Without power, our computers aren’t very useful. In this video, you’ll learn about computer power supplies, power specifications, redundant power supplies, and power supply efficiency ratings.
Before we get into this presentation on power, I want to give you a very strong warning to always, always disconnect from any power source if you’re ever going to work on the inside of any computer. Not only is there a concern about electrocution from that direct power source, but there may be components within your computer that are storing power in capacitors. You have to be sure that you know exactly what you’re touching inside of that computer, and you have to be knowledgeable enough to know how to discharge those capacitors before you work with that equipment.
Another common mistake that I see people make is connecting themselves to the electrical system of the building. You never want to connect yourself or anyone to any part of a building’s electrical system, even if it’s the ground wire. The ground wire of a building could be energized at any time. So you want to be sure that you do not connect yourself to any part of that system.
Our goal when working with this type of equipment that uses electricity is to always have a healthy respect for anything dealing with power. And if you have a system that you’re going to be working with, you should always double check and make sure that you have disconnected yourself from the main power source.
If you look inside of a desktop computer, you will find a relatively large power supply. This power supply is providing your computer with DC power, or Direct Current. That’s because your motherboard and all of the components on your motherboard need DC power to operate. But the type of power that we get from our wall outlet is AC power, or Alternating Current. That’s why we need to convert from AC to DC that your motherboard will use. And this power supply is the device that provides that conversion.
These power supplies are designed to convert 120 of AC or 240 of AC to DC power. Specifically, separate DC voltages of 3.3 volts, 5 volts, and 12 volts. This is probably one of the most important components in your system because everything inside your computer relies on the power that’s being provided by this power supply.
You’ll see many different terms associated with power inside of a computer. One of those terms is an ampere. You may see this abbreviated as an amp, or abbreviated as a capital A. This describes the number of electrons that are moving past a single point in one second.
Often, we’ll compare electricity flowing through a wire to water that is flowing through a hose. You can think of amps as that total amount of water flowing through the hose. So if you can increase the size of the diameter of that hose, you can increase the number of amps.
Another term you’ll see used is voltage. It’s often abbreviated as volt or the capital letter V. You can think of this as the pressure of electricity on a particular wire. And in the case of a hose, it would be the pressure of water that’s flowing through that hose. If you want to increase the amount of voltage, then you need to increase that pressure, very similar to increasing the amount of water that might pass through a hose.
If you know the voltage and you know the number of amps, you can calculate the wattage. This is often described as a watt or a capital W. And we think of this as a measurement of real power use.
This is a relatively easy calculation. We simply take the number of volts. We multiply that by the number of amps, and the resulting value is the total number of watts. So if you’re working inside the United States with 120 volts, and the device is using half of an amp, then the total amount of real power use would be 60 watts.
If you look at the details of a power supply, you’ll see specifications for AC power and specifications for DC power. As we’ve mentioned earlier, AC is Alternating Current, and it is referring to current that is constantly reversing direction. You’ll often see this shown as a wave or a curvy line to designate alternating current.
So alternating current is what we use to get power from our power plants to the outlets that are in our homes and in our businesses. We often describe this alternating current as the number of volts and how much this is alternating in a single second, and that is referenced in hertz.
In the United States and Canada, we have 110 to 120 volts of alternating current. You’ll sometimes see this abbreviated as VAC for Volts of AC, and that is running at a 60 hertz rate. Hertz is often abbreviated with an Hz. If you’re in Europe, you’re probably running 220 to 240 of alternating current, and it runs at a rate of 50 hertz.
Our alternating current is the input to our power supply. And, of course, our power supply is outputting Direct Current, or DC. You’ll often see DC shown with the graphic of a single line and multiple lines underneath. Direct current, as the name implies, is power that is moving in a single direction with a constant voltage.
So the power source that we’re connecting our computers to will be different depending on where you are in the world. As we mentioned in the US and Canada, we’ll see 120 of AC running at 60 hertz, and Europe is 230 at 50 hertz. That means that if we are moving a computer from one place to the other, we need to be sure that we are connecting a power supply that can use the type of input that is used in that country.
If you were to look at the back of a relatively old power supply, you might even see a manual switch in the back where you tell the power supply what you’re connecting to. And that switch is usually marked with 120 volts and 230 volts. If you’re not sure what type of power is coming out of the outlet that you’re connecting to, you might want to grab a multimeter and test that outlet to see what type of alternating current is on the other side.
If you look at the back of your computer, you might notice that it doesn’t have a switch to manually move between 120 volts and 230 volts. That’s because most modern power supplies will recognize the type of power they’re connecting to and will adjust accordingly to work properly, regardless of where you happen to be in the world.
If you do have one of these manual power supplies, you want to be very careful of how you’re configuring that switch on the back. You don’t want to take a power supply that is currently set for 120 volts and plug it in to a 230 volt power source. If you plug in a power supply with those settings, then you’ll probably quickly find the power supply will be overloaded, and it will most likely be a spectacular failure.
Here’s a better view of this manual switch on the back of one of these older power supplies. If you are planning to connect this device for the first time, you may want to reference that setting to see what it’s configured for on that power supply and make any change that you need before connecting it to the power source. Once the system is configured to the proper voltage and it’s connected to the power source, you can leave that switch exactly where it is.
So now that we’ve talked about the input to the power supply, let’s talk a little bit about the output from the power supply. That is going to provide us with a number of different voltages in DC, or Direct Current. You often see these DC values referenced as a positive value and a negative value. In reality, it’s referring to the difference in potential based on where you happen to be.
You can think of this as measuring the heights of your home from your front door. If you wanted to measure the second floor of your house, it would be approximately positive 10 feet above you. And if you were measuring the basement, it would be negative 10 feet. Both of those are 10 feet away, but obviously, the distance is relative to where you happen to be standing.
If you look at your power supply documentation, you’ll see there are a number of different outputs that are available from the back of that power supply. One of those is probably a positive 12 volt. This is for PCI express adapters, hard drives that you might install into a system or anything else that needs that much voltage to be able to operate.
You may find some motherboards that use plus 5 volts for components that are on the motherboard itself. Although many of our newer motherboards tend to use plus 3.3 volts. That 3.3 volt power is primarily used for the motherboard to power up the M.2 slots, the RAM that’s on your system, and the other assorted components on the motherboard.
And you might also find that your power supply provides plus 5 volts of SB power. This is the power provided to the motherboard when it’s in a standby or sleeping state, so that we can wake it up using signals across the network, or by pushing a button on the front of the case.
You may find some mother boards using negative 12 volt of DC power. This is often used for integrated local area network connections on the motherboard. And there may be some older PCI cards that use the negative 12 volts.
And for older power supplies that are providing power for legacy motherboards, you might see them providing a negative 5 volts. This is for an older style of adapter card that’s no longer used. And you may find that your power supply doesn’t even provide an output for negative 5 volts.
If you’re not sure the type of output and how many amps are supported for each of these voltages, all of this is documented in your power supplies manual. You might also see those values right on the side of your power supply for easy reference.
To get power to our motherboard, we have a main power connection that is a 24-pin connector on the motherboard itself, and it provides the motherboard with 3.3 volts, 5 volts, and 12 volts of DC power. This was originally a 20 pin connector, but most modern motherboards are using the full size 24 pin connector to connect the power supply to the motherboard.
If you do run into one of these older motherboards that only has a 20 pin connector on the motherboard, you can still use the 24 pin power connector from the power supply and simply not use those last four pins that are on the connector.
Here’s the 24 pin connector you’ll find on a motherboard, and it is probably one of the larger connectors that you’ll find on the motherboard itself. To be able to connect the power from the power supply, we simply take the 24 pin connector that is coming from the power supply and place it into those slots on the motherboard. This can only fit into this connector one way because this entire connection is keyed, which prevents us from plugging it in with the wrong orientation.
If you’re working with servers and other infrastructure devices, you may find that there are multiple power supplies on the back of the unit. These are designed to be redundant. Each power supply is designed to support the full 100% power required by the system. So if you lose one of those power supplies, the other power supply can continue to keep that system up and running.
Very commonly, these two power supplies will run at 50% of the load. And if you lose one of those power supplies or it comes disconnected from the power source, the other power supply will take 100% of that load.
These are also designed to be hot swappable. You can see there’s a switch on top of this motherboard that allows you to slide it out of the chassis, even when the system is up and running. This means that you can maintain 100% uptime, but be able to replace any of these power supplies if you run into a problem.
Many less expensive power supplies will have fixed connections coming out of the power supply itself. This means we’ll have a large grouping of cables that will be sitting inside of our computer case, whether we’re plugging a device into those connections or not.
Higher in power supplies tend to be more modular, where you can simply connect only the cables that you need to use inside of that particular system. And if you need to add more later, you can simply plug them into that modular connection. And if you need to remove a device from your computer, you can remove those cables from the inside of your case.
Here’s a hybrid power supply that has some fixed connectors, but it also has modular connectors that you can plug in if you need them. Here’s a power supply that is completely modular. You can see that they provide all of the cables that you would need to connect. And you can simply plug in the cables that you need to provide power for your specific requirements.
If you’re purchasing a power supply, you’ll notice there are different models that will support a different number of watts. Generally, if you’re getting a power supply that supports a higher wattage, that power supply tends to be more expensive. You could certainly spend the extra money to buy a power supply that gives you much more capacity than you’ll ever need, but that doesn’t provide you with any additional speed benefit for your computer.
Even though different power supplies may support different wattages, the physical size of the power supply doesn’t tend to change. So if you’re upgrading a power supply inside of a computer case, you might upgrade to a higher wattage. But the size of the power supply itself will be exactly the same inside of that case.
If you’re trying to decide just how many watts you need in a power supply, then you’ll need to calculate all of the different components inside of your computer and add up what the maximum number of watts might be required for all of those systems to work together. So you’ll want to check your documentation to see what the CPU requires for wattage, what your storage devices will need, what your video adapter requires, and then any other components inside of that system.
If you have a separate video card inside of your computer, these usually require a significant amount of power. And you’ll want to check the documentation for that video card to see what the requirements are for power inside of that computer. A good rule of thumb is to get a power supply that can support 50% of your total load today. That means that the power supply will not be overloaded, and you’ll have plenty of room for growth in the future.
Another useful specification when you’re looking to purchase a power supply is the energy efficiency. When we’re converting from alternating current to direct current, we lose a bit of power each time we make that conversion. That lost power is converted to heat, which, of course, creates more of a cooling issue for the computer that you’re using.
If you’re concerned about this efficiency rating, you may want to check the different values associated with those power supplies. The standards tend to be somewhere between 80% to 96% efficiency, depending on the quality of the power supply that you’re purchasing. If you get a power supply that’s more efficient, then you’ll have less power that is lost during that conversion process. And because you’re losing less power, you have a lot less heat in your system. And overall, you’re saving money not only empowering the computer, but keeping that computer cool.
There’s a certification program that power supplies can go through to determine their efficiency. You’ll see power supplies rated as an 80 plus, an 80 plus bronze, silver, gold, platinum, or titanium. This means that the 80 plus with no rating would be the least efficient, and an 80 plus titanium would be the most efficient.