Chopper Circuit for Micromechanical Sensor Noise Reduction
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Solution Overview
Problem
Integrated circuits face challenges in achieving high signal-to-noise ratios due to noise contributions from various circuit modules, particularly pink noise, which limits the achievable signal-to-noise ratio to around 60 decibels or less, and the inefficiency and heat generation associated with on-chip DC voltage generation.
Innovation Solution
A measuring arrangement incorporating a micromechanical sensor, a bridge circuit, a DC voltage source, and a chopper with a switch structure that alternately couples a charge store to the DC voltage and the bridge circuit to reduce low-frequency noise components, enabling a higher signal-to-noise ratio and efficient power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If on-chip DC voltage generation is used, then power supply integration is improved, but power efficiency deteriorates and waste heat increases
Solution Approach 1:
The patent employs periodic switching action through a chopper circuit that alternately connects the DC voltage source to the bridge circuit at a specific frequency. This periodic operation enables the sensor circuit to achieve higher effective signal-to-noise ratio by modulating the signal away from low-frequency pink noise, while maintaining efficient power consumption through controlled duty cycle operation.
Solution Approach 2:
The patent changes the operating parameters by using AC coupling through the chopper circuit instead of direct DC coupling. This parameter change transforms the signal representation from DC level to AC waveform, enabling the system to overcome pink noise limitations and achieve 75 dB or more signal-to-noise ratio while maintaining efficient power supply integration.
2Device complexity
If on-chip DC voltage generation is used, then power supply integration is improved, but waste heat generation increases
Solution Approach 1:
The periodic switching operation of the chopper circuit enables efficient power transfer by confining current flow to specific time intervals. This reduces continuous power dissipation and associated waste heat generation, while maintaining the benefits of integrated on-chip power supply.
3Measurement precision
If pink noise optimization by enlarging gate area is applied, then signal-to-noise ratio is improved, but chip area requirement increases
Solution Approach 1:
Instead of increasing transistor gate area to reduce pink noise, the patent uses periodic chopping action to modulate the signal to higher frequencies where pink noise has lower spectral density. This achieves improved signal-to-noise ratio of 75 dB or more without increasing chip area.
Solution Approach 2:
The patent changes the frequency domain characteristics of the signal by using AC coupling through the chopper circuit. This parameter change shifts the signal spectrum away from low-frequency pink noise dominance, achieving high measurement precision without requiring larger transistor dimensions.
4Use of energy by moving object
If low DC voltage (2.5V or less) is used for amplifier supply, then power consumption is reduced, but signal-to-noise ratio is limited
Solution Approach 1:
The periodic chopping operation transforms the low-voltage amplifier output into a modulated AC signal. This enables the system to achieve high signal-to-noise ratio through frequency-domain separation from pink noise, while maintaining low power consumption from the 2.5V or less amplifier supply.
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 achieves a signal-to-noise ratio of 75 dB or more and reduces power consumption and waste heat, while maintaining efficient area occupation and noise reduction without requiring external capacitors.
Implementation Method 1
a chopper including at least one first charge store and a switch structure, The switch structure is configured to couple the first charge store alternately to the DC voltage and the bridge circuit
Data Source
AI summary
In various embodiments, a measuring arrangement is provided. The measuring arrangement may include a micromechanical sensor including a capacitor, a bridge circuit including a plurality of capacitors, at least one capacitor of which is the capacitor of the micromechanical sensor, an amplifier coupled, on the input side, to an output of the bridge circuit, a DC voltage source configured to provide an electrical DC voltage, a chopper including at least one first charge store and a switch structure, The switch structure is configured to couple the first charge store alternately to the DC voltage and the bridge circuit for the purpose of coupling an electrical mixed voltage into the bridge circuit.