Dimensions of the ATX power unit. Modern ATX power supplies and their characteristics. ⇡ Total ATX Power Supply Scheme

ATX (Advanced Technology Extended.) - Form factor for desktop PCs. From the moment of its release, the market that occurred in 2001, this form factor acts as a leading standard in the market of mass-produced form factors for computer systems.

ATX defines the following motherboard parameters:

• Motherboard geometry;
• Basic requirements for the position of connectors and holes on the housing;
• The form and location of some connectors (mainly power connectors);
• Geometry sizes of the power supply;
• The location of the power supply on the housing;
• Electrical power supply parameters;

Dimensions of the board

Name	Board dimensions (mm)
Eatx (Extended)
microbtx.
Ultra ATX
Mini-dtx
microatx (min.)
Mini-ITX
EPIC. Express
Mini ATX
Nano-ITX
COM EXPRESS.
Esmexpress.
Pico-ITX
PC / 104. (-Plus)
mobile-ITX
CoreExpress.

History

ATX Form factor was created and published among computer systems producers in 1995. The author of the development is Intel. The ATX standard performed in the role of a logical alternative and evolutionary substitution used for a long time and an already obsolete-standard AT standard.

In addition to Intel, and other OEM equipment companies began to actively produce motherboards and power supplies to them (as well as other components) in the new ATX form factor. The global extrusion of the old standard accounted for the end of 1999 - the beginning of 2001. At that time, other modern standards ( microatx, Flexatx, Mini-ITXFor the most part, you have saved the imprint of the key features of the ATX standard, changing only the size of the boards and the number of slots.

In the course of its development, the ATX specification has passed the following evolution of standards:

• ATX 1.0 Standard.
• ATX 1.1 Standard.
• ATX 1.2 Standard.
• ATX 1.3 Standard.
• ATX 2.0 Standard.
• ATX 2.1 Standard.
• ATX 2.2 Standard.
• ATX 2.3 Standard.

In 2003, Intel was made public new standardcalled BTX. It was created to increase the level and intensity of cooling system Block. The ATX replacement was due to the increasing thermal power of the computer components. First of all, it was processors. Started new stage The transition to a new format, which, however, has soon stopped. Most of the representatives of the computer industry abandoned the mass distribution of the new format due to the reduction of power pC components.

To this day, ATX and its derivatives are the most common factors in the market, and in the foreseeable future there is no more interesting alternative to them.

The key differences of ATX from AT

• The motherboard is responsible for food processor. To ensure the operation of the control unit, as well as some peripheral devicesThe board is sent to the duty voltage of 5 / 3.3 volts. Despite the fact that in many instructions in order to safely replace components, ultimately require disconnecting the power cord from the outlet, many ATX power supplies are equipped with a tearing switch installed directly on the housing.
• The fan located on the rear wall of the power supply can be supplemented or replaced by a 12/14 cm fan, which is installed at the bottom of the power supply. This makes it possible to create a large-volume air flow with smaller turnover, which, accordingly, leads to a decrease in noise level. The location of the elements on the motherboard was carried out in such a way that the processor radiator is installed on the air flow path from the power supply fan.
• Power connector has become different. In order to impossible incorrectly connecting two power connectors on each other (as it was in the previous standard), the ATX standard is equipped with a key connector that cannot be connected incorrectly. Due to the increase in power consumed, the number of contacts in the ATX power connector increased at first to 20, and then - to 24.
• Received modernization I. rear panel Cases. The AT standard possessed only a hole for the keyboard connector on the rear panel. Other devices were connected via special boards with connectors installed on the motherboard and attached to special slotted slits. The ATX standard is characterized by the fact that it is located on top of the keyboard connectors (and mouse) by tradition, the rest occupies a rectangular opening of a fixed size, which, depending on the manufacturer of the motherboard, can be filled with various connectors in any arbitrary order. Complete with the motherboard comes a special "plug" with slots for a specific motherboard. It is very convenient because the user appears to appear to use the same case with motherboards equipped with completely different sets of connectors. Also, this "plug" has some other functions: it reduces the emitted Amy and forms a single chassis grounding circuit.

Connectors and plug

The metal "plug", located in the rear of the housing, performs a very important function. Thanks to it, manufacturers motherboards In the process of integrating into their products, various interface devices can be completely free to position the connectors without conducting the coordination of their position with the manufacturers of the housings.

The only discharge requirement is external geometric dimensions:

• width: 158.75 ± 2 mm;
• height: 44.45 ± 2 mm;
• thickness ranging from 0.94 to 1.32 mm;
• rounding panel not more than 0.99 mm.

Standard connectors in ATX-case are:

• PS / 2 Connector for connecting the keyboard and mouse. On some cases, a universal connector is installed that supports both devices. But currently a general trend of changing this jack on a modern USB-interface is traced. However, among budget plantsThese connectors are still used.
• 3.5 mm connectors (from 3 to 6 pieces) integrated sound card. They include:
  • linear output (green);
  • line input (blue);
  • microphone input (pink);
• USB connectors (4 - 8);
• Connector for connecting to a local network.

In addition, the following connectors can be installed:

• Parallel communication port;
• Serial port (1-2) - simple 9-pin connector;
• Game port for connecting the joystick or synthesizer;
• Digital audio outputs (coaxial and / or optical);
• Built-in video adapter;
• Integrated video output (D-Sub, S-Video, DVI or HDMI);
• Second port for integrated network cards;
• IEEE 1394 interface;
• Connector for wifi antenna;
• BIOS Fast Restart Button.

how to choose the case to the motherboard and got the best answer

Reply from Andrei Bobrovsky [Guru]
Form factor
Motherboard form factor.
The form factor determines the dimensions, installation holes, motherboard power connectors, as well as the cooling system requirements. When choosing components for a computer, it is necessary to remember that the computer case must support the motherboard form factor. Possible motherboard form factors: ATX, MICROATX, EATX, BTX, MBTX, MINI-ITX, SSI EEB, SSI CEB, non-standard.
ATX (Advanced Technology Extended) is one of the most common formats of PC motherboards, ideal for building a home computer. ATX cards have dimensions of 30.5 x 24.4. cm and maintain seven expansion slots. The main connector for connecting the power supply unit on the ATX motherboard may have 20 or 24 contacts. Almost all new motherboard models have a 24-pin connector.
MicroAtx (MATX) is a slightly reduced ATX standard. Suitable for building office computers when there are no slots for expanding the system. MicroATX cards have dimensions 24.4 x 24.4 cm and maintain four expansion slots. The main connector for connecting the power supply on the MICROATX motherboard can have 20 or 24 contacts. Almost all new motherboard models have a 24-pin connector.
FlexATX is a form factor that in the future should come to a change of Microatx. Currently, he has not been greatly popular. FlexATX boards have a size of 22.9 x 19.1 cm and no more than 3 expansion slots.
EATX (Extended ATX) Motherboards are different from ATX dimensions (up to 30.5 x 33.0 cm), are used mainly for servers.
BTX (Balanced Technology Extended) is a new standard that comes to replace ATX. When developing this form factor, much attention was paid to the efficient cooling of the elements installed on the board. BTX is ideal for building miniature computers. BTX motherboards have dimensions of 26.7 x 32.5 cm and support seven expansion slots.
mBTX (Micro BTX) - Reduced BTX option. The dimensions of such boards are 26.7 x 26.4 cm. MBTX support four expansion slots.
mINI-ITX is a form factor for motherboards developed by Via Technologies. Electrically and mechanically compatible with ATX Form Forms. Maternal mINI-ITX boards Have small dimensions (17 x 17 cm).
SSI EEB (Server Standards Infrastructure Entry Electronics Bay). Motherboards of this standard usually serve to build servers. Connectors for connecting the power supply have 24 + 8 contacts. The dimensions of such boards are 30.5 x 33.0 cm.
SSI CEB (SSI COMPACT ELECTRONICS BAY). Motherboards of this standard usually serve to build servers. Connectors for connecting the power supply have 24 + 8 contacts. Dimensions of such boards make up 30.5 x 25.9 cm.
Sometimes you can meet motherboards non-standard form factor (Proprietary). They are designed to be installed in a special, compatible housing.

Good day, dear readers of our technoblog. Today we will look at the main forms of motherboard factors as of 2018. We immediately want to refine that the classification will include only devices for home use. There are no modern servers MP CEB and EEB, although we will also talk about them in the future.

From this article you will learn:

What will the review be? Here you will receive comprehensive information on the maximum size of the board, the number of ports used, the layout of the connectors and not only. We hope our article will help you determine the optimal motherboard for the computer, if you have not done this yet.

Is the choice?

To date, several popular types are common on the market, or rather form factors of system boards. From the key to note:

• E-ATX;
• Microatx;
• MINI-ITX;
• MINI-STX.

How to find out and determine the optimal format? Here let's get together and understand, and at the same time we painse on the topic, which form factor is better.

ATX

ATX (Advanced Technology Extented) - The most common standard MP is currently. Intel was developed in the distant already in 1995 as an alternative to the AT form factor at that time, but real fame found only since 2001. Of the basic differences from the predecessor, it is worth noting the following:

• Power management of the processor forces by the motherboard. The process occurs even in the off state: on the CPU and some peripheral connectors are systematically fed voltage to 5 or 3.3 volts;
• The power circuit is significantly changed in the more familiar option 24 + 4 or 24 + 8 PIN;
• The rear panel received a fixed rectangular size, and all components and peripheral devices are now connected without the use of adapters and additional loops. Each manufacturer of the MP can arbitrarily change the location of the outputs, allowing the plug to the rear of the system unit;
• The mouse and keyboard have a standard PS / 2 connector (now mostly USB).

All power connectors on the motherboard are located along the edges of the textolite, providing both aesthetic beauty and the convenience of connecting peripheral devices and power supply. In the central part focused socket, slots under RAM, PCI-EX, and the south bridge.
Standard size - 305x244 mm. For mounting to the housing, 8 to 9 mounting holes are provided.

E-ATX

E-ATX (Extented - Advanced) - Derived case from ATX, which differs primarily, the size of the board is 305x330 mm. Often on the basis of this system board Top gamers are gather under current sockets 1151, 2066 (Intel), AM4 and TR4 (AMD).

The key difference from the standard ATX is more expansion slots (up to 8 ports under rAM), a more thought-out system of nutrition of components, improved cooling and, which happens quite often, its regular one.

Separately, I want to mention the server dual-processor maternal E-ATX fees. Additional 86 mm allow you to easily place on one sheet of textolite to 16 ports for RAM and expansion slots (video cards, network cards, RAID controllers).

Of the disadvantages it is worth noting only the selection of the appropriate case, since the overwhelming majority of MIDI-Tower solutions for ATX-cards are simply not suitable.

Microatx

MicroATX (MATX, UATX, μATX) - Another derivative of ATX, which was created all the same Intel in 1997. Cards of this form factor are practically no different from standard analogs, in one exception - dimensions of 244x244 mm, which cuts off the entire bottom panel with extension ports and moves SATA ports to side panelOptimizing the available space of textolite.

The mounting holes are done in such a way that Microatx can be installed in standard ATX builds without any problems. , socket and other architectural moments are not affected.
The standard was initially conceived as an office, and therefore a set of peripherals and a connection ports in MicroATX more modest than a full-format analog. However, modern models without problems are created on the basis of the board base for the following PCs:

• server;
• multimedia;
• gaming;
• workstations;
• HTPC;
• render machine.

The only drawback in essence is the impossibility of connecting the second video card due to the lack of the second full PCI-E x16.

Mini-ITX

Mini-ITX - An even more compact version of ATX, only its dimensions do not exceed 170x170 mm. Mechanical compatibility with all components and support for modern chips is preserved. The form factor was created in 2001 by Via Technologies with the sole purpose - to promote its own processor, but something went wrong, and the stone did not get popularity, which you can't tell about MP.

A distinctive feature of the MINI-ITX is a built-in processor in some models of boards, which are planted by the manufacturer at the factory. It will not be replaced from the word at all. On the one hand, the decision is not the most practical decision, but on the other - this procedure significantly reduces the cost of production (no need to think over the insertion of the socket) and the final cost of the product. Architecture allows you to create as cold as possible (TDP built-in CPU does not exceed 15 W), silent and fast office stations (SSD + 16 GB of RAM DDR4 2400 MHz).
The perfect solution for the HTPC or multimedia center. Although gaming system On this board can also be built. It suffices to look at MSI B350i Pro AC. The board has standard nutrition and supports the acceleration of components. Add Ryzen 5 2400G and get the perfect system for the soul.

Mini-stx

MINI-STX (Mini Socket Technology Extended) - relatively fresh standard developed by all the same Intel. It has dimensions of 147x140 mm, which is comparable to the envelope for the DVD.

From Mini-ITX is distinguished by the complete lack of support for PCI-E x16 connectors, as well as a modified port for connecting BP. Here, the yield has a pin look, like in most modern laptops. In part, this step is dictated by the fact that the fee and components on it are low-power. On the other hand, unpack 24 + 4 PIN on such an area is somehow inhuman.

To create a full-fledged PC, it is possible to connect SATA or M.2-drives, RAM and processor with a built-in video frame. Miniature dimensions will allow placing a fee into a miniature case with dimensions with PS4 or Xbox One.

The main drawback is the need for MINI-STX cards.

conclusions

So, the comparison of various architectures is reduced mainly to dimensional indicators and quantity on the board. In a good way, the need for ATX-models every year is even lower, since MicroATX offers similar functionality and do not require the case more MID-Tower. Lack of additional PCI-E x16 / x8 / x4 slots?

The modern industry refuses to further support SLI and Crossfire, which makes it impracticable to powering additional slots, unless you are engaged in mining, or want to connect an ultrafast NVME SSD, a capture card or an ASUS Xonar audio card.

We hope we helped you with the choice of motherboard for your future system. What it will be - another thing, but the main idea is obtained, now it would be necessary to implement it. Good luck! Do not forget and share with loved ones while.

Linear I. pulse sourceand nutrition

Let's start with the basics. The power supply in the computer performs three functions. First, the alternating current from the consumer network of the power supply must be converted to a permanent one. The second task of BP is to reduce the voltage of 110-230 V, redundant to computer electronics, To standard values \u200b\u200brequired by the power converters of individual components of the PC, - 12 V, 5 V and 3.3 V (as well as negative voltages that we will tell a little later). Finally, BP plays the role of stress stabilizer.

There are two main types of power supplies that perform listed functions - linear and pulsed. The simplest linear BP is based on a transformer on which the AC voltage drops to the desired value, and then the current is straightened with a diode bridge.

However, it also requires stabilization of output voltage, which is due to both the voltage instability in the household network, and the voltage drop in response to an increase in current in the load.

To compensate for the voltage drop in linear BP, the transformer parameters are calculated so as to provide redundant power. Then, at high current in the load, the required voltage will be observed. However, both the increased voltage that will arise without any means of compensation at low current in the payload is also unacceptable. Excessive voltage is eliminated due to the inclusion in the non-disabilities circuit. In the simplest case, there is a resistor or transistor connected via Stabilod (ZENER DIODE). In a more advanced - the transistor is controlled by a microcircuit with a comparator. Be that as it may, excessive power simply dissipates in the form of heat, which adversely affects the efficiency of the device.

Another variable occurs in the pulse BP scheme, from which the outlet voltage depends, in addition to the two already available: voltage at the inlet and load resistance. Consistently with the load is a key (which in the case of interest is the transistor) controlled by a microcontroller in a latitude and pulse modulation mode (PWM). The higher the duration of the open states of the transistor with respect to their period (this parameter is called Duty Cycle, in Russian-language terminology, the reverse value is used - well), the higher the output voltage. Due to the presence of a key pulse BP is also called Switched-Mode Power Supply (SMPS).

Through the closed transistor, the current does not go, and the resistance of the open transistor is ideally negligible. In fact, the open transistor has resistance and dispels some part of the heat in the form of heat. In addition, the transition between the transistor states is not perfectly discrete. And yet the efficiency of the impulse current source may exceed 90%, while the efficiency of the linear BP with the stabilizer at best reaches 50%.

Another advantage of impulse power supply consists of radical decrease in the dimensions and mass of the transformer compared to linear BP of the same power. It is known that the higher the frequency of alternating current in the primary winding of the transformer, the smaller the required core size and the number of turns of the winding. Therefore, the key transistor in the chain is placed not after, and to the transformer and, in addition to stabilization, the voltage is used to obtain an AC high frequency (for computer BP, it is from 30 to 100 kHz and above, and as a rule - about 60 kHz). A transformer operating at a power frequency of 50-60 Hz, for the power required by the standard computer, would be tens of times more massive.

Linear BPs are used mainly in the case of low-power devices, when relatively complex electronics needed for a pulsed power source is a more sensitive cost of expenses in comparison with the transformer. This, for example, power supplies by 9 V, which are used for guitar pedals of effects, and once - for game consoles, etc. But the chargers for smartphones are already completely impulse - there are justified expenditures. Due to the significantly less amplitude of the voltage pulsations at the outlet, linear BP is also used in areas where the quality is in demand.

⇡ Total ATX Power Supply Scheme

Bp desktop computer It is a pulsed power source, the input of which is supplied to the voltage of household electrical circuit with parameters 110/230 V, 50-60 Hz, and at the output there are a number of lines direct currentThe mains of which have a denomination 12, 5 and 3.3 V. In addition, the BP provides a voltage -12 B, and once also voltage -5 in the ISA tire. But the latter at some point was excluded from the ATX standard in connection with the termination of the support of the ISA itself.

On the simplified scheme of the standard pulsed BP presented above, four main stages can be distinguished. In the same order, we consider the components of the power supplies in the reviews, namely:

1. eMF filter - electromagnetic interference (RFI Filter);
2. primary chain - input rectifier (RECTIFIER), key transistors (Switcher), creating an alternating current of high frequency on the primary winding of the transformer;
3. main transformer;
4. secondary chain - current rectifiers with secondary transformer winding (Rectifiers), smoothing output filters (Filtering).

⇡ Filter EMP.

The Filter at the input of the BP serves to suppress two types of electromagnetic interference: differential (differential-mode) - when the interference current flows in different directions in the power lines, and the syphase (Common-mode) - when the current flows in one direction.

Differential interference is suppressed by CX capacitor (large yellow film capacitor in the photo above), parallel to the load. Sometimes the throttle performs the same function for each wire (no in the diagram).

The filter of the syphaseous interference is formed by CY capacitors (blue drop-shaped ceramic capacitors in the photo), as a common point in the connecting lines of the Earth, and the so-called. The syphase choke (COMMON-MODE CHOKE, LF1 in the diagram), the current in two windings of which flows in one direction, which creates resistance for syphase interference.

In cheap models, the minimum set of filter parts set, in more expensive schemes described forming repeating (fully or partially) links. In the past, BP was often met without the EMF filter. Now it is rather a curious exclusion, although, buying a very cheap BP, you can still run into such a surprise. As a result, it will suffer not only and not so much the computer itself, how much other technique included in the household network - impulse BPs are a powerful source of interference.

In the area of \u200b\u200ba good BP filter, you can find several parts that protect against damage the device itself is either its owner. Almost always has the simplest fuse for protection against short circuit (F1 in the diagram). Note that when the fuse is triggered, the protected object is no longer a power supply. If the KZ happened, then the key transistors already struck, and it is important to at least prevent the fire wiring. If the fuse suddenly burned down, then change it to a new one, most likely, is already meaningless.

Separately protection from short-term Voltage jumps with a varistor (MOV - Metal Oxide Varistor). But there are no means of protection against a long-term increase in voltage in computer BP. This function is performed by external stabilizers with their transformer inside.

The capacitor in the PFC circuit after the rectifier can retain a significant charge after disconnecting from the power. In order for a careless person who has thrown a finger into the power connector, the discharge resistor of the large nominal (Bleeder Resistor) is installed between the wires. In a more sophisticated version, along with the control circuit, which does not charge to flow when the device does not allow.

By the way, the presence of a filter in the PC power supply (and in the BP of the monitor and almost any computer equipment He also is) means buying a separate " network filter"Instead of an ordinary extension, in general, without a sense. He has all the same inside. The only condition in any case is a normal three-pin wiring with a grounding. Otherwise, CY capacitors connected to Earth simply will not be able to perform their function.

⇡ Input rectifier

After the filter, the alternating current is converted to constant with a diode bridge - as a rule, in the form of assembly in a common case. A separate radiator for cooling the bridge is welcome in every way. The bridge collected from four discrete diodes is the attribute of cheap power supplies. You can also ask for what current the bridge is calculated to determine whether it corresponds to the power of the BP itself. Although this parameter, as a rule, there is a good stock.

⇡ Block active PFC

In the AC circuit with a linear load (as, for example, an incandescent or electrolycin lamp) flowing current follows the same sinusoid, as well as voltage. But this is not so in the case of devices having an input rectifier, such as impulse BP. The power supply passes the current with short pulses, roughly coinciding with the peaks of the voltage sinusoids (that is, the maximum instant voltage) when the smoothing capacitor of the rectifier is recharged.

The signal of the currently distorted form is folded into several harmonic oscillations in the amount with a sinusoid of this amplitude (the ideal signal that would have a place with a linear load).

Power used to commit useful work (which, in fact, is the heating of PC components), indicated in the characteristics of the BP and is called active. The remaining power generated by the harmonic fluctuations in the current is called reactive. It does not produce useful work, but heats the wires and creates a load on transformers and other power equipment.

The vector amount of reactive and active power is called full power (Apparent Power). And the ratio of active power is called the power factor (Power Factor) - not to be confused with the efficiency!

In a pulsed bp, the power coefficient is initially rather low - about 0.7. For private consumer reactive power It does not constitute problems (good it is not taken into account by electric meters), unless he uses the UPS. On the uninterrupted man, the full load capacity lies. On the scale of the office or the urban network, the excessive reactive power generated by pulse BP already significantly reduces the quality of the power supply and causes expenses, therefore it is actively struggling with it.

In particular, the overwhelming majority of computer BP are equipped with active power factor correction schemes (Active PFC). A block with active PFC is easy to identify in a single major condenser and a throttle installed after the rectifier. In essence, Active PFC is another impulse converter, which supports on the condenser a constant charge of about 400 V. The current from the supply network is consumed by short pulses, the width of which is selected in such a way that the signal is approximated by the sinusoid - which is required to simulate a linear load. . To synchronize a current consumption signal with a voltage sinusoid in the PFC controller, there is a special logic.

The active PFC scheme contains one or two key transistors and a powerful diode that are placed on one radiator with key transistors of the main converter of BP. As a rule, the PWM key controller of the main converter and the Active PFC key is a single microcircuit (PWM / PFC Combo).

The power factor in pulse power supplies with active PFC reaches 0.95 and higher. In addition, they have one additional advantage - no key switch 110/230 V and the corresponding voltage double tensioner inside the BP. Most PFC circuits digest voltages from 85 to 265 V. In addition, the sensitivity of the BP is reduced to short-term voltage failures.

By the way, in addition to the active correction of PFC, there is a passive, which implies the installation of a large inductance choke consistently with the load. Effectiveness is small, and in modern BP you are hardly finding.

⇡ Main converter

The general principle of operation for all impulse BPs of an insulated topology (with a transformer) One: The key transistor (or transistors) creates an alternating current on the primary winding of the transformer, and the PWM controller controls the well to switch them. Specific schemes, however, differ in both the number of key transistors and other elements and by quality characteristics: efficiency, signal form, interference, etc. But here too much depends on the specific implementation, so that it costs attention. For those interested, we give a set of schemes and a table, which will allow the part of the parts to identify them in specific devices.

	Transistors	Diodes	Condencators	Legs of the primary winding of the transformer
Single-TRANSISTOR FORWARD	1	1	1	4
	2	2	0	2
	2	0	2	2
	4	0	0	2
	2	0	0	3

In addition to the listed topologies, there are resonant (resonant) options for Half Bridge, which are easy to identify on an additional large throttle (or two) and condenser forming an oscillating circuit.

Single-TRANSISTOR FORWARD

⇡ Secondary chain

The secondary chain is all that is after the secondary winding of the transformer. In most modern power supplies, the transformer has two windings: a voltage of 12 V is removed from one of them, on the other - 5 V. The current is first straightened by assembling from two Schottki diodes - one or more on the bus (on the highest bus - 12 V - 12 V - In powerful BP there are four assemblies). More efficient from the point of view of the efficiency are synchronous rectifiers in which field transistors are used instead of diodes. But it is prerogative for truly advanced and expensive BPs claiming 80 Plus Platinum certificate.

The tire is 3.3 V, as a rule, is output from the same winding as the bus 5 V, only the voltage is reduced using a saturated choke (MAG AMP). Special winding on a voltage transformer 3.3 V is an exotic option. Of the negative stresses in the current ATX standard, it remains only -12 B, which is removed from the secondary winding under the 12 V bus through separate low-voltage diodes.

PWM-control of the converter key changes the voltage on the primary winding of the transformer, and therefore on all secondary windings at once. In this case, the current consumption of the computer is not evenly distributed between the BP tires. In modern hardware, the most loaded tire is 12-in.

For separate stabilization of voltages on different tires required additional measures. A classic way implies the use of group stabilization throttle. The three main tires are missed through its windings, and as a result, if the current increases on the same bus, then the voltage drops on others. Suppose on the tire 12 in the current increase, and to prevent the voltage drop, the PWM controller reduced the diversity of the key transistors. As a result, on the bus 5, the voltage could be released for the permissible framework, but the group stabilization throttle was suppressed.

Voltage on the tire 3.3 V is additionally adjusted by another saturated choke.

In a more perfect version, a separate stabilization of tires 5 and 12 in due to saturated chokes is ensured, but now this design in expensive high-quality BP gave way to DC-DC converters. In the latter case, the transformer has a single secondary winding with a voltage of 12 V, and the voltage 5 V and 3.3 V are obtained due to DC converters. This method is most favorable for stress stability.

Output filter

The final stage on each bus is a filter that smoothes the voltage ripple caused by key transistors. In addition, the pulsations of the input rectifier, whose frequency is equal to the double frequency of the supply power supply in one way or another.

Pulsation filter includes choke and high-capacity capacitors. For high-quality power supplies, a capacity of at least 2,000 Igf is characterized, but manufacturers of cheap models have a reserve for savings when condensers are installed, for example, twice as smaller nominal, which is inevitably reflected on the amplitude of riscents.

⇡ duty nutrition + 5VSB

The description of the components of the power supply would be incomplete without mentioning the source of the 5 V voltage source, which makes it possible to sleep PC mode and ensures the operation of all devices that must be turned on constantly. "Digeon" is powered by a separate pulse converter with a low-power transformer. Some BP meets the third transformer used in the chain feedback To insulate the PWM controller from the primary chain of the main converter. In other cases, optocouplers (LED and phototransistor in one case) are performed this function.

⇡ Testing methods for power supplies

One of the main parameters of BP is the stability stability, which is reflected in the so-called. Cross load characteristic. The CNC is a diagram in which the current or power on the tire 12 V is postponed on the same axis, and on the other - the total current or power on tires 3.3 and 5 V. At the intersection points at different values \u200b\u200bof both variables, the voltage deviation from the nominal value is determined This tire. Accordingly, we publish two different CNHs - for tires 12 V and for tires 5 / 3.3 V.

The color of the point means the percentage of deviation:

• green: ≤ 1%;
• salad: ≤ 2%;
• yellow: ≤ 3%;
• orange: ≤ 4%;
• red: ≤ 5%.
• white:\u003e 5% (not allowed by the ATX standard).

To obtain the book, it is used to order a booth to test power supplies, which creates a load due to heat dissipation on powerful field transistors.

Another equally important test is determining the scope of pulsations at the output of BP. The ATX standard admits pulsation within 120 mV for a bus 12 V and 50 mV - for the 5 V. bus distinguishes high-frequency pulsations (on the double frequency of the key of the main converter) and low-frequency (on the double frequency of the supply network).

We measure this parameter using a HANTEK DSO-6022BE USB oscilloscope at maximum load on BP specified by specifications. On the oscillogram below the green graph corresponds to the 12 V bus, yellow - 5 V. It can be seen that pulsations are within the normal range, and even with a margin.

For comparison, we give the pattern of pulsations at the output of the BP of the old computer. This block was not initially outstanding, but clearly did not become better from time to time. Judging by the wise of low-frequency pulsations (note that the division of voltage sweep is increased to 50 mV so that the oscillations fit on the screen), the smoothing capacitor at the entrance has already become unusable. High-frequency pulsations on the 5-B tire are on the verge of permissible 50 mV.

The following test is defined by the efficiency of the block with a load from 10 to 100% of the rated power (by comparing the power at the outlet power with the power at the inlet measured using a domestic wattmeter). For comparison, the graph provides criteria for various categories of 80 Plus. However, there is no big interest in our days. The graph shows the results of the Top BP Corsair in comparison with a very cheap ANTEC, and the difference is not very high.

A more urgent question is noise from the built-in fan. It is impossible to directly measure it near the roaring bench for testing of the BP, so we measure the speed of rotation of the impeller with a laser tachometer - also with power from 10 to 100%. The graph below shows that with a low load on this BP, a 135 mm fan retains low revs and is unlikely to be heard at all. At maximum load, noise can already be distinguished, but the level is still quite acceptable.

# XL-ATX # enhanced_e-atx # e-atx #ssi_ceb #atx #Microatx #FlexATX # mini-dtx # mini-itx

ATX (Advanced Technology Extended) - Created in 1995, describing the geometric dimensions and, methods of their conjugation, as well as the geometric and electrical parameters of the power supplies, their ways to connect to motherboards and interacting with them.

Visual comparison of the sizes of motherboards of popular formats of the ATX family:

A more complete list of famous sizes of motherboards:

Used or planned to use in computers now:

Name	Board size (mm)	Comments:
XL-ATX	345 × 262. (325 × 244)	XL-ATX. The first representative of this form factor was the maternal gigabyte board GA-890FXA-UD7, published on April 1, 2010. XL-ATX card boards are longer than standard ATX boards and allow you to create a motherboard with the possibility of installing up to 10 extension boards. The length of the motherboard does not allow you to install it in the housings calculated on ATX or E-ATX fees, so it is necessary to choose special cases.
Enhanced E-ATX	347 × 330.	The branded extension E-ATX from Supermicro. The board is wider (from the BP) standard EATX card by 32 mm, which requires the corresponding case. Usually this format is indicated simply as E-ATX (347 × 330)
E-ATX	305 × 330.	Extended ATX. The most popular format of boards and enclosures for two-processor workstations and servers. Second name SSI EEB
SSI CeB.	305 × 267.	Format of motherboards for workstations. Recently, boards began to appear this format for game computers. Possible installation of boards of this format in the E-ATX case
ATX	305 × 244.	The most popular (together with microatx) motherboard format. In practice, fees can be shorter, up to 305 × 170
microatx	244 × 244.	The most popular (together with ATX) format of motherboards. In practice, fees may be shorter, up to 244 × 170
Flexatx	229 × 191.	Reduced Microatx option proposed by Intel
Mini-dtx	203 × 170.
Mini-ITX	170 × 170.

Other formats of motherboards that are not fully compatible with ATX.

Outdated or not found mass applications:

Name	Board size (mm)	Comments:
WTX	356 × 425.	Workstation ATX - Meets, as, the rule, only in brand-name fourprocessor platforms, like SWTX close to it
AT.	350 × 305.	Original motherboard formats for personal computersProposed by IBM and dominated the market until the end of the 90s of the 20th century. As a rule, most Baby-AT format boards can be installed in ATX housing.
Baby-At.	330 × 216.		DTX.	244 × 203.	Reduced Microatx options proposed by AMD.
NLX	254 × 228.	Original "branded" standards large manufacturers PC. Microatx was completely ousted.
LPX	330 × 229.
BTX	325 × 266.	The format that was developed as a replacement ATX, but did not.
microbtx.	264 × 267.
Nano-ITX	120 × 120.	Reduced Microatx options proposed by VIA.
Pico-ITX	100 × 72.
mobile-ITX	60 × 60.	The format of ultra-compact motherboards for mobile and embedded computers is also proposed by VIA

Used in industrial and embedded equipment: