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Piezoelectric Transformers
behoward writes "Tired of those big honking power adapters needed for all your portable toys? Me too! So far the best solution I've seen is the AC adapter for my G4 Powerbook, a sleek combo yoyo/flying saucer; but while it looks good on the desktop, it still makes too big of a bulge in my case when I travel. Now engineers at Penn State are working on a real solution. Hope Apple gets this technology in place in time for the G5 Powerbook."
That's nice and all, but what about our pets (cats, dogs, etc)? Are they going to be driven nuts by a high pitched whine?
The article mentions plans to develop 220V. versions. That seems to imply they cannot make adapters taking any voltage between 90 and 240 volts, like the current notebook adapters.
In other words, it would be a big step backwards if you need to carry around two adapters with your notebook!
Or can these be made universal like the current standard adapters?
I for one am looking forward to seeing this technology develop, and let me tell you this is signifigant! As an electrical engineer that builds transmitters for an income, I can tell you just how signifigant.
There are basically two ways to transform voltage right now. The first way is to use an electromagnetic transformer, which is a very bulky solution. A 2A 125v-24v power transformer can be the size of my fist, and will generate a lot of heat at even half that amperage max.
The second way is to use a type of switching power supply that basically uses a step-up transformer to convert the voltage and then filters it down through a series of circuits. This is the system used by most power supplies nowadays because it is cheaper and smaller, but there are many disadvantages to this method as well, most importantly SAFETY. The voltages that run through these can be thousands of volts, and also the circuits can be complicated (it's easier with a transformer, because all you need is a recitifer bridge and a filter capacitor).
This method, on the other hand, uses a peizoelectric method, which (if I'm understanding it correctly) is very cool. If you need an analogy, this method basically acts like a quartz crystal does, like in radio transmitters and those little RC cars you probably got for christmas.
If these aren't too expensive and can handle at least a few amps, I can see these being adopted widely in the market, not just in laptops. These things are a potental goldmine, for the improved efficiency alone (heat loss = energy loss).
Here's a previous rant of mine on AC adapters.
Yes, they are smaller than the transformers needed for non-switching power supplies, but they are there.
Adding to this is the fact that switch-mode power supplies are the main culprits for RF/EMI problems. A simple 60-Hz transformer (unless in very bad shape) emits very little of anything in the RF spectrum.
I assumed that the article was in fact referring to switching supplies, since they mentioned the EMI issue as one of the problems that their idea solves.
The only thing I wonder about is decoupling. Not knowing exactly how they work (the article isn't all that technical), I wonder how well decoupled the output is from the input. I recall a laptop being recalled over poorly decoupled modems, causing a shock in some circumstances; with 110 to 220 VAC, I think the problem would be worse, but it's possible that there is a good degree of isolation in these things.
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The real problem is that there is no standard connector for low DC voltage. Why isn't there one? This would benefit everyone. This isn't a very difficult problem, except that it needs support of big businesses. But it seems that it would even benefit them.
When I travel I have to bring 9 power supplies (2 laptops, mp3 player, still camera, video camera, 2 cellphones, razor, toothbrush). This is insane! Of course I don't always bring all these devices. I often leave them behind not because of the device itself but because of the weight and volume from the power supply.
While I'm glad to see that someone is actively working in the area, this idea is many decades old. About 20 years ago I obtained a sample kit from a vendor of the PZT and kynar type piezo films and the technical materials with the films gave formulas for computing the width, length and thickness of the films for creating voltage transormers. They gave many construction hints for increasing the output current and suggested operating at frequenccies greater than 500kHz. BTW, they are wonderful tweeters when connected to an audio amplifier. Here is a link to an IEEE artical on the history of Piezo ceramic transformers and filters. http://www.ieee-uffc.org/ultrasonics/jan1.pdf Doesn't mention the film based transformers though. Here is another link to an IBM text article describing kynar voltage tranformers from the late 60's. http://www.research.ibm.com/journal/sj/mit/section c/paradiso.txt
My laptop is currently using 15W (with a crappy power factor of 0.5!) and it isn't even charging. When charging or when the HD is on, it takes over 25W. The current Apple laptop power supplies are rated at 65W.
So where does this article get the 12W figure from?
I also question the likelihood of ever using these things. Current laptop power supplies are the size they are largely as a heat dissapation and safety issue (have you seen the requirements for computer power supplies?). They are switch mode supplies and very efficient.
To be smaller, these piezo power supplies will have to be more efficient and thus produce less heat. Then they can be smaller without overheating.
Thanks to the grad student for the more detailed view of this field. My first question upon reading this headline though was,
what do the Japanese know that we don't? As someone that travels to Japan extensively, I've become enamored with their electronic consumer goods market. One of their many nice touches -- very small transformers/power adapters for their phones/computers/you name it. Easily half the size of their American counterparts.
So what gives?
Speaking of DC power conversion technologies...
I know that DC power transmission went out with Westinghouse's AC transmission, mostly because DC doesn't really work over significant distances. Would it still work over small distances, say in a house or apartment? (For the sake of argument, say that cable runs could be kept to a maximum of a hundred feet.)
Assuming that it can work like that, why isn't there DC power distribution alongside AC in many situations? We have so many damned wall warts that it'd be worth it to distribute, say, 24VDC and step it down to 12, 9 or 4.8124VDC. (Whatever's popular.)
Wouldn't it be more convenient to replace those clunky wall warts with cables designed to step down DC voltage?
Question is, what exactly is the hardware required to shift DC voltage? I know AC can use a pair of coils with differing winding counts (that's a transformer), but how do you step down DC voltage? And can it be done on the cheap-cheap, and in a small footprint?
--grendel drago
Laws do not persuade just because they threaten. --Seneca
When I visited IBM's Almadden Research Centre in 1997 I recall seeing a cable that looked just like a power lead, but it had the power supply built into the cable. You plugged it into AC power at one end and DC came out the other.
They were having problems getting aproval from the power company as I recall...
My memory is getting poor at my old age, so perhaps I'm retelling a story of a friend-of-a-friend who thought about this idea, but I'm pretty sure I saw it - lots of geek magic happened on that trip in 1997.
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Almost all power supplies for consumer electronics, together with so-called energy saving light bulbs, LED lights, etc. cause significant losses in the power distribution networks. Why? Because they draw current only on the top of the sine wave.
Think about it. The first stage of most power supplies is a simple rectifier circuit. A capacitor that is charged through a couple of diodes. Diodes are open only when the line voltage is grater than the capacitor voltage. And that happens only on the top of the sine wave.
Why is this a Bad Thing? Because if you make a Fourier analysis of the current you will see that a large part of the current has a higher frequency than the normal 50/60 Hz. This is called higher harmonic current and the transformers in the power distribution networks really suck at transforming it (the losses in the ferromagnetic core of the transformer rise with the square of the frequency!).
Everyone that talks how LED lights and those fluorescent light bulbs will save environment doesn't know what he is talking about. The losses only move from your house to the nearby transformer (But of course, you do not care about that, do you? You only care how much you pay for your electricity bill).
I really hope that this new kind of a power supply doesn't have these drawbacks. It would really make life easier for folks that take care of the distribution network.