Condenser Microphone Diaphragm Collapse Detection and Control

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Solution Overview

Problem

Condenser microphones often enter an undesired collapsed state due to high sound pressure levels or mechanical shocks, leading to operational interruptions, and existing solutions lack effective collapse detection and control mechanisms.

Innovation Solution

A condenser microphone with a collapse detection element that determines the separation between the diaphragm and back-plate and a collapse control element that adjusts the DC bias voltage to prevent or remedy collapse, using electronic circuits and sensors to maintain optimal separation and prevent irreversible collapse.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the DC bias voltage is increased to improve the electrostatic force between diaphragm and back-plate, then the microphone sensitivity is improved, but the risk of diaphragm collapse increases under high sound pressure levels

Engineering Contradiction:

Improvemicrophone sensitivityVSAvoiddiaphragm collapse risk

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where a detection element continuously monitors the separation distance between the diaphragm and back-plate. When collapse is detected or anticipated, the control element automatically adjusts the DC bias voltage to prevent or remedy the collapsed state, creating a closed-loop control system that dynamically maintains reliable operation while preserving sensitivity

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent dynamically changes the DC bias voltage parameter based on real-time detection of diaphragm separation. By adjusting this electrical parameter in response to mechanical conditions, the system optimizes the electrostatic force to prevent collapse while maintaining measurement precision during normal operation

Inventive Principle:

Principle #35Parameter changes

2Reliability

If mechanical countermeasures are used to restrict maximum diaphragm deflection to prevent collapse, then the diaphragm is protected from collapse, but the device complexity increases

Engineering Contradiction:

Improvediaphragm collapse preventionVSAvoidmechanical countermeasure structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical countermeasures with an electronic control system. Instead of using mechanical structures to physically restrict diaphragm deflection, the system uses a detection element and control circuitry that electronically adjusts the DC bias voltage to prevent collapse, thereby reducing mechanical complexity while maintaining reliability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If the DC bias voltage is completely removed to remedy collapsed state, then the diaphragm is released from the back-plate, but the microphone operation is interrupted

Engineering Contradiction:

Improvecollapse recoveryVSAvoidoperation interruption time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by detecting the approaching collapsed state through the detection element and proactively adjusting the DC bias voltage before complete collapse occurs. This preventive approach allows the diaphragm to be released from the back-plate with minimal or no interruption to microphone operation, as the voltage adjustment is initiated before the collapsed state fully develops

Inventive Principle:

Principle #10Preliminary action

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 prevents microphone collapse during high sound pressure levels or mechanical shocks, ensuring continuous operation without the need for power supply removal, with the ability to quickly recover from collapsed states, minimizing sound interruptions.

Implementation Method 1

an attractive force originating from a DC electrical field provided between the diaphragm and the back-plate

Methodology Applied

Scientific EffectDC electrical field: Electric Field

Implementation Method 2

the force originating from an impinging sound pressure is combined with an attractive force originating from a DC electrical field

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Implementation Method 3

A collapse detection element is adapted to determine a physical parameter value related to a separation between the diaphragm and the back-plate

Methodology Applied

Scientific EffectCapacitance measurement: Capacitance

Implementation Method 4

both have been treated with a non-conducting anti-sticktion coating which will prevent Van der Waal forces from keeping the diaphragm sticking

Methodology Applied

Scientific EffectVan der Waal forces: Van der Waals Force

Data Source

PatentUS7548626B2Detection and control of diaphragm collapse in condenser microphones

Publication Date: 2009.06.16 INVENSENSE INC

AI summary

A condenser microphone is provided having a transducer element. A diaphragm has an electrically conductive portion. A back-plate has an electrically conductive portion. A DC bias voltage element is operatively coupled to the diaphragm and the back-plate. A collapse detection element is adapted to determine a physical parameter value related to a separation between the diaphragm and the back-plate. A collapse control element is adapted to control the DC bias voltage element based on the determined physical parameter value.