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Jorge-Vieira
10-09-15, 07:45
PSUs 101: A Detailed Look Into Power Supplies


The objective of this article is to provide detailed information about the most crucial part of a personal computer (PC) system, its power supply unit. Follow us on this journey into PSU territory and we promise that you will gain valuable knowledge.
For those of you who know nothing about PSUs, today we're taking it from the top. The abbreviation PSU stands for power supply unit, and in this article, we assume that it is also an SMPS (switching mode power supply), since in modern PCs only SMPS units are used.
You can think of the PSU as the heart of a PC; it is the most significant part of the system since it feeds power to the other components, including the CPU, graphics card, hard drive, SSD and so on. If the PSU fails, it affects all of the other pieces. And in some cases, a malfunction of the PSU can damage other components as well, especially if the PSU is of low quality with inefficient protection features. Unfortunately, this is something many builders ignore. Instead of choosing an adequate PSU for their systems, users typically acquire all of the other components first, using leftover funds for the power supply purchase. If you've made this mistake, we are sure that after reading this article you will change your PC building strategy. However, this article is not just intended for novice users and goes beyond the basics of PSUs, providing valuable information to experienced enthusiasts as well.
http://media.bestofmicro.com/X/F/505347/original/Chapter-1-Figure-1-AX1500i.jpg
In the following sections we will provide an easy-to-follow explanation of the switch power conversion. We will also make a brief reference to the most significant electronic components currently used not only in PSU manufacturing, but also in every modern electronics device. Through the following pages you will learn the basic concepts of inductors, capacitors, resistors, transistors and diodes in order to better understand PSU components. Next, the main context of switching power conversion will be explained and a brief description of the various stages that compose a PSU will be made. Afterward, we will make a brief reference to some switching regulator topologies, which are commonly used nowadays. Some of you might not be aware of this, but a PSU's cooling fan is usually the first part to stop working, at least in good-quality PSUs, so we will dedicate some time to discussing cooling fans as well. Next, we'll spend some time on protection features, and finally we will take a look at ATX, EPS and 80 PLUS specifications.
This is going to be an informative journey through electronics, and when you finish reading this article, we are confident that you will have gained valuable knowledge that will help you to better understand the "Look Inside" pages in our PSU reviews (http://www.tomshardware.com/articles/?tag=power-supplies&articleType=review). In addition, you will be able to judge the technical specifications of a PSU by yourself.
In the following section, we briefly describe the most significant electronic parts that are used in PSUs, including inductors, transformers, capacitors, resistors, transistors and diodes. This essential knowledge will help you when we analyze the internal parts of an SMPS, especially if you don't have an electronics background.



<article id="news-content" class="content innerB20 line vibrantContent KonaBody"> Inductors

An inductor, or induction coil, stores electrical energy in a magnetic field. Inductors are used in many electronics and they play an especially important role in PSUs. An inductor is simply a coil of wire wrapped around a core (composed of iron, ferrite or simply air). Depending on their usage they have several names: coils, chokes, solenoids, etc.
http://media.bestofmicro.com/X/G/505348/original/Chapter-2-Figure-1-Inductors.jpg
So how do inductors work? The whole concept is very simple: when a current passes through an inductor, a magnetic field is created around the wire. Every change in current affects the magnetic field, which in turn induces voltage across the inductor. That voltage creates a current flow opposite of the initial current. This property is known as inductance (L) and it's measured in henries, which is a quite large unit of measure usually documented in millihenries (mH) or microhenries (μH).
Here are some interesting facts about inductors:


They store electrical energy in magnetic fields.
They act as an open circuit at first when DC (direct current) is applied to them, but after a while they freely allow it to pass.
They oppose current changes.

Transformers

Now, let us take a quick look at transformers. Typically, inductors are shielded so their magnetic fields do not interact with other components in the same circuit. However, if we place two unshielded inductors side-by-side and feed one of them with AC (alternating current), then its magnetic field induces a voltage not only in the current inductor, but also in the other inductor. The process of inducing voltage in the second inductor is called mutual inductance. So if you pass current in one inductor you create voltage in the inductor near it.
A transformer is nothing more than two inductors, or coils, wound around the same core material in a way that mutual inductance is at a maximum level. The coil that lets the current pass is called a primary coil and the coil that is induced with voltage is called a secondary coil. A transformer can electrically isolate two circuits and also step voltages up or down.
http://media.bestofmicro.com/X/L/505353/original/Chapter-2-Figure-2-Transformer.jpg
</article>


Todo o manual:
http://www.tomshardware.com/reviews/power-supplies-101,4193.html

Jorge-Vieira
10-09-15, 07:47
Who's Who In Power Supplies, 2014: Brands Vs. Manufacturers


<article id="news-content" class="content innerB20 line vibrantContent KonaBody"> Do you think that all power supplies are manufactured by the brand on the label? Think again. We show what makes a good PSU and reveal who builds them. You can actually find lots of quality (instead of just scrap metal) behind some of the budget labels.
This article first appeared (http://www.tomshardware.com/reviews/psu-manufacturer-oem,2729.html) on November 12, 2010, and has since been added to and updated.
http://media.bestofmicro.com/K/D/256045/gallery/logo_w_200.png
Update, 7/22/14: Due to overwhelmingly positive feedback and a number of reader questions about the actual origin of certain power supply brands, we thoroughly revised our Who’s Who of PSUs, originally published in November of 2010, refreshed in May of 2011, and revisited in January of 2013. Since the article is frequently quoted and linked to, we’re updating it rather than publishing the newest entries. As such, much of the content remains unchanged from the previous version.
Today’s revision adds many new manufacturers and brands as well as expanding the number of models in several product families. Indeed, much has changed since our original article appeared more than two years ago, and we’re happy that readers in our forums and around the Web appear to be better informed and more discriminating when it comes to picking out a new power supply.
At the same time, manufacturers also appear to have re-evaluated some of their practices, and we’ve seen newer models use better components, resulting in higher quality overall.
We want to extend a special thanks to our community, as many of our readers and forum members have contributed much helpful information and valuable data to this analysis.
Several companies also joined in for the first time, volunteering information on their product lines. Sadly, for now it still appears that this is the exception rather than the rule. Many of our emails asking for information were met with silence. On that note, we acknowledge that we’re not infallible. Should you come across any omissions or errors, big or small, we invite you to send us your feedback so we can keep expanding and refining this list, ensuring it remains current and as inclusive as possible.
Who’s Who? Let’s start by dividing the manufacturers into three large groups so we can better understand the database and how these companies are connected:
1. The OEMs (Original Equipment Manufacturers)
OEMs manage all of their production internally. They either exclusively design and manufacture their own PSUs (like Enermax) or design and manufacture their own brands, as well as manufacture PSUs designed by other companies (such as FSP, HEC, and SeaSonic). Some of them focus heavily on worldwide exports and provide a range of models, which are then sold under different labels. It's common to find otherwise-identical models marketed under many different names and labels. The industrial areas around Shenzhen, China, are the cradle of the lowest-priced PSUs sold all over the globe.
http://media.bestofmicro.com/K/S/256060/gallery/shenzhen_w_600.jpg (http://www.tomshardware.com/gallery/shenzhen,0101-256060-0-2-12-1-jpg-.html)
2. Designers: Without Their Own Production
The second group of companies also develops and designs their own products. However, they have to outsource either some or all of the manufacturing to other companies. One example of this is Be Quiet. Those familiar with the brand noted how Be Quiet P7 models were suddenly much better than the disappointing P6. The answer was simply a manufacturer change, from Topower to FSP. Other examples of designers include SilverStone, Corsair, PC Power & Cooling, and Tagan.
3. The Labels: With or Without Any Technical Involvement
Arguably, this group could be subdivided. Some importers of foreign PSUs that resell models under their own labels have a certain influence over the quality and choice of components, while others simply bring in some very cheap products, change the label, and resell them.
This third group is the most interesting one for price-oriented customers, though also the most uncertain for quality. You're as likely to score a bargain by getting a relabeled high-quality product at a lower price as you are to be disappointed by being too tight-fisted. Some good examples of products to watch are new models from Aerocool, which are essentially the Cougar (http://www.tomshardware.com/out_click.php?id_site=18&m=925&zone=7&e=ICL_cougar&go=http%3A%2F%2Fwww.tomshardware.com%2Fbrands%2FCO UGAR%2F) units from Compucase/HEC with a discounted price and completely restyled exterior.
After many tests and inspections of budget models (by us, our readers, and friendly computer stores), we would advise you to steer your piggy banks clear of the labels Rasurbo, Inter-Tech (Sinan Power, Coba), Tech Solo, LC Power, RaptoxX, Tronje, Xilence, Ultron, World Link, Q-Tec, etc. We were able to identify some of these models without looking at the UL number (http://www.ul.com/global/eng/pages/) simply by checking out the installed components. These were almost exclusively the simplest work of such manufacturers as Enhance, World Link, Andyson, Topower, Casing Macron, and Channel Well.
Lack of protection circuits, low efficiency, and bad build quality were major points of criticism. The lowest of the low was a European label called Hardwaremania24, targeted at OEM PCs. While still in standby mode, the PSU heated to about 176 degrees Fahrenheit, spent the next six hours billowing smoke, and finally made what might be described as a trumpeting sound before dying. The host computer was never even turned on. After analyzing the PSU, we found no protection at all save for a single slow fuse.



<article id="news-content">How do you identify a bad power supply before buying it?

Extremely high wattage claims at comparatively low prices are suspicious. There are simply no decent 750 W power supplies for $50. For every product class based on performance and features, there must be a minimum price. When a product is significantly below that price, be cautious. You can get a "400 W PSU" for $20, and such fire hazards are installed in budget PCs every day by unscrupulous companies that know exactly the risk they're handing off to buyers.
Check the specifications. For example, if a PSU claims high performance on the 3.3 and 5 V rails while the 12 V rail numbers are low, then you know something is wrong.
The manufacturer does not specify any combined maximum performance, but instead only shows the maximum load for each rail separately. This is done without specifying how much real power would be available if all rails are used at the same time. Avoid PSUs without this information.
Be careful with juicy marketing expressions and commercial lingo: Super, Extreme, Gaming, Combat, etc. Using superlatives to describe something quite normal should arouse suspicion and have you double-check specification details.
Passive rather than active Power Factor Correction (PFC) leads to lower power efficiency.
Very few or short power connectors and cables might be an issue. A 750 W PSU usually has four PCIe connectors for graphics cards (2 x 6-pin and 2 x 6+2-pin), so think twice if a model only offers two (or at least consider your upgrade options).
With cheap PSUs, the quality of the cable insulation may be poor, or the cables may not be insulated at all. The power cable grommet may also be insufficiently padded.
Be careful if there are few or no indications of protection circuitry. If the PSU specification only says OPP (overload protection) or perhaps SCP (short circuit protection), this points towards a normal fuse. If the specification also says OVP (overvoltage protection), this probably means that it is equipped with a simple metal oxide variable resistor. These security measures by themselves are absolutely insufficient and cannot replace any kind of digital safety chip.

Unfortunately, you can't always tell at first glance whether you're dealing with a high-quality PSU or whether there's nothing but disappointment waiting behind the pleasant facade. Therefore, we decided to open up two budget PSUs representative of what you can find in many of today’s OEM PCs and illustrate the points and features you should be examining.
A First Look At the Inside: Primary Capacitor and PFChttp://media.bestofmicro.com/K/V/256063/gallery/supply_01_w_600.jpg (http://www.tomshardware.com/gallery/supply_01,0101-256063-0-2-12-1-jpg-.html)
First, look at the storage capacitors in the primary circuit. These act as buffers and help protect the PSU and computer from voltage fluctuations. The electrolyte used in them is key, because it evaporates or dries out through a combination of heat and time. As a general rule, capacitor lifetime is halved for each 10 degrees Centigrade increase in temperature over the specified normal load. Using higher-quality capacitors that can handle 105 degrees instead of 85 degrees (C) should almost double their lifetime, greatly contributing to the PSU's durability.
http://media.bestofmicro.com/K/U/256062/gallery/supply_05_w_600.jpg (http://www.tomshardware.com/gallery/supply_05,0101-256062-0-2-12-1-jpg-.html)
A PSU equipped with a big choke like in the photo above is a clear indicator of passive Power Factor Correction (PFC). Only more sophisticated active circuitry allows for factors close to the optimum value of 1, while passive components can reach 0.7 to 0.8 at best. The type of power factor correction indirectly suggests the expected efficiency of the power supply. Although PFC and efficiency are casually unrelated, devices with active PFC are also usually more complex and modern, meaning you're more likely to get better efficiency from them.
Protection CircuitsEven without opening the PSU, a data sheet can reveal some of the safety measures taken (or not) by manufacturers. A decent PSU should contain the following safety measures:


OCP (Over Current Protection): protection against power spikes
OVP (Over Voltage Protection)
OPP (Over Power Protection): overload protection, sometimes called OLP
OTP (Over Temperature Protection): protection from overheating
UVP (Under Voltage Protection)
SCP (Short Circuit Protection)
NLO (No Load Operation): this isn’t exactly protection in the same sense as the other features, but it allows the PSU to power up and function normally, even with no load.

Without this information, you have to look inside the PSU to find out what you need to know.
http://media.bestofmicro.com/K/Y/256066/gallery/supply_02_w_600.jpg (http://www.tomshardware.com/gallery/supply_02,0101-256066-0-2-12-1-jpg-.html)
We found no protection at all on this unit, except for a simple fuse. Sadly, this PSU is still available on the market under a couple of different labels.
http://media.bestofmicro.com/K/Z/256067/gallery/supply_04_w_600.jpg (http://www.tomshardware.com/gallery/supply_04,0101-256067-0-2-12-1-jpg-.html)
Passive components do not guarantee sufficient protection. Without a digital security chip, the computer hardware is severely exposed to risks.
http://media.bestofmicro.com/K/X/256065/gallery/supply_06_w_600.jpg (http://www.tomshardware.com/gallery/supply_06,0101-256065-0-2-12-1-jpg-.html)
The security chip PS223 from Silicon Touch is popular, and you should avoid PSUs not using it or similar products, such as the PS332S.
Cables and Short CircuitsYou can tell a lot about your PSU by looking at its internal wiring. A lack of heat shrink tubing, carelessly exposed solder joints, and components fastened with a glue gun are symptomatic of cheap and hazardous manufacturing. If unprotected cables are placed next to hot components, a PSU failure is nearly assured.
http://media.bestofmicro.com/K/T/256061/gallery/supply_03_w_600.jpg (http://www.tomshardware.com/gallery/supply_03,0101-256061-0-2-12-1-jpg-.html)
http://media.bestofmicro.com/K/W/256064/gallery/supply_03b_w_600.jpg
BoardsA final quality indicator is the circuit board material. Impregnated laminated paper (like the yellow boards in the pictures) is a sure sign of cost cutting. Fiber materials are much more durable and, perhaps more importantly, non-flammable.
</article> </article>

Todo o manual:
http://www.tomshardware.com/reviews/power-supply-psu-brands,3762.html

Jorge-Vieira
10-09-15, 07:49
How We Test Power Supply Units


The power supply unit (PSU) is the most important part of every electronic device, including, of course, computers. It is the heart of your system, since it feeds energy to the other components. Consequently, if the PSU fails, everything else fails with it. This is the reason most experienced technicians start a failure investigation from the PSU before proceeding to the rest of the components. And, consequently, this is why you should pay extra attention to your choice of PSU and not make a decision based exclusively on price. After all, a good PSU will do its job for quite a long time, far outlasting the rest of your expensive system components. To properly review a PSU, expensive equipment is required, and the reviewer needs to know not only how to operate it, but also have sufficient knowledge about electronics and a PSU's design. The knowledge part is especially crucial, since not even the most expensive equipment can make a good PSU review if the reviewer doesn't know how to properly use it and what tests to conduct with it.
In our reviews, we examine the PSU's performance, noise and temperature ratings, along with the build quality of the units. We also judge the PSU's individual components, cables, connectors and even product specifications and packaging while providing a performance per dollar comparison.
MORE: All Power Supply Articles (http://www.tomshardware.com/t/power-supplies/)
MORE: Power Supplies in the Forums (http://www.tomshardware.com/forum/74/power-supplies.html)

<section id="p2" class="line"> Test Setup Overview http://media.bestofmicro.com/D/T/509825/original/setup_new7.jpg
Currently, we use two Chroma 6314A mainframes equipped with six 63123A loads (350W each), one 63101A load (200W) and one 63102A load (2 x 100W). This setup is among the best money can buy, providing the highest possible accuracy. Chroma loads are widely used by all PSU manufacturers and are pretty much the standard for PSU measurements. Our setup allows us to stress the +12V rail with up to 2100W, 5V up to 200W, and 5VSB / 3.3V up to 100W each. All of our equipment is controlled and monitored by a custom-made software suite that's highly sophisticated.
In addition to the Chroma loads, we also use a Chroma AC source (6530), which can deliver up to 3kW of power, a Rigol DS2072A oscilloscope, a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, two Fluke multimeters (models 289 and 175), a Keithley 2015 THD 6.5- digit bench DMM and a lab grade N4L PPA1530 (http://www.newtons4th.com/products/power-analyzers/ppa1500-precision-power-analyzer/) 3-phase power analyzer along with a Yokogawa WT210 power meter.
Our testing gear also includes a hotbox, which allows us to test a PSU at high ambient temperatures. Finally, we have three more oscilloscopes (a Rigol VS5042, a Stingray DS1M12 and a second Picoscope 3424), and a Class 1 Brüel & Kjaer 2250-L G4 Sound Analyzer, which is equipped with a type 4189 microphone that features a 16.6-140 dB(A)-weighted dynamic range.
The latest addition to our testing equipment is a Flir E4 infrared camera, which through some firmware modifications (many thanks to the fine folks at EEVblog's forums for this) now delivers a resolution of 320x240 pixels. In addition, we have several soldering and desoldering stations that we use during the dismantling process of every PSU we test. Test results are one thing, while checking out the build quality of a PSU is another. Finally, if we encounter any unusual results during the testing process, we examine the internals of a PSU to find out what is causing the issues.
</section> <section id="p3" class="line"> Voltage Regulation Test A PSU should be able to keep all of its rails within some predefined voltage ranges at all cases/loads. In Table 1, you will find these ranges (following the ATX v. 2.4 specification).
DC Output Voltage Regulation
<tbody>
Voltage Name
Range
Minimum
Nominal
Maximum


+12V1
±5%
11.40V
12.00V
12.60V


+12V2
±5%
11.40V
12.00V
12.60V


5V
±5%
4.75V
5.00V
5.25V


3.3V
±5%
3.14V
3.30V
3.47V


-12V
±10%
-10.80V
-12.00V
-13.20V


+5VSB
±5%
4.75V
5.00V
5.25V

</tbody>
Here's an example of a voltage regulation test results chart you'll find in each of our PSU reviews:
http://media.bestofmicro.com/B/3/486399/original/Voltage-Regulation.png
</section> <section id="p4" class="line"> Efficiency The 80 PLUS (http://www.plugloadsolutions.com/80PlusPowerSupplies.aspx) certification measures efficiency at 20-, 50- and 100-percent load of the PSU's max-rated capacity up to the Gold efficiency certifications. For the Platinum and Titanium levels, they also measure efficiency with 10 percent of the PSU's max-rated capacity load.
Simply put, if a PSU has an 80 PLUS certification, then it must have the equivalent efficiency required by the corresponding certification. However, 80 PLUS measures at a mere 23 °C (73.4 °F) ambient, whereas we measure efficiency at a higher ambient temperature. This means that, in many cases, a PSU that is certified to a certain efficiency category fails to deliver the same efficiency at higher temperatures in our tests.
Also, many PSUs are tuned to deliver high efficiency at or above a specified load percentage, usually the minimum that 80 PLUS measures at the corresponding efficiency level. But at loads lighter than that, their efficiency is pretty low. Since many of us run our systems for long periods at low-energy consumption modes, efficiency at light loads can be highly important. So it's wise to pay special attention to our light-load test results.
http://media.bestofmicro.com/B/7/486403/original/Efficiency_Graph1.png
In our reviews, we measure efficiency at four different light loads: 20, 40, 60 and 100W.
The ATX specification also states that the efficiency of the 5VSB rail should be measured, too. In the table below, you will find the minimum 5VSB efficiency levels that the ATX specification recommends.
Recommended System DC And AC Power Consumption
<tbody>
Load
Efficiency


≤0.225W
< 0.5W to meet 2013 ErP Lot 6 requirement (100V~240V)


≤0.45W
< 1W to meet ErP Lot 6 requirement (100V~240V)


≤2.75W
< 5W to meet 2014 ErP Lot 3 requirement (100V~240V)

</tbody>
Testing in Standby Mode In 2010, the European Union released a guideline on Energy Related Products (ErP Lot 6 (http://ec.europa.eu/enterprise/policies/sustainable-business/ecodesign/index_en.htm)), which states that every electronic device should have below 1W power consumption in standby mode. In 2013, this limit was further reduced to 0.5W. The same year, the EU also released the ErP Lot 3 guideline for computers and computer servers.
This is why we measure the consumption of a PSU in standby mode, which is something that would be difficult without our monitoring software since the readings at such low consumption levels have significant fluctuations. We have to average them over a significant period of time to provide enough accuracy.
</section> Ripple Voltage Ripple represents the AC fluctuations (periodic) and noise (random) found in the DC rails of a PSU. Ripple significantly decreases the life span of capacitors since it increases their temperature; a 10 °C increase can cut into a capacitor's life span by 50 percent. Ripple also plays an important role in overall system stability, especially when it is overclocked.
The ripple limits, according to the ATX specification, are 120mV for the +12V and -12V rails, and 50mV for the remaining rails (5V, 3.3V and 5VSB). Nonetheless, in modern PSUs, we expect to find much lower ripple. It should be just a small fraction in high-end platforms with quality components and the proper amount of filtering capacitors. Below, you will find a schematic that analyzes a ripple waveform.
http://media.bestofmicro.com/O/6/481686/original/Figure33_ripple_noise_waveform_600x.jpg



Todo o manual:
http://www.tomshardware.com/reviews/how-we-test-psu,4042.html

LPC
05-11-15, 14:31
Boas!
Bom tópico de utilidade e geral para todas as fontes...

Vai ficar fixo para ser de fácil consulta e não se perder nos restantes tópicos...

Cumprimentos,

LPC