A+ Computer Repair Lesson 6 Power Supply Basics

Objectives Define power supply and describe its function. Describe power supply fan features Distinguish among the features of power supply types

Question? Do you know what the leading cause of failures in personal computers is?

Answer Power Supply

Note: The power supply unit consists of a fan and an AC/DC Converter. The AC/DC Converter is made up of a transformer, a regulator, and a rectifier. The rectifier and regulator are composed of resistors, capacitors, and diodes.

Inside a Power Supply

What does a power supply unit do? The power supply's job is to convert AC current to 3.3v, 5v, 12v, and -5v, - 12v DC current for use by internal computer components.

The term “ form factor “ indicates what?

The dimensions and types of features and design—applies to many computer components. Three prominent form factor types are the computer’s power supply, case (chassis), and motherboard.

Power Supply form factors Older power supply form factors are generally found on PCs built prior to the mid-1990s.

Power Supply form factors ATX/NLX ATX and NLX power supplies are interchangeable. Remote switch

Power Supply form factors SFX Intel designed the SFX to be used in Micro-ATX and Flex-ATX form factor systems. SFX power supplies do not supply -5v DC power and may not work with certain ISA cards. Remote switch

Power Supply form factors PC/XT The first form factor standard Rocker switch

Power Supply form factors AT The AT form factor introduced the first tower cases. AT power supplies designed for tower cases had a remote power switch at the front of the case instead of a rocker switch on the power supply. Rocker switch

Power Supply form factors Baby AT Baby AT power supplies can often fit in regular AT cases. Rocker switch

Soft Power Soft power allows an ATX computer to perform some neat tricks, such as being turned on remotely through a network or across a modem. Soft power allows the operating system to shut off the computer on shutdown.

Soft Power Power in an ATX computer is controlled by the computer’s complimentary metal-oxide semiconductor (CMOS). When the power button is pressed, it shorts a connector on the motherboard that sends a signal to the CMOS, telling it to bring the computer to a fully on state.

Linear Power Linear power supplies—sometimes called AC adapters—typically waste a lot of energy. You can feel the energy loss: touch the adapter while it's working. A warm power supply means energy is being wasted.

Switched Power The power supply your PC uses is a "switching" type, converting electricity more efficiently than a linear power supply.