Laptops are thin. Why are power supplies still fat?

jhsachs

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Modern laptops are pleasingly thin. I can slip one into my briefcase without making it look like a pregnant sloth.

So why are power supplies still shaped like bricks?

It seems to me that if a self-contained computer can be made less than an inch thick, a 19VDC power supply could, too. It could even be designed to nest with the computer so that the user doesn't have to jam it into the bag or stow it in a separate compartment.

In use, the nesting shape could keep the power supply out of the way and eliminate an exposed cord. If it were shaped like a wedge, thick in back and thin in front, it would give the keyboard a nice tilt without raising it uncomfortably far above the work surface.

Comment?
 

jhsachs

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That's probably literally true, but I don't think it's a real answer. Desktop computers are shaped like larger bricks for the same reason, but laptops aren't.

Laptop manufacturers put awesome resources into making their computers easy to use and transport; why don't they even try with the power supplies? The answer to that question would interest me.

As for heat dissipation... a long, wide, thin object has more surface area per unit volume than a short, narrow, thick one, so it dissipates heat better. Nesting the power supply with the computer would interfere with dissipation, but that's the type of problem that engineers are paid to solve.
 

jaguarskx

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Because the laptop power brick contains components are not easy to miniaturize without breaking the laws of physics.

For example, transformers are used to transfer electrical energy between two or more circuits which is done through electromagnetic induction which involves a magnetic flux. Basically the strength of the magnetic flux is dependent on the size of the transformer and would a direct effect on effectiveness of electromagnetic induction; or in other words the amount of power that can be transferred between circuits. Use transformers that are too small for "the job", and the power brick will not be able to provide enough power to the laptop.

Another large component used in power bricks are capacitors which are not only used to regulate power but also used as part of a circuit who's primary purpose is to convert alternating current from the AC out into direct current that the laptop can use. Again, size matters because the larger the capacitor the more power it can contain. Using small capacitors can affect how efficient the power brick can convert AC power into DC power as well as how much power the power brick can supply. Large capacitors are necessary to regulate the flow of power meaning without these capacitors the actual voltage and amperage can fluctuate which means the laptop itself is subject to not receiving enough power to function properly.


I am sure you can get a much better answer from someone who has an electrical engineering background.
 

madmatt30

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^ in all fairness your answer hits the nail on the head.
You need a large surface are for heat dissipation when converting 110/240v ac to 12/19v DC.

That means either wide/ long & thin or squat & deep.

My dell n5010 PSU (circa 2012) is actually only 3/4 of an inch think, 7 inch long, 3 inch wide so not all psu's are 'chunkers'

The only think that doesn't sit flat in a very thin laptop sleeve is the 3 pin mains plug itself.

 

orlbuckeye

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One thing is the OEM doesn't build or design the power brick. Plus their are limited companies that make them. Just like graphic cards the machines are designed around the Discrete GP's built by ATI or Nvidia.
 

JeffDaemon

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Pretty much what they said. The power conversion for the power brick is hard to miniaturist further then what we have atm unless we utilized vastly expensive metals and processes. Also in the last couple of years we've had gaming laptops that had no problem pulling 100 and 200 plus watts. Also the brick needs surface area to cool. A brick that would sacrifice surface area to be smaller would need to switch to active cooling requiring a small audible fan.

On the other hand we have seen small power supplies for some laptops (and mini PCs) because new technology has reduced power needs.
 

jhsachs

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I accept that some of these arguments explain why power supplies are shaped like bricks. I remain skeptical that they mean power supplies must be shaped like bricks.

I believe that all modern computer power supplies (office as well as mobile) are switched. There's no transformer.

There's no reason a capacitor has to be thick. In fact, "paper thin capacitors" are real products. You can find them on the Web.

Many years ago Toshiba made a line of laptops with internal power supplies. They were thick -- all laptops were, back then -- but they weren't thick as a brick! I think the reason they're no longer made is because of electrical safety regulations (a computer with no high voltage components isn't subject to them), and a belief that laptop users do not carry the power supply around with them. Which is true of some, but not of others -- definitely not true of me.
 
Novel idea, but sounds like the technology is not there yet, plus by the time this happens, the battery capacity will be good enough for all-day that you can leave the charger at base until the end of the day.
 

jhsachs

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> by the time this happens, the battery capacity will be good enough for all-day...

Many many years ago, I read that laptop batteries would be replaced Real Soon Now by fuel cells that were powered by replaceable cartridges about the size of a ballpoint pen. I wonder whatever happened to those? (Rhetorical question... the answer is pretty obvious.)
 
I hear ya, the hype always sound better than reality. But battery (not necessarily the fuel source) but the electronic has gotten more efficient over the years. Now you can surf on a Macbook for 10 hours.

But hey, you got a materials science degree? two words: Crowd Source :D
 

hang-the-9

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.It's very simple to answer you, call some laptop makers and ask them why the shape of the power supply is the way it is. If you are so certain that they don't have to be, design one that is shaped the way you think they should be.

Power supplies generate heat, attaching one to the back of a laptop would be a pretty bad idea, you want to remove heat from a computer not add to it.
 

jhsachs

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Regarding heat, I refer you back to my post about Toshiba laptops with internal power supplies. If attaching a power supply to the bottom of a laptop computer would create an unmanageable heat dissipation problem, how do you suppose they put one inside.

Regarding asking a manufacturer, I trust you're being facetious.
 

hang-the-9

Titan
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Why would I joke, you are basing things on "I think" and "They should", why not just find out why they do what they do.

You said yourself that laptop with an internal power supply was very large, if you want to make a 1 inch thick laptop with fans and vents and stick a power supply inside or under one that is up to you.

I doubt the laptop vendors are making their power supplies the way they are just because, and without actual info from design and engineering, it's all speculation as to who does what for what reason. I would not mind a small power supply you can attach to the laptop and just plug in the cord to the wall, but I would not complain about it until I knew what was needed to make one and why it was not done yet.
 

madmatt30

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I think the main issue here is you're in a fairly small minority of people who are actually bothered.

I'd hazard a guess the size is mainly down to the mass of safety circuitry that has to be built into these chargers.
http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html?m=1

Look at the 85w macbook mini charger & you'll see exactly the kind of stuff that has to be included in there to safely power or charge an expensive bit of kit.
Manufacturers certainly dont want to be replacing $1000 laptops every 5 minutes because they cut down on the PSU quality unnecessarily.
Certainly nothing akin to a standard transformer you'd use to run a 12v set of lights or even a 5v phone charger.
 

jhsachs

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There's clearly some segmentation here. At least one person (me) is constantly irritated by a power supply whose thickness makes it occupy an inordinate amount of space in his briefcase, and whose two cables are constantly getting tangled. Several other people don't see what difference it makes. I guess we'll have to agree that this is a feature some people want to see solved and others do not.

But hang-the-9, I'd much rather believe that you were being facetious than that you were serious, because if you're serious, it means that you grew up without acquiring a clue about how consumer market manufacturers work.

Try this experiment. (I won't do it because I know exactly what the result will be.) Call Lenovo, or General Motors, or Cuisinart, or ANY manufacturer of consumer products. Tell them that you've identified a significant shortcoming in one of their products and you'll be happy to tell them how to eliminate it without asking for anything in return. See how far you get. Let us know.
 

madmatt30

Honorable


Im sure its a feature we'd all be happy with if it were the norm mate,people just get used to having to plug in chunky bricks though.



thats my dell psu,its around 3/4 of an inch think so it can be done,but then theyve had to make the width inherently larger.
still the slimmest laptop brick ive ever seen though & its 4 years old or so at that,fits in a laptop sleeve pretty easily let alone a proper briefcase,the mains cable & plug are the main bugbear.



thats the newer model,smaller still so dell at least are trying, having delta onboard as their psu oem does make the difference here I think as theyre probably the best manufacturer around with standalone ac-dc converters/chargers.
 

hang-the-9

Titan
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I did not say that they will answer you, but if you want to know whey they are the size they are, where else would you find out? If I knew how to fix a product to make it better, I'd get a job doing it or design it myself and sell it. If you know how to design a smaller power supply that won't cost too much and will not cook itself during use, make one, sell it.
 
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