Zero-power wake-up sensing circuit in piezoelectric haptic feedback

Abstract

Provided is a piezoelectric circuit including: a piezoelectric actuator for generating a sensing signal in response to a force application and generating a haptic response in response to a haptic voltage signal; a driver circuit for generating a haptic voltage signal in response to the wake-up signal; a wake-up circuit which does not draw power when a force is not applied to the piezoelectric actuator and comprises a capacitor, a transistor and an output, wherein the capacitor is coupled to a piezoelectric brake, the transistor comprises a first terminal, a second terminal and a third terminal, the first terminal is capacitively coupled to the piezoelectric actuator through the capacitor to receive a sensing signal, the second terminal is connected to a voltage source, and the third terminal is connected to the ground, and wherein the transistor is turned on when the sensing signal is valid, and is output-connected to the second terminal for providing a wake-up signal to the actuator circuit when the transistor is turned on; and a feedback that includes a switch providing a ground path between the capacitor and the first terminal, where the switch is closed when the transistor is turned on.

Description

technical field [0001] The present invention relates to a wake-up circuit, and in particular to a wake-up circuit for a tactile feedback system including a piezoelectric actuator. Background technique [0002] The piezoelectric effect is a reversible process whereby when a force is applied to a piezoelectric material an electric charge is generated and when a charge is applied to the piezoelectric material a force is generated. Charge can be measured as a current or voltage and provides a good way of estimating the mechanical strain exerted on a material. An example application is the use of piezoelectric materials to replace mechanical switches. Thus, when a user presses on a button comprising piezoelectric material, a voltage / current is generated whereby this change in voltage / current can be detected by the electronic device which notifies the system that the user has pressed on the button. [0003] The reverse piezoelectric effect has the opposite result. When a voltag...

AI Technical Summary

Problems solved by technology

However, the resistive path reduces the sensitivity of the system by continuously discharging the piezoelectric actuator and reducing the signal amplitude

The second problem is that an active circuit is required to read the sensor, and that circuit requires a few microamps to milliamps of quiescent current and / or dynamic current to operate

In a system where the button is used several times a day, this demand for excess current leads to a lot of wasted power

Images