Kicking Off the New Year in Style

Jason Lomberg, North American Editor, PSD



With 2020 upon us, we hope your holiday was grand, your family was bearable, and if you were lucky enough to go to CES, the only thing you brought back is good stories (and most of your money). Welcome to another year of power engineering!

And what better way to kick off 2020 than a fundamental topic like “Power Supplies & Magnetics”?

Charged particles in motion produce magnetic fields and, when coupled with power supplies, comprise one of the quintessential areas for Power Systems Design. And with power supplies so incredibly ubiquitous – hence PSD’s existence – our contributors chose wildly different avenues of approach.

Robin Jeffery, with TDK-Lambda EMEA, discusses the mean time between failures (MTBF) as it relates to a power supply's operating life. And it turns out that MTBF is not a solid predictor of the part’s lifespan but rather the prediction of time between successive failures during normal operation.

According to Jeffery, a standard database is used that defines the failure rate of each part used in the system and “the MTBF number is then calculated, which is the inverse of the sum of all the part failure rates.” It’s also worth mentioning that “The most life-limiting component of a power supply is usually the electrolytic capacitor” and not necessarily the MTBF.

Meanwhile, Littlefuse’s Teddy To, Walt Tian, and Andy Xu cover how to avoid field failures from AC power line transients, and the answer is crowbar protection thyristors.

A crowbar circuit protects the circuit or equipment under fault condition, and it includes a thyristor with a higher rating than the devices being protected (hat tip:

Thus, “Crowbarring refers to limiting the voltage to a small value when the component’s overvoltage threshold is exceeded,” notes the Littlefuse authors. Crowbar-type devices are ideal for this purpose because they can “handle much higher surge currents since the clamp voltage is very low when the device switches to its on-state.”

Finally, I’d like to highlight a topic that’s tracking incredibly well for us – battery management systems (and batteries in general).

Over at Renesas, Niall Lyne mentions how to optimize precision cell measurement accuracy with an automotive BMS. BMS design has evolved significantly, and “the BMS IC selection today is also critical for boosting the lifespan of the battery packs, as batteries will degrade through normal operation,” Lyne says.

Here’s to another great year of power systems design!

Best Regards,

Jason Lomberg, North American Editor, PSD