Audio speaker system using a piezo diaphragm

Abstract

An audio speaker system comprises: an amplifier—the positive input terminal of the amplifier is configured to be coupled to a first reference voltage node—; and a piezo diaphragm, wherein the piezo diaphragm comprises: a metal plate; a first piezo film attached to the metal plate—the first piezo film is configured to function as a speaker during the operation of the audio speaker system—; and a second piezo film attached to the metal plate and spaced apart from the first piezo film, wherein the second piezo film is configured to function as a microphone during the operation of the audio speaker system, the output terminal of the amplifier is coupled to the first piezo film, and the negative input terminal of the amplifier is coupled to the second piezo film.

Description

Technology Field

[0001] Cross-reference for related applications

[0002] This patent application claims priority to U.S. Application No. 18 / 146,718, filed on December 27, 2022, titled "Audio Speaker System Using Piezo Diaphragm," in particular as a continuation of the above, which is incorporated herein by reference as is reproduced in its entirety.

[0003] The present disclosure generally relates to audio speaker systems, and in particular to audio speaker systems constructed using a piezo diaphragm. Background Technology

[0004] Due to their small form factor, piezo speakers are widely used as speakers in devices such as mobile devices or computers. Piezo speakers are typically very thin (e.g., less than 1 mm thick) and are designed to have a nearly flat frequency response within the audio frequency band, such as between 1 kHz and 20 kHz, and, for some special piezo speakers, between 500 Hz and 20 kHz. To achieve a nearly flat frequency response, piezo speakers may be designed to have a multi-layer structure or use special material(s). Consequently, piezo speakers are relatively expensive (e.g., currently costing between $1 and $10 each).

[0005] Piezo diaphragms (also referred to as piezo buzzers) are widely available on the market and generally cost only a fraction (e.g., less than one-third) of the price of piezo speakers. Piezo diaphragms are designed for applications where audio quality is not critical. For example, piezo diaphragms are typically used for alarms, buzzers, etc., where the sound containing most of the tone (e.g., a single frequency) is generated by the piezo diaphragm. When used in a typical circuit configuration (e.g., for use as an alarm or buzzer), the piezo diaphragm has a non-flat frequency response in the audio frequency band, which has multiple peaks and valleys in the frequency response curve. For example, the maximum variation in the frequency response of the piezo diaphragm within the audio frequency band can be as large as, for instance, 30 dB or more. Such poor frequency response can cause severe distortion of the audio signal, which is why piezo diaphragms cannot currently be used as speakers for audio signals such as music and human voices.

[0006] The present disclosure discloses various embodiments in which a piezo diaphragm is used to form an audio speaker system suitable for reproducing audio signals. By using a piezo diaphragm instead of a piezo speaker in an audio speaker system, significant cost reductions can be achieved while maintaining a small form factor.

[0007] According to an embodiment, the audio speaker system comprises: an amplifier—the positive input terminal of the amplifier is configured to be coupled to a first reference voltage node—; and a piezo diaphragm, wherein the piezo diaphragm comprises: a metal plate; a first piezo film attached to the metal plate—the first piezo film is configured to function as a speaker during the operation of the audio speaker system—; and a second piezo film attached to the metal plate and spaced apart from the first piezo film, wherein the second piezo film is configured to function as a microphone during the operation of the audio speaker system, the output terminal of the amplifier is coupled to the first piezo film, and the negative input terminal of the amplifier is coupled to the second piezo film.

[0008] According to an embodiment, the audio speaker system comprises: a piezo diaphragm—the piezo diaphragm comprises: a metal plate; a first piezo film attached to the metal plate; and a second piezo film attached to the metal plate, wherein the second piezo film is at least partially surrounded by the first piezo film and spaced apart from the first piezo film—; and an amplifier, wherein the output terminal of the amplifier is coupled to the first piezo film, the negative input terminal of the amplifier is coupled to the second piezo film, and the positive input terminal of the amplifier is coupled to a first reference voltage node.

[0009] According to an embodiment, a method for reproducing an audio signal using a piezo diaphragm comprises: receiving an audio signal at a positive input terminal of an amplifier or a negative input terminal of an amplifier; supplying a reference voltage to the positive input terminal of an amplifier; transmitting an output signal of an amplifier to a first piezo film of a piezo diaphragm, wherein the first piezo film is configured to convert the output signal of the amplifier into movement of the first piezo film; kinetically coupling the first piezo film to a second piezo film of a piezo diaphragm, wherein the second piezo film is configured to convert the movement of the second piezo film into an electrical signal; and supplying the electrical signal back to the negative input terminal of an amplifier. Brief explanation of the drawing

[0010] Now, for a more complete understanding of the present disclosure and its merits, reference is made to the following description taken together with the accompanying drawings: FIG. 1 illustrates the frequency response of a piezo diaphragm in a conventional application of a piezo diaphragm in an embodiment; FIGS. 2A and 2B illustrate various drawings of a piezo diaphragm in an embodiment; FIGS. 3 to 5 illustrate various embodiments of a piezo diaphragm; FIG. 6 illustrates a symbol for a piezo diaphragm in an embodiment; FIG. 7 illustrates an audio speaker system constructed using a piezo diaphragm in an embodiment; FIG. 8 illustrates an audio speaker system constructed using a piezo diaphragm in another embodiment; FIG. 9 illustrates an audio speaker system constructed using a piezo diaphragm in another embodiment; FIG. 10 illustrates the frequency response of a piezo diaphragm used in an audio speaker system in an embodiment; FIG. 11 illustrates a flowchart of a method for playing an audio signal using a piezo diaphragm in some embodiments. Specific details for implementing the invention

[0011] The creation and use of the examples disclosed herein are discussed in detail below. However, it should be recognized that the present disclosure provides a number of applicable inventive concepts that can be implemented in a wide variety of specific contexts. The specific examples discussed merely illustrate specific ways of creating and using the present disclosure and do not limit the scope of the present disclosure. Throughout the discussion herein, unless otherwise specified, identical or similar reference numbers or labels in different drawings refer to identical or similar components or signals.

[0012] The present disclosure will be described with respect to examples of a specific context, namely, an audio speaker system constructed using a piezo diaphragm.

[0013] FIG. 1 illustrates the frequency response of a piezo diaphragm in a conventional application of a piezo diaphragm in an embodiment. In such an application, the piezo diaphragm is used to generate a sound (e.g., a tone) for, for example, an alarm, a buzzer, etc.

[0014] In FIG. 1, curve (11) illustrates the sound pressure level (SPL) of the piezo diaphragm, and curve (13) illustrates the impedance of the piezo diaphragm. As illustrated in FIG. 1, the amplitude of the frequency response (e.g., curve (11)) varies significantly within the audio frequency band. Multiple peaks and valleys are observed in the frequency response of FIG. 1. The maximum variation in the frequency response can be as large as, for example, 30 dB or more. Such poor frequency response can cause severe distortion in audio signals (e.g., music, human voice, etc.) containing multiple and / or continuous frequency components across the audio frequency band. Therefore, conventional speaker systems constructed using piezo diaphragms are not suitable for reproducing audio signals.

[0015] FIGS. 2A and FIGS. 2B illustrate a plan view and a cross-sectional view of a piezo diaphragm (100A) in an embodiment, respectively. FIGS. 2B illustrates a cross-sectional view of a piezo diaphragm (100A) along cross-section D-D' of FIGS. 2A.

[0016] As illustrated in FIGS. 2a and 2b, the piezo diaphragm (100A) comprises a plate (101), a first piezo film (103), and a second piezo film (105). In some embodiments, the plate (101) is a metal plate, such as a brass plate, a nickel-alloy plate, etc. In some embodiments, the first piezo film (103) and the second piezo film (105) are formed from the same piezoelectric material. In other embodiments, the first piezo film (103) and the second piezo film (105) are formed from different piezoelectric materials.

[0017] A layer of piezoelectric material is deposited on a plate (101), and then the deposited piezoelectric material is patterned to remove a portion of the deposited piezoelectric material (e.g., by etching using an etching mask having a mask pattern), thereby forming a first piezofilm (103) and a second piezofilm (105). After patterning, the remaining portion of the deposited piezoelectric material forms the first piezofilm (103) and the second piezofilm (105). In another embodiment, each of the first piezofilm (103) and the second piezofilm (105) may be pre-formed as a layer of dielectric material having a predetermined shape, and then the pre-formed first piezofilm (103) and the pre-formed second piezofilm are attached (e.g., bonded) to the plate (101).

[0018] In the example of FIG. 2a, the plate (101) has a circular shape. The first piezo film (103) has a circular shape with a slit. The inner part of the slit has a test tube shape, and the outer part of the slit has an enlarged and curved shape. In the illustrated example, the second piezo film (105) is placed within the slit of the first piezo film (103) and may have a geometric shape similar to the slit. For example, the second piezo film (105) may have one end having a test tube shape and the other end having an enlarged portion. As illustrated in FIG. 2a, the second piezo film (105) is at least partially surrounded by the first piezo film (103). Note that the second piezo film (105) is spaced apart from the first piezo film (103), and there is a gap (104) (e.g., empty space) between the second piezo film (105) and the first piezo film (103). The shape and relative position of the first piezo film (103) and the second piezo film (105) allow for good coupling (e.g., kinetic coupling) between the first piezo film (103) and the second piezo film (105). For example, vibration of the first piezo film (103) causes the same or similar vibration of the second piezo film (105).

[0019] FIG. 2a shows three terminals of a piezo diaphragm (100A): terminals attached to the first piezo film (103). A , terminal attached to the second piezo film (105) B and a third terminal attached to the plate (101) C Further examples are provided. In some embodiments, a conductive wiring component (e.g., copper wire, metal connector, etc.) is bonded (e.g., soldered) to an individual component (e.g., 103, 105, or 101) of a piezo diaphragm (100A), thereby forming a terminal A , b and C Each can be formed.

[0020] In the illustrated embodiment, during the operation of the piezo diaphragm (100A) (e.g., as a speaker in an audio speaker system), the terminal C It is coupled to a reference voltage such as electrical ground. Terminal A It is configured to receive an (amplified) audio signal (e.g., a time-variable electric voltage that conveys audio information). The first piezo film (103) is configured to convert the audio signal (e.g., an electric signal) into movement (e.g., vibration) of the first piezo film (103) to generate audio sound. In other words, the first piezo film (103) is configured to function as a speaker. The movement (e.g., vibration) of the first piezo film (103) is picked up (e.g., detected) by the second piezo film (105) through the motion coupling between the first piezo film (103) and the second piezo film (105), causing movement (e.g., vibration) of the second piezo film (105). The second piezo film (105) generates an electric signal in response to that movement. In other words, the second piezo film (105) functions as a microphone, which converts the audio sound generated by the first piezo film (103) into an electrical signal, and this electrical signal is fed back to the negative input terminal of the amplifier of the audio speaker system. The amplifier generates an amplified audio signal that is transmitted to the first piezo film (103). Details are discussed below.

[0021] FIGS. 3 to 5 illustrate various embodiments of a piezo diaphragm. In particular, FIGS. 3, 4, and 5 illustrate plan views of a piezo diaphragm (100B), a piezo diaphragm (100C), and a piezo diaphragm (100D), respectively. The structure and function of the piezo diaphragms (100B, 100C, and 100D) are similar to those of the piezo diaphragm (100A), but the shapes of the first piezo film (103), the second piezo film (105), and / or plate (101) are different.

[0022] The piezo diaphragm (100B) of FIG. 3 is similar to the piezo diaphragm (100A), but the first piezo film (103) of FIG. 3 has a circular shape in which a circular portion is removed to form a recessed area. The second piezo film (105) of the piezo diaphragm (100B) has a (smaller) circular shape and is placed within the recessed area.

[0023] The piezo diaphragm (100C) of FIG. 4 is similar to the piezo diaphragm (100A), but the slit of the first piezo film (103) of FIG. 4 has a rectangular shape, and the second piezo film (105) of the piezo diaphragm (100C) also has a rectangular shape and is placed within the rectangular slit of the first piezo film (103) of FIG. 4.

[0024] The piezo diaphragm (100D) of FIG. 5 is similar to the piezo diaphragm (100C) in that there are rectangular slits in the first piezo film (103) and the second piezo film (105) which has a rectangular shape. However, the plate (101) of FIG. 5 has a rectangular shape, and the first piezo film (103) also has a rectangular shape.

[0025] Various embodiments of the piezo diaphragm illustrated in FIGS. 2a, 2b and FIGS. 3 through 5 are exemplary and non-limiting. Other shapes and / or structures for the piezo diaphragm are also possible and are intended to be fully included within the scope of this disclosure. The piezo diaphragms described herein (e.g., 100A, 100B, 100C, and 100D) have three terminals (e.g., A , B and CNote that it belongs to self-drive type piezo diaphragms, which have a ) and, when used as a buzzer, can be used to form an oscillation circuit to internally generate a frequency signal (e.g., a tone). Self-drive type piezo diaphragms are different from external-drive type piezo diaphragms, which have two terminals and must be supplied with an external frequency signal (e.g., a tone) to generate sound (e.g., an alarm or a buzzer). The piezo diaphragm used to construct the audio speaker system discussed herein is a self-drive type piezo diaphragm.

[0026] FIG. 6 illustrates a symbol for a piezo diaphragm (100) in an embodiment. The piezo diaphragm (100) may represent any suitable magnetic-driven type of piezo diaphragm, such as piezo diaphragms (100A, 100B, 100C, and 100D). The symbol illustrated in FIG. 6 is used to represent a piezo diaphragm used in an audio speaker system in subsequent drawings. As illustrated in FIG. 6, the symbol illustrates a plate (101), a first piezo film (103) (illustrated as a speaker icon), and a second piezo film (105) (illustrated as a microphone icon). The dashed arrow in FIG. 6 illustrates a connection (e.g., kinetic connection) between the first piezo film (103) and the second piezo film (105). The symbol in FIG. 6 is a terminal of the piezo diaphragm (100). A , B and C Provides additional examples.

[0027] FIG. 7 illustrates an audio speaker system (200A) in an embodiment. The audio speaker system (200A) is suitable for playing audio signals such as music and voice and is formed using a piezo diaphragm (100). The piezo diaphragm (100) may be any suitable piezo diaphragm, such as a piezo diaphragm (100A, 100B, 100C, 100D) or a commercially available (e.g., off-the-shelf) magnetic-driven type piezo diaphragm. For simplification, FIG. 7 may not illustrate all features of the audio speaker system (200A).

[0028] As illustrated in FIG. 7, the audio speaker system (200A) includes a piezo diaphragm (100) and an amplifier (111). The amplifier (111) may be an audio amplifier, such as an operational amplifier, for example. In the example of FIG. 7, the amplifier (111) is a supply voltage V DD It is coupled between a power supply having (e.g., 3V, 5V, etc.) and a reference voltage node (112) coupled to electrical ground. The output terminal (118) of the amplifier (111) is the terminal of the piezo diaphragm (100). A It is coupled to and provides an amplified audio signal to a first piezo film (103) (functioning as a speaker). Terminal of the piezo diaphragm (100). B It outputs an electrical signal (e.g., a voltage signal) generated by the second piezo film (105). Terminal of the piezo diaphragm (100). C It is connected to, for example, a reference voltage node (106) connected to an electric ground.

[0029] Referring still to Fig. 7, the reference voltage V REF It is applied to the node (114) coupled to the positive input terminal (115) of the amplifier (111). Reference voltage V REF has a fixed nominal value, for example, the supply voltage V DD It could be half of.

[0030] An audio signal (e.g., a time-variable voltage signal conveying audio information) is applied to node (121), and node (121) is a capacitor connected in series C 1 and resistors R It is coupled to the negative input terminal (113) of the amplifier (111) through 3. In some embodiments, a capacitor C 1 functions as a high-pass filter to block (e.g., filter) low-frequency components (e.g., DC components) of the audio signal.

[0031] As exemplified in Fig. 7, the resistor R 1 and resistor R 2 is a terminal of the piezo diaphragm (100). B It is coupled in series between and the reference voltage node (117). In the illustrated embodiment, the reference voltage node (117) is coupled to electrical ground. Resistor R 1 and R The node (116) between the two is also connected to the negative input terminal (113) of the amplifier (111).

[0032] During the operation of the audio speaker system (200A), the audio signal applied to the node (121) is (for example, to remove low-frequency components such as DC components) capacitor CIt is filtered by 1. The filtered audio signal is transmitted to an amplifier (111) and amplified by the amplifier (111). At the output terminal (118) of the amplifier (111), the amplified audio signal drives (e.g., excites) the first piezo film (103), and the movement (e.g., vibration) of the first piezo film (103) generates audio sound (e.g., music or voice). The movement (e.g., vibration) of the first piezo film (103), through kinematic coupling, causes the same or similar movement (e.g., vibration) of the second piezo film (105), and the second piezo film (105) functions as a microphone and converts the audio sound into an electrical signal (e.g., voltage signal). The electrical signal is fed back to the negative input terminal (113) of the amplifier (111). In the example of FIG. 7, the terminal B The scaled version of the electrical signal is a resistor R 1 and R A feedback voltage is formed by the voltage divider formed by 2 and combined with the filtered audio signal (e.g., added together), and this feedback voltage is then applied to the negative input terminal (113) of the amplifier (111).

[0033] FIG. 8 illustrates an audio speaker system (200B) in another embodiment. The audio speaker system (200B) is similar to the audio speaker system (200A), but the audio signal is applied to a node (131), and this node (131) is a capacitor C 1 It is coupled to the positive input terminal (115) of the amplifier (111) through. In addition, the reference voltage V REF A is applied to the node (124), and this node (124) is a resistor R 3It is coupled to the positive input terminal (115) of the amplifier (111) through. The operation of the audio speaker system (200B) is similar to that of the audio speaker system (200A), and therefore details are not discussed here. In both audio speaker systems (200A and 200B), the terminal B Note that the electrical signal is fed back to the negative input terminal (113) of the amplifier.

[0034] FIG. 9 illustrates an audio speaker system (300) in another embodiment. The audio speaker system (300) is similar to the audio speaker system (200B) (or 200A), but is less detailed to illustrate the speaker system at a higher level of abstraction. For example, FIG. 9 shows the terminals of a piezo diaphragm (100). B It is illustrated that the electrical signal from is fed back to the negative input terminal (113) of the amplifier, which is one of several features that differ from conventional circuit configurations using a piezo diaphragm (100) in applications such as alarms or buzzers. The amplifier (111) and piezo diaphragm (100) of FIG. 9 represent a high-level abstraction of audio speaker systems (200A and 200B).

[0035] In addition, in FIG. 9, an audio signal is applied to node (201). Then, the audio signal is processed by a preamplifier (203) (e.g., an audio preamplifier). Then, the output of the preamplifier (203) may be processed by a tone and volume control circuit (205), which may be, for example, a filter, rather than adjusting the gain and / or phase of the audio signal at different frequencies of the audio frequency band. In some embodiments, one or both of the preamplifier (203) and the tone and volume control circuit (205) are omitted. In some embodiments, the audio signal at the output of the tone and volume control circuit (205) is applied to node (121) in FIG. 7 or node (131) in FIG. 8.

[0036] Modifications and variations of the present disclosure are possible and are intended to be fully contained within the scope of the present disclosure. For example, the examples of FIGS. 7, 8, and 9 use single-ended signals as non-limiting examples. A person skilled in the art will readily recognize that the principles of the present disclosure apply to differential signals and that the disclosed embodiments can be easily adapted to differential signals. Furthermore, the disclosed embodiments can be used with various types of amplifiers, such as Class A, Class AB, Class D, Class G, and Class H amplifiers.

[0037] FIG. 10 illustrates the frequency response of a piezo diaphragm used in an audio speaker system in an embodiment. The audio speaker system may be, for example, an audio speaker system (200A, 200B, or 300).

[0038] In FIG. 10, curve (21) illustrates the sound pressure level (SPL) of the piezo diaphragm, and curve (23) illustrates the impedance of the piezo diaphragm. As illustrated in FIG. 10, the amplitude of the frequency response (e.g., curve (21)) remains substantially flat within the audio frequency band (e.g., between 1 kHz and 20 kHz). In some embodiments, within the audio frequency band, the maximum variation of the frequency response from the average value of the frequency response is less than 3 dB. For example, the amplitude of the frequency response may be within ±3 dB of the average value of the frequency response amplitude in the audio frequency band. This substantially flat frequency response allows for the generation of high-quality audio signals (e.g., music, human voice, etc.) using the piezo diaphragm.

[0039] FIG. 11 illustrates a flowchart of a method for playing an audio signal using a piezo diaphragm in some embodiments. It should be understood that the exemplary method illustrated in FIG. 11 is merely one example of a number of possible exemplary methods. A person skilled in the art will recognize a number of variations, alternatives, and modifications. For example, as illustrated in FIG. 11, various steps may be added, removed, replaced, rearranged, or repeated.

[0040] Referring to FIG. 11, in block (1010), an audio signal is received at the positive input terminal or the negative input terminal of the amplifier. In block (1020), a reference voltage is supplied to the positive input terminal of the amplifier. In block (1030), the output signal of the amplifier is transmitted to a first piezo film of a piezo diaphragm, wherein the first piezo film is configured to convert the output signal of the amplifier into movement of the first piezo film. In block (1040), the first piezo film is kinetically coupled to a second piezo film of a piezo diaphragm, wherein the second piezo film is configured to convert the movement of the second piezo film into an electrical signal. In block (1050), the electrical signal is supplied back to the negative input terminal of the amplifier.

[0041] The embodiments can achieve the advantages described below. For example, the audio speaker system disclosed herein is formed using a piezo diaphragm. The disclosed circuit configuration of the audio speaker system allows the audio speaker system to achieve an excellent frequency response that was previously impossible to achieve using a piezo diaphragm. Because the piezo diaphragm is much cheaper than a piezo speaker and has nearly the same form factor (e.g., size), the disclosed audio speaker system (using a piezo diaphragm) can be used to replace speaker systems currently in use and formed using piezo speakers, which are much more expensive.

[0042] Examples of the present disclosure are summarized herein. Other examples may also be understood from the entire specification and claims filed herein.

[0043] Example 1: According to an embodiment, an audio speaker system comprises: an amplifier - the positive input terminal of the amplifier is configured to be coupled to a first reference voltage node -; and a piezo diaphragm, wherein the piezo diaphragm comprises: a metal plate; a first piezo film attached to the metal plate - the first piezo film is configured to function as a speaker during the operation of the audio speaker system -; and a second piezo film attached to the metal plate and spaced apart from the first piezo film, wherein the second piezo film is configured to function as a microphone during the operation of the audio speaker system, the output terminal of the amplifier is coupled to the first piezo film, and the negative input terminal of the amplifier is coupled to the second piezo film.

[0044] Example 2: As an audio speaker system of Example 1, during the operation of the audio speaker system, a microphone formed by the second piezo film is kinetically coupled to a speaker formed by the first piezo film.

[0045] Example 3: An audio speaker system of Example 1 further comprises a first resistor and a second resistor coupled in series between a second piezo film and a second reference voltage node, and the negative input terminal of the amplifier is coupled to a first node between the first resistor and the second resistor.

[0046] Example 4: An audio speaker system of Example 3 further comprises a capacitor and a third resistor coupled in series between the negative input terminal of an amplifier and a second node, and the second node is configured to receive an audio signal.

[0047] Example 5: As an audio speaker system of Example 4, the second reference voltage node is configured to be coupled to electrical ground, and the first reference voltage node is configured to be coupled to a voltage supply having a voltage higher than electrical ground.

[0048] Example 6: An audio speaker system of Example 3 further comprises a capacitor coupled between the second node and the positive input terminal of the amplifier—the second node is configured to receive an audio signal—; and a third resistor coupled between the positive input terminal of the amplifier and the first reference voltage node.

[0049] Example 7: As the audio speaker system of Example 6, during the operation of the audio speaker system, the voltage at the second reference voltage node is equal to the electrical ground, and the voltage at the first reference voltage node is higher than the electrical ground.

[0050] Example 8: As the audio speaker system of Example 1, the audio speaker system has a frequency response within a frequency band between 1 kHz and 20 kHz, and the amplitude change of the frequency response within the frequency band is less than 3 dB.

[0051] Example 9: As an audio speaker system of Example 1, it further includes an audio preamplifier coupled between the input terminal of the audio speaker system and the positive input terminal of the amplifier.

[0052] Example 10: As an audio speaker system of Example 9, it further includes a tone and volume control circuit coupled between the audio preamplifier and the positive input terminal of the amplifier.

[0053] Example 11: According to an embodiment, an audio speaker system comprises: a piezo diaphragm - the piezo diaphragm comprises: a metal plate; a first piezo film attached to the metal plate; and a second piezo film attached to the metal plate, wherein the second piezo film is at least partially surrounded by the first piezo film and spaced apart from the first piezo film -; and an amplifier, wherein the output terminal of the amplifier is coupled to the first piezo film, the negative input terminal of the amplifier is coupled to the second piezo film, and the positive input terminal of the amplifier is configured to be coupled to a first reference voltage node.

[0054] Example 12: As an audio speaker system of Example 11, during the operation of the audio speaker system, a first piezo film is configured to convert a first electrical signal at the output terminal of an amplifier into movement of the first piezo film, and a second piezo film is configured to be kinetically coupled to the first piezo film and to convert the movement of the second piezo film into a second electrical signal.

[0055] Example 13: As an audio speaker system of Example 12, the second piezo film is coupled to a voltage divider comprising a first resistor and a second resistor coupled in series, and the first node between the first resistor and the second resistor is coupled to the negative input terminal of the amplifier.

[0056] Example 14: An audio speaker system of Example 13 further comprises a capacitor and a third resistor coupled in series between a first node and a second node, and the second node is configured to receive an audio signal.

[0057] Example 15: An audio speaker system of Example 13 further comprises a third resistor coupled between the positive input terminal of an amplifier and a first reference voltage node; and a capacitor coupled between the positive input terminal of an amplifier and a second node, wherein the second node is configured to receive an audio signal.

[0058] Example 16: As the audio speaker system of Example 11, the piezo diaphragm has a frequency response in a frequency band between 1 kHz and 20 kHz during the operation of the audio speaker system, and the maximum change in the amplitude of the frequency response is less than 3 dB in the frequency band.

[0059] Example 17: According to an embodiment, a method for reproducing an audio signal using a piezo diaphragm comprises: receiving an audio signal at a positive input terminal of an amplifier or a negative input terminal of an amplifier; supplying a reference voltage to the positive input terminal of an amplifier; transmitting an output signal of an amplifier to a first piezo film of a piezo diaphragm, wherein the first piezo film is configured to convert the output signal of the amplifier into movement of the first piezo film; kinetically coupling the first piezo film to a second piezo film of a piezo diaphragm, wherein the second piezo film is configured to convert the movement of the second piezo film into an electrical signal; and supplying the electrical signal back to the negative input terminal of an amplifier.

[0060] Example 18: As a method of Example 17, the step of resupplying the electrical signal includes: the step of generating a scaled version of the electrical signal using a voltage divider; and the step of transmitting the scaled version of the electrical signal to the negative input terminal of an amplifier.

[0061] Example 19: As a method of Example 17, the step of receiving an audio signal includes the step of receiving an audio signal at a first node, and a capacitor and a resistor are coupled in series between the first node and the negative input terminal of the amplifier.

[0062] Example 20: As a method of Example 17, the step of receiving an audio signal includes the step of receiving an audio signal at a first node, a capacitor is coupled between the first node and the positive input terminal of an amplifier, the step of supplying a reference voltage includes the step of supplying a reference voltage to a second node, and a resistor is coupled between the second node and the positive input terminal of an amplifier.

[0063] Although the present disclosure has been described by reference to exemplary examples, this description is not intended to be interpreted in a limiting sense. Various modifications and combinations of the exemplary examples, as well as other examples of the present disclosure, will become apparent to those skilled in the art upon reference to the description. Accordingly, the appended claims are intended to encompass any such modifications or examples.

Claims

Claim 1 As an audio speaker system, an amplifier—the positive input terminal of said amplifier is configured to be coupled to a first reference voltage node—; and a piezo diaphragm, said piezo diaphragm comprising: a metal plate; a first piezo film attached to said metal plate—said the first piezo film has a circular shape with a slit, said inner portion of the slit has a test tube shape, said outer portion of the slit has an enlarged and curved shape, said first piezo film is configured to function as a speaker during the operation of said audio speaker system—; An audio speaker system comprising a second piezo film attached to the metal plate, wherein the second piezo film is at least partially surrounded by the first piezo film and spaced apart from the first piezo film, and the second piezo film has a geometric shape similar to the slit and is configured to function as a microphone during the operation of the audio speaker system, wherein the output terminal of the amplifier is coupled to the first piezo film and the negative input terminal of the amplifier is coupled to the second piezo film. Claim 2 An audio speaker system according to claim 1, wherein, during the operation of the audio speaker system, the microphone formed by the second piezo film is kinetically coupled to the speaker formed by the first piezo film. Claim 3 An audio speaker system according to claim 1 or 2, further comprising a first resistor and a second resistor coupled in series between the second piezo film and the second reference voltage node, wherein the negative input terminal of the amplifier is coupled to a first node between the first resistor and the second resistor. Claim 4 An audio speaker system according to paragraph 3, wherein the second reference voltage node is configured to be coupled to an electrical ground, and the first reference voltage node is configured to be coupled to a voltage supply having a voltage higher than the electrical ground. Claim 5 An audio speaker system according to paragraph 3, further comprising a capacitor and a third resistor coupled in series between the negative input terminal of the amplifier and a second node, wherein the second node is configured to receive an audio signal. Claim 6 An audio speaker system according to paragraph 3, further comprising: a capacitor coupled between a second node and the positive input terminal of the amplifier—the second node is configured to receive an audio signal—; and a third resistor coupled between the positive input terminal of the amplifier and the first reference voltage node. Claim 7 In claim 6, during the operation of the audio speaker system, the voltage at the second reference voltage node is equal to the electrical ground, and the voltage at the first reference voltage node is higher than the electrical ground, the audio speaker system. Claim 8 An audio speaker system according to claim 1 or 2, wherein the audio speaker system has a frequency response within a frequency band between 1 kHz and 20 kHz, and the amplitude change of the frequency response within the frequency band is less than 3 dB. Claim 9 An audio speaker system according to claim 1 or 2, further comprising an audio preamplifier coupled between the input terminal of the audio speaker system and the positive input terminal of the amplifier. Claim 10 An audio speaker system according to claim 9, further comprising a tone and volume control circuit coupled between the audio preamplifier and the positive input terminal of the amplifier. Claim 11 As an audio speaker system, the piezo diaphragm — said piezo diaphragm comprises: a metal plate; a first piezo film attached to said metal plate — said first piezo film has a circular shape with a slit, said inner portion of the slit has a test tube shape, said outer portion of the slit has an enlarged and curved shape, said first piezo film is configured to function as a speaker during operation of said audio speaker system —; and a second piezo film attached to said metal plate, said second piezo film is at least partially surrounded by said first piezo film and spaced apart from said first piezo film, said second piezo film has a geometric shape similar to said slit, said second piezo film is configured to function as a microphone during operation of said audio speaker system —; An audio speaker system comprising an amplifier, wherein the output terminal of the amplifier is coupled to the first piezo film, the negative input terminal of the amplifier is coupled to the second piezo film, and the positive input terminal of the amplifier is coupled to the first reference voltage node. Claim 12 An audio speaker system according to claim 11, wherein, during the operation of the audio speaker system, the first piezo film is configured to convert a first electrical signal at the output terminal of the amplifier into movement of the first piezo film, and the second piezo film is configured to be kinetically coupled to the first piezo film and to convert the movement of the second piezo film into a second electrical signal. Claim 13 An audio speaker system according to claim 11 or 12, wherein the second piezo film is coupled to a voltage divider comprising a first resistor and a second resistor coupled in series, and the first node between the first resistor and the second resistor is coupled to the negative input terminal of the amplifier. Claim 14 An audio speaker system according to claim 13, further comprising a capacitor and a third resistor coupled in series between the first node and the second node, wherein the second node is configured to receive an audio signal. Claim 15 An audio speaker system according to claim 13, further comprising: a third resistor coupled between the positive input terminal of the amplifier and the first reference voltage node; and a capacitor coupled between the positive input terminal of the amplifier and the second node, wherein the second node is configured to receive an audio signal. Claim 16 An audio speaker system according to claim 11 or 12, wherein the piezo diaphragm has a frequency response in a frequency band between 1 kHz and 20 kHz during operation of the audio speaker system, and the maximum change in the amplitude of the frequency response is less than 3 dB in the frequency band. Claim 17 An audio speaker system according to claim 11 or 12, further comprising an audio preamplifier coupled between the input terminal of the audio speaker system and the positive input terminal of the amplifier. Claim 18 A method for reproducing an audio signal using a piezo diaphragm, wherein the method comprises: receiving an audio signal at a positive input terminal of an amplifier or at a negative input terminal of the amplifier; supplying a reference voltage to the positive input terminal of the amplifier; transmitting an output signal of the amplifier to a first piezo film of the piezo diaphragm, wherein the first piezo film has a circular shape with a slit, the inner portion of the slit has a test tube shape, the outer portion of the slit has an enlarged and curved shape, and the first piezo film is configured to convert the output signal of the amplifier into movement of the first piezo film; and kinetically coupling the first piezo film to a second piezo film of the piezo diaphragm through a metal plate, wherein the first piezo film and the second piezo film are attached to the metal plate, and the second piezo film is at least partially surrounded by the first piezo film and has a geometric shape similar to the slit, and the second A method configured to convert the movement of a piezo film into an electrical signal; and comprising the step of supplying the electrical signal back to the negative input terminal of the amplifier. Claim 19 In claim 18, the step of supplying the electrical signal again comprises: generating a scaled version of the electrical signal using a voltage divider; and transmitting the scaled version of the electrical signal to the negative input terminal of the amplifier. Claim 20 A method according to claim 18 or 19, wherein the step of receiving the audio signal includes the step of receiving the audio signal at a first node, and the capacitor and resistor are coupled in series between the first node and the negative input terminal of the amplifier. Claim 21 A method according to claim 18 or 19, wherein the step of receiving the audio signal includes the step of receiving the audio signal at a first node, a capacitor is coupled between the first node and the positive input terminal of the amplifier, the step of supplying the reference voltage includes the step of supplying the reference voltage to a second node, and a resistor is coupled between the second node and the positive input terminal of the amplifier. Claim 22 In claim 18, the step of receiving the audio signal comprises: receiving the audio signal by a preamplifier; and processing the audio signal by the preamplifier to produce a first output of the preamplifier. Claim 23 A method according to claim 22, further comprising the step of supplying the first output to the positive input terminal of the amplifier. Claim 24 A method according to claim 22, further comprising the steps of: processing a first output of the preamplifier by the tone and volume control circuit to generate a second output of the tone and volume control circuit; and supplying the second output to the positive input terminal of the amplifier.

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