Keeping it cool! Heatsinks: key parts of (power) electronics’ thermal household

Keeping it cool! Heatsinks: key parts of (power) electronics’ thermal household Door: KWx

Keeping it cool! Heatsinks: key parts of (power) electronics’ thermal household

With over 40 years of experience in #powerelectronics#KWx veteran Ben Tabak has seen probably over a thousand of different designs of electrical systems. This week Ben blogs about the underestimation of system cooling and the important role of choosing and applying the correct heatsink. 

The underestimation of system cooling

To me it has become clear that in the design of (power) electronics systems the importance of thermal household and choosing the correct heatsink is sometimes underestimated. Often, the designing engineer mainly focusses on choosing the right semiconductors and the control electronics.

But be aware, the thermal household of the system including the proper heatsink, is at least equally important!

A well designed, compact but reliable system asks for a perfect harmony of power dissipators, and the precautions taken to “keep it cool”!

Cooling principles

First of all, The cooling of the electrical system must assure that the maximum allowed junction temperature of the semiconductors and other components that dissipate heat, under worst case conditions, will never exceed their specified maximum. Even better: stay well under it as to secure a safety margin.

Calculating maximum temperatures

Calculating temperatures is not much magic if all required parameters are well defined.

The dissipated power, times the summary of the serial-connected thermal resistances lead to the temperature jump (ΔT). Adding this to the maximum ambient temperature will indicate the maximum (junction-) temperature.

The lifetime of components strongly depends on their temperatures and even more on the temperature variation. This especially applies to systems that must control load power that strongly varies in time.

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