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Computer power supplies reliably supply the PC with power
A PC power supply unit ensures the computer is supplied with power. Sensitive hardware components such as CPU or graphics card place high demands on the voltage stability. Please find out which power supply formats are available and what was an 80-Plus certification in our guide. In addition, we will tell you what to look for when purchasing a power supply.
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What was a power supply?
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Frequently used formats of PC power supplies
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What connections does a PC power supply have
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What was the 80 Plus certification and what divisions are there?
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Buy a suitable power supply - you should pay attention to this!
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Our practical tip: Don't save on the power supply
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FAQ - Frequently Asked Questions about PC Power Supplies
What was a PC power supply?
Each electrical device requires either a battery, a battery, or a power supply for it to work. This is no different for a computer. The AC voltage from the mains supply is converted into DC voltage by the power supply unit. A PC power supply unit that complies with the ATX standard must provide at least +12 volts, +5 volts, +3.3 volts, -12 volts and +5 volts SB. Of particular importance is that the power supply provides stable voltages with only minimum tolerances. If this were not the case, highly sensitive PC hardware such as CPUs or high-end graphics cards could be irreparably damaged.
Computer power supplies are available, which have either a fully modular, partially modular or non-modular design. With a non-modular PC power supply, all cables are firmly connected to the housing of the power supply. The laying of the complete wiring harness can become a real challenge especially in smaller housings. In the case of a partially modular power supply, only the 20 or 24-pin plug, which is responsible for the main power supply, and the 8-pin CPU connection, are permanently connected. All other cables can be plugged in as required or simply omitted. Once again, the situation is different with a fully modular power supply: Here all cables can be completely separated from the housing. This simplifies the laying of the thick and often not flexible main power cable considerably.
Frequently used formats of PC power supplies
In older computers, power supplies are still available in AT format (Advanced Technology). The main power supply is provided by a two-part plug, the individual parts of which have 6 pins each. However, in modern desktop PCs, AT-format power supplies are no longer important. Accordingly, the use of such models with current mainboards is excluded. The standard for PC power supplies today is the ATX form factor. According to the specification, such a power supply has dimensions 140 x 150 x 86 millimeters (L x W x H). In fact, the length is regularly exceeded, especially for power supplies with higher power. Width and height are maintained, in order to ensure a smooth installation in every ATX PC housing. With older ATX power supplies, the processor is powered by a 4-pin plug, whereas with current hardware, an 8-pin plug takes account of the increased energy consumption. The main power cable has 20 or 24 pins.
The SFX or SFX-L standard is also available especially for particularly compact housings. The cables are identical to those of a conventional ATX power supply unit; only the number of available connections for DVD drives and hard disks is usually lower. The dimensions are 100 x 125 x 63.5 millimeters (L x W x H). If the length is above 100 millimeters, it is referred to as an SFX-L power supply. These usually have a 120-millimeter fan, while a normal SFX power supply can usually only install an 80-millimeter fan. Thin Format Factor (TFX) power supplies are designed for ultra-thin computer chassis. The dimensions here are 175 x 85 x 65 millimeters (L x W x H). Even in this case, the existing connection cables do not differ from a "normal" ATX power supply unit.
What connections does a PC power supply have?
Modern power supplies have a 24-pin plug, which effectively ensures the main power supply of the computer. A 4+4-pin plug for the CPU power supply is also provided. Graphics cards can usually be supplied with power by several 6+2-pin cables. Depending on the power supply, there are also different numbers of SATA and 4-pin Molex connectors.
What was the 80 Plus certification and what divisions are there?
The so-called 80-plus certification for power supplies indicates the degree of efficiency achieved at a utilization of 20, 50 and 100 percent. A distinction is made between six different levels:
The simple 80-plus certification is the beginning. This has an efficiency of 80/80/80 per cent at a capacity utilization of 20/50/100 per cent. The next stage is 80 Plus Bronze and has an efficiency of 82/85/82 percent.
80 plus silver has an efficiency of 85/88/85 percent, while 80 plus gold comes at 87/90/87 percent.
Power supplies with 80 Plus Platinum and 80 Plus Titanium work particularly efficiently. The values are at 90/92/89% and 92/94/90% respectively.
Buy a suitable power supply – you should pay attention to this!
First, you should find out which power supply format is required. A standard ATX power supply unit is usually suitable for normal office PCs and all PC systems that have a regular tower housing. Especially with powerful computers, it may be useful to improve the airflow inside the housing with a modular power supply. So you only have to lay the cables, which are really needed, everything else remains outside and takes no place away. The few remaining cables can be laid much easier or cleaner, was this can contribute to improved air circulation.
The most important aspect of purchasing a power supply is the power required: The bandwidth of the power supplies available today ranges from 150 watts to 2000 watts. But what performance is really needed? The amount of watts a power supply should have depends heavily on the hardware installed. 750-watt power supplies and models that offer even more performance are usually only required for gaming PCs and workstations with multiple CPUs or multi-GPU systems. For an average computer with a powerful graphics card, a current processor, two hard disks and two fans, power supplies with more than 550 watts are rarely required. A PC with an Intel 9900K CPU, a GeForce RTX 2070 SUPER, two RAM modules, a M.2-SSD as well as a normal hard disk and three fans requires approx. 430 watts under load. For a simple office PC, power supplies with a power of 300 watt are still sufficient today.
When purchasing, the power supply unit must also be as efficient as possible. The higher the 80 Plus certification, the more efficient the device will operate. However, the price also increases significantly to the same extent. Below 80 Plus Bronze, you should no longer buy a power supply today; in terms of price and performance, 80 Plus Gold is in many cases the ideal middle way. There are also big differences in volume: If the computer is to be operated in a particularly noise-sensitive environment, semi-passive or completely passive power supplies are a good choice. With a semi-passive device, the built-in fan stops up to a certain temperature. If the limit is exceeded, the fan will continue to work until the temperature has dropped again. A passive power supply, on the other hand, has no fans at all. Sufficient ventilation of the housing is strongly recommended when using such a model.
Our practical tip: Don't save on the power supply
It is generally recommended that quality is a priority when selecting a power supply. A supposed bargain can turn out to be the opposite if it burns off under full load during the first use. This can not only destroy the hardware installed in the PC, but in the worst case, trigger a fire.
FAQ – Frequently Asked Questions about PC Power Supplies
What was the difference between a single-rail power supply and a multi-rail power supply?
The terms single- or multi-rail refer to the available +12 V-rails. With a single-rail power supply, any component, no matter how it is connected to the power supply, can consume the full power. However, the integrated surge protection only engages at a relatively high current, which was in extreme cases already damaging for some power supplies. On the other hand, in a multi-rail device, the current is divided into several +12 V busbars, the power of which can be limited. This effectively prevents the power supply from blowing, but it is not possible to split the available current between the individual rails. Theoretically, a connected device might not be supplied with sufficient power.
How long does the power supply manufacturer guarantee?
This depends on the manufacturer and often also on the respective model. In addition to the legally binding guarantee, well-known manufacturers usually give a 2 to 5 year guarantee. With particularly high-quality power supplies, 7 to 12 years are possible.
What was a redundant power supply?
A redundant power supply is usually used for servers and computers that must have high resilience. This is a housing, the so-called backplane, in which several individual special power supplies are inserted. If one of the devices fails, the power is supplied by one of the other power supplies in the backplane. Hot-swap capability allows the defective device to be replaced during operation. Corresponding power supplies are available in ATX or EPS format. In addition, there are special power supplies for 19" servers in 1 or 2 HE.
How much power do current high-end graphics cards require?
Depending on the graphics card, the power requirement varies significantly. Here are some examples of current graphics cards: An NVIDIA RTX 2060 SUPER requires up to 175 watts, but with the stronger RTX 2070 it IS ALREADY 215 watts. The RTX 2080 SUPER needs up to 250 watts under full load. A Radeon RX 5700 from AMD requires 180 watts and the RX 5700 XT requires up to 225 watts.