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A glossary of common power supply terms

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a b ) Power supply
March 30, 2010 10:29:19 PM

80Plus - The official explanation is here.
80plus.org certifies power supplies to be at least 80% efficient at room temperature. The more efficient a power supply is, at various loads, the higher the certification... 80plus, 80plus Bronze, 80plus Silver, 80plus Gold. It should be noted that real world operating temperatures are not always ideal, so the efficiency found in the 80plus labs may not be what the user experiences, depending on the PSU. 80plus certification also indicates the PSU is capable of its rated power, at 25c. (Example: The PSU received 80plus Gold certification.)

Amps - common abbreviation for amperes.
Ampere is the measurement of the flow of electricity. In simple terms you could think of it as the gallons per minute coming out of your garden hose, but not the FORCE of the water, that's different (volts). (Example: These PSUs can all produce at least 32 amps on the 12V rail.)

APFC - Active Power Factor Correction
This helps define your power supplies relationship with the power grid. It doesn't do much for you personally unless you live in a country that requires it. However, it does help reduce the strain on your electrical utility company, and so the environment indirectly. These days, any PSU without APFC is probably very old or very cheap (and not sold in Europe). Power supplies with APFC have no voltage selection switch on the back, because they don't need it.

Caps - Capacitors
What a capacitor does is probably beyond the scope of this glossary. In a power supply, it often looks like a little can of varying size, on two legs. Caps have to be able to do their job for long periods under a certain amount of heat. If they fail or are insufficient for their assigned task, they can cause problems. It's easy for an expert to look at the brand of capacitor and what it is rated for, when determining how good a PSU should be. Thus, you see capacitors mentioned in good reviews of PSUs often.

Crossload
A large load is placed on a single rail with very little load on another, often done in extreme power supply tests. Another indicator of quality.

Group regulated
The rails are controlled as a group so a larger load on one rail can affect the voltages on other rails. Cheaper to produce but can go out of spec on extreme crossloads.

Heatsinks
A heatsink is a device that conducts heat away from something, usually transferring it to the surrounding air. Various parts inside your PC need to have heatsinks because they produce a lot of heat. Your PSU will have heatsinks inside for the same reason, and will almost always use a fan to keep the heatsinks cool. Most often the heatsinks in your PSU will be made from aluminum.

Independently Regulated Rails
The load on one rail will not effect the voltage of the other.

Modularity
In a modular PSU, the extra cables can be removed to eliminate an ungainly clump of unused cables. Fully modular is when all the cables can be removed. Hybrid or partially modular is when some important cables, such as the cpu power and 24pin motherboard power cable are hardwired, while the rest of the connections are modular.

OEM - Original Equipment Manufacturer
Most PSU companies do not make the PSUs they sell. Knowing who actually made a PSU can sometimes help you decide if it's likely to be a quality unit or not.

PCB - Printed Circuit Board

Primary Circuit
Takes the 60Hz AC input, filters, rectifies, and converts it into a much higher frequency to feed into a PSU's transformer(s).

PSU - Power Supply Unit
The PSU in a modern computer converts power from the alternating current found at the wall into direct current. It outputs three kinds of direct current: 12V, 5V, and 3.3V. (Example: This PSU can produce up to 70 amps on the 12V rail.)

PUC This refers to a design by the OEM Channel Well Tech (CWT). It's used for larger power supplies where completely separate 12V sources are included in one PSU. An internal shot of one of these looks like two power supplies on one PCB.

Rail
This has meant various things in the past in regards to a power supply. Here we mean a separate channel for electricity produced by the PSU. There are always at least 5 rails on every PSU: +12VDC (VoltsDirectCurrent), -12VDC, 5VDC, 3.3VDC, 5 VSB (VoltsStandBy) Sometimes, more than one +12V rail is used. Sometimes, a PSU seller will claim to have more than one 12V rail, but really it's just one that has been split. For 12V rails to be real, they have to have something separating them, like independent over-current protection. Some PSUs have very separate sources inside the PSU for the 12V power, and these have been called "true independent 12V rails" or something like that.

Regulation - voltage regulation
A power supply needs to provide voltage that falls within a certain range. It must do this at all the various loads it's going to receive. This range is + or - 5%. So for instance the +12V rail is allowed to be anywhere from 11.4V to 12.6V. That does not mean you want such a loosely regulated PSU.

Ripple
Ripple (fluctuations) and noise (spikes) are undesirable AC currents remaining in a power supplies DC outputs. Ripple decreases the lifespan of the capacitors and increases voltage instabilities in the high speed and very low voltage circuitry in today's computers.
The ATX specification for allowable ripple is measured in mV, or millivolts. A millivolt is 1/1000th of a volt. The spec is 120mV for all the 12V rails, and 50mV for the others... but the lower the better of course.


Secondary Circuit
The "low voltage" area of the PSU, where the voltages your PC needs are produced, and load monitoring is done to see how high the duty cycle on the Primary side needs to be to meet the demand.

Soldering
Solder is made up of tin and other metals. It has a low melting point and is used to bond metal pieces together. Because it can be very conductive, it is used a great deal on circuit boards and wiring. The prickly silver dots on the bottom of the psu's circuit board are solder, for instance.

Transformer
"Transforms" an oscillating input voltage into a different output voltage using principles discovered by Michael Farraday that link magnetism and electric currents; each can induce the other. They are not the most efficient devices, particularly at low frequencies, which is why a modern switching PSU uses much higher frequencies than the 60Hz (or 50Hz in Europe) that comes over the mains.

Volts - It's the measure used to describe the difference of electrical potential, but you can think of it this way: If you turn your garden hose on and then put your hand over the end, the amount of pressure or force trying to push your hand away would be like volts. The amount of FLOW out of the hose would be like amps.


Watts - Also wattage.
A measurement of energy conversion, meaning when energy is converted to work or another form of energy such as heat.
When we talk about wattage of a PSU, we are talking about the total amount of work it can do. Volts multiplied by amps equals watts, or V x A = W.
PSUs are commonly categorized by total watts available. Some companies give the max possible watts, while other companies give the continuous watts. This means their PSUs can operate all the time providing that many watts.
However, a PSU might be able to do work that you don't need. Perhaps a lot of it's rated work comes from the 5 volt variety of power... not so useful for your gaming computer.
This is why there is a new trend to discuss PSUs using the 12 volt amps - the amount work the PSU can do using 12 volts.
a b ) Power supply
March 30, 2010 10:31:33 PM

Feel free to contribute, criticize, etc :) 

Remember, this is to be a NON-TECHNICAL reference. Hi-falutin' techno-speak is not allowed.
a b ) Power supply
March 30, 2010 10:38:46 PM

Nice! We could use a copy of this in the "Homebuilt systems" forum.
Related resources
a c 122 ) Power supply
March 30, 2010 11:33:26 PM

My understanding is that Active Power Factor Correction has to do with the PSU's apparent load on the mains being consistent with its actual load on the mains. In an AC signal, the voltage and current should oscillate in sync with one another. A side effect of Active PFC is that it eliminates the need for a voltage switch. Here's a link into an excellent tutorial article: http://www.hardwaresecrets.com/article/181/10
Here are a few of the other ones:

PCB = Printed Circuit Board.
Transformer: "transforms" an oscillating input voltage into a different output voltage using principles discovered by Michael Farraday that link magnetism and electric currents; each can induce the other. They are not the most efficient devices, particularly at low frequencies, which is why a modern switching PSU uses much higher frequencies than the 60Hz (or 50Hz in Europe) that comes over the mains.
Primary Circuit: takes the 60Hz AC input, filters, rectifies, and converts it into a much higher frequency to feed into a PSU's transformer(s).
a b ) Power supply
March 30, 2010 11:54:28 PM

I see jtt, my statement isn't exactly false, but it does lead to a false conclusion. A bit too simple. I'll have to work on that... Think I have it.

Thanks for the definitions too, we can use those but I think we'll need a simplification after the Primary Circuit def.
a b ) Power supply
March 31, 2010 9:12:22 PM

More added, corrections made.
a b ) Power supply
April 1, 2010 12:33:39 AM

Modularity- if a power supply is modular, theextra unused internal cables can be removed also at the psu end to eliminate an ungainly clump of unused cables. Fully modular is when all the cables can be removed. Hybrid or psrtially modular is when some important cables, such as the cpu power and 24pin motherboard power csble are hardwaired, while it still has modular connectiond for the rest.
a b ) Power supply
April 1, 2010 12:36:26 AM

Thanks shovenose, I'll dress that up a bit and use it.
a b ) Power supply
April 1, 2010 1:01:01 AM

heatsinks-metal things attached to the mosfets (Metal Oxide Semiconductor Field Effect Transistors) to direct the heat away from the mosfets. these are a little different in every psu, but they are generall a silver in color. the more surface area, the better the heatsink. psus also usually have a fan to aid in keeping the insides of the psu cool so that the heatsinks can dso their job. the heatsinks in a psu are similar in conecpt to those on ur cpu, graphics card, and motherboard chipset. Caution: some psu jeatsinks are part of a circuit on inside the psu, so removing them may cause damage to the cpu. also, touching themcan give you a nasty and potentially fatal shock. there are fanless psus out there, but they are very expensive. or you can do this:
http://www.silentpcreview.com/article80-page1.html
LOL!
a b ) Power supply
April 1, 2010 1:03:30 AM

Soldering-the prickly silver dots on the bottom of the psu's circuit board is solder. it is used to permanently create a good electrical connection for the compnents. you can find it on motherboards and most other circuit boards. beware: it is prickly sometimes! to apply solder, you need solder and a soldering iron.
a b ) Power supply
April 1, 2010 1:10:01 AM

caps- short for capacitros. these are like high-voltage batteries of varying shapes, sizes, and power. do not underestimate them , they can carry lethal voltage, especially the small ones. that is why it is not recommended to open ur psu (plus it ends the warranty. sometimes, if cheap capacitors are used, they can fail. ihgh-end capacitors are designed as "solid capacitors" where they have a hard shell instead of the typical metal top... im not sure if this actually helps though...
http://badcaps.net/pages.php?vid=4

also, i suggest you add descriptions of the typical connectors provided by atx psus.
a b ) Power supply
April 1, 2010 1:14:02 AM

A bit more info than is needed.

I'll go with something like this:

A heatsink is a device that conducts heat away from something, usually transferring it to the surrounding air. Various parts inside your PC need to have heatsinks because they produce a lot of heat. Your PSU will have heatsinks inside for the same reason, and will almost always use a fan to keep the heatsinks cool. Most often the heatsinks in your PSU will be made from aluminum.
a b ) Power supply
April 1, 2010 1:18:55 AM

ok then its ur guide/thread. do what you want with what i wrote...
a b ) Power supply
April 1, 2010 1:25:07 AM

I also used a bit of your solder description ;) 
a b ) Power supply
April 1, 2010 1:47:15 AM

whats puc?
a b ) Power supply
April 21, 2010 7:10:46 PM

Bump, I actually forgot I was working on this :p 
a b ) Power supply
May 24, 2010 8:26:36 AM

Bump!
a b ) Power supply
June 2, 2010 3:36:00 AM

Someone give me a good simple definition of Secondary Circuit :p 
a c 279 ) Power supply
June 2, 2010 4:23:51 AM

I would add to the 80plus part that it tests them at 100% load which weeds out those that cant even provide full power at 25C.
a b ) Power supply
June 2, 2010 4:27:05 AM

Done!
a c 279 ) Power supply
June 2, 2010 4:37:48 AM

Might want to add in

independently regulated - each rail's voltage is controlled independently and dont affect each other

group regulated - rails are controlled as a group so a large load on one rail can affect the voltages on other rails. Cheaper to produce but can go out of spec on extreme crossloads.

Crossload - Large load on a single rail with very little load on another, often done to the extreme test power supplies.
a b ) Power supply
June 2, 2010 7:08:33 AM

Excellent, done.
a c 144 ) Power supply
June 3, 2010 12:07:43 PM

Proximon said:
Someone give me a good simple definition of Secondary Circuit :p 

Something like:

Transformers have an input, or primary section and an output or secondary section. Rectifier (diodes) and voltage regulators are part of the secondary circuits.

Rectifiers (diodes) change ac to dc.

Transformer
"Transforms" Changes (maybe) an oscillating input voltage into a different output voltage using principles discovered by Michael Farraday that link magnetism and electric currents; each can induce the other. They are not the most efficient devices, particularly at low frequencies, which is why a modern switching PSU uses much higher frequencies than the 60Hz (or 50Hz in Europe) that comes over the mains.

I have a quibble with that. A well designed 60 Hz power transformer is 99% efficient. The real problem is that, at such a low frequency, it uses a lot of copper and steel.
a c 122 ) Power supply
June 3, 2010 4:33:06 PM

Point taken about efficiency, but an efficient transformer would have to be huge, and therefor expensive and impractical.
For rectifiers, I think it is important to note that they pass one half of an AC waveform, so what you get out of one is PULSED DC; i.e. "A rectifier converts an AC input into a pulsed DC output." A full-wave bridge rectifier is actually four diodes, arranged to capture both halves of the AC input waveform, but it is still creating a pulsed output. Capacitors are needed to clean it up; flatten out the pulses. That's another reason you want a high frequency; otherwise you'd need very big capacitors and excess input capacity to avoid extreme voltage drop under load.
a b ) Power supply
June 3, 2010 9:07:57 PM

That's interesting. I'll have to go back and re-read the old Navy books I have been studying.

This is hard because it's the point where I really need to throttle down the technical stuff in the glossary. I'm really looking for a very simple definition, something like "that part of the PSU which comes after the transformer and provides the final version of power used in your PC".
a c 122 ) Power supply
June 3, 2010 11:10:16 PM

The secondary does so much though, but you could just say it's the "low voltage" area of the PSU, where the voltages your PC needs are produced, and load monitoring is done to see how high the duty cycle on the Primary side needs to be to meet the demand.
a b ) Power supply
June 4, 2010 12:52:45 AM

Yes, now that's more like it :)  I'll get that in a bit later tonight, or at least incorporate it in the final def.
a b ) Power supply
March 19, 2012 3:13:39 AM

shovenose said:
heatsinks-metal things attached to the mosfets (Metal Oxide Semiconductor Field Effect Transistors) to direct the heat away from the mosfets. these are a little different in every psu, but they are generall a silver in color. the more surface area, the better the heatsink. psus also usually have a fan to aid in keeping the insides of the psu cool so that the heatsinks can dso their job. the heatsinks in a psu are similar in conecpt to those on ur cpu, graphics card, and motherboard chipset. Caution: some psu jeatsinks are part of a circuit on inside the psu, so removing them may cause damage to the cpu. also, touching themcan give you a nasty and potentially fatal shock. there are fanless psus out there, but they are very expensive. or you can do this:
http://www.silentpcreview.com/article80-page1.html
LOL!
Old thread, I know. But I... touched a PSU heatsink while it was plugged in...
:ouch:  It really, really hurt. It wasn't fatal, but damn, it was huge. The wall outlet shut down on me...


Anyways... could someone explain the myth of modularity? I heard modularity sacrifices some performance. Is that true? If so, could someone explain why that is? I heard a few manufacturers built something that will get around that, I think it was the XFX Core.

EDIT: Will I die from the shock? It's been a day, I have no burns, I can touch people without killing them lol, and I can touch metal objects just fine.
a c 279 ) Power supply
March 19, 2012 3:28:23 AM

You managed to post so the shock isn't going to kill you(its an instant kill if its going to) but you may see some burns show up under your skin in a few days, the current travels through the blood vessels not along the surface so it can leave interesting results.


As for the myth about modularity sacrificing efficiency, it is true. Every connection in a wire provides resistance, the connectors are not nearly as conductive as we would like so they do cause some power loss; however, you are already losing more power to the length of the cable and the connection to the board than you do to the connection to the PSU. Jonnyguru did a test of this a few years ago, here is the article
http://www.motherboards.org/articles/guides/1488_1.html

A quote from his conclusion sums most of it up nicely.
Quote:
Someone once said that a modular connector's pins have as much resistance as two feet of wire. I can't recall where that came from, but I think our five subjects have shown us that there's actually as much as four times as much voltage lost in a mere 18 inches of cable than there is in a modular connector. And when thinking about a loss in voltage in a modular connector, one shouldn't look just at the fact that a power supply has a modular connector, but perhaps how that modular connector is made.
a b ) Power supply
March 19, 2012 4:03:36 AM

hunter315 said:
You managed to post so the shock isn't going to kill you(its an instant kill if its going to) but you may see some burns show up under your skin in a few days, the current travels through the blood vessels not along the surface so it can leave interesting results.


As for the myth about modularity sacrificing efficiency, it is true. Every connection in a wire provides resistance, the connectors are not nearly as conductive as we would like so they do cause some power loss; however, you are already losing more power to the length of the cable and the connection to the board than you do to the connection to the PSU. Jonnyguru did a test of this a few years ago, here is the article
http://www.motherboards.org/articles/guides/1488_1.html

A quote from his conclusion sums most of it up nicely.
Quote:
Someone once said that a modular connector's pins have as much resistance as two feet of wire. I can't recall where that came from, but I think our five subjects have shown us that there's actually as much as four times as much voltage lost in a mere 18 inches of cable than there is in a modular connector. And when thinking about a loss in voltage in a modular connector, one shouldn't look just at the fact that a power supply has a modular connector, but perhaps how that modular connector is made.
:cry:  Will I burn up to my death? or will my blood vessels explode? or implode into a black hole destroying everything in the universe?

What burns? I'm a bit scared now... Will the burns hurt?

As for the modularity, does that mean modularity has more pros than cons than a directly connected system?
a c 279 ) Power supply
March 19, 2012 11:11:24 PM

You will be fine, don't worry about it. All the damage that would have occurred has already been done. You might be a bit tender in that area but if it doesn't hurt right now it won't hurt much if any.

As for the modularity, i dont think you can really say either way, it is true that modular connectors do introduce more voltage drop and another failure point for the cable that fixed units do not, and the benefits of modularity really depend on the user and the system its going in. Having the main 24 pin and 8 pins be modular doesn't gain you anything since they need to be used at all times anyway so i would actually say hybrid/semi-modular is the best option since you really don't need everything to be able to disconnect.
!