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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.
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).
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
For example, converting from 6 V to 5 V at a current of 1 A means a voltage drop of 1 V. Input power is 6V * 1A = 6 W, whereas output power is 5V * 1A = 5 W. The difference is wasted heat, and you can always calculate this as voltage drop times current. You need to choose a suitable heatsink to accommodate the heat. For many electronic gadgets the current is small enough that the waste is not a concern, but with computers you need several amps, so a regulator would be out of the question.
However, a transformer from 6 V to 5 V would have ideally equal input and output power. Keeping the input at 6 V, 1 A, the output would be 5 V at 1.2 A, i.e. the same power, no waste. However, "DC transformers" are always a little complicated (basically inverter+transformer+rectifier) and there are other losses.
Escher was the first MC and Giger invented the HR department.
Actually, DC is more efficient than AC over long distances. The problems with loss have more to do with the voltage. The reason DC lost to AC early on was that AC is easily stepped up to high voltages for transmission, then dropped to "safe" voltages for local distribution. 100+ years ago, all they had were regular copper-wound inductive transformers, and they only work with AC.The problem we have now is that all our DC devices are slaves to their wall-warts, most of which are copper-wound inductive transformers and require AC power. Being that they all had their own power supplies anyway, all those DC devices have different voltage requirements, usually dictated by the "power-hungriest" component in the device. Thus we have no standard for low voltage devices, and no real hope of seeing a standard anytime soon. The closest we have is 12VDC, but only for devices you could conceivably use in a car! You could set up your own home DC power system, but how much will you end up paying for all the DC-DC converters to match the voltage to the device?
If a job's not worth doing, it's not worth doing right.
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.