Directory in .chm format. The author of this file is Kucheryavenko Pavel Andreevich. Most of the original documents were taken from the site pinouts.ru - brief descriptions and pinouts of more than 1000 connectors, cables, adapters. Descriptions of tires, slots, interfaces. Not only computer equipment, but also cell phones, GPS receivers, audio, photo and video equipment, game consoles and other equipment.

The program is designed to determine the capacitance of the capacitor by color marking (12 types of capacitors).

Transistor database in Access format.

Power supplies.

Wiring for ATX standard power supply connectors (ATX12V) with ratings and wire color coding:

Table of pins for the 24-pin ATX power supply connector (ATX12V) with ratings and color coding of wires

A typical 450W power supply circuit with the implementation of active power factor correction (PFC) of modern computers.

A typical 300W power supply circuit with notes on the functional purpose of individual parts of the circuit.

Schematic diagram of API3PCD2-Y01 450w power supply manufactured by ACBEL ELECTRONIC (DONGGUAN) CO. Ltd.

Diagram of the API4PC01-000 400w power supply manufactured by Acbel Politech Ink.

Alim ATX 250Watt SMEV J.M. 2002.

ATX-300P4-PFC power supply circuit (ATX-310T 2.03).

Schematic diagram of the ATX-P6 power supply.

ATX 250 SG6105, IW-P300A2 power supply schematics, and 2 circuits of unknown origin.

Schematic PSU CHIEFTEC TECHNOLOGY 350W GPS-350EB-101A.

Schematic PSU CHIEFTEC TECHNOLOGY 350W GPS-350FB-101A.

Chieftec CTG-350-80P, CTG-400-80P, CTG-450-80P and CTG-500-80P

Diagram of Chieftec CFT-370-P12S, CFT-430-P12S, CFT-460-P12S power supplies

Chieftec 400W iArena GPA-400S8 power supply diagram

PSU diagram Chieftec 500W GPS-500AB-A.

Schematic PSU CHIEFTEC TECHNOLOGY GPA500S 500W Model GPAxY-ZZ SERIES.

Schematic diagram of Chieftec CFT-500A-12S, CFT-560A-12S, CFT-620A-12S power supplies

Schematic diagram of Chieftec 550W APS-550S power supplies

Schematic diagram of Chieftec 650W GPS-650AB-A and Chieftec 650W CFT-650A-12B power supplies

Schematic diagram of Chieftec 650W CTB-650S power supplies

Chieftec 650W CTB-650S power supply circuit Board marking: NO-720A REV-A1

Schematic diagram of Chieftec 750W APS-750C power supplies

Schematic diagram of Chieftec 750W CTG-750C power supplies

Power supply diagram Chieftec CFT-600-14CS, CFT-650-14CS, CFT-700-14CS, CFT-750-14CS

Schematic diagram of the Chieftec 850W CFT-850G-DF power supply

Schematic diagram of Chieftec 1000W CFT-1000G-DF and Chieftec 1200W CFT-1200G-DF power supplies

PSU diagram NUITEK (COLORS iT) 330U (sg6105).

PSU diagram NUITEK (COLORS iT) 330U on the SG6105 chip.

PSU diagram NUITEK (COLORS iT) 350U SCH.

PSU diagram NUITEK (COLORS iT) 350T.

PSU diagram NUITEK (COLORS iT) 400U.

PSU diagram NUITEK (COLORS iT) 500T.

Schematic PSU NUITEK (COLORS iT) ATX12V-13 600T (COLORS-IT - 600T - PSU, 720W, SILENT, ATX)

Schematic PSU Codegen 250w mod. 200XA1 mod. 250XA1.

Schematic PSU Codegen 300w mod. 300X.

PSU diagram CWT Model PUH400W.

Dell 145W SA145-3436 Power Supply Diagram

Dell 160W PS-5161-7DS Power Supply Diagram

Dell 230W PS-5231-2DS-LF power supply schematic (Liteon Electronics L230N-00)

Dell 250W PS-5251-2DFS Power Supply Diagram

Diagram of power supply unit Dell 280W PS-5281-5DF-LF model L280P-01

Diagram of power supply unit Dell 305W PS-6311-2DF2-LF model L305-00

Diagram of power supply unit Dell 350W PS-6351-1DFS model L350P-00

Dell 350W Power Supply Parts List PS-6351-1DFS Model L350P-00

PSU Diagram Delta Electronics Inc. model DPS-260-2A.

Delta 450W GPS-450AA-101A Power Supply Diagram

Diagram of the power supply unit Delta DPS-470 AB A 500W

Diagram of the power supply DTK PTP-1358.

Schematic diagram of the power supply DTK PTP-1503 150W

Schematic diagram of the power supply DTK PTP-1508 150W

PSU diagram DTK PTP-1568.

PSU diagram DTK PTP-2001 200W.

PSU diagram DTK PTP-2005 200W.

PSU diagram DTK Computer model PTP-2007 (aka MACRON Power Co. model ATX 9912)

PSU diagram DTK PTP-2007 200W.

PSU diagram DTK PTP-2008 200W.

PSU diagram DTK PTP-2028 230W.

PSU diagram DTK PTP-2038 200W.

Schematic diagram of the power supply DTK PTP-2068 200W

PSU diagram DTK Computer model 3518 200W.

PSU diagram DTK DTK PTP-3018 230W.

Schematic diagram of the power supply DTK PTP-2538 250W

Schematic diagram of the power supply DTK PTP-2518 250W

Schematic diagram of the power supply DTK PTP-2508 250W

Schematic diagram of the power supply DTK PTP-2505 250W

PSU diagram EC model 200X.

PSU diagram FSP Group Inc. model FSP145-60SP.

Scheme of the standby power supply of the FSP Group Inc. model ATX-300GTF.

Scheme of the standby power supply of the FSP Group Inc. model FSP Epsilon FX 600 GLN.

Schematic diagram of the Green Tech PSU. model MAV-300W-P4.

HIPER HPU-4K580 power supply schematics. In the archive - a file in SPL format (for the sPlan program) and 3 files in GIF format - simplified circuit diagrams: Power Factor Corrector, PWM and power circuit, oscillator. If you have nothing to view .spl files, use diagrams in the form of pictures in .gif format - they are the same.

INWIN IW-P300A2-0 R1.2 power supply circuits.

INWIN IW-P300A3-1 Powerman power supply circuits.
The most common malfunction of the Inwin power supplies, the circuits of which are given above, is the failure of the + 5VSB (duty) voltage generation circuit. As a rule, the electrolytic capacitor C34 10uF x 50V and the protective zener diode D14 (6-6.3 V) need to be replaced. In the worst case, R54, R9, R37, U3 chip (SG6105 or IW1688 (full analogue of SG6105)) are added to the faulty elements.

Powerman IP-P550DJ2-0 power supply circuit (IP-DJ Rev: 1.51 board). The standby voltage generation scheme available in the document is used in many other models of Power Man power supplies (for many 350W and 550W power supplies, the differences are only in the ratings of the elements).

JNC Computer Co. LTD LC-B250ATX

JNC Computer Co. Ltd. SY-300ATX Power Supply Diagram

Presumably manufacturer JNC Computer Co. Ltd. Power supply SY-300ATX. The scheme is drawn by hand, comments and recommendations for improvement.

Power Supply Schematics Key Mouse Electroniks Co Ltd model PM-230W

Power Supply Circuits L&C Technology Co. model LC-A250ATX

Scheme of power supplies LiteOn PE-5161-1 135W.

Scheme of power supplies LiteOn PA-1201-1 200W ( full set documentation for the PSU)

Scheme of LiteOn PS-5281-7VW 280W power supplies (full set of PSU documentation)

Scheme of LiteOn PS-5281-7VR1 280W power supplies (full set of PSU documentation)

Scheme of LiteOn PS-5281-7VR 280W power supplies (full set of PSU documentation)

LWT2005 power supply circuits on the KA7500B and LM339N chip

PSU diagram M-tech KOB AP4450XA.

PSU diagram MACRON Power Co. ATX 9912 model (aka DTK Computer model PTP-2007)

Schematic PSU Maxpower PX-300W

Schematic PSU Maxpower PC ATX SMPS PX-230W ver.2.03

PowerLink power supply circuits model LP-J2-18 300W.

Power Master power supply circuits model LP-8 ver 2.03 230W (AP-5-E v1.1).

Power Master power supply circuits model FA-5-2 ver 3.2 250W.

Schematic PSU Microlab 350W

Schematic PSU Microlab 400W

Schematic PSU Powerlink LPJ2-18 300W

Powerlink LPK, LPQ PSU Schematic

Schematic PSU Power Efficiency Electronic Co LTD model PE-050187

Schematic PSU Rolsen ATX-230

PSU diagram SevenTeam ST-200HRK

Schematic PSU SevenTeam ST-230WHF 230Watt

Schematic PSU SevenTeam ATX2 V2

PSU diagram SIRTEC INTERNATIONAL CO. Ltd. HPC-360-302 DF REV:C0 archived document in .PDF format

Sirtec HighPower HPC-420-302 420W power supply circuit diagram

Schematic PSU Sirtec HighPower HP-500-G14C 500W

PSU diagram SIRTEC INTERNATIONAL CO. Ltd. NO-672S. 850W. Power supplies of the Sirtec HighPower RockSolid line were sold under the CHIEFTEC CFT-850G-DF brand.

SHIDO power supply circuits model LP-6100 250W.

Scheme of PSU SUNNY TECHNOLOGIES CO. LTD ATX-230

Utiek ATX12V-13 600T power supply circuit diagram

Scheme of the power supply unit Wintech PC ATX SMPS model Win-235PE ver.2.03

Schemes of power supplies for laptops.

Scheme of a universal power supply 70W for laptops 12-24V, model SCAC2004, EWAD70W board on the LD7552 chip.

Schematic diagram of a power supply unit 60W 19V 3.42A for laptops, KM60-8M board on a UC3843 chip.

Delta ADP-36EH power supply circuit for 12V 3A laptops based on the DAP6A and DAS001 chip.

Li Shin LSE0202A2090 90W power supply circuit for laptops 20V 4.5A on the NCP1203 and TSM101 chip, AKKM on the L6561.

Diagram of a power supply unit ADP-30JH 30W for laptops 19V 1.58A on a DAP018B and TL431 chip.

Diagram of the Delta ADP-40PH ABW power supply

And the compatibility of the power supply with the UPS (uninterruptible power supply).
The ATX form factor standard defines the size, design, and other characteristics of a power supply, as well as voltage tolerances under load. We will consider this standard.
On this moment There are such versions of the ATX standard:

1. ATX 1.3
2. ATX2.0
3. ATX 2.2
4. ATX 2.3

The main differences between the versions of the ATX standards are the introduction of newer connectors and new power lines. In the first series, the +5 V line was mainly used, and in the second, +12 V.

Details about ATX power supply versions

One of the main developers of the ATX form factor is the company. All documentation is located on the official website www.formfactors.org, they describe the requirements for manufacturers of motherboards, power supplies and cases. Requirements and recommendations for power supplies are regulated by a document called ATX12V Power Supply Design Guide (PSDG).

The ATX12V standard was released as part of the transition to the new NetBurst architecture. The main innovation in ATX12V, compared to ATX 1.3, was the change in power supply from +12V, and not from +5V, and the addition of a new 4-pin +12V power connector (there should be no connector if the maximum possible +12V current is less than 10A).

ATX Versions 1.1 , was introduced in August 2000. There is no mention of versions 1.0, 1.2 on the official website, but information about them can be found on other resources.

ATX version 1.3 released in April 2003. Compared to the previous version 1.1, new current requirements were introduced, the -5V voltage was removed, PS_ON# signal processing requirements were added, and a mention of the power cable for .

ATX version 2.0 , compared to the version ATX 1.3 has been significantly changed. First of all, in terms of currents, the power consumption was increased by + 12V and reduced by + 3.3 and + 5V. Standardization of power supplies 350W and 400W was introduced (if above 300W, then 16 AWG wire is recommended). The ATX power cable was replaced with a 24-pin instead of 20-pin, and +3.3, +5, +12V, COM (“ground”), power for devices and a power cable for .
The 24-pin ATX connector is fully compatible with the 20-pin ATX, both mechanically and electrically.

In versions ATX 2.01 and ATX 2.2, the standardization of the 450W power supply was introduced; simplified requirements for currents along the +3.3V, +5V, +12V lines; increased efficiency requirements for +5V stand by.

The most important consumers of electricity are processors and video cards, the power of which passes through the +12 V line. If you install a seemingly ordinary configuration of the processor and video card (for example: AMD Athlon 3000+ and GeForce 7600 GT), and provide them with power from the block with a power of 400 W, then we will “get a skew” of voltages. The +12 V power line will sag, and the +5 V line will outweigh. And as a result - an independent reboot of the computer (either at startup or under load), blue screens of death, shutting down the computer, etc. The problem is that the main line of old power supplies is +5 V, and the processor and video card need a +12 V line, which turned out to be completely overloaded.

Linear and switching power supplies

Let's start with the basics. The power supply in the computer performs three functions. First, alternating current from the household power supply must be converted to direct current. The second task of the PSU is to lower the voltage of 110-230 V, which is redundant for computer electronics, to the standard values ​​required by the power converters for individual PC components - 12 V, 5 V and 3.3 V (as well as negative voltages, which we will talk about a little later) . Finally, the PSU plays the role of a voltage stabilizer.

There are two main types of power supplies that perform these functions - linear and switching. The simplest linear PSU is based on a transformer, on which the voltage alternating current is reduced to the required value, and then the current is rectified by a diode bridge.

However, the PSU is also required to stabilize the output voltage, which is due to both the instability of the voltage 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 a linear power supply, the transformer is dimensioned to provide excess power. Then, at a high current in the load, the required voltage will be observed. However, the overvoltage that will occur without any means of compensation at low current in the payload is also unacceptable. Excessive voltage is eliminated by including a non-useful load in the circuit. In the simplest case, this is a resistor or transistor connected via a Zener diode. In a more advanced one, the transistor is controlled by a microcircuit with a comparator. Be that as it may, excess power is simply dissipated in the form of heat, which negatively affects the efficiency of the device.

In the switching power supply circuit, another variable appears, on which the output voltage depends, in addition to the two already available: the input voltage and the load resistance. In series with the load there is a key (which in the case of interest to us is a transistor), controlled by a microcontroller in pulse-width modulation (PWM) mode. The higher the duration of the open states of the transistor in relation to their period (this parameter is called the duty cycle, in Russian terminology the inverse value is used - the duty cycle), the higher the output voltage. Due to the presence of a key, a switching power supply is also called Switched-Mode Power Supply (SMPS).

No current flows through a closed transistor, and the resistance of an open transistor is ideally negligible. In reality, an open transistor has resistance and dissipates some of the power in the form of heat. Also, the transition between transistor states is not perfectly discrete. And yet, the efficiency of a pulsed current source can exceed 90%, while the efficiency of a linear PSU with a stabilizer reaches 50% at best.

Another advantage of switching power supplies is a radical reduction in the size and weight of the transformer compared to linear power supplies 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 circuit is placed not after, but before the transformer and, in addition to voltage stabilization, it is used to obtain high-frequency alternating current (for computer PSUs, this is from 30 to 100 kHz and higher, and as a rule - about 60 kHz). A transformer operating at a mains frequency of 50-60 Hz, for the power required by a standard computer, would be ten times more massive.

Linear PSUs today are used mainly in the case of low power devices, when the relatively complex electronics required for a switching power supply is a more sensitive cost item compared to a transformer. These are, for example, 9 V power supplies, which are used for guitar effects pedals, and once - for game consoles, etc. But chargers for smartphones are already completely pulsed - here the costs are justified. Due to the significantly lower amplitude of the voltage ripple at the output, linear power supplies are also used in areas where this quality is in demand.

⇡ The general scheme of the ATX standard power supply

The PSU of a desktop computer is a switching power supply, the input of which is supplied with the voltage of a household electrical network with parameters of 110/230 V, 50-60 Hz, and there are a number of lines at the output direct current, the main of which are rated 12, 5 and 3.3 V. In addition, the PSU provides the -12 V voltage, and sometime also the -5 V voltage required for the ISA bus. But the latter at some point was excluded from the ATX standard due to the termination of support for the ISA itself.

In the simplified diagram of a standard switching power supply presented above, four main stages can be distinguished. In the same order, we consider the components of power supplies in the reviews, namely:

1. EMI filter - electromagnetic interference (RFI filter);
2. primary circuit - input rectifier (rectifier), key transistors (switcher) that create high-frequency alternating current on the primary winding of the transformer;
3. main transformer;
4. secondary circuit - current rectifiers from the secondary winding of the transformer (rectifiers), smoothing filters at the output (filtering).

⇡ EMI filter

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

Differential noise is suppressed by a CX capacitor (large yellow film capacitor in the photo above) connected in parallel with the load. Sometimes a choke is additionally hung on each wire, which performs the same function (not in the diagram).

The common mode filter is formed by CY capacitors (blue teardrop-shaped ceramic capacitors in the photo), at a common point connecting the power lines to ground, and the so-called. Common mode choke (common-mode choke, LF1 in the diagram), the current in the two windings of which flows in the same direction, which creates resistance to common mode noise.

In cheap models, a minimum set of filter parts is installed; in more expensive, the described schemes form repeating (in whole or in part) links. In the past, it was not uncommon to see PSUs without an EMI filter at all. Now this is rather a curious exception, although when buying a very cheap PSU, you can still run into such a surprise. As a result, not only and not so much the computer itself will suffer, but other equipment included in the household network - pulsed power supplies are a powerful source of interference.

In the area of ​​\u200b\u200bthe filter of a good PSU, you can find several details that protect the device itself or its owner from damage. There is almost always a simple fuse for short circuit protection (F1 in the diagram). Note that when the fuse blows, the protected object is no longer the power supply. If a short circuit has occurred, then it means that the key transistors have already broken through, and it is important to at least prevent the ignition of the electrical wiring. If a fuse suddenly blows in the PSU, then it is most likely pointless to change it to a new one.

Separately, protection against short-term voltage surges using a varistor (MOV - Metal Oxide Varistor). But there are no means of protection against a prolonged increase in voltage in computer power supplies. This function is performed by external stabilizers with their own transformer inside.

The capacitor in the PFC circuit after the rectifier can retain a significant charge after being disconnected from the power supply. So that a careless person who puts his finger into the power connector is not shocked, a high-value discharge resistor (bleeder resistor) is installed between the wires. In a more sophisticated version - along with a control circuit that prevents the charge from leaking when the device is in operation.

By the way, the presence of a filter in the PC power supply (and it is also in the PSU of a monitor and almost any computer equipment) means that buying a separate " network filter” instead of a conventional extension cord, in general, to no avail. He has the same inside. The only condition in any case is normal three-pin wiring with grounding. Otherwise, the CY capacitors connected to ground will simply not be able to perform their function.

⇡ Input rectifier

After the filter, the alternating current is converted to direct current using a diode bridge - usually in the form of an assembly in a common housing. A separate radiator for cooling the bridge is strongly welcomed. A bridge assembled from four discrete diodes is an attribute of cheap power supplies. You can also ask what current the bridge is designed to determine if it matches the power of the PSU itself. Although this parameter, as a rule, there is a good margin.

⇡ Active PFC block

In an AC circuit with a linear load (such as an incandescent lamp or electric stove), the flowing current follows the same sinusoid as the voltage. But this is not the case with devices that have an input rectifier, such as switching power supplies. The power supply passes current in short pulses, approximately coinciding in time with the peaks of the voltage sine wave (i.e., the maximum instantaneous voltage), when the rectifier smoothing capacitor is recharged.

The distorted current signal is decomposed into several harmonic oscillations in total with a sinusoid of a given amplitude (an ideal signal that would occur with a linear load).

The power used to perform useful work (which, in fact, is the heating of PC components) is indicated in the characteristics of the PSU and is called active. The rest of the power generated by harmonic current oscillations is called reactive power. It does no useful work, but heats up wires and puts a strain on transformers and other power equipment.

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

A switching PSU has a rather low power factor initially - about 0.7. For a private consumer, reactive power is not a problem (fortunately, it is not taken into account by electricity meters), unless he uses a UPS. It just falls on the uninterruptible full power loads. On the scale of an office or a city network, the excess reactive power generated by switching power supplies already significantly reduces the quality of power supply and causes costs, so it is being actively combated.

In particular, the vast majority of computer PSUs are equipped with active power factor correction (Active PFC) circuits. The unit with active PFC is easily identified by the single large capacitor and inductor installed after the rectifier. In essence, Active PFC is another switching converter that maintains a constant charge of about 400 V on the capacitor. In this case, the current from the mains is consumed by short pulses, the width of which is chosen so that the signal is approximated by a sinusoid - which is required to simulate a linear load . To synchronize the current demand signal with the voltage sine wave, the PFC controller has special logic.

The active PFC circuit contains one or two key transistors and a powerful diode, which are placed on the same radiator with the key transistors of the main power supply converter. As a rule, the PWM controller of the main converter key and the Active PFC key are one chip (PWM/PFC Combo).

The power factor of switching power supplies with active PFC reaches 0.95 and higher. In addition, they have one additional advantage - they do not require a 110/230 V mains switch and a corresponding voltage doubler inside the PSU. Most PFC circuits digest voltages from 85 to 265 V. In addition, the PSU's sensitivity to short-term voltage dips is reduced.

By the way, in addition to active PFC correction, there is also a passive one, which involves installing a high inductance inductor in series with the load. Its effectiveness is low, and you are unlikely to find this in a modern PSU.

⇡ Main transducer

The general principle of operation for all pulsed power supplies of an isolated topology (with a transformer) is the same: the key transistor (or transistors) creates an alternating current on the primary winding of the transformer, and the PWM controller controls the duty cycle of their switching. Specific circuits, however, differ both in the number of key transistors and other elements, and in qualitative characteristics: efficiency, signal shape, interference, etc. But here too much depends on the specific implementation to be worth focusing on. For those interested, we present a set of diagrams and a table that will allow them to be identified in specific devices by the composition of parts.

In addition to the above topologies, in expensive PSUs there are resonant (resonant) versions of Half Bridge, which are easy to identify by an additional large inductor (or two) and a capacitor forming an oscillatory circuit.

⇡ Secondary circuit

The secondary circuit is everything that is after the secondary winding of the transformer. In most modern power supplies, the transformer has two windings: 12 V is removed from one of them, and 5 V is removed from the other. The current is first rectified using an assembly of two Schottky diodes - one or more per bus (on the most heavily loaded bus - 12 V - there are four assemblies in powerful power supplies). More efficient in terms of efficiency are synchronous rectifiers, which use field-effect transistors instead of diodes. But this is the prerogative of truly advanced and expensive PSUs that claim the 80 PLUS Platinum certificate.

The 3.3V rail is typically derived from the same winding as the 5V rail, only the voltage is stepped down with a saturable choke (Mag Amp). A special winding on a 3.3 V transformer is an exotic option. Of the negative voltages in the current ATX standard, only -12 V remains, which is removed from the secondary winding under the 12 V bus through separate low-current diodes.

PWM key control of the converter changes the voltage on the primary winding of the transformer, and therefore on all the secondary windings at once. At the same time, the current consumption by the computer is by no means evenly distributed between the PSU buses. In modern hardware, the most loaded bus is 12-V.

Separate voltage stabilization on different buses requires additional measures. The classic method involves the use of a group stabilization choke. Three main tires are passed through its windings, and as a result, if the current increases on one bus, then the voltage drops on the others. Suppose the current increased on the 12 V bus, and in order to prevent a voltage drop, the PWM controller reduced the duty cycle of the key transistors. As a result, the voltage on the 5 V bus could go beyond the permissible limits, but was suppressed by the group stabilization inductor.

The 3.3V rail voltage is additionally regulated by another saturable choke.

In a more advanced version, separate stabilization of the 5 and 12 V buses is provided due to saturable chokes, but now this design in expensive high-quality PSUs has given way to DC-DC converters. In the latter case, the transformer has a single secondary winding with a voltage of 12 V, and the voltages of 5 V and 3.3 V are obtained thanks to DC converters. This method is most favorable for voltage stability.

Output filter

The final stage on each bus is a filter that smooths out the voltage ripple caused by the key transistors. In addition, pulsations of the input rectifier, whose frequency is equal to twice the frequency of the mains, break through to the secondary circuit of the PSU to one degree or another.

The ripple filter includes a choke and large capacitors. High-quality power supplies are characterized by a capacitance of at least 2,000 microfarads, but manufacturers of cheap models have a reserve for savings when they install capacitors, for example, of half the value, which inevitably affects the ripple amplitude.

⇡ Standby power supply +5VSB

A description of the components of the power supply would be incomplete without mentioning the standby voltage of 5 V, which makes it possible to sleep the PC and ensures the operation of all devices that must be turned on all the time. "Duty room" is powered by a separate pulse converter with a low-power transformer. In some power supplies, there is also a third transformer used in the feedback circuit to isolate the PWM controller from the primary circuit of the main converter. In other cases, this function is performed by optocouplers (LED and phototransistor in one package).

⇡ Power supply testing methodology

One of the main parameters of the PSU is voltage stability, which is reflected in the so-called. cross-load characteristic. KNKH is a diagram in which the current or power on the 12 V bus is plotted on one axis, and the total current or power on the 3.3 and 5 V buses is plotted on the other. At the intersection points, for different values ​​of both variables, the voltage deviation from the nominal by one tire or another. Accordingly, we publish two different KNX - for the 12 V bus and for the 5 / 3.3 V bus.

The color of the dot means the deviation percentage:

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

To obtain CNC, a custom-made power supply test bench is used, which creates a load due to heat dissipation on powerful field-effect transistors.

Another equally important test is to determine the range of ripples at the PSU output. The ATX standard allows ripples within 120 mV for a 12 V bus and 50 mV for a 5 V bus. There are high-frequency ripples (at twice the frequency of the main converter key) and low-frequency ripples (at twice the mains frequency).

We measure this parameter using the Hantek DSO-6022BE USB oscilloscope at the maximum load on the power supply unit specified by the specifications. In the oscillogram below, the green graph corresponds to a 12 V bus, yellow - 5 V. It can be seen that the ripples are within normal limits, and even with a margin.

For comparison, here is a picture of ripples at the output of the PSU of an old computer. This block wasn't great initially, but clearly hasn't gotten any better over time. Judging by the range of low-frequency ripples (note that the voltage base division is increased to 50 mV to fit the oscillations on the screen), the smoothing capacitor at the input has already become unusable. High-frequency ripple on the 5 V bus is on the verge of an acceptable 50 mV.

The following test determines the efficiency of the unit at a load of 10 to 100% of the rated power (by comparing the output power with the input power measured with a household wattmeter). For comparison, the graph shows the criteria for different categories of 80 PLUS. However, it does not arouse much interest these days. The graph shows the results of the top Corsair PSU in comparison with the very cheap Antec, and the difference is not that very big.

A more pressing issue for the user is the noise from the built-in fan. It is impossible to directly measure it near the roaring power supply test stand, so we measure the speed of rotation of the impeller with a laser tachometer - also at power from 10 to 100%. In the graph below, you can see that at low load on this PSU, the 135mm fan maintains a low RPM and is hardly audible at all. At maximum load, the noise can already be distinguished, but the level is still quite acceptable.

Good laboratory block power is a rather expensive pleasure and not all radio amateurs can afford it.
Nevertheless, at home, you can assemble a power supply that is not bad in terms of characteristics, which will also cope well with providing power to various amateur radio designs, and can also serve as a charger for various batteries.
Radio amateurs assemble such power supplies, usually from, which are available everywhere and cheap.

In this article, little attention is paid to the conversion of the ATX itself, since it is usually not difficult to convert a computer PSU for a medium-skilled radio amateur into a laboratory one, or for some other purpose, but beginner radio amateurs have a lot of questions about this. Basically, what parts in the PSU need to be removed, which ones to leave, what to add in order to turn such a PSU into an adjustable one, and so on.

Here, especially for such radio amateurs, in this article I want to talk in detail about the conversion of ATX computer power supplies into regulated power supplies, which can be used both as a laboratory power supply and as a charger.

For rework, we need a working ATX power supply, which is made on the TL494 PWM controller or its analogues.
The power supply circuits on such controllers, in principle, do not differ much from each other and are all mostly similar. The power of the power supply should not be less than that which you plan to remove from the converted unit in the future.

let's consider typical scheme ATX power supply, 250 watts. For "Codegen" power supplies, the circuit is almost the same as this one.

The circuits of all such PSUs consist of a high-voltage and low-voltage part. On the image printed circuit board power supply unit (below) from the side of the tracks, the high-voltage part is separated from the low-voltage wide empty strip (without tracks), and is located on the right (it is smaller in size). We will not touch it, but we will work only with the low-voltage part.
This is my board, and using its example, I will show you an option for reworking the ATX PSU.

The low-voltage part of the circuit we are considering consists of a TL494 PWM controller, an operational amplifier circuit that controls the output voltages of the power supply, and if they do not match, it gives a signal to the 4th leg of the PWM controller to turn off the power supply.
Instead of an operational amplifier, transistors can be installed on the PSU board, which, in principle, perform the same function.
Next comes the rectifier part, which consists of various output voltages, 12 volts, +5 volts, -5 volts, +3.3 volts, of which only a +12 volt rectifier (yellow output wires) will be needed for our purposes.
The remaining rectifiers and their related parts will need to be removed, except for the "duty" rectifier, which we will need to power the PWM controller and cooler.
The duty rectifier provides two voltages. Usually this is 5 volts and the second voltage can be in the region of 10-20 volts (usually about 12).
We will use a second rectifier to power the PWM. A fan (cooler) is also connected to it.
If this output voltage is significantly higher than 12 volts, then the fan will need to be connected to this source through an additional resistor, as will be further in the considered circuits.
In the diagram below, I marked the high-voltage part with a green line, the "duty" rectifiers with a blue line, and everything else that needs to be removed is in red.

So, everything that is marked in red is soldered, and in our 12 volt rectifier we change the standard electrolytes (16 volts) to higher voltage ones that will correspond to the future output voltage of our PSU. It will also be necessary to solder in the circuit of the 12th leg of the PWM controller and the middle part of the winding of the matching transformer - resistor R25 and diode D73 (if they are in the circuit), and instead of them, solder the jumper into the board, which is drawn in the diagram with a blue line (you can simply close diode and resistor without soldering them). In some schemes, this circuit may not be.

Further, in the PWM harness on its first leg, we leave only one resistor that goes to the +12 volt rectifier.
On the second and third legs of the PWM, we leave only the Master RC chain (in the diagram R48 C28).
On the fourth leg of the PWM, we leave only one resistor (indicated as R49 on the diagram. Yes, in many circuits between the 4th leg and 13-14 legs of the PWM - there is usually an electrolytic capacitor, we don’t touch it (if any), since it is designed for a soft start of the power supply, it simply was not in my board, so I put it in.
Its capacitance in standard circuits is 1-10 microfarads.
Then we release the 13-14 legs from all connections, except for the connection with the capacitor, and also release the 15th and 16th PWM legs.

After all the operations performed, we should get the following.

Here's what it looks like on my board (below in the picture).
I rewound the group stabilization inductor here with a 1.3-1.6 mm wire in one layer on my native core. It fit somewhere around 20 turns, but you can not do this and leave the one that was. It also works well with him.
I also installed another load resistor on the board, which I have consists of two 1.2 kOhm 3W resistors connected in parallel, the total resistance turned out to be 560 Ohm.
The native load resistor is rated for 12 volts of output voltage and has a resistance of 270 ohms. My output voltage will be about 40 volts, so I put such a resistor.
It must be calculated (at the maximum output voltage of the PSU at Idling) for a load current of 50-60 mA. Since the operation of the power supply unit without any load is not desirable, therefore it is put into the circuit.

View of the board from the side of the details.

Now what will we need to add to the prepared board of our PSU in order to turn it into an adjustable power supply;

First of all, in order not to burn the power transistors, we will need to solve the problem of stabilizing the load current and protecting against short circuits.
On the forums for the alteration of such blocks, I met such an interesting thing - when experimenting with the current stabilization mode, on the forum pro-radio, forum member DWD Here is a quote, here it is in full:

"I once said that I could not get the UPS to work normally in current source mode with a low reference voltage at one of the inputs of the PWM controller error amplifier.
More than 50mV is normal, less is not. In principle, 50mV is a guaranteed result, but in principle, you can get 25mV if you try. Less than that didn't work. It does not work steadily and is excited or confused by interference. This is with a positive voltage signal from the current sensor.
But in the datasheet on the TL494 there is an option when a negative voltage is removed from the current sensor.
I redid the circuit for this option and got an excellent result.
Here is a snippet of the diagram.

Actually, everything is standard, except for two points.
Firstly, is the best stability when stabilizing the load current with a negative signal from the current sensor, is it an accident or a pattern?
The circuit works fine with a reference voltage of 5mV!
With a positive signal from the current sensor, stable operation is obtained only at higher reference voltages (at least 25mV).
With resistor values ​​of 10Ω and 10KΩ, the current stabilized at 1.5A up to a short circuit of the output.
I need more current, so I put a 30 ohm resistor. Stabilization turned out at the level of 12 ... 13A at a reference voltage of 15mV.
Secondly (and most interesting), I don’t have a current sensor, as such ...
Its role is played by a track fragment on the board 3 cm long and 1 cm wide. The track is covered with a thin layer of solder.
If this track is used as a sensor at a length of 2 cm, then the current stabilizes at a level of 12-13A, and if at a length of 2.5 cm, then at a level of 10A.

Since this result turned out to be better than the standard one, we will follow the same path.

To begin with, you will need to unsolder the middle terminal of the secondary winding of the transformer (flexible braid) from the negative wire, or better without soldering it (if the signet allows) - cut the printed track on the board that connects it to the negative wire.
Next, you will need to solder a current sensor (shunt) between the cut of the track, which will connect the middle output of the winding to the negative wire.

Shunts are best taken from faulty (if you can find) pointer ammeters (tseshek), or from Chinese pointer or digital devices. They look like this. A piece 1.5-2.0 cm long will be quite enough.

You can of course try to do the same as above. DWD, that is, if the path from the braid to the common wire is long enough, then try to use it as a current sensor, but I didn’t do it, I got a board of a different design, like this, where two wire jumpers that connected the output are indicated by a red arrow braids with a common wire, and printed tracks passed between them.

Therefore, after removing unnecessary parts from the board, I unsoldered these jumpers and soldered a current sensor from a faulty Chinese circuit in their place.
Then I soldered the rewound inductor in place, installed the electrolyte and the load resistor.
Here is a piece of the board I have, where I marked the installed current sensor (shunt) with a red arrow at the place of the wire jumper.

Then, with a separate wire, this shunt must be connected to the PWM. From the side of the braid - with the 15th PWM leg through a 10 Ohm resistor, and connect the 16th PWM leg to a common wire.
Using a 10 ohm resistor, it will be possible to select the maximum output current of our PSU. On the diagram DWD there is a 30 ohm resistor, but start with 10 ohms for now. Increasing the value of this resistor increases the maximum output current of the PSU.

As I said earlier, the output voltage of the power supply is about 40 volts. To do this, I rewound my transformer, but in principle you can not rewind, but increase the output voltage in another way, but for me this method turned out to be more convenient.
I’ll talk about all this a little later, but for now, let’s continue and start installing the necessary additional parts on the board so that we get a workable power supply or charger.

Let me remind you once again that if you did not have a capacitor on the board between the 4th and 13-14 PWM legs (as in my case), then it is advisable to add it to the circuit.
You will also need to install two variable resistors (3.3-47 kOhm) to adjust the output voltage (V) and current (I) and connect them to the circuit below. It is desirable to make connection wires as short as possible.
Below I have given only a part of the circuit that we need - it will be easier to understand such a circuit.
In the diagram, newly installed parts are marked in green.

Scheme of newly installed parts.

I will give a few explanations according to the scheme;
- The uppermost rectifier is the duty room.
- The values ​​​​of variable resistors are shown as 3.3 and 10 kOhm - they are the ones that were found.
- The value of the resistor R1 is 270 ohms - it is selected according to the required current limit. Start small and you may end up with a completely different value, for example 27 ohms;
- I did not mark capacitor C3 as newly installed parts in the expectation that it may be present on the board;
- The orange line indicates the elements that may have to be selected or added to the circuit in the process of setting up the PSU.

Next, we deal with the remaining 12-volt rectifier.
We check what maximum voltage our PSU is capable of delivering.
To do this, temporarily unsolder from the first leg of the PWM - a resistor that goes to the output of the rectifier (according to the diagram above by 24 kOhm), then you need to turn on the unit in the network, first connect it to the break of any network wire, as a fuse - an ordinary incandescent lamp 75-95 Tue The power supply in this case will give us the maximum voltage that it is capable of.

Before connecting the power supply to the network, make sure that the electrolytic capacitors in the output rectifier are replaced with higher voltage ones!

All further switching on of the PSU should be made only with an incandescent lamp, it will protect the PSU from emergencies in case of any errors. The lamp in this case will simply light up, and the power transistors will remain intact.

Next, we need to fix (limit) the maximum output voltage of our PSU.
To do this, a 24 kΩ resistor (according to the diagram above) from the first PWM leg, we temporarily change it to a trimmer, for example 100 kΩ, and set the maximum voltage we need for them. It is advisable to set it so that it is less than 10-15 percent of the maximum voltage that our PSU is capable of delivering. Then, in place of the tuning resistor, solder a constant.

If you plan to use this PSU as a charger, then you can leave the standard diode assembly used in this rectifier, since its reverse voltage is 40 volts and it is quite suitable for the charger.
Then the maximum output voltage of the future charger will need to be limited in the manner described above, in the region of 15-16 volts. For a 12-volt battery charger, this is quite enough and it is not necessary to increase this threshold.
If you plan to use your converted PSU as a regulated power supply, where the output voltage will be more than 20 volts, then this assembly is no longer suitable. It will need to be replaced with a higher voltage one with the appropriate load current.
I put two assemblies in parallel on my board at 16 amperes and 200 volts.
When designing a rectifier on such assemblies, the maximum output voltage of the future power supply can be from 16 to 30-32 volts. It all depends on the model of the power supply.
If, when checking the PSU for the maximum output voltage, the PSU produces a voltage less than planned, and someone will need more output voltage (40-50 volts for example), then instead of a diode assembly, you will need to assemble a diode bridge, unsolder the braid from its place and leave it hanging in the air, and connect the negative output of the diode bridge to the place of the soldered braid.

Scheme of a rectifier with a diode bridge.

With a diode bridge, the output voltage of the power supply will be twice as much.
Diodes KD213 (with any letter) are very good for a diode bridge, the output current with which can reach up to 10 amperes, KD2999A, B (up to 20 amperes) and KD2997A, B (up to 30 amperes). The last ones are the best.
They all look like this;

In this case, it will be necessary to consider mounting the diodes to the radiator and isolating them from each other.
But I went the other way - I just rewound the transformer and managed, as I said above. two diode assemblies in parallel, since space was provided for this on the board. For me, this path was easier.

It is not difficult to rewind the transformer and how to do it - we will consider below.

To begin with, we unsolder the transformer from the board and look at the board to which pins the 12-volt windings are soldered.

Basically there are two types. Such as in the photo.
Next, you will need to disassemble the transformer. Of course, it will be easier to cope with smaller ones, but larger ones also lend themselves.
To do this, you need to clean the core from visible residues of varnish (glue), take a small container, pour water into it, put the transformer there, put it on the stove, bring to a boil and "cook" our transformer for 20-30 minutes.

For smaller transformers, this is quite enough (less can be) and such a procedure will absolutely not damage the core and windings of the transformer.
Then, holding the transformer core with tweezers (you can directly in the container) - with a sharp knife we ​​try to disconnect the ferrite jumper from the W-shaped core.

This is done quite easily, as the varnish softens from such a procedure.
Then just as carefully, we try to free the frame from the W-shaped core. This is also pretty easy to do.

Then we wind the windings. First comes half of the primary winding, mostly about 20 turns. We wind it and remember the direction of winding. The second end of this winding may not be soldered from the place of its connection with the other half of the primary, if this does not interfere with further work with the transformer.

Then we wind all the secondary ones. Usually there are 4 turns at once of both halves of 12-volt windings, then 3 + 3 turns of 5-volt ones. We wind everything, solder it from the conclusions and wind a new winding.
The new winding will contain 10+10 turns. We wind it with a wire with a diameter of 1.2 - 1.5 mm, or with a set of thinner wires (easier to wind) of the appropriate section.
The beginning of the winding is soldered to one of the terminals to which the 12-volt winding was soldered, we wind 10 turns, the winding direction does not matter, we bring the tap to the "braid" and in the same direction as we started - we wind another 10 turns and the end solder to the remaining output.
Next, we isolate the secondary and wind on it, wound by us earlier, the second half of the primary, in the same direction as it was wound earlier.
We assemble the transformer, solder it into the board and check the operation of the PSU.

If any extraneous noise, squeaks, cods occur during the voltage adjustment process, then in order to get rid of them, you will need to pick up an RC chain circled in an orange ellipse below in the figure.

In some cases, you can completely remove the resistor and pick up a capacitor, and in some it is impossible without a resistor. It will be possible to try adding a capacitor, or the same RC circuit, between 3 and 15 PWM legs.
If this does not help, then you need to install additional capacitors (circled in orange), their ratings are approximately 0.01 microfarads. If this does not help much, then install an additional 4.7 kΩ resistor from the second leg of the PWM to the middle output of the voltage regulator (not shown in the diagram).

Then you will need to load the power supply output, for example, with a 60 watt car lamp, and try to regulate the current with the "I" resistor.
If the current adjustment limit is small, then you need to increase the value of the resistor that comes from the shunt (10 ohms) and try to adjust the current again.
You should not put a tuning resistor instead of this, change its value only by installing another resistor with a higher or lower rating.

It may happen that when the current increases, the incandescent lamp in the mains wire circuit lights up. Then you need to reduce the current, turn off the PSU and return the resistor value to the previous value.

Also, for voltage and current regulators, it is best to try to purchase SP5-35 regulators, which come with wire and hard leads.

This is an analogue of multi-turn resistors (only one and a half turns), the axis of which is combined with a smooth and coarse regulator. First "Smooth" is adjusted, then when it runs out of limit, "Rough" starts to be regulated.
Adjustment with such resistors is very convenient, fast and accurate, much better than with a multi-turn. But if you can’t get them, then get the usual multi-turn ones, for example;

Well, it seems that I told you everything that I planned to bring to the alteration of the computer power supply, and I hope that everything is clear and intelligible.

If someone has any questions about the design of the power supply, ask them on the forum.

Good luck with your design!

Updated on 03/11/2013 23:29

Hi all! Today we will talk about the ATX form factor power supply.

The choice of a power supply for a personal computer should be approached with special responsibility, since the stability and reliability of the entire computer as a whole largely depends on it. This article describes the design features of the PSU, characteristics... Read more...

The power supply is an integral part of every computer. The functioning of the entire personal computer (PC) depends on its normal operation. But at the same time, power supplies are rarely bought, because once purchased a good power supply can provide several generations of continuously evolving systems. Given all this, the choice of power supply must be approached very seriously.

The power supply generates voltages to power all functional blocks of the PC. It generates the main supply voltages for computer components: +12 V, +5 V and 3.3 V. The PSU also generates additional voltages: -12 V and -5 V, and in addition, it provides galvanic isolation from the 220 V network.

ATX PSU Internal Design

The figure (Fig. 1) shows the internal design and layout of the elements of a typical power supply unit with an active power factor corrector (AKKM) "GlacialPower GP-AL650AA". On the PSU board, the following elements are indicated by numbers:

1. current protection control module;
   
2. +12 V and +5 V output voltage filter inductor, which also performs the function of group stabilization;
3. Filter choke +3.3 V;
4. Radiator with rectifier diodes of output voltages;
5. Main Converter Transformer;
6. Main converter key control transformer;
7. Transformer that forms the standby voltage of the auxiliary converter;
8. Power factor correction controller (separate board);
9. Radiator with diodes and keys of the main converter;
10. Mains voltage filter;
11. Throttle KKM;
12. Mains voltage filter capacitor.

This design of ATX power supplies is the most common and is used in PSUs of various capacities.

PSU connector types ATX

On the rear wall of the PSU there is a connector for connecting a network cable and a network switch. In some models of power supplies, a mains switch is not installed. Sometimes, in older models, you can find a connector for connecting the monitor's network cable next to the network connector. In modern power supplies, on the rear wall, manufacturers can install the following connectors (Fig. 2):

• Mains voltage indicator;
• Fan control button;
• Button for manual switching of input voltage (110 V / 220 V);
• USB ports built into the PSU.
  

IN modern models rarely installed exhaust fan on the back wall. Now it is located at the top of the PSU. This allows you to install a large and quiet cooling element. On high-power power supplies, such as the Chieftec CFT-1000G-DF power supply, two fans are installed on the top and on the back cover (Fig. 3).

A harness with connectors for connecting the motherboard, hard drives, video card and other components of the system unit comes out of the front wall of the power supply.

In a modular type PSU, instead of a wiring harness on the front wall, there are connectors for connecting wires with different output connectors. This allows you to organize the supply wires in the system unit and connect only those that are necessary for this configuration (Fig. 9 and 10).

The pinout of the PSU output connectors connected to the motherboard and other devices is shown in the figure (Fig. 4).

It should be noted that the colors of the wires are unified, and each color corresponds to its own voltage:

• Black - common bus (Ground);
• Yellow - +12 V;
• Red - +5 V;
• Orange - +3.3 V.
  

The figure (Fig. 5) shows the output connectors of ATX power supplies.

Not shown in the figures (Fig. 4 and 5) are the auxiliary power connectors for video cards, their pinout and appearance similar to the pinout for additional processor power connectors.

Electrical parameters and characteristics of the PSU

Modern power supplies for PCs have a large number of electrical parameters, some of them are not marked in the "passport technical specifications", since they are considered not important for the user. The main parameters are indicated by the manufacturer on a sticker located on the side wall.

Power supply power

Power - This is one of the main parameters of the BP. It describes how much electrical energy can give the power supply to devices connected to it ( HDD, motherboard with processor, video card, etc.). To select a power supply, it would seem that it is enough to sum up the consumption of all components and choose a power supply with a small power margin.

But things are much more complicated. The power supply generates various voltages distributed over different power buses (12 V, 5 V, 3.3 V and others), each bus (line), voltage is designed for a certain power. One would think that these powers are fixed, and their sum is equal to the output power of the power supply itself. But in ATX power supplies, one transformer is installed to form all these voltages, so the power on the lines floats. When the load on one of the lines increases, the power on the other lines decreases and vice versa.

The manufacturer in the passport indicates the maximum power of each line, summing them up, you get more power than the power supply can actually provide. Thus, often, the manufacturer declares the rated power that the PSU is not able to provide, thereby misleading users. An underpowered PSU installed in the system unit causes “freezes”, arbitrary reboots, clicking and cracking of hard disk heads, and other incorrect operation of devices.

Permissible maximum line current

This is one of the most important parameters of the power supply, but users often do not pay due attention to this parameter when purchasing a PSU. But after all, when the line current is exceeded, the power supply turns off (protection is triggered). You will need to disconnect it from the 220 V network and wait about a minute. It must be taken into account that the most powerful consumers - the processor and the video card are powered by 12 V lines, so when buying a PSU, you need to pay attention to the current values ​​\u200b\u200bspecified for it. To reduce the current load on the power connectors, the 12 V line is divided into two parallel (sometimes more) and designated as + 12V1 and + 12V2. When counting, the currents on the parallel lines are summed up.

For high-quality PSUs, information on the maximum current loads along the lines is indicated on the side sticker in the form of a plate (Fig. 6).

If such information is not indicated, then one can doubt the quality of this PSU and the correspondence of the real and declared power.

Operating voltage range

This characteristic means the range of mains voltage at which the PSU will remain operational. Modern power supplies are available with AKKM (active power factor corrector), which allows you to use the input voltage range from 110 V to 230 V. But inexpensive power supplies are also available with a small operating voltage range from 220 V to 240 V (for example, FPS FPS400-60THN- P). As a result, such a power supply will turn off when the mains voltage drops, which is not uncommon for our power networks, or even will not start at all.

Internal resistance

Differential internal resistance (electrical impedance) characterizes the losses of the PSU during the flow of alternating current. To combat it, a low-pass filter is included in the power supply circuit. But you can significantly reduce the impedance only by installing high-capacity capacitors with low series resistance (ESR) and chokes wound with thick wire. It is quite difficult to implement this structurally and physically.

Output voltage ripple

The power supply of a personal computer is a converter that converts AC voltage to DC voltage. As a result of such transformations, ripples are present at the output of the power lines (a pulsed change in the voltage value). The problem with ripple is that, if not filtered enough, it can distort the performance of the entire system, lead to false switching of comparators and misinterpretation of input information. This, in turn, leads to errors in operation and disconnection of PC devices.

To combat ripples, LC filters are included in the circuit of the output voltage lines, which smooth out the ripples of the output voltages as much as possible (Fig. 8).

Voltage stability

During the operation of the PSU, its output voltages change. An increase in voltage causes an increase in quiescent currents, which in turn causes an increase in power dissipation and overheating of circuit elements connected to the PSU. A decrease in the output voltage leads to a deterioration in the operation of the circuits, and when it drops to a certain level, the PC elements stop working. Computer hard drives are especially sensitive to voltage drops.

Permissible voltage deviations of the output lines for the ATX standard should not exceed ± 5% of the nominal line voltage.

Efficiency

The power supply efficiency determines how much usable power the system unit will receive from the energy consumed by the power supply. Most modern power supplies have an efficiency of at least 80%. And power supplies equipped with PKKM (PPFC) and AKKM (APFC) significantly exceed this figure.

Power factor

This is a parameter that you should pay attention to when choosing a power supply, it directly affects the efficiency of the power supply. With a small coefficient power efficiency will also be small. Therefore, automatic power factor correctors (APFC) are built into the circuits of modern PSUs, which significantly improve the characteristics of the PSU.

The first step when choosing a power supply should be determined by its capacity. To determine the required power, it is enough to sum up the power of all components of the system unit. But sometimes individual video cards have special requirements for the amount of current on the +12 line. In, this must be considered when choosing. Usually, for an average system unit equipped with one video card, a power supply unit of 500-600 watts is enough.

When choosing a model and manufacturer, you should read the reviews and reviews on this PSU model. It is advisable to choose a power supply with an AKKM (APFC) circuit. In other words, you need to choose a power supply that is powerful, quiet, well-made and meets the declared characteristics. Saving a dozen or two dollars is not worth it. It must be remembered that the stability, durability and reliability of the entire computer as a whole largely depends on the operation of the power supply..

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