How Much Voltage Is Required for a Computer

Three types of DC voltage are required for a computer to run. 12 volts (V) are used in the feeding of the motherboard and new-age graphics cards, 3.3V is used for the processor and 5V is used for the chassis and USB ports or CPU fan. Power...

Author: Delilah Daut
Category: Hardware

Have you ever wondered what really happens inside your computer power supply? A power supply is the most vital component when it comes to the operation of a computer. Without a power supply, a computer is just a random box full of metallic and plastic components. Since the beginning of the first computer, a power supply has been used to feed all the electronic devices inside it. 

And believe it or not, there is no magic behind this. Alternating current (AC) voltage is drawn by a power supply from an electric source and converts it to direct current (DC) voltage. Several components assist the computer power supply: capacitors, coils, a fan for cooling down the whole unit, and an electronic circuit board that will regulate the current. Apart from these, the circuit board should have several cables fed into it with wire sets of distinguishable colors. These wires transmit different voltages to other devices connected to it, plus the mainboard. 

Today, several safety circuits are equipped to modern power supplies that check the flowing current continuously. If an extreme condition that may exceed its power output capacity is detected, the power supply will prevent any further harm to the motherboard and itself by shutting itself down.

How Much Voltage Is Required for a Computer

Computers and Voltages

The power supply of a personal computer is a metal box that can usually be found in the corner of the case. It is usually visible from the back of many systems because it contains the cooling fan and the power cord receptacle. Three types of DC voltage are required for a computer to run. 12 volts (V) are used in the feeding of the motherboard and new-age graphics cards, 3.3V is used for the processor and 5V is used for the chassis and USB ports or CPU fan. Power supplies use switcher technology for the conversion of alternating current to lower direct current. 

Converted electricity is forwarded through dedicated cables from the electronic circuit board in the power supply to feed the devices that are inside the computer. With the help of these components, AC voltage is converted into a clean direct current. The capacitors located inside do nearly half of the work that is done by the power supply. These capacitors are responsible for the regulation of clean and smooth currents to precious computer circuits.

You should be warned that even if your computer has been unplugged, there is still a chance of electricity being present inside your power supply unit. This applies even days after you’ve pulled out the plug. That is the work of the capacitors: to store energy that can be used to achieve a continuous workflow.

A power supply's main specification is in watts. A watt is the product of the current in amperes or amps, and the voltage in volts. If your PC experience is a bit old, you might remember that the original PCs had toggle switches that were large and red and relatively heavy. These switches controlled 120V of power flowing to the power supply. 

Today, a little push button turns on the power and then a menu option is used to turn the machine off. Standard power supplies were able to get this upgrade in feature several years ago. The power supply can receive a signal from the operating system telling it to turn off. A 5-volt signal is sent by the push button to the power supply telling it when to turn on. A circuit that supplies 5V is contained in the power supply called the ‘standby voltage' which allows the push button to work even when it is officially ‘off'. 

Power supplies tended to be bulky and heavy prior to the 1980s. Huge capacitors (soda can large), large and heavy transformers were used to convert line voltage at 120Vs and 60 Hertz (Hz) into 5V and 12V DC. Today, the switching power supplies that are used are much lighter and smaller and can convert 60 Hz to a higher frequency, which translates to more cycles per second. A small, lightweight transformer located in the power supply is enabled by the conversion to do the voltage step-down from 110V (or 220 depending on the region) to the voltage that is required by a computer component. 

Wire Color Coding

Do you know about power supply unit color codes? You are bound to see a bunch of colored cable sets protruding out with different connectors or sockets and different numbers of wires inside a power supply. The black wires are used as a ground for the current. You are advised to pair every other color of wire with a black wire. The yellow wires and the blue wires denote +12V and -12V respectively. The red wires and the white wires denote +5V and -5V respectively. The orange wire denotes 3.3V and the purple wire denotes +5V when it is on standby mode.

How Much Voltage Is Required for a ComputerHow Much Voltage Is Required for a Computer

How Do You Check Power Supply Voltages?

Now that we are familiar with colored wires and their voltages, you may wonder if these voltage feeds can be measured by a consumer to ensure that they are delivering enough voltage. This is where a voltmeter (also called a multimeter) comes in. To check voltage, turn the multimeter on and switch it to a DC voltage range. Preferably, using a limit of less than 20V, create a connection between multimeter cables into their proper sockets keeping in mind that wire is always used for grounding. Now, simply touch any sockets with the cable needles of the multimeter. Before making a measurement, you need to check the multimeter manual. You also need to power on your computer.

Misconfigurations may lead to unwanted results. While doing such a test, you must be very careful. Checking the bigger plug of your power supply should be the easiest way to make a measurement. Attach the black cables to black and attach the other cables to either the yellow or red cables since you have bigger holes to plug your multimeter needles into.  You should never connect the cables of your own multimeter to yellow and red cables at the same time. This might lead to a short circuit that may cause harm to your motherboard. 

Checking the power supply voltage is not the easiest thing in your to-do list. However, interested users may decide to do it in order to confirm if their power supply is working properly or not. Using too many long valves may affect voltage delivery since low voltage currents should be considered. This is what normally happens when you use a two-meter long USB cable to plug your pen drive. Voltage loss throughout the long cable may reduce the work efficiency of your external storage unit or pen drive that is drawing its energy from the USB port.

Laptops also have a power supply. Every electronic device requires some source of energy to operate. The power supply for your portable computer is the cable plus adapter duo used to charge it. The adapter converts AC voltage to DC voltage and feeds either the battery or the power control card of your portable computer.


Having a power supply is very vital in the operation of a computer. A computer power supply has different rail voltages: +3.3V, +5V and +/-12V. A power supply consists of different components such as the fan, the capacitors, the circuit board, and the coils. The modern ones have several safety circuits that check flowing current and shuts itself down if the excessive power output is detected. A computer’s capacity to produce power in watts is what makes a computer power supply unique and capable of feeding the computer.