these capacitors. Replace the DS4001 with UF4005. 99% sure DS4001 is a slow diode, although i can not find a datasheet to verify it.