What Is A PSU? Components, Types, Pricing, Explained!

The power supply unit is the engine of the computer. It is responsible for converting the raw voltage into a usable voltage that the computer can use. Most can say it can also be the heart of the computer since it pumps electricity throughout the computer, just like a heart pumping blood through our body.

what is a psu
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You can find a power supply by looking at your chargers. Do you see those adapters? Those are somewhat kind of a power supply. They also convert raw voltage to usable voltage that our phones can take. Since smartphones batteries are tiny, they also need smaller amounts of power to charge. So, what’s the difference between the adapters and a power supply?

Well, it’s actually the devices they serve. A cell phone is small, compact, and portable, so it only needs an adapter. In contrast, a power supply unit serves a whole computer. The PSU gives enough power to all the components of the computer.

What Is A PSU On A Computer?

A power supply unit or PSU is the electronic circuit that converts high-voltage alternating current to lower voltages used by personal computers, called a direct current. In addition, it supplies voltage to regulate the operation of the computer’s internal components.

Each kind of power supply has its own set of advantages and disadvantages. It’s crucial to consider a range of aspects, including your budget, the unit’s form factor, and the number of ports it has.

Additionally, you must ensure that you have adequate watts to power all of your system’s devices.

In a much more technical sense, a power supply is called a rectifier. However, a power supply is what our computer needs since it supplies our components with the right and proper amount of power for it to function correctly.

We need our nervous system to function properly and accordingly. There are tons of complicated things when it comes to talking about motherboards. Let’s break some of them down and erase the confusion.

How Does The Power Supply Work In A Computer?

A computer’s power supply unit is the component that provides all of the computer’s other components with electricity. As a result of the rapid on-and-off switching of the AC voltage, a series of DC pulses are generated. Because a transformer isn’t required for this conversion, the SMPSU (switching mode power supply unit) is more efficient than other power supplies.

A feedback controller controls the number of voltage pulses generated every time by raising or reducing the duty cycle. If the current load going through the circuit becomes too much, the power supply will shut down, saving computer systems from being damaged in the case of an electrical failure. Once the power supply has finished its internal testing after the overload, a signal is transmitted to the motherboard, telling it that everything is in working order.

History Of Power Supply Unit

The original IBM PCs power supply only delivered 64 watts of electricity, which pumped a staggering 5 volts across the CPU, which would destroy any current consumer-grade chip. Because the old-school power supply only had a hard power switch, everything was always either completely on or entirely off.

The physical architectures of these earlier power sources were particularly challenging. Even during the AT power supply period, which ran from 1984 to the late 1990s, there were not only several distinct form factors such as baby AT or XT, but some systems even had switches soldered directly to the computer chassis out of the power supplies.

Among these many form factors, there was no universal standard for actual pinouts onto the motherboard. When Intel developed the ATX standard in 1995, it spared us from an eternity of proprietary form factors. Mainly because it accomplished so much more than just making our power supply around the same size.

ATX power supplies have changed; they are now available in big and compact sizes, with 80 and 120-millimeter fans. ATX also introduced us to items we now take for granted, such as the 20 and subsequently 24-pin connectors that serve as the main power supply for all current PCs. The connections that link to the motherboard, on the other hand, allow intelligent power management and a stronger focus on the 12-volt power supply.

Types Of Power Supply In Computer

A power supply’s type or form factor tells you a lot about the device, including how big it is and what functions it supports. Knowing the most popular power supply form factors might help you make an informed decision. These pointers will help you get the most out of your power supply, both in terms of its ability to fit in your case and its efficiency:


A 24-pin connection has replaced the earlier 20-pin connector on ATX power supplies, which was used to provide power to the motherboard (which are still used with previous generations of 20-pin motherboards). An additional 3.3V rail is included in ATX power supplies. Soft-off, a feature supported by ATX, is an example of a part that may be used to switch off the power supply.


Technically, ATX12V is superior to standard ATX, although the two power supplies are identical in terms of size and appearance. ATX12V power supplies are now the most used form factor. However, they have evolved through time. Newer ATX12V versions include ATX12V 2.1 and ATX12.2. In addition to having a 24-pin mains plug, these models have been fine-tuned for maximum performance.

SFF (Small Form Factor)

Several small power supplies have been created for compact cases throughout the years. Smaller than the standard ATX, SFF or SFX power supplies might be ideal for budget setups worried about desk space. The CFX12V (Compact Form Factor), LFX12V (Low Profile Form Factor), and TFX12V are all examples of SFF power supply (Thin Form Factor).


Additional CPU power connections are available in EPS12V power supplies, making them more stable than ATX12V power supplies. EPS12V form factor power supplies, on the other hand, are not compatible with most typical home PC components.

Components And Parts Of PSU



Stepping AC voltage up and down and providing electrical isolation is accomplished by a transformer. The frequency is not altered while the energy is transferred between the primary and secondary windings. The secondary winding of the transformer is connected to the load, while the primary winding is connected to the AC source.


Using a rectifier, AC electricity may be converted to alternating current and then back again. A diode, a one-way rectifier, is the most common rectifier in use today. The three most common diode-based rectifier circuits are the half-wave, full-wave bridge, and full-wave center-tapped.


The filter smoothes down the rectifier’s pulsing DC output. Ripple is the AC component of a signal that remains after rectification is complete. Large waves might damage the load. C-filters and RC filters are the two most common power supply filters. C-filters are the simplest of the two options, making them ideal for beginners.

Regulator Circuits

Because of the voltage regulator, the load can work correctly, even when the input voltage fluctuates significantly. A shunt voltage regulator and a series voltage regulator are the two most prevalent configurations.

All PSU Brands

Most of these brands are the brands you also hear when it comes to computer cases. Well, since a power supply unit is also found within a computer case, these brands have made their combinations for easier compatibility.

CorsairGot the best of the cheapest gaming PSU
XPGHas the best PSU with around 650 watts
Cooler MasterHas the best PSU with around 750 watts
be quiet!Has the best PSU with around 1250-1500 watts
SilverstoneGot the best of the SFX-L PSU
SeasonicHas the best PSU with around 1000 watts
Fractal DesignGot the best of the small form factor PSU

How Much Does A Power Supply Unit Cost?

Typically, it costs you around $40 in the low-end range for a good power supply unit, there’s even cheaper, like literally $10, but I do not suggest you take that risk with all your precious components. I recommend those that range around $50. Although, the actual typical range for a PSU is about $50 to $700 (even more). Like every other computer component, there’s a mid-range one perfect for you, but there is also a high-end one ideal for you. It just depends on your components and budget. 

It’s essential to know your devices and components. Choosing the correct power supply is necessary, even if it’s not as eye-catching as other components. Details and specifications are critical when selecting a power supply, and you should always confirm that your power supply and other components are compatible before making a purchase.

Frequently Asked Questions

Wrap Up

Woo! That was a lot, huh? But let’s relax now. I know it was a bit overwhelming to learn about PSUs, but personally, it’s just a game of electrical and electronics. Which are probably learned by everyone when we were in high school. 

I hope this serves you well, and remember, pick the right one for your components! You do not want to fry your components with the wrong PSUs. 

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Anna Bonilla
Anna Bonilla

Anna isn't just any ordinary Computer Hardware Expert, she's highly skilled and multi-talented. She's a graphic designer, a writer, and a social media expert. At ErrorBook, she helps her readers in understanding the purpose of different hardware components and also helps pick the best PC Parts for their money. She also loves babysitting her nephews, baking, and crafting coffee.

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