You might have heard of the term “power supply unit” (PSU) or “SMPS” (switch mode power supply) — yes that’s a part of your computer system, even if you haven’t heard of it. The power supply is not only one of the most important parts in a PC, but unfortunately, it’s also the most overlooked one. People brag and spend hours discussing their PC’s processor speeds, monitor size, amount of RAM and disk storage but rarely specify the device that powers their system. there’s no respect for the humble and unglamorous metal box that sits at a corner of your system.
When a system is put together to meet the lowest possible price point, what component do you think the assembler or manufacturer compromises on? Yes, it’s the power supply unit, and it is that same device which most often responsible for internal damage in your system, be it burnt motherboards, CPUs, graphics cards or other components that were killed due to electrical faults. So you save on the PSU while buying a PC and pay much more for the mistake later.
Even if people pay little attention to PSU, they are more concerned about the power rating label that is stuck on them by the manufacturer. Without regard to whether the power being produced is clean and stable or whether it is full of noise, spikes and surges. A person building a new PC should give special emphasis on selecting a power supply to get a robust and reliable unit. It will ensure peace of mind throughout the life time of the PC.
Basic functions of a PSU
The basic function of a power supply is to convert the electrical power available (AC 120V, 50Hz/AC 240V, 50Hz) to that which the computer circuit can use (DC +3.3V, +5V, +12V). The objective in manufacturing a power supply is to provide an efficient power source which generates minimum heat. If you observe a power supply unit, you are sure to notice that there is a fan built into it. Now that fan throws out hot air from inside the cabinet thereby keeping the PSU as well as the whole system cool. The fan diameter typically ranges from 60mm to 200mm or even larger, depending on the manufacturer. It’s basic logic that larger diameter fans will throw out more air and thereby keep the system cool, but efficient PSUs may not need large fans as they generate less heat. Therefore fan size is not a major criterion while deciding on a PSU.
Power is generally supplied to the motherboard over multiple wires connected to the same source circuit called rail or tap inside the power supply. Each rail can be imagined to be a separate power circuit supplying a specific power rating. There are generally +3.3V, +5V, +12V rails which are technically independent inside the power supply, many cheaper designs have them sharing some circuitry, making them less independent than they should be. This can cause voltage regulation problems in which a significant load on one rail causes a voltage drop on others. Components such as processors and graphic cards can vary their power consumption greatly by their activity. When you suddenly load a graphics intensive game, it causes the processor as well as the video card to more than double the power consumption on the +12V rail which powers them. In these cases, cheaper power supplies can cause voltage fluctuations causing the system to crash. Better designed power supplies feature independent rails with better regulation and better quality wires to draw power from the rails.
Most switched-mode power supplies with more than 75 W of output power must include passive PFC, at least. 80 PLUS power supply certification requires a power factor of 0.9 or more. Where power factor is purity of the DC voltage obtained, here 1 power factor means it is completely pure. An “active power factor corrector” (active PFC) is a power electronic system that controls the amount of power drawn by a load in order to obtain a power factor as close as possible to unity. The purpose of making the power factor as close to unity as possible is to make the load circuitry that is power factor corrected appear purely DC and this ensures proper working of the internal components of the PC and its longevity.
It is frequently used in practice, for example, SMPS with passive PFC can achieve power factor of about 0.7–0.75, SMPS with active PFC can supply up to a 0.99 power factor, while a SMPS without any power factor correction has a power factor of only about 0.55–0.65. Due to their very wide input voltage range, many power supplies with active PFC can automatically adjust to operate on AC power from about 100 V to 230 V. So it is always necessary to look out for PSUs with active PFCs.
So now that you know the basics of power supply units, go get yourself the right one if you are still using cheap PSUs which can cause potential harm to your system. The best way to decide on a PSU is to calculate the power requirement for your system and then zeroing in on a particular brand or model by searching their reviews on the net.
==== About the Author ====
Abhijoy Sarkar is a 19 year old tech enthusiast currently pursuing B.tech in Electronics and Communication. Anything technical is always his cup of tea. He has a fetish for gadgets, automobiles and books (except course books). He also loves gaming, photography, listening to music, watching movies and experimenting with gadgets as hobbies.Spend a lot of time researching on web on different topics. His passion for technology and sharing knowledge motivated him to start his writing work. He is co-writer at www.linuxb.in a blog focused on linux and open source community.