Sensor Driving Device with Dynamic Resistor Switching
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Solution Overview
Problem
Existing sensor driving systems face challenges in maintaining consistent current consumption and sensitivity when measuring pressure and temperature, leading to increased voltage variation, larger circuit sizes, and higher costs due to varying resistance values and dynamic range requirements.
Innovation Solution
A sensor driving device with a Wheatstone bridge configuration, including a first resistor connected in series between the main power supply and the sensor circuit, a second resistor connected between the sensor circuit and the reference power supply, and a temperature output circuit in parallel, which reduces the difference in input levels to the analog front-end circuit and improves sensitivity by adjusting resistance values and common mode potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a resistor element is connected in series to a Wheatstone bridge to suppress current consumption variation, then current consumption stability is improved, but sensitivity in pressure detection decreases
Solution Approach 1:
The patent implements dynamic switching of the resistor element's connection state. The resistor is connected in series during temperature measurement to suppress current consumption variation, and disconnected during pressure measurement to maximize sensitivity. This time-varying configuration resolves the contradiction by adapting the circuit topology to the specific measurement mode.
Solution Approach 2:
The patent changes the resistance parameter of the overall circuit by switching the resistor element in and out. During temperature measurement, the resistor is included to increase total resistance and reduce current variation. During pressure measurement, the resistor is excluded to maintain low total resistance for high sensitivity. This parameter switching resolves the contradiction between stability and sensitivity.
2Measurement precision
If the resistance value of the series resistor is decreased to increase pressure detection sensitivity, then sensitivity is improved, but the difference in input signal levels to the A/D converter increases
Solution Approach 1:
The patent extracts the series resistor from the circuit during pressure measurement, removing its influence on the signal level. This allows the Wheatstone bridge to operate with optimal sensitivity without the resistor's voltage drop, while the A/D converter only needs to handle the bridge's output range, reducing its dynamic range requirement.
Solution Approach 2:
The patent dynamically switches the resistor's connection state based on measurement mode. During pressure measurement, the resistor is disconnected to maintain signal levels suitable for the A/D converter's dynamic range. During temperature measurement, the resistor is connected to suppress current variation. This dynamic configuration resolves both contradictions simultaneously.
3Measurement precision
If the input level at temperature measurement time is increased, then temperature measurement accuracy is improved, but leak currents of multiplexer and switches increase
Solution Approach 1:
The patent changes the circuit configuration parameter by switching the resistor's connection state. During temperature measurement, the resistor is connected to establish an appropriate input level for the A/D converter, improving temperature measurement accuracy. The resistor's presence also limits the current through the multiplexer and switches, reducing leak current effects.
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 allows for improved sensitivity in pressure detection while reducing the dynamic range and power consumption of the analog front-end circuit, enabling efficient and accurate simultaneous pressure and temperature measurement without significant increases in circuit size or costs.
Implementation Method 1
a pressure sensor having a Wheatstone bridge, which is formed of gauge resistors (piezoelectric resistors) arranged on a diaphragm movable with pressure
Implementation Method 2
The resistance value of a sensor circuit including the Wheatstone bridge also varies with temperature
Data Source
AI summary
A sensor driving device drives a sensor circuit formed of a Wheatstone bridge, which is connected between a main power supply for supplying a power supply potential and a reference power supply for supplying a reference potential lower than the power supply potential and includes at least one gauge resistor varying a resistance value thereof with deformation caused by external force. The sensor driving device includes a first resistor, which is connected in series with the sensor circuit between the main power supply and the sensor circuit, and a second resistor, which is connected between the sensor circuit and the reference power supply. The sensor driving device further includes a temperature output circuit connected in parallel to the sensor circuit relative to the main power supply. The temperature output circuit includes two output terminals, which output a potential difference smaller than a potential difference between one end of a main power supply side and one end of a reference power supply side.