AC Adapter size

Postby sanjy009 » January 5th, 2013, 8:10 pm

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I know pretty much nothing about electronics, but can anyone explain why the AC Adapter for my laptop is so much bigger than the AC adapter for my phone:
ac adapter.jpg


Here the domestic power supply is 240V, the laptop brick converts to 18.5V, I believe the USB standard voltage is 5V.

Re: AC Adapter size

Postby NURB » January 5th, 2013, 8:35 pm

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Not positive but I believe it has something to do with the size if the two batteries.
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Re: AC Adapter size

Postby Cyberdemon » January 6th, 2013, 5:16 pm

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Voltage, amperage, output, heat and cost.

The size of power bricks has to do with how much power it has to output. A cell phone typically charges on a USB standard which is only 5 Volts and ~1 amp. By comparison, if you read your power brick you'll see it's 19V and probably ~7-8 amps. That means it pushes out a lot more power, and since power transformers are only so efficient, some of that results in heat.

Heat is naturally bad, so usually everything in the power supply grows to compensate for it.

For example I have the same HP laptop and I use 3 power supplies. The recommended power supply is rated at 150 Watts since for the big workstations they can draw a lot of power.

Most of the time when I travel, I'll use the smaller 75 Watt power supply and it still works, because it still provides enough power - but if I use it for a few hours of gaming (peak power draw) the thing gets scorching hot - almost burns you to the touch.

Now if you look at a Macbook adapter it's still generally much smaller than a typical laptop. That's because companies like HP and others will find a power supply that meets their needs for multiple products (usually that means your power supply is actually designed for the largest 17" notebook with all the fixins, plus some extra margin on top) and then use that for anything below that. This way they don't need to stock a unique power supply for every laptop.

Re: AC Adapter size

Postby sanjy009 » January 6th, 2013, 6:27 pm

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Cyberdemon wrote:Voltage, amperage, output, heat and cost.

The size of power bricks has to do with how much power it has to output. A cell phone typically charges on a USB standard which is only 5 Volts and ~1 amp. By comparison, if you read your power brick you'll see it's 19V and probably ~7-8 amps. That means it pushes out a lot more power, and since power transformers are only so efficient, some of that results in heat.


Thanks. For some reason I thought the heat, and so the size of the transformer, came from stepping down the mains power supply, not pushing it through.

Re: AC Adapter size

Postby KenoLeon » January 7th, 2013, 12:33 am

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powerbrick.jpg
Alienware x51 Power Brick
powerbrick.jpg (88.91 KiB) Viewed 4277 times


Speaking of power bricks,I present this here monster of a Power Brick, it came with an alienware x51 which is billed as a slim/console type gaming pc, I think it is a shame they went this route since the whole idea was to have as small and powerful a computer as possible, the tower itself is pretty great and small (about the size of an xbox 360), but then there's this thing next to it...Sigh. ( It outputs 17A !)

While I have your attention, I should also mention that the xbox360 has a power brick the size of Texas, it's also ugly, while the PS3 has none in roughly the same footprint so it seems at least possible to hide these things trough the magic of R&D.

K.

Re: AC Adapter size

Postby yo » January 7th, 2013, 2:52 am

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Internal power supplies tend to cost more and you have to deal with the heat in your box (venting,fans,heat sinks) vs externally in a brick. As you say, Sony did it. They just decided to spend more BOM cost there.

Re: AC Adapter size

Postby Mr-914 » January 7th, 2013, 8:10 am

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It's funny how things swing back and forth.

PS one - internal PS
PS 2, v1 - internal PS
PS2, v2 - exterior PS (ie brick)
PS3 - internal PS

I prefer having a brick that I can hide on the floor than the console being 4 x larger.
Ray Jepson

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Re: AC Adapter size

Postby NURB » January 7th, 2013, 8:16 am

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Thanks for the explanation Cyber. Kind of what I thought, but thank you for articulating it much better than I could.
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Re: AC Adapter size

Postby Cyberdemon » January 7th, 2013, 9:16 am

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Power supplies are also pretty common failure points, so externalizing it is one way of making it more robust.

Those designers went though all the same trade-off decisions I'm sure. Internalize the PSU and all of a sudden the thermal guys are flipping out telling you the temperatures the device could reach (remember many of these devices have to be rated to very high temperatures, and the extra heat of a PSU running at full load can be too much without radically redesigning the product (adding a bunch of fans, vents, etc).

The X51 was a perfect example of that, trying to deliver desktop performance in a console size form factor and trying to custom design an internal power supply would've caused the product to grow even larger and cost more money, which isn't something customers probably would have cared as much about. Remember since PSU's are commodities, anything custom designed (esp on a niche product) will be very expense. Buying the same off the shelf brick that 50 other companies use and are made in the millions lets them keep the cost very low.

Re: AC Adapter size

Postby pier » January 7th, 2013, 6:05 pm


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as alluded to above, it is a matter of physics and electromagnetism to convert AC mains power to DC power at required voltage and amperage for the intended device, with margin. For higher power more iron and copper are required.

Also cost, as noted.

Also, safety and electromagnetic compatibility certifications. Power supplies are notoriously both bad emitters and receivers of electromagnetic and radio frequency energy. Externalizing it helps device designers deal with FCC, UL, CE, CSA, TUV, etc. certifications, as witnessed in your photo by the 20 or so approval agency logos.

Re: AC Adapter size

Postby engio » January 8th, 2013, 2:20 am


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Ah so that's an Aussie plug with the turned lamellas..

Sorry for thread hijack, but the question has been answered..

I bough a MUJI travel adapter in Japan, winch basically is an anything-goes-anywhere solution. I've never seen those anywhere in EU or US before (only OUR plug goes anywhere or a set of 10 different adapters) and suddenly they were everywhere in Japan and really well designed (instead of an engineers 10 min in ProE). Some even had USB built in so no need to bring your charger even. Is anyone familiar with them?

The MUJI one
http://www.flickr.com/photos/m-s-y/6955 ... otostream/

Re: AC Adapter size

Postby sanjy009 » January 8th, 2013, 6:25 pm

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engio wrote:Ah so that's an Aussie plug with the turned lamellas..


I had no idea that's what they are called.

Powerplugs and wall sockets are one of those things that always surprises me when I travel. It's something that seems so normal and right and constant, but everywhere they are different. It's like if water was different in different places:

from http://en.wikipedia.org/wiki/Power_plugs

Australia, New Zealand, Fiji, Tonga, Argentina, Solomon Islands, Papua New Guinea and China
Image

United Kingdom, the Republic of Ireland, Hong Kong, Cyprus and other countries. Compatible plugs standards are IS 401 and IS 411 (Ireland), MS 589 (Malaysia), SS 145 (Singapore), and SASO 2203 (Saudi Arabia).
Image

One of the many Euro-plugs, Albania, Austria, Bosnia and Herzegovina, Bulgaria, Chile, Croatia, Denmark, Estonia, Finland, Germany, Greece, Hungary, Iceland, Indonesia, Iran, Italy, Latvia, Lithuania, Luxembourg, Republic of Macedonia, the Netherlands, Norway, Pakistan, Portugal, Romania, Russia,[20] Serbia, Slovenia, South Korea, Spain, Sweden, Turkey, Ukraine, and Uruguay.
Image

North America, Canada, the United States, and Mexico. It is also used in Central America, the Caribbean, northern South America (Colombia, Ecuador, Venezuela and, as a legacy, part of Brazil), Japan, Taiwan, the Philippines and Saudi Arabia.
Image

and so on...

Re: AC Adapter size

Postby Mr-914 » January 9th, 2013, 8:22 am

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My fav is the euro plug. I like how they are recessed. It makes it harder to stick non-electric things into them, but also makes the plugs hold more securely.
Ray Jepson

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Re: AC Adapter size

Postby Travisimo » January 10th, 2013, 6:46 am

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After being away from the N. American plugs, they are definitely myfavorites and I really miss the small size of them... all the others seem so big when you stow it in a slim bag

Another headache is when the put the AC Adapter inside products, sometimes they make them for one power system only... so if you buy a product for US 120 volts, you're gonna have to get a power converter or a 220V version for Europe (most external adaptors work for both)

Re: AC Adapter size

Postby scrotum » January 13th, 2013, 8:52 pm

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Cyberdemon wrote:For example I have the same HP laptop and I use 3 power supplies. The recommended power supply is rated at 150 Watts since for the big workstations they can draw a lot of power.

I think I have the same HP laptop too, an 8560w. I've been looking for an additional power supply for traveling, I think I will go with a 70 Watts, about half the price of (and smaller than) the 150 recommended by HP.

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