Written By:
Kia Javadi
We all
know that the power supply is an important unit who's proper
operation is essential to a working computer. But
what exactly is it that a power supply does?
What Does A Power Supply Do?
A power supply's job is to convert an Alternating Current
(AC) signal coming from
your wall outlet into a usable Direct Current (DC) signal. Simply
stated, this process is done by stepping down the input
voltage level with a transformer and then rectifying it to
convert to DC. Once the DC signal
is generated it is used to power all the devices and
components of your system. In order to distribute the signal
around to every component, many internal or external
splitters can be attached to satisfy the number of connected
devices. Usually a preset number of leads are provided
by manufacturers to make this splitting procedure simple or
even unneeded to the end user (as proper voltage values must
adhere to specifications). From there, voltage regulation (often in the way of
capacitors) is used to prevent your power supply from
outputting too much or too little power. This protective
mechanism is often called over current protection, over
voltage protection, or over power protection. It is
always important to ensure that your power supply has built-in regulation capabilities
or spikes / sags due to fluctuations from the supply could
damage your components. Alternatively, connecting your
power supply to an Uninterruptible Power Supply (UPS) unit
can greatly eliminate any potential harm due to external
conditions on the unit.
For computers
the power supply is most responsible for providing power to
the motherboard, your hard drive, CD drives, expansion
cards, etc. In most cases, a single PSU unit (as opposed to
a redundant power supply setup where multiple PSUs are
cascaded in case one fails) is responsible for
powering all parts internal to the system. Some external
devices such as keyboards, mice, and external drives may
also draw power either directly or indirectly from the power
supply. This makes the power supply a critical
component to the system. That's why when the power supply fails, your
system will no longer operate.
Cause?
A dead or
otherwise unworking power
supply unit must be replaced or repaired. Without power
your devices will not 'Turn ON' so you will experience
complete downtime on the system until corrected.
Beyond that, a dead or 'burned out' power
supply can also cause damage to other components connected
to your system. For this reason and others, it is never
recommended to test a questionable power supply by simply
plugging it into a system. Doing so can cause
irreversible damage to
your components and won't tell you for certain
whether or not the PSU is functioning properly. Testing
should always be performed with a power supply tester (such
as this ATX
Power Supply Tester). The process is as simple as plugging
the unit in and waiting for the tester to output the
values, but if you don't have a tester you will need to
acquire one.
What
Can Damage A Power Supply?
The number one
killer of power supplies is damage due to overheating and/or
being overdrawn.
Usually this can happen if the cooling device / cooling fan
attached to the power supply fails and the operating
temperature inside the unit becomes too hot. Another reason
could also be improper air circulation throughout your
case or dust that collects over time.
Alternatively,
by connecting too many components and exceeding the maximum
deliverable power capabilities of the unit, you can cause
damage as well. It is important to calculate the
maximum device drain of your components and ensure that your
PSU can deliver that to them. Usually it is also
recommended to have some room to spare as fluctuations and
future growth can change your numbers.
The formula for power calculation is:
Power = Current x Voltage
Watts = Amps x Volts
Don't be fooled into using this formula to
calculate the total output power of a power supply (based on
the maximum ratings on each rail). Rail outputs can be
thought of as a 'Give-and-Take' system. This means
that if you are operating at maximum on the +12V rail, don't
expect to be able to operate at maximum on the +3.3V rail.
The more current outputted at +12V, the less you will be
able to output at +3.3V, and so on. When manufacturers
specify a Maximum Power rating for each rail on the power
supply they are oftentimes submitting maximums reached
independent of this interaction. These values are also
achieved in lab environments so you will rarely see them in
practice. In most cases it is recommended to budget a
30% buffer between your system needs and the max rating of
the supply.
How Can I Tell
If My Power Supply Is Dead?
The easiest way
to determine whether or not a power supply is working is to
use a Power Supply tester. Some of
the more common characteristics of a dead power supply are:
1) system doesn't turn on when the power button is pressed;
2) high-pitched noises coming from the power supply when in
operation; 3) random resets - especially during or shortly
after booting up; 4) burnt smell coming from the power
supply unit itself; 5) loud 'pop' sound heard once prior to
system failure. Again, exercise caution and use a PSU
tester to determine if the unit is faulty or has gone bad.
