This month, we explore the idea that in order to save power in many applications, you now have to know a lot about making power in a variety of different situations - or you can borrow knowledge about digital power from someone else.
There was a time when all an engineer had to worry about for many applications – spinning motors, lighting lights, and similar tasks – was grabbing AC power and managing it with switches, inductors and capacitors, and maybe a diode or triac.
Today, applications like hybrid vehicles, solid-state lighting, power grid management, energy generation, and more demand specialized DC power and intelligent control, usually with a microcontroller that requires software somewhere in the equation. This is often just as unfamiliar territory for the power electronics designers as the domain of power is for the digital and software designers.
The word “specialized” is important, too. There are very different approaches to DC/DC conversion (see this month’s Green in installment for two examples) depending on the voltages, currents, varying loads, efficiency required, space available, and other variables. Studying a single situation and designing an optimized power supply for it takes a lot of knowledge, but being an expert on all types of power supply situations takes a lot more.
How do designers cope with this paradox of making power efficiently to save more power in the main application efficiently? On top of that, how do designers prepare for a wide range of power needs in an optimized way that saves cost, improves IP reuse, and reduces design time?
The concept of digital power isn’t new, but it’s still developing. The folks at Texas Instruments think they have one solution to help designers get involved in more digital power applications at lower price points. Here’s the short version: A microcontroller can not only perform the actual control tasks, but it can also control the digital power subsystem. By packaging control libraries with some standard topology development kits and providing training, designers can be bootstrapped quickly into the world of digital power and get results faster.
We’ve talked before about the TI C2000 Piccolo MCU family and its Control Law Accelerator (CLA) feature, which makes complex algorithms run quite well. As it turns out, a whole bunch of digital power algorithms can be efficiently run on the CLA. TI’s Michael Wei, C2000 MCU marketing manager, listed off several algorithms including 2 pole/2 zero and 3 pole/3 zero control, two-phase interleaved power factor correction, buck single output, phase-shifted full bridge, sync driver with deadband, other functions dealing with A/D and PWM operation, and more.
Figure 1 presents a few great examples of how the MCU libraries – shown in the red blocks – can be implemented behind two completely different power topologies using just two or three pins on the MCU in the interface. The key here: It’s the same MCU and the same libraries, with two different digital power results.
The blocks are strung together using TI’s controlSUITE development environment for the C2000, and they’re all free and open source, so if designers really want to get under the hood and do more, they can.
Getting back to that two-phase interleaved power factor correction block, it’s one of the more interesting topologies because it handles a wide range of loads and higher voltages. TI has taken pieces from its portfolio and kitted them up into a High Voltage PFC Kit, shown in Figure 2.
I asked the folks at TI why they went with a different MCU module in this kit compared to some of the company’s other kits that use controlCARD, and the answer goes back to the idea that they wanted something simple with just a few interface pins for the power designers to deal with. They’ve also accounted for the isolation of the higher voltages running around this design.
TI has taken a third step, teaming up with Biricha Digital to offer a three-day class on digital power design and use of these tools for easier design execution. The class offers hands-on training and support for designers looking to dive deep into digital power.
This is one of the most comprehensive approaches to digital power I’ve seen lately, and as a 20th century mixed-signal boy, I’d like to hear your thoughts if you think it’s on target. E-mail me at firstname.lastname@example.org or tweet me at @dondingee and share your ideas.