Current Sensor Miller Compensation for Accurate Input Voltage Holding
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Solution Overview
Problem
Current sensors face accuracy issues due to voltage changes affecting stray capacitors, leading to reduced transconductance and gain in operational amplifiers, which impede precise current measurement.
Innovation Solution
A current sensor with a voltage generation circuit and a voltage integration circuit, utilizing a differential amplifier and compensation capacitors to maintain a fixed input voltage, forming a Miller compensation loop, thereby reducing voltage differences and enhancing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional integrator is used for frequency compensation, then the circuit structure is simple, but voltage changes at the input terminal cause current leakage through stray capacitors and reduce transconductance and gain, thereby decreasing measurement precision
Solution Approach 1:
The operational amplifier is divided into two stages: a first amplifier (differential amplifier) and a second amplifier. The first capacitor is connected between the output terminal of the voltage generation circuit and the output terminal of the first amplifier, forming a Miller compensation specifically for the first stage. This segmentation allows independent optimization of each stage's frequency compensation, improving current sensing accuracy while maintaining reasonable circuit complexity
Solution Approach 2:
The first capacitor acts as an intermediary element that provides frequency compensation by reducing the voltage difference between the first voltage (input terminal voltage) and the second voltage (reference voltage). This intermediary capacitor mitigates the harmful voltage changes that would otherwise cause current leakage through stray capacitors and reduce transconductance, thereby improving measurement precision without requiring a completely complex circuit structure
2Measurement precision
If voltage compensation is implemented to improve accuracy, then measurement precision increases, but the circuit complexity increases due to additional components
Solution Approach 1:
The circuit operates in two dynamic phases: reset phase and integration phase. During the reset phase, the first capacitor is connected to provide frequency compensation and reduce voltage differences. During the integration phase, the compensation mechanism maintains accuracy while allowing the integrator to function. This dynamic operation allows the circuit to achieve high measurement precision without requiring permanently active complex compensation circuits for all operating conditions
Solution Approach 2:
The invention changes the voltage parameter at the input terminal of the integrator by using the first capacitor to reduce the voltage difference between the first voltage and second voltage. This parameter change (voltage stabilization) improves measurement precision by preventing current leakage through stray capacitors and maintaining constant transconductance, while the compensation is achieved through a targeted approach rather than comprehensive circuit redesign
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 effectively fixes the input voltage to a reference, ensuring accurate current measurement by minimizing voltage changes across the differential pair, thus maintaining high transconductance and gain, and ensuring the current flows directly into the sensor.
Implementation Method 1
The first capacitor is coupled between an output terminal of the voltage generation circuit and an output terminal of the first amplifier, and configured to reduce a voltage difference between the first voltage and the second voltage
Data Source
AI summary
A current sensor including a voltage generation circuit and a voltage integration circuit is provided. The voltage generation circuit is configured to generate a first voltage according to a current to be sensed. The voltage integration circuit is coupled to the voltage generation circuit and configured to receive the first voltage and a second voltage to generate an output voltage. The voltage integration circuit includes a first amplifier, a second amplifier and a first capacitor. The first amplifier is configured to receive the first voltage and the second voltage to generate a third voltage. The second amplifier is coupled to the first amplifier and configured to receive the third voltage to generate the output voltage. The first capacitor is coupled between an output terminal of the voltage generation circuit and an output terminal of the first amplifier and configured to reduce a voltage difference between the first voltage and the second voltage.