MEMS Microactuator Actuation Signal for Bounce Suppression

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Solution Overview

Problem

MEMS switches experience bouncing and ringing issues during actuation, leading to degraded circuit performance and reduced operating life, especially under varying process conditions and operating conditions, which existing techniques fail to adequately address using simple waveforms and circuits.

Innovation Solution

A control circuitry system that generates actuation signals with a positive slope of lowest possible magnitude for closing and a controlled decrease in actuation signal to minimize bouncing and ringing, ensuring compliance with predetermined specifications and natural frequencies to manage momentum and energy dissipation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a simple actuation waveform is used, then device complexity is reduced, but bouncing and ringing issues occur leading to degraded performance

Engineering Contradiction:

Improveactuation waveform complexityVSAvoidswitch performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies preliminary action by pre-charging the actuator electrode to a first voltage level before actuation, and pre-discharging to a second voltage level before release. This preliminary preparation of electrical states enables controlled momentum management during switching, reducing bounce and ring effects without requiring complex real-time control waveforms.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes voltage parameters dynamically - using different voltage levels (first voltage, second voltage, third voltage) at different stages of actuation. By varying the electrical parameters (voltage magnitude and polarity) rather than using complex waveform shapes, the system achieves reliable switching with simple control circuitry.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If actuation speed is increased, then productivity is improved, but momentum increases causing more bouncing and contact damage

Engineering Contradiction:

Improveswitching speedVSAvoidcontact bounce and wear

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful momentum generated during rapid actuation into a beneficial controlled descent. By pre-charging the actuator and using capacitive discharge, the stored electrical energy is converted to mechanical energy in a controlled manner, allowing fast switching while the momentum is dissipated through the electrical circuit rather than causing damaging contact bounce.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent replaces mechanical momentum control with electrical field control. Instead of mechanically damping the cantilever motion, the system uses electrical charging and discharging of the actuator electrode to control the force profile, substituting electrical energy management for mechanical impact control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of time

If actuation signal is abruptly changed, then response time is reduced, but ringing occurs increasing settling time

Engineering Contradiction:

Improveactuation response timeVSAvoidringing duration

Core Design Contradiction:

Loss of timeVSDuration of action of moving object

Solution Approach 1:

The patent employs periodic action through the natural oscillation of the RC circuit formed by the actuator capacitance and series resistance. The charging and discharging cycles of this circuit naturally provide a time-extended voltage transition that reduces abrupt changes, allowing fast initial response while the periodic decay of the RC circuit gradually dissipates energy and reduces ringing duration.

Inventive Principle:

Principle #19Periodic 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 reduces bouncing and ringing, enhancing the operating life and performance of MEMS switches by ensuring controlled and efficient actuation and release processes, even under process variations and different operating conditions.

Implementation Method 1

an electrostatic voltage is applied to the actuator plate 28. The presence of the electrostatic voltage over time creates a force that moves the metallic cantilever 16 toward the actuator plate 28

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Implementation Method 2

decrease the actuation signal from the second state to the first state to dissipate energy stored in the movable member and minimize any bouncing of the movable member

Methodology Applied

Scientific EffectEnergy dissipation: Damping

Data Source

PatentUS9159516B2Actuation signal for microactuator bounce and ring suppression

Publication Date: 2015.10.13 QORVO US INC

AI summary

The present disclosure provides a system and method for controlling positioning of a movable member of a MEMS microactuator to reduce bouncing and ringing. The system includes control circuitry in communication with the MEMS microactuator. The control circuitry is adapted to linearly increase an actuation signal from a first state to a second state to urge the movable member from a first position to a second position and hold the movable member in the second position. The control circuitry is further adapted to linearly decrease the actuation signal from the second state to the first state to release the movable member to the first position. A transition time is not less than the inverse of one quarter of a natural frequency of the movable member as the movable member moves to the first position.