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Smaller power adapters

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Nucleophobe

Thu Sept 13 2012, 10:56PM

Registered Member #108 Joined: Thu Feb 09 2006, 11:44PM
Location: Billings, MT
Posts: 61

Hi all,

I'm trying to help my brother with a project requiring a small yet high-output power supply (AC-DC). I've noticed in recent years that power adapters seem to be getting smaller. For instance, on my 6-year old Dell laptop, I used to have a power supply that looked like this (85W):

and now they have a similar model that looks like this:

Notice that the second is much more slim, even though it puts out up to 90W.

Does anyone know how these have been redesigned? It doesn't seem like they are using traditional iron-core transformers anymore... I've noticed wall-warts getting smaller too, even for things which are fairly high wattage.

Any thoughts?

Thanks!
-Ken

Tony Matt

Thu Sept 13 2012, 11:41PM

Registered Member #3700 Joined: Sat Feb 19 2011, 12:59PM
Location:
Posts: 107

Hi Ken !

Yes, these "battery adapters" do not work at 60Hz.

A 60Hz 80-100W iron core transformer weigth 3kg or more.

Most are 50~150kHz inverters or flyback converters. They have a small ferrite core transformer to insulate the output from the 60Hz line.

Dr. Dark Current

Fri Sept 14 2012, 06:06AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

They can be made smaller by increasing the frequency, but only up to some point, because this basically only affects the size of magnetics. Or they can be made smaller by using underrated components (very likely today...)

Dr. Slack

Fri Sept 14 2012, 07:03AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

The first step-change in miniaturisation a decade or so ago when when they upped the frequency and changed from iron to ferrite.

The steady decline in size since then has been improved silicon, gradually chipping away at conduction losses with lower RDSon, and switching losses with lower charge storage and faster switching times. In mass commercial equipment like this, lower losses don't translate to higher efficiency and cooler running, they translate to smaller and lower cost assemblies running at the same high temperature.

Electroholic

Fri Sept 14 2012, 07:39AM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

There's also planar transformers.

Nucleophobe

Fri Sept 14 2012, 11:03AM

Registered Member #108 Joined: Thu Feb 09 2006, 11:44PM
Location: Billings, MT
Posts: 61

Thanks for the input! I didn't realize they used flybacks to step down voltage. I'd only heard of those being used in old CRT's to step the voltage up.

The clarification between iron and ferrite cores helps too (ferro - iron so I thought they were synonymous). I'll have to read up on that.

Electroholic wrote ...

There's also planar transformers.

Do you think that's what they use in the slim charger above? I can't seem to find any pictures of it taken apart. I just looked them up though, and this seems like a great option! Thanks.

My brother is looking for a transformer in the 500-1000W range. One route could be stacking 5-6 of the transformers like the slim one above and wiring them in parallel, but that's sloppy. All of the planar transformers I've found online seem to be made for lower voltages though (46V input). I guess at this point it might be a game of contacting different vendors/manufacturers.

A microwave oven transformer would be an easier source of such a high current power supply, but prohibitively heavy.

Conundrum

Fri Sept 14 2012, 03:22PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Piezo transformers (aka Transoner).
Should have called it a Transstator, then all the Trekkies would buy one

Also there are like 5 ways to make a module which uses off the shelf parts and no other wound components, however it wouldn't pass the UL tests because if dropped there is a 0.02% chance of an input to output short instead of a cracked transformer.

...

Fri Sept 14 2012, 09:47PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

You might want to look into Vicor power supply modules, they are the best I know of in the 'as much power in a tiny-ass package' department. A bit in the pricey side, a 500w module will run you $200 or so unless you can find the one you need surplus. One tricky bit - most of them require a DC input, so you are on your own for rectifying/filtering mains to power them.

ex

$200 a piece 500w weighs a whopping 8 ounces

Conundrum

Mon Sept 17 2012, 02:43PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Where the hell is my micro PC power supply already? 750W nearly doubles the weight of my machine..

-A

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