Chopper Instrumentation Amplifier Gain Switching to Prevent Saturation
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Solution Overview
Problem
Capacitively coupled chopper instrumentation amplifiers experience output saturation and prolonged signal recovery times due to high DC offsets when operating with high-voltage battery signals, particularly during the initial period of signal reception.
Innovation Solution
The amplifier reduces gain during the initial period by adjusting the differential input and feedback capacitances through a switching capacitor voltage division method, using a switch circuit controlled by a timing signal to connect capacitors in series or parallel, thereby avoiding output saturation and speeding up signal recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amplifier operates with high gain during the initial period, then the signal amplification is strong, but the output saturation occurs due to high DC offset
Solution Approach 1:
The patent implements dynamic gain adjustment by switching between different capacitor configurations (series/parallel) based on the operational phase. During the initial period, capacitors are connected in series to provide lower gain and avoid saturation. After the initial period, capacitors are switched to parallel configuration to provide higher gain for normal operation. This dynamic reconfiguration resolves the contradiction between strong signal amplification and avoidance of output saturation.
Solution Approach 2:
The patent changes the capacitance parameter by altering the connection topology of the capacitors. By switching between series and parallel connections, the effective capacitance value changes, which directly adjusts the gain of the amplifier. This parameter change allows the system to adapt between avoiding saturation (lower gain) and achieving strong amplification (higher gain) at different operational stages.
2Device complexity
If the amplifier uses fixed gain configuration, then the circuit structure is simple, but the signal recovery time is prolonged during the initial period
Solution Approach 1:
The patent introduces dynamic capacitor switching controlled by a control signal to adjust the gain during the initial period. This dynamic adjustment accelerates signal recovery by preventing saturation, while the switching mechanism adds only moderate complexity to the otherwise fixed gain circuit structure.
Solution Approach 2:
The patent applies preliminary action by adjusting the gain configuration before the main amplification phase. During the initial period, the capacitors are pre-configured in series to provide lower gain, preventing saturation before it occurs. This preliminary adjustment of the capacitor connection state avoids the need for lengthy recovery times after saturation.
3Ease of manufacture
If the capacitor feedback network uses fixed capacitance values, then the manufacturing process is simple, but the operational flexibility is reduced
Solution Approach 1:
The patent employs dynamic switching of capacitor connections (series/parallel) to provide multiple gain configurations without requiring physically different capacitor values. This approach maintains simple manufacturing with fixed capacitance values while achieving operational flexibility through controlled reconfiguration of the capacitor network during different operational phases.
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
This approach significantly shortens the time to reach a stable output voltage level during the initial period, improving the operational efficiency of the capacitively coupled chopper instrumentation amplifier in high-precision high-voltage battery voltage signal sensing systems.
Implementation Method 1
a capacitor feedback network, which includes a pair of differential input capacitors and a pair of differential feedback capacitors, wherein each of the differential input capacitors is connected to a corresponding one of the differential feedback capacitors in series between the input chopping unit and the feedback chopping unit
Data Source
AI summary
A capacitively coupled chopper instrumentation amplifier includes: an input chopper unit, configured to chop a differential input signal based on a clock signal to generate a chopped differential input signal; an output chopper unit, configured to chop a differential output signal based on the clock signal to generate a chopped differential output signal; a capacitor feedback network, configured to convert a differential difference of the chopped differential output signal and the chopped differential input signal to generate a differential feedback signal by a switching capacitor division voltage method with the input chopper unit and the output chopper unit; and a fully differential amplifier, which is configured to amplify the differential feedback signal to generate a differential output signal; wherein, in an initial period after the input chopper unit receives a differential input signal, the capacitively coupled chopper instrumentation amplifier prevents an output saturation by reducing a gain.