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All about power supplies on a PC. Modern ATX power supplies and their characteristics

Introduction

An integral part of every computer is the power supply. It is just as important as the rest of the computer. At the same time, purchasing a power supply is quite rare, because a good power supply can provide power to several generations of systems. Taking all this into account, the purchase of a power supply must be taken very seriously, since the fate of the computer is directly dependent on the performance of the power supply.

To implement galvanic isolation, it is enough to manufacture a transformer with the necessary windings. But powering a computer requires a lot of power, especially for modern PCs. To power the computer, a transformer would have to be made, which would not only be large in size, but also weigh a lot. However, as the frequency of the transformer supply current increases, to create the same magnetic flux, fewer turns and a smaller cross-section of the magnetic core are required. In power supplies built on the basis of a converter, the frequency of the transformer supply voltage is 1000 or more times higher. This allows you to create compact and lightweight power supplies.

The simplest pulse power supply

Let's look at the block diagram of a simple switching power supply, which underlies all switching power supplies.

Block diagram of a switching power supply.

The first block converts AC network voltage to DC. Such a converter consists of a diode bridge that rectifies alternating voltage and a capacitor that smoothes out the ripples of the rectified voltage. This box also contains additional elements: mains voltage filters from pulse generator ripples and thermistors to smooth out the current surge at the moment of switching on. However, these elements may be omitted in order to save on cost.

The next block is a pulse generator, which generates pulses at a certain frequency that power the primary winding of the transformer. The frequency of the generating pulses of different power supplies is different and lies in the range of 30 - 200 kHz. The transformer performs the main functions of the power supply: galvanic isolation from the network and reducing the voltage to the required values.

The alternating voltage received from the transformer is converted by the next block into direct voltage. The block consists of voltage rectifying diodes and a ripple filter. In this block, the ripple filter is much more complex than in the first block and consists of a group of capacitors and a choke. In order to save money, manufacturers can install small capacitors, as well as chokes with low inductance.

The first switching power supply was a push-pull or single-cycle converter. Push-pull means that the generation process consists of two parts. In such a converter, two transistors open and close in turn. Accordingly, in a single-ended converter one transistor opens and closes. Circuits of push-pull and single-cycle converters are presented below.

Schematic diagram of the converter.

Let's take a closer look at the elements of the circuit:

    X2 - connector power supply circuit.

    X1 is the connector from which the output voltage is removed.

    R1 is a resistance that sets the initial small bias on the keys. It is necessary for a more stable start of the oscillation process in the converter.

    R2 is a resistance that limits the base current on the transistors; this is necessary to protect the transistors from burning out.

    TP1 - The transformer has three groups of windings. The first output winding generates the output voltage. The second winding serves as a load for the transistors. The third generates the control voltage for the transistors.

At the initial moment of turning on the first circuit, the transistor is slightly open, because A positive voltage is applied to the base through resistor R1. A current flows through the slightly open transistor, which also flows through winding II of the transformer. The current flowing through the winding creates a magnetic field. The magnetic field creates voltage in the remaining windings of the transformer. As a result, a positive voltage is created on winding III, which opens the transistor even more. The process continues until the transistor reaches saturation mode. The saturation mode is characterized by the fact that when the applied control current to the transistor increases, the output current remains unchanged.

Since the voltage in the windings is generated only in the event of a change in the magnetic field, its increase or decrease, the absence of an increase in the current at the output of the transistor will, therefore, lead to the disappearance of the emf in windings II and III. A voltage loss in winding III will lead to a decrease in the degree of opening of the transistor. And the output current of the transistor will decrease, therefore, the magnetic field will decrease. Decreasing the magnetic field will create a voltage of opposite polarity. The negative voltage in winding III will begin to close the transistor even more. The process will continue until the magnetic field completely disappears. When the magnetic field disappears, the negative voltage in winding III will also disappear. The process will begin to repeat itself again.

A push-pull converter works on the same principle, but the difference is that there are two transistors, and they open and close in turn. That is, when one is open, the other is closed. The push-pull converter circuit has the great advantage of using the entire hysteresis loop of the magnetic conductor of the transformer. Using only one section of the hysteresis loop or magnetizing in only one direction leads to many undesirable effects that reduce the efficiency of the converter and degrade its performance. Therefore, a push-pull converter circuit with a phase-shifting transformer is generally used everywhere. In circuits where simplicity, small dimensions, and low power are needed, a single-cycle circuit is still used.

ATX form factor power supplies without power factor correction

The converters discussed above, although complete devices, are inconvenient to use in practice. The converter frequency, output voltage and many other parameters “float”, changing depending on changes in: supply voltage, converter output load and temperature. But if the keys control a controller that could carry out stabilization and various additional functions, then you can use the circuit to power the devices. The power supply circuit using a PWM controller is quite simple, and, in general, is a pulse generator built on a PWM controller.

PWM - pulse width modulation. It allows you to adjust the amplitude of the signal passed through the LPF (low pass filter) by changing the duration or duty cycle of the pulse. The main advantages of PWM are the high efficiency of power amplifiers and great application possibilities.

Scheme of a simple power supply with a PWM controller.

This power supply circuit has a low power and uses a field-effect transistor as a key, which makes it possible to simplify the circuit and get rid of additional elements required to control transistor switches. In high-power power supplies, the PWM controller has control elements (“Driver”) for the output switch. IGBT transistors are used as output switches in high-power power supplies.

The mains voltage in this circuit is converted to DC voltage and supplied through a switch to the first winding of the transformer. The second winding serves to power the microcircuit and generate feedback voltage. The PWM controller generates pulses with a frequency that is set by an RC chain connected to pin 4. The pulses are fed to the input of the switch, which amplifies them. The duration of the pulses varies depending on the voltage on leg 2.

Let's consider a real ATX power supply circuit. It has many more elements and additional devices are present in it. The power supply circuit is conventionally divided into main parts by red squares.

ATX power supply circuit with a power of 150-300 W.

To power the controller chip, as well as generate the standby voltage +5, which is used by the computer when it is turned off, there is another converter in the circuit. In the diagram it is designated as block 2. As you can see, it is made according to the circuit of a single-cycle converter. The second block also contains additional elements. Basically, these are chains for absorbing voltage surges that are generated by the converter transformer. Microcircuit 7805 - a voltage stabilizer generates a standby voltage of +5V from the rectified voltage of the converter.

Often, low-quality or defective components are installed in the standby voltage generating unit, which causes the frequency of the converter to decrease to the audio range. As a result, a squeaking sound is heard from the power supply.

Since the power supply is powered from a 220V AC voltage network, and the converter needs DC voltage power, the voltage must be converted. The first block rectifies and filters alternating mains voltage. This block also contains a filter against interference generated by the power supply itself.

The third block is the TL494 PWM controller. It carries out all the main functions of the power supply. Protects the power supply from short circuits, stabilizes output voltages and generates a PWM signal to control transistor switches that are loaded on the transformer.

The fourth block consists of two transformers and two groups of transistor switches. The first transformer generates the control voltage for the output transistors. Since the TL494 PWM controller generates a low power signal, the first group of transistors amplifies this signal and passes it to the first transformer. The second group of transistors, or output ones, are loaded onto the main transformer, which generates the main supply voltages. This more complex output switch control circuit was used due to the complexity of controlling bipolar transistors and protecting the PWM controller from high voltage.

The fifth block consists of Schottky diodes, which rectify the output voltage of the transformer, and a low-pass filter (LPF). The low-pass filter consists of electrolytic capacitors of significant capacity and chokes. At the output of the low-pass filter there are resistors that load it. These resistors are necessary to ensure that the power supply capacity does not remain charged after turning off. There are also resistors at the output of the mains voltage rectifier.

The remaining elements not circled in the block are chains that form “service signals”. These chains protect the power supply from short circuits or monitor the health of the output voltages.

ATX power supply 200 W.

Now let's see how the elements are located on the printed circuit board of a 200 W power supply. The picture shows:

    Capacitors that filter output voltages.

    Place of unsoldered output voltage filter capacitors.

    Inductors that filter the output voltages. The larger coil not only plays the role of a filter, but also acts as a ferromagnetic stabilizer. This allows you to slightly reduce voltage imbalances when the load of different output voltages is uneven.

    WT7520 PWM stabilizer chip.

    A radiator on which Schottky diodes are installed for voltages +3.3V and +5V, and for voltage +12V there are ordinary diodes. It should be noted that often, especially in older power supplies, additional elements are placed on the same radiator. These are voltage stabilization elements +5V and +3.3V. In modern power supplies, only Schottky diodes for all main voltages or field-effect transistors, which are used as a rectifying element, are placed on this radiator.

    The main transformer, which generates all voltages, as well as galvanic isolation from the network.

    A transformer that generates control voltages for the output transistors of the converter.

    Converter transformer generating standby voltage +5V.

    The radiator on which the output transistors of the converter are located, as well as the transistor of the converter that generates the standby voltage.

    Mains voltage filter capacitors. There don't have to be two of them. To form a bipolar voltage and form a midpoint, two capacitors of equal capacity are installed. They divide the rectified mains voltage in half, thereby forming two voltages of different polarities, connected at a common point. In single-supply circuits there is only one capacitor.

    Network filter elements against harmonics (interference) generated by the power supply.

    Diode bridge diodes that rectify AC mains voltage.

ATX power supply 350 W.

The 350 W power supply is designed equivalently. What immediately catches your eye is the large board size, larger radiators and larger converter transformer.

    Output voltage filter capacitors.

    A radiator that cools the diodes that rectify the output voltage.

    PWM controller AT2005 (analogous to WT7520), which stabilizes voltages.

    The main transformer of the converter.

    A transformer that generates control voltage for output transistors.

    Standby voltage converter transformer.

    A radiator that cools the output transistors of the converters.

    Mains voltage filter against power supply interference.

    Diode bridge diodes.

    Mains voltage filter capacitors.

The considered circuit has been used in power supplies for a long time and is now sometimes found.

ATX format power supplies with power factor correction.

In the considered circuits, the network load is a capacitor connected to the network through a diode bridge. The capacitor is charged only if the voltage across it is less than the mains voltage. As a result, the current is pulsed in nature, which has many disadvantages.

Bridge voltage rectifier.

We list these disadvantages:

  • currents introduce higher harmonics (interference) into the network;
  • large amplitude of current consumption;
  • significant reactive component in the consumption current;
  • mains voltage is not used during the entire period;
  • The efficiency of such circuits is of little importance.

The new power supplies have an improved modern circuit; it now has one more additional unit - a power factor corrector (PFC). It improves the power factor. Or, in simpler terms, it eliminates some of the disadvantages of a bridge rectifier for mains voltage.

Full power formula.

Power factor (PF) characterizes how much of the total power there is an active component and how much is reactive. In principle, one can say, why take into account reactive power, it is imaginary and has no benefit.

Power factor formula.

Let's say we have a certain device, a power supply, with a power factor of 0.7 and a power of 300 W. It can be seen from the calculations that our power supply has a total power (the sum of reactive and active power) greater than that indicated on it. And this power should be provided by a 220V power supply. Although this power is not useful (even the electricity meter does not record it), it still exists.

Calculation of the total power of the power supply.

That is, internal elements and network cables must be designed for a power of 430 W, not 300 W. Imagine a case where the power factor is 0.1... Because of this, GORSET prohibits the use of devices with a power factor of less than 0.6, and if such are detected, a fine is imposed on the owner.

Accordingly, the campaigns developed new power supply circuits that had PFC. Initially, a high-inductance inductor connected at the input was used as a PFC; such a power supply is called a power supply with PFC or passive PFC. Such a power supply has an increased KM. To achieve the desired CM, it is necessary to equip power supplies with a large choke, since the input resistance of the power supply is capacitive in nature due to the capacitors installed at the output of the rectifier. Installing a choke significantly increases the mass of the power supply, and increases the KM to 0.85, which is not so much.

400 W power supply with passive power factor correction.

The figure shows an FSP 400 W power supply with passive power factor correction. It contains the following elements:

    Rectified mains voltage filter capacitors.

    Throttle performing power factor correction.

    Main converter transformer.

    Transformer that controls the keys.

    Auxiliary converter transformer (standby voltage).

    Mains voltage filters against power supply ripples.

    A radiator on which the output transistor switches are installed.

    A radiator on which diodes are installed that rectify the alternating voltage of the main transformer.

    Fan speed control board.

    A board on which the FSP3528 PWM controller is installed (analogous to KA3511).

    Group stabilization choke and output voltage ripple filter elements.

  1. Output voltage ripple filter capacitors.

Turning on the throttle to correct the CM.

Due to the low efficiency of the passive PFC, a new PFC circuit was introduced into the power supply, which is built on the basis of a PWM stabilizer loaded onto an inductor. This circuit brings many advantages to the power supply:

  • extended operating voltage range;
  • it became possible to significantly reduce the capacitance of the mains voltage filter capacitor;
  • significantly increased CM;
  • reducing the weight of the power supply;
  • increasing the efficiency of the power supply.

There are also disadvantages to this scheme - a decrease in the reliability of the power supply and incorrect operation with some uninterruptible power supplies when switching battery / mains operating modes. The incorrect operation of this circuit with a UPS is caused by the fact that the mains voltage filter capacitance in the circuit has significantly decreased. At the moment when the voltage disappears for a short time, the PFC current, which is necessary to maintain the voltage at the PFC output, increases greatly, as a result of which the protection against short circuit (short circuit) in the UPS is triggered.

Active power factor correction circuit.

If you look at the circuit, it is a pulse generator, which is loaded onto the inductor. The mains voltage is rectified by a diode bridge and supplied to the switch, which is loaded by inductor L1 and transformer T1. A transformer is introduced to provide feedback from the controller to the key. The voltage from the inductor is removed using diodes D1 and D2. Moreover, the voltage is removed alternately using diodes, either from the diode bridge or from the inductor, and charges the capacitors Cs1 and Cs2. Key Q1 opens and the required amount of energy is accumulated in throttle L1. The amount of accumulated energy is regulated by the duration of the open state of the key. The more energy accumulated, the more voltage the inductor will produce. After the key is turned off, the accumulated energy is released by the inductor L1 through the diode D1 to the capacitors.

This operation makes it possible to use the entire sinusoid of the alternating voltage of the network, in contrast to circuits without PFC, and also to stabilize the voltage supplying the converter.

In modern power supply circuits, dual-channel PWM controllers are often used. One microcircuit operates both the converter and the PFC. As a result, the number of elements in the power supply circuit is significantly reduced.

Scheme of a simple power supply on a two-channel PWM controller.

Let's consider the circuit of a simple 12V power supply using a two-channel PWM controller ML4819. One part of the power supply generates a constant stabilized voltage of +380V. The other part is a converter that generates a constant stabilized voltage of +12V. The PFC consists, as in the case considered above, of switch Q1, inductor L1 of feedback transformer T1 loaded on it. Diodes D5, D6 charge capacitors C2, C3, C4. The converter consists of two switches Q2 and Q3, loaded onto transformer T3. The pulse voltage is rectified by diode assembly D13 and filtered by inductor L2 and capacitors C16, C18. Using cartridge U2, the output voltage control voltage is generated.

GlacialPower GP-AL650AA power supply.

Let's consider the design of a power supply that has an active PFC:

  1. Current protection control board;
  2. A choke that performs the role of both a voltage filter +12V and +5V, and a group stabilization function;
  3. Voltage filter choke +3.3V;
  4. A radiator on which rectifier diodes of output voltages are located;
  5. Main converter transformer;
  6. Transformer that controls the keys of the main converter;
  7. Auxiliary converter transformer (forming standby voltage);
  8. Power factor correction controller board;
  9. Radiator, cooling diode bridge and main converter switches;
  10. Line voltage filters against interference;
  11. Power factor corrector choke;
  12. Mains voltage filter capacitor.

Design features and types of connectors

Let's look at the types of connectors that may be present on the power supply. On the back wall of the power supply there is a connector for connecting the network cable and a switch. Previously, next to the power cord connector, there was also a connector for connecting the monitor's network cable. Optionally, other elements may be present:

  • indicators of mains voltage or power supply operating status;
  • fan operating mode control buttons;
  • button for switching input mains voltage 110/220V;
  • USB ports built into the USB hub power supply;
  • other.

Fans that suck air from the power supply are increasingly placed on the rear wall. Increasingly, the fan is placed at the top of the power supply due to the larger space for installing the fan, which allows you to install a large and quiet active cooling element. Some power supplies even have two fans installed, both on top and on the back.

Chieftec CFT-1000G-DF power supply.

A wire with a power connector for the motherboard comes out of the front wall. In some modular power supplies, it, like other wires, is connected through a connector. The figure below shows the pinout of all main connectors.

You can notice that each voltage has its own wire color:

  • Yellow color - +12 V,
  • Red color - +5 V,
  • Orange color - +3.3V,
  • Black color is common or earth.

For other voltages, wire colors may vary from manufacturer to manufacturer.

The figure does not show additional power connectors for video cards, since they are similar to the additional power connectors for the processor. There are also other types of connectors that are found in branded computers from DelL, Apple and others.

Electrical parameters and characteristics of power supplies

The power supply has many electrical parameters, most of which are not noted in the data sheet. On the side sticker of the power supply, only a few basic parameters are usually marked - operating voltages and power.

Power supply power

Power is often indicated on the label in large font. The power of the power supply characterizes how much electrical energy it can supply to the devices connected to it (motherboard, video card, hard drive, etc.).

In theory, it is enough to sum up the consumption of the components used and select a power supply with a little more power for reserve. To calculate the power, you can use, for example, the site http://extreme.outervision.com/PSUEngine, the recommendations specified in the passport of the video card, if there is one, the thermal package of the processor, etc. are also quite suitable.

But in reality, everything is much more complicated, because... The power supply produces different voltages - 12V, 5V, -12V, 3.3V, etc. Each voltage line is designed for its own power. It was logical to think that this power is fixed, and their sum is equal to the power of the power supply. But the power supply contains one transformer to generate all these voltages used by the computer (except for the standby voltage +5V). True, it is rare, but you can still find a power supply with two separate transformers, but such power supplies are expensive and are most often used in servers. Conventional ATX power supplies have one transformer. Because of this, the power of each voltage line can float: it increases if other lines are lightly loaded, and decreases if other lines are heavily loaded. Therefore, the maximum power of each line is often written on power supplies, and as a result, if they are summed up, the output will be even greater than the actual power of the power supply. Thus, the manufacturer can confuse the consumer, for example, by declaring too high a rated power that the power supply is not capable of providing.

Note that if a power supply of insufficient power is installed in the computer, this will cause abnormal operation of the devices (“freezes”, reboots, clicking of the hard disk heads), up to the impossibility of turning on the computer. And if the PC has a motherboard installed that is not designed for the power of the components that are installed on it, then often the motherboard functions normally, but over time the power connectors burn out due to their constant heating and oxidation.

Burnt connectors.

Permissible maximum line current

Although this is one of the important parameters of the power supply, the user often does not pay attention to it when purchasing. But if the permissible current on the line is exceeded, the power supply turns off, because protection is triggered. To turn it off, you need to turn off the power supply and wait a while, about a minute. It is worth considering that now all the most power-hungry components (processor, video card) are powered from the +12V line, so more attention must be paid to the values ​​​​of the currents indicated for it. For high-quality power supplies, this information is usually presented in the form of a plate (for example, Seasonic M12D-850) or a list (for example, FSP ATX-400PNF) on a side sticker.

Power supplies that do not include such information (for example, Gembird PSU7 550W) immediately raise doubts about the quality of performance and the compliance of the declared power with the real one.

The remaining parameters of power supplies are not regulated, but are no less important. It is possible to determine these parameters only by conducting various tests with the power supply.

Operating voltage range

The operating voltage range refers to the range of mains voltage values ​​at which the power supply retains its functionality and the values ​​of its rating parameters. Nowadays, power supplies with PFC (active power factor correction) are increasingly being produced, which allows expanding the operating voltage range from 110 to 230. There are also power supplies with a small operating voltage range, for example, the FPS FPS400-60THN-P power supply has a range from 220 up to 240. As a result, this power supply, even when paired with a massive uninterruptible power supply, will turn off when the network voltage drops. This is because a conventional UPS stabilizes the output voltage in the range of 220 V +/- 5%. That is, the minimum voltage for switching to the battery will be 209 (and if we take into account the slowness of the relay switching, the voltage may be even lower), which is lower than the operating voltage of the power supply.

Internal resistance

Internal resistance characterizes the internal losses of the power supply when current flows. Internal resistance by type can be divided into two types: conventional for direct current and differential for alternating current.

Equivalent equivalent circuit of the power supply.

The DC resistance consists of the resistances of the components from which the power supply is built: the resistance of the wires, the resistance of the transformer windings, the resistance of the inductor wires, the resistance of the printed circuit board tracks, etc. Due to the presence of this resistance, as the load on the power supply increases, the voltage drops. This resistance can be seen by plotting the cross-load characteristic of the power supply. To reduce this resistance, various stabilization circuits operate in power supplies.

Cross-load characteristics of the power supply.

Differential resistance characterizes the internal losses of the power supply when alternating current flows. This resistance is also called electrical impedance. Reducing this resistance is the most difficult. To reduce it, a low-pass filter is used in the power supply. To reduce the impedance, it is not enough to install high-capacity capacitors and high-inductance coils into the power supply. It is also necessary that the capacitors have low series resistance (ESR), and the chokes are made of thick wire. It is physically very difficult to implement this.

Output voltage ripple

The power supply is a converter that repeatedly converts the voltage from AC to DC. As a result, there are ripples at the output of its lines. Ripple is a sudden change in voltage over a short period of time. The main problem with ripple is that if a circuit or device does not have a filter in the power supply circuit or it is bad, then these ripples pass throughout the entire circuit, distorting its performance characteristics. This can be seen, for example, if you turn the speaker volume to maximum while there are no signals at the output of the sound card. Various noises will be heard. This is ripple, but it is not necessarily the noise of the power supply. But if in the operation of a conventional amplifier there is no great harm from ripples, only the noise level increases, then, for example, in digital circuits and comparators they can lead to false switching or incorrect perception of input information, which leads to errors or inoperability of the device.

Output voltage waveform of the Antec Signature SG-850 power supply.

Voltage stability

Next, we will consider such a characteristic as the stability of the voltages supplied by the power supply. During operation, no matter how ideal the power supply is, its voltages change. An increase in voltage causes, first of all, an increase in the quiescent currents of all circuits, as well as a change in the parameters of the circuits. So, for example, for a power amplifier, increasing the voltage increases its output power. Some electronic parts may not be able to withstand the increased power and may burn out. This same increase in power leads to an increase in the power dissipated by electronic elements, and, consequently, to an increase in the temperature of these elements. Which leads to overheating and/or changes in performance.

Reducing the voltage, on the contrary, reduces the quiescent current, and also worsens the characteristics of the circuits, for example, the amplitude of the output signal. When it drops below a certain level, certain circuits stop working. The electronics of hard drives are especially sensitive to this.

Permissible voltage deviations on the lines of the power supply are described in the ATX standard and on average should not exceed ±5% of the line rating.

To comprehensively display the magnitude of voltage drop, a cross-load characteristic is used. It is a color display of the level of voltage deviation of the selected line when two lines are loaded: the selected one and +12V.

Efficiency

Let's now move on to the coefficient of performance, or efficiency for short. Many people remember from school - this is the ratio of useful work to expended work. Efficiency shows how much of the consumed energy is converted into useful energy. The higher the efficiency, the less you have to pay for the electricity consumed by the computer. Most high-quality power supplies have a similar efficiency; it varies in the range of no more than 10%, but the efficiency of power supplies with PPFC and APFC is significantly higher.

Power factor

As a parameter that you should pay attention to when choosing a power supply, the power factor is less significant, but other values ​​depend on it. If the power factor is low, the efficiency will be low. As noted above, power factor correctors bring many improvements. A higher power factor will lead to lower currents in the network.

Non-electrical parameters and characteristics of power supplies

Usually, as for electrical characteristics, not all non-electrical parameters are indicated in the passport. Although the non-electrical parameters of the power supply are also important. We list the main ones:

  • Operating temperature range;
  • reliability of the power supply (time between failures);
  • noise level created by the power supply during operation;
  • power supply fan speed;
  • power supply weight;
  • length of power cables;
  • ease of use;
  • environmental friendliness of the power supply;
  • compliance with state and international standards;
  • Dimensions of the power supply.

Most non-electrical parameters are clear to all users. However, let’s focus on more relevant parameters. Most modern power supplies are quiet, with a noise level of about 16 dB. Although, even in a power supply with a rated noise level of 16 dB, a fan with a rotation speed of 2000 rpm can be installed. In this case, when the power supply load is about 80%, the fan speed control circuit will turn it on at maximum speed, which will lead to significant noise, sometimes more than 30 dB.

It is also necessary to pay attention to the convenience and ergonomics of the power supply. Using a modular connection of power cables has many advantages. This also makes it more convenient to connect devices, less occupied space in the computer case, which in turn is not only convenient, but improves the cooling of computer components.

Standards and certificates

When purchasing a power supply, first of all you need to look at the availability of certificates and its compliance with modern international standards. The following standards can most often be found on power supplies:

    RoHS, WEEE - does not contain harmful substances;

    UL, cUL - certificate for compliance with its technical characteristics, as well as safety requirements for built-in electrical appliances;

    CE - a certificate that shows that the power supply meets the strictest requirements of the European Committee directives;

    ISO - international quality certificate;

    CB - international certificate of compliance with its technical characteristics;

    FCC - compliance with standards for electromagnetic interference (EMI) and radio frequency interference (RFI) generated by the power supply;

    TUV - certificate of compliance with the requirements of the international standard EN ISO 9001:2000;

    CCC - China's certificate of compliance with safety, electromagnetic parameters and environmental protection.

There are also computer standards of the ATX form factor, which define the dimensions, design and many other parameters of the power supply, including permissible voltage deviations under load. Today there are several versions of the ATX standard:

  • ATX 1.3 Standard;
  • ATX 2.0 Standard;
  • ATX 2.2 Standard;
  • ATX 2.3 Standard.

The difference between the versions of ATX standards mainly concerns the introduction of new connectors and new requirements for the power supply lines of the power supply.

When it becomes necessary to purchase a new ATX power supply, you first need to determine the power that is needed to power the computer in which this power supply will be installed. To determine it, it is enough to sum up the power of the components used in the system, for example, using a calculator from outervision.com. If this is not possible, then we can proceed from the rule that for an average computer with one gaming video card, a power supply with a power of 500-600 watts is sufficient.

Considering that most parameters of a power supply can only be found out by testing it, the next step is to strongly recommend that you familiarize yourself with tests and reviews of possible contenders - power supply models that are available in your region and satisfy your needs at least in terms of power provided. If this is not possible, then you need to choose according to the power supply’s compliance with modern standards (the higher the number, the better), and it is desirable to have an APFC circuit in the power supply. When purchasing a power supply, it is also important to turn it on, if possible right at the place of purchase or immediately upon arriving home, and monitor how it works so that the power source does not make squeaks, hums or other extraneous noise.

In general, you need to choose a power supply that is powerful, well made, has good declared and actual electrical parameters, and also turns out to be easy to use and quiet during operation, even under high load. And under no circumstances should you save a few dollars when purchasing a power supply. Remember that the stability, reliability and durability of the entire computer mainly depends on the operation of this device.

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The most common version of the power supply involves converting 220 Volts of alternating voltage (U) into a reduced direct voltage. In addition, power supplies can provide galvanic isolation between input and output circuits. In this case, the transformation ratio (the ratio of input and output voltages) can be equal to unity.

An example of such use would be to supply power to areas where there is a high degree of electrical hazard, such as bathrooms.

In addition, quite often household power supplies can be equipped with built-in additional devices: stabilizers, regulators. indicators, etc.

TYPES AND TYPES OF POWER UNITS

First of all, the classification of power supplies is carried out according to the principle of operation. There are two main options here:

  • transformer (linear);
  • pulse (inverter).

Transformer block consists of a step-down transformer and a rectifier that converts alternating current into direct current. Next, a filter (capacitor) is installed that smooths out ripples and other elements (output parameter stabilizer, short-circuit protection, high-frequency (RF) interference filter).

Advantages of a transformer power supply:

  • high reliability;
  • maintainability;
  • simplicity of design;
  • minimal or no interference;
  • low price.

Disadvantages - heavy weight, large dimensions and low efficiency.

Impulse power block- an inverter system in which alternating voltage is converted into direct voltage, after which high-frequency pulses are generated, which undergo a series of further transformations (). In a device with galvanic isolation, pulses are transmitted to a transformer, and in the absence of one, directly to the low-pass filter at the output of the device.

Thanks to the formation of RF signals, small-sized transformers are used in switching power supplies, which allows reducing the size and weight of the device. To stabilize the voltage, negative feedback is used, thanks to which a constant voltage level is maintained at the output, independent of the load.

Advantages of a switching power supply:

  • compactness;
  • light weight;
  • affordable price and high efficiency (up to 98%).

In addition, it should be noted that there are additional protections that ensure the safety of using the device. Such power supplies often provide protection against short circuits (short circuits) and failure when there is no load.

Disadvantages - the operation of a larger component of the circuit without galvanic isolation, which complicates repairs. In addition, the device is a source of high frequency interference and has a lower load limit. If the power of the latter is less than the permissible parameter, the unit will not start.

PARAMETERS AND CHARACTERISTICS OF THE POWER SUPPLY

When choosing a power supply, you should take into account a number of characteristics, including:

  • power;
  • output voltage and current;
  • as well as the availability of additional options and capabilities.

Power.

A parameter that is measured in W or V*A. When choosing a device, you should take into account the presence of inrush currents in many electrical receivers (pumps, irrigation systems, refrigerators, and others). At the moment of start-up, power consumption increases by 5-7 times.

As for other cases, the power supply is selected taking into account the total power of the powered devices with a recommended margin of 20-30%.

Input voltage.

In Russia this parameter is 220 Volts. If you use a power supply in Japan or the USA, you will need a device with an input voltage of 110 Volts. In addition, for inverter power supplies this value can be 12/24 Volts.

Output voltage.

When choosing a device, you should focus on the rated voltage of the consumer used (indicated on the device body). It could be 12 Volts, 15.6 Volts and so on. When choosing, you should buy a product that is as close as possible to the required parameter. For example, to power a 12.1 V device, a 12 V unit is suitable.

Output voltage type.

Most devices are powered by stabilized direct voltage, but there are also those that are suitable for unstabilized or alternating voltage. Taking this criterion into account, the design is also selected. If an unstabilized constant U at the input is enough for the consumer, a power supply with a stabilized voltage at the output is also suitable.

Output current.

This parameter may not be indicated, but if you know the power, it can be calculated. Power (P) is equal to voltage (U) times current (I). Therefore, to calculate the current, it is necessary to divide the power by the voltage. This parameter is useful for selecting a suitable power supply for a specific load.

As a rule, the operating current should exceed the maximum current consumption of the device by 10-20%.

Efficiency.

High power supply power is not a guarantee of good performance. An equally important parameter is efficiency, which reflects the efficiency of energy conversion and its transmission to the device. The higher the efficiency, the more efficiently the unit is used, and the less energy is spent on heating.

Overload protection.

Many sources are equipped with overload protection, which ensures that the power supply is turned off if the level of current consumed from the network is exceeded.

Deep discharge protection.

Its task is to break the power circuit when the battery is completely discharged (typical for uninterruptible power supplies). After power is restored, the device's functionality is restored.

In addition to the options listed above, the power supply may provide protection against short circuits, overheating, overcurrent, overvoltage and undervoltage.

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Efficiency (Efficiency, PSU Efficiency - eng.) is a parameter indicating how efficiently the power supply can convert energy to meet the needs of components. It is measured as a percentage and the more it approaches 100%, the higher the efficiency.

What is power supply efficiency .

The power supply is a pulse converter that pre-converts alternating current to direct current. The alternating current is filtered, passes through filters, and other converters. With this transformation, some energy is lost with electromagnetic harmonics, element resistance and, accordingly, with heat. If you compare the incoming power and the outgoing power, the output will always be less. Ratio incoming and outgoing energy is Efficiency.

Based on the level of efficiency, one can judge quality element base in the power supply, since to achieve high values, more expensive and high-quality components are used. Manufacturers BP, new technologies are used to increase the level Efficiency. For example, quadruple and double transformers, electronic current and protection control systems, and finally, high-quality soldering for lower resistance.

Advantages of a high level of efficiency .

1. High efficiency saves energy, which can best affect your electricity bills. In a single case, the savings are not big, but in the long run you will get good savings. Additionally, if your computer consumes a significant amount of power, you will benefit from high Efficiency will be higher.

In organizations where computers 50 and more, tall Efficiency will save a significant amount of money on electricity and help save on electrical equipment of the supply network, due to the lower required power.

2. High Efficiency, ultimately reduces the heating of components inside the power supply, due to lower current losses and, as a result, less conversion of electricity into thermal energy. This allows you to reduce the fan operating frequency and reduce noise. But the main thing is that under more favorable operating conditions, most components of the power supply serve much longer. In particular, this applies to power circuits and, which are not tolerant of constant overheating.

3. Higher quality components in the power supply with high Efficiency. For increase Efficiency, high-quality components and reliable soldering are used. This also increases the service life of the power supply and all its characteristics: ripple level, maintaining the required voltage, the ability to release energy, the influence of power lines on each other.

Standard 80 PLUS.What it is?

Power supplies that received 80 PLUS certificate, must provide an efficiency coefficient not lower than a certain level under load from 20 to 100%. Certificates vary in percentage and name, from worst to best - Plus,Bronze, Silver, Gold, Platinum and introduced not so long ago Titanium.

It is noteworthy that certification has different percentages for different voltages. Different percentages apply when working from 115 (America) and 230 volt (Europe).

The presence of any of these certificates indicates a fairly high-quality element base, and the higher the standard, the higher the quality of the power supply. For home use, it is enough to have a power supply with a standard Bronze or Silver. Next, percentage growth Efficiency grows much more slowly, in contrast to prices for such BP.

The power supply is the most important component of any personal computer, on which the reliability and stability of your build depends. There is quite a large selection of products on the market from various manufacturers. Each of them has two or three lines or more, which also include a dozen models, which seriously confuses buyers. Many people do not pay due attention to this issue, which is why they often overpay for excess power and unnecessary bells and whistles. In this article we will figure out which power supply is best for your PC?

A power supply (hereinafter referred to as PSU) is a device that converts high voltage 220 V from an outlet into computer-friendly values ​​and is equipped with the necessary set of connectors for connecting components. It seems to be nothing complicated, but upon opening the catalog, the buyer is faced with a huge number of different models with a bunch of often incomprehensible characteristics. Before we talk about choosing specific models, let’s look at what characteristics are key and what you should pay attention to first.

Main parameters.

1. Form factor. In order for the power supply to fit into your case, you must decide on the form factors, based on from the parameters of the system unit case itself. The dimensions of the power supply in terms of width, height and depth depend on the form factor. Most come in the ATX form factor, for standard cases. In small system units of the microATX, FlexATX, desktops and others, smaller units are installed, such as SFX, Flex-ATX and TFX.

The required form factor is specified in the characteristics of the case, and it is by this that you need to navigate when choosing a power supply.

2. Power. The power determines what components you can install in your computer, and in what quantity.
It is important to know! The number on the power supply is the total power across all of its voltage lines. Since the main consumers of electricity in a computer are the central processor and video card, the main power line is 12 V, when there are also 3.3 V and 5 V to power some components of the motherboard, components in expansion slots, power drives and USB ports. The power consumption of any computer along the 3.3 and 5 V lines is insignificant, so when choosing a power supply for power, you should always look at the "characteristic" power on line 12 V", which ideally should be as close as possible to the total power.

3. Connectors for connecting components, the number and set of which determine whether you can, for example, power a multiprocessor configuration, connect a couple or more video cards, install a dozen hard drives, and so on.
The main connectors, except ATX 24 pin, are:

To power the processor, these are 4 pin or 8 pin connectors (the latter can be detachable and have a 4+4 pin entry).

To power the video card - 6 pin or 8 pin connectors (8 pin is most often collapsible and is designated 6+2 pin).

For connecting 15-pin SATA drives

Additional:

4pin MOLEX type for connecting older HDDs with an IDE interface, similar disk drives and various optional components, such as rheobass, fans, etc.

4-pin Floppy - for connecting floppy drives. They are very rare these days, so such connectors most often come in the form of adapters with MOLEX.

Extra options

Additional characteristics are not as critical as the main ones in the question: “Will this power supply work with my PC?”, but they are also key when choosing, because affect the efficiency of the unit, its noise level and ease of connection.

1. Certificate 80 PLUS determines the efficiency of the power supply unit, its efficiency (efficiency factor). List of 80 PLUS certificates:

They can be divided into the basic 80 PLUS, on the far left (white), and the colored 80 PLUS, ranging from Bronze to the top Titanium.
What is efficiency? Let's say we are dealing with a unit whose efficiency is 80% at maximum load. This means that at maximum power the power supply will draw 20% more energy from the outlet, and all this energy will be converted into heat.
Remember one simple rule: the higher the 80 PLUS certificate in the hierarchy, the higher the efficiency, which means it will consume less unnecessary electricity, heat less, and, often, make less noise.
In order to achieve the best efficiency indicators and obtain the 80 PLUS “color” certificate, especially at the highest level, manufacturers use their entire arsenal of technologies, the most efficient circuitry and semiconductor components with the lowest possible losses. Therefore, the 80 PLUS icon on the case also speaks of the high reliability and durability of the power supply, as well as a serious approach to creating the product as a whole.

2. Type of cooling system. The low level of heat generation of power supplies with high efficiency allows the use of silent cooling systems. These are passive (where there is no fan at all), or semi-passive systems, in which the fan does not rotate at low powers, and starts working when the power supply becomes “hot” under load.

When selecting a power supply, you should pay attention to for the length of the cables, the main ATX24 pin and the CPU power cable when installed in a case with a bottom-mounted power supply.

For optimal installation of power wires behind the rear wall, they must be at least 60-65 cm long, depending on the size of the case. Be sure to take this point into account so you don’t have to bother with extension cords later.
You need to pay attention to the number of MOLEX only if you are looking for a replacement for your old and antediluvian system unit with IDE drives and drives, and even in significant quantities, because even the simplest power supplies have at least a couple of old MOLEX, and in more expensive models There are dozens of them in general.

I hope this small guide to the DNS company catalog will help you with such a complex issue at the initial stage of your acquaintance with power supplies. Enjoy the shopping!

Greetings, dear readers. I encountered the following problem: recently my computer began to slow down. And this coincided precisely with a decrease in voltage in the electrical network. I noticed this by the glow of the lighting lamps. So I immediately discarded all suspicions of viruses and other problems.

It’s just that my old power supply couldn’t cope; it didn’t have enough strength to pull the voltage to the required level. This is where the problems with the system came from. And in this article I will share with you some thoughts about power supplies in a computer.

It would seem like a small component of the system unit (it’s not a video card), why devote an entire article to it? It's simple: many people do not treat their PC's power source with due "respect", which leads to unpleasant consequences. Therefore, let's figure out why you need a power supply in a computer and how to choose it correctly.

What is a power supply and what is it used for?

The power supply (aka PSU) is the power source in the unit, which is responsible for providing energy to the remaining components. The durability and stability of the entire system largely depends on the power supply. In addition, a computer power supply prevents the loss of information from a personal computer, preventing energy surges.

I am sure that every person who is more or less familiar with technology knows that it works from an outlet. However, not every user is aware that system components cannot receive energy directly.
This is how we smoothly come to the most interesting thing: what is a power supply for in a PC? For two reasons:

  • Firstly, the current in the electrical network is alternating, which computers really don’t like. The power supply makes the current constant, correcting the situation;
  • Secondly, each component of a PC, and even a laptop, requires a different voltage. And again the power supply comes to the rescue, supplying the processor and video card with the necessary current.

Choosing a power supply for a computer

Of course, it’s much more interesting to choose an expensive video card or an external one for your “comrade” than a power supply. Therefore, this component is often not purchased in the first place, and so to speak, with the last money. However, you should understand: a model with low power may not be able to handle a modern video card. But don't worry - a power supply doesn't cost that much. So, I'll tell you what to look for when buying, and you can decide which one to choose.

Power

The first thing you should pay attention to is the power of the model. You should choose it based on personal needs and the rest of the hardware. If you have an office-type personal computer (weak components, tasks are limited to working with text editors and surfing the Internet), then a 300 - 400 Watt model is sufficient. They are quite cheap, so they are the most popular on the market. But those who like to play modern games will have to fork out for a more expensive power supply unit that can handle all your hardware. It wouldn't hurt to buy some more.

How do you know how much power you need? Fortunately for users, today the Internet is full of services that will help you make calculations to determine the required power for your components. You can calculate it yourself, it’s not that difficult. It is enough to add up the power of all components of your system: motherboard (50-100 Watt); processor (65-125 Watt); video card (50-200 Watt); hard drive (12-25 Watt); RAM (2-5 Watts). It is recommended to add 30% to the resulting number in case of overloads. Go for it!

Efficiency

Newbie users often do not pay attention to this very important point. But it would be necessary. The durability of the power supply, as well as energy consumption, depends on the efficiency. The fact is that the power supply takes a certain amount of energy, but gives back less, losing some. Manufacturers solved this problem by dividing models into classes: expensive - more efficient, cheap - please put up with the loss of energy. This classification is carried out using special stickers: Bronze, Silver, Gold, Platinum (from best to worst).

Connectors

So, we are still far from connecting the power supply - we are deciding on the connectors. There can be no advice here, especially if you have already selected the main components for the system. Choose a set of connectors based on the rest of the hardware. If you decide to pay more attention to the unit by purchasing it first, then take a closer look at the latest models that have received modern ports. Of course, if finances allow.

The standard set of connectors today looks like this: motherboard connector (24-pin), processor power (4-pin), optical drives and hard drives (15-pin SATA), video card power (at least one 6-pin). Please note that if you have a very old system, this set of connectors may not be suitable. And finding a power supply for outdated components is very problematic.

Protection

Faced with various failures and problems, manufacturers gradually endowed their product with all kinds of protection from adverse influences. Today the list of such functions includes dozens of items. Find on the box or in the attached instructions what the model is protected from (voltage surges, failures, and so on). More features are better.

Noise and cooling

Yes, yes, these characteristics are interconnected. A low-power power supply does not heat up much, so its cooling system consists of a small fan. When buying a model for a gaming system, you can be sure that it will heat up no worse than a stove (with the exception of expensive units from well-known manufacturers). There is no escape from the noise that a powerful power supply makes along with other components.

Modern manufacturers offer models with fans of different sizes, the most common being 120 mm. There are also 80 mm and 140 mm blocks. In the first option, there is a lot of noise and poor cooling, in the second, it is difficult to replace the fan in case of failure.


This is all. There are, of course, a number of other parameters that experts pay attention to when choosing a power supply, but they are worth taking into account if you are buying a model for complex (rare) tasks. In other cases - assembling a home PC - our advice will be enough.

Prices

Today, manufacturers offer a huge number of power supplies at a variety of prices. Want to save money? No question, models for an office system can be purchased for around 25-35 dollars. Add another 25 dollars and we have a good 700 Watt power supply. Models for high-end gaming systems can cost $250 or more.

Connecting

Buy - bought, but not to sit on the shelf. Now it needs to be connected. The easiest option, if you are not computer savvy at all, is a friend who will do everything in a few minutes. And if you want to assemble your own system, then wait for a new article in which we will analyze in detail the connection of the power supply. In fact, there is nothing complicated. The main thing is don’t try to push the cable into the connector if it doesn’t want to fit.
Read other interesting articles on the blog, share with friends. Good luck!

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