It’s not very often that folks get excited about a power supply. After all, you don’t see commercials of people showing off the latest power-conversion technologies, like you do for the latest smart phone or tablet. But for those of us who work with the technologies thatfuel everythingdigital (really everything electronic), some interesting trends are really very exciting.
Digital control has been making waves in the world of power supplies for more than two decades. During its onset, people from all over the power supply industry asked questions like, “What does a digitally controlled power supply do that an analog power supply can’t?” While there still may be a few wondering about this, the reality is that ship has sailed. There are a multitude of innovative companies using digital power to bring efficiency increases, field upgradability, fault diagnostics, etc. To this end, in the coming years the adoption of digital power is projected to pass analog control in many significant markets. For it to do so effectively, I fundamentally believe that we are going to need a different kindof digital controller to step up to the plate.
OK, so what do I mean by that? Essentially, over the past decade we’ve seen a huge push for higher efficiency. Commercial power supplies have made amazing improvements in this regard. However, I think the next big trend is going to be miniaturization. We’re never going to see a runway model showcasing the latest digital power technology, but if the power supply becomes invisible, stand back and watch how excited people get. Now invisible is a tall order; the last time I checked, that technology wasn’t yet available. J But there are things we can do to make the technology less intrusive.
Fundamentally, we need to raise the switching frequency. At this point most of you are probably saying, “Duh!” While in one sense this is obvious, it’s worth noting that many things are coming together to create a perfect storm to usher this requirement onto center stage now. For example, 97% efficient AC-DC power supplies are commercially available, there are new cost-effective switch technology capable of higher switching frequencies and lower loss (i.e., gallium nitride [GaN]), and process technology advances now enable the integration of magnetics to unimaginably small sizes. To keep up with these trends, we need a new kind of digital controller. We need a digital controller that has the horsepower under the hood to not only keep pace with these advances, but to actually accelerate them.
It’s not hard to see how a conventional microprocessor could have trouble with this. This Institute of Electrical and Electronics Engineers (IEEE) publication[1], presents a straightforward analysis that shows that a 60MHz processor is computing-resource challenged to achieve a 20kHz bandwidth on a 200kHz switching-frequency power supply! If we’re struggling to keep up at 200kHz, we are going to need a revolutionary new architecture if the switching frequency is 2MHz or even 20MHz.
TI’s UCD line of digital controllers, such as the award-winning UCD3138 digital power controller, has the precise recipe that the industry needs. Instead of putting the burden of real-time control and protection on a high-end microcontroller (MCU), these controllers introduce application-specific state machines that are capable of closing a 2MHz control loop without any processing time required from the MCU[2]. The controller also has a fault management systemthat can take action in just over 100ns to halt the propagation of a fault without any processor intervention. This leaves the processor available for high-bandwidth communication or other process-intensive housekeeping tasks.
In concert with the fault management system, these state machines essentially create exactly what the industry needs to thrive in thisperfect storm: a digital controller with a boatload of processing power strategically placed exactly where it’s needed most. Or if you prefer, a digital controller on steroids.
Additional Resources
- View TI’s full digital power portfolio
- Read: Implementing transition-mode control using UCD3138 devices
- Read: It is not just a PFC controller, it is also a power meter
References and Notes
[1] Cho, Je-Hyung; Hyun-Wook Seong; Shin-Myung Jung; Jin-Sik Park; Gun-Woo Moon; Myung-Joong Youn. “Implementation of digitally controlled phase shift full bridge converter for server power supply.” Energy Conversion Congress and Exposition (ECCE), 2010 IEEE, pp. 802, 809, 12-16 Sept. 2010.