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Piezoelectric Transformers 190

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."
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Piezoelectric Transformers

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  • by Chmarr ( 18662 ) on Thursday December 25, 2003 @01:34PM (#7808512)
    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?
    • Not really (Score:1, Informative)

      by Anonymous Coward
      They typically have small flyback transformers. Making them smaller wouldn't allow us to redesign adaptors (or fit them into a pen).

      The whole idea of a switching power supply is that it gives a regulated output. A transformer would still give you an AC output, which is useless by itself.
      • Re:Not really (Score:1, Informative)

        by Anonymous Coward
        Well, you are wrong too. You can regulate the output of a transformer, but
        that doesn't make it a switch-mode supply. The really bulky (non-switching) supplies are
        called linear supplies and are only about 1/4 efficient.
    • by FreeMars ( 20478 ) on Thursday December 25, 2003 @01:45PM (#7808564) Homepage

      That's going to be a big surprise to the folks who manufacture transformers for switching mode power supplies [].

      Yes, they are smaller than the transformers needed for non-switching power supplies, but they are there.

      • by sfe_software ( 220870 ) on Thursday December 25, 2003 @02:31PM (#7808744) Homepage
        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.
    • You have not the faintest clue what you are talking about do you.

      They may not use regular transformers, but they still use transformers. All offline (i.e. connected to mains) SMPS use a transformer. They have to for safety reasons. The transformer provides galvanic isolation so if there is a failure in the electronics somewhere you don't end up with live mains on the output.

      Low voltage DC-DC SMPS do indeed use a small inductor as a charge storage device, and you could even do the same with rectified mai

    • dc-dc ac-dc switching power supplies may not use transformers (besides isolation as mentioned below), but they're chocked full of electronic components. Reduction of components count reduces failure points, manufacturing cost and price.
    • F

      Please note the inclusion of transformers as a componant of ac/dc switch mode power supplies.

    • by Animats ( 122034 ) on Thursday December 25, 2003 @02:35PM (#7808760) Homepage
      Some wall transformers use switching power supplies, with a small high-frequency transformer after the chopper, and some are linear, with a front-end transformer running at 50/60Hz.

      Worth mentioning is the forged UL safety label problem. If a power supply doesn't have a UL or CSA label, don't buy it. It will probably catch fire if shorted or even heavily loaded. A UL label must have the UL logo and a certification number. UL certifications can be looked up here. [] This is worth doing for desktop computer power supplies, for which forged certifications are a big problem. The ones that catch fire are almost invariably uncertified. UL requires that no single component failure can cause a fire.

    • Yes, your point was the first thought that struck me as I read the article. Then I came across this gem: Most laptops require about 15 volts direct current with less than one amp of current and about 12 watts of power.

      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

    • by albeit unknown ( 136964 ) on Thursday December 25, 2003 @03:42PM (#7809029)
      Totally wrong.

      Most electronic products, especially those using switch-mode DC power supplies, do use transformers. The reason is that the transformer provides galvanic isolation from the AC mains. This helps prevent transients like lightning strikes from propagating through the device. Also, it prevents the wrong parts from becoming "hot" because the cord is plugged in backwards.

      Products that do not have transformers have much more stringent requirements for creepage and clearance distances, and are usually simple devices. A drill, for example. Hard to do with an electronic device with lots of buttons and slots.

      The high-frequency operation of a switch-mode power supply does allow the magnetics (transformers and inductors) to be much smaller than their 60 Hz linear counterparts, but they are still there.

      Please refrain from commenting about something you know nothing about, as someone may read your post and build something lacking the necessary safety features and hurt themselves.

      • The reason is that the transformer provides galvanic isolation from the AC mains. This helps prevent transients like lightning strikes from propagating through the device.

        You're not serious, are you? A lightning strike would pass easy trough a transformer. Take a good look on a transformer and see how much isolation there really is between the mains and the secundairy coil. They can handle (at least) 4KV, but they can't handle a lightning strike.

        There are numerouse designs from SMPS, and many of these

        • Optocoupler (Score:1, Informative)

          by Anonymous Coward
          From my experience, most switch-mode power supplies use an optocoupler to isolate the feedback loop from the output.
        • And a surge protector can get blown out by a lightning strike, too, but surges that are stoppable by the same surge protector can have been created by a lightning strike. It was just farther away.

          Isolating transformers really do work for many things, even if thesis-level detail wasn't included in some specific post on Slashdot.

    • I can't really say whether they will be smaller or not (having read the article), since you have a point here about the power supplies not containing transformers...

      They are saying that heat won't be an issue, as it is with current laptops, so we can conclude from that that the conversion will be more efficient than the current power supplies.

      On the other hand the article mentions laptops that typically use only 15 watts of power. While these may exist (not sure about that), I think these will be quite ra
  • by Scrameustache ( 459504 ) on Thursday December 25, 2003 @01:35PM (#7808523) Homepage Journal
    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? ;- )
    • When I read this headline, I really thought someone modded a transformer toy to transform by itself or something to that effect.

      On that note, this probably could be an Ask Slashdot question, but does anyone know who to go to, to create a Decepticon icon replacement for my honda symbol on my prelude? I always thought that would be a real subtle, cool thing...(since they look similar)
      • Get a dremel tool and make a template by printing off a image to the size you want it. Get some fiberglass (REAL cheap, like $4/yd) and some epoxy resin. You COULD use Carbon Fiber, and make it invincible and very very sharp-looking, but that shit is quite expensive ($50/yd), but it works the same as the fiberglass fabric. Lay the fiberglass sheet down and apply the resin. Do this a few times to give it some thickness and integrity. Check out some fiberglass sites to tell you the exact procedure, it's prett
  • ultrasonic (Score:5, Interesting)

    by spoonist ( 32012 ) on Thursday December 25, 2003 @01:39PM (#7808535) Journal
    "Piezoelectric power adapters operate in the ultrasonic range so humans cannot hear any sound produced..."

    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?

    • by Seahawk ( 70898 ) <> on Thursday December 25, 2003 @01:57PM (#7808615)
      Well - me reading slashdot havent driven my cat nuts yet - and slashdot definately creates a high pitched whine once in a while...
    • Re:ultrasonic (Score:2, Interesting)

      by gregorious ( 449337 )
      Hmm, a power supply that repels flying insects. Or, attracts 'em.

      With other piezo devices I sometimes hear an irritating mosquito-like whine. I've wondered if this is due to interaction with casing, or resonance with other components. Two piezo components could set up beat frequencies. Gaaah. Jbecause we can't hear its dominant frequency doesn't mean a sound-generating device is Goodness on a Bun.
    • Re:ultrasonic (Score:4, Informative)

      by Flavio ( 12072 ) on Thursday December 25, 2003 @01:58PM (#7808619)
      Regular switching power supplies also operate in the ultrasonic range.

      Well designed supplies are reasonably quiet (as one can verify by making them operate in lower frequencies), so pets tolerate them.

      Likewise, badly designed supplies really pollute the airwaves. It's usually impossible to tune an AM radio within 20 meters of a cheap desktop computer PSU.
  • by rduke15 ( 721841 ) <[moc.liamg] [ta] [51ekudr]> on Thursday December 25, 2003 @01:40PM (#7808541)
    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?
    • Why cant they produce a dual voltage version? This mystifies me.

      In a dual voltage switch mode power supply the AC input is rectified to form a high voltage DC which is then switched at high frequency(tens of kHz or so) and passed through a ferrite transformer to step down the voltage. The dual voltage bit comes from the rectifier being a bridge rectifier when you set the switch to "240" and a voltage doubler when you set the switch to "110", both giving a DC voltage to the switch somewhere around 300V.


      • by sfe_software ( 220870 ) on Thursday December 25, 2003 @02:37PM (#7808771) Homepage
        The dual voltage bit comes from the rectifier being a bridge rectifier when you set the switch to "240" and a voltage doubler when you set the switch to "110", both giving a DC voltage to the switch somewhere around 300V.

        That's one way, but most notebook adapters don't have such a switch. Rather, they accept a very wide range of input voltages. They work by simply being able to regulate and handle the full range of voltages; at 90v input the regulator would be passing quite a bit more current through, where at 240v the duty-cycle would be dropped significantly.

        The piezo supplies, from what I gathered from the article, are more along the lines of a basic 60-Hz transformer; eg, you get some specific ratio of input/output voltage, without regulation. I'm sure these could be easily regulated, and I'm sure a future version will be.

        It's (AFAIK) brand-new tech, so more features will come I'm sure, if the technology takes off.
        • They are just a transformer replacement, so I would think it would still need most of the regulator electronics that a normal SMPS (switch mode power supply) has. Not sure the size will be significantly smaller, though. SMPS transformers are small.
    • The article says the adapters are 1/4 the size of current models. So you could bundle two together (perhaps in a single case, with a switch) and it would still be only half the size.
    • I would tend to think not. The physical geometry of the piezoelectric ceramic is what determines the voltage ratio. It might be possible to package several different configurations in one enclosure, but at its core it's a fixed ratio.

      In contrast, the switch-mode powersuppy you're using now rectifies line AC and then switches it at a very high frequency (around 40kHz) and uses the duty cycle of this switching to regulate the output. Through a closed-loop controller it regulates the output to a constant l
  • by niko9 ( 315647 ) * on Thursday December 25, 2003 @01:41PM (#7808548)
    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:


  • by Gary Whittles ( 735467 ) on Thursday December 25, 2003 @01:47PM (#7808573) Journal
    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.
    • This guy knows electro crystal chem.
    • Then you should be able to answer the obvious questions that people on these forums have posed: what's the efficiency, and will it drive pets insane?
    • 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?

    • First thing that comes to mind is a potentiometer where a voltage is applied to the ends and the wiper is adjusted to get a voltage (i guess you could also use a multitap transformer analogy).
      If this is the case it sounds like concerns about selectable input (120 / 240 vac) can be resolved by tapping into the crystal at different points for different voltage inputs, not to mention varying different taps for differnt voltage outputs.
      The thing that baffles me is how it works in the ultrasonic range. i
    • 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.

      • I always understood we used plain transformers because if you increase current drain on the output, the current in will increase to compensate. Something about the field in the tranny becoming unbalanced and the flux pulling more I into the primary...something like that. If you analogy is right, you can't draw more current from the secondary than is fed into the primary - useful for some applications, horrid for anything you'd want a transformer for.
    • 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 "no
    • The biggest obvious problem with this technology is the fact that you can no longer have universal power supplies, since the voltage ratio is a function of distance.

      Nice to remove the inductors and other compensating components, but it seems like there is still a HUGE trade-off.

    • From the article:
      Transformers are made from piezoelectric materials by applying a chopped electric voltage to one side of a piezoelectric wafer.
      It seems that they are still using some sort of line-side switch to manipulate the input to the piezo crystal. This means that having a large input voltage range is still quite possible by varying the duty cycle or turn-on phase point of the input waveform.

  • by Anonymous Coward

    The problem is not the transformers, you can make them much smaller than the standard wire wound ones with planar magnetics.

    The real problem is the rectification of the output of the transformer to get DC again. You still have to use diodes, and the very best ones still have a significant forward voltage drop. As a result the generate heat and need cooling.

    Open up any ATX PSU, and the main heatsinked components are the output rectification diodes. It is cooling these that limits power supply size. It is

  • No YoYo. (Score:3, Informative)

    by Anonymous Coward on Thursday December 25, 2003 @01:57PM (#7808613)
    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.
  • by vmalloc_ ( 516438 ) on Thursday December 25, 2003 @02:05PM (#7808651)
    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).
    • 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
  • by Qweezle ( 681365 ) on Thursday December 25, 2003 @02:14PM (#7808683) Journal
    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.
    • Really, I much prefered the yoyo model, or the older models with the molded plug, as I don't find the current white brick models that stable. I've had my mother's ibook's AC adapter replaced twice and mine once as the end of the plug kept loosening and eventually fraying and dying, as the ends of the current white brick adapters are not fully molded but can be disassembled quite easily.
    • I like the white rectagle thing. The original was not so well built, but still lasted a year. I just purchased the new model, and it much better. Thicker power cord for home use and an extra grommit on the output.

      The form fact is not noticible. The reason I prefer this to the saucer adapter is the interchangable power cord. It is usually unnecesary for me to carry the cord, so it is nice to have the small adapter.

    • There are at least two versions of the white brick adaptor. I have a new 1.25 15" and I have a later version than my girlfriend's 800 TiBook 15". They look the same, but on closer inspection, the cord connection is a little different the new one has a stronger rubber connection, the old one had a rounded surface so the cord wouldn't rub. This is hard to explain, you'd probably need to see both to understand what I am talking about. Also, the new version seems to carry a ground connection through the heavy d
    • Don't just trust the damn thing, if it's the model where the DC cable enters the plastic brick without the classical grommet but straight into a trench you've had it... it'll break and badly too! Mine died the day I was showing off the beauties of Os X to a chap I had just convinced to get an iBook; and a bad death was it too! The flimsy cheap wire (Apple must have noticed since it changed the design and the wire gauge) shorted on the laptop plug side and the circuitry cooked itself destroying the whole ada
    • The removable cord/travel prongs - great.
      Having to replace my p/s 5 times in the last 18 months - really poor design. In almost all cases, the strain relief at the notebook end broke, and within 2 weeks or so, it was dead. (once, the brick itself died. hacked something together using the dead ones).

      Yes, it's under warranty, but still a stupid design. And I've had a few clients with the same problem (not realizing that it was under warranty too - $150 for a new one)
  • by ortholattice ( 175065 ) on Thursday December 25, 2003 @02:21PM (#7808703)
    Does anyone remember those cheap transformerless adapters you could buy around 1970? They replaced a 9-V transistor radio battery and were the same size, with a cord coming out that plugged into 110V. I opened one up, and there were 4 parts: a capacitor in series with the AC line, a rectifier diode, a 9V zener diode, and an electrolytic filter capacitor. I wonder if anyone got electrocuted by them, and when they were (as I assume) banned.

    Here's a previous rant [] of mine on AC adapters.

    • The main problem with those is that with a zener diode you can only get a tiny amount of current. Enough to power a small transistor radio, not enough to power anything else. Not to mention that the regulation is total crap. Those devices are cheap and that's their only positive side. You could make a transformer brick that's smaller and more efficient.
      • Nice closing comment, but in 1970's you couldn't make a transformer brick smaller OR more efficient.

        The electrolytic only charges up in one cycle (current is only drawn from mains on one cycle) and THEN only insofar as the electrolytic capacitor has been discharged. No discharge means do mains current used (except to cover leakage).

        And lots of modern plug-in timers and light sensitive switches worked the same way.

        I converted such a light sensitive switch to a radio-control mains switch by combining it w
    • Sure, this device is a half wave charge pump running at the frequency of the AC power source. During the negative half cycle the pump capacitor charges to -170Vpeak and the charge is then pumped to the electrolytic as the input AC voltage swings from -170Vpeak to +170Vpeak. The total charge pumped on every full cycle is q=c*deltaV where deltaV is 340V for 120VAC. The average current supplied is i=q*f. So for a 120V 60Hz source with a 0.1uF pump capacitor you can draw an average of i=120*2*1.414.60Hz*0.5
  • Bulge? (Score:3, Funny)

    by donutz ( 195717 ) on Thursday December 25, 2003 @02:25PM (#7808723) Homepage Journal
    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.
  • by treat ( 84622 ) on Thursday December 25, 2003 @02:40PM (#7808782)
    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.
    • by Dun Malg ( 230075 ) on Thursday December 25, 2003 @04:38PM (#7809205) Homepage
      The real problem is that there is no standard connector for low DC voltage. Why isn't there one? When I travel I have to bring 9 power supplies (2 laptops, mp3 player, still camera, video camera, 2 cellphones, razor, toothbrush).

      Because there's no standard for low voltage. How many of those items use the same voltage? How many of them are even DC? Some devices are sensitive to as little as 2 volts difference plus or minus, and "low voltage" will generally be anything from 3 to 24 volts, plus they can be AC or DC. The connector isn't your problem-- it's the power your devices require.

    • Unless you can think of a way for the companies to make up the lost profit made from selling the power supply to you - you won't see it.

  • by Hirsto ( 601188 ) on Thursday December 25, 2003 @02:46PM (#7808804)
    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. 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. c/paradiso.txt
  • If you're building power supplies, it can't hurt to have your email address end in

  • by Anonymous Coward
    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 supplie
  • Look to Japan? (Score:2, Interesting)

    by Anonymous Coward
    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?
  • by Grendel Drago ( 41496 ) on Thursday December 25, 2003 @03:12PM (#7808913) Homepage
    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
    • its called the 78XX series of voltage regulators. where XX is the desired output voltage. a lot of electronics that use 6v in use a 7805 to regulate the voltage to 5v.
      • Linear voltage regulators like the 7805 [] are cheap, easy to use and amazingly resilient (eg. protected against short circuits and overheating) but they have their disadvantages.

        The main disadvantage is heat. If you want a lot of power, especially if there is a large voltage drop, you'll need heat sink bigger and much heavier than a small switch mode converter you could use instead.

        You also couldn't get 5V from 6V with a 7805. The dropout voltage is 2V, meaning you need at least 7V to get 5V. There are s

      • by TeknoHog ( 164938 ) on Thursday December 25, 2003 @04:59PM (#7809322) Homepage Journal
        Regulators are very much not the equivalent of transformers. They can only give a voltage drop, but the current is kept constant, which is why some energy is wasted.

        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.

    • by Dun Malg ( 230075 ) on Thursday December 25, 2003 @05:01PM (#7809336) Homepage
      I know that DC power transmission went out with Westinghouse's AC transmission, mostly because DC doesn't really work over significant distances.

      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?

    • I know that DC power transmission went out with Westinghouse's AC transmission, mostly because DC doesn't really work over significant distances.

      Actually DC power transmission becomes more efficient than AC at very large distances.

      There is a certain threshold distance where capacitive losses in transmission lines become greater than losses in rectifiers and inverters.

      For example electricity from the Itaipu power plant in Brazil is transformed to high voltages with regular transformers, then rectified to
    • I know that DC power transmission went out with Westinghouse's AC transmission, mostly because DC doesn't really work over significant distances.

      That's true of the low voltage DC used in Edison's distribution system (which, by the way, is why American homes have 120/240V single phase service). High voltage DC (+/- 400 KV or so) is actually better than AC for long distance power transmission - due to lower losses and not having to keep the neds in synchronism.

      Assuming that it can work like that, why isn'

  • And I, for one, welcome our new 1/4-of-standard-lightwhight-complex-supersonic-low heat-100-to-125volts-powerconductor overlords.
  • ... would be to move the power supply inside the computer. However, that would require that the computer meet UL safety requirements.
    • A Real Solution would be to move the power supply inside the computer. However, that would require that the computer meet UL safety requirements.

      Please moderate this as +5, Brilliant ...

  • voltage (Score:1, Informative)

    by Anonymous Coward
    European standard is 230V, _not_ 220V.
  • by |>>? ( 157144 ) on Thursday December 25, 2003 @04:20PM (#7809159) Homepage
    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.
    • by Dun Malg ( 230075 ) on Thursday December 25, 2003 @05:06PM (#7809361) Homepage
      You plugged it into AC power at one end and DC came out the other.

      Gimme four appropriate diodes and a power cord and I'll build you one. Unless, that is, you're expecting something other than dirty 110VDC....
      Getting to DC it the easy part-- it's the voltage conversion that thakes up all the space.

      • it's the voltage conversion that thakes up all the space.

        As I said, my memory is hazy on the subject, but I'm pretty sure that the voltage conversion was also included in that cable. That's what made it so sexy...
  • Don't increased frequencies allow shrinking of electromagnetic components? Why not just increase the frequency?

    What about non-line-isolated battery chargers? When you're supplying power to the laptop you need isolation, but you don't if you're just charging the battery. These could be extremely small and light.

  • Aluminum wire instead of copper for winding the transformer coil would reduce the weight, although the size would remain the same.

    The reason copper wire is more common then aluminum is that aluminum is not as malleable (breaks when its bent back and forth) so it is not practical for things like household wiring.

    Since coil windings are stationary the only time they could break is during manufacturing, increasing the cost of the final product. From what I gather that's why aluminum is not used.

    • Aluminum wire instead of copper for winding the transformer coil would reduce the weight, although the size would remain the same.

      An aluminum wire has higher resistance than a copper wire with the same cross section. Because of this, transformers would have to be made out of a thicker wire which would mean bigger and (probably) heavier transformers.

      Also aluminum is a lot cheaper than copper so I don't think cost would be a problem.
  • by Avian visitor ( 257765 ) on Thursday December 25, 2003 @06:05PM (#7809626) Homepage
    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.
  • Unless they can make these thing small enough so that the frequency is inaudible, or include lots and lots of sound dampening, you're going to be hearing an annoying buzz all the time.
  • by serbanp ( 139486 ) on Thursday December 25, 2003 @08:57PM (#7810227)
    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?

    • 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.

      Add to this the point made in another post []: DC appliances require those higher harmonics.

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