Crystal Oscillator Current Switching for Low-Power Frequency Stability
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Solution Overview
Problem
Existing crystal oscillator circuits face challenges in achieving low power consumption while maintaining stable frequency output over long-term operation, as higher transconductance is required for stability but increases power consumption.
Innovation Solution
The proposed low power crystal oscillator circuit incorporates a crystal electrically coupled with a resistor, capacitors, and transistors forming an oscillator. It utilizes current mirror transistors to amplify current efficiently, with a current limiting circuit and automatic amplitude detection to reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher transconductance is used to maintain stable frequency output, then frequency stability is improved, but power consumption increases
Solution Approach 1:
The patent implements dynamic transconductance adjustment by switching between a first transistor with higher transconductance for startup and a second transistor with lower transconductance for steady-state operation. This dynamic reconfiguration allows the system to optimize between frequency stability during startup and power consumption during normal operation, directly resolving the contradiction between maintaining stable frequency output and reducing power consumption.
Solution Approach 2:
The patent applies preliminary action by using the first transistor with higher transconductance to establish stable oscillation before switching to the second transistor with lower transconductance. This preliminary high-transconductance phase ensures reliable frequency stability is achieved first, then the system transitions to a lower power consumption state, effectively resolving the contradiction by sequencing the transconductance levels appropriately.
2Use of energy by moving object
If lower transconductance is used to reduce power consumption, then power consumption is reduced, but frequency stability and tolerance for errors deteriorate
Solution Approach 1:
The system dynamically switches between two transconductance levels based on operational phase. During startup, higher transconductance ensures frequency stability; during steady-state operation, lower transconductance reduces power consumption while maintaining adequate stability. This dynamic approach resolves the contradiction by applying the appropriate transconductance level at the appropriate time.
Solution Approach 2:
The patent employs periodic action by alternating between high and low transconductance states. The first transistor provides high transconductance during startup phase, then the system transitions to the second transistor for sustained low-power operation. This periodic switching pattern allows the system to achieve frequency stability when needed and reduce power consumption during normal operation.
Data Source
AI summary
A low power crystal oscillator circuit has a high power part and a low power part. Crystal oscillation is initialized using the high power part. An automatic amplitude control circuit includes a current subtractor that decreases current in the high power part as an amplitude of the crystal oscillation increases. A current limiting circuit may limit current in the low power part in order to further reduce power consumption by the low power crystal oscillator circuit. Additionally, an automatic amplitude detection circuit may turn off the high power part after the amplitude of the crystal oscillation reaches a predetermined level in order to further reduce power consumption of the low power crystal oscillator circuit, and may turn back on the high power part after the amplitude of the crystal oscillation reaches a second predetermined level in order to maintain the crystal oscillation.