A constant current power supply can be represented as a four
terminal active device.
The input represents a DC voltage
source for basic current regulators, and it represents AC line
voltage for those supplies which are complete with rectifiers
and filters.
To characterize the supply, definitions must be
established.
In a practical system, a transformer, rectifier and filter is
included in each case in order to produce DC power. The
power controller is added after this stage