Powering Your PC: Truths and Misconceptions
A Guide To Power Supplies

Power Conversion Basics:

There are three types of electronic power conversion devices in use today, which are classified as follows:

1. The AC/DC Power Supply
2. The DC/DC Converter
3. The DC/AC Inverter

A typical PC power supply falls under the first of the three categories listed above, it converts AC line voltage to DC power, thus it is generically referred to as a "Power Supply". This is the only type of power conversion that we will be talking about in this article (except for a brief discussion on Uninterruptible Power Supplies).

A power supply performs the following functions:

1. Rectification: Convert the incoming AC line voltage to DC voltage.
2. Voltage Transformation: Supply the correct DC voltage level(s).
3. Filtering: Smooth the ripple of the rectified voltage.
4. Regulation: Control the output voltage level to a constant value irrespective of line, load and temperature changes.
5. Isolation: Separate electrically the output from the input voltage source.
6. Protection: Prevent damaging voltage surges from reaching the output; provide back-up power or shut down during a brown-out.

An ideal power supply would be characterized by supplying a smooth and constant output voltage regardless of variations in line voltage, load current, or ambient temperature, at 100% conversion efficiency.¹