Differential Current Sensing Circuitry with Replica Devices
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Solution Overview
Problem
Existing current sensing methods in electronic circuits, which use in-line current sense resistors, result in reduced efficiency due to power dissipation as heat.
Innovation Solution
A differential sensing system that employs two current sense paths with replica devices and cross-coupling switches, operating in a chopping mode to sense current through a circuit element without the need for in-line resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an in-line current sense resistor is used to sense current through a circuit element, then the current can be measured, but power is dissipated as heat reducing efficiency
Solution Approach 1:
The patent uses replica devices (transistors) that copy the electrical characteristics of the circuit element to sense current. Instead of measuring current directly through a resistor, the replica devices replicate the current flow and associated voltages, allowing indirect measurement without dissipating power in a sense resistor. The differential amplifier then compares the replica currents to extract the sensed current information.
Solution Approach 2:
The patent replaces the passive resistive sensing mechanism with an active transistor-based replica system. The mechanical/electrical resistance-based current sensing is substituted with a transistor replica model that uses voltage-controlled current sources to mimic the circuit element behavior, enabling lossless current measurement through voltage comparison rather than direct current measurement.
2Loss of energy
If a differential sensing system with replica devices is used, then power loss is reduced, but the device complexity increases
Solution Approach 1:
The patent merges the current sensing function with the existing circuit element model by using replica devices that mirror the circuit element's characteristics. The differential sensing system combines multiple replica devices and cross-coupling switches into an integrated structure where the sensing function is embedded within the replica modeling approach, reducing the need for separate sensing components.
Solution Approach 2:
The replica devices serve multiple functions: they model the circuit element's electrical characteristics for analysis purposes, generate the sensed current signals, and enable differential comparison for accurate measurement. The cross-coupling switches provide both signal routing and chopping functionality, reducing the need for dedicated switching components.
Data Source
AI summary
A differential sensing system for sensing a current through a circuit element of a circuit, the differential sensing system comprising: a first current sense path having an input for coupling to a first node of the circuit element, the first current sense path comprising a first plurality of replica devices; a second current sense path having an input for coupling to a second node of the circuit element, the second current sense path comprising a second plurality of replica devices, wherein the second plurality is equal to the first plurality; a first cross-coupling switch operable to couple the input of the first current sense path to the second plurality of replica devices; a second cross-coupling switch operable to couple the input of the second current sense path to the first plurality of replica devices; differential amplifier circuitry having first and second inputs, wherein the differential amplifier circuitry is configured to output a differential replica current pair indicative of the current through the circuit element; and a controller, wherein the differential sensing system is operable in a chopping mode to perform a chopping operation in which: the first cross-coupling switch and a replica device of the first current sense path are controlled by the controller to couple the first input of the differential amplifier circuitry to the input of the first current sense path in a first phase of a chopping operation and to the input of the second current sense path in a subsequent phase of the chopping operation; and the second cross-coupling switch and a replica device of the second current sense path are controlled by the controller to couple the second input of the differential amplifier circuitry to the input of the second current sense path in the first phase of the chopping operation and to the input of the first current sense path in the subsequent phase of the chopping operation.