Buzzer driving circuit and electronic equipment

Abstract

The utility model discloses a buzzer driving circuit and electronic equipment, the buzzer driving circuit comprises a direct current power supply circuit, a transformer and a switching circuit, a pulse width modulation signal from the outside is input to the control end of the switching circuit to control the on and off of the switching circuit, the direct-current power supply circuit provides first alternating voltage for a primary coil of the transformer through the switching circuit, a secondary coil of the transformer is electrically connected with the buzzer so as to provide second alternating voltage for the buzzer, and the second alternating voltage is larger than the first alternating voltage. According to the utility model, the driving voltage of the buzzer is improved, and the output sound effect of the buzzer is increased.

Description

Technical Field

[0001] The present invention relates to the field of buzzer driving, and in particular to a buzzer driving circuit and electronic equipment. Background Art

[0002] Buzzer is an electronic sounder with an integrated structure, which is widely used as a sound-generating device in electronic products such as computers, printers, copiers, alarms, electronic toys, automotive electronic equipment, telephones, timers, etc.

[0003] The buzzer driving circuits currently used all adopt low voltage DC driving, resulting in low sound intensity of the buzzer output. For example, the sound intensity of the buzzer output cannot reach above 70dB, which affects the use effect of the buzzer. Summary of the invention

[0004] The utility model provides a buzzer driving circuit and electronic equipment to improve the sound intensity output by the buzzer.

[0005] The first aspect of the utility model provides a buzzer driving circuit, the buzzer driving circuit comprising: a DC power supply circuit, a transformer, and a switch circuit.

[0006] The pulse width modulation signal from the outside is input to the control end of the switch circuit to control the on and off of the switch circuit.

[0007] The DC power supply circuit provides a first alternating voltage to the primary coil of the transformer via the switch circuit.

[0008] The secondary coil of the transformer is electrically connected to the buzzer to provide a second alternating voltage to the buzzer.

[0009] in,

[0010] The second alternating voltage is greater than the first alternating voltage.

[0011] Preferably, the buzzer driving circuit further comprises a signal generating circuit, which outputs the pulse width modulation signal to the control end of the switch circuit, and the DC power supply circuit also supplies power to the signal generating circuit.

[0012] Preferably, the signal generating circuit is a microprocessor, the general input and output pins of the microprocessor output a pulse width modulation signal, and the duty cycle of the pulse width modulation signal is adjustable.

[0013] Preferably, the DC power supply circuit includes a high potential end and a low potential end.

[0014] Preferably, the switch circuit includes a transistor, the collector of the transistor is electrically connected to one end of the primary coil, the emitter of the transistor is electrically connected to one end of the DC power supply circuit, and the base is used as a control terminal to input a pulse width modulation signal.

[0015] or,

[0016] The switch circuit includes two composite-connected transistors, the base of the first transistor is used as a control terminal to input a pulse width modulation signal, the emitter of the first transistor is electrically connected to the base of the second transistor, the collector of the first transistor is electrically connected to the high potential end of the DC power supply circuit, the collector of the second transistor is electrically connected to one end of the primary coil, and the emitter of the second transistor is electrically connected to the low potential end of the DC power supply circuit.

[0017] Preferably, the DC power supply circuit comprises a first terminal, a second terminal and a ground terminal.

[0018] Preferably, the primary coil of the transformer has a first tap, an intermediate tap, and a second tap, and the intermediate tap is electrically connected to the ground terminal of the DC power supply circuit.

[0019] Preferably, the switch circuit includes a first switch circuit and a second switch circuit, the first switch circuit is connected in series between the first end and the first tap of the DC power supply circuit, and the second switch circuit is connected in series between the second end and the second tap of the DC power supply circuit.

[0020] Preferably, the buzzer driving circuit further comprises a signal generating circuit, the signal generating circuit outputs a first pulse width modulation signal to a control end of the first switch circuit, and outputs a second pulse width modulation signal to a control end of the second switch circuit.

[0021] in,

[0022] The first pulse width modulation signal is opposite to the second pulse width modulation signal.

[0023] Preferably, the DC power supply circuit also supplies power to the signal generating circuit.

[0024] Preferably, the signal generating circuit is a microprocessor, and two general input and output pins of the microprocessor respectively output a first pulse width modulation signal and a second pulse width modulation signal, and the duty ratios of the first pulse width modulation signal and the second pulse width modulation signal are adjustable.

[0025] Preferably, the first end is the positive electrode of the battery, and the second end is the negative electrode of the battery.

[0026] Preferably, the first switch circuit comprises a transistor, the collector of the transistor is electrically connected to the first tap, the emitter of the transistor is electrically connected to the positive electrode of the DC power supply circuit, and the base is used as a control terminal to input the first pulse width modulation signal.

[0027] or

[0028] The second switch circuit includes a transistor, the collector of the transistor is electrically connected to the second tap, the emitter of the transistor is electrically connected to the negative electrode of the DC power supply circuit, and the base is used as a control terminal to input the second pulse width modulation signal.

[0029] or,

[0030] The first switch circuit includes two composite-connected transistors, the base of the first transistor is used as a control terminal to input a first pulse width modulation signal, the emitter of the first transistor is electrically connected to the base of the second transistor, the collector of the first transistor is electrically connected to the positive electrode of the DC power supply circuit, the collector of the second transistor is electrically connected to the first tap of the primary coil, and the emitter of the second transistor is electrically connected to the positive electrode of the DC power supply circuit.

[0031] or,

[0032] The second switching circuit includes two composite-connected transistors, the base of the third transistor serves as a control terminal to input a second pulse width modulation signal, the emitter of the third transistor is electrically connected to the base of the fourth transistor, the collector of the third transistor is electrically connected to the positive electrode of the DC power supply circuit, the collector of the fourth transistor is electrically connected to the second tap of the primary coil, and the emitter of the fourth transistor is electrically connected to the negative electrode of the DC power supply circuit.

[0033] Preferably, the DC power supply circuit includes a high potential end and a low potential end.

[0034] Preferably, the primary coil of the transformer has a first tap, an intermediate tap, and a second tap.

[0035] Preferably, the switch circuit includes a first switch circuit and a second switch circuit.

[0036] The first tap of the primary coil of the transformer is electrically connected to the low potential end of the DC power supply circuit via the first switch circuit.

[0037] The second tap of the primary coil of the transformer is electrically connected to the low potential end of the DC power supply circuit via the second switch circuit.

[0038] The middle tap of the primary coil of the transformer is electrically connected to the high potential end of the DC power supply circuit.

[0039] Preferably, the buzzer driving circuit further comprises a signal generating circuit, the signal generating circuit outputs a first pulse width modulation signal to a control end of the first switch circuit, and outputs a second pulse width modulation signal to a control end of the second switch circuit.

[0040] in,

[0041] The first pulse width modulation signal is opposite to the second pulse width modulation signal.

[0042] The DC power supply circuit also supplies power to the signal generating circuit.

[0043] Preferably, the signal generating circuit is a microprocessor, and two general input and output pins of the microprocessor respectively output a first pulse width modulation signal and a second pulse width modulation signal, and the duty ratios of the first pulse width modulation signal and the second pulse width modulation signal are adjustable.

[0044] Preferably, the first switch circuit comprises a transistor, the collector of the transistor is electrically connected to the first tap, the emitter of the transistor is electrically connected to the low potential end of the DC power supply circuit, and the base is used as a control end to input the first pulse width modulation signal.

[0045] or,

[0046] The second switch circuit includes a transistor, the collector of the transistor is electrically connected to the second tap, the emitter of the transistor is electrically connected to the low potential end of the DC power supply circuit, and the base is used as a control end to input the second pulse width modulation signal.

[0047] or,

[0048] The first switch circuit includes two composite-connected transistors, the base of the first transistor is used as a control terminal to input a first pulse width modulation signal, the emitter of the first transistor is electrically connected to the base of the second transistor, the collector of the first transistor is electrically connected to a high potential end of a DC power supply circuit, the collector of the second transistor is electrically connected to a first tap of a primary coil, and the emitter of the second transistor is electrically connected to a low potential end of a DC power supply circuit.

[0049] or,

[0050] The second switching circuit includes two composite-connected transistors, the base of the third transistor serves as a control terminal to input a first pulse width modulation signal, the emitter of the third transistor is electrically connected to the base of the fourth transistor, the collector of the third transistor is electrically connected to a high potential terminal of a DC power supply circuit, the collector of the fourth transistor is electrically connected to a second tap of the primary coil, and the emitter of the second transistor is electrically connected to a low potential terminal of the DC power supply circuit.

[0051] Preferably, a first reverse electromotive force release circuit and a first protection element are connected in parallel between the first tap and the middle tap, and a second reverse electromotive force release circuit and a second protection element are connected in parallel between the second tap and the middle tap.

[0052] Preferably, a first pull-down resistor is further connected between the base and the emitter of the second transistor.

[0053] Preferably, a second pull-down resistor is connected between the base and emitter of the fourth transistor.

[0054] Preferably, the base of the first transistor is further connected to a first current limiting resistor, and the first pulse width modulation signal is input to the base of the first transistor via the first current limiting resistor.

[0055] Preferably, the base of the third transistor is further connected to a second current limiting resistor, and the second pulse width modulation signal is input to the base of the third transistor via the second current limiting resistor.

[0056] A second aspect of the utility model provides an electronic device, comprising any of the above-mentioned buzzer driving circuits.

[0057] The utility model provides a buzzer driving circuit, wherein a DC power supply circuit provides a first alternating voltage to a primary coil of a transformer via a switch circuit controlled by a pulse width modulation signal, and the transformer outputs a stepped-up second alternating voltage to the buzzer, so that the driving voltage of the buzzer is increased, thereby increasing the sound intensity output by the buzzer, and the driving voltage is adjusted by the duty cycle of the pulse width modulation signal, so that the sound intensity output by the buzzer can be adjusted. The utility model can generate a higher driving voltage under the condition of weak power supply, so that the buzzer can produce a high-decibel sound effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 A schematic diagram of a buzzer driving circuit according to an embodiment of the present application.

[0059] Figure 2 This is another schematic diagram of a buzzer driving circuit according to an embodiment of the present application.

[0060] Figure 3 This is a waveform diagram of a pulse width modulation signal, a voltage at both ends of a switch circuit, and a voltage at both ends of a primary coil of a transformer according to an embodiment of the present application.

[0061] Figure 4 This is a schematic diagram of a buzzer driving circuit according to the second embodiment of the present application.

[0062] Figure 5 This is another schematic diagram of the buzzer driving circuit according to the second embodiment of the present application.

[0063] Figure 6 This is a waveform diagram of the first pulse width modulation signal, the second pulse width modulation signal, the voltage at both ends of the first switch circuit, the voltage at both ends of the second switch circuit, the voltage at both ends of the primary coil between the first tap and the middle tap of the transformer, and the voltage at both ends of the primary coil between the middle tap and the second tap of the transformer in Example 2 of the present application.

[0064] Figure 7A schematic diagram of a buzzer driving circuit. DETAILED DESCRIPTION

[0065] In order to make the objectives, technical means and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings.

[0066] The utility model converts a DC power supply into an AC voltage through a switch circuit and inputs the AC voltage into a transformer, and drives a buzzer after the voltage is stepped up by the transformer, so that the driving voltage of the buzzer is increased, thereby improving the sound intensity output by the buzzer.

[0067] See also Figure 1 As shown, Figure 1 This is a schematic diagram of a buzzer driving circuit according to an embodiment of the present application. The driving circuit includes:

[0068] DC power supply circuit, used to provide DC power,

[0069] The switch circuit is connected in series between the DC power supply circuit and the primary coil of the transformer, and is turned on and off under the control of the pulse width modulation signal, so that the first alternating voltage is input to both ends of the primary coil of the transformer.

[0070] The transformer is used for stepping up the input first alternating voltage and providing the stepped-up second alternating voltage to the buzzer to drive the buzzer.

[0071] The second alternating voltage is greater than the first alternating voltage.

[0072] As an example, see Figure 2 As shown, the driving circuit also includes: a signal generating circuit for generating a pulse width modulation signal to control the on and off of the switch circuit, and the DC power supply circuit also provides a DC power supply for the signal generating circuit.

[0073] The signal generating circuit may be a microprocessor, and the pulse width modulation signal is outputted by a general purpose input and output (GPIO) pin of the microprocessor. The microprocessor may be a microprocessor in an electronic device.

[0074] As an example, the switching circuit is a transistor, and the collector and emitter of the transistor are connected in series between the DC power supply circuit and the primary coil of the transformer as a switch. For example, the collector of the transistor is electrically connected to one end of the primary coil of the transformer, and the emitter of the transistor is electrically connected to one end of the DC power supply circuit, such as the ground end; the base of the transistor is used as a control end to input a pulse modulation signal.

[0075] As another example, the switching circuit is a composite-connected transistor, the base of the first transistor serves as a control terminal to input a pulse width modulation signal, the emitter of the first transistor is electrically connected to the base of the second transistor, the collector of the first transistor is electrically connected to the high potential end of the DC power supply circuit, the collector of the second transistor is electrically connected to one end of the primary coil, and the emitter of the second transistor is electrically connected to the low potential end of the DC power supply circuit.

[0076] See also Figure 3 As shown, Figure 3 The waveform diagram is a pulse width modulation signal, a voltage at both ends of the switch circuit, and a voltage waveform at both ends of the primary coil of the transformer. When the pulse width modulation signal is input to the control end of the switch circuit, when the pulse width modulation signal is at a high level, the switch circuit is turned on, and the power output by the DC power supply circuit is applied to both ends of the primary coil of the transformer. When the pulse width modulation signal is at a low level, the switch circuit is turned off, and the voltage at both ends of the primary coil of the transformer is 0. In this way, a first alternating voltage can be generated at both ends of the primary coil of the transformer. When the duty cycle of the pulse width modulation signal changes, the duty cycle of the first alternating voltage at both ends of the primary coil of the transformer also changes. In this way, the magnitude of the second alternating voltage driving the buzzer is adjustable, and the magnitude of the sound intensity output by the buzzer is adjustable.

[0077] See also Figure 4 As shown, Figure 4 This is a schematic diagram of a buzzer driving circuit of Embodiment 2 of the present application. In this embodiment, the transformer has a first tap, an intermediate tap, and a second tap, the first switch circuit is connected in series with the primary coil between the first tap and the intermediate tap, and the second switch circuit is connected in series with the primary coil between the intermediate tap and the second tap.

[0078] As an example, the DC power supply circuit includes a first terminal, a second terminal and a ground terminal. For example, the DC power supply circuit is two batteries connected in series, the positive pole of the batteries connected in series is the first terminal, the negative pole of the batteries connected in series is the second terminal, and the connection point of the two batteries in series is the ground terminal.

[0079] The primary coil of the transformer has a first tap, a middle tap and a second tap, and the middle tap is electrically connected to the ground terminal of the DC power supply circuit.

[0080] The switch circuit includes a first switch circuit and a second switch circuit, the first switch circuit is connected in series between a first end of the DC power supply circuit and a first tap, and the second switch circuit is connected in series between a second end of the DC power supply circuit and a second tap.

[0081] The first switch circuit includes a transistor, the collector of the transistor is electrically connected to the first tap, the emitter of the transistor is electrically connected to the positive electrode of the DC power supply circuit, and the base is used as a control terminal to input the first pulse width modulation signal.

[0082] or,

[0083] The second switch circuit includes a transistor, the collector of the transistor is electrically connected to the second tap, the emitter of the transistor is electrically connected to the negative electrode of the DC power supply circuit, and the base is used as a control terminal to input the second pulse width modulation signal.

[0084] or,

[0085] The first switch circuit includes two composite-connected transistors, the base of the first transistor is used as a control terminal to input a first pulse width modulation signal, the emitter of the first transistor is electrically connected to the base of the second transistor, the collector of the first transistor is electrically connected to the positive electrode of the DC power supply circuit, the collector of the second transistor is electrically connected to the first tap of the primary coil, and the emitter of the second transistor is electrically connected to the positive electrode of the DC power supply circuit.

[0086] or,

[0087] The second switching circuit includes two composite-connected transistors, the base of the third transistor serves as a control terminal to input a second pulse width modulation signal, the emitter of the third transistor is electrically connected to the base of the fourth transistor, the collector of the third transistor is electrically connected to the positive electrode of the DC power supply circuit, the collector of the fourth transistor is electrically connected to the second tap of the primary coil, and the emitter of the fourth transistor is electrically connected to the negative electrode of the DC power supply circuit.

[0088] As another example, Figure 5 As shown, the DC power supply circuit includes a high potential end and a low potential end, the high potential end is the power supply end, and the low potential end is the ground end. The high potential end of the DC power supply circuit is electrically connected to the middle tap, the first tap of the primary coil of the transformer is electrically connected to the low potential end of the DC power supply circuit via the first switch circuit, the second tap of the primary coil of the transformer is electrically connected to the low potential end of the DC power supply circuit via the second switch circuit, the first pulse width modulation signal is used to control the conduction and shutdown of the first switch circuit, the second pulse width modulation signal is used to control the conduction and shutdown of the second switch circuit, and the first pulse width modulation signal is opposite to the second pulse width modulation signal.

[0089] See also Figure 5 As shown, the buzzer driving circuit also includes a signal generating circuit, which may be a microprocessor. The two GPIO pins of the microprocessor respectively output a first pulse width modulation signal and a second pulse width modulation signal. The microprocessor may be a microprocessor in an electronic device.

[0090] See also Figure 6 As shown, Figure 6The waveform diagram is a first pulse width modulation signal, a second pulse width modulation signal, a voltage at both ends of the first switch circuit, a voltage at both ends of the second switch circuit, a voltage at both ends of the primary coil between the first tap and the middle tap of the transformer, and a voltage at both ends of the primary coil between the middle tap and the second tap of the transformer. When the first pulse width modulation signal is input to the control end of the first switch circuit, when the first pulse width modulation signal is at a high level, the first switch circuit is turned on, and the power output by the DC power supply circuit is applied to both ends of the primary coil between the first tap and the middle tap of the transformer. When the first pulse width modulation signal is at a low level, the first switch circuit is turned off, and the voltage at both ends of the primary coil between the first tap and the middle tap of the transformer is 0. In this way, the first alternating voltage can be generated at both ends of the primary coil between the first tap and the middle tap of the transformer. When the second pulse width modulation signal is input to the control end of the second switch circuit, when the second pulse width modulation signal is at a high level, the second switch circuit is turned on, and the power output by the DC power supply circuit is applied to the two ends of the primary coil between the middle tap and the second tap of the transformer. When the second pulse width modulation signal is at a low level, the second switch circuit is turned off, and the voltage between the two ends of the primary coil between the middle tap and the second tap of the transformer is 0, so that the first alternating voltage can be generated at the two ends of the primary coil between the middle tap and the second tap of the transformer. Since the first pulse width modulation signal and the second pulse width modulation signal are opposite signals, when the first switch circuit is turned on, the second switch circuit is turned off, and when the first switch circuit is turned off, the second switch circuit is turned on.

[0091] When the duty cycle of the pulse width modulation signal changes, the duty cycle of the first alternating voltage across the primary coil of the transformer also changes, so that the magnitude of the second alternating voltage driving the buzzer is adjustable, and the intensity of the sound output by the buzzer is adjustable.

[0092] In this embodiment, although the first switching circuit and the second switching circuit work alternately, the secondary of the transformer can continuously output the second alternating voltage, so that the second alternating voltage is increased compared to a transformer without an intermediate tap. This is beneficial to reducing the transformation ratio between the primary and secondary of the transformer, thereby helping to reduce the volume of the transformer and miniaturize the drive circuit.

[0093] See also Figure 7 As shown, Figure 7The present invention is a schematic diagram of a buzzer driving circuit. The high potential end VDD of the DC power supply is electrically connected to the middle tap of the transformer, the low potential end of the DC power supply, i.e., the ground end, is electrically connected to the first tap of the transformer via the first switch circuit, and is electrically connected to the second tap of the transformer via the second switch circuit. A first reverse electromotive force release circuit and a first protection element are connected in parallel between the first tap and the middle tap, and a second reverse electromotive force release circuit and a second protection element are connected in parallel between the second tap and the middle tap, wherein the first reverse electromotive force release circuit includes: a circuit in which a capacitor C1 and a resistor R5 are connected in series, the second reverse electromotive force release circuit includes: a circuit in which a capacitor C2 and a resistor R6 are connected in series, the first protection element is a bidirectional voltage regulator diode TVS1, and the second protection element is a bidirectional voltage regulator diode TVS2.

[0094] The first switch circuit is two composite-connected transistors, the base of the first transistor Q1 is used as a control end to input a first pulse width modulation signal, the emitter of the first transistor Q1 is electrically connected to the base of the second transistor Q2, the collector of the first transistor Q1 is electrically connected to the high potential end of the DC power supply circuit, the collector of the second transistor Q2 is electrically connected to the first tap of the primary coil, the emitter of the second transistor Q2 is electrically connected to the low potential end of the DC power supply circuit, a first pull-down resistor R3 is also connected between the base and emitter of the second transistor Q2, the base of the first transistor Q1 is also connected to a first current limiting resistor R1, and the first pulse width modulation signal is input to the base of the first transistor Q1 via the first current limiting resistor R1.

[0095] The second switch circuit is two composite-connected triodes, the base of the third triode Q3 is used as a control terminal to input the second pulse width modulation signal, the emitter of the third triode Q3 is electrically connected to the base of the fourth triode Q4, the collector of the third triode Q3 is electrically connected to the high potential end of the DC power supply circuit, the collector of the fourth triode Q4 is electrically connected to the second tap of the primary coil, and the emitter of the fourth triode Q4 is electrically connected to the low potential end of the DC power supply circuit. A second pull-down resistor R4 is also connected between the base and emitter of the fourth triode Q4, and a second current limiting resistor R2 is also connected to the base of the third triode Q3, and the second pulse width modulation signal is input to the base of the third triode Q3 via the second current limiting resistor.

[0096] The DC power supply also includes voltage-stabilizing capacitors CW1-CW2 for suppressing current, one end of the voltage-stabilizing capacitor is electrically connected to the high potential end of the DC power supply circuit, and the other end is electrically connected to the low potential end of the DC power supply circuit.

[0097] In this article, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A buzzer driving circuit, characterized in that: The buzzer driving circuit includes: a DC power supply circuit, a transformer, and a switch circuit. The pulse width modulation signal from the outside is input to the control end of the switch circuit to control the on and off of the switch circuit. The DC power supply circuit provides a first alternating voltage to the primary coil of the transformer via the switch circuit. The secondary coil of the transformer is electrically connected to the buzzer to provide a second alternating voltage to the buzzer. in, The second alternating voltage is greater than the first alternating voltage.

2. The buzzer driving circuit according to claim 1, characterized in that: The buzzer driving circuit also includes a signal generating circuit, which outputs the pulse width modulation signal to the control end of the switch circuit, and the DC power supply circuit also supplies power to the signal generating circuit.

3. The buzzer driving circuit according to claim 2, characterized in that: The signal generating circuit is a microprocessor, the general input and output pins of the microprocessor output a pulse width modulation signal, and the duty cycle of the pulse width modulation signal is adjustable. The DC power supply circuit includes a high potential end and a low potential end. The switch circuit includes a transistor, the collector of the transistor is electrically connected to one end of the primary coil, the emitter of the transistor is electrically connected to one end of the DC power supply circuit, and the base is used as a control end to input a pulse width modulation signal. or, The switch circuit includes two composite-connected transistors, the base of the first transistor is used as a control terminal to input a pulse width modulation signal, the emitter of the first transistor is electrically connected to the base of the second transistor, the collector of the first transistor is electrically connected to the high potential end of the DC power supply circuit, the collector of the second transistor is electrically connected to one end of the primary coil, and the emitter of the second transistor is electrically connected to the low potential end of the DC power supply circuit.

4. The buzzer driving circuit according to claim 1, characterized in that: The DC power supply circuit includes a first terminal, a second terminal and a ground terminal. The primary coil of the transformer has a first tap, an intermediate tap, and a second tap, and the intermediate tap is electrically connected to the ground terminal of the DC power supply circuit. The switch circuit includes a first switch circuit and a second switch circuit, the first switch circuit is connected in series between the first end of the DC power supply circuit and the first tap, and the second switch circuit is connected in series between the second end of the DC power supply circuit and the second tap. The buzzer driving circuit further includes a signal generating circuit, which outputs a first pulse width modulation signal to the control end of the first switch circuit and outputs a second pulse width modulation signal to the control end of the second switch circuit. in, The first pulse width modulation signal is opposite to the second pulse width modulation signal. The DC power supply circuit also supplies power to the signal generating circuit.

5. The buzzer driving circuit according to claim 4, characterized in that: The signal generating circuit is a microprocessor, and two general input and output pins of the microprocessor respectively output a first pulse width modulation signal and a second pulse width modulation signal, and the duty ratios of the first pulse width modulation signal and the second pulse width modulation signal are adjustable. The first end is the positive electrode of the battery, and the second end is the negative electrode of the battery. The first switch circuit includes a transistor, the collector of the transistor is electrically connected to the first tap, the emitter of the transistor is electrically connected to the positive electrode of the DC power supply circuit, and the base is used as a control terminal to input the first pulse width modulation signal, or The second switch circuit includes a transistor, the collector of the transistor is electrically connected to the second tap, the emitter of the transistor is electrically connected to the negative electrode of the DC power supply circuit, and the base is used as a control terminal to input the second pulse width modulation signal. or, The first switch circuit includes two composite-connected transistors, the base of the first transistor is used as a control terminal to input a first pulse width modulation signal, the emitter of the first transistor is electrically connected to the base of the second transistor, the collector of the first transistor is electrically connected to the positive electrode of the DC power supply circuit, the collector of the second transistor is electrically connected to the first tap of the primary coil, and the emitter of the second transistor is electrically connected to the positive electrode of the DC power supply circuit. or, The second switching circuit includes two composite-connected transistors, the base of the third transistor serves as a control terminal to input a second pulse width modulation signal, the emitter of the third transistor is electrically connected to the base of the fourth transistor, the collector of the third transistor is electrically connected to the positive electrode of the DC power supply circuit, the collector of the fourth transistor is electrically connected to the second tap of the primary coil, and the emitter of the fourth transistor is electrically connected to the negative electrode of the DC power supply circuit.

6. The buzzer driving circuit according to claim 1, characterized in that: The DC power supply circuit includes a high potential end and a low potential end. The primary coil of the transformer has a first tap, a middle tap, and a second tap. The switch circuit includes a first switch circuit and a second switch circuit. The first tap of the primary coil of the transformer is electrically connected to the low potential end of the DC power supply circuit via the first switch circuit. The second tap of the primary coil of the transformer is electrically connected to the low potential end of the DC power supply circuit via the second switch circuit. The middle tap of the primary coil of the transformer is electrically connected to the high potential end of the DC power supply circuit. The buzzer driving circuit further includes a signal generating circuit, which outputs a first pulse width modulation signal to the control end of the first switch circuit and outputs a second pulse width modulation signal to the control end of the second switch circuit. in, The first pulse width modulation signal is opposite to the second pulse width modulation signal. The DC power supply circuit also supplies power to the signal generating circuit.

7. The buzzer driving circuit according to claim 6, characterized in that: The signal generating circuit is a microprocessor, and two general input and output pins of the microprocessor respectively output a first pulse width modulation signal and a second pulse width modulation signal, and the duty ratios of the first pulse width modulation signal and the second pulse width modulation signal are adjustable. The first switch circuit includes a transistor, the collector of the transistor is electrically connected to the first tap, the emitter of the transistor is electrically connected to the low potential end of the DC power supply circuit, and the base is used as a control end to input the first pulse width modulation signal. or, The second switch circuit includes a transistor, the collector of the transistor is electrically connected to the second tap, the emitter of the transistor is electrically connected to the low potential end of the DC power supply circuit, and the base is used as a control end to input the second pulse width modulation signal. or, The first switch circuit includes two composite-connected transistors, the base of the first transistor is used as a control terminal to input a first pulse width modulation signal, the emitter of the first transistor is electrically connected to the base of the second transistor, the collector of the first transistor is electrically connected to a high potential end of a DC power supply circuit, the collector of the second transistor is electrically connected to a first tap of a primary coil, and the emitter of the second transistor is electrically connected to a low potential end of a DC power supply circuit. or, The second switching circuit includes two composite-connected transistors, the base of the third transistor serves as a control terminal to input a first pulse width modulation signal, the emitter of the third transistor is electrically connected to the base of the fourth transistor, the collector of the third transistor is electrically connected to a high potential terminal of a DC power supply circuit, the collector of the fourth transistor is electrically connected to a second tap of the primary coil, and the emitter of the second transistor is electrically connected to a low potential terminal of the DC power supply circuit.

8. The buzzer driving circuit according to any one of claims 4 to 7, characterized in that: A first reverse electromotive force release circuit and a first protection element are connected in parallel between the first tap and the middle tap, and a second reverse electromotive force release circuit and a second protection element are connected in parallel between the second tap and the middle tap.

9. The buzzer driving circuit according to claim 7, characterized in that: A first pull-down resistor is also connected between the base and emitter of the second transistor. A second pull-down resistor is also connected between the base and emitter of the fourth transistor. The base of the first transistor is also connected to a first current limiting resistor, and the first pulse width modulation signal is input to the base of the first transistor via the first current limiting resistor. The base of the third transistor is also connected to a second current limiting resistor, and the second pulse width modulation signal is input to the base of the third transistor via the second current limiting resistor.

10. An electronic device, characterized in that: Comprising a buzzer driving circuit as claimed in any one of claims 1 to 9.

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