Displacement detection circuit for piezoelectric actuator, and piezoelectric actuator

Abstract

Disclosed in the present invention are a displacement detection circuit for a piezoelectric actuator, and a piezoelectric actuator. The piezoelectric actuator is used for generating haptic feedback on the basis of a received haptic voltage signal when an external force is applied. The displacement detection circuit comprises: a charge storage element, which is used for detecting first charges generated by a piezoelectric actuator due to deformation; a compensation circuit, which is used for performing multiple charging operations or discharging operations on the charge storage element, so as to provide the charge storage element with second charges which are opposite to the first charges; a counting circuit, which is used for counting the number of charging operations or discharging operations performed on the compensation circuit, so as to obtain a count value; and a logic output circuit, which is used for calculating, on the basis of the count value, a total charge amount of the second charges provided by the compensation circuit, and obtaining a real-time displacement amount of the piezoelectric actuator on the basis of the total charge amount. A displacement amount of a piezoelectric element during a haptic feedback process can be detected without the provision of sensors, thereby being conducive to simplifying a circuit, reducing costs, improving the product performance and reducing the power consumption.

Description

Displacement detection circuit of piezoelectric actuator and piezoelectric circuit

[0001] This application claims priority to a Chinese invention application filed on November 27, 2023, with application number 2023115947164, entitled “Displacement detection circuit and piezoelectric circuit for piezoelectric actuator,” and incorporates the entire specification, claims, drawings, and abstract of the above-mentioned Chinese invention application into this application by reference. Technical Field

[0002] The present invention relates to the technical field of piezoelectric actuator driving, and more particularly to a displacement detection circuit and a piezoelectric circuit of a piezoelectric actuator. Background Art

[0003] A piezoelectric element is a functional ceramic material that can convert mechanical energy into electrical energy. Due to its piezoelectric properties, it is widely used in various electronic devices. Piezoelectric elements have both direct piezoelectric effect and inverse piezoelectric effect. When force is applied to a piezoelectric element, the piezoelectric element can generate 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 on a button that includes a piezoelectric element, the piezoelectric element generates a voltage / current that is detected by the electronic device. The inverse piezoelectric effect has the opposite result. When voltage is applied to a piezoelectric element, mechanical strain is generated in the piezoelectric material, which will generate force and / or displacement of the piezoelectric element. An exemplary application is in a tactile actuator. An electronic device can generate vibration by applying a voltage waveform to the tactile actuator to provide tactile feedback to the user.

[0004] Piezoelectric actuators are very attractive for systems that need to simultaneously sense user pressure and provide tactile feedback, as the system can use piezoelectric actuators to act as both sensors and actuators. As a result, 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 tactile feedback.

[0005] When combining actuation and sensing functions in a simple system, we want to continuously monitor the piezoelectric actuator's deformation due to drive output and external forces while providing tactile feedback. Existing technologies typically use sensors to detect the piezoelectric actuator's output displacement, which not only increases the overall system complexity and circuit cost, but also can lead to delayed or inaccurate feedback due to sensor response speed issues, affecting the effectiveness. Therefore, for specific application scenarios, it is necessary to consider more innovative displacement detection methods to overcome these limitations. Summary of the Invention

[0006] In view of the above problems, the purpose of the present invention is to provide a displacement detection circuit and a piezoelectric circuit of a piezoelectric actuator to overcome the shortcomings of the prior art. The displacement of the piezoelectric element during the tactile feedback process can be detected without setting up a sensor, which is conducive to simplifying the circuit, reducing costs, improving product performance and reducing power consumption.

[0007] According to one aspect of the present invention, a displacement detection circuit for a piezoelectric actuator is provided, wherein the piezoelectric actuator is used to generate tactile feedback according to a received tactile voltage signal under the application of an external force, wherein the displacement detection circuit includes: 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 it with a second charge opposite to the first charge; a counting circuit for counting the number of charging operations or discharging operations of the compensation circuit to obtain a count value; and a logic output circuit for calculating the total charge 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 charge.

[0008] Optionally, the charge storage element is used to generate a detection voltage at its first end for detecting the first charge, and the detection voltage is proportional to the deformation of the piezoelectric actuator, wherein an upper threshold voltage and a lower threshold voltage are provided in the compensation circuit, and the compensation circuit 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.

[0009] Optionally, the logic output circuit is configured to calculate the total amount of the second charge according to the following formula: , where Qtotal represents the total amount of charge provided by the compensation circuit, n represents the count value obtained by the counting circuit, ∆V 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.

[0010] Optionally, the logic output circuit is further configured to obtain a charge and discharge time of the compensation circuit according to a change time interval of the count value obtained by the counting circuit, and calculate a total charge of the second charge according to the following formula: , where Qtotal represents the total amount of charge provided by the compensation circuit, Icc is the magnitude of the compensation current provided by the compensation circuit, and t is the total charge and discharge time.

[0011] Optionally, the compensation circuit includes: a comparator for comparing the detection voltage with the upper threshold voltage and the lower threshold voltage to output different logical digital signals; an extractor for downsampling and extracting the output signal of the comparator to convert the high-rate digital signal output by the comparator into a low-rate digital signal; a compensation control module for generating a charging control signal and a discharging control signal according to the digital signal output by the extractor; and a charging and discharging module connected to the first end 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.

[0012] Optionally, the charge and discharge module includes: a first switching element and a first current source connected in series between the power supply voltage and the first end of the charge storage element; and a second current source and a second switching element connected in series between the first end of the charge storage element and the 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.

[0013] Optionally, the counting circuit includes an up-down counter, wherein the up-down counter is used to add 1 to the current count value when a valid pulse of the discharge control signal is detected, subtract 1 from the current count value when a valid pulse of the charge 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 charge control signal and the discharge control signal reaches a predetermined time.

[0014] Optionally, the counting circuit includes: a first counter for counting the effective pulses of the charging control signal to obtain a first count value; a second counter for counting the effective 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.

[0015] Optionally, the counting circuit is further configured to count according to a counting period consistent with a period of the tactile voltage signal.

[0016] Optionally, the logic output circuit is also configured to calculate a first polarization charge in the piezoelectric actuator based on the tactile voltage signal, and 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.

[0017] According to another aspect of the present invention, a piezoelectric circuit is provided, comprising: a piezoelectric actuator; a driver circuit, wherein the output of the driver circuit is connected to a first end of the piezoelectric actuator, for outputting a tactile voltage signal to the piezoelectric actuator in response to force application, and the piezoelectric actuator is used to generate tactile feedback in response to the tactile voltage signal; and a displacement detection circuit according to any one of claims 1 to 10, connected to a second end of the piezoelectric actuator, and the displacement detection circuit is used to detect the displacement of the piezoelectric actuator caused by force application and the tactile voltage signal.

[0018] Optionally, the driver circuit includes: a waveform generator for generating a driving signal with a set period in response to force application; and a buffer for providing the tactile voltage signal to the piezoelectric actuator according to the driving signal.

[0019] In summary, an embodiment of the present invention provides a new type of displacement detection circuit for detecting the displacement of a piezoelectric actuator. The displacement detection circuit uses a charge storage element to collect the charge generated by the piezoelectric actuator due to deformation, and then uses a compensation circuit to charge and discharge the charge storage element to consume the charge accumulated in the charge storage element. Finally, the total charge output by the compensation circuit is calculated based on the number of charge and discharge times of the compensation circuit, and the real-time displacement of the piezoelectric actuator is calculated based on the obtained total charge. Compared with the prior art, the displacement detection circuit of the present invention can detect the real-time displacement of the piezoelectric element during the tactile feedback process without setting a sensor, which is conducive to simplifying the circuit, reducing costs, improving product performance and reducing power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0021] FIG1 shows a schematic circuit block diagram of an electronic device according to an embodiment of the present invention.

[0022] FIG2 shows a schematic circuit block diagram of a control circuit for controlling a piezoelectric actuator according to an embodiment of the present invention.

[0023] FIG3 shows a schematic circuit block diagram of a displacement detection circuit according to an embodiment of the present invention.

[0024] FIG4 shows a schematic circuit block diagram of a driver circuit according to an embodiment of the present invention.

[0025] FIG5 shows a schematic circuit block diagram of a compensation circuit according to an embodiment of the present invention.

[0026] FIG6 shows a schematic circuit block diagram of a counting circuit according to an embodiment of the present invention.

[0027] FIG7 shows a schematic circuit block diagram of another counting circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention may be implemented in various forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0030] It should be understood that in the following description, when an element or circuit is said to be "coupled to" another element or an element / circuit is said to be "coupled between" two nodes, it can be directly coupled or connected to the other element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly coupled to" another element, it means that there are no intermediate elements between the two.

[0031] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[0032] Figure 1 shows a schematic circuit block diagram of an electronic device according to an embodiment of the present invention. As shown in Figure 1, electronic device 10 may include a tactile feedback system 20. Tactile feedback system 20 may provide vibration or user feedback to electronic device 10. For example, tactile feedback system 20 may provide tactile feedback in response to a user's touch (or pressure) interaction.

[0033] It should be noted that although a smart phone is shown as an example of the electronic device 10 in Figure 1, it is merely exemplary, and the tactile-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 tactile-enabled device.

[0034] For example, the haptic feedback system 20 may include a piezoelectric actuator 100 and a control circuit 200 configured to control the piezoelectric actuator 100. In an exemplary embodiment, the piezoelectric actuator 100 may include a sheet of piezoelectric material and two electrodes defined on opposite sides of the sheet of piezoelectric material. 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).

[0035] In further embodiments, the electronic device 10 may have a housing that may include other components of the tactile-enabled electronic device 10, and the piezoelectric actuator 100 may be mounted to 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.

[0036] In this embodiment, the control circuit 200 can be configured to generate a tactile voltage signal to drive the piezoelectric actuator 100. In some cases, the control circuit 200 can include an amplifier, or more generally, a piezoelectric driver circuit configured to generate the tactile voltage signal. In embodiments, the control circuit 200 can 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 circuit. If the control circuit 200 includes a processor, the processor can be a general-purpose processor, such as found on a mobile phone or other end-user device, or can be a processor dedicated to generating tactile effects.

[0037] Figure 2 shows a schematic block diagram of a control circuit for controlling a piezoelectric actuator according to an embodiment of the present invention. As shown in Figure 2, the control circuit 200 of this embodiment may include a piezoelectric driver circuit 201 and a microcontroller unit (MCU). The piezoelectric driver circuit 201 further includes a driver circuit 210 and a displacement detection circuit 220. The displacement detection circuit 220 is configured to sense a signal to the microcontroller unit (MCU) in response to a pressure on the piezoelectric actuator 100 exceeding a predetermined threshold. The microcontroller unit (MCU) then provides a wake-up signal to the driver circuit 210 based on the sensed signal. In response to the wake-up signal, the driver circuit 210 generates a tactile voltage signal Vdrv and transmits it to the piezoelectric actuator 100 for generating tactile feedback in response to valid pressure activation. Furthermore, the displacement detection circuit 220 is configured to continuously detect the real-time displacement of the piezoelectric actuator 100 while the driver circuit 210 provides the tactile voltage signal Vdrv to generate tactile feedback on the piezoelectric actuator 100, and to provide this displacement to the microcontroller unit (MCU) for subsequent processing.

[0038] Figure 3 shows a schematic block diagram of a piezoelectric driver circuit according to an embodiment of the present invention. The output of the driver circuit 210 is connected to the 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 configured to generate tactile feedback in response to the tactile voltage signal Vdrv. The displacement detection circuit 220 is connected to the second terminal (e.g., the bottom plate) of the piezoelectric actuator 100 to detect the real-time displacement of the piezoelectric actuator 100 caused by the applied force and the tactile voltage signal Vdrv during tactile feedback.

[0039] 3 specifically shows a schematic diagram of the structure of an exemplary displacement detection circuit. As shown in FIG3 , in an 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 .

[0040] 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 force and / or a driving voltage is applied to the piezoelectric actuator 100, the piezoelectric actuator 100 undergoes mechanical deformation, which in turn 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.

[0041] The compensation circuit 222 is configured to provide a compensation current to the charge storage element 221 when the detection voltage Vsen reaches a set threshold voltage, thereby consuming 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 discharges the charge storage element 221; and when the detection voltage Vsen reaches the lower threshold, the compensation circuit 222 charges the charge storage element 221. After multiple charge and discharge operations, the voltage Vsen on the charge storage element 221 stabilizes within the window defined by the upper and lower thresholds. Through the above operations, the present invention can compensate for the charge generated by the deformation of the piezoelectric actuator 100 with the charge provided by the compensation circuit 222. The real-time displacement of the piezoelectric actuator 100 can be obtained by calculating the charge provided by the compensation circuit 222.

[0042] The counting circuit 223 is configured 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 as an up-down counter. Each time the compensation circuit 222 performs a discharge operation, the count value is incremented by 1, and each time the compensation circuit 222 performs a charge operation, the count value is decremented by 1. This counting process is repeated until the displacement detection operation is completed, at which point the final count value is output.

[0043] The logic output circuit 224 is configured to calculate the real-time displacement of the piezoelectric actuator 100 according to the count value obtained by the counting circuit 223 .

[0044] In an exemplary embodiment, the logic output circuit 224 is configured 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 × ∆V × C (wherein Qtotal represents the amount of charge provided by the compensation circuit 222, n represents the count value obtained by the counting circuit 223, ∆V represents the voltage difference between the upper or lower threshold voltage and a set reference voltage, and C represents the capacitance of the charge storage element 221). In one example, the reference voltage is equal to half of the upper and lower threshold voltages. Of course, the present invention is not limited to this, and those skilled in the art may set the upper and lower threshold voltages and the reference voltage according to actual circumstances.

[0045] In another exemplary embodiment, the logic output circuit 224 further calculates the total charge and discharge 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 (wherein Qtotal represents the amount of charge provided by the compensation circuit 222, Icc is the magnitude of the compensation current provided by the compensation circuit 222, and t is the total charge and discharge time).

[0046] 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 calculated linear relationship between the charge of the compensation circuit 222 and the displacement of the piezoelectric actuator 100 (this linear relationship can be obtained by calibration of an external sensor).

[0047] FIG4 shows a schematic circuit block diagram of a driver circuit according to an embodiment of the present invention. As shown in FIG4 , the driver circuit 210 of this embodiment includes a waveform generator 211 and a buffer 212 , wherein the waveform generator 211 is used to generate a drive signal Vpulse having a set period in response to external pressure on the piezoelectric actuator 100 , and the voltage and period of the drive signal Vpulse can be set by the user. The buffer 212 receives the drive signal Vpulse output by the waveform generator 211 and amplifies the drive signal Vpulse to the voltage range required to drive the piezoelectric actuator 100 , thereby providing the piezoelectric actuator 100 with a tactile voltage signal Vdrv, thereby driving the piezoelectric actuator 100 to vibrate.

[0048] Figure 5 shows a schematic circuit block diagram of a compensation circuit according to an embodiment of the present invention. As shown in Figure 5 , the compensation circuit 222 of this embodiment includes a comparator 2201 , an extractor 2202 , a compensation control module 2203 , a charge and discharge module 2204 , and a bias module 2205 .

[0049] 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 results of the detection voltage Vsen with the upper threshold voltage VREFH and the lower threshold voltage VREFL, the comparator 2201 outputs different logical digital signals. In an exemplary embodiment, the comparator 2201 outputs a first logic signal (e.g., a high-level signal or a 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 a logic "0") when the detection voltage Vsen is less than the lower threshold voltage VREFL.

[0050] The decimator 2202 is used to receive the output of the comparator 2201 and perform downsampling and decimation processing on the output signal of the comparator 2201 to convert the high-rate digital signal output by the comparator 2201 into a low-rate digital signal.

[0051] The input of the compensation control module 2203 is connected to the output of the decimator 2202, and is configured to generate a charge control signal SEL_chg and a discharge control signal SEL_dis based on the digital signal output by the decimator 2202. For example, when the output of the decimator 2202 is a logic "1", the compensation control module 2203 generates the discharge control signal SEL_dis; when the output of the decimator 2202 is a logic "0", the compensation control module 2203 generates the charge control signal SEL_chg.

[0052] The charge-discharge module 2204 is connected to the output of the compensation control module 2203 and the first end of the charge storage element 221, and is configured to charge or discharge the charge storage element 221 according to the charge control signal SEL_chg or the discharge control signal SEL_dis. For example, the charge-discharge module 2204 further includes a first current source 302 configured to send a first current pulse to charge the charge storage element 221; a first switch element 301 configured to receive the charge control signal SEL_chg and be connected to a power supply voltage VDD and the first current source 302; a second current source 303 configured to send a second current pulse to discharge the charge storage element 221; and a second switch element 304 configured to receive the discharge control signal SEL_dis and be connected to a ground voltage and the second current source 303. Furthermore, a common connection node between the first current source 302 and the second current source 303 is connected to the first end of the charge storage element 221.

[0053] In an 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 is not limited to this. Those skilled in the art can use PMOS transistors to form the first switching element 301 and use NMOS transistors to form the second switching element 304 according to actual applications.

[0054] FIG6 shows a schematic block diagram of a counting circuit according to an embodiment of the present invention. In an exemplary embodiment, the counting circuit 223 is implemented by an up-down counter 2231. The up-down counter 2231 receives the charge control signal SEL_chg or the discharge control signal SEL_dis at its input and counts valid pulses of the charge control signal SEL_chg or the discharge control signal SEL_dis to obtain a count value. For example, upon receiving a valid (e.g., high) discharge control signal SEL_dis, the up-down counter 2231 increments the current count value by 1, and upon receiving a valid (e.g., high) charge control signal SEL_chg, the up-down counter 2231 decrements the current count value by 1. If no valid charge control signal SEL_chg or discharge control signal SEL_dis is received after a predetermined time, the accumulated count value is output as the final count value Cntx, and the count value of the up-down counter 2231 is reset to zero.

[0055] For example, the up-down counter 2231 is further configured to read the pulse changes of the charging control signal SEL_chg and the discharge control signal SEL_dis at a certain rate during the period when the piezoelectric driver circuit 201 provides tactile feedback. The reading rate can be consistent with the period of the tactile voltage signal Vdrv output by the driver circuit 210. For example, the up-down counter 2231 is used to count when the tactile voltage signal Vdrv is at a high level, and add 1 to the current count value when the discharge control signal SEL_dis is at a high level, and the count value remains unchanged when the discharge control signal SEL_dis is at a low level; count when the tactile voltage signal Vdrv is at a low level, and subtract 1 from the count value when the charging control signal SEL_chg is at a high level, and keep the count value unchanged when the charging control signal SEL_chg is at a low level.

[0056] Continuing with FIG3 , the logic output circuit 224 of this embodiment is further configured to determine a change in polarization charge caused by external pressure during tactile feedback based on changes in the count obtained by the counting circuit 223 and changes in the tactile voltage signal Vdrv. For example, the logic output circuit 224 can calculate the drive polarization charge Qdrv on the piezoelectric actuator 100 during tactile feedback based on the tactile voltage signal Vdrv. For example, the drive 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, according to the formula Q=Qtotal-Qdrv, the driving polarization charge Qdrv generated by the tactile voltage signal is subtracted from the total polarization charge Qtotal obtained to obtain the polarization charge Q caused by the external pressure on the piezoelectric actuator 100. Since the polarization charge generated on the piezoelectric actuator 100 due to the external force is proportional to the degree of the external force, the logic output circuit 224 is also configured to calculate the force of the external pressure based on the calculated polarization charge Q through coefficient transformation.

[0057] For example, because the piezoelectric device itself has a stable response and a fast charge output response time, but there are differences between the components within the circuit, it is necessary to periodically initialize and calibrate the transfer gain of the inverse piezoelectric effect from voltage to charge 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 count value output by the counting circuit 223 that is consistent with the waveform profile of the tactile voltage signal Vdrv, using the driving waveform as a seed waveform, to obtain the transfer gain of the inverse piezoelectric effect during the piezoelectric period and initialize and calibrate this gain.

[0058] Figure 7 shows a schematic block diagram of another counting circuit according to an embodiment of the present invention. In another exemplary embodiment, counting circuit 323 includes a counter TRM1, a counter TRM2, and a subtractor 3231. Counter TRM1 is used to count the active pulses of the charge control signal SEL_chg to obtain a count value Cnt1; counter TRM2 is used to count the active pulses of the discharge control signal SEL_dis to obtain a count value Cnt2; and subtractor 3231 is used to subtract count value Cnt2 from count value Cnt1 to obtain a final count value Cntx.

[0059] For example, counters TRM1 and TRM2 are also configured to read the pulse changes of the charge control signal SEL_chg and the discharge control signal SEL_dis, respectively, at a certain rate during the period when the piezoelectric driver circuit 201 provides tactile feedback. The reading rate is consistent with the period of the tactile voltage signal Vdrv output by the driver circuit 210. For example, counter TRM2 is configured to count when the tactile voltage signal Vdrv is at a high level, and to increment the current count value by 1 when the discharge control signal SEL_dis is at a high level. When the discharge control signal SEL_dis is at a low level, the count value remains unchanged. After the discharge control signal SEL_dis remains at a low level for more than a predetermined time, the accumulated count value of counter TRM2 is output as Cnt2. The counter TRM1 counts when the tactile voltage signal Vdrv is at a low level and increments the count value by 1 when the charge control signal SEL_chg is at a high level. The counter TRM1 maintains the count value when the charge control signal SEL_chg is at a low level. After the charge control signal SEL_chg remains at a low level for a predetermined period of time, the counter TRM1 outputs the accumulated count value as Cnt1. The subtractor 3231 then calculates the count value Cntx from the count values ​​Cnt1 and Cnt, where Cntx = Cnt2 - Cnt1.

[0060] Furthermore, the piezoelectric driver circuit provided by the present invention is in a power-off mode when the system is in standby mode, so it has extremely low circuit power consumption. And when the piezoelectric actuator senses the user's force and generates deformation at the piezoelectric actuator, the deformation can be obtained by the displacement detection circuit and a sensing signal is generated in the displacement detection circuit to the microcontroller unit. The microcontroller unit wakes up the driver circuit according to the sensing signal, and the driver circuit generates a tactile voltage signal at the piezoelectric actuator in response to the wake-up to generate tactile feedback in response to effective pressure activation. Therefore, the displacement detection circuit provided by the present invention can realize the function of combining the monitoring and detection of tactile feedback and external force. It can not only be used to monitor whether external pressure occurs at the piezoelectric actuator to wake up the entire piezoelectric driver circuit, but also can detect the strength of the external pressure while providing tactile feedback, so that the microcontroller unit can adjust the waveform of the tactile feedback vibration according to the pressure intensity feedback obtained by the detection, thereby improving the stability and performance of the system.

[0061] In summary, an embodiment of the present invention provides a new type of displacement detection circuit for detecting the displacement of a piezoelectric actuator. The displacement detection circuit uses a charge storage element to collect the charge generated by the piezoelectric actuator due to deformation, and then uses a compensation circuit to charge and discharge the charge storage element to consume the charge accumulated in the charge storage element. Finally, the total charge output by the compensation circuit is calculated based on the number of charge and discharge times of the compensation circuit, and the real-time displacement of the piezoelectric actuator is calculated based on the obtained total charge. Compared with the prior art, the displacement detection circuit of the present invention can detect the real-time displacement of the piezoelectric element during the tactile feedback process without setting a sensor, which is conducive to simplifying the circuit, reducing costs, improving product performance and reducing power consumption.

[0062] It should be noted that, in the description of the present invention, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0063] Finally, it should be noted that the above embodiments are merely examples for the purpose of illustrating the present invention and are not intended to limit the embodiments. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to provide an exhaustive list of all embodiments. However, obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

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

2. The displacement detection circuit according to claim 1, wherein: The charge storage element is used to generate a detection voltage at a first end thereof according to the first charge detected, and the detection voltage is proportional to the deformation amount of the piezoelectric actuator. The compensation circuit is provided with an upper threshold voltage and a lower threshold voltage, and the compensation circuit is configured to discharge the charge storage element when the detection voltage is greater than the upper threshold voltage, and When the detection voltage is less than the lower threshold voltage, a charging operation is performed on the charge storage element.

3. The displacement detection circuit according to claim 2, wherein: The logic output circuit is configured to calculate the total amount of charge of the second charge according to the following formula:

4. Among them, Qtotal represents the total amount of charge provided by the compensation circuit, n represents the count value obtained by the counting circuit, ∆V 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.

5. The displacement detection circuit according to claim 2, wherein: The logic output circuit is further configured to obtain the charge and discharge time of the compensation circuit according to the change time interval of the count value obtained by the counting circuit, and calculate the total charge amount of the second charge according to the following formula:

6. Among them, Qtotal represents the total amount of charge provided by the compensation circuit, Icc is the magnitude of the compensation current provided by the compensation circuit, and t is the total charge and discharge time.

7. The displacement detection circuit according to claim 2, wherein: The compensation circuit comprises: A comparator, used for comparing the detection voltage with the upper threshold voltage and the lower threshold voltage to output different logic digital signals; A decimator, used for down-sampling and decimating the output signal of the comparator to convert the high-rate digital signal output by the comparator into a low-rate digital signal; a compensation control module, configured to generate a charging control signal and a discharging control signal according to the digital signal output by the extractor; and The charging and discharging module is connected to the first end of the charge storage element and is used to perform a charging operation or a discharging operation on the charge storage element according to the charging control signal or the discharging control signal.

8. The displacement detection circuit according to claim 5, wherein: The charging and discharging module comprises: A first switch element and a first current source connected in series between a supply voltage and the first terminal of the charge storage element; and a second current source and a second switch element connected in series between the first terminal of the charge storage element and ground, The first switch element and the second switch 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.

9. The displacement detection circuit according to claim 5, wherein: The counting circuit includes an up-down counter, The up-down counter is used to add 1 to the current count value when a valid pulse of the discharge control signal is detected, subtract 1 from the current count value when a valid pulse of the charge 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 charge control signal and the discharge control signal reaches a predetermined time.

10. The displacement detection circuit according to claim 5, wherein: The counting circuit comprises: A first counter, used for counting effective pulses of the charging control signal to obtain a first count value; a second counter, configured to count 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 a final count value.

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

12. The displacement detection circuit according to claim 1, wherein: The logic output circuit is also 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.

13. A piezoelectric circuit comprising: Piezoelectric actuators; a driver circuit, the output of the driver circuit being connected to the first end of the piezoelectric actuator, for outputting a tactile voltage signal to the piezoelectric actuator in response to the application of force, the piezoelectric actuator being configured to generate tactile feedback in response to the tactile voltage signal; as well as The displacement detection circuit described in any one of claims 1 to 10 is connected to the second end of the piezoelectric actuator, and the displacement detection circuit is used to detect the displacement of the piezoelectric actuator caused by the force applied and the tactile voltage signal.

14. The piezoelectric circuit according to claim 11, wherein: The driver circuit comprises: a waveform generator for generating a drive signal having a set period in response to the application of force; and A buffer is used to provide the tactile voltage signal to the piezoelectric actuator according to the driving signal.

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