Capacitor Charging Circuit for Precise Time Measurement
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Solution Overview
Problem
Current methods for precise time and capacitance measurement require ultra-high frequency clocks and high power digital logic, leading to significant power consumption and circuit noise, making them inefficient for measuring short time periods and capacitance values.
Innovation Solution
A system and method using a constant current source, current steering switch, and analog-to-digital converter to measure time and capacitance with high resolution, independent of ultra-high frequency clocks, by charging a capacitor and converting the voltage to a digital representation for precise time and capacitance calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultra-high frequency clocks and high power digital logic are used to precisely measure short time periods, then measurement precision is improved, but power consumption increases and circuit noise increases
Solution Approach 1:
The patent replaces the mechanical/digital clock-based time measurement system with an analog voltage-based system. Instead of using ultra-high frequency digital clocks to count time intervals, the invention uses a capacitor charging circuit where the voltage increases linearly with time. The time period is determined by measuring the analog voltage level rather than counting digital clock cycles, thereby eliminating the need for high-power digital logic and ultra-high frequency clocks while achieving picosecond-level measurement precision.
2Measurement precision
If ultra-high frequency clocks are used to measure short time periods, then measurement precision is improved, but circuit noise increases
Solution Approach 1:
The patent substitutes the digital clock and counter system with an analog capacitor charging system. The linearly increasing voltage on the capacitor provides a continuous analog representation of time elapsed, which can be measured with high precision using voltage comparison techniques. This analog approach generates minimal circuit noise compared to the switching activity and harmonic content inherent in ultra-high frequency digital clock systems.
3Measurement precision
If digital logic circuits run at high clock speeds to measure short time periods, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex digital logic circuits with a simple analog RC charging circuit. The core measurement mechanism relies on the fundamental physical relationship between capacitor voltage, current, and time (V = I×t/C for constant current charging). This requires only a constant current source, a capacitor, and voltage measurement capability, eliminating the need for high-speed digital logic, clock distribution networks, and synchronous sampling circuits, thereby significantly reducing device complexity.
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
Enables precise time measurements to picoseconds resolution and capacitance measurements with low power consumption and reduced noise, extending dynamic time measurement range to better than one part per million, suitable for capacitive switch sensors.
Implementation Method 1
a capacitor coupled to the current steering switch, the capacitor having a known value of capacitance, wherein a voltage on the capacitor increases substantially linearly in time when the current steering switch couples the constant current source to the capacitor
Data Source
Figure 1~1B
Figure 2
Figure 3
AI summary
A time period of an event is determined by charging a known value capacitor from a constant current source during the event. The resultant voltage on the capacitor is proportional to the event time period and may be calculated from the resultant voltage and known capacitance value. Capacitance is measured by charging a capacitor from a constant current source during a known time period. The resultant voltage on the capacitor is proportional to the capacitance thereof and may be calculated from the resultant voltage and known time period. A long time period event may be measured by charging a first capacitor at the start of the event and a second capacitor at the end of the event, while counting clock times therebetween. Delay of an event is done by charging voltages on first and second capacitors at beginning and end of event, while comparing voltages thereon with a reference voltage.