Buzzer drive system and method

Abstract

This invention provides a buzzer drive system and a buzzer drive method. [Solution] The buzzer drive system is electrically connected to the buzzer and comprises a drive unit 10, a boost unit 20, and a gain estimation unit 30. The drive unit includes a gain control circuit 11 that adjusts the gain of an audio signal S based on a gain coefficient and outputs a drive voltage to the buzzer based on the adjusted audio signal. The boost unit is electrically connected to the drive unit and boosts the input voltage VDD to the drive unit to generate an operating voltage VOUT. The gain estimation unit is electrically connected to the drive unit and the boost unit and generates a plurality of step voltages based on the operating voltage. The gain estimation unit sequentially compares the input voltage with each step voltage to generate an estimated gain. The gain coefficient used in the gain control circuit is determined based on its estimated gain.

Description

Technical Field

[0001] The present invention relates to a buzzer driving system and a method thereof, and more particularly, to a buzzer driving system and a method thereof capable of adjusting the amplification gain of an audio signal by detecting a boost ratio of an operating voltage.

Background Art

[0002] A buzzer is a device that generates sound and is widely used in products such as alarm devices, multimedia devices, car electronics devices, toys, etc. Buzzers are generally classified into piezoelectric types and electromagnetic types. When the buzzer is energized, a metal diaphragm in the buzzer vibrates in a resonance chamber, generating sound.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, since conventional buzzers are mainly driven by digital signals, many buzzers can only generate single tones. In addition, the details of the sound are often filtered by the buzzer, resulting in an output sound quality that is much lower than that of a speaker. However, compared with a speaker, a buzzer has advantages such as small size, high volume, low cost, and durability that cannot be substituted.

[0004] In addition, in order to make the buzzer generate a sufficiently loud sound, it is necessary to connect a voltage booster for increasing the input voltage, thereby increasing the voltage output to the buzzer. However, since conventional buzzers are driven by digital signals and their equivalent circuits can be regarded as capacitors, short pulses of the digital signals are easily filtered, resulting in loss of sound details. In addition, when automatic gain control (AGC) is used to directly control the gain of the audio signal, distortion of the signal waveform may easily occur.

[0005] Therefore, the inventors believed that the above-mentioned shortcomings could be improved, and after diligent research, arrived at the present invention, which effectively improves the above-mentioned problems through a rational design.

[0006] This invention was made through diligent research by the inventors in view of the above-mentioned problems, and its objective is to provide a buzzer drive system and method capable of detecting the boost ratio of the operating voltage in order to adjust the amplification gain of an audio signal. By maintaining sound quality even when the volume of the buzzer is increased, the buzzer helps to reproduce the sonic details embedded in the audio signal. Furthermore, by automatically detecting the boost ratio, the system can be adapted to changes in the input voltage level. [Means for solving the problem]

[0007] To achieve the above objective, a buzzer drive system according to one aspect of the present invention comprises a drive unit, a boost unit, and a gain estimation unit. The drive unit adjusts the gain of the audio signal using a gain control circuit and a gain coefficient, and outputs a drive voltage to the buzzer based on the audio signal. The boost unit is electrically connected to the drive unit and boosts the input voltage to generate an operating voltage for the drive unit. The gain estimation unit is electrically connected to the drive unit and the boost unit and is configured to generate a plurality of step voltages based on the operating voltage. The gain estimation unit sequentially compares the input voltage with each of the step voltages and generates an estimated gain. The gain coefficient of the gain control circuit is set based on the estimated gain.

[0008] Furthermore, in order to achieve the above objective, another embodiment of the present invention, a buzzer driving method, includes the steps of: determining whether an input voltage has been boosted to an operating voltage; if it is determined that the input voltage has been boosted to the operating voltage, sequentially comparing the input voltage with a plurality of step voltages so that an estimated gain is generated; setting a gain coefficient based on the estimated gain; adjusting the gain of the audio signal based on the gain coefficient; and outputting a driving voltage to the buzzer based on the audio signal. [Effects of the Invention]

[0009] As the present invention is configured as described above, it produces the following effects. Compared to conventional methods for driving buzzers and increasing their volume, the buzzer driving system and method can generate the driving voltage based on the audio signal in analog or digital format. This eliminates the limitation of the buzzer's application to the format of the input signal. In addition, the system adjusts the gain coefficient of the audio signal by adapting to changes in the input voltage through an automatic boost ratio detection mechanism. The driving unit then adjusts the gain of the audio signal based on the gain coefficient to increase the buzzer's volume while simultaneously preventing signal distortion, thereby preserving the original detail of the audio signal and improving sound quality.

[0010] The following information will become clear from the description and drawings described later. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing a buzzer drive system according to one embodiment of the present invention. [Figure 2] This is a block diagram showing a buzzer drive system according to another embodiment of the present invention. [Figure 3]This is a schematic diagram showing a gain control circuit in a buzzer drive system according to one embodiment of the present invention. [Figure 4] This is a schematic diagram showing a gain estimation unit in a buzzer drive system according to one embodiment of the present invention. [Figure 5] This flowchart shows a buzzer driving method according to one embodiment of the present invention. [Figure 6] This is another schematic diagram showing a gain estimation unit in a buzzer drive system according to one embodiment of the present invention. [Modes for carrying out the invention]

[0012] The present invention will be described below through embodiments of the invention, but these embodiments are not intended to limit the invention as defined in the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0013] In the example shown in Figure 1, the present invention is primarily characterized by providing a buzzer drive system 1 that increases the volume of the buzzer 2 while maintaining sound quality by detecting the boost ratio of the operating voltage VOUT and adjusting the gain coefficient of the audio signal S. Hereinafter, possible embodiments of the present invention will be described in detail with reference to the drawings. Incidentally, the details described below are not intended to limit the scope of the claims of the present invention, but are intended to facilitate the understanding of those ordinarily skilled in the art to which the present invention belongs.

[0014] The buzzer drive system 1 according to an embodiment of the present invention is electrically connected to the buzzer 2 and comprises a drive unit 10, a boost unit 20, and a gain estimation unit 30. The buzzer drive system 1 is configured as a system independent of the buzzer 2 and is arranged separately. Therefore, the buzzer drive system 1 can be directly applied to an existing buzzer 2 without modifying the structure of the buzzer 2.

[0015] According to embodiments of the present invention, the drive unit 10 is electrically connected to the buzzer 2, receives the audio signal S corresponding to the buzzer 2, and is configured to output a drive voltage D to the buzzer 2 based on the audio signal S. In this way, the buzzer 2 emits sound based on the drive voltage D. The audio signal S may be a digital or analog signal transmitted from an external device. In one embodiment, the audio signal S is a digital signal such as a pulse-width modulation (PWM) signal. In other embodiments, the audio signal S is an analog signal such as a human voice signal, a spoken audio signal, or a musical audio signal. In some embodiments, the analog signal may include an audio signal obtained by audio signal processing applied to a human voice, speech, or musical signal, the processing may include attenuation or enhancement of a specific frequency band. In some embodiments, the analog signal may be generated by applying a low-pass filter to a digital signal such as a PWM signal. The above description is illustrative only and does not limit the scope of protection of the present invention.

[0016] In the example shown in Figure 2, the drive unit 10 includes a gain control circuit 11. The gain control circuit 11 adjusts the gain of the audio signal S based on a gain coefficient, and the drive unit 10 outputs the drive voltage D based on the audio signal S after the gain has been adjusted. The gain coefficient is set based on an estimated gain, and the gain control circuit 11 may dynamically adjust the gain coefficient based on the estimated gain.

[0017] The gain control circuit 11 may comprise an amplifier 111, at least one input resistor Rin, and at least one feedback resistor Rf. As shown in Figure 2, the gain control circuit 11 comprises one input resistor Rin and one feedback resistor Rf. However, in this embodiment, the number of the at least one input resistor Rin and the at least one feedback resistor Rf is not limited. The input resistor Rin is connected in series with the inverting input terminal of the amplifier 111, and the feedback resistor Rf is connected in series between the inverting input terminal and the output terminal of the amplifier 111. A voltage reference ref is applied to the non-inverting input terminal of the amplifier 111. The gain coefficient of the gain control circuit 11 corresponds to the resistance ratio of the at least one feedback resistor Rf and the at least one input resistor Rin, which in this embodiment is the ratio of Rf to Rin. The amplifier 111 adjusts the gain of the audio signal S based on the gain coefficient and outputs the adjusted audio signal S via the output terminal. In other words, the gain control circuit 11 can control the gain by adjusting the resistance values ​​of each feedback resistor Rf and each input resistor Rin, and each input resistor Rin and each feedback resistor Rf may be a variable resistor.

[0018] Returning to Figure 2, the drive unit 10 may include a first-stage amplifier 12 and a second-stage amplifier 13. The first-stage amplifier 12 includes a first input terminal, a second input terminal, and an output terminal. The first input terminal of the first-stage amplifier 12 is electrically connected to the output terminal of the amplifier 111, and after gain adjustment, it receives the audio signal S. The second input terminal of the first-stage amplifier 12 is electrically connected to the voltage reference ref, and the output terminal of the first-stage amplifier 12 is electrically connected to the non-inverting input terminal of the buzzer 2. The first-stage amplifier 12 amplifies the audio signal S and outputs a first voltage via its output terminal.

[0019] The second-stage amplifier 13 includes a first input terminal, a second input terminal, and an output terminal. The first input terminal of the second-stage amplifier 13 is electrically connected to the output terminal of the first-stage amplifier 12 and receives the first voltage. The second input terminal of the second-stage amplifier 13 is electrically connected to the voltage reference ref, and the output terminal of the second-stage amplifier 13 is electrically connected to the negative terminal of the buzzer 2. After the first voltage is amplified, the second-stage amplifier 13 outputs a second voltage via its output terminal.

[0020] The drive voltage D corresponds to the difference between the first voltage and the second voltage. The drive unit 10 outputs the drive voltage D to the buzzer 2 through the first-stage amplifier 12 and the second-stage amplifier 13, and drives the buzzer 2 to emit a sound corresponding to the drive voltage D.

[0021] The boost unit 20 is electrically connected to an external input power supply and the drive unit 10. The boost unit 20 receives the input voltage VDD supplied from the input power supply, boosts the input voltage VDD to generate an operating voltage VOUT, and then outputs the operating voltage VOUT to the drive unit 10 to supply power and maintain its operation. The operating voltage VOUT can also increase the voltage level of the output stage of the drive unit 10. The voltage value of the operating voltage VOUT output from the boost unit 20 can be preset to a fixed value based on the operating requirements of the drive unit 10 and the buzzer 2, but the voltage value of the input voltage VDD may vary depending on the state of the input power supply.

[0022] For example, the operating voltage VOUT can be preset to 18V, and the input voltage VDD may be in the range of 2V to 5V. Regardless of the variation in the voltage value of the input voltage VDD, the boost unit 20 boosts the input voltage VDD to the preset 18V and outputs the boosted input voltage VDD to the drive unit 10. By doing so, the stable operation of the drive unit 10 is ensured without being affected by the variation of the input voltage VDD.

[0023] The gain estimation unit 30 is electrically connected to an external input power supply, the drive unit 10, and the boost unit 20, and receives the input voltage VDD from the input power supply and the operating voltage VOUT from the boost unit 20. A plurality of step voltages generated based on the operating voltage VOUT are preset in the gain estimation unit 30. The gain estimation unit 30 detects the voltage value of the input voltage VDD and generates an estimated gain based on a comparison between the input voltage VDD and the step voltage. Next, the gain estimation unit 30 generates a gain signal M for the drive unit 10 in order to control the gain control circuit 11 to adjust the gain coefficient corresponding to the estimated gain based on the estimated gain. The gain estimation unit 30 controls the gain control circuit 11 to adjust the resistance ratio between the at least one feedback resistor Rf and the at least one input resistor Rin corresponding to the estimated gain by the gain signal M. Alternatively, after receiving the gain signal M, the gain control circuit 11 adjusts the resistance values of the at least one feedback resistor Rf and the at least one input resistor Rin based on the estimated gain.

[0024] On the other hand, after the boost unit 20 boosts the input voltage VDD to generate the operating voltage VOUT, the boost unit 20 transmits a preparation signal R to the gain estimation unit 30, enabling the gain estimation unit 30 to confirm that the boosting operation has been completed and to perform subsequent gain estimation based on the boost ratio.

[0025] In the example shown in Figure 3, in one embodiment, the gain control circuit 11 comprises a multiplexer 14, a plurality of feedback resistors Rf, and an input resistor Rin. The multiplexer 14 is connected between the inverting input terminal and the output terminal of the amplifier 111. The plurality of feedback resistors Rf are connected in series between the multiplexer 14 and the output terminal of the amplifier 111. The multiplexer 14 includes a plurality of input terminals, each connected between two series-connected feedback resistors Rf. The gain control circuit 11 adjusts the gain coefficient of the amplifier 111 by changing the resistance ratio between the connected feedback resistors Rf and the input resistor Rin, by making the number of feedback resistors Rf connected between the inverting input terminal and the output terminal of the amplifier 111 via the multiplexer 14 adjustable.

[0026] Conversely, in another embodiment, the gain control circuit 11 may include another multiplexer 14, a plurality of input resistors Rin, and a feedback resistor Rf. The multiplexer 14 changes the resistance ratio between the input resistors Rin connected to the feedback resistor Rf and the input resistors Rf, thereby adjusting the gain coefficient of the amplifier 111 by adjusting the number of input resistors Rin connected to the inverting input terminal of the amplifier 111.

[0027] In another embodiment, the gain control circuit 11 may include two multiplexers 14, a plurality of feedback resistors Rf, and a plurality of input resistors Rin. The two multiplexers 14 adjust the number of feedback resistors Rf connected between the inverting input terminal and the output terminal of the amplifier 111, and the number of input resistors Rin connected to the inverting input terminal of the amplifier 111, respectively. In this way, the resistance ratio between the connected feedback resistors Rf and the connected input resistors Rin can be modified to flexibly adjust the gain coefficient.

[0028] In the example shown in Figure 4, the gain estimation unit 30 comprises a plurality of voltage divider resistors R, a multiplexer 31, and a comparator 32. The plurality of voltage divider resistors R are connected in series, with one end of each resistor connected in series to the boost unit 20 to receive the operating voltage VOUT, and the other end to ground. Each voltage divider resistor R divides the operating voltage VOUT to generate a plurality of step voltages. The plurality of input terminals of the multiplexer 31 are connected to the plurality of voltage divider resistors R, with each input terminal electrically connected between two voltage divider resistors R. Thus, each input terminal of the multiplexer 31 can receive one of the step voltages by the corresponding voltage divider resistor R. In other words, the multiplexer 31 receives the plurality of step voltages by its plurality of input terminals. The non-inverting input terminal of the comparator 32 is connected to the output terminal of the multiplexer 31 to receive the step voltage output from the multiplexer 31. The inverting input terminal of the comparator 32 may be connected to the boost unit 20 to receive the input voltage VDD. The comparator 32 compares each of the step voltages with the input voltage VDD, and the gain estimation unit 30 calculates and generates the estimated gain based on the comparison results of the comparator 32.

[0029] When the comparator 32 compares each step voltage with the input voltage VDD, the gain estimation unit 30 determines, based on the comparator 32, that the voltage value of the step voltage is not less than the input voltage VDD, but is closest to the input voltage VDD. Next, the estimated gain is calculated based on the ratio of the operating voltage VOUT to the identified step voltage.

[0030] The buzzer 2 may be a piezoelectric buzzer, the main structure of which comprises a piezoelectric element, a metal plate, and a housing. The piezoelectric element may be made of a piezoelectric ceramic material. A voltage is applied to the piezoelectric element, and the piezoelectric effect causes the piezoelectric element to deform, driving the metal plate to vibrate in a way that generates sound. The housing not only surrounds the piezoelectric element and the metal plate, but also forms a resonant cavity for the piezoelectric element and the metal plate.

[0031] Compared to conventional speakers, the buzzer 2 offers advantages such as energy saving, high volume output, compact size, low cost, and high durability. Due to its structural and material properties, the buzzer 2 exhibits greater durability and stability even in harsh environments such as high temperatures and high humidity. Compared to more expensive and easily damaged speakers, the buzzer 2 offers irreplaceable advantages.

[0032] In the example shown in Figure 5, the buzzer driving method according to an embodiment of the present invention is applied to the buzzer 2 and can be executed by the buzzer driving system 1. Steps S10 to S50 may be performed by the gain estimation unit 30, and steps S60 and S70 may be performed by the driving unit 10. The buzzer driving method includes the following steps.

[0033] In step S10, it is determined whether the input voltage VDD has been boosted to the operating voltage VOUT. Specifically, the gain estimation unit 30 determines whether the boosting operation is complete based on the preparation signal R output from the boost unit 20. If it is complete, the subsequent gain estimation can be performed based on the acquired operating voltage VOUT.

[0034] In step S20, if it is determined that the input voltage VDD has been boosted to the operating voltage VOUT, one of the multiple step voltages is powered. Specifically, the multiplexer 31 outputs one of the step voltages to the comparator 32.

[0035] In step S30, the input voltage VDD is compared with the selected step voltage so that it is determined whether the selected step voltage is less than the input voltage VDD. Specifically, the comparator 32 determines whether the step voltage output from the multiplexer 31 is less than the input voltage VDD.

[0036] In step S40, if it is determined that the selected step voltage is not less than the input voltage VDD, the estimated gain is calculated based on the ratio of the operating voltage VOUT to the selected step voltage, and the comparison between the input voltage VDD and the remaining step voltage is completed.

[0037] In step S50, if it is determined that the selected step voltage is less than the input voltage VDD, the next step voltage from the plurality of step voltages is received. The multiplexer 31 outputs the next step voltage to the comparator 32. During the execution of step S30 and when step S50 is executed in overlapping order, the multiplexer 31 outputs the step voltages sequentially in ascending order of voltage level.

[0038] In step S60, the gain coefficient is set based on the estimated gain.

[0039] In step S70, the gain of the audio signal S is adjusted based on the gain coefficient, and a drive voltage D is output to the buzzer 2 based on the audio signal S. More specifically, a first voltage and a second voltage are generated based on the audio signal S, and the drive voltage D corresponds to the voltage difference between the first voltage and the second voltage.

[0040] In the example in Figure 6, the multiplexer 31 is a 5-bit multiplexer, and the plurality of voltage divider resistors R include 33 voltage divider resistors R to generate 32 levels of step voltage. The plurality of voltage divider resistors R include, for example, a first voltage divider resistor R1, a second voltage divider resistor R2, a third voltage divider resistor R3, ..., a 31st voltage divider resistor R31, a 32nd voltage divider resistor R32, a 33rd voltage divider resistor R33, and so on. By setting the resistance values ​​of the voltage divider resistors R, the step voltage generated between the first voltage divider resistor R1 and the second voltage divider resistor R2 becomes 0.55 times the operating voltage VOUT. Each subsequent step voltage differs from the previous step voltage by 0.015 times the operating voltage VOUT. Therefore, the step voltage between the second voltage divider resistor R2 and the third voltage divider resistor R3 is 0.535 times the operating voltage VOUT, the step voltage between the 31st resistor R31 and the 32nd resistor R32 is 0.1 times the operating voltage VOUT, and the step voltage between the 32nd resistor R32 and the 33rd resistor R33 is 0.085 times the operating voltage VOUT. For the sake of simplicity, further details are omitted here.

[0041] When the operating voltage VOUT is 18V and the input voltage VDD is 2.4V, in step S20, the multiplexer 31 first outputs the step voltage, which is the lowest voltage value, to the comparator 32. For example, the step voltage generated between the 32nd voltage divider resistor R32 and the 33rd voltage divider resistor R33 is output to the comparator 32. In steps S30 and S50, since this step voltage is 1.53V (0.085 times the operating voltage VOUT), the comparator 32 determines that the step voltage is less than the input voltage VDD. Next, the multiplexer 31 outputs the next step voltage to the comparator 32. For example, the step voltage is generated between the 31st voltage divider resistor R31 and the 32nd voltage divider resistor R32. Since the next step voltage is 1.8V (0.1 times the operating voltage VOUT), the comparator 32 determines that this step voltage is less than the input voltage VDD. Then, the multiplexer 31 outputs the next step voltage.

[0042] The multiplexer 31 outputs a step voltage of 2.61V (for example, 0.145 times the operating voltage VOUT) to the comparator 32, and the comparator 32 determines that this step voltage exceeds the input voltage VDD. Next, the gain estimation unit 30 calculates the estimated gain based on the ratio of the operating voltage VOUT to this step voltage. Specifically, by calculating the ratio of 1 × VOUT and 0.145 × VOUT, it is determined that the obtained estimated gain is approximately 6.9. This estimated gain is close to the actual gain of 7.5 and corresponds to the ratio of the operating voltage VOUT to the input voltage VDD.

[0043] Incidentally, the above explanation is merely illustrative and does not limit the plurality of step voltages or the gain estimation unit 30 according to this embodiment.

[0044] Furthermore, the accuracy of the detected estimated gain relative to the actual gain is positively correlated with the number of step voltages. As the number of step voltages increases, the voltage difference between each pair of adjacent step voltages decreases. As a result, when the comparator 32 determines that one of the step voltages exceeds the input voltage VDD, the voltage difference between this step voltage and the input voltage VDD decreases. Therefore, the gain estimation unit 30 can calculate a more accurate estimated gain. Thus, the number of step voltages can be set based on the accuracy requirement. As the accuracy requirement increases, the number of step voltages also increases. The accuracy requirement indicates how closely the estimated gain approximates the actual gain. Furthermore, the voltage difference between two adjacent step voltages may be uniform or non-uniform, and the scope of the present invention is not limited to the above examples.

[0045] In summary, the buzzer drive system 1 and the corresponding method described above can generate the drive voltage D based on the audio signal S in analog or digital format. Therefore, the application of the buzzer 2 is not limited by the signal format, and the characteristics of the analog signal enable the buzzer 2 to produce a richer tone instead of a single tone. As a result, the buzzer 2 can achieve sound quality comparable to that of a typical speaker while maintaining the advantages of high volume output, low material cost, and high durability.

[0046] In addition, according to embodiments of the present invention, the buzzer drive system 1 is capable of detecting the boost ratio for which the boost unit 20 converts the input voltage VDD to the operating voltage VOUT. An automatic gain estimation mechanism based on the boost ratio allows the system to adapt to fluctuations in the input voltage VDD so as to adjust the gain coefficient of the audio signal S. In this way, the drive unit 10 increases the volume generated by the buzzer 2 based on the drive voltage D by amplifying the audio signal S with an appropriate gain coefficient. At the same time, it achieves the objective of preventing distortion of the audio signal S when the volume is increased and improving sound quality while maintaining the detail of the original sound.

[0047] The present invention can be implemented in various other forms without departing from its spirit or main features. Therefore, the embodiments described above are merely illustrative in all respects and should not be constrained. The scope of the invention is defined by the claims and is not restricted by the text of the specification. Furthermore, any modifications or changes within the equivalent scope of the claims are all within the scope of the invention. [Explanation of Symbols]

[0048] 1. Buzzer drive system 2 Buzzer 10 Drive Unit 11 Gain control circuit 111 Amplifier 12. First Stage Amplifier 13. Second Stage Amplifier 14 Multiplexer 20 Boost Unit 30 Gain Estimation Units 31 Multiplexer 32 Comparators S10~S70 Step S audio signal D Drive Voltage M gain signal R voltage divider resistor VDD input voltage VOUT Operating Voltage Ref Voltage Reference R1 Voltage divider resistor R2 Voltage divider resistor R3 Voltage divider resistor R31 Voltage Divider Resistor R32 Voltage Divider Resistor R33 Voltage Divider Resistor Rf feedback resistor Rin input resistance

Claims

1. A buzzer drive system (1) electrically connected to buzzer (2), A drive unit (10) includes a gain control circuit (11) configured to adjust the gain of an audio signal (S) based on a gain coefficient determined by the gain control circuit (11), and outputs a drive voltage (D) to the buzzer (2) based on the adjusted audio signal (S), A boost unit (20) is electrically connected to the drive unit (10) and is configured to boost the input voltage (VDD) so as to generate an operating voltage (VOUT) for the drive unit (10), The system includes a gain estimation unit (30) which is electrically connected to the drive unit (10) and the boost unit (20), and is configured to generate a plurality of step voltages based on the operating voltage (VOUT) and to sequentially compare the input voltage (VDD) with each of the step voltages to generate an estimated gain, A buzzer drive system characterized in that the gain coefficient used in the gain control circuit (11) is determined based on the estimated gain.

2. The buzzer driving system according to claim 1, wherein the gain estimation unit (30) comprises a comparator (32) having a non-inverting input terminal configured to receive each of the step voltages and an inverting input terminal configured to receive the input voltage (VDD), and the comparator (32) is configured to compare each of the step voltages with the input voltage (VDD) to generate the estimated gain.

3. The gain estimation unit (30) further comprises a plurality of voltage divider resistors (R) and a multiplexer (31), wherein the voltage divider resistors (R) are connected in series between the operating voltages (VOUT) and are grounded to generate the step voltage. The buzzer drive system according to claim 1 or 2, characterized in that the multiplexer (31) has a plurality of input terminals, each connected between a pair of voltage divider resistors (R), and an output terminal connected to the non-inverting input terminal of the comparator (32) to selectively output each of the step voltages to the comparator (32).

4. The buzzer drive system according to any one of claims 1 to 3, characterized in that the gain estimation unit (30) is configured to determine a step voltage that is not less than the input voltage (VDD) and is closest to the input voltage (VDD), and to calculate the estimated gain based on the voltage division ratio between the operating voltage (VOUT) and the determined step voltage.

5. The buzzer drive system according to any one of claims 1 to 4, characterized in that the multiplexer (31) is configured to sequentially output the step voltages to the comparator (32) from the lowest voltage to the highest voltage, and if the comparator (32) determines that one of the step voltages exceeds the input voltage (VDD), the gain estimation unit (30) stops the comparison.

6. The buzzer driving system according to claim 1, wherein the gain control circuit (11) comprises an amplifier (111) connected to at least one input resistor (Rin) and at least one feedback resistor (Rf), and the gain control circuit (11) is configured to adjust the resistance ratio between the at least one feedback resistor (Rf) and the at least one input resistor (Rin) based on the estimated gain in order to control the gain coefficient.

7. A step in which it is determined whether the input voltage (VDD) has been boosted to the operating voltage (VOUT), When the input voltage (VDD) is boosted to the operating voltage (VOUT), the input voltage (VDD) is sequentially compared with a plurality of step voltages so that an estimated gain is generated. The steps include setting the gain coefficient based on the estimated gain, The steps include adjusting the gain of the audio signal (S) based on the gain coefficient, A buzzer driving method characterized by including the step of outputting a drive voltage (D) to the buzzer (2) based on the adjusted audio signal (S).

8. The steps that are sequentially compared are, A step in which each of the aforementioned step voltages is compared with the input voltage (VDD) from the lowest voltage to the highest voltage, If the current step voltage is less than the input voltage (VDD), a step is taken in which the input voltage (VDD) and the next step voltage are compared. The buzzer driving method according to claim 7, characterized in that if it is determined that one of the step voltages is not less than the input voltage (VDD), the comparison between the input voltage (VDD) and any of the remaining step voltages is stopped.

9. The buzzer driving method according to claim 7, characterized in that the estimated gain is calculated based on the voltage division ratio between the operating voltage (VOUT) and a step voltage that is not less than the input voltage (VDD) and is closest to the input voltage (VDD).

10. The buzzer driving method according to claim 7, characterized in that the quantity of the step voltage is positively correlated with the required accuracy, and the quantity of the step voltage increases as the required accuracy increases.

Images