Displacement detection circuit and piezoelectric circuit for piezoelectric actuator

Abstract

The application discloses a displacement detection circuit and piezoelectric circuit of a piezoelectric actuator. The piezoelectric actuator is used to generate haptic feedback according to a received haptic voltage signal under external force application. The displacement detection circuit comprises a charge storage element for detecting a first charge generated by the piezoelectric actuator due to deformation; a compensation circuit for performing multiple charging operations or discharging operations on the charge storage element to provide a second charge opposite to the first charge to the charge storage element; a counting circuit for counting the number of charging operations or discharging operations of the compensation circuit to obtain a counting value; and a logic output circuit for calculating the total amount of the second charge provided by the compensation circuit according to the counting value, and obtaining the real-time displacement amount of the piezoelectric actuator according to the total amount of the charge, so that the displacement amount of the piezoelectric element in the haptic feedback process can be detected without setting a sensor, and the circuit is simplified, the cost is reduced, the product performance is improved, and the power consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric actuator driving technology, and more specifically, to a displacement detection circuit and a piezoelectric circuit for a piezoelectric actuator. Background Technology

[0002] Piezoelectric elements are functional ceramic materials capable of converting mechanical energy and electrical energy into each other. Due to their piezoelectric properties, they are widely used in various electronic devices. Piezoelectric elements exhibit both direct and inverse piezoelectric effects. When force is applied to a piezoelectric element, it generates an electric charge, which can be measured as current or voltage. Therefore, piezoelectric elements can be used to replace mechanical switches; when a user presses a button containing a piezoelectric element, the element generates a voltage / current that is detected by the electronic device. The inverse piezoelectric effect has the opposite result: when a voltage is applied to a piezoelectric element, mechanical strain is generated in the piezoelectric material, which produces force and / or displacement of the piezoelectric element. An exemplary application is in haptic actuators, where electronic devices can provide tactile feedback to the user by generating vibrations through the application of a voltage waveform to the actuator.

[0003] Piezoelectric actuators are highly attractive for systems that need to simultaneously sense user pressure and provide haptic feedback, as they can function as both sensors and actuators. Therefore, piezoelectric actuators are increasingly seen as a viable alternative to resonant actuators and are widely used in electronic devices such as mobile phones, laptops, and tablets to provide haptic feedback.

[0004] When combining actuation and sensing functions in a simple system, we want to continuously detect the deformation of the piezoelectric actuator due to drive output and external force while providing tactile feedback. Existing technologies typically use sensors to detect the output displacement of the piezoelectric actuator, which not only increases the overall system complexity and circuit cost, but also, due to the sensor's response speed limitations, may lead to delayed or inaccurate feedback, affecting the overall performance. Therefore, for specific application scenarios, more innovative displacement detection methods need to be considered to overcome these limitations. Summary of the Invention

[0005] In view of the above problems, the purpose of this invention is to provide a displacement detection circuit and a piezoelectric circuit for a piezoelectric actuator to overcome the shortcomings of the prior art. It can detect the displacement of the piezoelectric element in the tactile feedback process without the need for a sensor, which is beneficial to simplify the circuit, reduce costs, improve product performance and reduce power consumption.

[0006] According to one aspect of the present invention, a displacement detection circuit for a piezoelectric actuator is provided, the piezoelectric actuator being used to generate tactile feedback based on a received tactile voltage signal under the application of an external force, wherein the displacement detection circuit comprises: a charge storage element for detecting a first charge generated by the piezoelectric actuator due to deformation; a compensation circuit for performing multiple charging or discharging operations on the charge storage element to provide it with a second charge opposite to the first charge; a counting circuit for counting the number of charging or discharging operations of the compensation circuit to obtain a count value; and a logic output circuit for calculating the total amount of the second charge provided by the compensation circuit based on the count value, and obtaining the real-time displacement of the piezoelectric actuator based on the total amount of charge.

[0007] Optionally, the charge storage element generates a detection voltage at its first terminal when the first charge is detected, the detection voltage being proportional to the deformation of the piezoelectric actuator. The compensation circuit includes an upper threshold voltage and a lower threshold voltage, and is configured to discharge the charge storage element when the detection voltage is greater than the upper threshold voltage, and to charge the charge storage element when the detection voltage is less than the lower threshold voltage.

[0008] Optionally, the logic output circuit is configured to calculate the total charge of the second charge according to the following formula: Qtotal=n×ΔV×C, where Qtotal represents the total charge provided by the compensation circuit, n represents the count value obtained by the counting circuit, ΔV represents the voltage difference between the upper or lower threshold voltage and the set reference voltage, and C represents the capacitance value of the charge storage element.

[0009] Optionally, the logic output circuit is further configured to obtain the charging and discharging time of the compensation circuit based on the time interval of the change of the count value obtained by the counting circuit, and calculate the total charge of the second charge according to the following formula: Qtotal=Icc*t, where Qtotal represents the total charge provided by the compensation circuit, Icc is the magnitude of the compensation current provided by the compensation circuit, and t is the total charging and discharging time.

[0010] Optionally, the compensation circuit includes: a comparator for comparing the detected voltage with the upper threshold voltage and the lower threshold voltage to output different logic digital signals; a decimator for downsampling the output signal of the comparator to convert the high-speed digital signal output by the comparator into a low-speed digital signal; a compensation control module for generating a charging control signal and a discharging control signal based on the digital signal output by the decimator; and a charging / discharging module connected to the first terminal of the charge storage element for performing a charging operation or a discharging operation on the charge storage element according to the charging control signal or the discharging control signal.

[0011] Optionally, the charging and discharging module includes: a first switching element and a first current source connected in series between the supply voltage and a first terminal of the charge storage element; and a second current source and a second switching element connected in series between the first terminal of the charge storage element and ground, wherein the first switching element and the second switching element are turned on or off according to the charging control signal and the discharging control signal, respectively, so that the charge storage element is charged or discharged.

[0012] Optionally, the counting circuit includes an increment / decrement counter, wherein the increment / decrement counter is used to increment the current count value by 1 when a valid pulse of the discharge control signal is detected, decrement the current count value by 1 when a valid pulse of the charging control signal is detected, and output the accumulated count value as the final count value and clear it to zero when the invalid time of the charging control signal and the discharge control signal reaches a predetermined time.

[0013] Optionally, the counting circuit includes: a first counter for counting valid pulses of the charging control signal to obtain a first count value; a second counter for counting valid pulses of the discharging control signal to obtain a second count value; and a subtractor for subtracting the second count value from the first count value to obtain a final count value.

[0014] Optionally, the counting circuit is further configured to count according to a counting period that coincides with the period of the tactile voltage signal.

[0015] Optionally, the logic output circuit is further configured to calculate a first polarization charge in the piezoelectric actuator based on the tactile voltage signal, and to subtract the first polarization charge from the total polarization charge to obtain a second polarization charge generated by the piezoelectric actuator due to the application of force.

[0016] According to another aspect of the present invention, a piezoelectric circuit is provided, comprising: a piezoelectric actuator; a driver circuit, the output of which is connected to a first terminal of the piezoelectric actuator for outputting a tactile voltage signal to the piezoelectric actuator in response to an applied force, the piezoelectric actuator being configured to generate tactile feedback in response to the tactile voltage signal; and a displacement detection circuit according to any one of claims 1-10, connected to a second terminal of the piezoelectric actuator, the displacement detection circuit being configured to detect the amount of displacement of the piezoelectric actuator caused by the applied force and the tactile voltage signal.

[0017] Optionally, the driver circuit includes: a waveform generator for generating a drive signal with a set period in response to the application of force; and a buffer for providing the tactile voltage signal to the piezoelectric actuator according to the drive signal.

[0018] In summary, this invention provides a novel displacement detection circuit for detecting the displacement of a piezoelectric actuator. This circuit uses a charge storage element to collect the charge generated by the piezoelectric actuator due to deformation. Then, a compensation circuit charges and discharges the charge storage element to dissipate the accumulated charge. Finally, the total charge output by the compensation circuit is calculated based on the number of charge-discharge cycles, and the real-time displacement of the piezoelectric actuator is calculated based on this total charge. Compared to existing technologies, this displacement detection circuit eliminates the need for sensors to detect the real-time displacement of the piezoelectric element during tactile feedback, simplifying the circuit, reducing costs, improving product performance, and lowering power consumption. Attached Figure Description

[0019] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0020] Figure 1 A schematic circuit block diagram of an electronic device according to an embodiment of the present invention is shown.

[0021] Figure 2 A schematic circuit block diagram of a control circuit for controlling a piezoelectric actuator according to an embodiment of the present invention is shown.

[0022] Figure 3 A schematic circuit block diagram of a displacement detection circuit according to an embodiment of the present invention is shown.

[0023] Figure 4 A schematic circuit block diagram of a driver circuit according to an embodiment of the present invention is shown.

[0024] Figure 5 A schematic circuit block diagram of a compensation circuit according to an embodiment of the present invention is shown.

[0025] Figure 6 A schematic circuit block diagram of a counting circuit according to an embodiment of the present invention is shown.

[0026] Figure 7 A schematic circuit block diagram of another counting circuit according to an embodiment of the present invention is shown. Detailed Implementation

[0027] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in various forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0029] It should be understood that in the following description, when a component or circuit is said to be "coupled to" another component or "coupled between" two nodes, it can be directly coupled or connected to the other component or there may be intermediate components. The connection between components can be physical, logical, or a combination thereof. Conversely, when a component is said to be "directly coupled to" or "directly coupled to" another component, it means that there are no intermediate components between them.

[0030] The present invention will now be described in detail with reference to the accompanying drawings.

[0031] Figure 1 A schematic circuit block diagram of an electronic device according to an embodiment of the present invention is shown. Figure 1 As shown, the electronic device 10 may include a haptic feedback system 20, which can provide vibration or user feedback to the electronic device 10. For example, the haptic feedback system 20 can provide haptic feedback in response to a user's touch (or press) interaction.

[0032] It should be noted that, although Figure 1 The smartphone is shown as an example of electronic device 10, but it is merely exemplary. The haptic-enabled electronic device 10 can be, for example, a mobile phone, a laptop computer, a tablet computer, a vehicle user interface device, a wearable device (such as a watch), or any other haptic-enabled device.

[0033] For example, the haptic feedback system 20 may include a piezoelectric actuator 100 and control circuitry 200 configured to control the piezoelectric actuator 100. In one exemplary embodiment, the piezoelectric actuator 100 may include a sheet of piezoelectric material and two electrodes defined on opposite surfaces of the piezoelectric material sheet. For example, a top electrode may be formed on the top surface of the sheet and a bottom electrode may be formed on the bottom surface of the sheet. For example, the piezoelectric material in the piezoelectric actuator 100 may be composed of any suitable material, such as: naturally occurring crystals, such as quartz; synthetic crystals, such as lanthanum gallium silicate and lithium niobate; or synthetic ceramics, such as barium titanate, lead titanate, and lead zirconate titanate (PZT).

[0034] In a further embodiment, the electronic device 10 may have a housing that may include other components of the haptic-enabled electronic device 10, and the piezoelectric actuator 100 may be mounted on the housing or embedded within a portion of the housing. In one embodiment, the electronic device 10 may have a display device, and the piezoelectric actuator 100 may be attached to the display device or embedded within the display device. In some cases, the electronic device 10 may have a rigid component, and the piezoelectric actuator 100 may be embedded in the rigid component. In some cases, the electronic device 10 includes a touchpad or touchscreen suspended from a mounting surface via a suspension, and the piezoelectric actuator 100 may be attached to the touchpad or touchscreen.

[0035] In this embodiment, the control circuit 200 may be configured to generate a tactile voltage signal to drive the piezoelectric actuator 100. In some cases, the control circuit 200 may include an amplifier, or more generally, a piezoelectric driver circuit configured to generate a tactile voltage signal. In embodiments, the control circuit 200 may include one or more processors or processor cores, a programmable logic array (PLA) or programmable logic circuit (PLC), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), a microcontroller (MCU), or any other control circuitry. If the control circuit 200 includes a processor, the processor may be a general-purpose processor, such as a general-purpose processor in a mobile phone or other end-user device, or it may be a processor specifically designed to generate tactile effects.

[0036] Figure 2 A schematic circuit block diagram of a control circuit for controlling a piezoelectric actuator according to an embodiment of the present invention is shown. Figure 2As shown, the control circuit 200 of this embodiment may include a piezoelectric actuator circuit 201 and a microcontroller unit (MCU). The piezoelectric actuator circuit 201 further includes an actuator circuit 210 and a displacement detection circuit 220. The displacement detection circuit 220 is configured to sense a signal to the MCU in response to pressure exceeding a predetermined threshold on the piezoelectric actuator 100. The MCU provides a wake-up signal to the actuator circuit 210 based on the sensed signal. The actuator circuit 210 generates a tactile voltage signal Vdrv in response to the wake-up signal and transmits it to the piezoelectric actuator 100 for generating tactile feedback in response to effective pressure activation. Furthermore, the displacement detection circuit 220 is also configured to continuously detect the real-time displacement of the piezoelectric actuator 100 while the actuator circuit 210 provides the tactile voltage signal Vdrv and generates tactile feedback on the piezoelectric actuator 100, and provide this displacement to the MCU for subsequent processing.

[0037] Figure 3 A schematic circuit block diagram of a piezoelectric actuator circuit according to an embodiment of the present invention is shown. The output of the actuator circuit 210 is connected to a first terminal (e.g., the top plate) of the piezoelectric actuator 100 to output a tactile voltage signal Vdrv to the piezoelectric actuator 100 in response to an applied force. The piezoelectric actuator 100 is used to generate tactile feedback in response to the tactile voltage signal Vdrv. A displacement detection circuit 220 is connected to a second terminal (e.g., the bottom plate) of the piezoelectric actuator 100, and the displacement detection circuit 220 is used to detect the real-time displacement of the piezoelectric actuator 100 due to the applied force and the tactile voltage signal Vdrv during the tactile feedback.

[0038] in, Figure 3 A schematic diagram of an exemplary displacement detection circuit is shown. For example... Figure 3 As shown, in one exemplary embodiment, the displacement detection circuit 220 may include a charge storage element 221, a compensation circuit 222, a timing circuit 223, and a logic output circuit 224.

[0039] The first end of the charge storage element 221 is connected to the second end of the piezoelectric actuator 100, and the second end of the charge storage element 221 is grounded. For example, the charge storage element 221 can be implemented using a capacitor C1. When a force and / or driving voltage is applied to the piezoelectric actuator 100, the piezoelectric actuator 100 undergoes mechanical deformation. This mechanical deformation generates charge due to the positive piezoelectric effect. The charge generated by the piezoelectric actuator 100 at this time is collected by the charge storage element 221. The charge storage element 221 generates a detection voltage Vsen at its first end based on the detected charge. The magnitude of the detection voltage Vsen is proportional to the displacement of the piezoelectric actuator 100.

[0040] The compensation circuit 222 is used to provide a compensation current to the charge storage element 221 when the detection voltage Vsen reaches a set threshold voltage, so as to consume the charge accumulated in the charge storage element 221. In an exemplary embodiment, the compensation circuit 222 is provided with an upper threshold and a lower threshold. When the detection voltage Vsen reaches the upper threshold, the compensation circuit 222 performs a discharge operation on the charge storage element 221; and when the detection voltage Vsen reaches the lower threshold, the compensation circuit 222 performs a charging operation on the charge storage element 221. After multiple charge and discharge operations, the voltage Vsen on the charge storage element 221 stabilizes within the window range defined by the upper threshold and the lower threshold. Through the above operations, the present invention can compensate for the amount of charge generated by the deformation of the piezoelectric actuator 100 by the amount of charge provided by the compensation circuit 222, and the real-time displacement of the piezoelectric actuator 100 can be obtained by calculating the amount of charge provided by the compensation circuit 222.

[0041] The counting circuit 223 is used to count the number of times the compensation circuit 222 is charged or discharged to obtain a count value. For example, the counting circuit 223 can be implemented by incrementing or decrementing a counter. Whenever the compensation circuit 222 performs a discharge operation, the count value is incremented by 1, and whenever the compensation circuit 222 performs a charging operation, the count value is decremented by 1. This counting process is repeated until the displacement detection action is completed, and then the final count value is output.

[0042] The logic output circuit 224 is used to calculate the real-time displacement of the piezoelectric actuator 100 based on the count value obtained from the counting circuit 223.

[0043] In one exemplary embodiment, the logic output circuit 224 is used to calculate the amount of charge provided by the compensation circuit 222 based on the count value obtained by the counting circuit 223 using the following formula: Qtotal = n × ΔV × C (where Qtotal represents the amount of charge provided by the compensation circuit 222, n represents the count value obtained by the counting circuit 223, ΔV represents the voltage difference between the upper or lower threshold voltage and the set reference voltage, and C represents the capacitance value of the charge storage element 221). In one example, the reference voltage is equal to half of the upper or lower threshold voltage. Of course, the present invention does not limit this, and those skilled in the art can set the upper and lower threshold voltages and the reference voltage according to the actual situation.

[0044] In another exemplary embodiment, the logic output circuit 224 also calculates the total charging and discharging time of the compensation circuit 222 by calculating the time interval of the change of the count value, and then calculates the total charge provided by the compensation circuit 222 according to the formula Qtotal=Icc*t (where Qtotal represents the amount of charge provided by the compensation circuit 222, Icc represents the magnitude of the compensation current provided by the compensation circuit 222, and t is the total charging and discharging time).

[0045] As mentioned above, the amount of charge provided by the compensation circuit 222 is equal to the polarization charge generated by the deformation of the piezoelectric actuator 100. Therefore, the real-time displacement of the piezoelectric actuator 100 can be obtained based on the linear relationship between the calculated amount of charge of the compensation circuit 222 and the displacement of the piezoelectric actuator 100 (this linear relationship can be calibrated by an external sensor).

[0046] Figure 4 A schematic circuit block diagram of a driver circuit according to an embodiment of the present invention is shown. Figure 4 As shown, the driver circuit 210 of this embodiment includes a waveform generator 211 and a buffer 212. The waveform generator 211 generates a drive signal Vpulse with a set period in response to external pressure on the piezoelectric actuator 100. The voltage and period of the drive signal Vpulse can be given by the user. The buffer 212 receives the drive signal Vpulse output by the waveform generator 211 and amplifies the drive signal Vpulse to a voltage range required to drive the piezoelectric actuator 100, so as to provide a tactile voltage signal Vdrv to the piezoelectric actuator 100 and drive the piezoelectric actuator 100 to vibrate.

[0047] Figure 5 A schematic circuit block diagram of a compensation circuit according to an embodiment of the present invention is shown. Figure 5As shown, the compensation circuit 222 in this embodiment includes a comparator 2201, an extractor 2202, a compensation control module 2203, a charge / discharge module 2204, and a bias module 2205.

[0048] The bias module 2205 is used to set the upper threshold voltage VREFH and the lower threshold voltage VREFL of the comparator 2201. The voltage input terminal of the comparator 2201 is connected to the detection voltage Vsen at the first terminal of the charge storage element 221. Based on the comparison result between the detection voltage Vsen and the upper threshold voltage VREFH and the lower threshold voltage VREFL, the comparator 2201 outputs different logic digital signals. In an exemplary embodiment, the comparator 2201 outputs a first logic signal (e.g., a high-level signal or logic "1") when the detection voltage Vsen is greater than the upper threshold voltage VREFH; the comparator 2201 outputs a second logic signal (e.g., a low-level signal or logic "0") when the detection voltage Vsen is less than the lower threshold voltage VREFL.

[0049] Decimator 2202 is used to receive the output of comparator 2201 and to perform downsampling and decimation processing on the output signal of comparator 2201 to convert the high-speed digital signal output by comparator 2201 into a low-speed digital signal.

[0050] The input of the compensation control module 2203 is connected to the output of the extractor 2202, and it is used to generate a charging control signal SEL_chg and a discharging control signal SEL_dis based on the digital signal output by the extractor 2202. For example, when the output of the extractor 2202 is logic "1", the compensation control module 2203 generates the discharging control signal SEL_dis; when the output of the extractor 2202 is logic "0", the compensation control module 2203 generates the charging control signal SEL_chg.

[0051] The charge / discharge module 2204 is connected to the output of the compensation control module 2203 and the first terminal of the charge storage element 221, and is used to perform charging or discharging operations on the charge storage element 221 according to the charging control signal SEL_chg or the discharging control signal SEL_dis. For example, the charge / discharge module 2204 further includes a first current source 302 for sending a first current pulse to charge the charge storage element 221; a first switching element 301 for receiving the charging control signal SEL_chg and connected to the power supply voltage VDD and the first current source 302; a second current source 303 for sending a second current pulse to discharge the charge storage element 221; and a second switching element 304 for receiving the discharging control signal SEL_dis and connected to the ground voltage and the second current source 303. Further, the common connection node of the first current source 302 and the second current source 303 is connected to the first terminal of the charge storage element 221.

[0052] In one exemplary embodiment, the first switching element 301 and the second switching element 304 are NMOS transistors, and the charging control signal SEL_chg and the discharging control signal SEL_dis are non-overlapping signals. The present invention does not limit this. Those skilled in the art can use PMOS transistors to form the first switching element 301 and NMOS transistors to form the second switching element 304 according to actual applications.

[0053] Figure 6 A schematic circuit block diagram of a counting circuit according to an embodiment of the present invention is shown. In an exemplary embodiment, the counting circuit 223 is implemented by an increment / decrement counter 2231. The input of the increment / decrement counter 2231 is used to receive the charging control signal SEL_chg or the discharging control signal SEL_dis, and to count the valid pulses of the charging control signal SEL_chg and the discharging control signal SEL_dis to obtain a count value. For example, the increment / decrement counter 2231 increments the current count value by 1 when a valid (e.g., high-level) discharging control signal SEL_dis is received, and decrements the current count value by 1 when a valid (e.g., high-level) charging control signal SEL_chg is received, until a predetermined time has elapsed. If no valid charging control signal SEL_chg or discharging control signal SEL_dis is received, the accumulated count value is output as the final count value Cntx, and the count value of the increment / decrement counter 2231 is cleared to zero.

[0054] For example, the increment / decrement counter 2231 is further configured to read the pulse changes of the charging control signal SEL_chg and the discharging control signal SEL_dis at a certain rate during the tactile feedback provided by the piezoelectric driver circuit 201. The reading rate can be consistent with the period of the tactile voltage signal Vdrv output by the driver circuit 210. For example, the increment / decrement counter 2231 is used to count when the tactile voltage signal Vdrv is at a high level, and increment the current count value by 1 when the discharging control signal SEL_dis is at a high level, and keep the count value unchanged when the discharging control signal SEL_dis is at a low level; it also counts when the tactile voltage signal Vdrv is at a low level, and decrements the count value by 1 when the charging control signal SEL_chg is at a high level, and keeps the count value unchanged when the charging control signal SEL_chg is at a low level.

[0055] Continue to refer to Figure 3 In this embodiment, the logic output circuit 224 is further configured to obtain the change in polarization charge caused by external pressure during tactile feedback based on the change in count obtained by the counting circuit 223 and the change in the tactile voltage signal Vdrv. For example, the logic output circuit 224 can calculate the driving polarization charge Qdrv on the piezoelectric actuator 100 during tactile feedback based on the tactile voltage signal Vdrv. For example, the driving polarization charge Qdrv = Vdrv * K, where Vdrv is the voltage value of the tactile voltage signal, and K is a correlation coefficient related to the parameters of the piezoelectric actuator 100. Then, by subtracting the driving polarization charge Qdrv generated by the tactile voltage signal from the obtained total polarization charge Qtotal according to the formula Q = Qtotal - Qdrv, the polarization charge Q of the piezoelectric actuator 100 caused by external pressure can be calculated. Since the polarization charge generated on the piezoelectric actuator 100 caused by external pressure is proportional to the degree of external pressure, the logic output circuit 224 is also configured to calculate the force of external pressure based on the calculated polarization charge Q through coefficient transformation.

[0056] For example, since piezoelectric devices themselves have a stable response and a fast charge output response time, but there are differences between components within the circuit, it is necessary to periodically initialize and calibrate the transfer gain from voltage to charge in the inverse piezoelectric effect to eliminate errors and improve the measurement accuracy of the circuit. For example, the displacement detection circuit 220 of the present invention may also include an initialization module. This initialization module can calculate the inner product of the count changes based on the portion of the change in the count value output by the counting circuit 223 that matches the waveform profile of the tactile voltage signal Vdrv, using the driving waveform as a seed waveform, thereby obtaining the transfer gain of the inverse piezoelectric effect during piezoelectricity, and performing initial correction on this gain.

[0057] Figure 7A schematic circuit block diagram of another counting circuit according to an embodiment of the present invention is shown. In another exemplary embodiment, the counting circuit 323 includes a counter TRM1, a counter TRM2, and a subtractor 3231. The counter TRM1 is used to count the valid pulses of the charging control signal SEL_chg to obtain a count value Cnt1; the counter TRM2 is used to count the valid pulses of the discharging control signal SEL_dis to obtain a count value Cnt2; and the subtractor 3231 is used to subtract the count value Cnt1 from the count value Cnt2 to obtain the final count value Cntx.

[0058] For example, counters TRM1 and TRM2 are also configured to read the pulse changes of the charging control signal SEL_chg and the discharging control signal SEL_dis at a certain rate during the tactile feedback provided by the piezoelectric driver circuit 201, respectively, with the reading rate matching the period of the tactile voltage signal Vdrv output by the driver circuit 210. For instance, counter TRM2 is used to count when the tactile voltage signal Vdrv is high, and to increment the current count value by 1 when the discharging control signal SEL_dis is high. When the discharging control signal SEL_dis is low, the count value remains unchanged. After the discharging control signal SEL_dis has been low for a predetermined time, the accumulated count value of counter TRM2 is output as Cnt2. Counter TRM1 counts when the tactile voltage signal Vdrv is low, increments the count by 1 when the charging control signal SEL_chg is high, keeps the count unchanged when the charging control signal SEL_chg is low, and outputs the accumulated count value Cnt1 after the charging control signal SEL_chg has been low for a predetermined time. Then, subtractor 3231 calculates the count value Cntx based on the count values ​​Cnt1 and Cnt, where Cntx = Cnt2 - Cnt1.

[0059] Furthermore, the piezoelectric actuator circuit provided by this invention is in a power-off mode when the system is in standby mode, thus exhibiting extremely low circuit power consumption. When the piezoelectric actuator senses the user's force and deforms at the actuator, this deformation can be detected by the displacement detection circuit, generating a sensing signal to the microcontroller unit. The microcontroller unit wakes up the actuator circuit based on the sensing signal. In response to this wake-up, the actuator circuit generates a tactile voltage signal at the piezoelectric actuator to produce tactile feedback in response to effective pressure activation. Therefore, the displacement detection circuit provided by this invention can combine the functions of tactile feedback and external force detection. It can not only detect whether an external pressure has occurred at the piezoelectric actuator to wake up the entire piezoelectric actuator circuit, but also detect the force of the external pressure while providing tactile feedback. This allows the microcontroller unit to adjust the waveform of the tactile feedback vibration based on the detected pressure intensity feedback, improving the system's stability and performance.

[0060] In summary, this invention provides a novel displacement detection circuit for detecting the displacement of a piezoelectric actuator. This circuit uses a charge storage element to collect the charge generated by the piezoelectric actuator due to deformation. Then, a compensation circuit charges and discharges the charge storage element to dissipate the accumulated charge. Finally, the total charge output by the compensation circuit is calculated based on the number of charge-discharge cycles, and the real-time displacement of the piezoelectric actuator is calculated based on this total charge. Compared to existing technologies, this displacement detection circuit eliminates the need for sensors to detect the real-time displacement of the piezoelectric element during tactile feedback, simplifying the circuit, reducing costs, improving product performance, and lowering power consumption.

[0061] It should be noted that in the description of this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0062] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A displacement detection circuit for a piezoelectric actuator, wherein the piezoelectric actuator is used to generate tactile feedback based on a received tactile voltage signal under the application of an external force, wherein, The displacement detection circuit includes: A charge storage element is used to detect the first charge generated by the piezoelectric actuator due to deformation; A compensation circuit is used to perform multiple charging or discharging operations on the charge storage element to provide it with a second charge opposite to the first charge. A counting circuit is used to count the number of charging or discharging operations of the compensation circuit to obtain a count value; and A logic output circuit is used to calculate the total charge of the second charge provided by the compensation circuit based on the count value, and to obtain the real-time displacement of the piezoelectric actuator based on the total charge.

2. The displacement detection circuit of claim 1, wherein, The charge storage element generates a detection voltage at its first terminal upon detecting the first charge, the detection voltage being proportional to the deformation of the piezoelectric actuator. The compensation circuit includes an upper threshold voltage and a lower threshold voltage. The compensation circuit is configured to discharge the charge storage element when the detected voltage exceeds the upper threshold voltage. When the detected voltage is less than the lower threshold voltage, the charge storage element is charged.

3. The displacement detection circuit according to claim 2, wherein, The logic output circuit is configured to calculate the total charge of the second charge according to the following formula: Qtotal=n×ΔV×C Wherein, Qtotal represents the total charge provided by the compensation circuit, n represents the count value obtained by the counting circuit, ΔV represents the voltage difference between the upper or lower threshold voltage and the set reference voltage, and C represents the capacitance value of the charge storage element.

4. The displacement detection circuit according to claim 2, wherein, The logic output circuit is further configured to obtain the charging and discharging time of the compensation circuit based on the time interval of the change in the count value obtained by the counting circuit, and to calculate the total charge of the second charge according to the following formula: Qtotal=Icc*t Where Qtotal represents the total charge provided by the compensation circuit, Icc represents the magnitude of the compensation current provided by the compensation circuit, and t represents the total charging and discharging time.

5. The displacement detection circuit according to claim 2, wherein, The compensation circuit includes: A comparator is used to compare the detected voltage with the upper threshold voltage and the lower threshold voltage to output different logic digital signals; A decimator is used to downsample and decimate the output signal of the comparator to convert the high-speed digital signal output by the comparator into a low-speed digital signal. The compensation control module is used to generate charging control signals and discharging control signals based on the digital signals output by the extractor; and A charge / discharge module is connected to the first end of the charge storage element and is used to perform charging or discharging operations on the charge storage element according to the charging control signal or the discharging control signal.

6. The displacement detection circuit according to claim 5, wherein, The charging / discharging module includes: A first switching element and a first current source connected in series between the supply voltage and the first terminal of the charge storage element; and A second current source and a second switching element are connected in series between the first terminal of the charge storage element and ground. The first switching element and the second switching element are turned on or off according to the charging control signal and the discharging control signal, respectively, so that the charge storage element is charged or discharged.

7. The displacement detection circuit according to claim 5, wherein, The counting circuit includes an up / down counter. The increment / decrement counter is used to increment the current count value by 1 when a valid pulse of the discharge control signal is detected, decrement the current count value by 1 when a valid pulse of the charging control signal is detected, and output the accumulated count value as the final count value and clear it to zero when the invalid time of the charging control signal and the discharge control signal reaches a predetermined time.

8. The displacement detection circuit according to claim 5, wherein, The counting circuit includes: A first counter is used to count the valid pulses of the charging control signal to obtain a first count value; A second counter is used to count the effective pulses of the discharge control signal to obtain a second count value; and A subtractor is used to subtract the second count value from the first count value to obtain the final count value.

9. The displacement detection circuit according to claim 1, wherein, The counting circuit is also configured to count according to a counting period that is consistent with the period of the tactile voltage signal.

10. The displacement detection circuit of claim 1, wherein, The logic output circuit is further configured to calculate a first polarization charge in the piezoelectric actuator based on the tactile voltage signal, and to subtract the first polarization charge from the total charge to obtain a second polarization charge generated by the piezoelectric actuator due to the application of force.

11. A piezoelectric circuit, comprising: piezoelectric actuator; A driver circuit, the output of which is connected to a first terminal of the piezoelectric actuator, is used to output a tactile voltage signal to the piezoelectric actuator in response to the application of force, and the piezoelectric actuator is used to generate tactile feedback in response to the tactile voltage signal; as well as The displacement detection circuit according to any one of claims 1-10 is connected to the second end of the piezoelectric actuator, and the displacement detection circuit is used to detect the amount of displacement generated by the piezoelectric actuator due to the application of force and the tactile voltage signal.

12. The piezoelectric circuit according to claim 11, wherein, The driver circuit includes: A waveform generator for generating a drive signal with a set period in response to applied force; and A buffer is used to provide the tactile voltage signal to the piezoelectric actuator according to the drive signal.

Images