Talk:Power supply

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This article was nominated for deletion on 24 May 2006. The result of the discussion was Keep, nomination withdrawn.

Contents 1 Merge Complete 2 Wall wart 3 Truth in labeling? 4 Requested move 4.1 Survey 4.2 Discussion 5 Question 6 Full range 7 Article lack information 8 Dangerous to open a PSU 9 Split out Computer power supply 10 Some info regarding the various types of transformers/power-supplies 11 External link 12 Uses in aviation 13 Obfuscatory section heading: "Domestic mains adapter"

[edit] Merge Complete

I merged the article electronic power supply into this one, as suggested by another Wikipedian. The electronic power supply article now redirects to this one.

I didn't spend a ton of time with the merge, so I'm sure there will be some small edits that need to be made.

Enjoy! --smileyborg 04:37, 24 May 2006 (UTC)

[edit] Wall wart

I dont think this slang term is suitable for inclusion in an encyclopeida. Try 'battery eliminator' or AC to DC converter instead. Light current 00:00, 3 September 2005 (UTC)

Neither of those terms have the same meaning as wall wart. There doesn't seem to be any concise term that isn't slang and has the exact same meaning. Plugwash 00:51, 10 September 2005 (UTC)

The term is very common and fine for inclusion. Omegatron 16:05, 6 April 2006 (UTC)

I've never personally heard the term but I don't really object to it being on here. Smileyborg 02:08, 24 May 2006 (UTC)

I've never heard of the term Wall wart. I first thought that said Wall Mart. Any other words for wall wart? Colinstu 14:58, 07 July 2006 (GMT -6)

I agree it's a bit of a silly term but it's what I typed in to find this article, so I'm glad it's there. XavierBlak 14:36, 14 September 2006 (UTC)

Wall wart should definately be included as a disparaging name for these devices when wallmounted. However, the text, which implies any xformer/powersupply is a "wall wart" should be edited to also define such devices that have two cords (one the plugs into the wall, and one that plugs into the device). The geekslang for these units is "line lumps".

[edit] Truth in labeling?

I'm a little confused about them, though. If you measure a 9 VAC wall wart output unloaded, for instance, you get something like 11 V_RMS = 15 V_peak = 31 V_P-P, none of which are "9 VAC". It usually doesn't matter because of regulation, but is the printed number just a ballpark figure? Is there some rhyme or reason to the markings? Maybe the amount they can output under a certain load? — Omegatron 16:05, 6 April 2006 (UTC)

It's likely that they typically deliver n VAC when loaded to the rated m amps of load current. As you oserve, the unregulated ones have pretty poor load regulation (and, of course, no line regulation). On the other hand, more and more of the DC power bricks use offline switchers to do the conversion and these usually have pretty good load and line regulation.

I was struggling with this problem of poor load regulation the other day: some quartz halogen lighting that I'm trying to install was supplied with a wall wart power transformer, but that transformer has the typical poor load regulation of such things, so when I wanted to connect just one lamp to the transformer (rather than the supplied two lamps), it was obvious that the one bulb was running on a significant overvoltage. I'm probably going to switch to a much-more-expensive offline switcher "transformer".

Atlant 19:19, 6 April 2006 (UTC)

It's likely that they typically deliver n VAC when loaded to the rated m amps of load current.

That's so obvious I didn't even think of it. I figured it was something like that. :-) — Omegatron 20:12, 6 April 2006 (UTC)

Exactly right:

• "Most wall-mount power supplies have no active regulation. They are designed so that the voltage will be X when the current is Y, just like the label says. Many engineers are confused by this, thinking that a 12 volt, 1 amp power supply can be substituted for a 12 volt 500 mA power supply. This might be true, but the voltage at 500 mA will be higher than the voltage at 1 amp. How much this varies depends on the load line of the transformer." [1]
• "For a regulated constant voltage power supply, this attitude is just fine, but for the unregulated fluctuating voltage WW, it is not. The two numbers given on the WW must be taken together!
  
  We can see that the lower the current draw from the WW, the higher the voltage." [2]
• "One thing they almost never have is voltage regulation, and that’s very important to understand, since it can create questions and concerns… like: How come I’m reading 20+ volts from my 15 volt wart? Will it damage my xxxx? Is it defective? Actually, it’s perfectly normal. Let’s see why…
  
  Any time we have current flowing through a normal conductor there is a voltage drop. More current, more voltage drop – as stated by Mr. Ohm’s famous law. And the wire used for the windings of your wall wart's transformer is no exception. I have a shiny new "AC adapter" rated at 15 volts DC at 500 mA right here on the bench. What happens when I plug it in to the 120 volt outlet and measure the output? About 20.3 volts, that’s what. So... what’s going on? Did they miss the specified voltage by over 30%? Nope…" [3] — Omegatron 21:49, 6 April 2006 (UTC)

[edit] Question

"In portable computers there is usually an external power supply that produces low voltage DC power from a mains electrical supply (typically a standard AC wall outlet) to charge the batteries inside the computer. The computer itself runs from the batteries." Considering I can pull out the battery and use just the adaptor and I can't turn on the computer without the battery if not plugged in of course, how can this be true? Also with computer power supplies, does anyone know what makes this power suitable? What makes it different from AC (besides it can be used for standby and such)? Basically, what EXACTLY happens inside of a PC power supply? User:Tatsh 20:52, 27 May 2006 (UTC)

• I don't know exactly what happens, but I know at least one reason direct AC isn't used - computer PSUs regulate the amount of power going to componants. For one thing they have to provide just the right amount to each part. 1.8v to the ram, that sort of thing. Too much and it'll fry, too little and it'll crash. So a PSU controls the fluctuations in the power, helping system stability. Kind of like a UPS does, though on a much smaller scale (and without the battery of course) -Goldom 莨夊ｩｱ 謚慕ｨｿ 05:16, 28 May 2006 (UTC)
• As I understand it (and this is just what some guy at Best Buy told me, so take it as you will), you can run your laptop without the battery, but it isn't recommended. Without the battery, power fluctuations can be harmful; say, the power drops for a second, the arm on your hard drive drops and scratches the disc. I'm not sure how true this is (because it seems to me that the system would die the moment it loses any power at all, as Goldom mentioned with ram), but I'm pretty sure a laptop does run off of the battery whenever it has one. ~ Booya ^Bazooka 16:14, 29 May 2006 (UTC)
  • I don't buy this (btw my laptops battery pack has been totally dead for years), it would be pretty suicidal for a manufacturer to make something with a user removeable battery pack and no warnings against removing it that couldn't safely run without it. Plugwash 16:18, 29 May 2006 (UTC)

I agree with User:Plugwash, of course a laptop with the battery removed is more vulnerable to filesystem corruption etc in the event of power loss but no more so than a normal desktop system without a UPS. --Ali@gwc.org.uk 16:23, 29 May 2006 (UTC)

I agree with the above. The other thing is that Li-Ion batteries are better able to avoid data corruption compared to alkaline. User:Tatsh 22:35, 5 June 2006 (UTC)

• On the first question of whether laptops draw from the battery or from the adaptor, I'm not 100% sure, but my best guess is that if both are present, the laptop draws from the battery, and the battery is charged by the power adaptor. If only one is present, there is (obviously) no other possibility. On the second question as to what a computer power supply actually does, its main function is to convert AC power to DC power, and lower the voltage from 120 V to amounts such as 3 V, 5 V, or 12 V. The components of the computer are designed to accept a narrow range of voltages (for example, a hard drive may only operate on power within 11.2 V to 12.8 V). (This is what all electrical power supplies do.) It also does "smooth out" fluctuations in the regular mains power, so that there is a steady amount of power going to the delicate components of the computer. One last function of the computer PSU is to circulate air, as typically the power supply contains one or more fans that exhaust air out of the case. --smileyborg 04:32, 30 May 2006 (UTC)
  • You can't draw from and charge a battery at the same time. Either electricity is flowing into the cells of the battery or its flowing out of them. The battery could however by contributing to the smoothing (e.g. charge/discharge status switching quickly) but i doubt it would actually help much (as you have to go through all the batteries protection circuits internal resistance etc) and i guess in a badly designed laptop running every device could overload the external power and drag it down to the point where your on batteries only. Plugwash 00:27, 31 May 2006 (UTC)
    • Good point. So then, the power must be diverted either to charging the battery if needed and/or powering the laptop if it is on. --smileyborg 01:20, 31 May 2006 (UTC)

I don't buy that at all. I've been running a laptop without a battery for a few years. — Omegatron 02:28, 31 May 2006 (UTC)

I also don't buy it. And for the above, don't listen to anything Best Buy tells you. Obviously they wanted to make sure you buy a battery right away from them and never use it without the battery in (quite possibly limiting lifetime with the heat). The computer power supply section is much better compared to 27 May 2006. :)--User:Tatsh 22:38, 5 June 2006 (UTC)

[edit] Full range

What does "full range" mean in the context of personal computer power supplies?—The preceding unsigned comment was added by 66.74.136.58 (talk • contribs) .

Can you supply some context for your question? For example, a sentence using the term?

Atlant 12:12, 9 June 2006 (UTC)

On the back of the power supply there is a sticker that says "FULL RANGE" instead of a recessed red switch. Manufacturer is Zalman, model is ZM400A-APF.

I would imagine that it means that the input voltage range the PSU can accept goes from the North American 110V / 60Hz to the European 220V / 50Hz without obligating the user to flick a switch on the unit. Much safer to have the PSU detect and adapt automatically since end users may be unaware and incurr damage if the switch is set incorrectly. --Hooperbloob 03:27, 10 June 2006 (UTC)

[edit] Article lack information

It doesn't talk about efficiency. It doesn't talk about PFC/AFC, Passive/Active stuff.

[edit] Dangerous to open a PSU

In the 4th paragraph under the sub-topic "Computer power supply", it says that: "It is dangerous to open a power supply while it is connected to an electrical outlet as high voltages may be present even while the unit is switched off.". Actually, the danger presents under ALL circumstances, since the capacitors inside the PSU may store lethal charges, which may last for a long time after the PSU is removed from a power outlet.

I thought all modern PSUs were built to self discharge pretty quickly on removal of power, i could be wrong though. Plugwash 17:32, 30 July 2006 (UTC)

Bleeder resistors fail too ;-) .

Atlant 21:05, 30 July 2006 (UTC)

[edit] Split out Computer power supply

Most of the article covers different types of power supplies from an electrical perspective, rather than an application perspective, since power supplies are used in so many applications. Unless there's something electrically unique about a computer PSU, I propose it be moved to something like computer power supply, or merged with the info at ATX or something like that. (even if there is something electrically unique, the current text mainly just covers application-specific info like what connectors happen to be attached to the PSU). --Interiot 20:44, 28 September 2006 (UTC)

I agree, Computer power supply should be a differnt page with a link in Power Supply Joey.dale 19:39, 29 September 2006 (UTC)

I agree too. I'll create a new article and move the information if no one objects. -Etienne 20:23, 30 September 2006 (UTC)

Support per nom. Jay Kana 14:21, 6 October 2006 (UTC)

Support makes stacks of sence, and will work better with my work on computer hardware --TheJosh 06:20, 11 October 2006 (UTC)

Support its exactly what I was searching for Jimmy Tseng 11:55, 13 October 2006 (UTC)

Comment The only things that make PC PSUs notable as power supplies (that I can think of, anyway):

• They have a fairly standardized form-factor and pinout (two main pinouts as I understand it)
• They are multiple output but tend to regulate just one voltage (either +5 or +3.3), allowing the others to vary ratiometrically with the regulated voltage.

Support with name change An article about personal computer power supplies could delve into the specifics of pinouts, voltages, watts, physical packaging, cooling, etc. and all those other issues that don't belong here in the generic "power supply" article. But I'd only support this change if the article was specific to PC power supplies. There are plenty of other "computer power supplies" out there in the world that are vastly different from the generic boxes that you buy down at Ye Olde Byte Shoppe. Atlant 13:21, 13 October 2006 (UTC)

Support Along the same lines as Jimmy Tseng, [computer power supply] was exactly what I was looking for. I am going to make the move, considering strong support for the idea. --Ritz 05:25, 23 October 2006 (UTC)

[edit] Some info regarding the various types of transformers/power-supplies

According to the international standards (IEC) as listed on www.iecee.org, which are responsible for the international safety and performace requirements of such products, tranformers/power-supplies can be divided into the following categories:

For general use (IEC 61558):

• Separating transformers for general use (normally wound coil magnetic transformers)
• Control transformers
• ignition transformers for gas and oil burners
• isolating transformers
• shaver transformers and shaver supply units
• safety isolating transformers
• bell and chime transformers
• transformers for class III (<50V) handlamps for tungsten filament lamps
• contant voltage transformers
• auto-transformers
• variable transformers
• isolating transformers for the supply of medical equipment
• transformers for switch-mode power-supplies
• switch mode-power supplies (electronic)
• attenuation transformers
• pertubation attenuation transformers
• small reactors (also includes coils)
• transformers for construction sites

Power-supplies for IT equipment (IEC 60950)(includes PSU's)
This includes both magnetic wound transformers and electronic switch-mode power supplies. Most power-supplies for computers are tested according to this standard.

Transformers for audio/video equipment (IEC 60065)
Similar to IEC 60950

Battery chargers (IEC 60335-2-29)
Similar to IEC 60950

Electronic step-down converters for filament lamps (IEC 61347-2-3)

• Usually only switch-mode
  
  

Also it is worth mentioning other types of power-supplies such as:

• High voltage power-supplies (electronic or magnetic)
• Step-up power supplies (electronic or magnetic) for use in caravans, boats etc.
  
  

There might be other types of power-supplies that are covered by the american UL-standards. Please discuss.

[edit] External link

Google has a power supply directory; http://dir.google.com/Top/Business/Electronics_and_Electrical/Power_Supplies/

[edit] Uses in aviation

This section contains some imaginative overstatements, to be charitable. In virtually every "jet transport" the engines are started by compressed air (also called "bleed air") which comes from the other engines. This air is piped to pneumatic starters on each engine. Ground start capability is provided by an auxiliary power unit (APU) which is a small turbine engine with an electric starter. This engine may be started from the main ship batteries and then provides enough compressed air to start the main engines. Jet airplanes also provide an interface to use a ground source of compressed air. This is typically an aircraft-type APU mounted on a cart.

There is nothing special about aircraft power supplies that I know of. The most ingenious thing about them is the constant speed drive or CSD, which is a mechanical drive that keeps the generators in phase and at the same speed even though the engine speed varies according to throttle setting. The generators basically supply 400 Hz AC directly to the aircraft. Generator control units will take a generator off line if there is a problem with it, but the generators are wired directly to the aircraft power bus. There are power supplies on board that provide 28 VDC but they are a pretty standard design, if of course very high quality.

There are advanced airplanes on the drawing boards, like the Boeing 787, that are planned to have electric start capability, but I don't think there are any in service yet. I may be a little behind the times on this point, as I only deal with my employer's airplanes on a daily basis.

I am serving notice that I intend to remove this entire section as being nothing but misinformation.

Writing from the Engineering Department at the American Airlines Maintenance & Engineering Center, Tex 17:40, 12 December 2006 (UTC)

I agree -- this section sounds goofy. The one thing that is unique about aircraft power supplies (in general) is the use of 400 Hz as a means of minimizing size and weight. Plus you get that great 400 Hz "whine" on the radios instead of 50/60 Hz "hum" ;-).

Atlant 17:49, 12 December 2006 (UTC)

[edit] Obfuscatory section heading: "Domestic mains adapter"

I think a heading change is required. This is called an "AC adapter" in nearly all cases where products and manuals refer to them.

Who actually uses this unusual phrase to describe what these are? It seems highly unlikely that I would ever find one person saying to another "Excuse me, but could you please hand me that domestic mains adapter?"

This terminology also implies there is some other kind of non-domestic mains adapter. What is that device called? :-) DMahalko (talk) 23:36, 22 April 2008 (UTC)

Hmm, the Google Litmus Test isn't looking good here. Eight hits total for the entire web for "domestic mains adapter" and most of those are just GNU'd copies of this page: http://www.google.com/search?q=%22domestic+mains+adapter%22

DMahalko (talk) 23:40, 22 April 2008 (UTC)