SYSTEM AND METHOD FOR LOW-VOLTAGE MEASUREMENT IN PIEZOELECTRIC HAPTICS

Abstract

A device (100) includes a high-voltage amplifier (120) for amplifying a burst signal (115) and is coupled to a driver circuit (128) to control a piezoelectric actuator (150). During the on-time of the burst signal, a feedback circuit (190) can compensate for non-idealities in the system and balance the signal at the actuator and the output of the high-voltage amplifier. During the off-time of the burst signal, a signal conditioning circuit (160) can detect a differential signal between the signal at the actuator and the signal at the high-voltage amplifier output and interpret this differential signal as pressure exerted on the piezoelectric actuator.

Description

PRIORITY

[0001] This application claims priority over jointly held US patent application No. 63 / 457,233, which was filed on April 5, 2023, the entire contents of which are hereby incorporated by reference for all purposes. AREA OF INVENTION

[0002] The present disclosure relates to systems and methods for sensing in applications that use a piezoelectric element for haptics. BACKGROUND

[0003] Piezoelectric materials can generate a mechanical response when an electrical charge is applied to them. A piezoelectric material that functions in this way can be called a piezoelectric actuator. Piezoelectric actuators can be used in haptic applications. In haptic applications, a user can perceive this mechanical response as a tactile sensation. An electrical charge applied to the piezoelectric actuator can cause it to vibrate. In a haptic application, applying signals of different voltages and frequencies can result in different vibration responses. These different responses can be perceived by a user as a button press, switch flip, or other physical reactions.

[0004] Haptics can be used in automotive applications as part of a steering wheel or console surface on a touchscreen. Physical buttons can be replaced by a piezoelectric actuator and a force sensor.

[0005] A piezoelectric actuator can be modeled as a capacitor. To generate sufficient physical displacement of the actuator, it must be driven by a high-voltage signal. Typical drive voltages can exceed 100 volts.

[0006] In a haptic application, a piezoelectric actuator can also be used as a sensor element. In one of several applications, a user can exert force on the piezoelectric actuator, which can be detected as a voltage. Such applications include both a control path and a sensing path. The control path generates the high-voltage signal to drive the piezoelectric actuator, and the sensing path detects the pressure exerted by the user. The sensing path is a low-voltage path that detects small changes in current, voltage, or capacitance when the user applies touch pressure to the actuator.

[0007] During the time the high-voltage signal drives the piezoelectric actuator, all low-voltage components in the measurement path must be protected from the high voltages at the actuator. In one of several examples, a switch can disconnect the connection between the measurement path and the actuator while the high-voltage signal drives the piezoelectric actuator. In this case, no data acquisition takes place while the actuator is driven by a high-voltage signal.

[0008] There is a need for a system that enables data acquisition in the measuring range while the high-voltage actuator is being controlled. SUMMARY

[0009] The examples described herein enable a circuit that can detect a force on a haptic high-voltage actuator while the actuator is driven by a high-voltage signal.

[0010] According to one aspect, a device includes a high-voltage amplifier for receiving a periodic signal at a first input and a driver circuit coupled to the output of the high-voltage amplifier. A feedback circuit can be coupled from the output of the driver circuit to a second input of the high-voltage amplifier, and a sense resistor can have a first node coupled to the output of the driver circuit and a second node coupled to a piezoelectric actuator. A signal conditioning circuit can have a first input capacitively coupled to the output of the high-voltage amplifier and a second input capacitively coupled to the piezoelectric actuator. The signal conditioning circuit can generate a first output signal and a second output signal.A signal conditioning amplifier can receive the first and second output signals of the signal conditioning circuit, and the signal conditioning amplifier can generate a first and a second output signal based on a difference between the first and second output signals of the signal conditioning circuit. An analog-to-digital converter can generate a digital output signal based on the first and second output signals of the signal conditioning amplifier, and the digital output signal can represent a level applied to the piezoelectric actuator.

[0011] According to one aspect, a system includes a digital-to-analog converter to receive a periodic digital signal from a processor and generate a periodic analog signal. A high-voltage amplifier can receive the periodic analog signal at a first input, and a driver circuit can be coupled to the output of the high-voltage amplifier. A feedback circuit can be coupled from the output of the driver circuit to a second input of the high-voltage amplifier, and a sense resistor can be coupled to a first node coupled to the output of the driver circuit and a second node coupled to a piezoelectric actuator.A signal conditioning circuit with a first input capacitively coupled to the output of the high-voltage amplifier and a second input capacitively coupled to the piezoelectric actuator can generate a first output signal and a second output signal. A signal conditioning amplifier can receive the first and second output signals from the signal conditioning circuit and generate a first and second output signal based on the difference between the first and second output signals of the signal conditioning circuit. An analog-to-digital converter can generate a digital output signal based on the output signal of the signal conditioning amplifier, where the digital output signal represents a pressure level applied to the piezoelectric actuator.The analog-to-digital converter can output the digital signal to a processor.

[0012] According to one aspect, a method includes the following steps: generating a periodic signal at the output of a digital-to-analog converter, amplifying the periodic signal to generate a high-voltage drive signal, driving a piezoelectric actuator with the high-voltage drive signal, detecting a differential signal between the voltage at the piezoelectric actuator and the high-voltage drive signal, and processing the differential signal to determine a force level exerted on the piezoelectric actuator. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 illustrates one of several examples of a device for controlling a piezoelectric actuator and for detecting force. Fig. Figure 2 illustrates waveforms that are representative of a system for controlling a piezoelectric actuator and for detecting force. Fig. Figure 3 illustrates a method for controlling a piezoelectric actuator and for detecting the force exerted on the piezoelectric actuator. DETAILED DESCRIPTION

[0013] Fig. Figure 1 illustrates one of several examples of a device 100 for controlling a piezoelectric actuator 150 to generate haptic feedback and to detect the force exerted on the piezoelectric actuator 150.

[0014] The digital input signal 105 can be fed into a digital-to-analog converter (DAC) 110. The DAC 110 can convert the digital input signal 105 into an analog signal 115. The high-voltage amplifier 120 can amplify the analog signal 115 to generate a drive signal 125.

[0015] The control signal 125 can be input into the driver circuit 128. The driver circuit 128 can include a high-side transistor 130 and a low-side transistor 135 in an inverter configuration. The high-side transistor 130 is illustrated as an NMOS transistor, but this is not meant to be a limitation. The high-side transistor 130 can be a PMOS transistor, a bipolar transistor, or another transistor type. The low-side transistor 135 is illustrated as a PMOS transistor, but this is not meant to be a limitation. The low-side transistor 135 can be an NMOS transistor, a bipolar transistor, or another transistor type. The driver circuit 128 can include further circuitry, which is described in Fig. 1 are not explicitly shown.

[0016] In the Fig. In the first illustrated example, the driver circuit 128 is shown as a separate component from the high-voltage amplifier 120. In other examples, the driver circuit 128 can be integrated into the high-voltage amplifier 120.

[0017] The high-voltage output signal 140 can be the output of the driver circuit 128. The high-voltage output signal 140 can be an analog signal with a peak-to-peak voltage greater than 50 volts. The high-voltage output signal 140 can drive the measuring resistor 145. The measuring resistor 145 can be coupled to the piezoelectric actuator 150. The piezoelectric actuator 150 is represented using a capacitor symbol because the electrical response of a piezoelectric actuator is typically modeled as capacitance. The use of the capacitor symbol is not intended to represent the physical construction of the piezoelectric actuator 150. The piezoelectric actuator 150 can produce a mechanical response when driven by a high-voltage signal at node 148.

[0018] The feedback circuit 190 can be used in a feedback path from the high-voltage output signal 140 to the inverting input of the high-voltage amplifier 120. The feedback path can compensate for any non-idealities and non-linearities in the high-voltage amplifier 120, the high-side transistor 130, and the low-side transistor 135.

[0019] The coupling capacitors 161 and 162 can each couple the control signal 125 and node 148 to the signal conditioning circuit 160. The signal conditioning circuit 160 can include filters, amplifiers, or other circuitry to modify the signals at its input. The coupling capacitors 161 and 162 allow high-voltage signals at the control signal 125 and node 148 to be coupled to the low-voltage signal conditioning circuit 160 without damaging the circuitry within the signal conditioning circuit 160.

[0020] The amplifier 170 can amplify the outputs of the signal conditioning circuit 160 and convert the outputs of the signal conditioning circuit 160 into a single-ended output 175.

[0021] The single-ended output 175 can be fed into an analog-to-digital converter (ADC) 180. The ADC 180 can also be referred to as ADC FSENSE, since it is the ADC for the sampling path. The ADC 180 can output a digital signal 185. The digital signal 185 can be input into the processor 187 or another circuit capable of receiving the digital signal 185. The processor 187 can be a digital signal processor (DSP), a microcontroller, an embedded processor, or another type of processor.

[0022] The signal conditioning circuit 160, the amplifier 170, and the ADC 180 enable the device 100 to detect the force exerted on the actuator 150. The force exerted on the actuator 150 can be detected as the voltage difference between the desired output at the control signal 125 and the actual signal at the actuator 150, which is measured at node 148.

[0023] In operation, an actuator in haptic applications can be driven with a high-voltage signal at a very short duty cycle. As one of several examples, an actuator can be driven with a high-voltage signal for 1 ms. This short period can be referred to as the actuator's on-time. The actuator can then be idle or not driven for 199 ms. This idle time can be referred to as the actuator's off-time. This 200 ms period can be repeated while the actuator is driven. This repeated pattern of on-time and off-time can be referred to as a burst signal or pulsed signal. This example is not intended to be limiting. In other examples, an actuator can be driven with a high-voltage signal for a different duration and then be idle for another duration.During the actuator's on-time, the high-voltage amplifier 120 can output a high-voltage signal, and the feedback circuit 190 can balance the voltages at the drive signal 125 and the high-voltage output signal 140. During this time, the inputs to the signal conditioning circuit 160 can be equal. During the actuator's off-time, the output voltage of the high-voltage amplifier 120 can fall below a predetermined threshold, and the feedback loop via the feedback circuit 190 can no longer effectively balance the voltages at the drive signal 125 and the high-voltage output signal 140. A user can apply physical pressure to the actuator 150, which can be measured as a voltage at node 148.The voltage difference between coupling capacitor 162 and coupling capacitor 161 can be fed into signal conditioning circuit 160, amplified by amplifier 170, and converted by ADC 180. The output of ADC 180, a digital signal, can represent the difference between the voltage at the high-voltage output signal 140 and the voltage at the piezoelectric element 150. This difference can reflect pressure applied to the piezoelectric element 150 by a user. If this difference exceeds a predefined threshold, it can be interpreted as a key press or other physical input by the user.

[0024] The in Fig. The illustrated example represents a single information channel driving a single actuator, but this is not meant to be limiting. In one of several examples, a multi-channel DAC can drive multiple high-voltage amplifiers and transistors to drive multiple actuators. A multi-channel signal conditioning circuit and a multi-channel ADC can convert signals received from the multiple actuators.

[0025] Fig. Figure 2 illustrates waveforms representative of a system for controlling a piezoelectric actuator and detecting force. The waveforms shown in Figure 2 are shown in Figure 2. Fig. The two waveforms shown can be representative of stresses on components of the device 100, as shown in Fig. 1 described and illustrated.

[0026] Signal curve 210 can represent the signal via actuator 150. Signal curve 220 can represent the single-ended output 175, the output signal of amplifier 170. Signal curve 230 can represent the control signal 125, the output signal of high-voltage amplifier 120.

[0027] During operation, the DAC 110 can drive a burst signal to node 115. The precise frequency and amplitude of the pulsed signal can represent a physical response, but this is not limited to a key press, a slider movement, or a vibration alarm. In one of several examples, the pulsed signal can have a period of 200 ms, with a 1 ms on-time. This pulsed signal can generate a charge pulse 235 at the output of the high-voltage amplifier 120, as illustrated in curve 230. Curve 220 can reflect the voltage difference between coupling capacitor 161 and coupling capacitor 162 during the on-time of the burst signal and stabilize at a nominal voltage during the off-time of the burst signal.The charge pulse on curve 230 can drive the gate of the high-side transistor 130 and the gate of the low-side transistor 135, which can drive the actuator 150, as illustrated in curve 210. The capacitance of the actuator 150 leads to the exponential decay illustrated in curve 210.

[0028] At position 215, a user can exert pressure on actuator 150. This pressure can be reflected in curve 220 as a deviation from its periodic characteristic. While curve 220 typically settles at a nominal voltage, position 216 illustrates a change in voltage that reflects the pressure exerted on actuator 150. The disturbance in curve 220 at position 216 can be converted by ADC 180, and if the disturbance exceeds a programmable threshold, it can be interpreted as user pressure on the actuator.

[0029] At position 225, a user can release the pressure on the actuator. This release of pressure can be captured in curve 220 as a deviation from the periodic nature of curve 220. While curve 220 typically settles at a nominal voltage, position 226 illustrates a change in voltage that reflects the release of the pressure applied to actuator 150. The disturbance in curve 220 at position 226 can be converted by ADC 180, and if the disturbance exceeds a programmable threshold, it can be interpreted as a user releasing the pressure on the actuator.

[0030] The in Fig. The two illustrated signals can enable smooth haptic effects without interference, as there are no switches to activate or deactivate the low-voltage paths.

[0031] The in Fig. The two illustrated specific voltages and frequencies are not to be understood as limiting. Other examples may use signals with different voltages and frequencies.

[0032] Fig. Figure 3 illustrates a method 300 for controlling a piezoelectric actuator and for detecting force.

[0033] In step 310, a periodic signal can be generated at the output of a digital-to-analog converter. In step 320, the periodic signal can be amplified to generate a high-voltage control signal. In step 330, a piezoelectric actuator can be controlled with the high-voltage control signal.

[0034] In step 340, a differential signal between the voltage at the piezoelectric actuator and the high-voltage control signal can be acquired. In step 350, this differential signal can be processed to determine the force level applied to the piezoelectric actuator. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 457,233

[0001]

Claims

[1] Device comprising: a high-voltage amplifier for receiving a periodic signal at a first input; a driver circuit coupled to the output of the high-voltage amplifier; a feedback circuit that is coupled from the output of the driver circuit to a second input of the high-voltage amplifier; a measuring resistor with a first node coupled to the output of the driver circuit and a second node coupled to a piezoelectric actuator; a signal conditioning circuit with a first input capacitively coupled to the output of the high-voltage amplifier and a second input capacitively coupled to the piezoelectric actuator, wherein the signal conditioning circuit generates a first output signal and a second output signal; a signal conditioning amplifier for receiving the first output signal and the second output signal of the signal conditioning circuit, wherein the signal conditioning amplifier generates a first output signal and a second output signal based on a difference between the first output signal of the signal conditioning circuit and the second output signal of the signal conditioning circuit, and an analog-to-digital converter for generating a digital output based on the first output signal and the second output signal of the signal conditioning amplifier, wherein the digital output represents a pressure level applied to the piezoelectric actuator. [2] Device according to claim 1, wherein the driver circuit comprises an inverter circuit. [3] Device according to one of claims 1 to 2, wherein the driver circuit comprises an amplifier circuit. [4] Device according to any one of claims 1 to 3, wherein the signal conditioning circuit includes a low-pass filter. [5] Device according to any one of claims 1 to 4, wherein the feedback circuit serves to compensate for differences between the periodic signal and the output of the driver circuit. [6] Device according to any one of claims 1 to 5, wherein the periodic signal is a burst sine signal. [7] System comprising one of the devices according to claims 1 to 6 and a digital-to-analog converter for receiving a periodic digital signal from a processor and generating the periodic signal. [8] Method which features: Generating a periodic signal at the output of a digital-to-analog converter; Amplifying the periodic signal to generate a high-voltage drive signal; Controlling a piezoelectric actuator with the high-voltage control signal; Capturing a differential signal between the voltage at the piezoelectric actuator and the high-voltage control signal; Processing the differential signal to determine a force level applied to the piezoelectric actuator. [9] Method according to claim 7, wherein the periodic signal is a burst sine signal. [10] Method according to claim 7, wherein the amplification of a periodic signal comprises feeding the periodic signal into a high-voltage amplifier. [11] Method according to claim 8, comprising coupling the high voltage signal to the input of the high voltage amplifier via a feedback circuit. [12] Method according to claim 8, wherein the feedback circuit serves to compensate for differences between the periodic signal and the output signal of the driver circuit. [13] Method according to claim 8, wherein the detection of a differential signal comprises a signal conditioning circuit coupled to a signal conditioning amplifier. [14] Method according to claim 8, wherein the detection of a differential signal comprises an analog-to-digital converter coupled to a processor. [15] Method according to claim 14, wherein the processing of the differential signal comprises processing the output of the analog-to-digital converter in the processor.

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