Clock Recovery Using Dual Oscillators After Battery Removal
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Solution Overview
Problem
Existing clock recovery systems in battery-powered devices fail to accurately maintain time count when the battery is removed, as they do not provide power to the oscillator during this period, leading to a gap in time counting.
Innovation Solution
A method and circuit design that utilizes a secondary oscillator to count pulses during battery removal, with the main oscillator resuming at a higher rate upon battery reinsertion to recover the time count, allowing for accurate duration matching of the recovery period without requiring knowledge of the secondary oscillator's frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the battery is removed from the device, then power consumption is reduced, but time counting is interrupted and time accuracy deteriorates
Solution Approach 1:
A second counter is introduced as an intermediary to temporarily store the time count value when the battery is removed. This intermediary counter preserves the time information during power interruption, and the first counter resumes counting after battery reinsertion, eliminating the time loss that would otherwise occur during battery removal.
2Loss of time
If a second oscillator is used to count pulses during battery removal, then time counting continues, but the frequency of the second oscillator is unknown making synchronization difficult
Solution Approach 1:
The first counter counts clock pulses at an increased rate (excessive action) during the recovery period after battery reinsertion. This accelerated counting compensates for the unknown frequency of the second oscillator, allowing the system to overtaken the time loss and synchronize with the correct time without requiring precise knowledge of the second oscillator's frequency characteristics.
3Use of energy by moving object
If the first counter resumes counting at normal rate after battery reinsertion, then power consumption is minimized, but the recovery time is extended and time synchronization is delayed
Solution Approach 1:
The counting rate of the first counter is made dynamic rather than static. During the recovery period after battery reinsertion, the first counter operates at an increased rate to quickly recover lost time. Once the recovery is complete, it returns to the normal counting rate to minimize power consumption. This dynamic adjustment of counting rate optimizes both power efficiency and time synchronization speed.
Data Source
AI summary
A battery powered device is able to maintain a clock value when the battery is removed for a short period. During a first time period, while the battery is in the device, clock pulses derived from a first oscillator are counted at a first rate in a first counter that represents the clock value. During a second time period following the first time period, while the battery is removed, the value of the first counter is maintained independent of any clock pulses derived from the first oscillator, clock pulses derived from a second low power oscillator are counted in a second counter. During a recovery time period following the second time period, clock pulses derived from the second oscillator are again counted in the second counter, while clock pulses derived from the first oscillator are counted in the first counter at a second rate higher than the first rate, the duration of the recovery time period being determined based on the number of pulses counted in the second counter during the second time period.