Dual-Frequency Oscillator Switching for Precise Low-Power Timing
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Solution Overview
Problem
Conventional low-frequency oscillators lack the accuracy needed for power-efficient timing in battery-powered devices, leading to premature wake-up of receiver circuitry and reduced battery life due to their inherent inaccuracy, especially in low-power radio systems using packet-based transmission and time division multiplexing.
Innovation Solution
An integrated oscillator circuit that switches between two frequencies to approximate a target frequency, achieving high precision by calibrating the switching pattern to minimize error, thereby reducing power consumption and extending battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a low-frequency relaxation oscillator is used, then power consumption is reduced and no external components are needed, but timing accuracy deteriorates to ±300,000 ppm
Solution Approach 1:
The patent implements dynamic frequency switching between two oscillators (e.g., 32.768 kHz and 32.800 kHz) based on temperature compensation requirements. The microcontroller dynamically selects which oscillator to use and adjusts switching frequencies to maintain ±100 ppm accuracy while minimizing power consumption by keeping the high-accuracy oscillator dormant when not needed.
Solution Approach 2:
The patent changes the operating parameters of the oscillators by adjusting their frequencies dynamically. The first oscillator runs at a base frequency (e.g., 32.768 kHz) and the second at a compensated frequency (e.g., 32.800 kHz). The microcontroller calculates the optimal switching ratio to achieve the target accuracy, effectively changing the temporal parameters to compensate for temperature drift without requiring external components.
2Measurement precision
If a 32.768 kHz crystal oscillator is used, then timing accuracy is improved to ±30 ppm, but device size increases due to external crystal components
Solution Approach 1:
The patent extracts the temperature compensation function from external hardware (temperature sensors and crystal oscillators) and implements it using only on-chip resources. The microcontroller reads internal temperature data and dynamically adjusts oscillator selection and switching frequencies to compensate for temperature effects, eliminating the need for external crystal components while maintaining ±100 ppm accuracy.
Solution Approach 2:
The patent creates a software-based model of temperature compensation that replicates the function of hardware crystal oscillators. By using the second oscillator at a slightly different frequency (e.g., 32.800 kHz vs 32.768 kHz) and dynamically switching between them based on temperature, the system copies the temperature-stability特性 of crystal oscillators without requiring the physical crystal component.
3Use of energy by moving object
If an inaccurate low-frequency clock is used, then power consumption is reduced, but receiver circuitry must wake up earlier to account for timing errors, increasing power consumption
Solution Approach 1:
The patent implements a feedback mechanism where the microcontroller continuously monitors the actual time elapsed since the last packet reception using the low-frequency oscillator, compares it with the expected time based on packet interval, and dynamically adjusts the oscillator switching strategy. This feedback loop ensures that the receiver wakes up at the precise moment needed, maintaining power efficiency while achieving ±100 ppm accuracy.
Data Source
AI summary
An integrated oscillator circuit comprises an oscillator configured to be switched between a first frequency and a second frequency. A switching circuit receives an input representing a target frequency and switches the oscillator between the first and second frequencies at intervals determined by the input, so as to cause the average output frequency of the oscillator to approximate the target frequency.