The purpose of a 'power supply' is to provide a source of direct current (DC) of appropriate voltage and with adequate current capacity for the equipment it is to supply. This usually requires a transformer to convert the alternating current (AC) input to a different AC output voltage, one or more rectifiers to convert the AC to DC and chokes and capacitors to smooth out any remaining AC 'ripple' on the DC output.

In the late 20th Century, switched-mode power supply also became available. They work on a different principle. In switched mode power supplies, processes of voltage transformation, rectification, filtering and regulation all take place at much higher frequencies than the 50Hz mains supply. Consequently, all the components can be more compact and efficient and the need for bulky transformers and chokes is avoided.

The output may need to be regulated, to maintain a constant output voltage for a range of currrent loadings and to compensate for variations in supply voltage. At the time the CSIR Mk1/CSIRAC was built, saturable reactors were commonly used to regulate the output of the power supplies.

In the late 20th Century, a linear regulator was used to stabilize and adjust the output voltage. This regulator greatly reduced the ripple and noise in the output DC current. Linear regulators often provided current limiting, protecting the power supply and attached circuit from overcurrent.

Examples of power supplies used in CSIRAC are shown in the following three diagrams. The diagrams show how the various components were connected.

[HT 13519.87] Schematic Diagram - CSIRAC, 'POWER SUPPLY', B19620
[HT 13519.73] Schematic Diagram - CSIRAC, 'POWER SUPPLY No. 2', B21057
[HT 13519.98] Schematic Diagram - CSIRAC, 'TEST POWER SUPPLY', C24895
Accessed and edited on 18 november 2008

More Information