Relaxation Oscillator Delay Compensation for Precise Frequency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Relaxation oscillators face challenges in generating precise and stable oscillation frequencies due to propagation delays in comparator-based voltage detection, which vary with parameters like temperature, supply voltage, and process variations, affecting the accuracy of the oscillation period.
Innovation Solution
Incorporating a measuring device to determine the propagation delay and adjusting the charging rate of the capacitor device based on this measurement, either by increasing the charging current or reducing capacitance, to compensate for the delay and maintain an ideal oscillation period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a comparator is used to detect the threshold voltage, then the oscillation frequency can be determined, but the propagation delay of the comparator causes inaccuracy in the oscillation period
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor to a voltage level that anticipates the propagation delay. The capacitor is charged to a voltage Vpre = Vr + ΔV, where ΔV is calculated based on the expected propagation delay time and the charging current. This preliminary voltage adjustment ensures that when the comparator triggers after its propagation delay, the capacitor voltage is exactly at the threshold Vr, thereby compensating for the time loss and achieving precise oscillation frequency measurement.
2Measurement precision
If the propagation delay is compensated by increasing the charging current, then the oscillation period accuracy improves, but the energy consumption increases
Solution Approach 1:
The patent applies partial action by increasing the charging current only during the propagation delay period, not continuously. The charging current is set to a higher value Icharge = (Vr + ΔV) / (R * Tideal) only for the duration needed to compensate for the comparator delay, then returns to the normal operating current. This partial increase in charging current achieves the necessary period accuracy while minimizing the additional energy consumption compared to continuously operating at higher current.
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 effectively compensates for propagation delays, ensuring a stable and precise oscillation frequency by adjusting the charging rate, thereby reducing the impact of varying parameters on the oscillation period.
Implementation Method 1
a capacitor device coupled to the current source
Implementation Method 2
a detection device configured to detect when a voltage at the capacitor device reaches a threshold voltage
Data Source
AI summary
A method of operating a relaxation oscillator includes determining a measure of a propagation delay of a detection device of a relaxation oscillator and increasing a charging rate of a capacitor device of the relaxation oscillator for a time duration based on the determined measure of the propagation delay.