Method and device for coupling a DC supply line to a telephone line or coaxial cable

摘要

A coupling device that implements a related method for remote powering wide band digital telecommunication devices through telephone lines or coaxial cables installed in all buildings, has an AC blocking transistor inserted in the electrical path from a voltage supply line to the telephone line or coaxial cable. The transistor has a first current terminal coupled to the supply line and a second current terminal coupled to the telephone line, and it is controlled with a DC control voltage such to keep it in a substantially linear functioning condition at the edge of a saturation condition during the normal functioning whatever the supply current that flows through the transistor is, destined to the connected telecommunication devices. This may be done by properly generating this control voltage by means of a dedicated voltage generator, or by nullifying the DC component of the difference of potential between the control terminal and the second current terminal, for example through a low-pass filter that generates the voltage on the control terminal as a low-pass replica of the voltage on the second current terminal.

主权项

1. A coupling device of a DC power supply line to a telephone line or coaxial cable, said coupling device having a first connection pad to a DC power supply line and a second connection pad to a telephone line or coaxial cable adapted to provide a DC voltage and a DC supply current to at least a telecommunication device connected thereto, said coupling device having an electrical path, defined between said first pad and said second pad, adapted to be crossed by said DC supply current,
at least an AC blocking transistor inserted in said electrical path, having a first current terminal functionally coupled to said first pad and a second current terminal functionally coupled to said second pad; a control circuit connected between said second current terminal and a control terminal of said AC blocking transistor, adapted to generate a DC control voltage of the AC blocking transistor to keep it in a linear functioning condition at the edge of a saturation functioning condition when the DC supply current flows through the AC blocking transistor, wherein said control circuit is a low-pass filter adapted to generate said control voltage as a low-pass replica of the voltage on said second current terminal.