Bidirectional Current Sensing with Matched Sense Resistors
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Solution Overview
Problem
Sense resistors used for current monitoring in bidirectional current paths exhibit non-linearity, leading to inaccuracies in current sensing due to varying spatial current density and asymmetrical current sources and sinks.
Innovation Solution
Employ two sense resistors with matching non-linearities but opposite directions, arranged symmetrically with respect to transistors and electrodes, to compensate for non-linearity by combining their voltage measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sense resistor is used in a bidirectional current path, then the current sensing circuit is simple, but non-linearity occurs due to asymmetrical current sources and sinks, leading to inaccurate current sensing
Solution Approach 1:
The current sensing function is divided into two separate sense resistors (first sense resistor and second sense resistor) positioned at different locations in the bidirectional current path. Each resistor handles current flow in one direction, segmenting the sensing function to eliminate non-linearity caused by asymmetrical current sources and sinks.
Solution Approach 2:
The patent intentionally introduces asymmetry by placing sense resistors at different physical locations in the current path. This asymmetric arrangement compensates for the inherent asymmetry in current sources and sinks, allowing each resistor to operate in a region where current density is more uniform and linear.
2Reliability
If sense resistors are placed to monitor current on both sides of the load, then overcurrent protection is improved, but circuit complexity increases
Solution Approach 1:
The first and second sense resistors serve multiple functions: they provide current sensing for normal operation, enable overcurrent protection on both sides of the load, and compensate for non-linearity. This multi-functionality achieves comprehensive protection without proportionally increasing circuit complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Compensates for non-linearity in current sensing, providing accurate current monitoring and detecting overcurrent conditions on both sides of the load, reducing circuit size and complexity.
Implementation Method 1
A current monitor 105 may monitor the voltage drop across sense resistor 104 and determine the load current
Implementation Method 2
the sense resistor may exhibit non-linearity in use, which can adversely impact the accuracy of the current sensing
Data Source
AI summary
This application relates to methods and apparatus for sensing current in a monitored current path, where the monitored current path is bidirectional such that current can flow in either direction along the monitored current path. A current sensor has first and second sense resistors (401a, 401b) configured to each pass a current corresponding to the current in the monitored current path. The first and second sense resistors are configured to have a matching arrangement, such that current flow through the first sense resistor when current is flowing in one direction in the monitored current path matches current flow through the second sense resistor when current is flowing in the opposite direction in the monitored current path.