Power Management Blog | Comments and Opinions on the Power Management Engineering Sector

July 02, 2008
Tips from Texas
By Vince Biancomano

Next week we'll introduce the first installment of what I expect will be a long, well-remembered, and well-respected series of short technical articles from Texas Instruments that cover all the little facets of power management you want to know about. The Power Tips! series will essentially complement Signal Chain Basics, which is TI's contribution to Bill Schweber's Planet Analog site. If our new series is even half as successful, it'll be all I could ever hope for.

Expect to see a little bit of tutorial, a bit of "how-to," and maybe in some cases something that's akin to our Tip of the Week articles. Although at the moment we're planning the series to be a different type of technical "tip," i.e., more generic than product specific whenever possible.

I'm particularly happy to see the series coming from one of the "majors" in power management, since the IC folks up near the top tend to see it all. At the same time, it's more than a bit of effort and sacrifice for those in the semiconductor arena to write in the generic language of discrete, versus IC circuitry; after all, chips are what they do. Somehow, tho, our contributors most often deliver the goods in such a way that allows the designer to crystallize an idea with discrete parts if he/she so chooses. Although it's nice to know that if you haven't got the time and can do with a general solution that allows for a fair degree of customization, there's a chip somewhere that can do it for you.

But whichever way you look at it, the IC makers continue to constitute the core of this DesignLine, and we hope they'll continue to be as enthusiastic as they have always been. National Semiconductor in particular, with kudos also to Linear Technology and Maxim, have come through time and time again for me with some of the most widely read and useful articles you're likely to see. To be honest, we couldn't make it without them. So I'm happy to see that TI, in making the first regularly-scheduled committment to PMDL's technical section under my watch, has gone to the next level. Here's to more of the same!

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June 21, 2008
"Quad A" battery is a tickler
By Vince Biancomano

As editors, we often break some great news stories; place you, our reading audience, on the ground floor of new developments; and provide good insight on how those developments are going to impact your design task or job. But we can't break the doors down on news that may in truth have no punch line.

I'm talking about a kind of odd story I haven't seen in a good number of years. It's Energizer's initiative to expand the availability of its "Quad A" alkaline battery. More specifically, it's an AAAA battery, which by most accounts is picking up in popularity, although apparently it's not that easy now to secure from retailers. It measures 42.5 by 8.3 mm and weighs 6.5 grams. With these size and volume attributes, it's going to have a great impact on miniaturization and portable electronics, implies the initial press feed that slid across my desk two weeks ago and receded into the great beyond. The battery holds its charge for a very long time, some say. But, curiously, I haven't found that kind of allegory or other than what I'd call minimal technical info on Energizer's site. Nor have I located any other significant new info of use to you about it. Beyond that, there's very little to tell.

But Energizer says you should know about this new initiative, so here it is. Is the story all that important? I'm not sure. Because after about 10 days, I haven't located the proper authority I need to do an in-depth interview (or to paraphrase, "ten days is just about my limit on schnitzengruben"). Taking more than a few days to get a story of mine done is unusual, so having lost its timeliness the story must reduce to an announcement without any technical punch. There's a ton of questions I could be asking on the current state of the art, and getting the answers to. Such as, why would designers want to use this battery over all other alternatives? What are its specific power-density and/or energy-density advantages? Who makes competing products, and how do they rate? Has your battery been improved, or will it be, and, if so, how does it/will it outperform what's already available? What's the technology roadmap for this product, and what will be its cost profile? This is the in-depth story you need to know. But I'm judging that there's just enough info here to let you know about marketing strategy only.

As for the technical details, "son, you're on your own." Are there any details of importance? Perhaps this time I should suggest you make a call to Energizer to get the answers you need. Whatever it takes to tickle your fancy.

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May 06, 2008
Point of resistance
By Vince Biancomano

HP Labs' touted breakthrough in bringing us the fourth passive component, the "memristor", is certainly something to think about, although right now I'm a long way away from thinking about it as an advance that belongs in the Mendeleev or Newton or Maxwell class. The news, however, rather rejuvenates a related philosophical question on the power of The Calculus that I (and many) have pursued for years. And that is, how often is the derivative of a variable, versus a variable itself, the major driver for the class of equations we deal with on a day-to-day basis? And, can HP's finding now be further applied to power and power management in general? Perhaps their latest discovery adds meat to the view that the derivative is more often more fundamental in equations where we've taken something else for granted.

After all, Newton didn't really say F = ma. What he did say was that F = d (mV). And when you work that out (with respect to time t), you get F = ma + V dm/dt. Amazingly, for a while in the 50s and 60s I actually had a number of instructors who appeared to somehow believe—at least put it in their students' minds—that the second term in Newton's second law indicates that Newton may well have understood that mass could change with time in the relativistic sense. I seriously doubt Newton thought anything more than some hay could possibly fall off the wagon that he was rolling down a hill, but that's another discussion.

Electronics isn't the only area where I've seen a different look at the derivative strike in a big way. The area of radiometeorology, for instance, involves the refractive index of the atmosphere and its role in extending radio wave propagation at the VHF/UHF frequencies. Most people you run into with experience in this area will observe, and conclude, that you don't generally get enhanced propagation or ducting conditions in the wintertime because the absolute humidity is usually low, and basically is a very small term in the grand scheme of things. They assume the arithmetical differences in absolute humidity with height are too small to be concerned with, and don't bother to think about it further. That's true to a good extent, but under special circumstances you can extend the radio range even when the humidity is very low. In those cases, it's closer to the percentage change in the absolute humidity that counts.

But most people wouldn't readily recognize that, because few if any apparently bother to think about a situation where relative humidity changes greatly for a small change in absolute humidity, and that it might make a difference to look at it in that way. And know well enough, just to check it out, to take the derivative of relative humidity with height, and then plot it out. While they still would have seen the same result if they went through an analysis using absolute humidity (except for the fact that they discounted it), maybe part of the reason for avoiding relative humidity is that it isn't a direct fundamental variable (it's a function of temperature, whereas absolute humidity is not). Either way, it's a compounding of errors, and all the while the "secret" is sort of hiding in the math, waiting to be found. How many such cases of that do we have in electrical engineering? How many have we missed thus far?

In any case, I see certain parallels here with HP's announcement. Their advance seems a step beyond the kind of mental gymnastics that, in passives, made such great devices as the swinging choke, the varistor, the varactor, and yes, the FET possible. What happened is that over the course of time the technology for many of these components caught up with the math. And so HP's advance is something that apparently will yield dividends in advanced applications, and hopefully will extend deeper into power electronics. Which is, in the last reckoning, what would make the advance really noteworthy. But not the hype—given the power of mathematics—that went with it.

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March 25, 2008
Two nickels worth of battery power
By Vince Biancomano

Rechargeable nickel-zinc batteries, the complement to silver-zinc batteries we took a look at a few weeks ago, will shortly be with us. If all goes well, they'll ultimately do the job of both nickel-cadmium (NiCd) and nickel- metal-hydride (NiMH) types. But aside from the application (power tools and small vehicles), the similarities between nickel-zinc and silver-zinc are quite striking.

Much like the silver-zinc advantage that's claimed over lithium-ion, users can expect a 30 percent advantage right out of the box from NiZn over NiCd and NiMH in energy- and power-density, according to PowerGenix, the San Diego based company behind the effort. And the number of charge cycles, a problematic factor in adapting the battery's use to modern applications (primary NiZn batteries go back decades in military applications) is now several hundred.

The cost per watt-hour for the nickel-zinc might well be lower than NiMH, could compete favorably with NiCd and would be almost half the cost of lithium-ion, if you had to make that distinction. The new battery is designed to away with many of the safety and toxicity issues plaguing a battery having organic electrolytes. And they say NiZn has better low-temperature performance than NiMH.

What's more, the new batteries reportedly can be manufactured using existing NiCd and NiMH production lines and are now in high volume production. In fact, they're due to appear as a sub-C cell for a power tool next month, a D-cell at the end of the year, and before too long, a rechargeable AA battery that has 100 percent compatibility with throwaway AA batteries. So the overall value proposition (performance vs. cost. vs. toxicity) looks good.

Last but not least, they're poised to make the same step-advances in performance as NiCd and NiMH did, but in far less time. It sounds unbeatable. We'll have our interview with Dan Squiller, CEO of PowerGenix for you in short order, and let him tell you how he sees it.

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