Piezoelectric Haptic Interface With Overcurrent Protection Circuit

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Solution Overview

Problem

Haptic interfaces using piezoelectric bodies face challenges in simultaneously providing haptic outputs and sensing haptic inputs due to the significant difference in signal magnitudes, which can damage sensing circuits without proper protection.

Innovation Solution

Incorporating an overcurrent protection circuit within the control circuit to limit current flow into the sensing portion while the actuation portion charges the piezoelectric body, allowing for simultaneous haptic actuation and sensing by protecting the sensing circuit from excessive currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the haptic actuator circuit charges the piezoelectric body to provide haptic output, then the haptic output is delivered, but the current flow into the haptic sensor circuit becomes excessive and may damage the sensing circuit

Engineering Contradiction:

Improvehaptic output deliveryVSAvoidexcessive current damage to sensing circuit

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The control circuit is segmented into distinct functional portions: an actuator portion for charging the piezoelectric body and a sensor portion for sensing haptic inputs. The overcurrent protection circuit is selectively coupled to the sensor portion to limit current flow only when needed, allowing both portions to operate independently without mutual interference.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The overcurrent protection circuit acts as an intermediary between the actuator circuit and the sensor circuit. It monitors and limits the current flow into the sensor portion during actuation, preventing the harmful high currents from damaging the sensing circuit while allowing normal operation of both circuits.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the haptic sensor circuit monitors haptic inputs continuously, then haptic input detection is improved, but the sensing circuit may be damaged by high current during actuation

Engineering Contradiction:

Improvehaptic input detectionVSAvoidsensing circuit durability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The coupling of the overcurrent protection circuit to the haptic sensor portion is dynamic rather than static. The protection circuit is selectively activated during actuation phases when high currents are present and can be disengaged or reduced when not needed, allowing the sensor circuit to maintain high measurement precision while being protected from damage only when necessary.

Inventive Principle:

Principle #15Dynamics

3Reliability

If separate circuits are used for actuation and sensing, then circuit protection is improved, but device complexity increases

Engineering Contradiction:

Improvecircuit protectionVSAvoidcontrol circuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The control circuit is designed with multi-functionality where a single integrated control circuit performs both actuation and sensing functions. The overcurrent protection mechanism is integrated into this unified circuit rather than requiring completely separate protected circuits, reducing overall device complexity while maintaining reliable protection for the sensing portion during actuation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Enables the monitoring of haptic inputs during haptic output delivery, preventing damage to the sensing circuit and ensuring reliable operation of haptic interfaces in electronic devices.

Implementation Method 1

A piezoelectric body may also, or alternatively, convert electrical energy into mechanical energy using what has been referred to as the inverse piezoelectric effect. Conversion of electrical energy into mechanical energy can be used to actuate a piezoelectric body

Methodology Applied

Scientific EffectInverse piezoelectric effect: Piezoelectric Effect

Implementation Method 2

A piezoelectric material (or piezoelectric body) may be used to convert mechanical energy into electrical energy using what has been referred to as the direct piezoelectric effect. Conversion of mechanical energy into electrical energy can be used to sense a mechanical force or pressure on, or displacement of, a piezoelectric body

Methodology Applied

Scientific EffectDirect piezoelectric effect: Piezoelectric Effect

Data Source

PatentUS10622538B2Techniques for providing a haptic output and sensing a haptic input using a piezoelectric body

Publication Date: 2020.04.14 APPLE INC

AI summary

Haptic interfaces are described. One haptic interface includes a piezoelectric body and first and second electrodes coupled to the piezoelectric body. The haptic interface also includes a control circuit. The control circuit includes a haptic actuator, a haptic sensor circuit, and an overcurrent protection circuit. The haptic actuator circuit is coupled to the first electrode and configured to charge the piezoelectric body. The charging causes the piezoelectric body to provide a haptic output. The haptic sensor circuit is coupled to the second electrode and configured to sense an electrical change at the second electrode. The electrical change is related to a haptic input received by the piezoelectric body. The overcurrent protection circuit is coupled to the second electrode and configured to limit a current flow into the haptic sensor circuit while the haptic actuator circuit is charging the piezoelectric body.