Introduction: Power Supply Information

By Alec Manzardo

The power supply is one of the most important components of a computer. It is needed to convert the AC current from the wall socket to the DC current used by the other components of the computer. Alternating current (AC) is a type of electricity in which the electrons switch directions while transmitting. It is used for transmitting larger amounts of electricity over long distances, and it is the type of electricity that comes out of a wall socket. Direct current (DC) is needed to power electronic systems such as the components inside of a computer.

There are three different types of power supplies, unregulated, linear regulated, and switching.

In unregulated power supplies, there are a lot of AC properties such as ripple voltage (rapid electrical instability) carrying over to the DC power where it is not needed, but it is a cheap and efficient option for a power supply. Ripple voltage can be a problem because it causes the voltage to be inconsistent, like AC electricity, when the hardware that the power supply powers requires a consistent DC charge, so the device doesn't receive the intended type of voltage, which can possibly shorten the lifetime of some parts.

A linear regulated power supply is just like an unregulated one except for a transistor circuit that that operates in linear mode. The linear regulator outputs a fixed voltage for a wide range of inputs, effectively getting rid of excess voltage from the input. The problem with linear regulated power supplies is that all the excess voltage that is dropped results in a dissipation of heat, causing the power supply to require large heat sinks which ultimately make them expensive and inefficient.

The third type of power supply is switching. It operates by converting incoming AC current into DC, reconverting it into high frequency AC, using a transformer to step the voltage up or down, and finally turning the charge back into DC and filtering for final output. There are many advantages to using switching power supplies, such as being universal (able to power other electric power systems), light weight, and highly efficient. There are some disadvantages however, as they are very complex, can still have ripple voltage in their outputs (in cheaper models), and are expensive.

Step 1: Parts of a Power Supply

Transformer: Static device that transfers electrical energy without affecting the frequency. First step of converting AC power from wall socket to DC power needed for device. Used to step up or step down the AC voltage to a uniform charge, while isolating it from the AC power source.

Rectifier: Device used to convert AC power coming from transformer into pulsating DC. Utilizes a unidirectional device called a diode to rectify the charge in a forward direction.

Filter: Comes after rectifier and is used to prevent the ripple component of the voltage from appearing in the output. The DC coming from the rectifier is pulsating and is not suitable for the components of a computer, so the filter converts it to a smooth DC current.

Voltage Regulator: Final piece which is used to ensure that the DC output is well-regulated and steady. The device keeps the output voltage constant no matter what the input is, making sure the parts receiving the power work properly.

Step 2: Proper Maintenance and Care

The power supply is a device that does not require much upkeep, as the average user has no need to mess with its parts, therefore the only components that one has to maneuver are the cables and the casing. The most important part of caring for a power supply is making sure it is clean and dust free. The best way to clean out dust is to use an aerosol air duster. It is important not to blow air into the power supply from the outside because when it is turned back on all of the dust will get sucked back in. To properly clean the dust from the power supply, first unplug it from the computer tower. Next remove the side and lay it on its side so that the exposed part is facing you. Finally, spray the concentrated air at the fan, which will effectively force the dust out.

It is essential that your power supply provides enough power for every component, and you can check this by using an online power supply calculator. The calculator uses the model of your power supply and references it with the models of your other components to check if it is providing enough power to function properly. Cooler Master offers a relatively user friendly power supply calculator at .

Step 3: How to Troubleshoot the Power Supply

When a power supply unit is not working, it becomes pretty obvious, as some or all components of the computer will not function at all due to a lack of power. When not working properly, power supplies will either not provide power to any components, or will provide incorrect voltage, causing some parts to not function. Power surges can also occur, possibly causing pins of certain parts to bend or even causing some pieces to partially burn.

The most common reason that power supplies provide incorrect voltage is that the voltage selector switch on the back is switched to the incorrect standard. In the United States, the standard that components use is 110V, while most of Europe uses 220V, and if the wrong side is selected some components will not function because they won't receive the required amount of power. The solution to the problem is a simple flip of the switch.

If the correct voltage is selected and the computer still is not receiving power, it is most likely a problem with the connection of the power supply. You can tell if the power supply is not connected/working properly if the system does not start to turn on when the power button is pressed and if the power LED on the motherboard is not illuminated. It is easiest to first check the outlet and the cord being used. Plug another electronic device into the outlet to make sure that it works and check the cord for any bent or missing prongs. If neither the cord or the outlet are the problem, it may be a connection inside the computer. The motherboard provides power to most components, and it gets its power from the ATX power connector, a 20 or 24 pin connector that supplies power. If that is disconnected than nothing connected to the motherboard would receive power and it wouldn't work.

It is best to always keep your power supply clean so that no internal parts get damaged. One tool that is useful for testing the power supply and the ATX connector is a digital multi meter. It is a tool that is used to test the voltage coming out of certain pins that are connected to the power supply. A digital multi meter consists of a negative probe, a positive probe, and a device/screen that displays the voltage. I have included a picture that can be used to reference the correct voltage for each pin of an ATX power connector.

Step 4: Using a Power Supply Calculator (Video)