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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."
The current power adaptors don't use transformers. They're switch-mode power supplies, which use a small inductor and a bunch of circuitry to control switching and regulating.
So, yes, the article states that the new piezoelectric transformer will be smaller than regular transformers, but the current laptop power supplies DONT use regular transformers!
So, the real question is, will the piezoelectric transformer be SMALLER than a switch-mode supply, AND, will it be more efficient?
Who is this new Piezoelectric transformer aligned with?
;- )
Will Megatron get his alligeance and collect enough energon with his help to conquer earth and Cybertron, or will Optimus Prime woo him to the side of good and save us all?
You can't take the sky from me...
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?
Sounds electrifying! We need to rectify this alternating situation. We currently need to take a more direct approach. Let's hope they can induct some more engineers, and they can harness the capacitance of their talents and rectify the situation.
We shall now meditate, repeat after me:
Ohm
Ohm
Ohm
I am doing some graduate studies in this field, so here's a quick breakdown.
Power electronic circuits have traditionally been based on magnetic technology, and until recently, have not been part of the tide of miniaturization and integration advances from which signal-processing integrated circuits have benefited. In an effort to miniaturize power components, acoustic rather than inductive coupling can be used as the basis for a transformer. Note that acoustic coupling can be achieved through piezoelectric *or* magnetostrictive means.
In a piezoelectric transformer, the direct and converse piezoelectric effects are used to acoustically transform power from one voltage and current level to another through a vibrating structure. The converse piezoelectric effect, in which an applied electric field produces a resulting strain in a body, is used to convert an oscillating electric field applied to the left half of a structure, such as a bar, into a vibrational mode of the entire bar. If driven at resonance, standing-wave distributions of large amplitudes of stress and strain result. The resonantly amplified strain in the right half of each bar is converted to a voltage across the output terminals by the direct piezoelectric effect. Depending upon geometry and materials parameters, you can obtain voltage amplifications of various magnitudes, with associated step-downs in current level.
The unique nature of the piezoelectric transformer offers the opportunity for innovative circuit design such as operating above resonance for inductive behavior to achieve soft-switching without compensating inductors.
The YoYo shaped adapters for Apple's PowerBooks have already been replaced by small lightweight adapters. The current ones are tiny and I carry it everywhere without noticing it at all. It looks like the iPod power adapter only slightly larger. Take the current Apple power adapter and compare it to some other laptop manufacturer's power supply and the difference is clear.
Ok, so here's a couple of questions..... the piezoelectric effect is based on physical vibration. In essence, we are introducing moving parts into a power supply. This prompts the questions:
1. Do they wear out?
2. Will other motion or vibration cause voltage spikes or sags?
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).
I have a 12" Powerbook G4(original model), and let me tell you, the AC adapter is just excellent. It is very solidly built, and unlike some of my Apple AC adapters of the past, the wire has not frayed at all. I wrap and unrwap it every day, too, so this is even more impressive.
The small prongs that flip out from the brick are very handy for winding the wire around, and the design is simple, small, and much more durable than other companies' adapters I've used/seen.
But for this fellow to say the yo-yo design was "great" is just silly. The design was good for its time, but I have one, and the wire frayed eventually, and compared to the current white-brick adapter I own, it is a piece of crap.
Here's a previous rant of mine on AC adapters.
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
Well stick that adapter in the front of your pants -- then you won't hear any complaining about the bulge being too big.
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.
I am doing some graduate studies in this field, so here's a quick breakdown. ...
So if I'm understanding correctly, this is roughly equal to driving a speaker with a high voltage, and picking up the sound on a dynamic mic... resulting in a low voltage output from the mic. Accoustic coupling, only at a miniature and inaudible scale in a self-contained unit.
Cool!
NGWave - Fast Sound Editor for Windows
For an electrical engineer you don't know a lot do you ? A decent transformer of 48VA (2A, 24V) will run barely warm if its designed right. Increasingly transformer designers are using cheaper and cheaper techniques which has reduced the regulation of small transformers to as much as 75%. A 48VA TOROIDAL transformer runs basically cold, and is smaller than a clenched fist.
A an on-line (90-280 V AC In) SMPSU DOES NOT work in the way you describe. The input stage rectifies the incoming AC to high voltage DC (110 x root(2) )The High direct voltage (500 volts) is then chopped at very high frequency and transformed and isolated by a very small high frequency core.
The piezo electric method is interesting, but TANSTAAFL, and the catch is that piezo materials suffer from hysteresis loss, which results in, you guessed it, heat generation.
Electromagnetic transformers are close to perfect machines, particularly as the size increases.
Steve
Sorry to reply again, but something occurred to me. In a normal power supply, a load on the output side directly affects the current draw on the input side. How does that work here? Other than having some kind of input-side regulation and feedback (opto-coupler?), similar to what we have now with switch-mode supplies, I'm not sure how this would work.
By itself it seems that this technology would draw about the same amount of input current, regardless of load. Of course it's possible that it's exactly a "normal" switching supply, with the transformer swapped out in favor of a Piezo device -- in which case the other problems have already been solved.
Any insight?
NGWave - Fast Sound Editor for Windows
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
Most laptops use about 12 watts?????? If these guys are working towards making their pizo suppkies reach a target of 12 watts of power, then it's going to be a long time before we'll ever be able to use them with real laptops, which can draw 75 watts or more. The article seems high on hype and low on anything meaningful.
I'm an American. I love this country and the freedoms that we used to have.
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.
|>>?
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.
It's simply full of inaccuracies. The piezo transformer is not a new idea. You take a piece of piezo-electric material, excite it in AC (thus making it vibrate) and, with electrodes placed properly on the same piece of material, you get back electric signal from the vibration.
This stuff is already used in low-to-high voltage converters (e.g. the inverter in the laptop panel - its job is to produce high AC voltage for driving the backplane CCFL). However there are tremendous shortcomings when comparing to the mature magnetic energy conversion:
1) LOWER efficiency - if you can get 84% you've got a lucky day. Magnetic-based conversion can easily achieve 90-95%.
2) to work properly, these things must be driven at resonance, i.e. the AC input signal must match the resonating frequency of the piezo-transformer. This is much more difficult (think dynamic frequency tuning) than driving the wide bandwidth magnetic transformer.
3) derived from 2), the driving signal must be sinus (the energy confined in a narrow spectrum). This is very difficult. A magnetic transformer is usually driven in switching-mode - certainly all AC-adaptors (off-line AC/DC converters) for laptops are.
4) the input/output voltage ratio is fixed by the piezotransformer geometry. A ratio higher than 1:10 was very unusual back in 2001 when I designed back-light inverters with them. In contrast, the magnetic transformer is very versatile and, when controlling the insulation between the primary and secondary(ies), you can easily achieve factors of 100s.
5) present piezo materials have much lower power density ratings than the better magnetic cores. This means that for the same 80W AC-adaptor you'll need a much bulkier piezo-transformer than a magnetic transformer to transfer that power.
Did you see any of these major setbacks mentioned in the article? What a piece of crap!
B.t.w. it makes no sense to integrate the AC adaptor in the laptop as it limits its portability. When you're on batteries and you can't use the AC outlet, you don't want to carry with you the extra weight of an useless AC adaptor, do you?
Serban