Where there’s great people and great teams, you’ll find Bob White
There’s a lot to be said about how being around great people can have a positive, nurturing influence on a career. When you talk to Bob White, who has been very instrumental in creating and advancing the PMBus standard and who continues to be a very prolific speaker at power-related events, he’s quick to praise the people he met along the way from his days as an Air Force electronics technician working on microwave and communications equipment and throughout 30 years as a power conversion expert.
Following his service in the Air Force, Bob White wanted to do more than just study the theories being taught in the science classes and chose electrical engineering. His bachelor’s thesis analyzing the fields in a superconducting alternator led him to the Power Lab at MIT studying under distinguished professor John Kassakian who later became director of the MIT Laboratory for Electromagnetic and Electronic Systems. In a special graduate power electronics seminar, he worked alongside Neil Rassmussen and Manny Landsman — who would later co-found American Power Conversion, and Marty Schlecht who founded SynQor — on electric vehicle design, which was largely conceptual for the late 1970s. The project captured Bob’s interest, so he embarked down the power conversion path and went to work at GE Power Systems’ Business Unit between semesters.
While the company’s expectations may not have been high for a student providing summer help, his work was quite innovative for the time. “I actually gave them several patent disclosures and made a little 48 V to +/-15 V converter which I would call today a primary side regulated peak current mode constant off time converter using only a 339 quad comparator as the only IC. I also used a MOSFET, which was kind of outrageous.”
Bob spent a good part of his career at Digital Equipment Corporation where he, once again, was part of a great team and had very successful projects including designing the company’s first switching power supply to power a hard disk.
“I lucked into a really good group, a really good project and a really good boss. He just kind of gave me the project and got out of my way. In those days, a desktop power supply’s densities were limited by the box design, but he was able to produce a unit for 60 cents/watt for a triple output 208 W supply with an AC fan and a complex power sequencing circuit interfaced to the computer board. Teaming with a great technician, “We got the noise down low enough, and we also had a very innovative input voltage switching circuit.”
Bob is perhaps best known for his work in drafting the PMBus standard, which came about during his time at Artesyn Technologies. While working toward a protocol for digital control systems, Bob realized that other vendors were going to do things their own way no matter what bus Artesyn chose or however the 1s and 0s are patterned for “On” or “Off”. He approached his manager, Trey Burns, and division president, Ken Blake, with the idea of developing an open standard for digital power management. Trey and Ken got it right away and asked Todd Hendrix, vice president of marketing, to reach out to power supply and power IC companies. It took Todd just a few weeks to form the initial PMBus consortium. With IC vendors and power supply vendors cooperating, lending their expertise, and customer input to the project they were able to release the first draft in a matter of only six months. Equally amazing was the foresight of the original working group which, in addition to Bob, included David Freeman from Texas Instruments, Ken Fernald of Zilker Labs, Keith Curtis from Microchip Technology and others. Ten years after that first draft, PMBus is only up to Revision 1.3!
So what can we expect from PMBus Rev. 1.3?
Given its few revisions over the last 10 years, the basic PMBus specifications will undergo some fine tuning. The big change is the addition of Part III of the specification, which describes a new, fast, interface between a device like a large ASIC or FPGA and the converters powering it. This new part of PMBus, called the AVSBus, helps the ASICs, FPGAs and other processors save energy at the system level in real time by sending instructions to the POL to adjust the supply voltage. “The ASIC talks to its two or three power converters. If an ASIC or an FPGA wants to cycle through power states, it can do that. It can tell its power source ‘OK I’m going idle, shut down to 0.8 V for a while or something,’ and do that fast enough to make a real difference in energy savings.” Bob sees AVSBus as a “big leap forward” in the future of PMBus.
Bob points to the very high efficiency of today’s AC-DC power supplies as the reason why today’s focus on power savings has moved to the system level where unused components are turned off. In order to do so effectively, however, the switching must happen superfast. Even 100 milliseconds is too long to make a difference. In addition to his consulting work, Bob is a PhD candidate at the University of Colorado and he, along with his sponsor Sarda Technologies, is trying to bring power conversion well into the RF region. They’re hoping to make POL converters with extremely high frequencies — into the megahertz — that will hopefully bring about meaningful reductions in power consumption at the system level. “Today we can turn the voltage down which saves some energy but it’s really hard to turn things all the way off and turn them back on kind of in real time,” he explains. “We’re already at 94 to 95 percent efficiency on the AC/DC converters, and we’re well into the 90s on POLs. It’s hard to push that much further.”
Another important development Bob is expecting to impact digital power will come from the emerging wide bandgap compound semiconductor devices — GaN and SiCs. In particular, Bob is optimistic about GaN’s potential for higher voltage operation. “When I started in 1980 at Digital, I had already used a MOSFET but we used all bipolars. By 1985 we had pretty much switched to MOSFET,” he remembers. “GaN feels a lot like 1980.” Bob believes GaN’s role in the commercial power supply space is going to be very important in the next five years. Further on the horizon, Bob is keeping an eye on the advanced nonlinear and digital control. He notes that there’s so much computational power that techniques, such as automatic loop compensation, coming from companies like Powervation, may provide benefits beyond what are offered from the standard type 3 op amp-based compensators of today.
Today, Bob White continues to work on his thesis and provide consulting services through his company, Embedded Power Labs. If there’s one bit of advice Bob most enthusiastically offers newer engineers, it is to get involved and network themselves. “It’s not just sitting at your desk with your Mathcad and your scope, but getting to know the people.” For instance, Bob is well-known through his involvement with the IEEE and its various committees, his chairmanship of the APEC Conference and co-chairmanship of the Power Sources Manufacturers Association’s Technology Roadmap, and presentations at many seminars. Bob counts anything that connects a broad range of people and interests as being very important to a successful and satisfying career. “I think it’s so easy to get narrowly focused on what you’re doing you lose track of the fact that it’s a big world out there. I encourage people to get involved in the professional societies, volunteer, write papers, give seminars ... get out there and make the connections because that’s going to be crucial to your career.” In college, Bob had a general interest in science. But by meeting up with great people, he developed a passion for power electronics that led to constant involvement in very interesting projects that continually places him on the cutting edge of power technology.