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In this lesson, we're going to talk about power supply units,

also known as PSUs.

Now, every computer

is going to have some sort of power supply unit.

This is because power supplies

are going to give all the computer systems and components

the direct current they need to be able to operate.

Now in all of our homes,

when you plug something into the wall outlet,

you're actually getting voltage

in what's known as AC or alternating current.

In America, this is 110 volts to 120 volts AC.

And over in Europe and Asia,

you're usually going to see this as around 230 to 240 volts AC.

But our computers need a much lower voltage

and they need a direct current voltage.

Alternating current actually cycles

between positives and negatives repeatedly.

For instance, in the United States we use 60 Hertz power,

which means 60 times per second,

our voltage is going from 120 positive to 120 negative

and back again.

So, our computers have to take that cycling voltage

and turn it into something they can understand

which is a direct current,

which means it's always going to be at a certain voltage.

For example, if you have a double-A battery,

that's 1.5 volts DC.

That means on one end of the battery,

there is always going to be a positive 1.5 volts.

And as you move from one side of the battery to the other

as you're going through the circuit,

you're going to keep that direct current

or that flow of voltage at 1.5 volts the entire time.

So when you think about a power supply,

remember its main purpose

is to deliver direct current or DC low voltage power

to all the different components inside of your PC

when it receives an alternating current or AC power

from your wall outlet.

Now when you look at a power supply,

they tend to be a fairly large size unit.

Even in smaller and less powerful office computers,

your power supply

is going to be about the size of your fist.

Whereas when you start using gaming PCs

or more powerful workstations that require more power,

you're going to have a larger power supply unit

that is two, three, or four times as large as that.

Now inside this power supply unit,

it needs to do the conversion from AC to DC.

And to do that, it's going to use a transformer

and a series of regulators and filters.

The transformer is going to do the large power drop for us,

going from that 110 or 120 volt AC inside the US

or that 230 or 240 volts AC over in Europe and Asia

into voltages that are at current at 12 volts or less.

Once the transformer part gets it down to a lower voltage,

it will then pass through filters and regulators

to get to the right levels of DC

that are needed by your various components.

So remember when it comes to your computer,

it needs good clean power from the outlet

to the computer's power supply.

And then that power supply is going to convert that AC

or alternating current input

into a DC or direct current output

for all the various subsystems of your computer,

at those necessary voltages.

Your power supply is going to create a lot of heat

when it does this,

and so you're also going to have a fan inside your power supply

to draw air over the transformer

and be able to expel that heat

out the back of that power supply.

This will help

keep the transformer inside the power supply cool

and allow it to work at optimal efficiency.

To install a power supply,

you're simply going to find the location in your case

that will support it.

And generally,

it's going to be inserted using four different screws,

one on each corner of the power supply,

with the power supply plug

hanging out the backside of the case,

and having multiple different connectors

on the inside of the case that can then connect

to your different components from your power supply.

Older power supplies would use cables

that were actually soldered directly into the power supply,

and you'd have all the different connector types

that you might need,

and you'd plug them into your various components.

Some of the new modern power supply units though,

use a form factor that's known as modular PSU

or modular power supply units.

These modular power supply units

allow you to unhook the connectors

and detach them from the unit.

So if you don't need all 15 connectors,

you can unplug the ones you don't need,

and therefore there are less cables inside of your case

connected to your power supply.

This can help improve the airflow and cooling

inside of your case because there's less cables in the way,

and it just clears out a lot of the mess

inside of your computer case.

Now other than that, when you're using a power supply,

it really doesn't matter if it's a modular power supply

or a regular traditional power supply.

Either of these power supply units

are going to operate the same.

The only real difference

is that if you're using a modular power supply,

you can disconnect any of the unneeded cables

to free up space inside of your computer.

Now the last thing we need to talk about

when it comes to power supplies

is the fact that some systems

will actually have more than one power supply.

For example, if you're using a workstation or server

that is critical to your business operations,

you may want to select a motherboard

that supports a redundant power supply configuration.

This will allow you to install two power supply units

into that particular machine,

and then connect dual power to that motherboard.

This way, if one of those power supply units fails,

the other one can continue to carry the load

and keep that machine up and running.

Now for this to work,

you have to have a motherboard that supports it.

And on these type of systems

that support redundant power supplies,

you're going to be able to have those power supplies

plug into a backplane,

and this backplane will then switch between the two sources

as needed to power that particular motherboard.

This means that if one of those power supplies fails,

you can actually replace it

without shutting down that system.

And this will allow you to keep your operations up

and running the entire time because you're dealing

with some kind of a mission critical system in this case,

which is why you bought

a redundant power supply capable motherboard

in the first place.

Now most of us in a regular office environment though

aren't going to be using redundant power supplies.

Instead, each of our cases will have a single power supply

connected directly to our motherboard

to provide power to all of its components,

as well as having additional cables

attached to that power supply

that are connected to things like our processor socket,

our hard drives, and our external graphics cards

if they need additional power.