Power Supply Units

What is the function of a PSU?

Power Supply Unit

• Convert 100 - 240V AC Current into DC voltage that are computer needs to operate

What are the DC voltages does a PSU output?

+3.3V, +5V, +12V, and -12V

Why do PSU produce multiple DC voltages?

Different computer components require different levels of power?

What components use +3.3VDC?

Modern CPUs, chipsets, RAM, SSDs (NVMe/M.2), PCIe/PCI logic circuits

What components use +5VDC?

USB ports, hard drive logic boards, SSDs (SATA), and older legacy devices

What components use +12VDC?

CPU, GPU, case fans, water pump, and the motors inside hard drives and optical drives

What components use -12VDC?

Legacy ports and some older audio chips

• Still required by ATX standard

What is the difference between 110-120 VAC and 220-240 VAC?

110-120 VAC is the standard wall voltage in North America and parts of Asia; 220-240 VAC is the standard in Europe, UK, Australia, and most of the world

What is wattage rating?

The total continuous power output a PSU can deliver (e.g. 650W)

What is PSU energy efficiency?

Efficiency = Useful DC output / by a power drawn from the wall

What is the 80 PLUS standard?

The 80+ certification program rates PSU at 80%, 85%, 90%, 92%, or 94% plus efficiency at various loads

• Bronze, silver, gold, platinum, titanium

What comes with a more efficient PSU?

Less wasted heat and lower electricity bills

Why is the conversion of AC into DC not perfect?

Heat generation is a side-effect of the lack of efficiency

What does Amps mean?

They are the unit for current flow

• An analogy would be the amount of water flowing through a pipe

What does volts mean?

They are the unit of force

• An analogy would be the water pressure

What does Watts mean?

They are the unit for power

• Would be the power that the water could provide

• Watts = Volts x Amps

• It is what PSUs are rated in

What does Ohms mean?

They are units of resistance

• filter of the barriers in the pipe, that would provide resistance

What is the 20+4 pin motherboard connector?

The main power connector that plugs into the motherboard AX power header

• A 24 pin connector split as 20+4, allowing it to fit both older 20-pin boards and modern 24-pin boards

• A system will not turn on without it

What connectors are important to a system?

• 4+4 (8) pin = CPU power

• 6+2 pin = GPU power

• 20+4 and 24 pin ATX power header

• 4 pin (molex) = devices, some case fans

What is a modular power supply?

A PSU where all (fully modular) or some (semi modular) cables are detachable Pink

• Non-modular PSUs have all cables permanently attached

What are the benefits of a modular power supply?

Reduces cable clutter, improves airflow, and simplifies cable management

What are the disadvantages of modular PSU?

• Some PSU manufacturers use proprietary connectors

• Modular PSU can take up a little more room

What is a redundant power supply (RPS) and what does it do?

• When two or more PSUs share the power load

• One PSU fails, the other (S) instantly take over with zero downtime - this is called hot-swappable redundancy

What are the two types of redundant power supplies?

Redundant power supplies within a system or battery backups

Where are you likely to find a redundant power supply?

In situations where power redundancy is helpful or critical

• Common for servers to have a redundant power supply

What is a battery backup system?

An uninterruptible power supply (UPS)

• A battery backup system that the computer plugs into

• Protects everything that is plugged into it from power surges

What are the drawbacks of a battery backup system?

• They have a limit to the number of devices they can handle at once

• They need to be checked periodically to make sure the batteries are operational

What are the three things you need to pay attention to when looking at a UPS?

• VA = The maximum load the UPS can support, the higher the number the bigger the load

• PF = Power factor, a measure of efficiency, Between zero and 1.0, the higher the number the better

• Watts = wattage supported = VA x PF

What should you pay attention to when choosing a UPS?

Ensure the VA is at least 1.2 times the anticipated need

What are the common symptoms of a failing or undecided PSU?

Random reboots or shutdowns, failure to POST, BSODs, system instability only during gaming/rendering, burning smell or no power at all