Piezoelectric Haptics Low Voltage Sensing via Transformer Isolation
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Solution Overview
Problem
Existing haptic systems using piezoelectric actuators face a challenge in sensing force while the actuator is driven with a high-voltage signal, as low-voltage components in the sensing path must be protected from high voltages, typically requiring a switch to disconnect the sensing path, which prevents continuous sensing during actuation.
Innovation Solution
A circuit comprising a high-voltage amplifier, driver circuit, feedback circuit, sense resistor, signal conditioning circuit, and analog-to-digital converter allows for continuous force sensing on a high-voltage haptic actuator by using capacitive coupling and feedback loops to manage voltage differences, enabling the detection of pressure applied to the actuator without disconnecting the sensing path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a switch is used to disconnect the sensing path during high-voltage drive, then low-voltage components are protected from high voltage damage, but continuous sensing is prevented and sensing capability is lost during actuation
Solution Approach 1:
The patent introduces a transformer as an intermediary device between the high-voltage drive circuit and the low-voltage sensing circuit. The transformer provides galvanic isolation while allowing magnetic coupling of the drive signal through to the sensing path, enabling continuous sensing without direct electrical connection that would expose low-voltage components to high voltage damage
Solution Approach 2:
The patent segments the sensing path into isolated sections using the transformer, separating the high-voltage drive domain from the low-voltage sensing domain. This allows the sensing circuit to operate independently at low voltage while the drive circuit operates at high voltage, with the transformer acting as the boundary between segments
2Productivity
If the sensing path remains connected during high-voltage drive, then continuous sensing is enabled, but low-voltage components are exposed to high voltage damage
Solution Approach 1:
The transformer serves as a protective intermediary that blocks high voltage from reaching low-voltage components while still allowing the sensing function to operate continuously. The magnetic coupling mechanism transfers the drive signal waveform to the sensing side without transmitting harmful high voltage energy
Solution Approach 2:
The patent converts the potentially harmful high-voltage signal into a useful sensing signal by using the transformer to extract only the necessary waveform information while blocking the harmful high voltage energy. The high voltage drive signal becomes the source of the sensing signal through magnetic induction
3Force
If high-voltage signals are used to drive the piezoelectric actuator, then sufficient physical displacement is generated for effective haptic feedback, but the voltage level becomes incompatible with standard low-voltage sensing circuits
Solution Approach 1:
The transformer acts as an intermediary that bridges the voltage level incompatibility between the high-voltage drive path and low-voltage sensing path. It allows the high-voltage drive signal to generate sufficient actuator displacement while simultaneously providing a scaled-down version of the signal for safe sensing operations
Solution Approach 2:
The transformer provides multi-functionality by simultaneously enabling high-voltage drive signal transmission to the actuator and low-voltage sensing signal generation for the sensing circuit, making the system compatible with standard low-voltage electronics while maintaining effective haptic output
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 continuous force sensing during high-voltage actuation, allowing for smooth haptic feedback without glitches, as the system effectively processes voltage differences to determine the level of force applied, even when the actuator is driven with high-voltage signals.
Implementation Method 1
Piezoelectric materials may generate a mechanical response when an electric charge is applied across the material
Implementation Method 2
A signal conditioning circuit may have a first input capacitively coupled to the output of the high-voltage amplifier and a second input capacitively coupled to the piezoelectric actuator
Data Source
AI summary
A device includes a high-voltage amplifier to amplify a bursted signal and may couple to a driver circuit to drive a piezoelectric actuator. During the on-time of the bursted signal, a feedback circuit may compensate for non-idealities in the system and may equalize the signal at the actuator and the output of the high-voltage amplifier. During the off-time of the bursted signal, a signal conditioning circuit may sense a difference signal between the signal at the actuator and the signal at the high-voltage amplifier output and may interpret this difference signal as pressure applied to the piezoelectric actuator.