WO2014169861A1 - 一种压电扬声器驱动装置 - Google Patents

一种压电扬声器驱动装置 Download PDF

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Publication number
WO2014169861A1
WO2014169861A1 PCT/CN2014/076152 CN2014076152W WO2014169861A1 WO 2014169861 A1 WO2014169861 A1 WO 2014169861A1 CN 2014076152 W CN2014076152 W CN 2014076152W WO 2014169861 A1 WO2014169861 A1 WO 2014169861A1
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Prior art keywords
piezoelectric
piezoelectric speaker
signal
driving
driving device
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PCT/CN2014/076152
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English (en)
French (fr)
Inventor
秦世军
袁世民
卞学恒
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中兴通讯股份有限公司
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Application filed by 中兴通讯股份有限公司 filed Critical 中兴通讯股份有限公司
Priority to EP14784927.7A priority Critical patent/EP3048811A4/en
Priority to US15/030,069 priority patent/US20160277833A1/en
Publication of WO2014169861A1 publication Critical patent/WO2014169861A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/04—Circuits for transducers, loudspeakers or microphones for correcting frequency response
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H04R17/005—Piezoelectric transducers; Electrostrictive transducers using a piezoelectric polymer
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/007—Protection circuits for transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2430/00—Signal processing covered by H04R, not provided for in its groups
    • H04R2430/01—Aspects of volume control, not necessarily automatic, in sound systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2430/00—Signal processing covered by H04R, not provided for in its groups
    • H04R2430/03—Synergistic effects of band splitting and sub-band processing

Definitions

  • the present invention relates to speaker technology, and more particularly to a piezoelectric speaker driving device for an electronic product including a speaker such as a mobile phone or a tablet computer. Background technique
  • the piezoelectric crystal or the piezoelectric ceramic When a piezoelectric crystal or a piezoelectric ceramic is subjected to an external electric field, the piezoelectric crystal or the piezoelectric ceramic generates a mechanical deformation linearly related to the electric field strength. This phenomenon is called an inverse piezoelectric effect. Therefore, when an electrical signal is applied to the piezoelectric ceramic, the piezoelectric ceramic itself undergoes corresponding mechanical vibration, and further pushes the nearby air to vibrate, thereby emitting sound.
  • FIG. 1 is a schematic diagram of the impedance of a related piezoelectric ceramic as a function of frequency, where the abscissa is the frequency (in Hz) and the ordinate is the impedance (in ohm), as shown by curve 1 in Figure 1, at high frequencies.
  • the impedance is extremely low. Because of this, the piezoelectric speaker drive circuit needs to be able to provide a higher current output, so a specially designed drive circuit is required to satisfy the stable drive.
  • the piezoelectric speaker since the piezoelectric speaker has a certain deformation amplitude at a certain voltage, the sound pressure frequency response generally increases as the frequency increases, and this phenomenon requires a frequency response in the high-fidelity playback requirement of the sound. Keeping it as flat as possible is not consistent.
  • most piezoelectric speaker reproduction systems behave as a audible sound, which is caused by the high frequency response being much higher than the low frequency response in the speaker.
  • the present invention provides a piezoelectric speaker driving device capable of simply improving the sound quality of a high-frequency portion of a piezoelectric speaker without adjusting the structure and assembly of the piezoelectric speaker, and improving the pressure due to the pressure.
  • the high-band impedance of the electric ceramic component leads to an increase in driving power consumption and a self-excited circuit.
  • the invention discloses a piezoelectric speaker driving device, comprising a driving amplification unit for amplifying a signal source, a piezoelectric speaker, and further comprising: a signal tuning unit,
  • the method is configured to: filter the signal amplified by the driving amplification unit to filter out high frequency noise; adjust impedance characteristics of the piezoelectric ceramic in the piezoelectric speaker; output the adjusted driving signal to the piezoelectric speaker to drive Piezo speaker.
  • the signal tuning unit includes a low pass filter circuit and an adjusted impedance.
  • the driving amplification unit includes a power amplifier, and is set as: a power supply for supplying power to the power amplifier;
  • the low-pass filter is configured to: consist of an inductor connected in series in the output loop of the power amplifier, and a capacitor connected in parallel in the output loop of the power amplifier, filtering out high-frequency noise in the amplified signal from the power amplifier, and simultaneously pressing The high frequency portion of the sound pressure response curve of the electric speaker is attenuated;
  • the adjustment impedance is set as: the resistance of the series connection in the output loop of the power amplifier, adjusting the piezoelectricity
  • the impedance characteristics of piezoelectric ceramics in the sounder The value of the inductance, or capacitance, or resistance is determined according to the frequency point corresponding to the resonant peak and valley of the high frequency portion of the piezoelectric speaker.
  • the inductor is a patch magnetic low frequency inductor between 10 uH and 1 OmH;
  • the capacitor is a chip ceramic capacitor between lnF and luF;
  • the resistor is a patch metal film resistor between 10 and 100 ohms.
  • the inductance is 130 uH; the capacitance is 0.47 uF; the resistance is 22 ohms.
  • the piezoelectric speaker driving device includes a driving amplifying unit, a signal tuning unit, and a piezoelectric speaker; wherein, the driving amplifying unit is configured to amplify the signal source, and output the amplified signal to the signal tuning unit; a tuning unit for filtering the amplified signal to filter out high frequency noise; adjusting the impedance characteristics of the piezoelectric ceramic, increasing the load impedance of the driving circuit in the high frequency portion, and reducing the driving current in the high frequency band; The drive signal is output to the piezoelectric speaker to drive the piezoelectric speaker.
  • the signal tuning unit may include a low pass filter circuit and a regulated impedance.
  • the piezoelectric speaker driving device of the embodiment of the invention the sound quality of the high-frequency part of the piezoelectric speaker is improved and the high-band impedance of the piezoelectric ceramic component is improved without adjusting the structure and assembly of the piezoelectric speaker. Low drive power consumption rise and circuit self-excitation problems.
  • Figure 1 is a schematic diagram showing the impedance of a related piezoelectric ceramic as a function of frequency
  • FIG. 2 is a schematic structural diagram of a piezoelectric speaker driving device according to an embodiment of the present invention.
  • FIG. 3 is a specific circuit diagram of a piezoelectric speaker driving device according to an embodiment of the present invention.
  • Figure 4 is an equivalent circuit diagram of the relevant piezoelectric ceramic working near the resonance point
  • FIG. 5 is a schematic diagram of frequency response and THD under the relevant piezoelectric speaker driving circuit
  • FIG. 6 is a schematic diagram of frequency response and THD of the piezoelectric speaker driving circuit according to an embodiment of the present invention.
  • FIG. 2 is a schematic structural diagram of a piezoelectric speaker driving device of the present invention, as shown in FIG. a driving amplification unit, a signal tuning unit, and a piezoelectric speaker;
  • the driving amplifying unit is configured to amplify the signal source, and output the amplified signal to the signal tuning unit; and the specific implementation data of the driving amplifying unit is prior art.
  • a signal tuning unit for filtering the amplified signal to filter out high frequency noise; adjusting the impedance characteristics of the piezoelectric ceramic, increasing the load impedance of the driving circuit in the high frequency portion, and reducing the driving current in the high frequency band;
  • the drive signal is output to the piezoelectric speaker to drive the piezoelectric speaker.
  • the signal tuning unit may include a low pass filter circuit and an adjusted impedance.
  • the piezoelectric speaker driving device of the embodiment of the invention the sound quality of the high-frequency part of the piezoelectric speaker is improved and the high-band impedance of the piezoelectric ceramic component is improved without adjusting the structure and assembly of the piezoelectric speaker. Low drive power consumption rise and circuit self-excitation problems.
  • the driving amplifying unit includes a power amplifier 2 and a power source 3;
  • the signal tuning unit includes an inductor 4, a capacitor 5, and a resistor. 6;
  • a piezoelectric speaker 7 and a signal source 1 to be amplified are included. specifically,
  • Signal source 1 that is, the original electrical signal that is not amplified.
  • source 1 can be voice (such as in the case of a mobile phone call) or music (such as playing MP3 music on a tablet).
  • the voltage of signal source 1 is generally around lVpp.
  • Amplifier 2 used to amplify the original electrical signal from signal source 1 to 10Vpp ⁇ 20Vpp, and output it to the signal tuning unit.
  • the commonly used power amplifier 2 can be a power amplifier of the TPA2100P1 signal from Texas Instruments.
  • Power supply 3 is used to supply power to the amplifier.
  • the power supply 3 is typically a 3.7V lithium-ion battery.
  • the inductor 4 connected in series in the output loop of the power amplifier 2 and the capacitor 5 connected in parallel in the output loop of the power amplifier 2 constitute a low-pass filter for filtering high-frequency noise in the amplified signal from the power amplifier 2, and at the same time
  • the high-frequency portion of the piezoelectric speaker's sound pressure frequency response curve is attenuated to make the sound softer.
  • the resistor 6 connected in series in the output loop of the power amplifier 2 is used to adjust the impedance characteristic of the piezoelectric ceramic, and the load impedance of the driving circuit in the high frequency portion is improved by the series resistor 6, thereby effectively reducing the driving current in the high frequency band, so that the system The power consumption is reduced and the stability of the circuit is improved.
  • the inductor 4 can choose the chip magnetic low frequency inductor between lOuH ⁇ : lOmH; the capacitor 5 can select the chip ceramic capacitor between InF ⁇ : luF; the resistor 6 can choose the patch metal film between 10 ⁇ 1 ohms resistance.
  • the piezoelectric speaker 7 is driven by a signal output from the signal tuning unit and oscillates the nearby air through the piezoelectric ceramic vibration in the piezoelectric speaker.
  • FIG. 3 is merely an embodiment and is not intended to limit the scope of protection of the present invention.
  • the embodiment of the present invention emphasizes that the signal tuning is added to the output circuit of the existing driving circuit.
  • the unit on the one hand, filters the amplified signal to filter out high frequency noise; on the other hand, adjusts the impedance characteristics of the piezoelectric ceramic, improves the load impedance of the driving circuit in the high frequency part, and reduces the driving current in the high frequency band;
  • the rear drive signal is output to the piezoelectric speaker to drive the piezoelectric speaker.
  • the piezoelectric speaker driving device provided by the embodiment of the invention corrects and reduces the fluctuation of the high-frequency portion of the piezoelectric speaker by the low-pass filter unit in the signal tuning unit, improves the sound quality; and adjusts the impedance through the signal tuning unit.
  • the load impedance of the high frequency part is increased, power consumption is reduced, and circuit stability is increased.
  • the piezoelectric speaker driving device of the embodiment of the invention solves the problem of poor sound quality in the application of the piezoelectric speaker in the portable electronic device, and fully utilizes the advantages of thinning of the piezoelectric speaker and low power consumption.
  • the parameters of the inductance 4, the capacitance 5, and the resistance 6 are determined according to the frequency points corresponding to the resonance peaks and valleys of the high-frequency portion of the piezoelectric speaker. details as follows:
  • the core part of the piezoelectric speaker is a piezoelectric ceramic.
  • a piezoelectric ceramic When operating near the resonance point, it is equivalent to a static capacitor CO on the circuit and a set of capacitor C1, inductor L1, and resistor R1 in parallel, as shown in Figure 4, Figure 4 An equivalent circuit diagram for the relevant piezoelectric ceramics operating near the resonance point.
  • the resonant frequency of the low-pass filter circuit composed of the static capacitor CO and the capacitor 5 and the inductor 4 can be set according to the intermediate frequency point between the high-frequency peak and the valley value in the piezoelectric speaker (ie, the impedance resonance phase zero-crossing point), and can pass The value of capacitor 5 or inductor 4 is trimmed for optimization.
  • the resistor 6 can adjust the quality factor of the corresponding matching circuit, that is, the Q value, and should be adjusted in combination with the Q value of the frequency response valley of the high frequency transition region in the piezoelectric speaker, thereby improving and improving the output frequency response.
  • the valley of the curve is, the Q value
  • Piezoelectric speaker type PS2327 uses a piezoelectric ceramic static capacitor CO of 1.4 ⁇ 0.2uF; the drive circuit has a capacitance of 5 selectable parameters of 0.47uF; inductor 4 has a choice of 130uH and resistor 6 has a choice of 22ohm.
  • the intermediate frequency between the peak and the valley of the high frequency is about 10 kHz, which falls on the high frequency peak (see Figure 5, about 13 kHz) and the intermediate frequency valley, which is the frequency point corresponding to the piezoelectric speaker frequency response valley (see Figure 6, about 7 kHz). ) Middle.
  • FIG 5 is a schematic diagram of the frequency response and total harmonic distortion (THD) of the existing piezoelectric speaker drive circuit.
  • the abscissa indicates the frequency (in ⁇ ), and the left side is vertical.
  • the coordinates represent the sound pressure level (SPL) (in dB), the right ordinate represents THD (unit is %); curve 1 is the frequency response curve, curve 2 is the THD curve, and the sound pressure fluctuation value of the high frequency part is about 25dB.
  • SPL sound pressure level
  • THD unit is %
  • curve 1 is the frequency response curve
  • curve 2 is the THD curve
  • the sound pressure fluctuation value of the high frequency part is about 25dB.
  • Peak P1 is about 105 dB
  • valley P2 is about 80 dB).
  • FIG. 6 is a schematic diagram of frequency response and THD of a piezoelectric speaker driving circuit according to an embodiment of the present invention.
  • the abscissa represents frequency (in units of ⁇ ), and the left ordinate represents SPL (in dB), right side.
  • the ordinate represents THD (unit is %); curve 3 is the frequency response curve, and curve 4 is the THD curve.
  • the piezoelectric speaker driving device of the embodiment of the invention simply improves the sound quality of the high-frequency portion of the piezoelectric speaker without adjusting the structure and assembly of the piezoelectric speaker, and improves the low-frequency impedance of the piezoelectric ceramic component.
  • the resulting drive power consumption increases and the circuit is self-excited.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Amplifiers (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)

Abstract

一种压电扬声器驱动装置，包括驱动放大单元、信号调谐单元，以及压电扬声器；其中，驱动放大单元，设置为：放大信号源，并将放大后的信号输出给信号调谐单元；信号调谐单元，设置为：对放大后的信号进行滤波，滤除高频噪声；调整压电陶瓷的阻抗特性，提高驱动电路在高频部分的负载阻抗，降低高频段的驱动电流；并将调整后的驱动信号输出给压电扬声器，以驱动压电扬声器。其中，信号调谐单元可以包括低通滤波电路和调整阻抗。通过本发明实施例压电扬声器驱动装置，在不调整压电扬声器结构和装配的情况下，简单地实现了改善压电扬声器高频部分重放音质，并改善了因压电陶瓷元件高频段阻抗低导致的驱动功耗升高以及电路自激问题。

Description

一种压电扬声器驱动装置
技术领域
本发明涉及扬声器技术， 尤指一种包含扬声器的电子产品如手机、 平板 电脑等中压电扬声器驱动装置。 背景技术
当压电晶体或压电陶瓷受到外电场的作用时， 压电晶体或压电陶瓷会产 生与电场强度成线性关系的机械形变， 这个现象称为逆压电效应。 因此， 当 在压电陶瓷上施加电信号时， 压电陶瓷自身会发生相应的机械振动， 并进一 步推动附近的空气振动， 从而发出声音。
与传统的动圈扬声器相比， 压电扬声器具有体积小、 轻薄、 抗冲击、 低 电磁辐射、 低功耗等优点。 但是， 由于压电扬声器的核心压电陶瓷为电容性 负载， 其阻抗频率特性接近电容。 图 1为相关压电陶瓷的阻抗随频率变化的 曲线示意图，其中横坐标为频率（单位为 Hz ) ,纵坐标为阻抗（单位为 ohm ) , 如图 1中的曲线 1所示， 在高频时阻抗极低。 正因为这样， 压电扬声器驱动 电路需要能够提供较高的电流输出， 因此， 需要特殊设计的驱动电路才能满 足稳定驱动。
在申请号为 "200880125607.5" , 发明名称为 "一种低功耗的压电放大 器及方法" 的申请中， 也指出了在高频部分电流增大的问题， 并提出了使用 开关和比较器来控制电路电流流向的方案。但是，这样的方法在实际应用中， 不仅电路和控制设计软件复杂， 而且也容易因为元件的参数失配带来电路的 自激振荡， 而导致压电元件发出高频嘯叫声。
在申请号为 "200810110462.3" , 发明名称为 "功率放大电路" 的申请 中， 提到了一种专门针对压电驱动的功率放大电路， 其中通过设置 2组不同 的功放电压 （其中一组高压通过电荷泵产生） ， 可以有效的改善功放的输出 效率。 但是， 该电路没有考虑压电扬声器中， 由于高频阻抗降低带来的电流 增加与输入信号增大带来的电流增加的差异， 而只是釆用一致的降低电压的 方法来防止电路输出电流过大的问题。 这样， 会带来因驱动电路产生的信号 失真， 并极大的损害了重放音质。
之外， 由于压电扬声器在一定的电压下变形幅度一定， 因此， 随频率升 高， 其声压频率响应一般也会升高， 这种现象与声音的高保真重放要求中的 频率响应需要保持尽可能平坦是不符的。 当前， 大多数压电扬声器的重放系 统表现为听感声音发尖， 就是由于高频部分响应远高于扬声器中低频响应而 造成的。
在申请号为 "201020149309.4" , 发明名称为 "一种带有配重结构及阻 尼结构的矩阵式压电平板扬声器" 的申请中， 提到了通过在压电扬声器结构 中， 增加配重和阻尼结构， 以相应改善压电扬声器中高频响应的不平坦性。 但是， 该方法会增加产品装配上的难度， 同时也增加了产品总厚度。
发明内容
为了解决上述技术问题， 本发明提供一种压电扬声器驱动装置， 能够在 不调整压电扬声器结构和装配的情况下， 简单地实现改善压电扬声器高频部 分重放音质， 并能够改善因压电陶瓷元件高频段阻抗低导致的驱动功耗升高 以及电路自激问题。 本发明公开了一种压电扬声器驱动装置， 包括用于放大信号源的驱动放 大单元、 压电扬声器， 还包括： 信号调谐单元，
设置为：对经所述驱动放大单元放大后的信号进行滤波，滤除高频噪声； 调整压电扬声器中的压电陶瓷的阻抗特性； 将调整后的驱动信号输出给压电 扬声器， 以驱动压电扬声器。 所述信号调谐单元包括低通滤波电路和调整阻抗。
所述驱动放大单元包括功放， 设置为： 给功放供电的电源；
所述低通滤波器设置为： 由串联在功放的输出回路中的电感， 和并联在 功放的输出回路中的电容构成，滤除来自功放的放大后的信号中的高频噪声， 同时将压电扬声器的声压频率响应曲线中高频部分进行衰减；
所述调整阻抗设置为： 为串联在功放的输出回路中的电阻， 调整压电扬 声器中的压电陶瓷的阻抗特性。 所述电感， 或电容， 或电阻的值， 根据压电扬声器中高频部分的谐振峰 谷对应的频点来确定。
所述电感为 10uH~ 1 OmH间的贴片磁性低频电感；
所述电容为 lnF~luF间的贴片陶瓷电容；
所述电阻为 10〜： lOOohm间的贴片金属膜电阻。
所述电感为 130uH; 所述电容为 0.47uF; 所述电阻为 22ohm。
本申请技术方案提供的压电扬声器驱动装置包括驱动放大单元、 信号调 谐单元， 以及压电扬声器； 其中， 驱动放大单元， 用于放大信号源， 并将放 大后的信号输出给信号调谐单元； 信号调谐单元， 用于对放大后的信号进行 滤波， 滤除高频噪声； 调整压电陶瓷的阻抗特性， 提高驱动电路在高频部分 的负载阻抗， 降低高频段的驱动电流； 并将调整后的驱动信号输出给压电扬 声器， 以驱动压电扬声器。 其中， 信号调谐单元可以包括低通滤波电路和调 整阻抗。 通过本发明实施例压电扬声器驱动装置， 在不调整压电扬声器结构 和装配的情况下， 简单地实现了改善压电扬声器高频部分重放音质， 并改善 了因压电陶瓷元件高频段阻抗低导致的驱动功耗升高以及电路自激问题。
附图概述
图 1为相关压电陶瓷的阻抗随频率变化的曲线示意图；
图 2为本发明实施例压电扬声器驱动装置的组成结构示意图；
图 3为本发明实施例的压电扬声器驱动装置的具体电路图；
图 4为相关压电陶瓷在共振点附近工作时的等效电路图；
图 5为相关压电扬声器驱动电路下的频率响应和 THD示意图； 图 6为本发明实施例压电扬声器驱动电路下的频率响应和 THD示意图。
本发明的较佳实施方式
图 2为本发明压电扬声器驱动装置的组成结构示意图， 如图 2所示， 包 括驱动放大单元、 信号调谐单元， 以及压电扬声器； 其中，
驱动放大单元， 用于放大信号源， 并将放大后的信号输出给信号调谐单 元； 驱动放大单元的具体实现数据现有技术。
信号调谐单元， 用于对放大后的信号进行滤波， 滤除高频噪声； 调整压 电陶瓷的阻抗特性， 提高驱动电路在高频部分的负载阻抗， 降低高频段的驱 动电流； 并将调整后的驱动信号输出给压电扬声器， 以驱动压电扬声器。
其中， 信号调谐单元可以包括低通滤波电路和调整阻抗。
通过本发明实施例压电扬声器驱动装置， 在不调整压电扬声器结构和装 配的情况下， 简单地实现了改善压电扬声器高频部分重放音质， 并改善了因 压电陶瓷元件高频段阻抗低导致的驱动功耗升高以及电路自激问题。
具体实施例参见图 3 , 图 3为本发明实施例压电扬声器驱动装置的具体 电路图， 如图 3所示， 驱动放大单元包括功放 2, 电源 3; 信号调谐单元包括 电感 4、 电容 5、 电阻 6; 此外还包括压电扬声器 7, 及待放大的信号源 1。 具体地，
信号源 1 , 即未经放大的原始电信号， 根据不同的应用场合， 信号源 1 可以是语音（如在手机通话的情况下） ， 或者是音乐 （如在平板电脑上播放 MP3乐曲） 。 信号源 1的电压一般在 lVpp左右。
功放 2, 用于将来自信号源 1的原始电信号放大到 10Vpp~20Vpp, 输出 给信号调谐单元。 比如常用的功放 2 可以是美国德州仪器公司的信号为 TPA2100P1的功放。
电源 3 , 用于给功放提供电源。 比如， 在手机中， 电源 3通常为 3.7V锂 离子电池。
串联在功放 2的输出回路中的电感 4和并联在功放 2的输出回路中的电 容 5, 构成低通滤波器， 用于滤除来自功放 2的放大后的信号中的高频噪声， 同时将压电扬声器的声压频率响应曲线中高频部分进行衰减， 让声音变得更 柔和。
串联在功放 2的输出回路中的电阻 6, 用于调整压电陶瓷的阻抗特性， 通过串联电阻 6, 使驱动电路在高频部分的负载阻抗提高， 有效降低了高频 段的驱动电流， 使得系统功耗降低， 同时电路的稳定性得到了改善。 其中， 电感 4 , 可以选择 lOuH〜： lOmH间的贴片磁性低频电感； 电容 5 , 可以选择 InF〜： luF间的贴片陶瓷电容； 电阻 6 , 可以选择 10~1 OOohm间的贴 片金属膜电阻。
压电扬声器 7 , 用于被信号调谐单元输出的信号驱动， 并通过压电扬声 器中的压电陶瓷振动带动附近空气发声。
需要说明的是， 图 3仅仅是一个实施例， 并不用于限定本发明的保护范 围。本领域技术人员根据本发明图 2所示的压电扬声器驱动装置的组成结构， 是可以得出不同的具体实现电路的， 本发明实施例强调的是在现有驱动电路 的输出回路增加信号调谐单元， 一方面对放大后的信号进行滤波， 滤除高频 噪声； 另一方面调整压电陶瓷的阻抗特性， 提高驱动电路在高频部分的负载 阻抗， 降低高频段的驱动电流； 并将调整后的驱动信号输出给压电扬声器， 以驱动压电扬声器。
通过本发明实施例提供的压电扬声器驱动装置， 由信号调谐单元中低通 滤波器单元修正并减小了压电扬声器高频部分的起伏， 改善了音质； 并且通 过信号调谐单元中的调整阻抗提高了高频部分的负载阻抗， 降低了功耗， 增 加了电路稳定性。 本发明实施例压电扬声器驱动装置解决了压电扬声器在便 携电子设备中应用中音质不佳的问题， 充分发挥了压电扬声器的薄形化， 低 功耗等优点。
为了使得本发明实施例压电扬声器驱动装置的驱动效果更优， 电感 4、 电容 5、 电阻 6的参数根据压电扬声器中高频部分的谐振峰谷对应的频点来 确定。 具体如下：
压电扬声器的核心部分为压电陶瓷， 其在共振点附近工作时在电路上等 效为一个静态电容 CO与一组电容 C1 , 电感 L1 , 电阻 R1的并联， 如图 4所 示， 图 4为相关压电陶瓷在共振点附近工作时的等效电路图。
静态电容 CO与电容 5 , 电感 4构成的低通滤波器电路的谐振频率，可以 根据压电扬声器中高频间峰值与谷值的中间频点 (即阻抗谐振相位过零点） 设定， 并可通过微调电容 5或电感 4的值以进行优化。
电阻 6可以调整相应匹配电路的品质因数即 Q值，调整时应结合压电扬 声器中高频过渡区域的频率响应低谷的 Q值，从而提升并改善输出频率响应 曲线的谷值。
下面结合实际应用中的实施例， 对本发明的具体实现及效果进行详细
以精拓丽音科技（北京）有限公司的型号为 PS2327的压电扬声器为例， 其驱动放大单元中的功放使用的是美国德州仪器 TPA2100P1 压电专用驱动 电路。 型号为 PS2327 的压电扬声器使用的压电陶瓷静态电容 CO 为 1.4士 0.2uF; 驱动电路中电容 5选择参数为 0.47uF; 电感 4选择为 130uH, 电阻 6 选择 22ohm。压电扬声器中高频间峰值与谷值的中间频点约为 10kHz落在高 频峰（参见图 5 , 约 13kHz )和中频谷即压电扬声器频响谷值对应的频点（参 见图 6, 约 7kHz ) 中间。
对于同一压电扬声器样品， 图 5为现有压电扬声器驱动电路下的频率响 应和总谐波失真 （THD ) 示意图， 如图 5 所示， 横坐标表示频率 （单位为 Ηζ ) , 左侧纵坐标表示声压级（ SPL ) (单位为 dB ) , 右侧纵坐标表示 THD (单位为％ )； 曲线 1为频率响应曲线， 曲线 2为 THD曲线， 高频部分的声 压波动值约在 25dB (峰值 P1约为 105dB, 谷值 P2约为 80dB )左右。
图 6为本发明实施例压电扬声器驱动电路下的频率响应和 THD示意图， 如图 6所示， 横坐标表示频率（单位为 Ηζ ) , 左侧纵坐标表示 SPL (单位为 dB ) , 右侧纵坐标表示 THD (单位为％) ； 曲线 3为频率响应曲线， 曲线 4 为 THD 曲线， 可以明显看到， 在本发明实施例压电扬声器驱动电路下， 波 动降低到 10dB左右（峰值 P3约为 88dB, 谷值 P4约为 lOOdB ) , 相应的衡 量音质的失真指标也有大幅降低。
以上所述， 仅为本发明的较佳实例而已， 并非用于限定本发明的保护范 围。 凡在本发明的精神和原则之内， 所做的任何修改、 等同替换、 改进等， 均应包含在本发明的保护范围之内。
工业实用 4生
本发明实施例压电扬声器驱动装置， 在不调整压电扬声器结构和装配的 情况下， 简单地实现了改善压电扬声器高频部分重放音质， 并改善了因压电 陶瓷元件高频段阻抗低导致的驱动功耗升高以及电路自激问题。

Claims

权 利 要 求 书
1、一种压电扬声器驱动装置， 包括用于放大信号源的驱动放大单元、压 电扬声器， 其特征在于， 还包括： 信号调谐单元，
所述信号调谐单元设置为： 对经所述驱动放大单元放大后的信号进行滤 波， 滤除高频噪声； 调整压电扬声器中的压电陶瓷的阻抗特性； 将调整后的 驱动信号输出给压电扬声器， 以驱动压电扬声器。
2、根据权利要求 1所述的压电扬声器驱动装置， 其中， 所述信号调谐单 元包括氏通滤波电路和调整阻抗。
3、根据权利要求 2所述的压电扬声器驱动装置， 其中， 所述驱动放大单 元包括功放， 设置为： 给功放供电的电源；
所述低通滤波器设置为： 由串联在功放的输出回路中的电感， 和并联在 功放的输出回路中的电容构成，滤除来自功放的放大后的信号中的高频噪声， 同时将压电扬声器的声压频率响应曲线中高频部分进行衰减；
所述调整阻抗设置为： 为串联在功放的输出回路中的电阻， 调整压电扬 声器中的压电陶瓷的阻抗特性。
4、 根据权利要求 3所述的压电扬声器驱动电路， 其中， 所述电感， 或电 容，或电阻的值，根据压电扬声器中高频部分的谐振峰谷对应的频点来确定。
5、 根据权利要求 3所述的压电扬声器驱动装置， 其中，
所述电感为 10uH~ 1 OmH间的贴片磁性低频电感；
所述电容为 lnF~luF间的贴片陶瓷电容；
所述电阻为 10〜： lOOohm间的贴片金属膜电阻。
6、 根据权利要求 3 所述的压电扬声器驱动装置， 其中， 所述电感为 130uH; 所述电容为 0.47uF; 所述电阻为 22ohm。
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