Driving circuit for improving sound pressure of piezoelectric buzzer

Abstract

The utility model discloses a driving circuit for improving sound pressure of a piezoelectric buzzer. The driving circuit comprises a master control circuit, a coupling circuit, a filter circuit, an operational amplifier circuit, a voltage division circuit, a current limiting circuit, the piezoelectric buzzer, a low-pass filter circuit and an mos tube switching circuit. The corresponding end of the master control circuit is electrically connected with the corresponding ends of the coupling circuit, the low-pass filter circuit and the current limiting circuit. The coupling circuit is electrically connected with the voltage division circuit and the corresponding end of the piezoelectric buzzer through the filter circuit. The low-pass filter circuit is electrically connected with the corresponding end of the voltage division circuit through the operational amplifier circuit; and the current limiting circuit is electrically connected with the corresponding end of the piezoelectric buzzer through the mos tube switching circuit. The driving circuit designed by the utility model is low in cost, and can achieve the effect of improving the sound pressure of the piezoelectric buzzer.

Description

TECHNICAL FIELD

[0001] The utility model relates to piezoelectric buzzer technical field, especially in improving piezoelectric buzzer sound pressure's drive circuit. BACKGROUND

[0002] Piezoelectric buzzer because its simple structure, low cost, response speed fast etc, in electronic equipment has been widely used, such as in alarm system, timer, toys, communication equipment etc. product as sound prompt element. However, if need to improve sound pressure, the piezoelectric buzzer drive circuit of prior art needs to increase more additional circuit, in some products is not economical.

[0003] Firstly, the traditional piezoelectric buzzer drive circuit usually adopts simple DC power supply, can not raise voltage, this mode can not provide enough sound pressure, lead to the sound of buzzer can not satisfy some application scenarios to the requirement of volume. In order to solve this problem, some designs adopt boost circuit to improve the supply voltage, but this practice increases the complexity and cost of circuit, in some products is inappropriate. UTILITY MODEL CONTENTS

[0004] In view of the problems existing in the prior art, the utility model provides a kind of drive circuit for improving piezoelectric buzzer sound pressure.

[0005] In order to realize the above-mentioned purpose, the utility model technical scheme is as follows:

[0006] The utility model provides a kind of drive circuit for improving piezoelectric buzzer sound pressure, including: main control circuit, coupling circuit, filter circuit, operational amplifier circuit, voltage dividing circuit, current limiting circuit, piezoelectric buzzer, low pass filter circuit, mos tube switch circuit;

[0007] The main control circuit corresponding end is electrically connected with the coupling circuit, low pass filter circuit, current limiting circuit corresponding end respectively;

[0008] The coupling circuit is electrically connected with voltage dividing circuit, piezoelectric buzzer corresponding end respectively through filter circuit;

[0009] The low pass filter circuit is electrically connected with voltage dividing circuit corresponding end through operational amplifier circuit;

[0010] The current limiting circuit is electrically connected with piezoelectric buzzer corresponding end through mos tube switch circuit.

[0011] Preferably, the main control circuit includes MCU, and the model of the MCU is STM32F103C8T6.

[0012] Preferably, the coupling circuit includes a capacitor C1, a diode D1, a capacitor C2, the first end of the diode D1 is electrically connected with a VCC end and the first end of the capacitor C1 respectively, the second end of the diode D1 is electrically connected with the first end of the capacitor C2, a corresponding end of a filter circuit, a corresponding end of a voltage dividing circuit and the first pin of a piezoelectric buzzer respectively, the second end of the capacitor C1 is grounded, and the second end of the capacitor C2 is electrically connected with the PA1 pin of an MCU.

[0013] Preferably, the filter circuit includes a capacitor C3, the first end of the capacitor C3 is electrically connected with the second end of the diode D1, and the second end of the capacitor C3 is grounded.

[0014] Preferably, the voltage dividing circuit includes resistors R3 and R4, the first end of the resistor R3 is electrically connected with the second end of the diode D1, the second end of the resistor R3 and the first end of the resistor R4 are electrically connected with an operational amplifier circuit respectively, and the second end of the resistor R4 is grounded.

[0015] Preferably, the low-pass filter circuit includes a resistor R5 and a capacitor C4, the PA3 pin of the MCU is electrically connected with the first end of the resistor R5 and the first end of the capacitor C4 respectively, the second end of the capacitor C4 is grounded, and the second end of the resistor R5 is electrically connected with a corresponding end of the operational amplifier circuit.

[0016] Preferably, the operational amplifier circuit includes an operational amplifier U2, the non-inverting input of the operational amplifier U2 is electrically connected with the second end of the resistor R3 and the first end of the resistor R4 respectively, and the inverting input of the operational amplifier U2 is electrically connected with the output end of the operational amplifier U2 and the second end of the resistor R5.

[0017] Preferably, the current limiting circuit includes resistors R1 and R2, the PA6 pin of the MCU is electrically connected with the first end of the resistor R2 and a corresponding end of a mos transistor switch circuit through the resistor R1, and the second end of the resistor R2 is grounded.

[0018] Preferably, the mos transistor switch circuit includes a mos transistor Q1, the gate of the mos transistor Q1 is electrically connected with the first end of the resistor R1 and the first end of the resistor R2, the source of the mos transistor Q1 is grounded, and the drain of the mos transistor Q1 is electrically connected with the second pin of the piezoelectric buzzer.

[0019] The technical scheme of the utility model has the following beneficial effects:

[0020] The driving circuit designed in the utility model has low cost and can improve the sound pressure of the piezoelectric buzzer.

[0021] The PA1 and PA6 pins of the single-chip microcomputer U1 are configured as PWM (pulse width modulation) outputs. The PA1 outputs a PWM signal of a fixed frequency (for example, 4KHZ) and a duty cycle (for example, 50%), which is used to drive the basic operation of the piezoelectric buzzer, and the frequency of the PWM signal output by the PA6 pin is set to the resonant frequency of the piezoelectric buzzer. When the frequency of the driving signal matches the resonant frequency of the buzzer, the buzzer can generate the maximum sound pressure, thereby improving the loudness of the sound.

[0022] Since the voltage on the capacitor C2 will rise at the high level of the PWM cycle, a voltage higher than the power supply voltage VBAT can be provided, thereby increasing the sound pressure of the piezoelectric buzzer.

[0023] The filter capacitor C3 of the filter circuit is used to smooth the PWM signal and reduce high-frequency noise, and to ensure that the voltage provided to the piezoelectric buzzer is more stable. The operational amplifier U2 acts as a voltage follower and is used to buffer the signal from the voltage divider resistors R3 and R4, ensuring that the sampling signal input to the MCU is within the appropriate range.

[0024] The current-limiting resistor R1 and the MOSFET gate pull-down resistor R2 of the current-limiting circuit are used to limit the current charging the gate of the NMOS transistor Q1, reduce the speed of the MOSFET switch, prevent oscillation, and reduce noise.

[0025] The low-pass filter circuit composed of the resistor R5 and the capacitor C4 is used to filter out high-frequency noise and facilitate internal ADC collection of the MCU. The mos transistor Q1 acts as a switching element to control the current flow to the piezoelectric buzzer. When Q1 is turned on, the current passes through the buzzer to produce sound. When Q1 is turned off, the buzzer stops making sound. This control method allows the circuit to accurately control the working state of the buzzer. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The utility model discloses a circuit diagram. DETAILED DESCRIPTION

[0027] The embodiments of the utility model are described in detail below, and the examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the utility model, and cannot be understood as limiting the utility model.

[0028] In the description of the utility model, it is necessary to understand that the orientation or positional relation indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like is the orientation or positional relation based on the orientation or positional relation shown in the drawings, which is only for the convenience of describing the utility model and simplifying the description, and therefore cannot be understood as a limitation on the utility model.

[0029] In addition, the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the utility model, the meaning of "multiple" is two or more than two, unless otherwise specifically limited.

[0030] In the utility model, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication between two elements. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0031] In the utility model, unless otherwise specifically defined and limited, the "upper" or "lower" of the first feature in the second feature can include the direct contact of the first and second features, or the indirect contact of the first and second features through another feature between them. Moreover, the "upper", "upper" and "upper" of the first feature in the second feature include the vertical direction of the first feature above and oblique above the second feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The "below", "below" and "below" of the first feature in the second feature include the vertical direction of the first feature below and oblique below the second feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0032] Referring to Figure 1 The utility model provides a kind of drive circuit for improving the sound pressure of piezoelectric buzzer, it include: main control circuit 100, coupling circuit 200, filter circuit 500, operational amplifier circuit 600, voltage division circuit 700, current limiting circuit 400, piezoelectric buzzer 900, low pass filter circuit 300, mos tube switch circuit 800;

[0033] The corresponding end of the main control circuit 100 is electrically connected with the corresponding end of the coupling circuit 200, the low-pass filter circuit 300 and the current limiting circuit 400 respectively;

[0034] The coupling circuit 200 is electrically connected with the corresponding end of the voltage division circuit 700 and the piezoelectric buzzer 900 through the filter circuit 500 respectively;

[0035] The low-pass filter circuit 300 is electrically connected with the corresponding end of the voltage division circuit 700 through the operational amplifier circuit 600;

[0036] The current limiting circuit 400 is electrically connected with the corresponding end of the piezoelectric buzzer 900 through the mos tube switch circuit 800.

[0037] Further, the main control circuit 100 comprises an MCU, the model of the MCU is STM32F103C8T6, the MCU serves as the control center of the whole circuit, is responsible for generating control signals, coordinating the work of each part, can be responsible for processing input signals, controlling PWM output and adjusting frequency.

[0038] Further, the coupling circuit 200 comprises a capacitor C1, a diode D1 and a capacitor C2; the first end of the diode D1 is electrically connected with the VCC end and the first end of the capacitor C1 respectively, the second end of the diode D1 is electrically connected with the first end of the capacitor C2, the corresponding end of the filter circuit, the corresponding end of the voltage division circuit and the first pin of the piezoelectric buzzer respectively, the second end of the capacitor C1 is grounded, and the second end of the capacitor C2 is electrically connected with the PA1 pin of the MCU, the design of the coupling circuit aims to provide stable power voltage, and the output voltage is raised through the coupling capacitor C2, after the voltage on C2 is lifted by D1, the current will not flow reversely to the power supply VCC, and after the raised voltage is smoothed by C3, it is provided to the piezoelectric buzzer 900.

[0039] Further, the filter circuit 500 comprises a capacitor C3; the first end of the capacitor C3 is electrically connected with the second end of the diode D1, and the second end of the capacitor C3 is grounded; the design of the filter circuit aims to reduce voltage fluctuation and noise through the capacitor C3, and to stably provide voltage to the buzzer.

[0040] Further, the voltage division circuit 700 comprises resistors R3 and R4; the first end of the resistor R3 is electrically connected with the second end of the diode D1, the second end of the resistor R3 is electrically connected with the first end of the resistor R4 respectively, and the second end of the resistor R4 is grounded; the design of the voltage division circuit aims to reduce voltage through the combination of the resistors R3 and R4, and to ensure that the operational amplifier circuit will not be damaged due to excessively high voltage. In addition, the MCU can also adjust the frequency of PA1 according to the signal of the voltage division circuit 700 as needed, to adjust the voltage size provided to the buzzer.

[0041] Further, the low pass filter circuit 300 comprises a resistor R5 and a capacitor C4, a PA3 pin of the MCU is electrically connected with a first end of the resistor R5 and a first end of the capacitor C4 respectively, a second end of the capacitor C4 is grounded, and a second end of the resistor R5 is electrically connected with a corresponding end of the operational amplifier circuit 600. The design of the low pass filter circuit 300 aims to filter out high-frequency noise through the combination of the resistor R5 and the resistor C4, so as to ensure that only low-frequency signals can reach the operational amplifier circuit 600.

[0042] Further, the operational amplifier circuit 600 comprises an operational amplifier U2, which is used as a voltage follower, a positive input of the operational amplifier U2 is electrically connected with a second end of the resistor R3 and a first end of the resistor R4 respectively, and an inverting input of the operational amplifier U2 is electrically connected with an output end of the operational amplifier U2 and a second end of the resistor R5. The design of the operational amplifier circuit aims to give a sampling signal input to the MCU a lower impedance, so as to increase the sampling accuracy.

[0043] Further, the current limiting circuit 400 comprises a resistor R1 and a resistor R2, a PA6 pin of the MCU is electrically connected with a first end of the resistor R2 and a corresponding end of the MOS transistor switch circuit through the resistor R1, and a second end of the resistor R2 is grounded. The design of the current limiting circuit aims to control and limit the current through the resistors R1 and R2, reduce the switching speed of the MOS transistor switch circuit 800, reduce noise, and control the MOS transistor through the PA6 pin of the MCU, so as to realize accurate control of the buzzer.

[0044] Further, the MOS transistor switch circuit 800 comprises a MOS transistor Q1, a gate of the MOS transistor Q1 is electrically connected with the first ends of the resistors R1 and R2, a source of the MOS transistor Q1 is grounded, and a drain of the MOS transistor Q1 is electrically connected with a second pin of the piezoelectric buzzer. The MOS transistor Q1 is used as a switching element, and the MOS transistor Q1 controls the current flowing to the piezoelectric buzzer. When the MOS transistor is turned on, the current can flow from the drain to the source, so as to activate the piezoelectric buzzer. When the MOS transistor is turned off, the current stops flowing, and the piezoelectric buzzer stops sounding. The design of the MOS transistor switch circuit aims to control the working state of the piezoelectric buzzer 900 through the MOS transistor Q1, so as to realize the generation and stop of sound.

[0045] The working principle of the utility model is as follows:

[0046] When working, the PA1 and PA6 pins of the MCU U1 are configured as PWM output, the PA1 output frequency is configured at 4KHZ, and the duty cycle is 50%. The PA6 output frequency is configured as the resonance frequency of the piezoelectric buzzer.

[0047] Since the voltage on the capacitor C2 cannot be mutated, when the PA1 pin is at the low level of the PWM, the voltage on the capacitor C2 (at TP1) is the size of VBAT minus the voltage drop Vd on the diode D1. When the PA1 pin is at the high level of the PWM, the voltage of the PA1 pin is about equal to VBAT, at this time, the voltage on the capacitor C2 (at TP1) is the size of 2x VBAT minus the voltage drop Vd on the diode. Therefore, in a cycle, the voltage on the capacitor C2 is (3x VBAT-3Vd) / 2; since the buzzer consumes the current on the C2 when working, the output frequency of the PA1 pin can be adjusted to ensure that the charge on the C2 can meet the buzzer.

[0048] The resistors R3 and R4 divide the output voltage, then enter the operational amplifier U2, and after filtering, enter the internal ADC sampling circuit of the MCU to obtain the voltage on the capacitor C3. The output frequency of the PA1 pin can be adjusted according to the voltage on the capacitor C3, which facilitates the control of the PA1 output frequency, thereby reducing the system power consumption.

[0049] Since the voltage drop Vd on the diode is small, the voltage on the capacitor C2 is greatly improved than VBAT. After the voltage on the capacitor C3 is filtered, it is provided to the piezoelectric buzzer. Since the vibration amplitude of the piezoelectric buzzer is positively correlated with the voltage applied to its two ends, the sound pressure of the piezoelectric buzzer can be increased.

[0050] The above only describes the preferred embodiments of the utility model, and does not limit the patent range of the utility model, and any equivalent structural transformation made under the utility model concept of the utility model, or direct / indirect application in other related technical fields is included in the patent protection range of the utility model.

Claims

1. A drive circuit for increasing the sound pressure of a piezoelectric buzzer, characterized by comprising: Include: Master control circuit, coupling circuit, filter circuit, operational amplifier circuit, voltage dividing circuit, current limiting circuit, piezoelectric buzzer, low pass filter circuit, mos switch circuit; The corresponding end of the master control circuit is respectively electrically connected with the corresponding end of the coupling circuit, the low pass filter circuit and the current limiting circuit; The coupling circuit is respectively electrically connected with the voltage dividing circuit and the corresponding end of the piezoelectric buzzer through the filter circuit. The low pass filter circuit is electrically connected with the corresponding end of the voltage dividing circuit through the operational amplifier circuit. The corresponding end of the piezoelectric buzzer is electrically connected with the current limiting circuit through the mos switch circuit.

2. The driving circuit for improving the sound pressure of a piezoelectric buzzer according to claim 1, characterized by The master control circuit includes MCU, and the model of the MCU is STM32F103C8T6.

3. The driving circuit for improving the sound pressure of a piezoelectric buzzer according to claim 2, characterized by The coupling circuit includes capacitor C1, diode D1 and capacitor C2; the first end of the diode D1 is respectively electrically connected with the VCC end and the first end of the capacitor C1; the second end of the diode D1 is respectively electrically connected with the first end of the capacitor C2, the corresponding end of the filter circuit, the corresponding end of the voltage dividing circuit and the first pin of the piezoelectric buzzer; the second end of the capacitor C1 is grounded, and the second end of the capacitor C2 is electrically connected with the PA1 pin of the MCU.

4. The driving circuit for improving the sound pressure of a piezoelectric buzzer according to claim 3, characterized by The filter circuit includes capacitor C3; the first end of the capacitor C3 is electrically connected with the second end of the diode D1, and the second end of the capacitor C3 is grounded.

5. The driving circuit for improving the sound pressure of a piezoelectric buzzer according to claim 4, characterized by The voltage dividing circuit includes resistor R3 and resistor R4; the first end of the resistor R3 is electrically connected with the second end of the diode D1; the second end of the resistor R3 is electrically connected with the first end of the resistor R4 and the operational amplifier circuit; the second end of the resistor R4 is grounded.

6. The driving circuit for improving the sound pressure of a piezoelectric buzzer according to claim 5, wherein The low pass filter circuit includes resistor R5 and capacitor C4; the PA3 pin of the MCU is respectively electrically connected with the first end of the resistor R5 and the first end of the capacitor C4; the second end of the capacitor C4 is grounded, and the second end of the resistor R5 is electrically connected with the corresponding end of the operational amplifier circuit.

7. The driving circuit for improving the sound pressure of a piezoelectric buzzer according to claim 6, wherein The operational amplifier circuit includes operational amplifier U2; the non-inverting input of the operational amplifier U2 is respectively electrically connected with the second end of the resistor R3 and the first end of the resistor R4; the inverting input of the operational amplifier U2 is electrically connected with the output end of the operational amplifier U2 and the second end of the resistor R5.

8. The driving circuit for improving the sound pressure of a piezoelectric buzzer according to claim 7, characterized by, The current limiting circuit includes resistor R1 and resistor R2; the PA6 pin of the MCU is respectively electrically connected with the first end of the resistor R2 and the corresponding end of the mos switch circuit through the resistor R1; the second end of the resistor R2 is grounded.

9. The driving circuit for improving the sound pressure of a piezoelectric buzzer according to claim 8, wherein The mos switch circuit includes mos Q1; the gate of the mos Q1 is respectively electrically connected with the first end of the resistor R1 and the resistor R2; the source of the mos Q1 is grounded; and the drain of the mos Q1 is electrically connected with the second pin of the piezoelectric buzzer.

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