What is a power supply? and how it works?

What is a power supply ? It is simply the piece of hardware that is used to convert the power supplied from the outlet into usable power for the many parts inside the computer case.

Do you want to know more about what a power supply is and how it works? Do not miss our article!

Index of contents

What is a power supply?

A power source converts alternating current (AC) into a continuous form of energy that computer components need to function, called direct current (DC). Unlike some hardware components that are not mandatory to use, such as an SSD, the power supply is a crucial piece because, without it, the rest of the internal hardware cannot work.

The power supply is often abbreviated as PSU and is also known as a power source. Motherboards, boxes, and power supplies come in different sizes called "form factors." These three elements must be compatible for them to work properly together.

A power supply in the box

The power supply is mounted on the back of the box or chassis. If you follow the power cord of the computer, the one that is connected to the wall, you will see that it connects to the back of the power supply.

The back is the only part of the power supply that most people see. There is also a fan opening on the back of it that sends air to the back of the PC case.

The side of the power supply that faces the outside of the box has a three-prong male port into which a power cord plugs in and the other end is directly connected to the wall outlet.

It also often includes a power switch, and a red voltage switch on very, very low level sources.

Inside the PC, a large number of cables extend from the source. The connectors located at opposite ends of the cables connect to various components within the computer to supply power.

Some connectors are specifically designed to connect to the motherboard, while others have connectors that adapt to hard drives, optical drives, graphics cards…

Power supplies are rated by watts to show how much power they can provide to the computer. Since each part of the computer requires a certain amount of power to function properly, it is important to have a power supply (PSU) that can supply the correct amount.

How a power supply works

If there is any component that is absolutely vital to the operation of a computer, it is the power source. Without it, a computer is just an inert box full of plastic and metal.

Power supplies use switching technology to convert AC input to lower DC voltages. The most used voltages are:

• 3.3 volts 5 volts 12 volts

Today, approximately 90% or 95% of the load is on the 12V rail. Therefore, the other rails remain in an increasingly secondary position.

The power of a power supply always appears in watts. A watt is the product of the voltage in volts and the current in amps or amps.

Today, a computer is turned on with a small button and turned off with a menu option or with the button itself. These options were integrated into the standard PSU several years ago.

In this way, the operating system is able to send a signal to the PSU in order to signal it to shut down. The push button sends a 5 volt signal to the power supply to tell you when to turn on. The power supply also has a circuit that supplies power in standby, called 5VSB (5 volts stand by), even when the computer is turned off, so that the devices that remain on in standby can work and the source can be turned on.

Before approximately 1980, power supplies tended to be heavy and bulky. They used large, heavy transformers and huge capacitors to convert the line voltage at 120 volts and 60 hertz into 5 volts and 12 volts DC.

The power supplies used today are much lighter and smaller (there are ATX, SFX and other dimensions). They transform the current from 60 Hz (Hz, or cycles per second) to a much higher frequency, which translates to more cycles per second. This conversion allows a small, lightweight transformer in the power supply to make the actual voltage reduction of 115 volts (or 230 in Europe and most of the world) to the voltage required for that particular component.

The high-frequency alternating current supplied by a PSU is also easier to filter and rectify compared to the original 60 Hz AC line voltage, reducing voltage variations and noise for sensitive computer electronics.

A switched power supply takes only the power it needs from the AC line. The typical voltages and currents of a power supply are indicated on the label.

Standardization of power supplies

Over the years, there were at least six different power supply standards for PCs. A few decades ago, the industry decided to use ATX- based power supplies.

ATX is an industrial specification, that is, the PSU has the physical characteristics to fit a standard ATX box and the electrical characteristics to work with an ATX motherboard.

The PC power cables use standard connectors and are designed in a way that makes it difficult to connect the wrong connectors. Also, fan manufacturers often use the same connectors as power cables for disk drives or peripherals (Molex), allowing a fan to easily get the 12 volts it needs.

PSU problems

The computer's power supply is surely the component most likely to fail, as it goes into heat and then cold with each use, and receives the first AC input when the PC is turned on.

A non-working fan, continuous random PC restarts, crashes on load, and even gaming performance issues can all be a symptom of a faulty, poor-quality, or insufficient power supply. You should be aware that the components of the source degrade over the years, and what 10 years ago was an 850W source, today it could be 650W, and its performance can also be affected and endanger your components.

A high quality font should last 10 years with no problems. Anyway, we recommend that if you are going to renew your equipment and the fountain is about 10 years old, you should change it for a quality one.

For any problem that you suspect is the fault of the power supply, you can either process a warranty, try another unit… However, what you should never do is open it for repair. Many will disagree, but with the complexity of its interior components, voiding the warranty that comes with opening it, and the possibility of electric shocks even disconnected should be considered.

It is very difficult for you to repair a fault in a source without having its electrical schematic and / or advanced knowledge of electronics.

Power supply improvements

Today, new internal designs have emerged in power supplies, such as VRM (voltage regulation modules) voltage regulation, which are independent. They are the DC-DC sources. Its main advantage is that the voltages do not trigger when the load is unbalanced, a situation that occurs very commonly in current PCs (remember the 12V load compared to the other rails).

Recent designs on web servers include power supplies that offer a spare source that can be swapped while the other power supply is in use.

Some new computers, particularly those designed for use as servers, provide redundant PSUs, that is, there are two or more PSUs in the computer, one of which provides power and the other acts as a backup.

The standby source takes over immediately in the event of a failure by the primary source. The primary power can then be changed while using the other power source.

External power supplies

But the power supplies located inside a PC are not the only ones that exist. The other type of power supply is external.

For example, some game consoles have a power supply connected to the power cord that must be located between the console and the wall. In other cases, the power supply is built into some external hard drives, which are required if the device cannot extract enough power from the computer via USB.

External power supplies are beneficial because they make the device smaller and more attractive. However, some of these types of power supplies are quite large and their placement could be problematic.

Current peaks

Power supplies are often victims of surges and current spikes, as this is where the device receives electrical power. Therefore, it is often recommended to plug the device into a UPS or a surge protector with circuit breaker.

Power

The PSU rating is usually the most obvious metric for choosing a power source. If you choose a power source with very little power, your system will shutdown when it consumes more power than the PSU can provide. Conversely, buying a ton of watts could be a waste of money. So what is the most convenient?

The key is to create an estimated power consumption for your PC. Each new component will change the amount of watts your system needs to keep running. Overall, we're moving toward energy efficiency, and new CPUs and GPUs are consuming less and less.

To estimate watt demand you can use the calculator at Outervision.com, which allows you to select the make and model of CPU and GPU, storage and other components. If you are planning to overclock your system, you can also configure the CPU clock, voltage, the GPU clock and the graphics card clock. In any case, it is usually more convenient to receive expert advice than that of a calculator.

When you've entered all the details you want to include, the calculator displays three numbers: load power, recommended UPS power, and suggested PSU power.

To set a wattage that you can easily find, do a few things. First, round up the power to the nearest 50W mark (370W would round up to 400W). With this method, you can usually find a power source that delivers ample power, even if you upgrade to something more powerful in the future.

For some systems, that additional 50 W or more may not be warranted. Locked CPUs (Intel CPUs without the "K" or "X" designation) are much less likely to be used in situations where they consume more power than their specifications require. Also, these CPUs tend to decrease their maximum clock speed when heated, which helps save power as well.

When it comes to unlocking CPUs and overclocking the GPU, it's better to have plenty of power. This can be useful when you want to overclock, or when adding components to an overclocking system. Overclocking often requires better cooling, and each fan and water pump will also draw watts.

It is also worth noting that your system will not always be at maximum power. Most PCs only consume 100 watts or less while idle, and rarely more than 150W while doing everyday tasks like working on documents or surfing the web. But you want the power supply to handle peak power requirements, not typical loads.

Efficiency and 80 Plus Certification

Electronics never works at 100 percent efficiency in the real world. The "80 Plus" label on a PSU denotes that it has been rated for a certain level of efficiency. Before we turn to 80 Plus Certification, let's talk about efficiency.

When a power supply (or other device) is 80 percent efficient, 80 percent of the rated power is delivered to the system, and the other 20 percent is lost in the form of heat. If a power supply is drawing 500 W from the wall and is 80 percent efficient at 100 percent load, you can only deliver 400 W at maximum output. Such a PSU will be rated at 400W, since it is the maximum power that will be delivered to the system.

Since the PSU's rated power takes efficiency into account, there isn't much math to do. That's it, unless you care about electric bills. If you like to keep your PC on all the time, or if you spend long hours playing, a more efficient PSU can save you money.

If the same 400W power supply is 90 percent efficient, it will draw 444W (instead of 500W) from the wall to deliver the 400W to your PC. That difference equates to almost the same energy as a 60W light bulb. And the more you play demanding games, the more kilowatt hours begin to accumulate.

It is important to note that the efficiency of the power supply is not linear and changes depending on the load. The 80 Plus specification requires that a power supply be at least 80 percent efficient at 115V (in the United States) on all loads of 20 percent or more. For 230V (EU) connections, a PSU must be 82 percent efficient at 20 and 100 percent load, and 85 percent efficient at 50 percent load.

Part quality is another great reason to get a more efficient power supply. The more efficient a PSU is, the less heat it generates. That tends to mean the components last longer, and you don't need to use the cooling fan as much. Still, this is not always true. For example, think of an 80 Plus Gold fountain with poor quality capacitors and a short-lived fan, with absurdly small heatsinks, and an 80 Plus Bronze with a leading fan, generous heat dissipation, and decent capacitors. Without a doubt, the Bronze is better.

Some power supplies are efficient enough that you don't have to plug in the fan all the time. Depending on your case, a less efficient power supply has the potential to increase the ambient temperature inside the box.

This goes without saying, but a more efficient power supply is also greener. A high-powered gaming PC under load is an important device, just like a washing machine or a fridge. Consuming less energy reduces the load demand of the entire network, which can help keep spikes offline, especially in times of high demand.

Guarantee

When shopping for PC components, you'll often find products that don't seem to make any significant difference on their respective spec sheets. When this happens, it can be helpful to go with a brand you prefer, or to look at something much less attractive than technical specifications: the warranty.

As of today, a source with a 2-year warranty is behind on the market and should not be considered. Although they vary, most PSUs come with a three to five year warranty. However, a seven and ten year warranty is offered with some products. This is not a direct indicator of quality, but it is a kind of limited insurance worth considering.

Modular power supplies

After power and efficiency, modularity is one of the most important selling points for fountains. In many cases, a modular PSU power supply is ideal. In others, it is the last thing you want. But what makes a PSU modular?

Simply put, a modular power supply allows you to connect (or disconnect) cables as needed. Traditional power supplies, on the other hand, have cables permanently connected to the power supply.

Semi-modular PSUs strike a balance between the two: some cables (usually the motherboard and CPU cables) are permanently connected, while other cables (PCIe, SATA, and Molex) are detachable.

Modular PSUs have a huge advantage when it comes to cable management. Cable management can be one of the most tedious and expensive tasks in PC construction. A modular power supply allows you to use only the cables necessary to mount a PC, which can significantly reduce cable clutter in the box. This can sometimes improve air flow in addition to aesthetics.

The downside to having detachable cables is that the cables themselves generally use proprietary connectors. Even cables from different product lines from the same manufacturer may be incompatible. As such, it is always advisable to store cables in a box or bag to store them safely for later storage.

Modular PSUs also take up more space in the box than non-modular models. On ATX towers this is not usually a problem, but it can cause real problems on a mini-ITX system. The connectors on the end of the cables add approximately 1/2-inch to 3/4 of an inch to the length of the PSU. Non-modular PSUs, on the other hand, do not have connectors on the end of the PSU, since the cables simply go out the back of the unit.

In cases where the clearance at the rear of the PSU may be very tight, consider using a non-modular power supply if the construction permits. It will be more difficult to store unused cables, but clearance will be less problematic. If space is not an issue, modular or semi-modular fonts are generally recommended. It will clean the structure and allow you to replace the cables when necessary.

Size Matters

Like everything else that goes into a PC case, the physical dimensions of a PC can have a big impact. While this is generally manifested with higher power PSUs, even low watt models may be too large in some versions. It can be difficult to get a 1600W PSU EVGA source to fit a medium power tower, but it is much more difficult to get a PSU ATX source in a mini ITX box if things are tight.

Although there are some boxes that support the smaller SFX form factor, many mini-ITX boxes are still built for PSU ATX. This is a mixed blessing. There is not a wide variety of PSU SFX available for the consumer, so going with ATX gives more options. Even with that choice, you have to choose the pieces carefully. ITX boxes, for example, are only capable of accepting fonts with a certain configuration and size. In such a small space, having a modular power supply is highly recommended, but extremely expensive in a special format: SFX.

Conclusion about What is a power supply?

It is true that PSUs are not the sexiest part of a PC. A good PSU doesn't offer aesthetic points to display with your friends, like a good CPU or GPU, but the right PSU will ensure that you are able to use those parts to their full potential.

Would you buy a sports car just to use the cheapest gasoline you can find? PSUs can be like high octane fuel for your gaming gear, helping to provide clean power and ensuring that everything doesn't go up in smoke.

If there is one last tip, it's not to skimp on your PSU. You can always buy more storage or RAM, but a bad PSU can spell disaster.

A solid power supply with enough spare power will give the system longevity and ensure worry-free upgrades. If you have questions you can always consult our guide on the best power supplies on the market, here you will find the best models by price range.

What did you think of our article on what is a power supply? Are you missing something?