Piezoelectric and electrostatic composite driving MEMS loudspeaker, array element and electronic equipment

Abstract

The invention discloses a piezoelectricity and static electricity composite driving MEMS loudspeaker, an array element and electronic equipment, the array element comprises an oscillator for generating sound signals, a fixing unit of the oscillator and a static electricity driving unit, and the oscillator comprises a piezoelectric driving unit. According to the piezoelectric and electrostatic composite driving MEMS loudspeaker provided by the invention, piezoelectric and electrostatic composite driving is adopted, so that the loudspeaker can work in a high-energy large-displacement state, higher sound pressure output is generated, meanwhile, the driving voltage is lower, and integration with an IC (Integrated Circuit) is facilitated; a piezoelectric and electrostatic composite driving voltage distribution mode is adopted, and the design of a stop structure is added, so that the service life of the loudspeaker is longer, and the reliability is higher.

Description

TECHNICAL FIELD

[0001] The present application relates to a piezoelectric micro-electro-mechanical system loudspeaker, an array element and an assembly thereof, and more particularly, to a piezoelectric micro-electro-mechanical system loudspeaker driven by piezoelectricity and electrostaticity, an array element and an electronic device. BACKGROUND

[0002] Piezoelectric micro-electro-mechanical system (MEMS) ultrasonic transducers have advantages such as easy mass production and compatibility with CMOS (Complementary Metal-Oxide-Semiconductor) that traditional ultrasonic transducers cannot have. However, the current development of piezoelectric micro-electro-mechanical system ultrasonic transducers encounters the problem of difficulty in obtaining high sensitivity.

[0003] A piezoelectric micro-electro-mechanical system loudspeaker contains a movable diaphragm or beam that is moved by applying a voltage to a driving electrode. A conventional MEMS loudspeaker is driven by electrostatic force alone. Once the driving voltage reaches the pull-in voltage, the system becomes unstable, and the beam accelerates to move towards the driving electrode. The driving voltage is determined by the stiffness of the beam. The threshold voltage of a piezoelectric micro-electro-mechanical system loudspeaker driven by electrostatic force is usually tens of volts or even hundreds of volts. Such a high driving voltage is a major obstacle to the integration of IC circuits.

[0004] Therefore, the prior art has problems to be further improved and developed. SUMMARY

[0005] (I) Invention purpose: To solve the above problems in the prior art, the purpose of the present application is to provide a MEMS loudspeaker driven by piezoelectricity and electrostaticity to improve the performance of the loudspeaker.

[0006] (II) Technical solution: In order to solve the above technical problems, the present application provides a MEMS loudspeaker driven by piezoelectricity and electrostaticity, wherein the array element includes a vibrator generating a sound signal, a fixed unit of the vibrator, and an electrostatic driving unit, and the vibrator includes a piezoelectric driving unit.

[0007] The MEMS loudspeaker driven by piezoelectricity and electrostaticity, wherein the vibrator includes a clamped-clamped beam, a cantilever beam, and a folded cantilever.

[0008] The MEMS loudspeaker driven by piezoelectricity and electrostaticity, wherein in the starting stage, an alternating voltage is applied to the piezoelectric driving unit to make the vibrator vibrate from the horizontal position by the resonance effect, and the electrostatic force of the electrostatic driving unit makes the vibrator remain in a high-energy state at its maximum amplitude position; then the vibrator enters the running stage.

[0009] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein, in the starting stage, the piezoelectric driving unit and the electrostatic driving unit work in turn; or in the starting stage, only the piezoelectric driving unit works; or in the starting stage, the piezoelectric driving unit and the electrostatic driving unit work simultaneously; or in the running stage, only the electrostatic driving unit works, and the piezoelectric driving unit does not work; or in the running stage, the electrostatic driving unit and the piezoelectric driving unit work simultaneously.

[0010] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein, when the vibrator enters the running stage and the vibrator is released, the restoring force of the vibrator is the resultant force of the elastic force generated by the rigidity of the vibrator and the restoring force generated by the reverse driving of the piezoelectric driving unit, and the resultant force makes the vibrator move away from the highest amplitude position.

[0011] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein, the fixed unit comprises upper and lower substrates, and the vibrator is arranged between the upper and lower substrates; cavities are formed between the upper and lower substrates and the vibrator; an upper sound hole is arranged on the upper substrate, and a lower sound hole is arranged on the lower substrate.

[0012] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein, the upper sound hole and the lower sound hole of the array element are arranged on the right side of the upper substrate and the left side of the lower substrate, respectively, or arranged at the center of the upper and lower substrates.

[0013] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein, the electrostatic driving unit comprises two electrostatic fixed electrodes on the inner walls of the two substrates, a continuous medium layer covering the electrostatic fixed electrodes, and two electrostatic driving electrodes on the upper and lower surfaces of the vibrator.

[0014] The electrostatic driving electrode on the upper surface of the vibrator, the electrostatic fixed electrode on the inner wall of the upper substrate, and the continuous medium layer covering the electrostatic fixed electrode form a first electrostatic driving unit.

[0015] The electrostatic driving electrode on the lower surface of the vibrator, the electrostatic fixed electrode on the inner wall of the lower substrate, and the continuous medium layer covering the electrostatic fixed electrode form a second electrostatic driving unit.

[0016] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein, the high-energy state includes high-position locking and low-position locking; through the interaction of the first electrostatic driving unit and the second electrostatic driving unit, the up-and-down position of the vibrator is converted, and the high-energy state of the vibrator remains unchanged.

[0017] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein the electrostatic driving electrode protrudes out of the surface of the vibrator or is embedded in the surface of the vibrator.

[0018] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein a stop unit is arranged on the electrostatic driving unit.

[0019] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein a plurality of stop units are arranged in sequence at positions close to the maximum amplitude of the vibrator, and the height of the plurality of stop units decreases in sequence at positions close to the maximum amplitude of the vibrator.

[0020] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein the stop unit has two, including a first stop unit and a second stop unit; under the joint action of the piezoelectric driving unit and the electrostatic driving unit, the vibrator bends; the vibrator contacts the first stop unit in the process of approaching the maximum amplitude position; the piezoelectric force of the piezoelectric driving unit is greater than the electrostatic force of the electrostatic driving unit.

[0021] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein under the joint action of the piezoelectric driving unit and the electrostatic driving unit, the vibrator continues to bend downward, the vibrator contacts the second stop unit and stays at the maximum amplitude position, and the electrostatic force of the electrostatic driving unit is greater than the piezoelectric force of the piezoelectric driving unit.

[0022] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein the stop unit has three, and four rows of sound holes are arranged on the upper and lower substrates respectively, so as to divide the upper and lower substrates into three parts, including a first lower substrate, a second lower substrate and a third lower substrate; the first lower substrate is provided with a static fixed electrode, a dielectric layer and a first stop unit, the second lower substrate is provided with a static fixed electrode, a dielectric layer and a second stop unit, and the third lower substrate is provided with a static fixed electrode, a dielectric layer and a third stop unit.

[0023] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein the positions of the first stop unit and the third stop unit are symmetrically arranged at a distance from the maximum amplitude of the vibrator, and the heights of the first stop unit and the third stop unit are the same; the second stop unit is located at the maximum amplitude of the vibrator, and the height of the second stop unit is less than the heights of the first stop unit and the third stop unit.

[0024] The piezoelectric and electrostatic composite driving MEMS speaker array element, wherein the vibrator package further comprises a support layer of the piezoelectric driving unit, and the piezoelectric driving unit comprises a piezoelectric layer, an upper electrode and a lower electrode.

[0025] The array element of the piezoelectric and electrostatic composite driven MEMS speaker, wherein the electrostatic driving electrode is arranged in the support layer, and the support layer is arranged below or above the piezoelectric driving unit.

[0026] The array element of the piezoelectric and electrostatic composite driven MEMS speaker, wherein the upper electrode or the lower electrode in the piezoelectric driving unit is used as the electrostatic driving electrode.

[0027] The array element of the piezoelectric and electrostatic composite driven MEMS speaker, wherein when the piezoelectric driving unit is arranged below the support layer, the lower electrode of the piezoelectric driving unit is the same as the electrostatic driving electrode; when the piezoelectric driving unit is arranged above the support layer, the upper electrode of the piezoelectric driving unit is the same as the electrostatic driving electrode.

[0028] The array element of the piezoelectric and electrostatic composite driven MEMS speaker, wherein one side of the cantilever beam is fixed between the upper and lower substrates, the upper and lower substrates are arranged with the electrostatic driving unit relative to the surface of the cantilever beam, and the other side of the cantilever beam is a free end.

[0029] The array element of the piezoelectric and electrostatic composite driven MEMS speaker, wherein a plurality of stop units are arranged on the substrate, and the heights of the plurality of stop units decrease from the fixed end to the free end.

[0030] The array element of the piezoelectric and electrostatic composite driven MEMS speaker, wherein the folded cantilever is E-shaped, including a middle free vibration diaphragm and two fixed diaphragms on both sides.

[0031] The array element of the piezoelectric and electrostatic composite driven MEMS speaker, wherein in the starting stage, under the action of the piezoelectric force of the piezoelectric driving unit, the surface of the cantilever beam is bent due to the inverse piezoelectric effect; the middle free vibration diaphragm and the two fixed diaphragms on both sides of the cantilever beam are bent, and the bending of the free vibration diaphragm and the two fixed diaphragms on both sides are offset.

[0032] The array element of the piezoelectric and electrostatic composite driven MEMS speaker, wherein the shape of the array element is square, rectangular or circular.

[0033] A piezoelectric and electrostatic composite driven MEMS speaker, wherein the array element described above is included, and a plurality of array elements are integrated to form a MEMS speaker array.

[0034] An electronic device includes: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus, and the processor is connected to the above-mentioned piezoelectric and electrostatic composite driven MEMS speaker.

[0035] (III) Beneficial Effects: This invention provides a MEMS speaker with a piezoelectric and electrostatic hybrid drive. By employing this hybrid drive, the speaker can operate in a high-energy, large-displacement state, generating higher sound pressure output while simultaneously lowering the drive voltage, facilitating integration with integrated circuits. The voltage distribution scheme employed by this hybrid drive, combined with a stop structure, extends the speaker's lifespan and enhances its reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a structural schematic diagram of a piezoelectric and electrostatic composite driven MEMS loudspeaker including an array element array according to the present invention;

[0037] Figure 2 It is a vibration timing diagram of the array element of the present invention;

[0038] Figure 3 1 is a schematic structural diagram of a first preferred embodiment of an array element of a MEMS loudspeaker driven by piezoelectric and electrostatic composite drive according to the present invention;

[0039] Figure 4 It is a schematic structural diagram of an array element of a MEMS loudspeaker driven by piezoelectric and electrostatic combination according to the present invention, in which the electrostatic driving electrodes are buried in the surface of a clamped beam;

[0040] Figure 5 It is a schematic diagram of a stop unit in an array element of a MEMS loudspeaker driven by piezoelectric and electrostatic combination according to the present invention;

[0041] Figure 6 It is a schematic diagram of the mechanism of the array element of the MEMS loudspeaker driven by piezoelectric and electrostatic combination in the operation stage of the present invention, in which the clamped beam vibrates downward and contacts the first stop unit;

[0042] Figure 7 It is a schematic diagram of the mechanism of the array element of the MEMS loudspeaker driven by piezoelectric and electrostatic combination in the operation stage of the present invention, in which the clamped beam vibrates downward and contacts the second stop unit;

[0043] Figure 8 It is a schematic diagram of the mechanism of the array element of the MEMS loudspeaker driven by piezoelectric and electrostatic combination in the operation stage of the present invention, in which the clamped beam vibrates upward and contacts the first stop unit;

[0044] Figure 9is the mechanism diagram of the fixed beam vibrating upward and the second stop unit contacting in the running stage of the array element of the piezoelectric and electrostatic composite driving MEMS speaker of the present application;

[0045] Figure 10 is the structure diagram of the third preferred embodiment with four rows of sound holes in the array element of the piezoelectric and electrostatic composite driving MEMS speaker of the present application;

[0046] Figure 11 is the structure diagram of the piezoelectric driving unit being located below the support layer and the lower electrode of the piezoelectric driving unit being the same electrode as the electrostatic driving electrode in the array element of the piezoelectric and electrostatic composite driving MEMS speaker of the present application;

[0047] Figure 12 is the structure diagram of the piezoelectric driving unit being located above the support layer and the upper electrode of the piezoelectric driving unit being the same electrode as the electrostatic driving electrode in the array element of the piezoelectric and electrostatic composite driving MEMS speaker of the present application;

[0048] Figure 13 is the structure diagram of the piezoelectric driving unit being located above the support layer and the upper electrode of the piezoelectric driving unit being the same electrode as the electrostatic driving electrode in the array element of the piezoelectric and electrostatic composite driving MEMS speaker of the present application;

[0049] Figure 14 is the structure diagram of the piezoelectric driving unit being located above the support layer and the upper electrode of the piezoelectric driving unit being the same electrode as the electrostatic driving electrode in the array element of the piezoelectric and electrostatic composite driving MEMS speaker of the present application;

[0050] Figure 15 is the structure diagram of the piezoelectric driving unit being located above the support layer and the upper electrode of the piezoelectric driving unit being the same electrode as the electrostatic driving electrode in the array element of the piezoelectric and electrostatic composite driving MEMS speaker of the present application;

[0051] Figure 16 is the structure diagram of the piezoelectric driving unit being located above the support layer and the upper electrode of the piezoelectric driving unit being the same electrode as the electrostatic driving electrode in the array element of the piezoelectric and electrostatic composite driving MEMS speaker of the present application;

[0052] Figure 17 is the structure diagram of the piezoelectric driving unit being located above the support layer and the upper electrode of the piezoelectric driving unit being the same electrode as the electrostatic driving electrode in the array element of the piezoelectric and electrostatic composite driving MEMS speaker of the present application; Figure 19 is the bottom view of the vibration element, which is viewed from below along the AA' section;

[0053] Figure 18 is the bottom view of the vibration element, which is viewed from below along the AA' section; Figure 19 is the top view of the vibration element, which is viewed from above along the BB' section;

[0054] Figure 19 is the array element of the piezoelectric and electrostatic composite driving MEMS speaker of the present application, in which Figure 17 is the cross-sectional view of the folded cantilever beam structure along CC' direction;

[0055] Figure 20 is the array element of the piezoelectric and electrostatic composite driving MEMS speaker of the present application, in which the vibrator is arranged as a folded cantilever beam structure, and the Figure 17 is the cross-sectional view along DD';

[0056] Figure 21 is the structural schematic diagram of the electronic device with the piezoelectric and electrostatic composite driving MEMS speaker of the present application. DETAILED DESCRIPTION

[0057] The present application will be further described below in conjunction with the preferred embodiments, and more details are set forth in the following description in order to fully understand the present application, however, the present application can be implemented in many different ways other than the description, and the person skilled in the art can make similar generalization and deduction according to the actual application without departing from the connotation of the present application, therefore, the protection scope of the present application should not be limited by the content of the specific embodiments.

[0058] The accompanying drawings are schematic diagrams of the embodiments of the present application, it should be noted that the accompanying drawings are only examples, not drawn according to the condition of the same scale, and should not be used as a limitation to the actual claimed protection scope of the present application.

[0059] The present application provides a piezoelectric and electrostatic composite driving MEMS speaker, as shown in Figure 1 which includes a plurality of array elements, each of which can independently control the displacement of the inner diaphragm, the plurality of array elements are integrated to form a MEMS speaker array, and jointly realize the synthesis of sound signals. The shape of the array element can be square, rectangular, circular, etc., which is not limited in the present application. The array shape formed by the array element can be hexagonal, circular, cross-shaped, one-shaped, or rectangular, etc., which is also not limited in the present application.

[0060] The present application provides a piezoelectric and electrostatic composite driving MEMS speaker, as shown in Figure 1 which includes a plurality of array elements, each of which can independently control the displacement of the inner diaphragm, the plurality of array elements are integrated to form a MEMS speaker array, and jointly realize the synthesis of sound signals. The shape of the array element can be square, rectangular, circular, etc., which is not limited in the present application. The array shape formed by the array element can be hexagonal, circular, cross-shaped, one-shaped, or rectangular, etc., which is also not limited in the present application.

[0061] The present invention provides a MEMS speaker array element driven by a piezoelectric and electrostatic combination. The present invention describes in detail the first preferred embodiment of the array element having a rectangular shape and the vibrator being a fixed beam. The fixed beam can also be a cantilever beam, a folded cantilever, or other vibrator forms, which will not be described in detail here. A cross-sectional view of the rectangular array element is shown in FIG. Figure 3 As shown, the array element includes a clamped beam, a fixing unit for the clamped beam, and an electrostatic drive unit. The fixing unit comprises upper and lower substrates 501, with the clamped beam disposed between them. A cavity is formed between the upper and lower substrates 501 and the clamped beam. The clamped beam includes a piezoelectric drive unit and a support layer 201. The piezoelectric drive unit comprises a piezoelectric layer 101, an upper electrode 102, and a lower electrode 103. The clamped beam is also called a diaphragm.

[0062] Electrostatic drive units are provided on the upper and lower substrates 501 and the inner walls of the opposing clamped beams. These units include electrostatic fixed electrodes on the two substrates 501 and electrostatic drive electrodes on the upper and lower surfaces of the clamped beams. The electrostatic drive electrodes on the upper surface of the clamped beams and the electrostatic fixed electrodes on the inner wall of the upper substrate are referred to as first electrostatic drive units. The interaction of the first electrostatic drive unit, specifically the conversion of voltages on the electrostatic fixed electrodes, is used to change the vibration direction of the clamped beams. The electrostatic drive electrodes on the lower surface of the clamped beams and the electrostatic fixed electrodes on the inner wall of the lower substrate are referred to as second electrostatic drive units. The interaction of the second electrostatic drive unit, specifically the conversion of voltages on the electrostatic fixed electrodes, is used to change the vibration direction of the clamped beams. Upper and lower acoustic holes 506 are provided on the upper and lower substrates 501, respectively. The upper and lower acoustic holes of the array element are located at the center of each substrate. In the present invention, an AC voltage is applied to the piezoelectric drive unit to cause the clamped beams to resonate from a horizontal position. The driving force of the electrostatic drive unit maintains the clamped beams in a high-energy state at their maximum amplitude. The input voltage of the electrostatic driving electrode is an alternating current voltage of a specific frequency, and the frequency of the alternating current voltage of the electrostatic driving unit is synchronized with the vibration frequency of the clamped beam.

[0063] The electrostatic driving electrode of the present invention protrudes from the surface of the fixed beam, such as Figure 3 As shown; the electrostatic driving electrode is buried in the surface of the fixed beam, as shown Figure 4 The present invention does not limit the arrangement of the electrostatic driving electrodes on the clamped beam.

[0064] The vibration timing diagram of the array element of the present invention is as follows: Figure 2As shown, the vibration of the array element includes a starting phase and a running phase. In the starting phase, an alternating voltage is applied to the piezoelectric layer of the fixed beam to make the fixed beam vibrate by resonance effect. The fixed beam reaches the maximum amplitude position or the vicinity of the maximum amplitude position by resonance. The high-energy state of the maximum amplitude position is also the maximum amplitude position of the fixed beam. In the timing diagram of the array element, the piezoelectric driving electrode and the electrostatic driving electrode are simultaneously inputted with alternating current through the common electrode.

[0065] The fixed beam reaches the maximum amplitude position, and the maximum amplitude position is near. Then, the voltage of the electrostatic fixed electrode is increased, the fixed beam and the electrostatic driving electrode are attracted, and the fixed beam is locked at the maximum amplitude position. The high-energy state is locked by the electrostatic driving unit, and the energy is stored. The high-energy state includes high and low lockings, and the locking position of the fixed beam includes high and low lockings. The fixed beam, that is, the up and down positions of the diaphragm are converted by the interaction release of the first electrostatic driving unit and the second electrostatic driving unit, but the high-energy state remains unchanged. In the starting state, the piezoelectric force of the piezoelectric driving unit mainly realizes large displacement vibration, and the electrostatic force of the electrostatic driving unit locks the diaphragm position at the end; in the running state, the electrostatic force of the electrostatic driving unit mainly controls the diaphragm to convert the up and down positions, and the piezoelectric force of the piezoelectric driving unit assists the diaphragm to escape from the locking position.

[0066] The fixed beam is locked at the maximum amplitude position, also known as closed, or the closure of the diaphragm, or the closure of the loudspeaker.

[0067] The array element of the piezoelectric and electrostatic composite driving MEMS loudspeaker of the application can make the fixed beam move downward by the piezoelectric driving when the distance between the electrostatic driving electrode and the electrostatic fixed electrode is far. When the distance between the electrostatic driving electrode and the electrostatic fixed electrode is close, the electrostatic force between the electrostatic driving electrode and the electrostatic fixed electrode acts on the fixed beam, and the required electrostatic driving voltage is greatly reduced. Therefore, compared with the traditional pure electrostatic driving MEMS loudspeaker, the composite driving MEMS loudspeaker of the application does not require high electrostatic driving voltage, and the required electrostatic driving voltage of the composite driving MEMS loudspeaker of the application is less than 10V.

[0068] The driving voltage of the electrostatic driving unit is reduced, the kinetic energy of the fixed beam caused by the electrostatic force is reduced during the downward movement of the fixed beam, and the kinetic energy of the fixed beam caused by the piezoelectric force is also not large. Therefore, when the fixed beam contacts the fixed unit at the highest amplitude position or when the fixed beam is released, the impact force is reduced, and the wear of the fixed beam and the electrostatic driving unit is also reduced, which can increase the service life of the loudspeaker.

[0069] Finally, when the fixed beam is released, the restoring force of the fixed beam is the combined force of the elastic force generated by the rigidity of the fixed beam and the restoring force generated by the reverse driving of the piezoelectric driving unit, and the combined force makes the fixed beam move away from the highest amplitude position. Thus, the fixed beam of the composite driving MEMS loudspeaker of the present application has stronger restoring force, which avoids the problem that the fixed beam cannot be disconnected from the fixed unit due to the surface adhesion force of the fixed beam and the fixed unit, and further improves the service life of the MEMS loudspeaker.

[0070] In the closing process, the piezoelectric force plays a role in most of the distance, and only when the distance is close to the electrostatic driving electrode, the electrostatic force provided by the electrostatic driving unit plays a role.

[0071] The piezoelectric and electrostatic composite driving MEMS loudspeaker of the present application can select different working modes to achieve better results, for example: in order to reduce the driving voltage and power consumption, the piezoelectric driving unit and the electrostatic driving unit can be selected to work in sequence in the starting stage; or only the piezoelectric driving unit works in the starting stage; or the piezoelectric driving unit and the electrostatic driving unit work simultaneously in the starting stage; or only the electrostatic driving unit works in the running stage, and the piezoelectric driving unit does not work; or the electrostatic driving unit and the piezoelectric driving unit work simultaneously in the running stage. In order to improve the response time and working frequency in the running stage, the electrostatic driving unit and the piezoelectric driving unit can be selected to work simultaneously in the running stage.

[0072] The upper substrate of the fixed beam is bonded to the fixed beam through two bonding layers 401 located at both ends of the upper substrate, and the lower substrate is bonded to the fixed beam through bonding layers 401 located at both ends of the lower substrate; cavities are formed between the upper and lower substrates 501 and the fixed beam. The cavity formation method is not limited, and the preferred method of the present application is to form a cavity by using a sacrificial layer 402 release process. Acoustic holes 506 are arranged on the upper and lower substrates 501 respectively, including upper acoustic holes on the upper substrate and lower acoustic holes on the lower substrate, and the upper acoustic holes and the lower acoustic holes of the array element are arranged at the center of the upper and lower substrates.

[0073] The preferred method of the present application is to lay electrostatic fixed electrodes 502 on one side of the upper and lower substrates 501 close to the fixed beam, and cover the electrostatic fixed electrodes 502 with a continuous dielectric layer 503. The dielectric layer 503 can be made of dielectric materials such as silicon oxide, which is used to isolate and protect the electrostatic fixed electrodes 502, and is not limited in the present application.

[0074] The fixed beam includes a piezoelectric driving unit 100 and a support layer 201, and moves inside the cavity to compress air. The cavity includes an upper cavity above the fixed beam and a lower cavity below the fixed beam. When the fixed beam moves downward, air in the upper cavity is expanded to emit negative air pressure pulses or negative air flow rate pulses from the upper sound hole; when the fixed beam moves upward, air in the upper cavity is compressed to emit positive air pressure pulses or positive air flow rate pulses from the upper sound hole to generate sound. The upper sound hole on the upper substrate and the lower sound hole on the lower substrate generate opposite air pressure pulses or air flow rate pulses at the same time.

[0075] The second preferred embodiment of the array element of the piezoelectric and electrostatic composite driven MEMS loudspeaker of the present application can further include a stopping unit on the upper surface of the medium layer 503, which is in contact with the fixed beam to release the kinetic energy of the fixed beam and reduce the impact force of the fixed beam on the medium layer 503. At the same time, the stopping unit reduces the direct contact area of the medium layer 503 with the electrostatic driving electrode 202, avoiding the problem of electrostatic driving force reduction caused by charging of the medium layer 503. The present application adopts a composite driving mode of electrostatic driving unit and piezoelectric driving unit, and the fixed beam is in contact with the stopping unit in the composite driving mode, which can drive the vibration of the fixed beam with lower voltage, reduce the impact force of the fixed beam on the stopping unit in the closed state, reduce the wear of the stopping unit, and increase the service life of the array element and the loudspeaker. The continuous medium layer on the surface of the electrostatic fixed electrode fixes the fixed beam at the maximum amplitude position. The stopping unit of the present application functions to reduce the impact force of the fixed beam, reduce the loss, and increase the service life: during the closing process, the fixed beam first contacts the first stopping structure and then contacts the second stopping structure; during the contact with the two stopping structures, the kinetic energy of the beam is released, reducing the impact force of the fixed beam on the fixed part; at the same time, the stopping structure reduces the direct contact area of the medium layer 503 and the electrostatic driving electrode, avoiding the problem of electrostatic driving force reduction caused by charging of the medium layer.

[0076] When the stopping unit of the present application is in contact with the fixed beam, the electrostatic fixed electrode 502 of the medium layer 503 interacts with the electrostatic driving electrode 202 of the fixed beam to make the fixed beam stay at the position of maximum amplitude under the attraction of the stopping unit, and the fixed beam is closed.

[0077] The electrostatic driving unit is provided with a stopping unit for fixing the fixed beam at the position of maximum amplitude.

[0078] Preferably, the stopping unit can have multiple, including a first stopping unit, a second stopping unit, a third stopping unit, etc., the multiple stopping units are arranged in order near the maximum amplitude of the fixed beam, and the height of the multiple stopping units is lowered in order near the maximum amplitude of the fixed beam. The first stopping unit is far away from the maximum amplitude of the fixed beam, and the second stopping unit is close to the maximum amplitude of the fixed beam. The height of the first stopping unit is greater than the height of the second stopping unit, as shown in Figure 5 .

[0079] The working process of the array element of the present application includes closing operation at the maximum amplitude position of the fixed beam and opening operation away from the maximum amplitude position of the fixed beam, as shown in Figure 6 , Figure 7 , Figure 8 and Figure 9 .

[0080] The process of the fixed beam in the downward closing operation and the opening operation is the same as the process of the fixed beam in the upward closing operation and the opening operation. The present application takes the downward closing operation of the fixed beam as an example for detailed introduction, as shown in Figure 6 and Figure 7 .

[0081] Step one, in the starting state, the piezoelectric driving unit 100 on the array element is changed with the driving voltage to make the fixed beam resonate, and the fixed beam continuously vibrates inside the cavity, thereby compressing the air in the upper cavity or the lower cavity.

[0082] Step two, under the joint action of the piezoelectric driving unit 100 and the second electrostatic driving unit, the fixed beam is bent; in the process of approaching the maximum amplitude position, the fixed beam contacts the first stopping unit 504, and in this process, the piezoelectric force of the piezoelectric driving unit plays a major role, and the piezoelectric force is greater than the electrostatic force, as shown in Figure 6 .

[0083] Step three, under the joint action of the piezoelectric driving unit 100 and the second electrostatic driving unit, the fixed beam continues to bend downward, and the fixed beam contacts the second stopping unit 505 and stays at the maximum amplitude position, as shown in Figure 7 . In the process of completing the closing operation in the second stopping unit, the electrostatic force of the second electrostatic driving unit plays a major role, and the electrostatic force is greater than the piezoelectric force.

[0084] The closing operation of the fixed beam of the present application is shown in Figure 8 and Figure 9 , which specifically includes the following steps:

[0085] Firstly, the voltage of the second electrostatic driving unit is removed or the voltage of the electrostatic fixed electrode is reduced to make the electrostatic force disappear, and a reverse piezoelectric voltage is applied to the piezoelectric driving unit, so that the fixed beam starts to recover upward by the elastic force of the fixed beam and the reverse piezoelectric force. Alternatively, the voltage of the second electrostatic driving unit is removed, and no reverse piezoelectric voltage is applied to the piezoelectric driving unit, so that the fixed beam starts to recover from the completely upward position to the flat position by the elastic force of the fixed beam.

[0086] During the process of recovering upward to the flat position, the fixed beam is first separated from the second stop unit 505, and then separated from the first stop unit 504.

[0087] In the running stage, the fixed beam of the application includes closing operation and opening operation, and the fixed beam is controlled to switch the position by the electrostatic force, and the fixed beam is assisted to get rid of the maximum amplitude position, that is, the locking position, by the piezoelectric force.

[0088] The third preferred embodiment of the array element of the MEMS loudspeaker driven by piezoelectricity and electrostaticity of the application is shown in Figure 10 The number of stop units is increased, so that the energy loss of the fixed beam during the closing operation and the opening operation is greatly reduced, and the service life of the loudspeaker is improved.

[0089] The application is provided with four rows of sound holes on the upper and lower substrates, respectively, so that the upper and lower substrates are divided into three parts, respectively. For example, the lower substrate is divided into three parts, including a first lower substrate, a second lower substrate and a third lower substrate, and the electrostatic fixed electrode, the dielectric layer and the stop unit are arranged on the first lower substrate, the second lower substrate and the third lower substrate, respectively, as shown in Figure 10 .

[0090] The first stop unit is arranged on the first lower substrate, the second stop unit is arranged on the second lower substrate, and the third stop unit is arranged on the third lower substrate. The positions of the first stop unit and the third stop unit are symmetrical in the closing operation or the opening operation of the fixed beam, so that the heights of the first stop unit and the third stop unit are the same. The second stop unit is located at the maximum amplitude of the fixed beam, and the height of the second stop unit is smaller than the heights of the first stop unit and the third stop unit.

[0091] The three electrostatic fixed electrodes corresponding to the lower substrate are arranged on the fixed beam to form the first electrostatic driving unit. The structure of the upper substrate is the same as that of the lower substrate to form the second electrostatic driving unit.

[0092] The application can also set more rows of sound holes, divide the substrate into more parts, and set stop units on the divided substrate, and the number of stop units is not limited by the application.

[0093] The application preferably sets an electrostatic driving electrode in the support layer 201 below the piezoelectric driving unit, as shown in Fig. 4. Figure 11 The electrostatic driving electrode can also be set in the support layer 201 above the piezoelectric driving unit, as shown in Fig. 5. Figure 12

[0094] The fourth preferred embodiment of the array element of the MEMS loudspeaker driven by piezoelectricity and electrostaticity of the application sets the upper electrode or the lower electrode of the piezoelectric driving unit as the electrostatic driving electrode, so that the structure of the array element is simpler. Specifically, when the piezoelectric driving unit is below the support layer 201, the lower electrode of the piezoelectric driving unit is the same as the electrostatic driving electrode 202, as shown in Fig. 6. Figure 13 When the piezoelectric driving unit is above the support layer 201, the upper electrode of the piezoelectric driving unit is the same as the electrostatic driving electrode 202, as shown in Fig. 7. Figure 14

[0095] The fifth preferred embodiment of the array element of the MEMS loudspeaker driven by piezoelectricity and electrostaticity of the application sets the vibrator, i.e., the diaphragm, as a cantilever beam structure fixed at one end between the upper and lower substrates, as shown in Fig. 8. This embodiment is the array element of the cantilever beam structure, and the cantilever beam is fixed at one side between the upper and lower substrates. The upper and lower substrates are provided with the electrostatic driving unit relative to the surface of the cantilever beam, and the other side of the cantilever beam is the free end. Preferably, for the first electrostatic driving unit, when the support layer in the cantilever beam is below the piezoelectric driving unit, the electrostatic driving electrode is on the lower surface of the support layer, the electrostatic fixed electrode is on the upper surface of the lower substrate, and the dielectric layer covers the upper surface of the electrostatic fixed electrode. Since the vibrator adopts the cantilever beam structure, it has a fixed end and a free end, and therefore the multiple stop units of the application are sequentially lowered in height from the fixed end to the free end. For example, when the stop units are on the dielectric layer, the stop units include two, and the order from the fixed end to the free end of the cantilever beam is the first stop unit and the second stop unit, and the height of the first stop unit is greater than that of the second stop unit. When the vibrator is set as the cantilever beam structure, the upper sound hole and the lower sound hole of the array element are respectively set on the right side of the upper substrate and the left side of the lower substrate, so that the sound short circuit caused by the gap of the free end of the cantilever beam can be effectively avoided. Figure 15 The support layer 201 can also be above the piezoelectric driving unit, and the structure is as shown in Fig. 9.

[0096] Figure 16 ​​​As shown, other structures are consistent with the fifth preferred embodiment of the array element and will not be described again here.

[0097] In a sixth preferred embodiment of the present invention, an array element of a MEMS loudspeaker driven by a piezoelectric and electrostatic combination, the vibrator is a folded cantilever structure, such as Figure 17 、 Figure 18 、 Figure 19 and Figure 20 As shown, Figure 19 The bottom view of the horizontal section along the dotted line AA' is as follows Figure 17 As shown, Figure 19 The top view of the horizontal section along the dotted line BB' is as follows Figure 18 As shown. Figure 17 The longitudinal cross-sectional view along CC' is as follows Figure 19 As shown, in Figure 17 The longitudinal cross-sectional view along DD' is as follows Figure 20 shown.

[0098] In the sixth embodiment of the array element, the vibrator is a folded cantilever, and the structure of the folded cantilever is E-shaped, including a free-vibrating diaphragm in the middle and two fixed diaphragms on both sides. The free-vibrating diaphragm is in the area where the electrostatic drive unit is located. In the startup phase, due to the piezoelectric force of the piezoelectric drive unit 100, bending occurs on the surface of the folded cantilever due to the inverse piezoelectric effect. At this time, the free-vibrating diaphragm in the middle of the folded cantilever and the two fixed diaphragms on both sides have the same bending. The bending generated by the free-vibrating diaphragm and the two fixed diaphragms on both sides cancel each other out, thereby avoiding the initial position deviation of the folded cantilever caused by the piezoelectric force of the piezoelectric drive unit dominating the vibration of the folded cantilever, which affects the sound pressure output.

[0099] The present invention provides a MEMS loudspeaker driven by a piezoelectric and electrostatic composite, comprising a plurality of array elements, which are all the embodiments of the array elements described above in the specification. The plurality of array elements are integrated to form a MEMS loudspeaker array, in which each array element can independently control the displacement state of its diaphragm, i.e., the vibrator, and the entire array realizes the synthesis of sound signals.

[0100] The present invention discloses a MEMS loudspeaker with a piezoelectric and electrostatic composite drive. By adopting the piezoelectric and electrostatic composite drive, the loudspeaker can operate in a high-energy, large-displacement state, generate a higher sound pressure output, and at the same time, has a lower driving voltage, which is convenient for integration with an IC. The present invention adopts a voltage distribution method of the piezoelectric and electrostatic composite drive, and adds a stop structure design, so that the loudspeaker has a longer service life and higher reliability.

[0101] The present invention also includes an electronic device, such as Figure 21As shown, the technical features in any of the embodiments of the MEMS speaker with the above piezoelectric and electrostatic composite driving are included, such as Figure 20 As shown, the electronic device can include a processor 1002, a communications interface 1004, a memory 1006, and a communications bus 1008.

[0102] The processor 1002, the communications interface 1004, and the memory 1006 can communicate with each other through the communications bus 1008.

[0103] The communications interface 1004 is configured to communicate with network elements such as clients or other servers.

[0104] The processor 1002 is configured to execute the program 1010, and can execute the related steps in the above-described embodiments of the processing method of the mail.

[0105] Specifically, the program 1010 can include program code including computer operation instructions.

[0106] The processor 1002 can be a central processing unit CPU, or an application specific integrated circuit ASIC, or one or more integrated circuits configured to implement the embodiments of the present application. The one or more processors included in the terminal can be the same type of processors, such as one or more CPUs; or can be different types of processors, such as one or more CPUs and one or more ASICs.

[0107] The memory 1006 is configured to store the program 1010. The memory 1006 can include a high-speed RAM memory, and can also include a non-volatile memory such as at least one disk memory.

[0108] The digital-to-analog converter 1012 is configured to connect the piezoelectric and electrostatic composite driven MEMS speaker of the present application.

[0109] The piezoelectric and electrostatic composite driven MEMS speaker is also the preferred embodiment of the piezoelectric and electrostatic composite driven speaker in the embodiments of the present application.

[0110] The above is the description of the preferred embodiments of the present application, which can help the skilled in the art to more fully understand the technical solutions of the present application. However, these embodiments are only illustrative, and the specific implementation of the present application should not be limited to the description of these embodiments. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions and transformations can be made, which should be considered as falling within the protection scope of the present application.

Claims

1. A MEMS speaker array element of piezoelectric and electrostatic composite driving, characterized in that, The array element comprises a vibrator generating a sound signal, a fixing unit of the vibrator, and an electrostatic driving unit, the vibrator comprising a piezoelectric driving unit.

2. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 1, wherein, The vibrator comprises a clamped beam, a cantilever beam, or a folded cantilever. 3.The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 1, wherein, In the starting stage, an alternating voltage is applied to the piezoelectric driving unit to make the vibrator vibrate from a horizontal position by resonance effect, and the electrostatic force of the electrostatic driving unit makes the vibrator keep in a high-energy state at the maximum amplitude position; then the vibrator enters the running stage.

4. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 3, wherein, In the starting stage, the piezoelectric driving unit and the electrostatic driving unit work in sequence; or only the piezoelectric driving unit works in the starting stage. Or, in the starting stage, the piezoelectric driving unit and the electrostatic driving unit work simultaneously. Or, in the running stage, only the electrostatic driving unit works, and the piezoelectric driving unit does not work; or in the running stage, the electrostatic driving unit and the piezoelectric driving unit work simultaneously. 5.The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 3, wherein, When the vibrator enters the running stage, the restoring force of the vibrator is the resultant force of the elastic force generated by the rigidity of the vibrator and the restoring force generated by the reverse driving of the piezoelectric driving unit, and the resultant force makes the vibrator deviate from the highest amplitude position. 6.The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 1, wherein, The fixing unit comprises two layers of substrates, and the vibrator is arranged between the two layers of substrates; cavities are formed between the two layers of substrates and the vibrator; an upper sound hole is arranged on the upper substrate, and a lower sound hole is arranged on the lower substrate.

7. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 6, wherein, The upper sound hole and the lower sound hole of the array element are arranged on the right side of the upper substrate and the left side of the lower substrate, or arranged at the center of the upper and lower substrates.

8. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 3, wherein, The electrostatic driving unit comprises two electrostatic fixed electrodes on the inner walls of the two layers of substrates, a continuous medium layer covering the electrostatic fixed electrodes, and two electrostatic driving electrodes on the upper surface and the lower surface of the vibrator. The electrostatic driving electrode on the upper surface of the vibrator, the electrostatic fixed electrode on the inner wall of the upper substrate, and the continuous medium layer covering the electrostatic fixed electrode constitute a first electrostatic driving unit. The electrostatic driving electrode on the lower surface of the vibrator, the electrostatic fixed electrode on the inner wall of the lower substrate, and the continuous medium layer covering the electrostatic fixed electrode constitute a second electrostatic driving unit.

9. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 8, wherein, The high-energy state includes high-position locking and low-position locking; through the interaction of the first electrostatic driving unit and the second electrostatic driving unit, the up-down position of the vibrator is converted, and the high-energy state of the vibrator remains unchanged.

10. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 8, wherein, The electrostatic driving electrode protrudes outside the surface of the vibrator, or the electrostatic driving electrode is embedded in the surface of the vibrator. 11.The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 1, wherein, The electrostatic driving unit is provided with a stopping unit.

12. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 11, wherein, There are multiple stopping units, and the multiple stopping units are arranged in sequence near the position of the maximum amplitude of the vibrator, and the heights of the multiple stopping units decrease in sequence near the position of the maximum amplitude of the vibrator.

13. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 11, wherein, There are two stopping units, including a first stopping unit and a second stopping unit; under the joint action of the piezoelectric driving unit and the electrostatic driving unit, the vibrator is bent; the vibrator contacts the first stopping unit in the process of approaching the position of the maximum amplitude. The piezoelectric force of the piezoelectric driving unit is greater than the electrostatic force of the electrostatic driving unit.

14. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 13, wherein, Under the joint action of the piezoelectric driving unit and the electrostatic driving unit, the vibrator continues to bend downward, contacts the second stop unit and stops at the maximum amplitude position, and the electrostatic force of the electrostatic driving unit is greater than the piezoelectric force of the piezoelectric driving unit.

15. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 11, wherein, The stop unit has three, and four rows of sound holes are arranged on the upper and lower substrates respectively, so that the upper and lower substrates are divided into three parts, including a first lower substrate, a second lower substrate and a third lower substrate; the first lower substrate is provided with a static fixed electrode, a dielectric layer and a first stop unit, the second lower substrate is provided with a static fixed electrode, a dielectric layer and a second stop unit, and the third lower substrate is provided with a static fixed electrode, a dielectric layer and a third stop unit.

16. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 15, wherein, The positions of the first stop unit and the third stop unit are symmetrically arranged at the maximum amplitude of the vibrator, and the heights of the first stop unit and the third stop unit are the same; the second stop unit is located at the maximum amplitude of the vibrator, and the height of the second stop unit is less than the heights of the first stop unit and the third stop unit.

17. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 1, wherein, The vibrator bag also includes a support layer of the piezoelectric driving unit, and the piezoelectric driving unit includes a piezoelectric layer, an upper electrode and a lower electrode.

18. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 17, wherein, The electrostatic driving electrode is arranged in the support layer, and the support layer is located below or above the piezoelectric driving unit.

19. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 17, wherein, The upper electrode or the lower electrode in the piezoelectric driving unit serves as the electrostatic driving electrode.

20. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 17, wherein, When the piezoelectric driving unit is located below the support layer, the lower electrode of the piezoelectric driving unit is the same electrode as the electrostatic driving electrode; when the piezoelectric driving unit is located above the support layer, the upper electrode of the piezoelectric driving unit is the same electrode as the electrostatic driving electrode.

21. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 2, wherein, One side of the cantilever beam is fixed between the upper and lower substrates, and the electrostatic driving unit is arranged on the surface of the cantilever beam opposite to the upper and lower substrates; the other side of the cantilever beam is a free end.

22. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 21, wherein, A plurality of stop units are arranged on the substrate, and the heights of the plurality of stop units decrease in sequence from the fixed end to the free end.

23. The piezoelectric and electrostatic combined actuation MEMS speaker cell of claim 2, wherein, The folded cantilever is in E shape, including a middle free vibration diaphragm and two fixed diaphragms on both sides.

24. The piezoelectric and electrostatic composite-driven MEMS speaker cell of claim 23, wherein, In the starting stage, under the action of the piezoelectric force of the piezoelectric driving unit, the surface of the cantilever beam is bent due to the inverse piezoelectric effect; the middle free vibration diaphragm and the two fixed diaphragms on both sides of the cantilever beam are bent, and the bending of the free vibration diaphragm and the two fixed diaphragms on both sides is offset.

25. The piezoelectric and electrostatic combined actuation MEMS speaker cell of claim 1, wherein, The array element is in square, rectangular or circular shape.

26. A piezoelectric and electrostatic hybrid actuated MEMS loudspeaker, characterized by, The array element of claims 1-25 is integrated to form a MEMS speaker array.

27. An electronic device, comprising: A processor, a memory, a communication interface and a communication bus, the processor, the memory and the communication interface complete communication with each other through the communication bus, and the processor is connected to the piezoelectric and electrostatic composite driven MEMS speaker in claim 26.

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