Current Sensor Circuit with Dual Amplifier Switching
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Solution Overview
Problem
Current current measurement technologies face challenges in accurately measuring a wide dynamic range of currents with minimal waste heat dissipation, particularly in DC power systems that require continuous and uninterrupted monitoring, while also being insensitive to RF and EM interference and maintaining low energy consumption.
Innovation Solution
A current sensor circuit utilizing a single shunt and two instrumentation amplifiers, with a switching mechanism and calibration algorithm, that achieves several orders of magnitude better dynamic range and near-zero energy consumption, allowing for accurate low-current measurements and continuous output with reduced latency and offset errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single shunt and two instrumentation amplifiers are used with switching mechanism, then dynamic range is improved by several orders of magnitude, but device complexity increases
Solution Approach 1:
The current measurement circuit is divided into two separate measurement channels, each with its own instrumentation amplifier and shunt connection. This segmentation allows independent optimization of each channel for different current ranges, achieving wide dynamic range while keeping individual channel complexity manageable
Solution Approach 2:
The circuit employs dynamic switching between the two measurement channels based on the magnitude of current being measured. The switchable connection between the shunts and amplifiers allows the system to adapt its configuration in real-time, selecting the appropriate channel for the current range being measured
2Object-affected harmful factors
If RFI filtering is applied to prevent interference, then immunity to RF and EM fields is improved, but energy consumption increases
Solution Approach 1:
RF filters are introduced as intermediary components between the shunt and instrumentation amplifier. These filters act as mediators that block RF and EM interference from reaching the sensitive amplifier circuits while allowing the desired current measurement signal to pass through
Solution Approach 2:
The patent replaces traditional active filtering methods with passive RF filter implementations that utilize the natural reactance of capacitors and inductors. This substitution reduces the need for active components that would consume additional energy while maintaining effective RF rejection
3Measurement precision
If measurement accuracy for small currents is improved, then coulometry accuracy is improved, but systematic offset error increases
Solution Approach 1:
The circuit incorporates feedback mechanisms through the instrumentation amplifiers that continuously monitor and adjust their own operation. This feedback allows the amplifiers to compensate for systematic offset errors by dynamically adjusting their gain and bias conditions
Solution Approach 2:
The patent employs parameter changes in the instrumentation amplifier configuration, including adjustable gain settings and bias voltage modulation. By dynamically changing these parameters, the system can maintain high accuracy for small current measurements while compensating for systematic offset errors through real-time parameter adjustment
4Productivity
If response time is reduced for quick measurement, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The circuit performs preliminary actions by pre-configuring both measurement channels with appropriate gain settings and filtering parameters before actual measurement occurs. This preliminary setup allows the system to rapidly switch between channels and begin measurement immediately without requiring complex real-time adjustments
Solution Approach 2:
The measurement system employs periodic sampling and processing cycles where the instrumentation amplifiers operate in alternating phases. This periodic operation allows each channel to complete its measurement and processing cycle efficiently, then quickly switch to the next channel, maintaining both speed and precision through rhythmic operation
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
The solution provides high accuracy and low energy consumption across a wide range of currents, enabling accurate coulometry and quick-response electronic fuse functionality while minimizing waste heat and interference effects.
Implementation Method 1
direct measurement of the current as manifested by a voltage drop across a sense resistor (oftentimes called a resistive shunt)
Implementation Method 2
two or more instrumentation amplifiers, switchably measuring voltages at the shunt
Data Source
AI summary
An apparatus and method make use of a single shunt and two or more instrumentation amplifiers, switchably measuring voltages at the shunt. This permits current measurement. At times each instrumentation amplifier has its input shorted, which permits zeroing out many sources of offset in the signal path of that amplifier. Dynamic range is several orders of magnitude better than known current measurement approaches, permitting coulometry.