3.14.1 Power Supplies.txt

Power Supplies Computers need electricity to function. Without it a computer is nothing more than a really expensive paperweight. In this lesson, we’re going to look at the hardware component responsible for powering a computer, the power supply. Back Panel 0:17-1:11 This is a typical ATX power supp...

Power Supplies Computers need electricity to function. Without it a computer is nothing more than a really expensive paperweight. In this lesson, we’re going to look at the hardware component responsible for powering a computer, the power supply. Back Panel 0:17-1:11 This is a typical ATX power supply. The ATX tells us that the power supply adheres to the ATX form factor specifications. Right now, we’re looking at the back panel of the power supply. This is the part of the power supply that’s exposed when it’s installed in the computer case. Here you’ll typically see a power switch like this one that turns the power supply on and off. You might also see a voltage selector switch. It’s used to toggle the input voltage between 115 or 230 volts, depending on which is being used. Some power supplies are able to automatically switch between voltages, eliminating the need for the switch. These types of power supplies specify a voltage range that they are compatible with, which is usually between 100 volts and 240 volts. Most power supplies also have air holes on the back. Some models have a fan here instead of on the top. AC Power to DC Power 1:12-1:51 On the back panel of all power supplies is a C14 connector. This is where the power cord from the wall plugs into. Now, the electricity that comes in here from the power cord is 120 volt AC power. However, the components inside a computer use DC power. This means the AC power from the outlet need to be converted to DC power. This is one of the main functions of a power supply. The 120 volt AC power from the wall flows into the power supply where it’s converted into three DC voltage levels, 12 volts, 5 volts, and 3.3 volts. This is because different components have different voltage requirements. Wire Bundle & Connectors 1:52-2:20 The converted DC power flows out the power supply’s wire bundle which is on the opposite side of the power supply here. The power supply’s wire bundle contains a variety of wired connectors that plug into components and provide them with the correct voltage of DC power. Now, it’s important to know that the number of components a power supply can handle isn’t based on the number of its connectors. For example, a power supply could have 10 hard drive connectors but this doesn’t mean it can power 10 hard drives. Watts 2:21-3:10 Instead, power supplies use a power rating called watts, which is a measurement of its maximum power output. Now, for most desktop computers a 350 watt power supply should be sufficient. However, when you start adding hard drives, optical drives, and high end video cards, your power needs increase substantially. As such, it’s usually best to invest in a more powerful one such as a 500 or 650 watt power supply. If necessary, you can identify your exact power needs by adding up the wattage requirements for each component you need to power. There are also several websites you can use to calculate specific power needs. Remember, one of the power supply’s main functions is to provide power to components, but if the connected components draw more power than the power supply can handle, they will shut off. Thermal Management 3:11-3:44 Another part of the power supply is its fan. Most ATX power supplies will have a large fan on it that helps to cool the unit, however, this fan serves a secondary purpose. When installed in a case, a power supply’s fan aids in thermal management. Power supplies are typically installed in the back, top of a computer case, directly above the CPU. This positioning allows the power supply’s fan to pull hot air out of the computer case allowing cooler air from the front of the case to flow in. This helps to maximize cooling by creating a wind tunnel effect inside the case. Summary 3:45-4:03 Those are the basics of computer power supplies. Remember, power supplies have two primary functions. First, they convert AC power to DC power and second, they provide 12, 5, and 3.3 volts of DC power to components. Power supplies also provide a secondary function which is to aid in thermal management.