Choosing your next computer power supply

A quality power supply unit – or PSU – is far more important than many computer owners believe or care to think about. Feeding a modern computer – with powerful graphics card(s), multi-core CPU, fast memory chips and hard disks, and other power-hungry delicate electronics – with anything less than a quality power supply that can deliver stable, noise-free power at any load, under any condition, at any operating temperature that your system can experience, is simply asking for trouble down the road.

Frequent hangs, crashes, Blue Screens Of Death (BSOD)  and other highly annoying and disruptive incidents that you can’t seem to pin down to either software or hardware, are often the result. And they become more frequent as your computer ages.

Even silent data corruption can occur, as most operating systems don’t give any warning when data gets written out incorrectly, and do not provide automatic data integrity checking or reliable repair afterwards. Something you only discover when it’s way too late and your oldest backup set is already rotated out.

Another factor to take into consideration – certainly in this day and age – is the Power Factor and the efficiency of the PSU. The Power Factor is the ratio of the real power flowing to the computer to the apparent power taken from the AC outlet. In short, it all relates to the effect the components in your computer have on shifting the voltage and current sinusoids of that alternating current out of phase. The Power Factor Corrected (PFC) power supply cleverly uses additional electrical components to counteract this negative effect so the PF approaches the ideal of 1, or 100%. This is not just of theoretical use: the power company will bill you based on the non-corrected power you apparently draw from the grid, because the ”phantom” power is lost on the transport wires to your residence.

The efficiency is yet another interesting number. It is also represented as a percentage, and calculated as the effective electrical power coming out of the PSU, divided by the power it consumes from the electrical grid. The rest is lost as heat in the components. Smart designs in multiple stage switching power supplies, and the use of quality components, play a big role in achieving a high efficiency in excess of 80%.

Most manufacturers measure the efficiency or Power Factor of their power supplies at room temperature, whereas the only interesting number is that at operating temperature, which is quite a bit higher than room temperature. So watch out for claims that are not backed by an independent review. Your electricity bill will reflect the beneficial effect of a high PF and efficiency as you use your computer(s) more often.

The quickest and easiest test to get an impression of the build quality and electrical characteristics of a computer power supply is strangely enough… the weight test. The reasoning behind this, is that a cheap China-made PSU will have far less components and heat sinks to deliver clean, quality regulated 5V and 12V power than its heavier US or European counterpart. So steer away from those 15$ featherlight tin cans with wires.

Since a few years, power supplies have been adorned with options previously neglected or difficult to implement. We all know the coloured LEDs, the shiny housings and the gold coloured or custom fan grilles, but there are two others that are really useful.

The first is the modular design. This allows you to connect only the cables you need, sometimes in only the length you need. Needless to say that this can make the interior of your computer case much more tidy, and significantly improve airflow, and hence component longevity and necessary fan noise. The very first modular PSUs coped with design problems such as the connectors at the back heating up and even melting because of the almost inevitable electrical resistance they introduced. These kinks have been worked out, and as long as you snap your connectors in securely (as with any connector), you should be perfectly fine.

The second improvement in modern computer power supplies, is noise awareness. Popular brands are even making special PSUs that hardly produce any noise, or are even completely fan-less for low-power applications. Some keep their exhaust fan spinning for two minutes after you switch off your computer, to make sure all remaining heat is taken out of your computer case before final switch-off, similar to video projectors.

All you need to do next, is use your favourite on-line power supply calculator, add 30% extra watts for future expansion, and get yourself a quality, stable, silent, modular, brand name power supply. The extra money you pay will probably be earned back within the year in electricity bills, longer lasting components, and saved time due to less crashes and no silently lost data.

 

Pete Stevens

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