Power supply for a computer with speed control. Automatic fan control. List of symbols, symbols, units, abbreviations and terms

1. Computer power supply
2. Power
3. Active or passive PFC?
4. Power supply cooling
5. Connectors and cables
6. Brands and manufacturers
7. From the history
8. Development prospects

Computer power supply

Choosing the right power supply for your computer is sometimes not as easy as it seems. The stability, as well as the service life of all used PC components, depend on this choice, and you need to take the issue of choosing a power supply seriously. In this review, we will try to consider the main points that will help you make the right choice.

Power

The output of the power supply contains the following constant stresses: +5 V, +12 V (also +3.3 V), and - auxiliary (minus 12 V and + 5 V in idle). The main load is now “accepted” to load the +12 V line.

Output power (W - Watts) is calculated by a simple formula: it is equal to the product of U and J, where U is voltage (in Volts), J is current (in Amperes). Voltages are constant, therefore, the greater the power, the greater the current strength along the lines should be.

But it turns out that not everything is simple here either. With a heavy load on the combined line +3.3 / +5, the power on the +12 line may decrease. An example is the marking of the power supply unit of the budget brand Cooler Master (models RS-500-PSAP-J3):

The maximum total power on the +3.3 and +5 lines is 130W (which is indicated on the package), but the maximum power on the “most important” + 12V line is 360W.

But this is not all. Let's take a look at the caption below:

3.3V and + 5V and + 12V, the total power should not exceed 427.9 W. As if, theoretically (looking at the "table"), we "see" 490W (360 plus 130), but here - only 427.9.

What will this give us in practice: if the load on the line + 3.3V and 5V is in total, say 60W, then subtracting 427.9 from the power supplied by the manufacturer, i.e. 427.9 - 60, we get 367.9W. We will only get 360 watts from the +12V line. From which comes just the "basic consumption": the current to the processor, video card.

Automatic power calculation

To calculate the power of power supplies, you can use the calculator in the browser: http://www.extreme.outervision.com/psucalculatorlite.jsp. Although he is on English language, you can figure it out. There are many such services on the Internet.

In general, here you can choose almost everything you need, including a specific type of CPU, motherboard format (micro-ATX or ATX), the number of memory sticks, hard drives, fans ... To calculate, you need to press the rectangular "Calculate" button. The service will give out: both the recommended and the minimum possible power value (in Watts) for your system.

However, from experience, we can assume: an office computer (with a dual-core CPU) can be content with a 300W power supply. For a home (gaming, with a discrete video card) - PSU 450 - 500W is suitable, but for powerful gaming PCs with a "top" (top) card (or two, in Crossfire or SLI mode) - Total Power (total power) starts from 600 - 700W.

The central processor, even at the maximum possible load, consumes 100 - 180W (with the exception of 6-core AMD), a discrete video card - from 90 to 340W, the motherboard itself - 25-30W (memory bar - 5-7W), HDD 15-20W. Keep in mind that the main load (processor and video card) falls on the "12V" line. Well, it is desirable to add a margin of power (10-20%).

Efficiency - efficiency factor

An important criterion will be the efficiency of the power supply. Coefficient of performance (COP) - the ratio of the useful power produced by the power supply to the power consumed by it from the network. If the PC power supply circuit contained only a transformer, its efficiency would be about 100%.

Consider an example when a power supply (with a known efficiency of 80%) provides 400W output power. If this number (400) is divided by 80%, we get 500W. A power supply with the same characteristics, but with a lower efficiency (70%), will already consume 570W.

But - do not take these numbers "seriously". The power supply most of the time is not fully loaded, for example, this value can be 200W (the computer will consume less from the network).

There is an organization whose functions include testing power supplies for compliance with the level of the declared efficiency standard. 80 Plus certification, however, is only for 115 Volt networks (common in the USA), starting from the "class" 80 Plus Bronze, all units are tested for use in a 220V mains. For example, if certified in the 80 Plus Bronze class, the power supply efficiency is 85% at "half" power load, and 81% at the declared power.

The presence of a logo on the power supply indicates that the product meets the level of certification.

pros high efficiency: Less energy is dissipated "as heat" and the cooling system is therefore less noisy. Secondly, the energy savings are obvious (although not very big). The quality of "certified" PSUs is usually high.

Active or passive PFC?

Power Factor Correction (PFC) - power factor correction. Power Factor - the ratio of active power to total (active plus reactive).

The load, however, does not consume reactive power - it is 100% returned to the network, in the next half-cycle. However, with an increase in reactive power, the maximum (per period) value of the current increases.

Too much great power current in wires 220V - is it good? Probably not. Therefore, with reactive power fight whenever possible (this is especially true for really powerful devices, "passing" the limit of 300-400 watts).

PFC - can be passive or active.

Advantages of the active method:

Close to ideal value Power Factor (power factor), up to a value close to 1. With PF=1, the current in the 220V wire will not exceed the “power divided by 220” value (in the case of lower PF values, the current is always slightly higher).

Disadvantages of active PFC:

As complexity increases, the overall reliability of the power supply decreases. The active PFC system itself needs cooling. In addition, it is not recommended to use active correction systems with autovoltage in conjunction with UPS sources.

Advantages of passive PFC:

There are no disadvantages of the active method.

Flaws:

The system is inefficient at high power values.

What exactly to choose? In any case, when purchasing a PSU of lower power (up to 400-450W), you will most often find in it the PFC of a passive system, and more powerful blocks, from 600 W - more common with active correction.

Power supply cooling

The presence of a cooling fan in any power supply is considered the norm. Fan diameter - can be equal to 120 mm, there is an option for 135 mm and, finally, 140 mm.

The system unit provides for the installation of a PSU at the top of the case - then, choose any model with a horizontally located fan. Larger diameter - less noise (with the same cooling capacity).

The rotation speed should change depending on the internal temperature. When the PSU does not overheat - why do you need to turn the “valve” at all speeds and annoy the user with noise? There are PSU models that completely stop their fan when the power consumption is less than 1/3 of the calculated one. Which is convenient.

The main thing in the PSU cooling system is its silence (or the complete absence of a fan, this also occurs). On the other hand, cooling is necessary in order to prevent overheating of parts (high power, in any case, entails heat generation). At high power, without a fan - you can not do.

Note: the photo shows the result of modding (removal of the standard slotted grille, installation of a Noktua fan and a 120 mm grill).

Connectors and cables

When buying and choosing, pay attention to the number of available connectors and the length of the wires coming from the power supply. Depending on the geometry of the case, you need to choose a power supply unit with a cable bundle of sufficient length. For standard ATX cases, a 40-45 cm harness will suffice.

The power supply that works in a home and office computer has connectors:

This is a 24 pin PC motherboard power connector. Usually here - separately 20 and 4 contacts, but it happens - and monolithic, 24-pin.

Processor power connector. Usually it is 4-pin, and only for very powerful processors use 8 pins. You can choose the right power supply for your computer, focusing on the appropriate connector of the motherboard itself.

The video card power connector looks similar, and differs in that it is 6-pin or 8-pin.

Connectors (connectors) for powering SATA devices (hard drives, optical drives), four-pin Molex (for IDE), and for enabling FDD (or a card reader) are familiar to most users:

Note: the number of all additional connectors (SATA, MOLEX, FDD) must be sufficient to connect devices placed inside the system unit.

Montage demontage

To dismantle the old power supply, disconnect its 220 Volt wire. Then, you need to wait 2-3 minutes, and only then get to work. Attention! Failure to comply with this requirement may result in electrical injury.

The power supply in any PC is attached to the back wall with 4 screws (self-tapping screws). You can unscrew them only by disconnecting all the internal connectors and plugs of the power supply (2 connectors of the motherboard, video cards, connectors for additional devices).

You can connect the power supply to the computer in the reverse order: first, we mount it in the case, fixing it with screws, then we connect the connectors.

Note: when manipulating the power supply, the processor cooler may interfere. If it is possible to dismantle it - use this (put it in place - later, before turning it on).

Turning on a computer with a new PSU

Having applied 220 Volt power to the new PSU, you do not need to immediately turn on the computer. Wait 10-15 seconds first: you will listen to see if anything "out of the ordinary" is going on. If we hear a squeak, the ringing of chokes - we go and change the power supply under warranty. If you hear a periodically repeated “metallic” click, do not turn on the computer with such a power supply.

If in standby mode, the power supply "clicks" - this is the protection system. Turn off such a power supply, disconnect its connectors (connectors). You can try to assemble the same thing again - if the problem repeats, we carry the power supply to the service center (perhaps the unit itself is faulty).

A computer with a working PSU turns on almost immediately when you press the "Power" button of the ATX case. An image should appear on the monitor - now you can continue to work, but already - with a new power supply.

Modular cables and connectors

Many more powerful power supply models now use the so-called "modular" connection. Adding internal cables with appropriate mating connectors - occurs as needed. This is convenient, because there is no longer any need to keep extra (unused) wires in the computer case, and besides, there is less confusion. And the absence of unnecessary wires also improves the circulation of hot air. In modular power supplies, only cords with a motherboard / processor connector are made “non-removable”.

Brands and manufacturers

All companies (manufacturers of power supplies for a computer) belong to one of 3 main groups:

1. They produce their own products - such brands as Hipro, FSP, Enermax, Delta, also HEC, Seasonic.
2. They produce products by shifting part of the manufacturing process to other companies - Corsair, Silverstone, Antec, Power & Cooling and Zalman.
3. They resell ready-made blocks under their own brand (some make a "selection", some do not): Chiftec, Gigabyte, Cooler Master, OCZ, Thermaltake.

Each brand listed above can be safely recommended. On the Internet, in addition, there are many reviews and tests for “branded” power supplies that the user can navigate.

Before buying a PSU, it is worth weighing it (just hold it in your hand). This will allow you to more or less understand what is inside him. Of course, this method is inaccurate, but it allows you to immediately "sweep" a clearly "cheap" PSU.

The mass of the power supply depends on the quality of the steel, the dimensions of the fan, and (most importantly): the number of chokes and the weight of the radiators inside. If the PSU lacks some inductors (or, say, capacitors of reduced capacity), this indicates a “cheapening” electrical circuit A: PSU will weigh 700-900 gr. A good PSU (450-500W) usually weighs from 900 grams. up to 1.4 kg.

From the history

In the market of personal computers, that is, not only IBM-compatible, but - in a more general sense, "computers", IBM initially went to standardize components (PSU, motherboard). The rest then began to "copy" it. All known form factors for IBM-compatible PC power supplies are based on one of the PSU models: PC/XT, PC/AT, and Model 30 PS/2. All compatible PCs, one way or another, could use one of the three original standards developed by IBM. These standards were popular until 1996, and even later - the modern ATX standard dates back to the physical layout of the PS / 2 Model 30.

A new form factor, that is, ATX known to us, was determined in 1995 by Intel (then an IBM partner), introducing a standard for the board and power supply. The new standard has gained popularity since 1996, and manufacturers have gradually begun to move away from the outdated AT standard. ATX and some of the "branches" of the standard that followed it use mat connectors that are different from the AT form factor. boards (not only with additional voltages, but also with signals that allow you to provide more power and additional features).

All IBM-ovsky standards provided physically the same connector that supplies power to the motherboard. To turn it on and off, to supply power to the computer, a toggle switch (or button) was used, breaking the wire with a voltage of 220 volts. Which was not very convenient (especially when parsing / repairing a PC). Therefore, a new standard has appeared that “does not allow” a voltage of more than 12 volts inside the system unit (inside the case).

It must be said that the power circuit itself (the principle of its construction), starting from the first PC XT, significant changes did not receive. The principle of energy conversion used in computer power supplies is called "pulse" (from AC voltage 220 volts is made “constant”, then it is converted, lowered to lower values ​​​​by the pulse method). The first power supplies for personal computers had a power of 60 W (XT), or, say, 100-120 W (AT 286). Simply, then the computer provided for the installation of: 1-2 disk drives, one hard drive (and the processor itself - "consumed" very little).

Development prospects

800 watts, 900 watts, 1000 watts ... A power supply for a PC that delivers one kilowatt of energy to the load is no surprise. Of course, the price is significantly different (from the "standard" 450-500 W boxes), however, such a power supply provides a sufficient level of reliability (and - a low noise level) even at full load! Well, just a miracle.

If we calculate how much energy such a computer will consume from the outlet, it turns out that this is nothing more than the equivalent of an iron constantly turned on at full power. A good one, in terms of power - above average, heavy ...

Recently, with the transition to new manufacturing processes for the production of "main" microcircuits for a computer (central processor, 3-D module), the movement has been just "reverse" - that is, a decrease in total power while maintaining the same level of performance. Two years ago, the average 4-core “percent” consumed at least 90 W, now it is already 65 W (“new”, and faster). In any case (both 2 years ago and now), the choice is up to the user.

Many potential buyers in the computer components market are alarmed by the fact that it is impossible to find a fan for the power supply in store windows. Here for the processor, video card, case, hard drive- Please, there is nothing for BP. It really looks very strange and causes a lot of negative emotions according to user reviews. However, there is no need to be upset. Any expert will tell you that a regular cooler is installed in the power supply to cool the case. The difference can only be in the size - 120, 80, 60 or 40 millimeters. By the way, any user can verify this by disassembling his PSU.

The focus of this article is a fan for a computer power supply. The reader is invited to get acquainted not only with worthy models, their descriptions and photos, but also with the maintenance of a non-working cooling system. After all, in 90% of cases, replacing the fan is not needed at all, just a little cleaning is enough.

Fascinating math

It is better to start not with the choice of a specific model or brand, but with the technical requirements that apply to the fan. Yes, such a simple computer component has a number of limitations that the user will have to put up with, because from right choice the comfortable work of the user at the computer depends. It follows that the basic requirements are noiselessness and efficiency of blowing.

The cooling fan in most cases does not know how to independently regulate the speed of the impeller. Applying 5 volts to the cooler, the PSU uses the maximum rotational speed that is characteristic of this voltage. This is where interesting events begin, because the characteristics for all fans are indicated for a 12-volt line. There are few options here - trust your instincts or the recommendations of experts, because it is impossible to mathematically accurately calculate the behavior of the impeller.

How to be?

This is where the trust factor comes into play. famous brand, who took care of the buyer and independently measured the impeller speed and air flow on the 5-volt line. True, there are not so many such brands on the market, plus the prices for their products are quite high. But this option can be safely considered, because it will satisfy the wishes of users in terms of silent operation and efficient cooling.

It is better to look for a fan for a computer power supply among products from well-known global manufacturers, such as Thermaltake, Zalman, be quiet, Noctua, Scythe. The cooler package contains data on the operation of the fan at 5 and 12 volts. Accordingly, data on speed and noise level are indicated. For example, Noctua NF-P12 - 600 rpm (12 dB). Or Thermaltake Riing 12 - 1000 rpm (18 dB). By the way, in the last example, the fan is backlit.

Basic fan requirements

Having dealt with the methodology for choosing a worthy product in the computer components market, it's time to go directly to the requirements. should not exceed 20 decibels. This is very important factor, because this indicator is a certain threshold of audibility. As for the speed of the impeller, it all depends on the quality of the assembly. There are models that spin at a frequency of 2000 rpm. However, experts recommend limiting yourself to 1200 rpm.

Many users have already heard many times that all the fans in the system enter into resonance, due to which a terrible hum appears in and the case begins to rattle. Oddly enough, the computer's power supply may also be involved. The fan in it twitches not only due to a malfunction. The problem may also be in too high an impeller speed. Also, cheap Chinese fans have a problem with the skew of the rotor, which is why a constant knock is heard in the operation of the device, and the cooler itself starts to twitch.

From theory to practice

Having figured out which fan is in the computer's power supply, the user can only buy its analogue and replace it. However, here the owner expects a small surprise. This is an interface for connecting to the power supply. Almost all fans are sold with a 4-pin connector, and there are only two pins on the PSU board, plus they are soldered. You shouldn't get upset, in most cases there is a soldering dummy on the board. In fact, two wires from the fan are just in glue.

Naturally, having unscrewed the cooler from the PSU case, you need to carefully remove the glue from the contacts (you may need a knife). At the end of the cleaning procedure, a board with two pins will be in front of the user. The main thing here is to remember where is the plus (red wire), and where is the minus (black wire). Then it's a matter of technique: you need to put a 4-pin connector on these two contacts so that the polarity matches the color of the cables. And there is nothing wrong with the fact that two contacts remained unconnected.

Foreboding

Noisy fan in computer power supply? This event causes a lot of indignation on the part of users who start counting the cost of purchasing a new cooler. It is at this stage that there is no need to rush, the fact is that noise is not a breakdown. This is a signal to the owner of the computer that there are some difficulties in the operation of the fan that need to be fixed immediately. It's pretty simple here:

• the power supply is removed and disassembled and purged from dust;
• the fan is unscrewed and removed;
• the protective sticker on the cooler rotor is removed, 3-4 drops of oil are poured inside;
• the sticker is returned to its place, the PSU is assembled and installed in the computer.

The algorithm is quite simple, but very effective. There may be problems with a sticker that has lost its sticky properties. It is not necessary to put it in this form, it will fall off anyway and will rumble inside the case. It is better to install a new sticker. Where to get? Cut out from thick tape, use the insert from chewing gum or purchase any children's sticker of similar sizes in the store.

Lubricant

Having decided that the replacement of the computer power supply fan is not needed, it will not be difficult for the user to take measures to clean and lubricate the cooler. However, there is one factor that all readers should pay attention to. It's about lubrication. The fact is that the rumble in operation is emitted not by the fan blades, but by the bearing, which, from drying out, begins to distort the movement of the rotor.

The user must only use fluid oils capable of lubricating the bearing. However, do not forget about the high viscosity, because the lubricant should remain inside, and not flow out under the influence. Here it is better to use a lubricant for sewing machines (an analogue of the I-8 brand). In extreme cases, engine oil will also do.

Time to say good-bye

The only symptom that requires the user's attention to itself when it comes to such an element as a computer power supply is that the fan is not spinning. In such cases, lubricating the bearing can only prolong the life of the cooler by a few days (if you manage to spin the impeller after applying the oil). But leaving the power supply in this state is not recommended. It is the impossibility of cooling the boards with a faulty fan that can disable the power supply, which, in turn, can burn the motherboard and other components of the system unit.

Work on mistakes

Not every user undertakes to change the fan for the computer power supply. Often this work is trusted by many owners service centers who specialize in such breakdowns. In fact, this is the right decision, however, judging by the reviews of the owners, there are exceptions. We are talking about installing used fans in the PSU case that have worked out their resource in system block. For many users, the fan in the computer's power supply does not work after repair because of this.

The second problem that users may encounter is the lack of contacts in the PSU to connect the cooler. This is found only in cheap Chinese devices, where an economical manufacturer soldered all the components of the power supply. In such cases, the user must also clean the contacts and solder the fan to the board (there should be no twists).

Finally

As practice shows, in 99% of cases it is not necessary to change the fan for the computer power supply. It is enough just to disassemble the PSU, clean it of dust and lubricate the cooler. All this suggests that the electrical component of the computer just needs constant cleaning (once a year). Yes, there are situations when it is necessary to install a new cooler, but here the user will not have any problems. After all, the market has a fairly large assortment of worthy fans that can be safely installed as a cooling system for the power supply.

Recently, I finally coped with the noise coming from the processor cooler. With the help of cooling made from water. But it had almost no effect. Noisy power supply fan. So that the work was not in vain, I had to figure out how to get rid of the noise from the power supply. And in order to competently cope with any problem, you must always try to figure out the cause of its occurrence. So, as you know, this fan drives air that blows over the radiators inside the PSU case. Radiators, in turn, take heat from transistors and diode assemblies and give it to the air. In general, two methods are mainly used to increase the efficiency of heat transfer from a solid to a gas or liquid (or vice versa). This is an increase in the heat exchange surface of a solid body and an increase in the so-called heat transfer coefficient. This coefficient depends on many factors, for example, on the shape of the surface, on the direction of gas movement relative to the surface, on the gas flow rate, on the type of gas, etc. In a conventional power supply, a fan (or fans) is just needed in order to compensate for a small heat exchange area of ​​radiators by increasing the heat transfer coefficient. But we need to either get rid of the air flow completely, or reduce it to an acceptable value. In this case, the heat transfer coefficient will decrease. In order for the heat transfer from the elements to the air to remain at least at the same level, it is necessary either to compensate for the reduced heat transfer coefficient by increasing the heat transfer area of ​​the radiator or to increase the heat transfer coefficient by changing the factors on which it depends (for example, the most stable change in the type of gas).

In short, it begs two relatively simple ways eliminate noise: put a larger radiator, or make a water block. Of course, making water cooling only for the power supply is stupid (but original). And it is reasonable if you already have a CBO at least for the processor. I refused this method, even though I have a water system. cool. due to the fact that it can be dangerous and reduce the reliability of the entire system. Yes, and finding and installing a radiator is easier than a water block.

Before unwinding, soldering, soldering and screwing it all up, I took off the cover of the power supply and figured out what I would need for all this modernization and whether I could even do it. In general, interest and a desire to brag to my friends did not allow me to figure it out for a long time, and I went to the radio parts store for a radiator and polymer gaskets. This is all that is needed for the alteration (although the gaskets can be put on the old ones). The store offered a used aluminum radiator.

As it turned out later, one of its sides turned out to be equal to one of the sides of the BP. What pleased. Sanded the visible surfaces of the radiator. Yes, for shine.

The power supply has two heatsinks.

To fix the transistors and diode assemblies to the new heatsink, they had to be soldered first. I had to solder the old radiators along with transistors and assemblies. It's easier. Soldered with a braid. Immediately soldered wires to the places of transistors and assemblies.

In the picture, the parts are already unscrewed. By the way, on the native radiator with transistors there was a voltage of one hundred and something volts, for which I don’t know (all parts were isolated, the radiator was not used as a conductor). I screwed the soldered parts with the same self-tapping screws to a new radiator using thermal paste. I isolated the parts from the radiator with polymer gaskets (after all, I replaced them with new ones, because the old ones were already deformed) and ceramic rings.

At first glance, the pads seem to be too big, but this is for safety. Suddenly, some transistor will turn around the screw. Then, if I want to warm my hands on the radiator, I will not only warm them, but also feel how good life is.

In order to start the computer more calmly later, you need to check with a tester whether the parts are in contact with the radiator. After checking, the radiator with parts was fixed to the PSU case in the old holes, instead of the unscrewed cover. Assemblies and transistors connected to their places by occasions. He put a vinyl chloride tube on his legs.

The fan did not turn off. Just in case of a fire. But I put an adjustable resistance of 150 ohms in the context of the minus. If nothing but semiconductors gets warm, I will set the speed to the smallest, so that it can start or remove it completely. The side walls were closed with galvanized sheet. Well, here's what my power supply looks like now.

Such a power supply is unlikely to get into a regular case. Although everything is as usual here - if you try and be smart, then everything is possible. This does not bother me, because I do not have a completely ordinary case, and there is enough space in it not only to install such a power supply.

In short, I installed it, connected it and turned it on. Everything worked, thank God, as usual. The fan started running at 150 ohms. Now, for confident operation of the unit, it needs to be checked in conditions close to combat. After a long run of 3DMark, the temperature of the heatsink to the touch is in the range of 50-550C. Unfortunately, I do not have such a useful thing as a thermometer. After the test, I turned off the computer as quickly as possible and removed the PSU covers to check the temperature of other elements. The temperature of the transformer is about 30 o C, touching the toroidal choke, I burned myself, but not immediately, probably about 70 o C ± 10 o C. The temperature is far from fatal for him. In addition to these elements, nothing has heated up significantly (no more than 30 o C). The fan at 150 ohms produced almost no flow. You can safely turn it off. Well, now (I thought about the block) let him just chirp.

Not so long ago, I came across an Enhance P520N power supply from a home computer. In addition to the main power supply board, another small device was found in it. It was a fan speed thermostat. The circuit is simple, contains only two transistors, four resistors, a diode and a capacitor. The device diagram is shown in Figure 1.

This regulator can be used not only for power supplies, but also in low-frequency power amplifiers, welding machines, powerful converters, power regulators, etc. Why buzz in vain if all PPs (semiconductor devices) are cold. Diode VD1, which is on the board and in the indicated circuit, is most likely needed only in a specific SMPS, so it can be removed. The board has a 1N4002 diode. The first transistor can be replaced with a domestic one - KT3102. According to the documentation, the imported C1384 transistor is designed for a collector current of 1A, a collector-emitter voltage of 60V, and a constant collector power dissipation of 1 watt. You can try to replace it with our KT814 with any letter or with KT972. The electrolytic capacitor should be 16 volts.

The initial fan speed is selected by changing the resistance value of the resistor R1. The scheme works as follows. When the temperature inside the controlled volume or directly in the heat sink of the PCB is low, then the transistor VT2 is closed and the fan has no great speed rotation. As the temperature increases, the resistance of the thermistor Rt begins to decrease, which in turn will lead to a decrease in the voltage at the base of VT1, and the collector current of this transistor will also begin to decrease. Reducing the current through the first transistor will increase the base-emitter current of the second transistor VT2 (the shunting effect of the transistor VT1 on the base-emitter junction VT2 will decrease). Transistor VT2 will start to open, the voltage on the fan will start to increase, its rotation speed will increase.
For greater versatility, a voltage stabilizer can be introduced into the circuit, for example, KR142EN8B. This microcircuit has a maximum input voltage over the entire temperature range of 35 volts.
The view of the board is shown in photo 1, and the figure printed circuit board in figure 2.

The speed of a modern computer is achieved at a fairly high price - the power supply, processor, video card often need intensive cooling. Specialized cooling systems are expensive, so a home computer usually has several case fans and coolers (radiators with fans attached to them).

The result is an efficient and inexpensive, but often noisy cooling system. To reduce the noise level (while maintaining efficiency), a fan speed control system is needed. Various kinds of exotic cooling systems will not be considered. It is necessary to consider the most common air cooling systems.

In order to reduce the noise during operation of the fans without reducing the cooling efficiency, it is advisable to adhere to the following principles:

1. Fans large diameter work more efficiently than smaller ones.
2. The maximum cooling efficiency is observed in coolers with heat pipes.
3. Four-pin fans are preferred over three-pin ones.

There can be only two main reasons for excessive fan noise:

1. Poor bearing lubrication. Eliminated by cleaning and new grease.
2. The motor is spinning too fast. If it is possible to reduce this speed while maintaining acceptable level cooling intensity, then this should be done. The most accessible and cheap ways to control the speed of rotation are discussed below.

Fan Speed ​​Control Methods

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The first way: switching in the BIOS the function that regulates the operation of the fans

Q-Fan control, Smart fan control, etc. functions supported by part motherboards, increase the fan speed when the load increases and decrease it when it falls. It is necessary to pay attention to the method of such fan speed control using the Q-Fan control as an example. It is necessary to perform a sequence of actions:

1. Enter BIOS. Most often, this is done by pressing the "Delete" key before booting the computer. If you are prompted to press another key at the bottom of the screen instead of "Press Del to enter Setup" before booting, do so.
2. Open the "Power" section.
3. Go to the line "Hardware Monitor".
4. Change to "Enabled" the value of the CPU Q-Fan control and Chassis Q-Fan Control functions on the right side of the screen.
5. In the CPU and Chassis Fan Profile lines that appear, select one of three performance levels: enhanced (Perfomans), quiet (Silent) and optimal (Optimal).
6. By pressing the F10 key, save the selected setting.

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The second way: fan speed control by switching method

Figure 1. Distribution of voltages on the contacts.

For most fans, the nominal voltage is 12 V. When this voltage decreases, the number of revolutions per unit time decreases - the fan rotates more slowly and makes less noise. You can take advantage of this circumstance by switching the fan to several voltage ratings using an ordinary Molex connector.

The distribution of voltages on the contacts of this connector is shown in fig. 1a. It turns out that you can take three different meanings voltages: 5 V, 7 V and 12 V.

To ensure this method of changing the fan speed, you need:

1. After opening the case of a de-energized computer, remove the fan connector from its socket. The wires leading to the power supply fan are easier to unsolder from the board or just have a snack.
2. Using a needle or an awl, release the corresponding legs (most often the red wire is a plus, and the black wire is a minus) from the connector.
3. Connect the fan wires to the contacts of the Molex connector for the required voltage (see Fig. 1b).

An engine with a rated rotation speed of 2000 rpm at a voltage of 7 V will give 1300 revolutions per minute, at a voltage of 5 V - 900 revolutions. An engine with a nominal value of 3500 rpm - 2200 and 1600 rpm, respectively.

Figure 2. Scheme of serial connection of two identical fans.

A special case of this method is the serial connection of two identical fans with three-pin connectors. Each of them has half the operating voltage, and both rotate more slowly and make less noise.

The scheme of such connection is shown in fig. 2. The left fan connector is connected to the motherboard as usual.

A jumper is installed on the right connector, which is fixed with electrical tape or tape.

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The third way: adjusting the fan speed by changing the value of the supply current

To limit the fan speed, you can connect fixed or variable resistors in series to its power circuit. The latter also allow you to smoothly change the speed of rotation. Choosing such a design, one should not forget about its disadvantages:

1. Resistors heat up, wasting electricity uselessly and contributing to the process of heating the entire structure.
2. The characteristics of the electric motor in different modes can be very different, each of them requires resistors with different parameters.
3. The power dissipation of the resistors must be large enough.

Figure 3. Electronic speed control circuit.

It is more rational to apply electronic circuit speed control. Its simple version is shown in Fig. 3. This circuit is a stabilizer with the ability to adjust the output voltage. A voltage of 12 V is applied to the input of the DA1 chip (KR142EN5A). A signal from its output is fed to the 8-amplified output by the transistor VT1. The level of this signal can be adjusted by a variable resistor R2. As R1, it is better to use a tuning resistor.

If the load current is not more than 0.2 A (one fan), the KR142EN5A chip can be used without a heat sink. If it is present, the output current can reach a value of 3 A. At the input of the circuit, it is desirable to include a small ceramic capacitor.

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The fourth way: adjusting the fan speed using reobas

Reobas is an electronic device that allows you to smoothly change the voltage supplied to the fans.

As a result, the speed of their rotation smoothly changes. The easiest way is to buy a ready-made reobas. It usually fits into a 5.25" bay. There is only one drawback: the device is expensive.

The devices described in the previous section are actually reobasses that allow only manual control. In addition, if a resistor is used as a regulator, the motor may not start, since the current is limited at the time of starting. Ideally, a full-fledged reobas should provide:

1. Uninterrupted engine start.
2. Rotor speed control not only in manual, but also in automatic mode. As the temperature of the cooled device increases, the rotation speed should increase and vice versa.

A relatively simple circuit that meets these conditions is shown in Fig. 4. Having the appropriate skills, it is possible to make it yourself.

Changing the supply voltage of the fans is carried out in a pulsed mode. Switching is carried out using powerful field-effect transistors, the channel resistance of which in the open state is close to zero. Therefore, the engine starts without difficulty. The highest speed will also not be limited.

The proposed scheme works like this: at the initial moment, the cooler that cools the processor runs at the minimum speed, and when heated to a certain maximum allowable temperature, it switches to the maximum cooling mode. When the processor temperature drops, the reobas switches the cooler back to the minimum speed. The rest of the fans support the manually set mode.

Figure 4. Scheme of adjustment using reobas.

The basis of the node that controls the operation of computer fans, the integral timer DA3 and field-effect transistor VT3. Based on the timer, a pulse generator with a pulse repetition rate of 10-15 Hz was assembled. The duty cycle of these pulses can be changed using the trimmer resistor R5, which is part of the timing RC circuit R5-C2. Thanks to this, it is possible to smoothly change the speed of rotation of the fans while maintaining the required amount of current at the time of start-up.

Capacitor C6 performs pulse smoothing, due to which the rotors of the motors rotate softer, without making clicks. These fans are connected to the XP2 output.

The basis of a similar processor cooler control unit is the DA2 chip and the VT2 field effect transistor. The only difference is that when the output operational amplifier DA1 voltage, it, thanks to the diodes VD5 and VD6, is superimposed on output voltage timer DA2. As a result, VT2 opens completely and the cooler fan starts to rotate as fast as possible.