Variable power supply technique for use with a high efficiency line driver
AssigneeNortel Networks Limited
InventorsG. Kate Harris, Dennis W. Mitchler
Life of this patent
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Abstract
A variable power supply technique for use with a high efficiency line driver uses a signal peak amplitude to determine a start of a rise time for a power supply to begin supplying operating voltage to the line driver. This ensures that the voltage supplied to the line driver essentially tracks the output signal. A slew start delay circuit detects when the signal rises above a level that can be supported by a current power supply, and determines a variable delay for switching on a power supply to supply a higher voltage to the line driver. The advantages include reduced power usage, less heat dissipation, and the ability to select a primary power supply that outputs a lower voltage.
Claims19
A supply voltage control circuit for determining a variable delay before a selection of a power supply to supply a higher voltage to a driver that applies an encoder signal to a communications path, comprising:
- a) a threshold detector for receiving the signal and determining when an amplitude of the signal crosses at least one predefined threshold;
- b) a slew start controller that receives output from the threshold detector and a signal encoder, and determines a delay before a change to supply the higher voltage to the driver is required, based on a peak amplitude of the signal with respect to the higher voltage output by a power supply;
- c) a supply voltage selector for selecting the higher voltage based on an output of the threshold detector, after the delay determined by the slew start controller;
- and
- d) a slew rate controller for limiting a rate of transition to the higher voltage selected by the supply voltage selector.
A method of determining a variable delay before a selection of a power supply to supply voltage to a driver that applies an encoder signal to a communications path comprising steps of:
- a) determining when a change in voltage supply to the driver is required by comparing a peak amplitude of the signal with a voltage output by the higher power supply;
- b) selecting a one of two power supplies based on the peak amplitude of the signal;
- and
- c) switching to the selected power supply after a variable delay based on the peak amplitude of the signal and a slope of a waveform of the power supply.
Dependencies are inferred from the claim text.