Switched Capacitor Circuit With Leakage Error Correction
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Solution Overview
Problem
Variable-capacitance devices face challenges in achieving high accuracy due to leakage currents and parasitic capacitance, which affect capacitance stability and accuracy, especially when switching between different capacitance states.
Innovation Solution
Incorporating an error correction circuit that resets the voltage at the capacitance switching node to match the output terminal voltage during the OFF state of the capacitance selection switch, thereby eliminating leakage current effects and maintaining capacitance accuracy by resetting the charge in the first capacitance element before discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a capacitance selection switch is used to switch between capacitors, then capacitance can be changed after production, but leakage current flows through the switch causing capacitance inaccuracy
Solution Approach 1:
The error correction circuit performs preliminary action by resetting the voltage at the capacitance switching node to match the output terminal voltage before capacitance measurement or switching operations. This preemptive voltage equalization prevents leakage current from causing capacitance inaccuracy during subsequent operations.
Solution Approach 2:
The error correction circuit implements feedback by continuously monitoring and correcting voltage differences between the output terminal and capacitance switching node. When a voltage difference is detected, the circuit activates to equalize the voltages, thereby compensating for leakage current effects and maintaining capacitance accuracy.
2Stability of the object's composition
If the capacitance selection switch is in the OFF state, then the second capacitor is isolated, but leakage current still flows causing voltage difference and capacitance deviation
Solution Approach 1:
The error correction circuit creates equipotential conditions by equalizing the voltage at the capacitance switching node with the output terminal voltage. This voltage equalization eliminates the potential difference that drives leakage current, thereby preventing capacitance deviation even when the switch is in the OFF state.
Solution Approach 2:
The invention converts the harmful effect of leakage current into a beneficial correction mechanism. By detecting voltage differences caused by leakage current and actively compensating for them through the error correction circuit, the system transforms the leakage problem into an opportunity for enhanced capacitance accuracy through active error correction.
3Speed
If parasitic capacitance of the switch is considered, then switching speed may improve, but capacitance accuracy deteriorates due to voltage-dependent parasitic effects
Solution Approach 1:
The error correction circuit uses feedback to detect and compensate for voltage differences caused by parasitic capacitance effects. By continuously monitoring the voltage at the capacitance switching node and comparing it with the output terminal voltage, the circuit activates corrections only when needed, thereby maintaining accuracy without sacrificing switching speed.
Data Source
AI summary
A variable-capacitance device includes a first capacitance element coupled between a first power supply terminal and an output terminal, a capacitance selection switch that is turned on and off in accordance with a capacitance switching signal, a second capacitance element coupled in parallel to the first capacitance element and in series to the capacitance selection switch, and an error correction circuit configured to operate such that in a state in which the capacitance selection switch is in an OFF state, in response to a charge reset signal that causes a voltage at the output terminal to be reset to a reset voltage, the error correction circuit substantially eliminates a difference between the voltage at the output terminal and a voltage at a capacitance switching node at which the second capacitance element is coupled to the capacitance selection switch.