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# Self Adaptive Remote Powering Circuit

IP.com Disclosure Number: IPCOM000082809D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 46K

IBM

## Related People

Esteban, D: AUTHOR [+1]

## Abstract

The use of a fixed voltage source for powering remote terminals, for example telephone sets, through transmission lines has a drawback that the power supply voltage is determined by the maximum line resistance and the terminal current and voltage requirements. Accordingly, for shorter lines, most of the power delivered by the power supply is dissipated in line resistors or other devices.

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The use of a fixed voltage source for powering remote terminals, for example telephone sets, through transmission lines has a drawback that the power supply voltage is determined by the maximum line resistance and the terminal current and voltage requirements. Accordingly, for shorter lines, most of the power delivered by the power supply is dissipated in line resistors or other devices.

Power efficiency at the terminal level is improved when using the circuit shown in the drawing.

The output current source consisting of transistor T1, resistors R1, R2 and bias current source I is driven by an adaptive voltage source. The adaptive voltage source is a switched voltage regulator consisting of switching transistors T2, T3, tank circuit (L, C, D), comparator T4, T5, and bias current source I". If VT and IT are the maximum voltage and current required by the terminal, the total power supply voltage needed is: V = VT + VC + VL where VL = RL x IT is the line voltage drop.

The differential voltage pair of transistors T4, T5 compares variable voltage V supplied to the current source with input line voltage VL + VT which is equal to V - VC, where VC is the constant voltage drop of the current source. Constant voltage drop VC is obtained by current I' and resistor R'2.

As a result, the adaptive voltage source supplies, via the current source, the input transmission line with a voltage, the value of which is in direct relationship with t...