Oscillation Circuit With Threshold Switching for 50% Duty Cycle
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Solution Overview
Problem
Conventional quartz oscillation systems face duty cycle deviations due to transistor gate leakages in advanced manufacturing processes, necessitating complex frequency doublers that increase circuit area and introduce noise, which are not suitable for high-speed, high-frequency circuits.
Innovation Solution
An oscillation circuit with an amplifier, feedback resistor, and switch circuit that automatically calibrates duty cycle by conducting a switch circuit in response to voltage differences between input and output voltages, using transistors with threshold-based on-state resistance to stabilize DC bias voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a frequency doubler is used to calibrate the duty cycle of the oscillation signal, then the duty cycle calibration capability is improved, but the circuit area increases and more noises are introduced
Solution Approach 1:
The patent extracts the duty cycle calibration function from the complex frequency doubler structure and implements it through a simplified switch circuit connected in parallel with the feedback resistor. The switch circuit only activates when voltage difference exceeds a threshold, providing calibration without the full frequency doubling functionality, thus reducing circuit area while maintaining calibration capability.
Solution Approach 2:
The patent changes the operating parameter by using a voltage difference threshold to control the switch circuit activation. Instead of continuously operating a complex frequency doubler, the system monitors the voltage difference between input and output nodes and only engages the calibration mechanism when the deviation exceeds the threshold, reducing overall circuit complexity and noise while maintaining calibration effectiveness.
2Measurement precision
If a frequency doubler is used to calibrate the duty cycle of the oscillation signal, then the duty cycle calibration capability is improved, but more noises are introduced
Solution Approach 1:
The patent extracts only the essential duty cycle calibration function from the frequency doubler, implementing it through a simple switch circuit that activates based on voltage difference threshold. This extracted approach provides calibration capability without introducing the additional noise associated with full frequency doubling operation.
Solution Approach 2:
The patent implements a feedback mechanism where the switch circuit continuously monitors the voltage difference between the input and output nodes of the amplifier. When the voltage difference exceeds the threshold, indicating duty cycle deviation, the switch circuit activates to correct the deviation, providing continuous noise-free calibration without the need for complex frequency doubling feedback paths.
3Speed
If transistors are decreased in size to realize high-speed and high-frequency circuits, then the circuit speed and frequency are improved, but gate leakages increase causing duty cycle deviation
Solution Approach 1:
The patent implements a self-service mechanism where the switch circuit automatically detects and corrects duty cycle deviations caused by transistor gate leakages. The circuit monitors its own operating state through voltage difference detection and self-corrects without external intervention, maintaining reliability in high-speed circuits with small transistors.
Solution Approach 2:
The patent employs feedback through the switch circuit that continuously monitors the voltage difference between input and output nodes. When gate leakage causes duty cycle deviation exceeding the threshold, the feedback mechanism activates the switch to correct the deviation, maintaining duty cycle stability despite the use of small transistors for high-speed operation.
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
The solution effectively stabilizes the duty cycle at 50% without increasing circuit area or introducing noise, addressing transistor leakage issues in high-speed, high-frequency quartz oscillation systems.
Implementation Method 1
The first switch circuit is configured to conduct the input terminal and the output terminal to each other when a voltage difference between an input voltage and an output voltage of the oscillation signal meets a threshold condition
Implementation Method 2
the amplifier is configured to invert and to amplify an oscillation signal received from the input terminal to provide an output oscillation signal at the output terminal
Implementation Method 3
The feedback resistor is coupled between the input terminal and the output terminal
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An oscillation circuit (10) including an amplifier (11), a feedback resistor (Rf) and a first switch circuit (12) is provided. The amplifier inverts and amplifies an oscillation signal (Cr) received from an input terminal (XI) thereof to provide an output oscillation signal (Ou) at an output terminal (XO) thereof. The feedback resistor is coupled between the input terminal (XI) and the output terminal (XO), and coupled with the first switch circuit in parallel. The first switch circuit conducts the input terminal to the output terminal in one of the following situations: (1) an input voltage of the oscillation signal is higher than an output voltage of the output oscillation signal by at least a first threshold value; and (2) the output voltage is higher than the input voltage by at least a second threshold value. The first switch circuit has a first on-state resistance smaller than a resistance of the feedback resistor.