What is a Power Supply Unit (PSU)?

A Power Supply Unit also known as PSU is an essential computer hardware component that converts alternating current (AC) into direct current (DC) and then supplies voltage to every component connected to the system. The power supply transforms a 110-115 or 220-230 volt AC to a stable low-voltage DC that the computer can use and is rated by the number of watts it generates.

Most of the power supplies are switched-mode (SMPS), which improves efficiency and simplifies design for different voltage inputs. PSUs have the abilities where the power input varies.

Why Power Supply Unit is Important?

A power supply is needed and works as an essential component in the computer system for the following reasons −

• Conversion of AC to DC Power − A primary function of a PSU is to convert AC from the wall outlet into DC and make computers” important components functional like the motherboard, CPU, GPU, and storage drives because they operate on DC power.
• Voltage Regulation − A PSU supplies the required voltage to different components to ensure that they receive the required voltage to perform +12V, +5V, and +3.3V.
• Power Distribution − A PSU works as a power supply distributor for the different components connected to the system.
• Protect system − A PSU also protects systems from overvoltage short-circuit, and thermal protection.
• Energy Efficiency − Efficient power supplies can cut electricity costs and the environmental effects of running a computer.

How Does a Power Supply Unit (PSU) Work?

A Power Supply Unit works by converting AC to DC and supplying required voltages to the different components connected to the system. Following are the steps to demonstrate how a PSU works −

• AC voltage as input − The PSU takes AC voltage as input.
• Rectification − A rectifier converts inputted AC voltage into DC.
• Filtering − The rectified DC power is subsequently filtered by capacitors to smooth out fluctuations and remove ripple, producing a more stable DC voltage.
• Switching − Switching is a process of sending filtered DC power to a high-frequency transformer; the switch-mode power supply (SMPS) converts DC voltage to high-frequency AC. This high-frequency AC enables the use of a smaller and more efficient transformer.
• Transformation and Isolation − The high-frequency AC is then transferred using a transformer, which steps down the voltage to the desired levels. This transformer keeps isolation between input and output to improve safety.
• Rectification and Filtering Again − The transformed AC voltage is rectified back into DC with diodes. This DC is then filtered once again with capacitors to remove any residual ripple, resulting in get stable DC voltage.
• Voltage Regulation − Voltage regulators are used to keep output voltages within limits, despite the changes in input voltage. This is critical to the computer”s stable operation.
• Output − The regulated DC voltages are supplied to every component connected to the system using specified connectors and cables. It includes common voltages like +12V, +5V, and +3.3V.
• Protection Mechanisms − Modern PSUs protect the system from overvoltage, short circuits, and thermal protection.
• Cooling − PSUs are equipped with cooling fans which keep systems cool from system heat generated during operations.

Types of Power Supply Units

Types of Power Supply are as follows −

• ATX Standard − These are the most common PSUs usually used in desktop systems. These power supplies are tailored to be compatible with the ATX motherboard and deliver three distinct positive voltage rails: +3.3 V, +5 V, and +12 V, in addition to a standby voltage rail of +5 V SB, which ensures that computers receive power when in standby mode.
• Entry-Level Power Supply Specification (EPS) − Based on the ATX standard, this PSU was specifically designed for servers. It sets a more stable environment for critical applications than ATX standards, which makes it perfect for critical servers.
• Small Form Factor (SFX) − These PSUs are used in smaller form-factor computers using MicroATX motherboards. These are the power supply units used in smaller set-top boxes like DVD players and cable boxes.
• Thin Form Factor (TFX) − TFX power supplies are longer and thinner than traditional ATX power supplies which are used in ultra-slim and low-profile desktops.
• Modular and Semi-Modular Power Supply − Modular PSUs allow users to connect using cables; this process minimises cable clutter and improves airflow while Semi-Modular PSUs use fixed and detachable cables.
• Non-Modular Power Supply − All cables are permanent and not removable. These are frequently less expensive, however, they result in more cable clutter.
• Laptop Power Supply / AC Adapter − External power supplies that convert AC to DCto power laptop computers. These are referred to as power bricks or AC adapters.
• Uninterruptible Power Supply (UPS) − An external device that provides backup power during power outages, rather than a computer”s power supply unit. It contains batteries and can keep a system working for a short period if the main power fails.

Functions of a Power Supply Unit

The Power Supply Unit (PSU) in a computer performs different essential functions. Some of them are as follows −

• Power Conversion − The main function of a PSU is to convert AC from the wall outlet into DC. Generally, it provides multiple DC voltage outputs like +12V, +5V, +3.3V.
• Voltage Regulation − A PSU supplies the required voltage to different components to ensure that they receive the required voltage to perform +12V, +5V, and +3.3V. This is crucial for reliable operation and stable voltage.
• Power Distribution − A PSU works as a power supply distributor to the different components connected to the system like motherboard, CPU, graphics card, storage devices, and peripherals.
• Protection Mechanisms − It protects the system from overvoltage short-circuit, thermal protection, and over-temperature.
• Efficiency − PSUs reduce power wastage and reduce electricity costs.
• Cooling − It supports system cooling by heat dissipation and temperature management.
• Standby Power − The PSU can provide standby power (often +5VSB) to support features such as Wake-on-LAN and allow the system to execute specific tasks during low power mode or when the system is turned off.

How to Choose a Power Supply Unit (PSU)?

When choosing the right Power Supply Unit (PSU) for your computer; the following considerations are required −

• Determine required power watt − You should estimate the total wattage needed for the system like CPU, GPU, motherboard, RAM, storage drives, and any peripherals. A user should also keep in mind about future upgrades for the system.
• Efficiency − Efficient PSUs can lower electricity costs.
• Connectors and Cables − It determines that the PSU has the required connectors and pins.