Audio speaker system using a piezoelectric diaphragm

Abstract

The audio speaker system includes an amplifier, the amplifier having a positive input terminal configured to be coupled to a first reference voltage node; and a piezoelectric diaphragm, the piezoelectric diaphragm including a metal plate; a first piezoelectric film attached to the metal plate, the first piezoelectric film configured to function as a speaker during operation of the audio speaker system; and a second piezoelectric film attached to the metal plate and spaced apart from the first piezoelectric film, the second piezoelectric film configured to function as a microphone during operation of the audio speaker system, an output terminal of the amplifier coupled to the first piezoelectric film and a negative input terminal of the amplifier coupled to the second piezoelectric film.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims priority to, and is specifically a continuation of, U.S. patent application Ser. No. 18 / 146,718, entitled "Audio Speaker System Using Piezo Diaphragm," filed December 27, 2022, which is incorporated herein by reference as if reproduced in its entirety.

[0002]

[0002] The present disclosure relates generally to audio speaker systems, and more particularly to audio speaker systems constructed using piezoelectric diaphragms. [Background technology]

[0003]

[0003] Piezoelectric speakers are widely used as speakers for mobile devices, computers, and the like due to their small form factor. Piezoelectric speakers are typically very thin (e.g., less than 1 mm thick) and designed to have a nearly flat frequency response within an audible frequency range, such as 1 KHz to 20 KHz, or 500 Hz to 20 KHz for some specialized piezoelectric speakers. To achieve a nearly flat frequency response, piezoelectric speakers can be designed to have a multi-layer structure and / or use special materials. As a result, piezoelectric speakers are relatively expensive (e.g., currently between $1 and $10 each). Summary of the Invention [Problem to be solved by the invention]

[0004] Piezoelectric diaphragms (also known as piezoelectric buzzers) are widely available on the market and typically cost a fraction (e.g., one-third or less) of the price of piezoelectric speakers. Piezoelectric diaphragms are designed for applications where sound quality is not an issue. For example, piezoelectric diaphragms are typically used in alarms, buzzers, and other applications, where the sound produced by the piezoelectric diaphragm is mostly tonal (e.g., single-frequency). When used in a typical circuit configuration (e.g., for use as an alarm or buzzer), piezoelectric diaphragms have an uneven frequency response across the audio frequency band, with many peaks and valleys in the frequency response curve. For example, the maximum variation in the frequency response of a piezoelectric diaphragm within the audio frequency band can be as large as 30 dB or more. This poor frequency response can cause severe distortion of the audio signal, which is why piezoelectric diaphragms cannot currently be used as speakers for audio signals such as music or the human voice.

[0005]

[0005] This disclosure discloses various embodiments in which a piezoelectric diaphragm is used to form an audio speaker system suitable for reproducing audio signals. By using a piezoelectric diaphragm instead of a piezoelectric speaker in an audio speaker system, significant cost savings can be achieved while maintaining a small form factor. [Means for solving the problem]

[0006]

[0006] According to one embodiment, an audio speaker system includes an amplifier, the amplifier having a positive input terminal configured to be coupled to a first reference voltage node; a piezoelectric diaphragm, the piezoelectric diaphragm including a metal plate, a first piezoelectric film attached to the metal plate, the first piezoelectric film configured to function as a speaker during operation of the audio speaker system, and a second piezoelectric film attached to the metal plate and spaced apart from the first piezoelectric film, the second piezoelectric film configured to function as a microphone during operation of the audio speaker system, the output terminal of the amplifier coupled to the first piezoelectric film and the negative input terminal of the amplifier coupled to the second piezoelectric film.

[0007]

[0007] According to one embodiment, an audio speaker system includes a piezoelectric diaphragm including a metal plate, a first piezoelectric film attached to the metal plate, and a second piezoelectric film attached to the metal plate, the second piezoelectric film being at least partially surrounded by the first piezoelectric film and spaced apart from the first piezoelectric film; and an amplifier configured such that an output terminal of the amplifier is coupled to the first piezoelectric film, a negative input terminal of the amplifier is coupled to the second piezoelectric film, and a positive input terminal of the amplifier is coupled to a first reference voltage node.

[0008]

[0008] According to one embodiment, a method for reproducing an audio signal using a piezoelectric diaphragm includes the steps of receiving an audio signal at a positive input terminal of an amplifier or 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 piezoelectric film of the piezoelectric diaphragm, the first piezoelectric film being configured to convert the output signal of the amplifier into movement of the first piezoelectric film, kinematically coupling the first piezoelectric film to a second piezoelectric film of the piezoelectric diaphragm, the second piezoelectric film being configured to convert movement of the second piezoelectric film into an electrical signal, and feeding the electrical signal back to the negative input terminal of the amplifier.

[0009] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 illustrates the frequency response of a piezoelectric diaphragm in a conventional application of the piezoelectric diaphragm, according to one embodiment. [Figure 2A] FIG. 1 illustrates a piezoelectric diaphragm in one embodiment. [Figure 2B] FIG. 1 illustrates a piezoelectric diaphragm in one embodiment. [Figure 3] FIG. 1 illustrates one embodiment of a piezoelectric diaphragm. [Figure 4] FIG. 1 illustrates one embodiment of a piezoelectric diaphragm. [Figure 5] FIG. 1 illustrates one embodiment of a piezoelectric diaphragm. [Figure 6] FIG. 1 illustrates a symbol for a piezoelectric diaphragm in one embodiment. [Figure 7] FIG. 1 illustrates an audio speaker system constructed using a piezoelectric diaphragm, in one embodiment. [Figure 8]FIG. 1 illustrates an audio speaker system constructed using a piezoelectric diaphragm in another embodiment. [Figure 9] FIG. 10 illustrates an audio speaker system constructed using a piezoelectric diaphragm in yet another embodiment. [Figure 10] FIG. 2 illustrates the frequency response of a piezoelectric diaphragm used in an audio speaker system, in one embodiment. [Figure 11] FIG. 1 illustrates a flowchart of a method for reproducing an audio signal using a piezoelectric diaphragm, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0019] Making and using embodiments of the present disclosure are described in detail below. It should be understood, however, that the present disclosure provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific examples described are merely illustrative of particular ways to make and use the present disclosure and do not limit the scope of the disclosure. Throughout this description, unless otherwise specified, the same or similar reference numbers or labels on different figures refer to the same or similar components or signals.

[0012]

[0020] The present disclosure will be described with reference to an example in a particular context: an audio speaker system constructed using a piezoelectric diaphragm.

[0013]

[0021] 1 illustrates, in one embodiment, the frequency response of a piezoelectric diaphragm in a conventional application of the piezoelectric diaphragm, where the piezoelectric diaphragm is used to generate sound (e.g., tone) for, for example, an alarm, buzzer, etc.

[0014]

[0022] In Figure 1, curve 11 shows the sound pressure level (SPL) of a piezoelectric diaphragm, and curve 13 shows the impedance of the piezoelectric diaphragm. As shown in Figure 1, the amplitude of the frequency response (e.g., curve 11) varies significantly within the audible frequency range. Multiple peaks and valleys are observed in the frequency response of Figure 1. The maximum fluctuation in the frequency response can be as large as 30 dB or more. Such an insufficient frequency response can cause serious distortion in audio signals (e.g., music, human voice, etc.) that contain multiple and / or continuous frequency components across the audio frequency range. Therefore, conventional speech systems built using piezoelectric diaphragms are not suitable for reproducing audio signals.

[0015]

[0023] 2A and 2B show a top view and a cross-sectional view, respectively, of a piezoelectric diaphragm 100A according to one embodiment, with Fig. 2B showing a cross-sectional view of the piezoelectric diaphragm 100A taken along section DD' of Fig. 2A.

[0016]

[0024] 2A and 2B, piezoelectric diaphragm 100A includes plate 101, first piezoelectric film 103, and second piezoelectric film 105. In some embodiments, plate 101 is a metal plate, such as a brass plate or a nickel alloy plate. In one embodiment, first piezoelectric film 103 and second piezoelectric film 105 are formed from the same piezoelectric material. In another embodiment, first piezoelectric film 103 and second piezoelectric film 105 are formed from different piezoelectric materials.

[0017]

[0025] The first piezoelectric film 103 and the second piezoelectric film 105 may be formed by depositing a layer of piezoelectric material on the plate 101 and then patterning the deposited piezoelectric material (e.g., etching using an etching mask having a mask pattern) to remove portions of the deposited piezoelectric material. After patterning, the remaining portions of the deposited piezoelectric material form the first piezoelectric film 103 and the second piezoelectric film 105. In other embodiments, the first piezoelectric film 103 and the second piezoelectric film 105 may each be preformed as a layer of dielectric material having a predetermined shape, and then the preformed first piezoelectric film 103 and the preformed second piezoelectric film are attached (e.g., glued) to the plate 101.

[0018]

[0026] In the example of FIG. 2A , the plate 101 has a circular shape. The first piezoelectric film 103 has a circular shape with a slit. The inner portion of the slit has a test-tube shape, and the outer portion of the slit has an enlarged, curved shape. In the illustrated example, the second piezoelectric film 105 is disposed within the slit of the first piezoelectric film 103 and may have a geometrically similar shape to the slit. For example, the second piezoelectric film 105 may have a test-tube shape at one end and an enlarged portion at the other end. As shown in FIG. 2A , the second piezoelectric film 105 is at least partially surrounded by the first piezoelectric film 103. Note that the second piezoelectric film 105 is spaced apart from the first piezoelectric film 103, and a gap 104 (e.g., an empty space) exists between the second piezoelectric film 105 and the first piezoelectric film 103. The shapes and relative positions of the first piezoelectric film 103 and the second piezoelectric film 105 allow for good coupling (e.g., kinematic coupling) between the first piezoelectric film 103 and the second piezoelectric film 105. For example, vibrations of the first piezoelectric film 103 cause the same or similar vibrations as the second piezoelectric film 105.

[0019]

[0027] 2A further shows three terminals of piezoelectric diaphragm 100A: terminal A attached to first piezoelectric film 103, terminal B attached to second piezoelectric film 105, and third terminal C attached to plate 101. In some embodiments, each of terminals A, B, and C may be formed by joining (e.g., soldering) a conductive wiring component (e.g., copper wire, metal connector, etc.) to a respective component (e.g., 103, 105, or 101) of piezoelectric diaphragm 100A.

[0020]

[0028] In the illustrated embodiment, during operation of the piezoelectric diaphragm 100A (e.g., as a speaker in an audio speaker system), terminal C is coupled to a reference voltage, such as electrical ground. Terminal A is configured to receive an (amplified) audio signal (e.g., a time-varying voltage carrying audio information). The first piezoelectric film 103 is configured to convert the audio signal (e.g., an electrical signal) into movement (e.g., vibration) of the first piezoelectric film 103 to generate audio sound. That is, the first piezoelectric film 103 is configured to function as a speaker. Due to the kinematic coupling between the first piezoelectric film 103 and the second piezoelectric film 105, movement (e.g., vibration) of the first piezoelectric film 103 is picked up (e.g., sensed) by the second piezoelectric film 105, causing movement (e.g., vibration) of the second piezoelectric film 105. The second piezoelectric film 105 generates an electrical signal in response to the movement. That is, the second piezoelectric film 105 functions as a microphone that converts the audio sound generated by the first piezoelectric film 103 into an electrical signal that is fed back to the negative input terminal of an amplifier in the audio speaker system. The amplifier generates an amplified audio signal that is sent to the first piezoelectric film 103, as will be described in more detail below.

[0021]

[0029] 3 to 5 show various embodiments of piezoelectric diaphragms. In particular, FIGS. 3, 4, and 5 show top views of piezoelectric diaphragm 100B, piezoelectric diaphragm 100C, and piezoelectric diaphragm 100D, respectively. The structures and functions of piezoelectric diaphragms 100B, 100C, and 100D are similar to those of piezoelectric diaphragm 100A, but the shapes of first piezoelectric film 103, second piezoelectric film 105, and / or plate 101 are different.

[0022]

[0030] Piezoelectric diaphragm 100B of Figure 3 is similar to piezoelectric diaphragm 100A, except that first piezoelectric film 103 of Figure 3 has a circular shape with a circular portion removed to form a recessed area. Second piezoelectric film 105 of piezoelectric diaphragm 100B has a (smaller) circular shape and is disposed within the recessed area.

[0023]

[0031] Piezoelectric diaphragm 100C in FIG. 4 is similar to piezoelectric diaphragm 100A, except that the slit in first piezoelectric film 103 in FIG. 4 has a rectangular shape, and second piezoelectric film 105 in piezoelectric diaphragm 100C also has a rectangular shape and is disposed within the rectangular slit in first piezoelectric film 103 in FIG. 4.

[0024]

[0032] Piezoelectric diaphragm 100D in Figure 5 is similar to piezoelectric diaphragm 100C, and has a rectangular slit in first piezoelectric film 103 and rectangular second piezoelectric film 105. However, plate 101 in Figure 5 has a rectangular shape, and first piezoelectric film 103 also has a rectangular shape.

[0025]

[0033] The various embodiments of piezoelectric diaphragms shown in Figures 2A, 2B, and 3-5 are illustrative and non-limiting. Other shapes and / or configurations of piezoelectric diaphragms are possible and are fully intended to be within the scope of this disclosure. Note that the piezoelectric diaphragms described herein (e.g., 100A, 100B, 100C, and 100D) belong to the self-driven piezoelectric diaphragm type, which has three terminals (e.g., A, B, and C). When used as a buzzer, they can be used to form an oscillator circuit for generating an internal frequency signal (e.g., a tone). Self-driven piezoelectric diaphragms differ from externally driven piezoelectric diaphragms, which have two terminals and require an external frequency signal (e.g., a tone) to generate sound (e.g., an alarm or buzzer). The piezoelectric diaphragms used to construct the discussion of audio speaker systems herein are self-driven piezoelectric diaphragms.

[0026]

[0034] FIG. 6 illustrates a symbol for a piezoelectric diaphragm 100 in one embodiment. Piezoelectric diaphragm 100 may represent any suitable self-actuated piezoelectric diaphragm, such as piezoelectric diaphragms 100A, 100B, 100C, and 100D. The symbol shown in FIG. 6 is used in subsequent figures to represent piezoelectric diaphragms used in audio speaker systems. As shown in FIG. 6, the symbol indicates a plate 101, a first piezoelectric film 103 (shown as a speaker icon), and a second piezoelectric film 105 (shown as a microphone icon). The dashed arrows in FIG. 6 indicate coupling (e.g., kinematic coupling) between the first piezoelectric film 103 and the second piezoelectric film 105. The symbol in FIG. 6 also indicates terminals A, B, and C of piezoelectric diaphragm 100.

[0027]

[0035] FIG. 7 illustrates an audio speaker system 200A in one embodiment. Audio speaker system 200A is suitable for reproducing audio signals, such as music or speech, and is configured using piezoelectric diaphragm 100. Piezoelectric diaphragm 100 may be any suitable piezoelectric diaphragm, such as piezoelectric diaphragm 100A, 100B, 100C, 100D, or a commercially available (e.g., off-the-shelf) self-actuated piezoelectric diaphragm. For simplicity, FIG. 7 does not show all features of audio speaker system 200A.

[0028]

[0036] 7, the audio speaker system 200A includes a piezoelectric diaphragm 100 and an amplifier 111. The amplifier 111 may be, for example, an audio amplifier such as an operational amplifier. In the example of FIG. 7, the amplifier 111 is connected to a power supply voltage V DD The amplifier 111 is coupled between a power supply having a voltage (e.g., +3V, +5V, etc.) and a reference voltage node 112, which is coupled, for example, to electrical ground. An output terminal 118 of the amplifier 111 is coupled to terminal A of the piezoelectric diaphragm 100 and provides an amplified audio signal to the first piezoelectric film 103 (which functions as a speaker). Terminal B of the piezoelectric diaphragm 100 outputs an electrical signal (e.g., a voltage signal) generated by the second piezoelectric film 105. Terminal C of the piezoelectric diaphragm 100 is coupled to a reference voltage node 106, which is coupled, for example, to electrical ground.

[0029]

[0037] Continuing with reference to FIG. 7, a reference voltage V is applied to a node 114 that is coupled to the positive input terminal 115 of amplifier 111. REF The reference voltage V REF has a fixed nominal value, for example, the power supply voltage V DD It may be half of that.

[0030]

[0038] An audio signal (e.g., a time-varying voltage signal carrying audio information) is applied to node 121, which is coupled to negative input terminal 113 of amplifier 111 via series-coupled capacitor C1 and resistor R3. In some embodiments, capacitor C1 functions as a high-pass filter to block (e.g., filter out) low frequency components (e.g., DC components) of the audio signal.

[0031]

[0039] 7, resistors R1 and R2 are coupled in series between terminal B of piezoelectric diaphragm 100 and a reference voltage node 117. Reference voltage node 117 is coupled to electrical ground in the illustrated embodiment. A node 116 between resistors R1 and R2 is also coupled to the negative input terminal 113 of amplifier 111.

[0032]

[0040] During operation of the audio speaker system 200A, an audio signal applied at node 121 is filtered by capacitor C1 (e.g., to remove low-frequency components such as DC components). The filtered audio signal is sent to and amplified by amplifier 111. The amplified audio signal at output terminal 118 of amplifier 111 drives (e.g., excites) first piezoelectric film 103, causing movement (e.g., vibration) of the first piezoelectric film 103 to generate audio sound (e.g., music or voice). The movement (e.g., vibration) of the first piezoelectric film 103, through kinematic coupling, results in the same or similar movement (e.g., vibration) of second piezoelectric film 105, which functions as a microphone and converts the audio sound into an electrical signal (e.g., a voltage signal). The electrical signal is fed back to negative input terminal 113 of amplifier 111. In the example of FIG. 7, a scaled version of the electrical signal at terminal B is generated by a voltage divider formed by resistors R1 and R2 and combined with (e.g., added together) the filtered audio signal to form a feedback voltage which is then applied to the negative input terminal 113 of amplifier 111.

[0033]

[0041] 8 shows another embodiment of an audio speaker system 200B. The audio speaker system 200B is similar to the audio speaker system 200A, except that an audio signal is applied to a node 131, which is connected to the positive input terminal 115 of the amplifier 111 through a capacitor C1. In addition, a reference voltage V REF is applied to node 124, which is coupled via resistor R3 to the positive input terminal 115 of amplifier 111. The operation of audio speaker system 200B is similar to that of audio speaker system 200A and will not be described in detail. In both audio speaker systems 200A and 200B, the electrical signal at terminal B is fed back to the negative input terminal 113 of the amplifier.

[0034]

[0042] FIG. 9 illustrates yet another embodiment of an audio speaker system 300. Audio speaker system 300 is similar to audio speaker system 200B (or 200A), but with less detail to illustrate a speaker system at a higher level of abstraction. For example, FIG. 9 illustrates that the electrical signal at terminal B of piezoelectric diaphragm 100 is fed back to the negative input terminal 113 of the amplifier, which is one of many features that distinguish it from conventional circuit configurations that use piezoelectric diaphragm 100 in applications such as alarms or buzzers. The amplifier 111 and piezoelectric diaphragm 100 in FIG. 9 represent a high-level abstraction of audio speaker systems 200A and 200B.

[0035]

[0043] Further, in FIG. 9, an audio signal is applied at node 201. The audio signal is then processed (e.g., amplified) by preamplifier 203 (e.g., an audio preamplifier). The output of preamplifier 203 is then processed by tone and volume control circuit 205, which may be, for example, a filter that adjusts the gain and / or phase of the audio signal at different frequencies in the audio frequency band. In some embodiments, one or both of preamplifier 203 and tone and volume control circuit 205 are omitted. In some embodiments, the audio signal at the output of tone and volume control circuit 205 is applied to node 121 in FIG. 7 or node 131 in FIG. 8.

[0036]

[0044] Modifications and variations of the present disclosure are possible and are fully intended to be within the scope of the present disclosure. For example, the examples in Figures 7, 8, and 9 use single-ended signals as a non-limiting example. Those skilled in the art will readily understand 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 different types of amplifiers, such as Class A, Class AB, Class D, Class G, and Class H amplifiers.

[0037]

[0045] 10 illustrates the frequency response of a piezoelectric diaphragm used in an audio speaker system, such as audio speaker system 200A, 200B, or 300, in one embodiment.

[0038]

[0046] In FIG. 10, curve 21 shows the sound pressure level (SPL) of the piezoelectric diaphragm, and curve 23 shows the impedance of the piezoelectric diaphragm. As shown in FIG. 10, the amplitude of the frequency response (e.g., curve 21) remains substantially flat within an audible frequency range (e.g., 1 KHz to 20 KHz). In some embodiments, within the audible frequency range, 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 amplitude of the frequency response in the audible frequency range. Such a substantially flat frequency response enables the piezoelectric diaphragm to be used to generate high-quality audio signals (e.g., music, human voice, etc.).

[0039]

[0047] 11 illustrates a flowchart of a method for reproducing an audio signal using a piezoelectric diaphragm, according to some embodiments. It should be understood that the exemplary method illustrated in FIG. 11 is merely an example of many possible exemplary methods. Those skilled in the art will recognize many variations, modifications, and alternatives. For example, various steps as illustrated in FIG. 11 can be added, removed, substituted, rearranged, or repeated.

[0040]

[0048] Referring to FIG. 11 , in block 1010, an audio signal is received at a positive input terminal of an amplifier or a negative input terminal of the amplifier. In block 1020, a reference voltage is provided to the positive input terminal of the amplifier. In block 1030, an output signal of the amplifier is transmitted to a first piezoelectric film of a piezoelectric diaphragm, the first piezoelectric film being configured to convert the output signal of the amplifier into movement of the first piezoelectric film. In block 1040, the first piezoelectric film is kinematically coupled to a second piezoelectric film of the piezoelectric diaphragm, the second piezoelectric film being configured to convert movement of the second piezoelectric film into an electrical signal. In block 1050, the electrical signal is fed back to the negative input terminal of the amplifier.

[0041]

[0049] Embodiments can achieve advantages as described below. For example, the audio speaker systems disclosed herein are formed using piezoelectric diaphragms. The circuitry of the disclosed audio speaker systems enables the audio speaker systems to achieve superior frequency response previously unattainable using piezoelectric diaphragms. Because piezoelectric diaphragms are much cheaper than piezoelectric speakers while having approximately the same form factor (e.g., size), the disclosed audio speaker systems (which use piezoelectric diaphragms) can be used to replace currently used, much more expensive speaker systems formed using piezoelectric speakers.

[0042]

[0050] Embodiments of the present disclosure are summarized here. Other embodiments can be seen throughout the specification and claims appended hereto.

[0043]

[0051] Example 1 According to one embodiment, an audio speaker system includes an amplifier, the amplifier configured to have a positive input terminal coupled to a first reference voltage node; and a piezoelectric diaphragm, the piezoelectric diaphragm including a metal plate; a first piezoelectric film attached to the metal plate, the first piezoelectric film configured to function as a speaker during operation of the audio speaker system; and a second piezoelectric film attached to the metal plate and spaced apart from the first piezoelectric film, the second piezoelectric film configured to function as a microphone during operation of the audio speaker system, the output terminal of the amplifier coupled to the first piezoelectric film and the negative input terminal of the amplifier coupled to the second piezoelectric film.

[0044]

[0052] [Example 2] The audio speaker system of Example 1, wherein during operation of the audio speaker system, the microphone formed by the second piezoelectric film is kinematically coupled to the speaker formed by the first piezoelectric film.

[0045]

[0053] [Example 3] The audio speaker system of Example 1, further including a first resistor and a second resistor coupled in series between the second piezoelectric film and a second reference voltage node, and the negative input terminal of the amplifier is coupled to the first node between the first resistor and the second resistor.

[0046]

[0054] [Example 4] An audio speaker system as described in Example 3, further including a capacitor and a third resistor coupled in series between the negative input terminal of the amplifier and a second node, the second node being configured to receive an audio signal.

[0047]

[0055] [Example 5] An audio speaker system as described in Example 4, wherein 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 source having a voltage higher than electrical ground.

[0048]

[0056] [Example 6] An audio speaker system as described in Example 3, further including: a capacitor coupled between the second node and the positive input terminal of the amplifier, where 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]

[0057] [Example 7] The audio speaker system of Example 6, wherein during operation of the audio speaker system, the voltage at the second reference voltage node is equal to electrical ground and the voltage at the first reference voltage node is greater than electrical ground.

[0050]

[0058] [Example 8] The audio speaker system according to Example 1, wherein the audio speaker system has a frequency response within a frequency band of 1 KHz to 20 KHz, and the amplitude variation of the frequency response within the frequency band is less than 3 dB.

[0051]

[0059] [Example 9] The audio speaker system of Example 1, further comprising an audio preamplifier coupled between the input terminal of the audio speaker system and the positive input terminal of the amplifier.

[0052]

[0060] [Example 10] The audio speaker system of Example 9, further comprising a tone and volume control circuit coupled between the audio preamplifier and the positive input terminal of the amplifier.

[0053]

[0061] [Example 11] According to one embodiment, an audio speaker system includes a piezoelectric diaphragm including a metal plate, a first piezoelectric film attached to the metal plate, and a second piezoelectric film attached to the metal plate, the second piezoelectric film being at least partially surrounded by and spaced apart from the first piezoelectric film; and an amplifier configured such that an output terminal of the amplifier is coupled to the first piezoelectric film, a negative input terminal of the amplifier is coupled to the second piezoelectric film, and a positive input terminal of the amplifier is coupled to a first reference voltage node.

[0054]

[0062] [Example 12] An audio speaker system as described in Example 11, wherein during operation of the audio speaker system, a first piezoelectric film is configured to convert a first electrical signal at the output terminal of the amplifier into movement of the first piezoelectric film, and a second piezoelectric film is configured to be kinematically coupled to the first piezoelectric film and to convert movement of the second piezoelectric film into a second electrical signal.

[0055]

[0063] [Example 13] An audio speaker system as described in Example 12, wherein the second piezoelectric film is coupled to a voltage divider including a first resistor and a second resistor coupled in series, and a first node between the first resistor and the second resistor is coupled to the negative input terminal of the amplifier.

[0056]

[0064] [Example 14] An audio speaker system as described in Example 13, further including 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.

[0057]

[0065] [Example 15] An audio speaker system as described in Example 13, further including: 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 a second node, the second node being configured to receive an audio signal.

[0058]

[0066] [Example 16] An audio speaker system as described in Example 11, wherein the piezoelectric diaphragm has a frequency response in a frequency band of 1 KHz to 20 KHz during operation of the audio speaker system, and the maximum variation in the amplitude of the frequency response is less than 3 dB in the frequency band.

[0059]

[0067] [Example 17] According to one embodiment, a method for reproducing an audio signal using a piezoelectric diaphragm includes the steps of receiving an audio signal at a positive input terminal of an amplifier or 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 piezoelectric film of the piezoelectric diaphragm, the first piezoelectric film being configured to convert the output signal of the amplifier into movement of the first piezoelectric film, kinematically coupling the first piezoelectric film to a second piezoelectric film of the piezoelectric diaphragm, the second piezoelectric film being configured to convert movement of the second piezoelectric film into an electrical signal, and feeding back the electrical signal to the negative input terminal of the amplifier.

[0060]

[0068] [Example 18] The method described in Example 17, wherein the step of feeding back the electrical signal includes the steps of generating a scaled version of the electrical signal using a voltage divider and sending the scaled version of the electrical signal to the negative input terminal of the amplifier.

[0061]

[0069] [Example 19] A method as described in Example 17, wherein the step of receiving an audio signal includes a step of receiving the 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]

[0070] [Example 20] A method as described in Example 17, wherein the step of receiving an audio signal includes a 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, and the step of supplying a reference voltage includes a step of supplying the reference voltage to a second node, a resistor is coupled between the second node and the positive input terminal of the amplifier.

[0063]

[0071] While the present disclosure has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the present disclosure, will be apparent to those skilled in the art upon reference to the description. It is therefore intended that the appended claims cover any such modifications or examples.

Claims

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

2. 2. The audio speaker system of claim 1, wherein the microphone formed by the second piezoelectric film is kinematically coupled to the speaker formed by the first piezoelectric film during operation of the audio speaker system.

3. 3. The audio speaker system of claim 1, further comprising a first resistor and a second resistor coupled in series between the second piezoelectric film and a second reference voltage node, the negative input terminal of the amplifier being coupled to a first node between the first resistor and the second resistor.

4. 4. The audio speaker system of claim 3, wherein 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 the electrical ground.

5. 5. The audio speaker system of claim 1, further comprising a capacitor and a third resistor coupled in series between the negative input terminal of the amplifier and a second node, the second node being configured to receive an audio signal.

6. a capacitor coupled between a second node and the positive input terminal of the amplifier, the second node 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; 5. An audio speaker system according to claim 1, further comprising:

7. 7. The audio speaker system of claim 6, wherein during operation of the audio speaker system, the voltage at the second reference voltage node is equal to electrical ground and the voltage at the first reference voltage node is greater than electrical ground.

8. 8. An audio speaker system according to claim 1, wherein the audio speaker system has a frequency response within a frequency band of 1 KHz to 20 KHz, the amplitude variation of the frequency response within the frequency band being less than 3 dB.

9. 3. The audio speaker system of claim 1, further comprising an audio preamplifier coupled between an input terminal of the audio speaker system and the positive input terminal of the amplifier.

10. 10. The audio speaker system of claim 9, further comprising a tone and volume control circuit coupled between said audio preamplifier and said positive input terminal of said amplifier.

11. 1. An audio speaker system, comprising: A piezoelectric diaphragm, A metal plate and a first piezoelectric film attached to the metal plate; a piezoelectric diaphragm including: a second piezoelectric film attached to the metal plate, the second piezoelectric film being at least partially surrounded by the first piezoelectric film and spaced apart from the first piezoelectric film; an amplifier configured such that an output terminal of the amplifier is coupled to the first piezoelectric film, a negative input terminal of the amplifier is coupled to the second piezoelectric film, and a positive input terminal of the amplifier is coupled to a first reference voltage node.

12. 12. The audio speaker system of claim 11, wherein during operation of the audio speaker system, the first piezoelectric film is configured to convert a first electrical signal at the output terminal of the amplifier into movement of the first piezoelectric film, and the second piezoelectric film is configured to be kinematically coupled to the first piezoelectric film and to convert movement of the second piezoelectric film into a second electrical signal.

13. 13. The audio speaker system of claim 11 or 12, wherein the second piezoelectric film is coupled to a voltage divider including a first resistor and a second resistor coupled in series, and a first node between the first resistor and the second resistor is coupled to the negative input terminal of the amplifier.

14. 14. The audio speaker system of claim 13, further comprising a capacitor and a third resistor coupled in series between the first node and a second node, the second node configured to receive an audio signal.

15. a third resistor coupled between the positive input terminal of the amplifier and the first reference voltage node; a capacitor coupled between the positive input terminal of the amplifier and a second node, the second node configured to receive an audio signal; and 14. An audio speaker system according to any one of claims 11 to 13, further comprising:

16. 16. An audio speaker system according to any one of claims 11 to 15, wherein the piezoelectric diaphragm has a frequency response in a frequency range of 1 KHz to 20 KHz during operation of the audio speaker system, and wherein a maximum variation in the amplitude of the frequency response is less than 3 dB in the frequency range.

17. 13. An audio speaker system according to claim 11 or 12, further comprising an audio preamplifier coupled between an input terminal of the audio speaker system and the positive input terminal of the amplifier.

18. 1. A method for reproducing an audio signal using a piezoelectric diaphragm, comprising: receiving an audio signal at a positive input terminal of an amplifier or a negative input terminal of said amplifier; providing a reference voltage to the positive input terminal of the amplifier; transmitting an output signal of the amplifier to a first piezoelectric film of the piezoelectric diaphragm, the first piezoelectric film being configured to convert the output signal of the amplifier into movement of the first piezoelectric film; kinematically coupling the first piezoelectric film to a second piezoelectric film of the piezoelectric diaphragm, the second piezoelectric film being configured to convert movement of the second piezoelectric film into an electrical signal; and feeding back the electrical signal to the negative input terminal of the amplifier.

19. The step of feeding back the electrical signal includes: generating a scaled version of the electrical signal using a voltage divider; sending the scaled version of the electrical signal to the negative input terminal of the amplifier.

20. 20. The method of claim 18 or 19, wherein receiving the audio signal comprises receiving the audio signal at a first node, a capacitor and a resistor coupled in series between the first node and the negative input terminal of the amplifier.

21. 20. The method of claim 18 or 19, wherein receiving the audio signal comprises receiving the audio signal at a first node, a capacitor coupled between the first node and the positive input terminal of the amplifier, and providing the reference voltage comprises providing the reference voltage to a second node, a resistor coupled between the second node and the positive input terminal of the amplifier.

22. receiving the audio signal, receiving the audio signal with a preamplifier; and processing the audio signal through the preamplifier to generate a first output of the preamplifier.

23. 23. The method of claim 22, further comprising providing the first output to the positive input terminal of the amplifier.

24. processing the first output of the preamplifier with a tone and volume control circuit to generate a second output of the tone and volume control circuit; providing the second output to the positive input terminal of the amplifier; 23. The method of claim 22, further comprising:

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