Oscillator Drive Circuit With Phase Feedback and AGC Stability

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Solution Overview

Problem

Conventional physical quantity sensors face challenges in stabilizing the driving and oscillation of oscillators due to unwanted components in the monitor signals, leading to unstable frequency control and amplitude regulation.

Innovation Solution

A drive circuit is configured with a drive signal generating unit, phase difference detector, frequency controller, and automatic gain control (AGC) unit to adjust the drive frequency and amplitude of the drive signal based on phase differences and monitor signal amplitudes, ensuring stable oscillation and precise physical quantity detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional drive circuits are used to drive the oscillator, then the oscillator can be driven, but the frequency control and amplitude regulation become unstable due to unwanted components in monitor signals

Engineering Contradiction:

Improvestability of oscillationVSAvoidprecision of frequency control

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The band-pass filter extracts the desired oscillation frequency component from the monitor signal by removing unwanted frequency components. This isolation of the fundamental oscillation signal eliminates interference from harmonics and noise, enabling stable frequency control and amplitude regulation.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The drive circuit uses feedback mechanisms where the monitor signal is continuously processed through the band-pass filter, phase difference detector, and AGC unit. The filtered signal provides accurate feedback about the actual oscillation state, allowing the system to automatically adjust drive frequency and amplitude to maintain stable operation.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If continuous operation of ADC, phase difference detector, and AGC unit is used, then precise control is achieved, but power consumption increases

Engineering Contradiction:

Improveprecision of physical quantity detectionVSAvoidpower consumption of drive circuit

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The ADC, phase difference detector, and AGC unit operate intermittently in periodic cycles rather than continuously. During each cycle, these components are activated for a predetermined period to perform measurements and adjustments, then deactivated. This periodic operation maintains detection precision while significantly reducing average power consumption of the drive circuit.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS10848159B2Drive circuit, physical quantity sensor, and electronic device

Publication Date: 2020.11.24 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A drive circuit is configured to drive an oscillator to vibrate the oscillator that outputs a monitor signal according to a physical quantity. The drive circuit includes a drive signal generating unit that generates a drive signal having a drive frequency, a phase difference detector that detects a phase difference between the monitor signal and the drive signal, a frequency controller that controls the drive frequency based on the phase difference, automatic gain control (AGC) unit that controls an amplitude of the drive signal according to an amplitude of the monitor signal, and an output unit that outputs the drive signal having the controlled amplitude to the oscillator. This drive circuit can stably drive and vibrate the oscillator.