With so many power discretes to choose from, how can you be sure you’re using the right one? The following suggestions can help you realize the “gain” of truly energy-efficient choices without enduring the “pain” of comparing performance claims.

Understand Your Market

Different regions have different requirements for power consumption, so make sure you know what’s expected. Inefficient power discretes could, ultimately, bar your product from being sold.

Look Beyond Parameter Tables

Overall efficiency is the combination of many factors. Relying on a single parameter, like on-resistance or saturation voltage, may not tell the whole story. Review the entire datasheet in detail, keeping relative peak efficiencies in mind.

Narrow Your Focus

Know when to choose a MOSFET and when to use an IGBT instead. If your application uses high voltage (≥ 300 V) and high current, with a switching frequency between 3 and 100 kHz, then an IGBT is probably best.

Test it Yourself

Since different vendors use different test conditions and publish different electrical data, be sure to test discretes in the target application. With MOSFETs, two of the most important waveforms to look at are drain-to-source resistance [RDS(ON)] and total gate charge (Qg). They give the most comprehensive view of conduction and switching losses. For IGBTs, look at the collector-to-emitter saturation voltage [VCE(sat)], the turn-on switching loss (EON), and the turn-off switching loss (EOFF).

Understand the Role of Packaging

Some packages are more efficient than others, so it’s a good idea to compare the details. Newer packages may reduce the need for lossy circuits or for managing device overstress and electromagnetic interference (EMI). They may also make the layout more compact or help the PCB spread heat.

To get the details on these recommendations, download the full six-page Tech Brief.


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High Level: http://www.fairchildsemi.com/products/discretes/igbts/