Power Supply

Power Supply

The internal power supply is responsible for converting your standard household power into a form that your computer can use. The power supply is responsible for powering every device in your computer; if it has a problem or is of low quality you may experience many difficulties that you may not realize are actually the fault of the electrical system. This section discusses what makes up the power supply and how it works in detail. In depth, power supply of computer has following function.

1. it converts household AC power supply to DC power because the computer system use (-12 V to +12 V) DC power in computer system but household power supply of NEA in 220V.

2. it distributes power supply in different parts of computers system through different cable according to requirement of parts

The power supply plays an important role in the following areas of your system:

Stability: A high quality power supply with sufficient capacity to meet the demands of your computer will provide years of stable power for your PC. A poor quality or overloaded power supply will cause all sorts of glitches that are particularly insidious, because the problems occur in other, seemingly unrelated, parts of the system. For example, power supplies can cause system crashes, can make hard disks develop bad sectors, or cause software bugs to appear, problems which can be very difficult to trace back to the power supply.

Cooling: The power supply contains the main fan that controls the flow of air through the PC case. This fan is obviously a major component in your PC's cooling system.

Energy Efficiency: Newer PC power supplies work with your computer's components and software to reduce the amount of power they consume when idle. This can lead to significant saving over older systems.

Expandability: The capacity of your power supply is one factor that will determine your ability to add new drives to your system, or upgrade to a more powerful motherboard or processor. Many people don't realize, for example, that a high-speed Athlon CUP and motherboard consume far more power than a similar Pentium-based system, and the power supply needs to be able to provide this power. If you build a new system with a power supply that barely meets your needs, you may have to replace it when you upgrade down the road.

Power Supply Types

Power supplies typically have two basic design formats, known as linear and switched-mode. The linear supply is a relatively simple design that becomes increasingly bulky and heavy for high amperage devices, the switched supply is capable of being much smaller and more efficient but its design is much more complex and sophisticated.

Linear Power Supply

It does not have any feedback of power, therefore it is called linear power supply and the design is also simple.

A simple AC powered linear power supply usually uses a transformer to convert the voltage from the wall outlet (mains) to a different, usually a lower voltage. If it is used to produce DC a rectifier circuit is employed either as a single chip, an array-of diodes sometimes called Bridge Rectifier, both for forward rectification or a single diode yielding a half wave (pulsating) output. Filter is also used to remove the pulsating output of rectifier and voltage regulator is used to regulate the power supply.

Finally, depending on the requirements of the load, a linear regulator may be used to reduce the ripple sometimes also allowing for adjustment of the output to the desired but lower voltage. In the simplest case a single diode is connected directly to the mains and uses a resistor in series with a more or less fixed load to recharge a battery.

Switched-Mode Power Supply

A switched-mode power supply (SMPS) works on a different principle, consuming only as much power as is needed for the load. AC mains input is directly rectified without the use of a transformer, to obtain a DC voltage. This voltage is then sliced into small pieces by a high-speed electronic switch. The size these slices grows larger as power output requirements increase.

The input power slicing occurs at a very high speed (typically 10 KHz - 1 MHz). High frequency and high voltages in this first stage permit much smaller isolation transformers than are in a linear power supply. After the transformer secondary, the AC is again rectified to DC. To keep output voltage constant, the power supplies needs a sophisticated feedback controller to monitor current draw by the load.