Dual-Shunt Current Sensor With Switching Fabric Error Correction
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Solution Overview
Problem
Current current measurement technologies face challenges in accurately measuring low currents while maintaining minimal waste heat dissipation, especially in DC power systems, where they need to be sensitive, low in latency, and resistant to RF and EM interference, with existing methods like shunt-based and Hall-effect sensors having limitations in precision and power consumption.
Innovation Solution
The use of two shunts in series within a switching fabric, with methodical make-before-break cycling of switches for real-time error correction and RFI filtering, allowing for continuous and accurate current measurement with minimal power dissipation, using FETs and instrumentation amplifiers to manage voltage drops and errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shunt resistor is used for direct current measurement, then measurement precision is improved, but power dissipation increases
Solution Approach 1:
The patent implements periodic switching between two shunt resistors, alternating their roles between active measurement and idle states. This periodic action allows the system to achieve accurate DC measurements when needed while dissipating less average power overall, as each shunt spends part of the time inactive or in a low-power state.
Solution Approach 2:
The patent performs preliminary error correction measurements during the switching cycles, measuring and storing offset errors before actual current measurements. This preliminary action allows the system to compensate for measurement errors without requiring continuously high-power operation, thereby reducing overall power dissipation while maintaining precision.
2Measurement precision
If the sensitivity of the current sensor is increased to measure small currents, then measurement precision for low currents is improved, but the ability to measure large currents accurately deteriorates
Solution Approach 1:
The patent divides the measurement function into multiple segments by using two different shunt resistors with different resistance values. One shunt is optimized for measuring small currents with high sensitivity, while the other is optimized for large currents. The system segments the measurement range and selects the appropriate shunt based on the current magnitude, achieving both high precision for small currents and broad dynamic range coverage.
Solution Approach 2:
The patent implements dynamic switching between two shunt resistors based on the magnitude of the current being measured. The system automatically selects the appropriate shunt resistance value according to the current level, making the measurement system adaptive and versatile across a wide dynamic range while maintaining high precision for both small and large current measurements.
3Reliability
If RFI filtering is added to prevent electromagnetic interference, then reliability is improved, but response time deteriorates
Solution Approach 1:
The patent employs periodic switching and measurement cycles that incorporate RFI filtering during specific phases while maintaining fast response capability. By structuring the measurement process with periodic filtering actions rather than continuous filtering, the system achieves reliable interference rejection without excessive latency, as the filtering is applied methodically within the switching cycle rather than continuously delaying measurements.
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
This approach provides accurate current measurement across a wide dynamic range with reduced latency and minimal waste heat, enabling quick-response electronic fuse capabilities and effective filtering of interference, while being economically viable without the need for expensive components.
Implementation Method 1
direct measurement of the current as manifested by a voltage drop across a sense resistor
Implementation Method 2
A current sensing approach using two shunts in series within a switching fabric, with methodical make-before-break cycling of switches
Data Source
AI summary
A current sensing approach makes use of two shunts in series, embedded in a switching fabric, each shunt the object of a differential measurement of voltage drop across the shunt. Methodical make-before-break cycling of the switches in the switching fabric permit real-time or very near-real-time measurement of nearly all of the errors such as offset errors present in each differential-measurement path. Additional differential measurement paths can be connected with the shunts, with RFI filtering at shorter time constants to serve electronic fuse needs.