Sensor Frontend Circuit With Single-Loop Resistance Matching
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Solution Overview
Problem
Conventional frontend circuits for resistive sensors face challenges such as mismatch between sensitive and reference branches, high power consumption, sensitivity to leakage currents, and area occupation issues due to varying currents and capacitive loads, especially when dealing with wide range resistance measurements.
Innovation Solution
A circuit arrangement with a single control loop that transfers voltage information from a variable resistance branch to a fixed resistance branch, regulating current in the fixed branch to match voltage drops, and incorporating a current limiter to manage excessive currents, thereby reducing component size and power consumption while maintaining robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional frontend circuits use two independent control loops with variable and fixed resistors for wide range resistance measurement, then measurement range is improved, but power consumption increases and circuit complexity increases
Solution Approach 1:
The patent merges two independent control loops into a single control loop that sequentially controls both the variable resistor branch and the fixed resistor branch. This consolidation reduces the number of active components and control circuits, thereby reducing power consumption while maintaining the capability to measure across a wide resistance range by switching between branches.
Solution Approach 2:
The patent implements periodic switching between the variable resistor branch and the fixed resistor branch within a single control loop. The control loop alternates between measuring the variable resistor and the fixed resistor, using the fixed resistor as a reference. This periodic action allows wide range measurement capability while reducing average power consumption compared to having both branches active simultaneously with independent control loops.
2Measurement precision
If conventional frontend circuits use two independent control loops for logarithmic compression measurement, then measurement accuracy is improved, but device area increases
Solution Approach 1:
The patent combines the control functions for both measurement branches into a single control loop, reducing the number of amplifiers, transistors, and other control components needed. This merging significantly reduces the device area while maintaining measurement accuracy through sequential measurement and reference comparison.
Solution Approach 2:
The patent extracts the control loop functionality from both branches and consolidates it into a single shared control loop. By taking out the redundant control components and sharing them between branches through time-division multiplexing, the device area is reduced while the measurement precision is preserved through the reference measurement approach.
3Use of energy by moving object
If conventional frontend circuits operate with very low currents to reduce power consumption, then power consumption is reduced, but sensitivity to leakage currents increases
Solution Approach 1:
The patent uses periodic switching between measurement branches with a single control loop, allowing the circuit to operate at optimized current levels during each phase. The sequential measurement approach enables better control over current levels while reducing the impact of leakage currents through the reference measurement technique, maintaining reliability while managing power consumption.
4Reliability
If conventional frontend circuits use large component sizes to handle wide current ranges, then robustness is improved, but device area increases
Solution Approach 1:
The patent implements periodic switching between the variable resistor branch and the fixed resistor branch, allowing each branch to be optimized for its specific current range. The fixed resistor branch serves as a reference and can be designed with appropriate sizing for its operating conditions. This time-division approach allows smaller component sizes compared to designing for maximum current range continuously, reducing device area while maintaining robustness through proper reference comparison.
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 reduces power consumption, increases robustness against short circuits, and achieves accurate resistance measurements across a wide range with minimal error, ensuring reliable operation and reduced design risks.
Implementation Method 1
The logarithmic compression technique uses the current-to-voltage dependence of bipolar diodes included in the branches
Implementation Method 2
Each of the two branches includes a control loop to generate a predetermined voltage at the resistors. The logarithmic compression technique uses the current-to-voltage dependence of bipolar diodes
Data Source
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AI summary
A circuit arrangement comprises a first branch (101) comprising a resistor of variable resistance (131) and a diode-connected bipolar transistor (134) and a second branch comprising a resistor of fixed resistance (141) and another diode-connected bipolar transistor (135). A control loop (110) reproduces a voltage drop at the resistor of variable resistance (131) to a voltage drop at the resistor of fixed resistance (141). Output terminals (136, 137) are connected to the bipolar transistors (134, 135) to supply a differential voltage (VBE1, VBE2). The circuit arrangement may be used as an analog frontend circuit in a gas sensor or a temperature sensor arrangement.