Thermal worst case analysis of TOP261YN 148W 85-265VAC Supply

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Attached is a universal input power supply that is designed into a U-frame of 3/32" aluminium measuring 1.5" high by 3.75" wide by 8" long. The TOP261YN is mounted midway on one side with a series 400 Sil-Pad(R) and a CLP-212G spring clip.

The design will be operating in air-conditioned environments, so the ambient air should be kept between 23 and 27 C.

The measured efficiency of this design is 85% on the 12.5V output and 82% on the 55V output. I have yet to figure out how to model this design for absolute worst case power dissipation and temperature rise. So far, a couple dozen units have been built and tested without problems, but I'd like to have a better handle on the probability of units that do have thermal shutoff issues that might develop in less than 60 minutes at full power.

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Thermal modeling of a power supply can be fairly complex.  There are lots of variables and many of them are interdependent.  It's usually easiest to do real-world testing and verify the design at it's worst case operating condition.  This is usually (but not always) going to be to be at low-line, full-load and max ambient temp.  

 

A datalogger, properly set up thermocouples and an environmental chamber will be a big help for a project like this.

 

Just out of curiousty, could you send a PDF of your PCD layout and maybe a sketch/picture of the power supply setup?

 

-The Traveler