Crystal Oscillator Start-Up Circuit With Pulsed Parallel Current Boost
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Solution Overview
Problem
Crystal oscillator circuits experience prolonged start-up times, particularly in low-frequency circuits, due to low loop-gain, which is slower compared to high-frequency circuits.
Innovation Solution
Incorporating a second current source parallel to the first current source, driven by a pulse generation circuit that outputs a control pulse to enhance driving ability without altering loop-gain, and operates only during start-up to reduce start-up time while maintaining low-power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a single current source is used to drive the oscillator start-up circuit, then power consumption is kept low, but the start-up time becomes too long
Solution Approach 1:
The patent applies dynamics by making the current source configuration changeable over time. A first current source operates during normal operation for low power consumption, while a second current source is activated during start-up through a control circuit to provide stronger driving current. This dynamic switching between different current source configurations resolves the contradiction between low power consumption and fast start-up.
Solution Approach 2:
The patent implements periodic action through the control circuit that periodically activates the second current source only during the start-up phase. The control circuit detects the oscillation start-up condition and switches the current source configuration accordingly, applying strong current periodically during start-up and normal current during operation, thus achieving both fast start-up and low power consumption.
2Loss of time
If the loop-gain is increased to reduce start-up time, then start-up time decreases, but the circuit complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the current sourcing function into two separate current sources: a first current source for normal operation and a second current source for start-up. This segmentation allows each current source to be optimized for its specific function, with the second current source providing the additional loop-gain needed for fast start-up without requiring the entire circuit to be redesigned for high performance.
Solution Approach 2:
The control circuit acts as an intermediary that manages the switching between the first and second current sources. It detects the oscillation start-up condition and controls the activation of the second current source, thereby indirectly achieving the loop-gain increase needed for reduced start-up time without directly modifying the oscillator core circuitry.
3Loss of time
If a second current source is added in parallel to increase driving ability, then start-up time is reduced, but power consumption increases
Solution Approach 1:
The patent applies preliminary action by preparing the second current source to be activated only when needed during the start-up phase. The control circuit is configured to detect the initial oscillation condition and activate the second current source at the appropriate moment, providing the necessary driving current before the oscillation is fully established, then deactivating it to maintain low power consumption during normal operation.
Data Source
AI summary
A crystal oscillator circuit is provided. The crystal oscillator circuit includes an oscillator start-up circuit having a first output terminal and a second output terminal, where the second output terminal outputs a first oscillation signal; and a waveform conversion circuit configured to convert the first oscillation signal to a rectangular wave signal. The crystal oscillator circuit also includes a first current source configured to output a first current to drive the oscillator start-up circuit; and a second current source configured to output a second current, and being connected in parallel with the first current source to jointly drive the oscillator start-up circuit. Further the crystal oscillator circuit includes a pulse generation circuit configured to generate a control pulse signal to control the second current source to output the second current after power on and to stop outputting the second current after a preset time.