Bridge Sensor IC Offset Compensation With Dynamic Reference Voltage
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Solution Overview
Problem
Existing bridge circuits used for detecting physical quantities like pressure or acceleration suffer from deteriorated sensing accuracy due to an error component (offset voltage) that cannot be removed, especially when resistors in the circuit vary in resistance value.
Innovation Solution
An integrated circuit and semiconductor device configuration that includes a differential amplifier circuit and a reference voltage output circuit, where the reference voltage level is adjusted to either a sum or difference of a predetermined voltage and an amplified offset voltage, allowing for the removal of the offset voltage and preventing output saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If AC voltage is applied to the bridge circuit to remove noise, then noise is removed, but offset voltage error cannot be removed and sensing accuracy deteriorates
Solution Approach 1:
The patent applies AC voltage with alternating polarity to the bridge circuit input terminals in a periodic manner. By switching between positive and negative polarity states, the system causes the offset voltage to manifest as an alternating signal that can be distinguished from the DC sensor output through periodic measurement and processing
Solution Approach 2:
The patent measures the offset voltage by applying AC voltage and measuring the bridge circuit output during calibration phases. This measured offset information is then fed back and subtracted from subsequent sensor measurements to compensate for the error, creating a closed-loop error correction system
2Device complexity
If fixed reference voltage is used in differential amplifier, then circuit is simple, but output saturation occurs and sensing accuracy is limited
Solution Approach 1:
The patent replaces the fixed reference voltage with a dynamic reference voltage that changes based on the polarity of the applied AC voltage. The reference voltage output circuit switches between different voltage levels (e.g., Vref and -Vref) synchronized with the AC voltage polarity, allowing the differential amplifier to operate optimally across different measurement conditions without saturation
Solution Approach 2:
The patent changes the reference voltage parameter dynamically based on the AC voltage polarity state. During calibration with positive polarity, one reference voltage level is applied, and during calibration with negative polarity, a different reference voltage level is applied. This parameter change enables accurate offset measurement and prevents output saturation
Data Source
AI summary
An integrated circuit includes: an amplifier circuit outputting a first voltage and a second voltage respectively in a first case and a second case, in which two input voltages of opposite polarities are applied to a pair of input terminals of a bridge circuit, the first and second voltages being based on a reference voltage and first and second amplified voltages, obtained by amplifying, by a predetermined gain, first and second output voltages outputted from a pair of output terminals of the bridge circuit; and a reference voltage output circuit setting the reference voltage to a first level and a second level respectively in the first and second cases. The first and second levels respectively correspond to a sum of, and a difference between, a predetermined voltage and another amplified voltage obtained by amplifying, by the predetermined gain, an offset voltage generated at the output terminals of the bridge circuit.