Device for controlling a supply voltage for a terminal

摘要

A control device includes a circuit operable to sense an analog input voltage dependent on a line current flowing via a communication line of a terminal generate an analog difference voltage in a constant line current operation based on a difference between the sensed analog input voltage and an analog feedback voltage which depends on an adjustable nominal direct-current value and filter a sequence of control error values from a sequence of digital difference voltage values converted from the generated analog difference voltage. The circuit is further operable to convert a control value generated from the sequence of control error values in the constant line current operation to an analog direct voltage for supplying the terminal and convert the nominal direct-current value into the analog feedback voltage in the constant line current operation.

主权项

1. A method of switching a control device for a line terminal between a constant line current operation and a constant line voltage operation, the method comprising:
adding a nominal direct-current value to a sequence of control error values which indicate a difference between an analogue feedback voltage and an analogue input voltage sensed at the line terminal, to form a sequence of aggregate current values; and switching the control device from the constant line current operation to the constant line voltage operation responsive to one of the aggregate current values dropping below a predetermined adjustable direct-current threshold value.