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Windows 7: How do PSU's work?

07 Dec 2012   #11
bobafetthotmail

Win 7 Pro 64-bit 7601
 
 

Quote   Quote: Originally Posted by Britton30
I for one would like a simple, understandable of how switched mode circuitry works and what it is/does.
Try reading here (one of my favorite sites, btw). They say it's a more efficient way to convert wall socket AC to DC for computer components, that allows the miniaturization of high power PSUs to the point they actually fit in a computer case.

They explain the technicalities in a readable way even for me that I'm not exactly an electrician, and provide dumbed-down diagrams (that I still can't properly understand) but don't rely too much on them to convey the point.



BTW, in another article they talk about how to properly test a PSU the pro way.


My System SpecsSystem Spec
.
07 Dec 2012   #12
ICIT2LOL

Desk1 7 Home Prem / Desk2 10 Pro / Main lap Asus ROG 10 Pro 2 laptop Toshiba 7 Pro Asus P2520 7 & 10
 
 

Quote   Quote: Originally Posted by Britton30 View Post
I for one would like a simple, understandable of how switched mode circuitry works and what it is/does. I have looked at Wikipedia and electronic sites and have a headache from seeing squiggly lines and diagrams.

The same paper clip test is listed on the Corsair site with no warnings or other unneeded info.
Hiyya Gary Now this looks complicated and it might take a bit of reading but the pics are good and really it is all down to transforming the mains ac voltage down the dc voltage we need for the motherboard opto drives GPU's etc

Anatomy of Switching Power Supplies | Hardware Secrets

Now to do that with a "normal transformer would take some hideously large and not to mention VERY expensive transformer to get a secondary voltage of around say 25 amps at 15 volts - for the 12v supply (you loose volts in rectification and regulatory circuits)
The switched mode uses circuitry to be able to use small cost effective transformers to turn that high frequency / high voltage back to low volts / high current without the weight bulk and cost
The downside is that it is more costly to make but that is offset by the efficiency.

But if there is anyone who thinks I am being too simplistic I stand to be corrected.
My System SpecsSystem Spec
07 Dec 2012   #13
Indianatone

Windows 7 x64 Ultimate and numerous virtual machines
 
 

Quote   Quote: Originally Posted by ICit2lol View Post
Quote   Quote: Originally Posted by Britton30 View Post
I for one would like a simple, understandable of how switched mode circuitry works and what it is/does. I have looked at Wikipedia and electronic sites and have a headache from seeing squiggly lines and diagrams.

The same paper clip test is listed on the Corsair site with no warnings or other unneeded info.
Hiyya Gary Now this looks complicated and it might take a bit of reading but the pics are good and really it is all down to transforming the mains ac voltage down the dc voltage we need for the motherboard opto drives GPU's etc

Anatomy of Switching Power Supplies | Hardware Secrets

Now to do that with a "normal transformer would take some hideously large and not to mention VERY expensive transformer to get a secondary voltage of around say 25 amps at 15 volts - for the 12v supply (you loose volts in rectification and regulatory circuits)
The switched mode uses circuitry to be able to use small cost effective transformers to turn that high frequency / high voltage back to low volts / high current without the weight bulk and cost
The downside is that it is more costly to make but that is offset by the efficiency.

But if there is anyone who thinks I am being too simplistic I stand to be corrected.
No you are doing a good job. I'll have a think about a basic explanation of how an Switching Mode Power supply works and what the benefits are and why almost everything including wall warts for phones have them and then post it here after the weekend.
My System SpecsSystem Spec
.

07 Dec 2012   #14
Indianatone

Windows 7 x64 Ultimate and numerous virtual machines
 
 

Quote   Quote: Originally Posted by Britton30 View Post
The same paper clip test is listed on the Corsair site with no warnings or other unneeded info.
That is for safety reasons all Computer Power Supply Manufactureres and vendors regard the PSU as a "closed black box". Test it by turning it on or replace it with another unit. It is perfectly safe to do this.
My System SpecsSystem Spec
07 Dec 2012   #15
ICIT2LOL

Desk1 7 Home Prem / Desk2 10 Pro / Main lap Asus ROG 10 Pro 2 laptop Toshiba 7 Pro Asus P2520 7 & 10
 
 

Thank you Tony I shall take that as a real compliment and I am glad we have you on board so to speak with this one as there heaps of questions that need to be answered.

As Britton pointed out it needs some explanation of how these things work. I personally think that once folks know what dangers lurk inside they would be more inclined to follow your advice to get the unit to a qualified person for checking.

I did see one ref that testing for voltage too is ok but one needs specialised equipment to test for loading as I know it is one thing to have volts but without current - pretty pointless really eh?
This was apparent just recently when my old tester machine kept dying on me and the volts ca,e up ok but obviously something was failing maybe those large caps because as soon as I stuck in an old recycled Coolermaster it just took off. Before it was getting slower and I suppose in hindsight that might have been a warning sign.

My next fiddle is to make a bench tester out of one because I want to try elector plating some heatsinks to improve heat removal.
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08 Dec 2012   #16
Britton30
Microsoft MVP

Windows 7 Ultimate X64 SP1
 
 

Thanks John, but that article is 9 pages to long for me to grasp, "switched mode".
My System SpecsSystem Spec
08 Dec 2012   #17
ICIT2LOL

Desk1 7 Home Prem / Desk2 10 Pro / Main lap Asus ROG 10 Pro 2 laptop Toshiba 7 Pro Asus P2520 7 & 10
 
 

Quote   Quote: Originally Posted by Britton30 View Post
Thanks John, but that article is 9 pages to long for me to grasp, "switched mode".
Ok mate I'll pick the eyes out of it if I can
My System SpecsSystem Spec
11 Dec 2012   #18
Indianatone

Windows 7 x64 Ultimate and numerous virtual machines
 
 
Part One Why, What and who needs it?

Hi,
First of all to be here you must have an interest in computers and to some extent power supplies. This is meant to be a simple layman’s explanation as to how and why we use Switched Mode Power Supplies in modern electronics and in particular computers. I have made this simple by request; there are far more detailed explanations available in your favorite search engine. This is meant to be easy.
First some history.
Many years ago in the 1950’s most electronics in the home was made featuring valves or tubes. There was no regulated power supply. One side of the AC mains was connected directly to the chassis and the supplies to the various stages were made usually by resistors dropping a rectified DC voltage to the required voltage. The rectifier was at one time a valve and needed to warm up. The resistors gave off a large amount of heat and were often called “droppers” in the trade. If the mains voltage went down or up the picture got bigger, brighter, smaller darker and the volume wandered around. This was the only way of doing this until the solid state revolution arrived. It was also lethal, if the plug was wired wrong the chassis was live and killed plenty of people.

Transistors could be used to regulate the supplies which was especially important in the early days of colour TV. The first switching power supplies I came across used SCR’s or thyristors to take a chunk of the positive side of the AC voltage and rectify it. This was a great step to prevent picture sizes and sound levels wandering around all over the place. The problem was that all the power supplies were taking a chunk out of the positive side of the AC only and this led to potential differences on the AC neutral return lines which the power companies were not happy about. Plus when the SCR went short it usually took the plug out the wall and threw a breaker.

Along came Switched mode power supplies.
These first appeared in expensive TV sets. Basically the power supply became a very regulated affair. The brighter the image or the louder the sound the picture did not budge and the audio did not clip (within limits there was always some deaf blind old git that managed it).
They also became safer. TV’s were still dangerous to work with as this kind of power supply was not yet fully isolated.
VCR’s came out in the late 70’s. These at first had huge mains transformers which completely isolated the unit. They were safe to work on and the only dangerous place was the input fuse and the live side of the transformer. When these machines cost many hundreds or even over a thousand (JVC front loader was at one time the most complex home electronic device ever made) a costly mains power transformer was something the manufacturer could afford and since all the power supply rails were low voltage they used what was called series regulators. Usually a couple of transistors and a zener diode and sometimes a power regulating voltage specific IC to set the required voltage. VCR’s as all but the youngest of us will remember got lighter and cheaper with more and more features. TV’s got more and more features, got bigger and heavier. The need to connect your TV to the VCR, camcorder meant that you must have an isolated power supply.
This is where and when Switched Mode power supplies come into their own and surpass all others. Normally the more power you need the bigger and bigger the transformer you need, they get heavy and expensive fast. With a Switched Mode Power supply if you switch at a faster rate (higher frequency) the smaller the transformer and higher the current. This means we can have a powerful power supply in a little box rather than wheel it around in a cabinet. Also the design was tweaked to give us a HOT side (the AC input side and LIVE) and a cold side, perfectly safe to plug in our new camcorders and VCR’s and Amiga computer etc. An important factor at this time was TV’s started to use microprocessors and needed very stable supplies and even a supply when the unit was in standby.
This is why we use Switching power supplies in most electronics. They are efficient, safe (modern designs shut down in the case of a short or no load) and can run in a very low power mode for standby. Although most of us never give them a second thought without this we could not use computers today. I'll write a simple explanation how a switched mode power supply actually works with some simple diagrams next time.
My System SpecsSystem Spec
11 Dec 2012   #19
Britton30
Microsoft MVP

Windows 7 Ultimate X64 SP1
 
 

This is a great start Tony! SCR=Silicone Controlled Rectifier or Semi-conductor Rectifier?

I think here in the US we always called vacuum tubes just "tubes" while the English call them "valves". I remember as a boy waiting to see the tiny red glow to come on in the back of the TV or radio.

Let's see if I'm getting it. Switched mode means rapidly turning a large power source on and off so it effectively becomes a smaller power source, is that it?
My System SpecsSystem Spec
11 Dec 2012   #20
Indianatone

Windows 7 x64 Ultimate and numerous virtual machines
 
 

SCR silicon controled rectifier or thyristor (common name) It has an anode and cathode like a normal diode with a "GATE" to switch the device on.
The answer to your second comment is basically yes, we switch a transistor on and off at a high frequency (32KHZ) and this creates a back electomotive force (EMF) in the secondary side of a transformer and we rectify that voltage to supply our circuits. Wait for part 2.
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 How do PSU's work?




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