Classification Power Supplies, Types and Characteristics

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Classify power supplies types and characteristics

AC adapter

Most portable computers have power supplies that provide 25 to 100 watts. In portable computers (such as laptops) there is usually an external power supply which converts AC power to one DC voltage, and further DC-DC conversion occurs within the laptop to supply the various DC voltages required by the other components of the portable computer.

ATX

Today, PCs will use either an ATX or ATX12V power supply. It contains software control of the power on/off signal so that it can shut down the system.

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Since the ATX/ATX12V power supplies are software activated/deactivated, you need to connect the Power SW cable from the chassis to the motherboard. Most power supplies require to have a load connected to the power supply. In other words, you must have at least one component such as a drive or motherboard connected to the power supply.

Most power supplies designed to be used in the United States operate at 120 volts with a frequency of 60 Hz.

In other nations, the supply voltage and frequency may be different. In Europe, you will find 230 volt with a 50 Hz frequency as the standard. Today, most PC power supplies will operate at either voltage. Some can automatically switch over to the proper voltage while most are done by using a small switch on the rear of the power supply. Ensure when plugging in your PC and turning it on, the correct voltage is selected. If you have a power supply switched over to 230 V and the voltage is 120 V, the PC will not boot up.

Unfortunately, if the power supply is set to 120 V and it is connected to a 230 V outlet, it will seriously damage your power supply and other important components.

The ATX12V power supply provides increased 12 V, 3.3 V, and 5 V current and provides additional cooling capability. An ATX12V power supply can be easily identified by the addition of an additional new 2x2 pin connector and an optional 1X6 pin connector.

The ATX power supply uses the PS_ON signal to power up the system. A +5 volt signal is constantly sent through pin 14 (PS_ON) of the ATX power connector. When the PS_ON is shorted tells the power supply to turn on and start the boot process. A push button contact switch is connected to two pins on the motherboard that link to the PS_ON signal to ground. When the push button is pushed, it connects the PS_ON signal to ground. When the push button is pushed, it connects the PS_ON signal with ground, shorting it out. Therefore, when you are installing an ATX motherboard, you need to connect the push button wires (usually labeled PWR SW) to the motherboard. If you decide to test a motherboard without physically installing it into an ATX case, you can start the system by either connecting a push button switch to the motherboard and pressing the button or by taking a small screw driver and make contact with the two pins that make up the power switch connector. Since the switch only toggles the on/off status, the switch carries only +5 V of DC power, rather than the full 110 V AC current used in the T power supplies.

Besides supplying the power to the PC components, the power supply also provides the power-good signal. During boot up, the processor tells the computer to constantly reset. As soon as the power supply performs a self-test, testing if all voltage and current levels are acceptable, the power supply will send a power good signal (+5 volts) to the microprocessor. When the power good signal is sent, the computer will finish the boot process.

Voltage, wattage and capacity

Computer power supplies are rated based on their maximum output power. Typical power ranges are from 300 W to 500 W lower than 300 W for Small form factor systems and are intended for ordinary home computers, the use of which is limited to Internet-surfing and burning and playing DVDs. Power supplies used by gamers and enthusiasts mostly range from 450 W to 1400 W. Typical gaming PCs feature power supplies in the range of 500-800 W, with higher-end PCs demanding 800-1400 W supplies. The power rating of a PC power supply is not officially certified and is self-claimed by each manufacturer.

Computer power supplies are generally about 7075% efficient. That means in order for a 75% efficient power supply to produce 75 W of DC output it would require 100 W of AC input and dissipate the remaining 25 W in heat. Higher-quality power supplies can be over 80% efficient; higher energy efficient PSU's waste less energy in heat, and requires less airflow to cool, and as a result will be quieter. As of 2007, 93%-efficient power supplies are available.

Voltage selector switch

Some power supplies have a switch to change between 230 V and 115 V. Other models have automatic sensors that switch input voltage automatically, or are able to accept any voltage between those limits.

Pins (20, 24)

The ATX form factor has five main power supply designs:

“ATX - 20 pin connector (Used through Pentium III and early Athlon XP)

WTX - 24 pin connector (Pentium II and III, Xeon and Athlon MP)

AMD GES - 24 pin main connector, 8 pin secondary connector (some dual-processor Athlon)

ATX12V - 20 pin main connector, 4 pin secondary connector, 8 pin tertiary connector (Pentium 4 and mid/late Athlon XP & Athlon 64)

EPS12V - 24 pin main connector, 8 pin secondary connector, optional 4 pin tertiary connector (Xeon and Opteron) defined in SSI specification

ATX12V 2.0 - 24 pin main connector, 4 pin secondary connector (Pentium 4, Core 2 Duo, and Athlon 64 with PCI Express)

ATX12V 2.2 - One 20/24-pin connector, one ATX12V 4 pin connector. Many power supply manufacturers include a 4 plus 4 pin, or 8 to 4 pin secondary connector instead, which can also be used as the secondary EPS12V connector.”