Temperature-Self-Compensated Current Sensing Amplifier Circuit
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Solution Overview
Problem
Current sensing circuits face inaccuracy due to temperature variation, process stress, and package stress, which existing solutions fail to address effectively without increasing circuit complexity and power consumption.
Innovation Solution
A current sensing circuit utilizing a fully differential amplifier with switched capacitor circuits emulating resistors, which compensates for temperature variations by matching the temperature coefficients of sense and input resistors, thereby maintaining gain independence from temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital signal processing techniques are used to adjust for temperature variation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces digital signal processing techniques with an analog circuit solution. Specifically, it uses a fully differential amplifier with temperature-self-compensating feedback resistors to directly compensate for temperature effects on the sense resistor in the analog domain, eliminating the need for digital correction algorithms and associated digital circuitry.
Solution Approach 2:
The patent introduces fully differential amplifier circuits as intermediary components between the sense resistor and the output. These amplifiers, combined with temperature-matched feedback resistors, serve as analog intermediaries that automatically compensate for temperature variations without requiring digital processing intervention.
2Measurement precision
If digital correction circuits are added to compensate for temperature, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The patent substitutes energy-consuming digital correction circuits with a passive analog compensation mechanism. The fully differential amplifier with temperature-matched resistors provides automatic temperature compensation through its inherent circuit characteristics, eliminating the need for active digital processing and associated power consumption.
Solution Approach 2:
The circuit implements self-compensation by using feedback resistors that are intentionally designed to track the temperature characteristics of the sense resistor. This self-service mechanism automatically adjusts for temperature effects without external intervention or additional power consumption for correction operations.
3Device complexity
If conventional current sensing circuit is used, then device complexity is low, but measurement precision deteriorates due to temperature variation
Solution Approach 1:
The patent changes the temperature parameter characteristics of the feedback resistors to match those of the sense resistor. By selecting feedback resistors with identical temperature coefficients, the circuit maintains a stable gain ratio across temperature variations, thereby improving measurement precision while keeping the analog circuit structure relatively simple.
Solution Approach 2:
The patent creates equipotential conditions by ensuring that the temperature-induced resistance changes in the feedback path match those in the sense path. This balancing approach ensures that temperature variations affect both paths equally, canceling out their impact on the measurement accuracy.
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 accurate current measurement by eliminating temperature-related inaccuracies, reducing circuit complexity, and minimizing power consumption, while ensuring precise cutoff frequency and high DC gain.
Implementation Method 1
Each of the first and second feedback resistors is implemented as a switched capacitor circuit which emulates a resistor
Data Source
AI summary
A current sensor architecture is implemented using a trans-resistance amplifier circuit having a low pass filter characteristic. The current sensing resistor and the input resistors for the amplifier circuit are matched thermally so that they have substantially identical temperature coefficients. The feedback resistors, which are coupled in parallel with corresponding capacitors, are implemented using switched capacitor circuits that emulate resistors. With this configuration, the current sensor is temperature insensitive.