Plug-in and Desktop Power Supplies
The humble plug-in or desktop power supply is a part of everyone's everyday life and its importance is often overlooked until the time comes when a replacement is needed, and only then is it realised that these devices come in an amazing range of different specifications. They do, of course, simply consist of a step-down transformer and regulator, but as they are used to power almost every conceivable DC-powered item, many different permutations are necessary. Highly efficient and accurate switching regulators are often used. The first considerations are the input supply and the required output DC voltage and current. Most of these power supplies operate on a wide range of different mains supplies, and due to their fairly universal nature, many come with the option of interchangeable mains plug adapters for different countries. Some simply offer a 2-pin C8, or sometimes a 3-pole C14 socket for use with a separate power lead. Output terminals also tend to be in the fairly standard form of appropriately-sized barrel plugs and jack-plugs, but some units, especially those offering a choice of output voltages, offer interchangeable secondary terminations, often also with polarity changing capabilities.