Comparator Threshold Correction Using Variable Capacitor Feedback
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Solution Overview
Problem
Comparator circuits face challenges in accurately adjusting threshold voltages due to manufacturing dispersion and variations in capacitance values of variable capacitors, leading to offset voltages and difficulties in achieving desired voltage levels.
Innovation Solution
A comparator circuit configuration that includes a variable capacitor, an input voltage control circuit to generate a common voltage, and a correction circuit to control the capacitance values of the variable capacitor, ensuring the output voltage reverses at specific voltage differences and equalizes capacitance value differences to a predetermined capacitance value, thereby stabilizing the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a variable capacitor is connected to the output terminal of the comparator circuit to adjust the threshold voltage, then the threshold voltage can be adjusted to a desired voltage, but manufacturing dispersion causes the threshold voltage to become dispersed and produces offset voltage
Solution Approach 1:
The patent implements a feedback mechanism where the comparator circuit's output is fed back through the variable capacitor to the input side. This feedback loop allows the circuit to automatically compensate for manufacturing dispersion by adjusting the common voltage based on the actual output state, thereby correcting offset voltages and ensuring consistent threshold voltage across different devices.
Solution Approach 2:
The patent changes the electrical parameters (voltage levels) applied to the input terminals of the comparator circuit. By applying different common voltages to both input terminals while maintaining a specific voltage difference, the circuit can compensate for manufacturing variations. This parameter change approach allows the threshold voltage to be adjusted and stabilized without requiring precise physical dimensions of the variable capacitor.
2Adaptability or versatility
If the capacitance value of the variable capacitor is varied to adjust the threshold voltage, then the threshold voltage changes, but the variation amount of threshold voltage becomes dispersed due to manufacturing dispersion
Solution Approach 1:
The feedback connection through the variable capacitor allows the circuit to sense its own output state and automatically adjust the common voltage accordingly. This self-correcting mechanism compensates for manufacturing dispersion in the variable capacitor's capacitance value, ensuring that the threshold voltage adjustment remains accurate and uniform across different devices even when the physical capacitor values vary.
Solution Approach 2:
The patent applies the same common voltage to both input terminals of the comparator circuit, creating an equipotential condition for the common mode signal. This approach ensures that manufacturing variations in the variable capacitor affect both inputs equally, allowing the voltage difference (which determines the threshold) to remain consistent and predictable despite variations in absolute capacitance values.
Data Source
AI summary
A comparator has a comparator circuit to output an output voltage based on a voltage difference between a first and second input voltage, a variable capacitor connected to an output terminal, an input voltage control circuit to generate a common voltage and add the common voltage to the first and the second input voltages, and a correction circuit to control the variable capacitor to control the common voltage. The correction circuit controls a first capacitance value of the variable capacitor so that the output voltage is reversed when the voltage difference equals a first voltage difference, and controls a second capacitance value of the variable capacitor so that the output voltage is reversed when the voltage difference equals a second voltage value, and controls the common voltage so that a difference between the first capacitance value and the second capacitance value becomes equal to a predetermined capacitance value.