What is a PSU?
PSU. Power Supply Unit. A Cube/Cuboid shaped transformer mounted inside your case, towards the rear. Electricity supplied to your home is AC (Alternating Current). This is no good for a computer and as a result a transformer is used to convert Alternating Current to Direct Current. The Voltage is also stepped down from 110V/240V to split Voltage rails inside the computer of +3.3V, +5V, +12V, which in turn power certain components within the system. Without any argument it's the heart
of a Computer.
Some data you need to understand.
- Energy transferred per unit time. Power Supplies are advertised by the amount of Power it can deliver to the components. Units in Watts (W)
- Energy transferred per charge carrier. You may need to understand the importance of the 3.3V, 5V and 12V rails.
- The flow of electricity to components. Units in Amperes (A)
- ((Power Drawn From Mains) / (Power Effectively Used)) * 100%
where > 75% is ideal.
Anyway, that's more than enough background information for now. Lets move on.
What Determines a good PSU?
In short. One that's less susceptible to failure. Let's expand on that. What are the traits of a PSU that's susceptible to failure?
- Low Quality Internal Components. Difficult to judge as a consumer but sub $40/£30 price tag should ring alarm bells.
- Low Efficiency. This is infact a consequence of the above factor. The Conservation of Energy Law states that within a closed system, Energy (Power) cannot be created nor destroyed but are transferred in different forms. No Transformer can be 100% efficient. Inevitably, while some energy is transferred effectively as Electric Energy, some is transferred as heat or possibly sound. The latter two forms of energy transfer is effectively wasted or useless. A good PSU will waste less energy while a poor PSU will waste more energy. A PSU with a poor efficiency will always have to work harder to deliver the same power to the system components and this in turn can lead to failure.
A given system required 400W under load to function. We'll use a hypothetical PSU with a 80% efficiency and another with a 65% efficiency.
The first PSU needs to draw 400 / 0.8 = 500W
from the Power Socket/Mains.
The second PSU needs to draw 400 / 0.65 = 615W
from the Power Socket/Mains.
This in turn actually makes your system more expensive to run in terms of Electricity Bills.
The above are factors that make PSU's more susceptible to failure.
What Happens When A PSU Fails
Sometimes a PSU shows symptoms of imminent failure. This may include system lockups, unexpected system restarts but also unexpected shut downs. More than often this occurs when the system is fully loaded, running a game or other intensive application. Eventually this can also happen when a system is just idling as a PSU continues to deteriorate. On the other hand, PSU failures can be imminent as well. In short, when PSU's fail there is a risk of it producing a surge effect that can damage or destroy other components within the system. Quite often the Motherboard is the first victim, followed by CPU, RAM and Disk Drives. This tends not to happen with well built PSU's.
Trusted PSU Vendor List
My honest advice would be not to choose any brands other than the ones mentioned below. There may be some brands that I've missed out but you cannot go wrong with this selection.
Fortron Source (FSP Group)
PC Power & Cooling
Thermaltake (Toughpower Range Only)
MUST Avoid List
Hiper (Early Batches)
Finally a list of PSU Brands and Models that are 80 PLUS certified