PC Buyer's Guide: choosing a power supply

    Hi Geektimes! Today we continue our PC Buyers Guide cycle and talk about the piece of hardware without which no computer will work at all. About the power supply. Questions about power supplies are asked a lot and regularly. Of course, the most common question is how to choose the right PSU and how powerful a “feeder” is needed for a certain set of iron. But in addition to calculating the required capacity, there are several more interesting topics that I would like to highlight today: what is 80+ certification, which marketing “enhancers” should be ignored, and which ones to consider, and, of course, which manufacturer to choose.





    Instead of the foreword


    - Grandfather, how does the plane fly?
    - How-how ... Here's how: “Oooo-oo-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o»

    In order to better understand some aspects of power supply and generally more or less understand why the choice of power supply is more important than at first glance seem to many users (especially those who have not lost the hardware because of the filthy feeder), it is worth considering the general principles of this thing.

    In the outlet with you (and also with most of humanity) we have alternating current, voltage - 220 volts, which change their "direction" 50 times per second. In countries of decaying capitalism across the ocean, a different standard is adopted (usually 110 V at 60 Hz, but various other distortions also occur). Modern PSUs have the ability to work in both those and other networks. Input characteristics are determined automatically or manually (by switch), depending on the model.



    The main voltages inside the computer are 3.3 V, 5 V and 12 V, moreover, we are not talking about any “change”, all the elements work on direct current. To correctly “straighten” the 220 V variables and “saw them” to the above-mentioned voltmeter readings in the computer, the power supply is used. So, what is the BP inside and why is such crazy money being asked for it?

    I have inside, um ... neonka!


    Attention: the description of the part of the interior design is deliberately omitted: those who know electrical engineering / are fond of microelectronics - knowing how the power supply is arranged, will do well without this section, and those who are new to this theoretical material in a more detailed form are hardly necessary now, the rest - Wikipedia to help.

    The interiors of the power supply unit can be conditionally divided into three large parts: input circuits, converter and output circuits.

    In the input circuits, the alternating current, passing through several filters and the power corrector (more about it later), is “rectified” by the diode bridge:



    Despite the constant change in polarity at the input, the relative orientation of the diodes allows you to get a fixed output with a "plus" and "minus". After such a conversion, the alternating current turns into direct, however, with one small unpleasant effect: instead of direct current and constant voltage, we get a constant current of alternating voltage:



    For normal further conversion of direct current, it is necessary to apply various filters: capacitors, inductors, voltage stabilizers, which smooth out ripples in voltage to acceptable values.

    Further, the current, rectified and tamed to constant values, enters the conversion unit, which consists of a push-pull converter on bipolar, which is now rare or MOSFET transistors. Next, a pulse transformer is used, which creates the necessary voltage for the computer (+3.3, +5 and +12 Volts). It is also used for galvanic isolation of the insides of the BP and PC with an external network. The main magic happens here. The circuitry inside the device is responsible for the stability and conversion efficiency, and the better it is, the more expensive the device is and the less energy is wasted: on heating, fan noise and electricity bills. In addition, the better the filling, the less likely that something will happen to the computer due to unstable power.

    The output circuits provide repeated filtering of the received power lines and carry out the “feedback” of the iron with the PC: an increase in power consumption causes a voltage drop, and it makes it clear to the PSU that it is necessary to increase the performance of the transformer and restore the required parameters of the PC's internal power network.

    Power calculation


    It so happened that almost 95% of the electricity generated by the power supply goes to simply ... warm the air! No, in fact, all this movement of electrons and holes is involved in switching transistors, settling in the form of “ones” and “zeros” on hard drives and SSDs, displaying information on the display and speakers, but along the way they create only one type of mechanical work: heating (we already talked about the removal of heat from the processor in the last issue of PCBG).

    Roughly speaking, we can assume that a computer consumes electricity according to the declared TDP (thermal packages) of its components, adding some constants for those devices whose TDP is unknown to us or not declared: hard drives and optical drives, cooling systems and any peripherals. Video card manufacturers, as a rule, do not indicate the TDP of their offspring, but the power consumption can be approximately determined by the power connectors used. The standard PCIe x8 / x16 bus delivers up to 75 watts of power for a video adapter. Additional 6-pin connectors add 75 watts each. More powerful video cards can have 8-pin connectors on board that can transmit up to 150 watts. Thus, if your video card (current, or planned) has one 6-PIN and 8-PIN connector,

    So that you do not get confused in all this diversity, we have prepared a convenient plate on which you can estimate the required power of the PSU.
    PC components
    Power consumption under load
    CPU
    35 to 150-160 W, see processor TDP
    Video card
    75 W on PCIe, 75 W on 6-PIN, 150 W on 8-PIN, summarize all connectors
    Motherboard
    35-65 watts
    DDR memory per module
    4-6 watts
    HDD, optical drive (in recording mode)
    10 W for conventional models, 15 W for high-speed HDD or Blu Ray
    SSD
    5 W for regular models, 10-15 W for PCIe exotic with integrated RAID
    PCI-X devices
    2-5 watts
    Fans
    ~ 3 W
    Suppose you are assembling a new domestic horse for yourself a couple of years ahead, it remains only to choose a PSU. Here is an example of power consumption calculations:
    MBo: MSI H97 PC Mate
    CPU: Core i5-4460 , TDP 84 W
    GPU: MSI nVidia GTX970 (6 + 6 PIN)
    RAM: 2x8 GB DDR III Kingston HyperX (1866 MHz)
    SSD: 120 GB Kingston HyperX 3K
    HDD: 2 TB Wd se

    The motherboard does not belong to the High-End, we will not overclock anything, so we take the average value on the plate: about 50 watts. The processor is declared 84 W, rounded up to 85. On the video card there are two six-pin power connectors + there are 75 W on the PCIe connector, total 3x75 W, two RAM modules of 5 W each, 1 HDD and 1 SSD, totaling another 10 + 5 W. Let 5 fans stand in total (together with a processor cooler) in the case: another 3x5 watts. Add, we get 50 + 85 + 75x3 + 5x2 + 10 + 5 + 5x3 = 400 watts!

    But wait rejoice. The fact is that the efficiency of the power supply is not equal to 100%, moreover, it depends directly on the load. At the minimum (that is, in the case when your computer is idle), the efficiency drops, at the maximum or close to it - similarly. The most effective range is 50-60% of the load on the power supply, in which case the PSU performance is at an optimal level. Accordingly, if your use-case is games on weekends, a typewriter on weekdays, then you can limit yourself to a reasonable 15-20% of the estimated power (just in case + for a potential upgrade of RAM and hard drives), since most of the time is hardware will not load the PSU to the limit and the whole system will be in conditions comfortable for it. If a computer at home is also a working tool, it’s worth, firstly, to make the power reserve a little higher,

    Certification 80+


    When choosing a power supply, you may notice that on many models it is either indicated in the product description, or there is a sticker on the PSU itself with an indication of incomprehensible eighty pluses. In fact, this sticker is a certification icon for BP performance. The higher the sticker class, the higher the PSU efficiency and the less “extra” power it eats out of your wallet every month in electricity bills. In addition, the 80 PLUS sticker has another nice bonus. To achieve such efficiency, using so-so components inside will not work. That is, it is also a banal "quality certificate" of your PSU.


    When buying a new computer, even in the conditions of austerity, it’s not worth taking power supplies from an unknown manufacturer without such a sticker, even the basic white one. There is a chance to run into a cheap Chinese craft, but what the cunning optimizers saved on the inside is not known.

    Of course, we in Yulmart try to avoid unreliable models and dubious suppliers, but once a year, as they say, a stick shoots

    As for saving, here we are forced to disappoint you. In order to beat off buying a PSU with a 80+ Platinum or Titanium class, you must at least have a bitcoin farm on video cards, otherwise the exhaust will be minimal. If you are not very limited by funds, you should pay attention to models with certification above 80+ Bronze, but do not engage in meaningless "improvement"; it’s better to spend an extra couple of thousand in the power supply for the sake of the cherished 80+ Platinum, faster, more capacious SSD or a more powerful graphics card - depending on your needs.

    Nice bonuses


    One of the most pleasant “chips” of modern PSUs is the modular design: some wires (and sometimes all wires) have connectors at two ends, allowing you to remove excess and unused “braids” from the system unit: it’s both aesthetically pleasing and easier to lay cables inside a PC , and less resistance to air flow in the housing. Of course, you have to pay extra for this chip, albeit a little.

    If you are building a computer and your budget is very limited, you can not bother with the “modulators” and just take an inexpensive, high-quality model with “built-in” wires, and there are always some places to invest the extra 500-600 rubles.

    Marketing husk


    Many companies introduce various “unique” technologies with beautiful names into their PSU, trying to justify the high price of their products. Often, all these chips are ordinary public achievements of electrical engineering in a beautiful wrapper, however, there are a number of letters and phrases that are worth paying attention to.

    The necessary things include:

    OVP / UVP - protection against overvoltage and undervoltage,
    OCP / OLP / OPP - protection against overcurrent and PS overload,
    OTP / OHP - protection against overheating,
    NLO - protection against no-load operation,
    SCP - protection against short circuit.

    Not to say that all these features are needed every second every time, but it’s better to have a power supply and a computer just turned off than smoke and stench from exploding capacitors or dead iron for many thousands of rubles.

    Recommended Models


    Of the simple, reliable and unremarkable PSUs, the FSP ATX-550PNR can be noted . It is inexpensive (less than three thousand rubles), perfectly assembled, no noise, has a two-year warranty and is extremely rare in service centers. The power supply is 550W, which is quite enough for a very typical system unit (such as the one that we “collected” a couple of paragraphs above).

    A slightly more expensive model (but already with an efficiency class of 80+) is the Chieftec GPS-550A8 , and it looks nicer and does not make noise.

    If after all the calculations you have come to the conclusion that you need a power supply with a power of 600-650 W, you should pay attention to the CoolerMaster G650M model. It has 80+ Bronze certification, a good cooling system, supports automatic fan speed control, a modular cable connection system and costs a little more than five thousand rubles. The model is fresh, but in the "iron" press and among enthusiasts, it is extremely successful. By the way, it also exists in the 750-W version.



    Alternative for Cooler Master'a in the segment of high-power power supply for high-end computers can be called a Corsair CX 750 M . In stock - all the same pluses as the CM G650M - modular design, 80+ Bronze certificate and excellent reputation. In addition, the price does not bite much - we have a Corsair worth a little less than seven thousand rubles.



    Well, about all sorts of monsters, such as the Corsair CP-9020008-EUat 1.2 kW you can safely forget. If you do not have 4 video cards for 30-40 thousand rubles each, then you definitely will not need such a monster for ~ 20 thousand rubles.

    Passive cooling


    For fans of deathly silence, there are special fanless models that do not make any sounds at all (unless, of course, the manufacturer set normal chokes). All of them are usually indecently expensive due to 80+ Platinum / Titanium certification (and passive cooling is difficult to obtain without such efficiency).


    Thanks for the picture to Overclockers.ru.

    An example is the 500-Watt Chieftec PGS-500C . The price is an impressive 10 and a half thousand rubles. For about the same money, for example, you can take the 850-Watt TT Moscow with a "gold" certification and a completely silent cooler or the 1000-Watt TT Volga with similar characteristics in terms of efficiency and noise.



    You can only hear it in a deaf crypt, but ordinary people cannot understand these passivators :)

    FAQ


    There are a number of frequently encountered issues that I would like to highlight before we summarize.

    >> I already have a PSU, I thought it should be enough. Do I need to replace it with a new one or can I leave it as is?
    The question is how old your PSU is. If you have not changed the computer since the fourth Pentium, and now decided to install a new Core i3 and a simple video card such as nVidia 840, you may find that your PSU simply does not support 24-pin power for modern motherboards. In addition, the old PSUs had an emphasis on the 3.3 and 5 volt line, and the twelve-volt power lines were mainly focused on connecting hard drives and optical drives. Now the emphasis is shifted just to the voracious 12-volt power supply circuitry for video cards. So if you have a frankly old PSU - it is worth replacing it with a current one, albeit not very expensive.

    >> Why do some PSUs make a vile whistle under load?
    A vile whistle or creak is the sound of filtering elements (chokes ). The fact is that the inductor is a commonplace inductor, and the high-frequency current passing through it can cause it to vibrate finely, hence the whistling-hissing-creaking sound. Power reactors can whistle both on the PSU and on the motherboard / video card. If you find such a flaw in a new product - bring and change. Unfortunately, the whistle of throttles is rarely recognized as a warranty case, so in the "old" power supplies either put up, or ... If your hands grow out of your shoulders, you can fill the chokes with epoxy resin, however, this will lead to loss of warranty.

    >> Why put a power supply of 1 kW or more?
    Such PSUs are used in gaming computers with two or more video cards. The relevance of such an assembly for everyday use is a big question, since SLI / Crossfire-X only adequately manifests itself in multi-monitor assemblies with a huge overall resolution, for a single monitor, even with a resolution of 2560x1440 and 3840x2160, one video card like R9-290X or nVidia 780Ti is enough (it is more productive than the 980th, and the 980Ti have not yet come out).

    >> How much power supply does it consume from the network?
    Efficiency of a power supply with good filling floats in the region of 80-90%. Thus, a 600-W PSU consumes about 660-720 W from the network under almost full load. In addition, depending on the design of the power supply unit and the installed power correction unit, from 2 to 30% “from above” can be spent in void and heat. So the old 600-Wattnik of an unknown manufacturer may well consume up to 1 kW at full load in adverse conditions. Working intensively for 4 hours a day, such a computer will “burn” you electricity by about 1x4x430 = 120 kW * h. That is, about 540 rubles according to a single-rate meter in Moscow per month. Replacing a PSU with, say, a new one, with a power of 700 watts will allow you to “beat off” the difference in a couple of years. On the one hand - saving so-so, on the other - who knows how much electricity will cost in 2-3 years?

    Total


    That's all. In our store, there are always a lot of models of power supplies to choose from for a variety of needs - a good hardware selection for you, a high-quality power supply and no way to service centers :)

    Previous publications from the PC Buyer's Guide cycle:
    » PC Buyer's Guide: cooling
    » PC Buyer's Guide 2015: Motherboards, Chipsets, and Sockets
    »I twist and twist, I want to confuse. We understand the lines of HDD

    On what topic do you want to read PCBG in the next issues?

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