PWM-Switched Self-Oscillation Circuit for Stable Amplitude Control
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Solution Overview
Problem
Existing self-oscillation circuits for capacitive vibration type sensors require a variable-gain amplifier that complicates the interface between positive and negative feedback circuits, making it difficult to achieve low power consumption and increasing design man-hours, especially when implemented in ASICs.
Innovation Solution
A self-oscillation circuit configuration that eliminates the variable-gain amplifier by using a switch (SW circuit) and a pulse-width modulation (PWM) unit to control the positive feedback loop, allowing independent adjustment of the positive and negative feedback circuits and reducing design complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a variable-gain amplifier is used to control oscillation amplitude, then the oscillation amplitude can be controlled, but the interface between positive and negative feedback circuits becomes complicated and design complexity increases
Solution Approach 1:
The patent extracts the variable-gain amplifier from the feedback circuit interface and replaces it with a switch circuit controlled by PWM signals. This separation removes the complex gain control function from the interface between positive and negative feedback circuits, simplifying the overall system architecture while maintaining amplitude control capability through the PWM-controlled switch.
Solution Approach 2:
The patent introduces a PWM control signal as an intermediary between the negative feedback circuit and the positive feedback circuit. Instead of directly controlling gain through a variable-gain amplifier, the PWM signal mediates the control by switching the positive feedback path on and off, thereby controlling oscillation amplitude without complicating the circuit interface.
2Reliability
If a variable-gain amplifier is used in the feedback circuit, then oscillation amplitude can be controlled, but power consumption increases and ASIC integration becomes difficult
Solution Approach 1:
The patent removes the power-hungry variable-gain amplifier from the system and replaces it with a switch circuit that consumes minimal power. The switch circuit is controlled by PWM signals generated through digital processing, which significantly reduces power consumption compared to analog variable-gain amplifier operation.
Solution Approach 2:
The patent replaces the analog variable-gain amplifier mechanism with a digital PWM control mechanism. By using digital switching instead of analog gain control, the system achieves amplitude control with much lower power consumption and better suitability for ASIC integration.
3Reliability
If a variable-gain amplifier is used to control oscillation amplitude, then the oscillation can be maintained, but design man-hours increase due to interface complexity
Solution Approach 1:
By extracting the variable-gain amplifier and replacing it with a simple switch circuit, the patent eliminates the need for complex interface design between feedback circuits. This reduction in interface complexity directly decreases design man-hours while maintaining oscillation stability through the PWM-controlled switch.
Solution Approach 2:
The patent changes the control parameter from analog gain control to digital PWM duty cycle control. This parameter change simplifies the design process by allowing standard digital control techniques to be used instead of complex analog interface design, thereby reducing design time and man-hours.
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
This configuration simplifies the interface between the positive and negative feedback circuits, reduces design man-hours, and facilitates low power consumption, enabling easier integration into ASICs while maintaining stable oscillation amplitude control.
Implementation Method 1
the vibrator 511 vibrates in accordance with the potential change of the first fixed electrode 512... Such positive feedback circuit allows the vibrator 511 to vibrate at its own resonance frequency
Data Source
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AI summary
A self-oscillation circuit includes a vibration unit having a vibrator, a positive feedback path which positively feeds back a signal based on vibration of the vibrator to the vibration unit, a negative feedback circuit which generates a pulse-width-modulated signal having a frequency lower than a vibration frequency of the vibrator, based on a comparison result between a value corresponding to an amplitude of the vibrator and a reference value, and a switch circuit which switches connection and disconnection of the positive feedback path to the vibration unit by the pulse-width-modulated signal.