TWI591924B - Overload Protection Circuit Of Piezoelectric Element - Google Patents

Description

Piezoelectric element overload protection circuit

The invention provides an overload protection circuit, in particular to an overload protection circuit for a piezoelectric element.

Piezoelectric effect is a phenomenon in which a mechanical energy and electrical energy are converted into each other in a dielectric material. Among them, a dielectric material that can produce a piezoelectric effect is generally referred to as a piezoelectric material. It is known that the piezoelectric material has a piezoelectric effect due to the special arrangement between atoms in its crystal lattice, and there may be an effect of coupling the stress field and the electric field. Therefore, a piezoelectric element made of a piezoelectric material can be widely used in many fields by utilizing a piezoelectric effect.

Conventionally, the piezoelectric effect can be divided into a positive piezoelectric effect that converts mechanical energy into electrical energy and an inverse piezoelectric effect that converts electrical energy into mechanical energy. In the application of the inverse piezoelectric effect, the mechanical energy output by the vibration of the piezoelectric element is generally used to drive (or vibrate) the external load in contact with it to achieve the desired effect of the application. When the load is water as an example, the water can be driven by the mechanical energy output by the vibration of the piezoelectric element, so that the water can be refined into fine water droplets due to the vibration of the piezoelectric element.

The piezoelectric element is a frequency control element. Therefore, when the piezoelectric element operates normally at a fixed frequency and is driven in a stable state, the operating current of the piezoelectric element can be maintained within a small range. However, since the external load may vary for some reason, the operating current of the piezoelectric element also changes. Especially when the operating current of the piezoelectric element exceeds the normal variation range of the load of the piezoelectric element due to the variation of the external load, the piezoelectric element may be seriously damaged. damage.

In view of the above, the present invention provides an overload protection circuit for a piezoelectric element, which can stop the operation of the piezoelectric element when it is detected that the operating current of the piezoelectric element exceeds a normal range of loadability to avoid damage of the piezoelectric element.

In an embodiment, an overload protection circuit for a piezoelectric element includes a current sampling unit and a regulation unit. The current sampling unit can sequentially sample the analog signal according to the complex control code to generate a sampling signal. The control unit may sequentially generate the complex control code, and after obtaining the corresponding reference signal according to the control code when the sampling signal is changed, comparing the potential and the threshold of the reference signal, and when the potential of the reference signal is greater than the threshold, the control unit Stop outputting the pulse modulation signal to stop the piezoelectric element. The magnitude of the analog signal is related to the operating current of the piezoelectric element.

In an embodiment, a method for overload protection of a piezoelectric element includes receiving an analog signal, sequentially generating a complex control code, sequentially sampling an analog signal according to the control code to generate a sampling signal, and controlling a code according to a sampling signal. The corresponding reference signal is obtained, the potential and the threshold of the reference signal are compared, and when the potential of the reference signal is greater than the threshold, the output of the pulse modulation signal is stopped to stop the piezoelectric element. The magnitude of the analog signal is related to the operating current of the piezoelectric element.

In summary, the overload protection circuit of the piezoelectric element according to the embodiment of the present invention and the method thereof, by sampling the operating current of the piezoelectric element, can quickly react when detecting that the operating current of the piezoelectric element exceeds a critical value. The output of the pulse modulation signal is stopped to stop the piezoelectric element from being operated to avoid damage of the piezoelectric element.

The detailed features and advantages of the present invention are described in detail in the embodiments of the present invention. The objects and advantages associated with the present invention can be readily understood by those skilled in the art.

100‧‧‧Piezoelectric components

110‧‧‧First drive electrode

120‧‧‧second drive electrode

200‧‧‧Overload protection circuit

210‧‧‧current sampling unit

211‧‧‧Digital Analog Conversion Unit

212‧‧‧Comparative unit

220‧‧‧Control unit

240‧‧‧current to voltage unit

250‧‧‧ Noise Elimination Unit

260‧‧‧Amplification unit

270‧‧‧Resonance unit

271‧‧‧Capacitive components

272‧‧‧Switch Module

273‧‧‧Inductive components

A1‧‧‧ analog signal

C0‧‧‧Static capacitor

C1‧‧‧ Dynamic Capacitance

D1-Dn‧‧‧ control code

F1‧‧‧ series resonant frequency

F2‧‧‧ parallel resonant frequency

I1‧‧‧ working current

L1‧‧‧dynamic inductor

R1‧‧‧ dynamic resistance

R2‧‧‧ resistance

Sr1-Srn, Srx‧‧‧ reference signal

Gnd‧‧‧ Ground potential

Ss‧‧‧Sampling signal

Sp‧‧‧ pulse modulation signal

Vcc‧‧‧ power supply potential

Z _max ‧‧‧maximum impedance value

Z _min ‧‧‧minimum impedance value

Step S10a‧‧‧ generates an analog signal based on the operating current

Step S10b‧‧‧ Eliminate noise on the analog signal

Step S10c‧‧‧Enlarge analog signal

Step S11‧‧‧ Receive analog signal

Step S12‧‧‧ Generate multiple control codes in sequence

Step S13‧‧‧Sampling the analog signal according to the complex control code to generate the sampling signal

Step S13a‧‧‧ sequentially generates reference signals according to each control code

Step S13b‧‧‧ generates sampling signals according to each reference signal and analog signal

Step S14‧‧‧ obtain the corresponding reference signal according to the control code when the sampling signal is changed

Step S15‧‧‧Compare the potential and threshold of the reference signal

Step S16a‧‧‧ Stop outputting the pulse modulation signal to stop the piezoelectric element

Step S16b‧‧‧ Output pulse modulation signal

Fig. 1 is a schematic equivalent circuit diagram of a piezoelectric element.

Fig. 2 is a schematic diagram showing the relationship between impedance versus frequency of a piezoelectric element.

Fig. 3 is a schematic view showing a driving circuit for driving a piezoelectric element according to an embodiment of the present invention.

4 is a schematic view showing a driving circuit driving a piezoelectric element according to another embodiment of the present invention.

[Fig. 5] is a schematic diagram showing the comparison of the analog signals by the complex reference signals.

Fig. 6 is a schematic view showing a method of overload protection of a piezoelectric element according to an embodiment of the present invention.

In general, the piezoelectric element 100 is made of a piezoelectric material, and the piezoelectric effect is used to achieve mutual conversion between mechanical energy and electrical energy. Herein, the effect of generally converting mechanical energy into electrical energy is called a positive piezoelectric effect, and the effect of converting electrical energy into mechanical energy is called an inverse piezoelectric effect.

In some embodiments, the piezoelectric material to which the piezoelectric element 100 is applied may be, but not limited to, a piezoelectric single crystal such as quartz, lithium niobate (LiNbO ₃ ), lithium niobate (LiTaO ₃ ), etc., piezoelectric polycrystal. (Piezoelectric ceramics), such as barium titanate (BT), lead zirconate titanate (PZT), etc., piezoelectric polymers such as PVDF and copolymers thereof, polyvinyl fluoride, etc. or piezoelectric composite materials such as piezoelectric ceramics and A two-phase composite of polymers.

1 is a schematic equivalent circuit diagram of a piezoelectric element. Please refer to Figure 1, piezoelectric element 100 has a first drive electrode 110 and a second drive electrode 120. Here, the piezoelectric element 100 can be equivalent to a resonant circuit composed of a static capacitor C0, a dynamic capacitor C1, a dynamic inductor L1, and a dynamic resistor R1. The dynamic capacitor C1, the dynamic inductor L1 and the dynamic resistor R1 are connected in series with each other between the first driving electrode 110 and the second driving electrode 120, and the two ends of the static capacitor C0 are respectively coupled to the first driving electrode 110 and the second The driving electrode 120 can be connected in parallel to the dynamic capacitor C1, the dynamic inductor L1 and the dynamic resistor R1 which are connected in series.

Fig. 2 is a schematic diagram showing the relationship between the impedance of the piezoelectric element and the frequency. Referring to FIG. 1 and FIG. 2, since the piezoelectric element 100 is a frequency control element, when the piezoelectric element 100 operates at different frequencies, its impedance will change accordingly. Here, when the piezoelectric element 100 operates at the series resonance frequency F1, the equivalent circuit of the piezoelectric element 100 is resistive, and the impedance of the piezoelectric element 100 is approximately equal to the size of the dynamic resistance R1 and has the minimum impedance value. Z _min ; and when the piezoelectric element 100 operates at the parallel resonance frequency F2, the equivalent circuit of the piezoelectric element 100 is inductive, and the impedance of the piezoelectric element 100 may have a maximum impedance value Z _max . Therefore, in a general application, the piezoelectric element 100 operates at the series resonance frequency F1 so that the impedance of the piezoelectric element 100 can be minimized and the operating current I1 flowing through the piezoelectric element 100 can have a maximum value, thereby obtaining the pressure. The maximum mechanical energy output of the electrical component 100.

3 is a schematic diagram of an overload protection circuit for protecting a piezoelectric element according to an embodiment of the present invention, and FIG. 4 is a schematic diagram of an overload protection circuit for protecting a piezoelectric element according to another embodiment of the present invention. Referring to FIG. 3 and FIG. 4, the piezoelectric element 100 can be actuated according to the pulse modulation signal Sp to convert electrical energy into corresponding mechanical energy and output corresponding mechanical energy to an external load (not shown). In one embodiment, the frequency of the pulse modulation signal Sp is substantially the same as the series resonant frequency F1 of the piezoelectric element 100. Wherein, the overload protection circuit 200 can use the frequency chasing technology to find the equivalent The pulse modulation signal Sp of the frequency of the series resonance frequency F1 of the piezoelectric element 100.

In some embodiments, the overload protection circuit 200 can generate a pulse modulation signal Sp at a fixed frequency (corresponding to the series resonant frequency F1 of the piezoelectric element 100). In other embodiments, the pulse modulation signal Sp can also be generated by other circuits, such as a signal generating circuit (not shown), and the overload protection circuit 200 can output a control signal to the signal generating circuit to generate the signal. The circuit can output a pulse modulation signal Sp having a corresponding frequency or stop outputting the pulse modulation signal Sp according to the control signal.

Here, in the case where the external load of the piezoelectric element 100 is not changed, the operating current I1 of the piezoelectric element 100 may tend to be constant (or maintained within a small range).

After the overload protection circuit 200 determines the frequency of the pulse modulation signal Sp (completes the frequency chasing), the overload protection circuit 200 can also sample the operating current I1 of the piezoelectric element 100 to detect whether the piezoelectric element 100 is overloaded.

The overload protection circuit 200 includes a current sampling unit 210 and a regulation unit 220. The current sampling unit 210 is coupled to the piezoelectric element 100 , and the regulating unit 220 is coupled to the current sampling unit 210 and the piezoelectric element 100 . The current sampling unit 210 can perform a plurality of sampling procedures, and samples the operating current I1 of the piezoelectric element 100 according to the complex control codes D1-Dn generated by the regulating unit 220 in each sampling process to output the sampling signal Ss according to the sampling result. . The control unit 220 can obtain the corresponding reference signal according to the control code when the sampling signal Ss is in the transition state, and then compare the potential of the reference signal with the preset threshold value, and the result of the comparison is that the potential of the reference signal is greater than the critical value. At the time of the value, the output pulse modulation signal Sp is stopped to be quickly reacted to stop the piezoelectric element 100 from operating. Here, the transition of the sampling signal Ss refers to a period in which the level of the sampling signal Ss transitions from a logic "0" to a logic "1" or a logic "1" to a logic "0".

In some embodiments, the current sampling unit 210 can include a digital analog conversion unit 211 and a comparison unit 212. The input end of the digital analog conversion unit 211 is coupled to the control unit 220. The two input ends of the comparison unit 212 are respectively coupled to the output ends of the piezoelectric element 100 and the digital analog conversion unit 211.

The digital analog conversion unit 211 can be used to convert the corresponding analog signal output according to the value of the digital signal. Here, the digital analog conversion unit 211 can generate a plurality of reference signals Sr1 - Srn according to the plurality of control codes D1 - Dn.

In some embodiments, the plurality of control codes D1-Dn may be sequentially generated by the control unit 220 in a descending manner, that is, the control code D1 generated by the control unit 220 will have the largest value, and the control code generated by the control unit 220 Dn will have the smallest value. However, the present invention is not limited thereto. The plurality of control codes D1-Dn may also be sequentially generated by the control unit 220 in an ascending order, or may be sequentially generated by the control unit 220 in the order defined by the user.

Taking a plurality of control codes D1-Dn sequentially generated in descending order as an example, the first reference signal Sr1 converted by the digital analog conversion unit 211 according to the first control code D1 is greater than that converted according to the second control code D2. The second reference signal Sr2 is output, and the second reference signal Sr2 converted by the digital analog conversion unit 211 according to the second control code D2 is greater than the third reference signal converted according to the third control code D3. Sr3, and so on to the last reference signal Srn.

In some implementations, the digital analog conversion unit 211 can be a digital to analog converter (DAC) mainly composed of passive components, such as a resistive digital analog converter or a switched capacitive digital analog converter. , or a digital analog converter composed mainly of active components, such as a weighted current source digital analog converter or a moment Array current source digital analog converter. However, the invention is not limited thereto. Here, the digital analog conversion unit 211 can be implemented with a simple architecture R-2R type digital analog converter to reduce the overall cost of the overload protection circuit 200.

The comparison unit 212 has two inputs, which can be referred to as an inverting input and a non-inverting input, respectively. The inverting input terminal of the comparing unit 212 is coupled to the digital analog converting unit 211 , and the non-inverting input terminal of the comparing unit 212 is coupled to the piezoelectric element 100 .

In some embodiments, the overload protection circuit 200 further includes a current-to-voltage unit 240, and the current-to-voltage unit 240 is coupled between the piezoelectric element 100 and the non-inverting input of the comparison unit 212. The current-to-voltage unit 240 can convert the operating current I1 into a corresponding analog signal A1 and then output it to the comparing unit 212. The magnitude of the analog signal A1 generated by the current-to-voltage unit 240 is related to the magnitude of the operating current I1 of the piezoelectric element 100. Here, the analog signal A1 is positively related to the operating current I1. In other words, the larger the operating current I1 of the piezoelectric element 100 is, the larger the analog signal A1 generated by the current converting voltage unit 240 is.

In addition, the magnitude of the operating current I1 of the piezoelectric element 100 is also related to the magnitude of the impedance of the piezoelectric element 100 and the magnitude of the impedance of the load outside the driving thereof, and the operating current I1 is negatively related to the impedance of the piezoelectric element 100 and The magnitude of the impedance at the load. Therefore, the magnitude of the analog signal A11 generated by the current-to-voltage unit 240 is also related to the impedance of the piezoelectric element 100 and the impedance of the external load, and the analog signal A1 is negatively related to the impedance of the piezoelectric element 100 and The magnitude of the impedance at the load. In other words, the larger the analog signal A1 generated by the current-to-voltage unit 240, the smaller the impedance of the piezoelectric element 100 and the impedance of the external load, and the larger the operating current I1 flowing through the piezoelectric element 100.

Here, the impedance of the piezoelectric element 100 is related to the frequency of the pulse modulation signal Sp. rate. At that time, the impedance of the piezoelectric element 100 was also a fixed impedance. Therefore, when the frequency of the pulse modulation signal Sp is a fixed frequency, the analog signal A1 can only be related to the impedance of the external load, and the larger the analog signal A1, the smaller the impedance representing the external load and flowing through the piezoelectric The operating current I1 of the component 100 is larger. In other words, the overload protection circuit 200 can thereby determine whether the external load is stable according to the magnitude change of the analog signal A1.

In some implementations, the current-to-voltage unit 240 can be a resistor R2 having one end coupled to the ground potential Gnd, such as a zero potential, and the other end coupled to the non-inverting input of the piezoelectric element 100 and the comparison unit 212. In order to make the working current I1 form a corresponding voltage across the resistor R2, the corresponding analog signal A1 to the comparison unit 212 can be converted. The analog signal A1 is a voltage signal, and the resistor R2 can be a fixed resistor.

Here, the comparison unit 212 sequentially compares the analog signal A1 converted by the current-to-voltage unit 240 with the plurality of reference signals Sr1-Srn one by one to generate the sampling signal Ss.

In some implementations, the comparison unit 212 can be a comparison circuit composed of an operational amplifier, but the invention is not limited thereto.

In some embodiments, the overload protection circuit 200 further includes a noise cancellation unit 250 , and the noise cancellation unit 250 is coupled between the piezoelectric element 100 and the comparison unit 212 . The noise cancellation unit 250 can be coupled between the voltage conversion unit 240 and the comparison unit 212 to eliminate the noise on the analog signal A1 generated by the voltage conversion unit 240, and then output to the comparison unit 212 for comparison. .

In some implementations, the noise cancellation unit 250 can be a filter composed of capacitors to filter out noise on the analog signal A1, but the invention is not limited thereto.

In some embodiments, the overload protection circuit 200 further includes an amplification unit 260, The amplification unit 260 is coupled between the piezoelectric element 100 and the comparison unit 212. The amplification unit 260 can be coupled between the voltage conversion unit 240 and the comparison unit 212 to amplify the analog signal A1 generated by the voltage conversion unit 240, and then output to the comparison unit 212 for comparison. In addition, the amplifying unit 260 can also be coupled between the noise canceling unit 250 and the comparing unit 212, so that the analog signal A1 can be cancelled by the noise canceling unit 250 before being amplified by the amplifying unit 260, and then output to the analog signal 260. Comparison unit 212 performs the comparison.

Therefore, the control unit 220 of the overload protection circuit 200 can sequentially generate the control code D1-Dn to the digital analog conversion unit 211, so that the comparison unit 212 can classify the analog signal A1 and the digital analog conversion unit 211 according to the first control code D1-Dn. The generated reference signals Sr1-Srn are sequentially compared, and the sampling signal Ss is generated to the control unit 220, so that the control unit 220 can decide whether to continue to output the control codes D1-Dn sequentially according to whether the sampling signal Ss is in a transition state.

In an embodiment in which the control unit 220 generates the control codes D1-Dn in descending order, as shown in FIG. 5, in each sampling program, first, the digital analog conversion unit 211 generates the first according to the first control code D1. The reference signal Sr1, and the comparing unit 212 can compare the first reference signal Sr1 with the analog signal A1. Since the potential of the first reference signal Sr1 is greater than the potential of the analog signal A1, the level of the sampling signal Ss generated by the comparing unit 212 can be logic "0". Until the digital analog conversion unit 211 generates the xth reference signal Srx according to the xth control code, and the comparing unit 212 compares the xth reference signal Srx with the analog signal A1, the comparing unit 212 can determine the xth reference signal. The potential of Srx is less than the potential of the analog signal A1 such that the level of the sampling signal Ss is shifted from a logic "0" to a logic "1". When the sampling signal Ss transitions, the control unit 220 stops outputting the next first control code, and obtains the reference signal Srx generated by the digital analog conversion unit 211 according to the current control code. When the potential of the reference signal Srx is used as the piezoelectric element 100 to drive the external load, the current-to-voltage unit 240 can convert the maximum potential of the analog signal A1 according to the operating current I1 of the piezoelectric element 100.

In an embodiment in which the control unit 220 generates the control codes D1-Dn in an ascending order, in each sampling procedure, when the sampling signal Ss is in a transition state, the control unit 220 stops outputting the next control code, and Obtaining the potential of the reference signal Srx generated correspondingly by the digital analog conversion unit 211 according to the current control code, and using the potential of the reference signal Srx as the piezoelectric element 100 to drive the external load, the current-to-voltage unit 240 according to the piezoelectric element The minimum potential of the analog signal A1 can be converted by the operating current I1 of 100.

In the implementation manner of the control unit 220 in the order defined by the user, in each sampling procedure, the control unit 220 can perform all the transition states corresponding to the sample signal Ss according to the transition state of the sampling signal Ss. The potential of each reference signal is averaged, and the average value obtained is used as the piezoelectric element 100 under the current frequency control of the pulse modulation signal Sp. The current-to-voltage unit 240 can be converted according to the operating current I1 of the piezoelectric element 100. The average potential of the analog signal A1 is converted out.

Therefore, the control unit 220 can compare the potential of the reference signal obtained in each sampling procedure with a preset threshold value, and perform corresponding actions according to the comparison result. When the result of the comparison is that the potential of the reference signal is less than or equal to the preset threshold, it indicates that the variation of the external load is still within the stable range, and the operating current 11 flowing through the piezoelectric element 100 is still interposed between the piezoelectric element 100. Within the load range. Therefore, the control unit 220 can normally output the pulse modulation signal Sp to continue the operation of the piezoelectric element 100.

When the result of the comparison is that the potential of the reference signal is greater than a preset threshold, then It is indicated that the variation of the external load has exceeded the stable range, and the operating current I1 flowing through the piezoelectric element 100 has exceeded the range (ie, overload) at which the piezoelectric element 100 can be loaded. Therefore, the control unit 220 can quickly react and stop outputting the pulse modulation signal Sp to stop the piezoelectric element 100, thereby protecting the piezoelectric element 100 from being damaged by the excessive operating current I1.

In some embodiments, the overload protection circuit 200 further includes a resonance unit 270 , and the resonance unit 270 is coupled between the piezoelectric element 100 , the regulation unit 220 , and the comparison unit 212 . The resonant unit 270 can be used to actuate according to the pulse modulation signal Sp outputted by the control unit 220, thereby controlling the operating current 11 of the piezoelectric element 100.

In some implementations, the resonant unit 270 can include a capacitive element 271, a switch module 272, and an inductive element 273. The one end of the capacitive element 271 can be coupled to the first driving electrode 110 of the piezoelectric element 100. The inductive component 273 can be coupled between the other end of the capacitive component 271 and a power supply potential Vcc. One end of the switch module 272 can be coupled to the non-inverting input end of the comparison unit 212, and the other end of the switch module 272 can be coupled to the other end of the capacitive element 271 and one end of the inductive element 273, and the switch module 272 The control end is coupled to the output end of the control unit 220. Therefore, the switch module 272 can control the electrical connection between the capacitive element 271 and the comparison unit 212 according to the pulse modulation signal Sp.

In one embodiment, the second driving electrode 120 of the piezoelectric element 100 can be coupled to the non-inverting input of the comparing unit 212, as shown in FIG. However, the present invention is not limited thereto. In another embodiment, as shown in FIG. 4, the second driving electrode 120 of the piezoelectric element 100 can be coupled to the ground potential Gnd.

In some implementations, the digital analog conversion unit 211, the comparison unit 212, and the control unit 220 of the overload protection circuit 200 can be fabricated in the same chip (IC). The remaining current-to-voltage unit 240, the noise cancellation unit 250, the amplification unit 260, and/or the resonance unit 270 may be externally disposed electronic components. However, the present invention is not limited thereto, and the current-to-voltage unit 240, the noise canceling unit 250, the amplifying unit 260, and/or the resonating unit 270 may also be integrated with the digital analog converting unit 211, the comparing unit 212, and the regulating unit 220. Made in the same wafer.

Fig. 6 is a schematic view showing a method of overload protection of a piezoelectric element according to an embodiment of the present invention. Referring to FIG. 3 to FIG. 6, the overload protection method of the piezoelectric element 100 includes receiving the analog signal A1 (step S11), sequentially generating the complex control codes D1-Dn (step S12), and sequentially sampling according to the complex control codes D1-Dn. The analog signal A1 generates the sampling signal Ss (step S13), obtains the corresponding reference signal according to the control code when the sampling signal is changed (step S14), compares the potential of the reference signal with the threshold (step S15), and when the reference signal When the potential is greater than the threshold value, the output of the pulse modulation signal Sp is stopped to stop the piezoelectric element 100 (step S16a). Further, when the operating voltage is less than or equal to the critical value, the pulse modulation signal Sp is output (step S16b) to control the operating current I1 of the piezoelectric element 100.

Here, the frequency of the pulse modulation signal Sp may be a fixed frequency, such as a series resonance frequency F1 fixed to the piezoelectric element 100 to obtain a maximum mechanical energy output. Since the piezoelectric element 100 is a frequency control element, when the frequency of the pulse modulation signal Sp is a fixed frequency, the impedance of the piezoelectric element 100 can be a fixed impedance, so that the operating current I1 can be driven only by the piezoelectric element 100. The impedance of the external load.

Further, the magnitude of the analog signal A1 is related to the magnitude of the operating current I1 of the piezoelectric element 100. Here, the analog signal A1 is positively related to the operating current I1 of the piezoelectric element 100 and negatively related to the impedance of the external load.

In some embodiments, before the step S11, the overload protection method may further include generating the analog signal A1 according to the operating current I1 (step S10a). In this case, the overload protection circuit 200 can convert the corresponding analog signal A1 according to the magnitude of the operating current I1 of the piezoelectric element 100 by the current-to-voltage unit 240.

After the step S10a, the overload protection method may further include canceling the noise on the analog signal A1 by the noise cancellation unit 250 (step S10b). In addition, the overload protection method may further include amplifying the analog signal A1 by the amplifying unit 260 (step S10c). In this case, step S10b and step S10c may be sequentially performed to first cancel the noise on the analog signal A1, and then amplify the analog signal A1. However, the present invention is not limited thereto, and the overload protection method may also perform only step S10b or step S10c.

In an implementation of step S11, the overload protection circuit 200 can receive the analog signal A1 by the comparison unit 212 of the current sampling unit 210. Here, the comparison unit 212 receives the analog signal A1 with its non-inverting input.

In an implementation of step S12, the control unit 220 of the overload protection circuit 200 may sequentially generate a plurality of control codes D1-Dn in a descending order, an ascending order, or a user-defined sequence.

In an implementation of the step S13, the digital analog conversion unit 211 of the current sampling unit 210 sequentially generates the reference signals Sr1-Srn according to the control codes D1-Dn (step S13a), and the current sampling unit 210 The comparing unit 212 generates the sampling signal Ss according to each of the reference signals Sr1-Srn and the analog signal A1 (step S13b).

Here, when the comparing unit 212 determines that the analog signal A1 is greater than the reference signal compared thereto, the level of the sampling signal Ss generated by the comparing unit 212 may be logic "1". And when comparing When the unit 212 determines that the analog signal A1 is smaller than the reference signal, the bit criterion of the sampling signal Ss generated by the comparing unit 212 may be logic “0”. Further, step S11 to step S13 may be referred to as a sampling procedure.

In an implementation of the step S14, the control unit 220 of the overload protection circuit 200 can obtain the reference signal Srx generated by the digital analog conversion unit 211 according to the control code when the sampling signal Ss is in the sampling process. . Next, in step S15, the overload protection circuit 200 can compare the potential of the reference signal Srx with a preset threshold through the control unit 220.

When the result of the comparison is that the potential of the reference signal Srx is greater than the threshold value, it indicates that the variation of the external load has exceeded the stable range, and the operating current I1 flowing through the piezoelectric element 100 has exceeded the loadable range of the piezoelectric element 100 (ie, ,overload). Therefore, in step S16a, the control unit 220 of the overload protection circuit 200 can stop outputting the pulse modulation signal Sp to stop the operation of the resonance circuit 270, so that the piezoelectric element 100 can be stopped to avoid the piezoelectric element 100. Excessive operating current I1 is destroyed.

On the other hand, when the result of the comparison is that the potential of the reference signal Srx is less than or equal to the preset threshold, it indicates that the variation of the external load is still in the stable range, and the operating current I1 flowing through the piezoelectric element 100 is still in the piezoelectric state. The component 100 can be loaded within the range. Therefore, step S16b can be performed, and the control unit 220 of the overload protection circuit 200 can normally output the pulse modulation signal Sp to continue the operation of the piezoelectric element 100.

In some embodiments, after step S16b, the above-described flow steps may be performed repeatedly to resample the operating current I1 of the piezoelectric element 100, thereby immediately monitoring whether the piezoelectric element 100 is overloaded.

In some embodiments, after step S16a, the control unit 220 of the overload protection circuit 200 can further output an alert signal (not shown) to alert the user that an abnormal state has occurred.

In summary, the overload protection circuit of the piezoelectric element according to the embodiment of the present invention and the method thereof, by sampling the operating current of the piezoelectric element, can quickly react when detecting that the operating current of the piezoelectric element exceeds a critical value. The output of the pulse modulation signal is stopped to stop the piezoelectric element from being operated to avoid damage of the piezoelectric element.

The technical contents of the present invention have been disclosed in the preferred embodiments as described above, and are not intended to limit the present invention. Any modifications and refinements made by those skilled in the art without departing from the spirit of the present invention should be The scope of the invention is therefore defined by the scope of the appended claims.

100‧‧‧Piezoelectric components

110‧‧‧First drive electrode

120‧‧‧second drive electrode

200‧‧‧ drive circuit

210‧‧‧current sampling unit

211‧‧‧Digital Analog Conversion Unit

212‧‧‧Comparative unit

220‧‧‧Control unit

240‧‧‧current to voltage unit

250‧‧‧ Noise Elimination Unit

260‧‧‧Amplification unit

270‧‧‧Resonance unit

271‧‧‧Capacitive components

272‧‧‧Switch Module

273‧‧‧Inductive components

A1‧‧‧ analog signal

D1-Dn‧‧‧ control code

R2‧‧‧ resistance

Sr1-Srn‧‧‧ reference signal

Ss‧‧‧Sampling signal

Sp‧‧‧ pulse modulation signal

Vcc‧‧‧ power supply potential

Gnd‧‧‧ Ground potential

Claims (9)

An overload protection circuit for a piezoelectric element includes: a resonance unit that controls an operating current of a piezoelectric element according to a frequency of a pulse modulation signal; and a current sampling unit that sequentially samples an analog signal according to the complex control code to generate a a sampling signal, wherein the magnitude of the analog signal is related to the magnitude of the operating current of the piezoelectric element; and a control unit sequentially generates the complex control code, and the control code is obtained according to the sampling signal when the sampling signal is changed. After a reference signal, the potential of the reference signal is compared with a threshold, and when the potential of the reference signal is greater than the threshold, the output of the pulse modulation signal is stopped to stop the piezoelectric element. The overload protection circuit of the piezoelectric element according to claim 1, wherein the current sampling unit comprises: a digital analog conversion unit, generating the complex reference signal according to the complex control code; and a comparison unit, according to each of the reference signals The analog signal produces the sampled signal. The overload protection circuit of the piezoelectric element according to claim 1, wherein when the voltage of the reference signal is less than or equal to the threshold, the control unit outputs the pulse modulation signal to control the operating current of the piezoelectric element. . The overload protection circuit of the piezoelectric element according to claim 1, further comprising: a current-to-voltage unit, wherein the analog signal is generated according to the operating current of the piezoelectric element. The overload protection circuit of the piezoelectric element according to claim 1, further comprising: An amplifying unit amplifies the analog signal, wherein the current sampling unit sequentially samples the amplified analog signal according to the complex control code to generate the sampling signal. The overload protection circuit of the piezoelectric element according to claim 5, further comprising: a noise canceling unit for canceling the noise on the analog signal, wherein the amplifying unit amplifies the analog signal by using the noise canceling unit The analog signal after the noise. The overload protection circuit of the piezoelectric element of claim 1, wherein the resonant unit comprises: a capacitive element, one end coupled to one end of the piezoelectric element; and a switch module coupled to the other end of the capacitive element And the current sampling unit, and the electrical connection between the capacitive element and the current sampling unit is controlled according to the pulse modulation signal; and an inductive component coupled between the other end of the capacitive element and a power supply potential . The overload protection circuit of the piezoelectric element according to claim 7, wherein the other end of the piezoelectric element is coupled to a ground potential. The overload protection circuit of the piezoelectric element according to claim 7, wherein the other end of the piezoelectric element is coupled to the current sampling unit.