CN117958499A

CN117958499A - Signal processing method, signal processing circuit, piezoelectric sensing system and electronic cigarette

Info

Publication number: CN117958499A
Application number: CN202410158808.6A
Authority: CN
Inventors: 王志轩; 刘茂强; 李思聪; 王佳鑫; 赵勇
Original assignee: Wuxi Micronano Core Electronic Technology Co ltd
Current assignee: Wuxi Micronano Core Electronic Technology Co ltd
Priority date: 2024-02-04
Filing date: 2024-02-04
Publication date: 2024-05-03

Abstract

The application relates to a signal processing method, a signal processing circuit, a piezoelectric sensing system and an electronic cigarette, wherein the output voltage of a piezoelectric sensor is controlled to be in a preset range by responding to a force removing event generated by the piezoelectric sensor; and periodically resetting the piezoelectric sensor under the condition that the piezoelectric sensor does not generate a pressure event; the pressure event comprises that the output voltage of the piezoelectric sensor is not smaller than a voltage threshold value, so that rebound voltage can be eliminated, temperature drift influence can be restrained, and probability of false triggering of the pressure event is reduced.

Description

Signal processing method, signal processing circuit, piezoelectric sensing system and electronic cigarette

Technical Field

The application relates to the field of piezoelectric sensor signal processing, in particular to a signal processing method, a signal processing circuit, a piezoelectric sensing system and an electronic cigarette.

Background

A piezoelectric sensor, which is a sensor that converts mechanical pressure into an electrical signal, uses the characteristics of a piezoelectric material, and when an external force is applied to the surface thereof, the internal charge distribution changes, thereby generating a voltage. The piezoelectric sensor converts a physical quantity into an electrical signal, and the processing of the electrical signal requires a chip. Therefore, in practical applications, the piezoelectric sensor and the signal processing circuit are usually combined with each other, so as to enhance the function and measurement accuracy of the sensor, and better meet the requirements of different industries.

Fig. 1 is a schematic diagram of a state change of a related art piezoelectric sensor, in which fig. 1a represents a state change process of the piezoelectric sensor when the piezoelectric sensor is stressed, and fig. 1b represents a state change process of the piezoelectric sensor when the piezoelectric sensor is affected by temperature drift. Referring to fig. 1a, the piezoelectric sensor is typically a parallel plate-like capacitor structure with uniform positive and negative charges in the medium. Under the condition of no external force, the whole body presents electric neutrality, and when the sensor is stressed, the geometric centers of positive and negative charges are dislocated, so that induced charges are presented on the two polar plates. The greater the force, the greater the degree of misalignment of the geometric centers of the positive and negative charges, and the greater the amount of charge on the plate. If the sensor is subjected to pressure in the opposite direction, charges are generated as well, but the charge sign corresponding to each polar plate is changed according to the direction of the force. The piezoelectric sensor outputs voltage when the internal charge of the piezoelectric sensor changes, and the signal processing circuit judges whether a pressure event occurs according to the output voltage.

The following will cause the signal processing circuitry to erroneously determine that a pressure event has occurred:

(1) The piezoelectric sensor has a common charge leakage phenomenon, and the charge leakage can cause the piezoelectric sensor to generate rebound voltage in the process of removing force, so that the signal processing circuit can be used for erroneously judging that a pressure event occurs.

(2) Referring to fig. 1b, when the temperature of the piezoelectric sensor increases due to an increase in the ambient temperature, the piezoelectric sensor also generates an induced charge, which causes the baseline voltage of the piezoelectric sensor (the output voltage of the piezoelectric sensor when not being stressed) to rise, possibly causing the signal processing circuit to erroneously determine that a pressure event has occurred.

Aiming at the problem that the piezoelectric sensor is easy to trigger a pressure event by mistake in the related technology, no effective solution is proposed at present.

Disclosure of Invention

In view of the foregoing, it is desirable to provide a signal processing method, a signal processing circuit, a piezoelectric sensing system, and an electronic cigarette that are capable of preventing false triggering of a pressure event.

In a first aspect, the present application provides a signal processing method, including:

responding to a force removing event of the piezoelectric sensor, and controlling the output voltage of the piezoelectric sensor to be in a preset range; and

Under the condition that the piezoelectric sensor does not generate a pressure event, the piezoelectric sensor is reset periodically;

The pressure event comprises that the pressure born by the piezoelectric sensor gradually decreases from a peak value, and the pressure event comprises that the output voltage of the piezoelectric sensor is not smaller than a voltage threshold value.

In some of these embodiments, controlling the output voltage of the piezoelectric sensor to be within a preset range includes:

increasing the capacitance of the first capacitor so that the output voltage of the piezoelectric sensor decreases to not exceed the voltage threshold; and/or the number of the groups of groups,

Resetting the piezoelectric sensor and releasing the reset after maintaining the first preset time;

the first capacitor is arranged between a voltage output pin and a reference voltage input pin of the piezoelectric sensor; the first preset time is not less than a bleed time of residual charge in the piezoelectric sensor that can trigger the pressure event.

In some of these embodiments, the force-withdrawal event occurring in response to the piezoelectric sensor comprises:

detecting an output voltage of the piezoelectric sensor;

When the output voltage of the piezoelectric sensor is detected to be converted from a first voltage area to a second voltage area, judging that the piezoelectric sensor generates a force removing event;

Wherein the voltage in the first voltage region is not less than the voltage threshold, and the voltage in the second voltage region is less than the voltage threshold.

In some embodiments, the reset period of the periodic reset is less than a second preset time, where the second preset time is a time required for the piezoelectric sensor to ramp up from a baseline voltage to the voltage threshold due to a temperature drift effect when the piezoelectric sensor is not under pressure.

In some of these embodiments, the reset period of the periodic reset is greater than the rising edge time and/or falling edge time of the output voltage when the piezoelectric sensor experiences a pressure event.

In some of these embodiments, in the event that a pressure event does not occur with the piezoelectric sensor, periodically resetting the piezoelectric sensor includes:

and if the output voltage of the piezoelectric sensor is detected to be smaller than the voltage threshold value, the piezoelectric sensor is reset periodically.

In some of these embodiments, the method further comprises: and if the output voltage of the piezoelectric sensor is detected not to be smaller than the voltage threshold value, stopping periodic resetting of the piezoelectric sensor.

In some of these embodiments, controlling the output voltage of the piezoelectric sensor to be within a preset range includes: increasing the capacitance of the first capacitor so that the output voltage of the piezoelectric sensor decreases to not exceed the voltage threshold; the first capacitor is arranged between a voltage output pin and a reference voltage input pin of the piezoelectric sensor; after suspending the periodic reset of the piezoelectric sensor, the method further comprises: reducing the capacitance of the first capacitor.

In a second aspect, the present application provides a signal processing circuit comprising:

A control module for executing the signal processing method described in the first aspect;

The controlled module is connected with the control module and can respond to the control signal output by the control module, and the output voltage of the piezoelectric sensor is in a preset range by switching the working state.

In some of these embodiments, the control module comprises: a comparison unit and a logic unit; the input end of the comparison unit is connected with the voltage output pin of the piezoelectric sensor, the output end of the comparison unit is connected with the input end of the logic unit, and the output end of the logic unit is connected with the controlled module; wherein,

The comparison unit is used for comparing the output voltage of the piezoelectric sensor with a voltage threshold value to obtain a comparison result;

The logic unit is used for outputting the control signal according to the comparison result and sending the control signal to the controlled module.

In some of these embodiments, the controlled module comprises: a first capacitor; the first capacitor is arranged between a voltage output pin and a reference voltage input pin of the piezoelectric sensor; the working state of the first capacitor comprises increasing the capacitance value or recovering to the initial capacitance value.

In some of these embodiments, the controlled module comprises: a reset switch; the first end of the reset switch is connected with a voltage output pin of the piezoelectric sensor, the second end of the reset switch is connected with a reference voltage input pin of the piezoelectric sensor, and the third end of the reset switch is connected with the output end of the control module; wherein,

The working state of the reset switch comprises that the first end of the reset switch is connected with the second end or the third end.

In a third aspect, the present application provides a piezoelectric sensing system comprising: a piezoelectric sensor and the signal processing circuit according to the second aspect, wherein the piezoelectric sensor is connected with the signal processing circuit.

In a fourth aspect, the present application provides an electronic cigarette, comprising: the main body is provided with a piezoelectric sensor and the signal processing circuit of the second aspect, and the piezoelectric sensor is connected with the signal processing circuit.

According to the signal processing method, the signal processing circuit, the piezoelectric sensing system and the electronic cigarette, when a force removing event occurs, the output voltage of the piezoelectric sensor is controlled to be in the preset range, and when a pressure event does not occur, the piezoelectric sensor is reset periodically, so that the rebound voltage can be eliminated, the temperature drift influence can be restrained, and the probability of false triggering of the pressure event is reduced.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below to provide a more thorough understanding of the other features, objects, and advantages of the application.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments or the conventional techniques of the present application, the drawings required for the descriptions of the embodiments or the conventional techniques will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.

FIG. 1a is a schematic diagram of a state change of a piezoelectric sensor according to the related art when the piezoelectric sensor is stressed;

FIG. 1b is a schematic diagram showing a state change of a piezoelectric sensor in the related art when temperature drift occurs;

FIG. 2 is a schematic diagram of an equivalent circuit of a piezoelectric sensor;

FIG. 3 is a schematic diagram of a response curve of a piezoelectric sensor;

FIG. 4 is a second schematic diagram of a response curve of a piezoelectric sensor in one embodiment;

FIG. 5 is a flow diagram of a method of signal processing in one embodiment;

FIG. 6 is an effect diagram of a signal processing method in one embodiment;

FIG. 7 is a schematic diagram of the detection principle of a force-withdrawal event in one embodiment;

FIG. 8 is a flow chart of a signal processing method in another embodiment;

FIG. 9 is an architecture diagram of signal processing circuitry in one embodiment;

FIG. 10 is a schematic diagram of the architecture of a signal processing circuit in one embodiment;

Fig. 11 is a schematic diagram of a signal processing circuit in another embodiment.

Reference numerals illustrate: 1. a signal processing circuit; 11. a control module; 111. a comparison unit; 11a, a first comparator; 11b, a second comparator; 112. a logic unit; 12. a controlled module; cn, first capacitance; K. a reset switch; 13. a first pin; 14. a second pin; 15. a third pin; 16. an amplifying unit; 17. a voltage generation module; q, a charge source; cp, a second capacitor; rp, resistance; MEMS, piezoelectric sensor; voltage output pins of the Vout and piezoelectric sensors; vref, reference voltage input pin of the piezoelectric sensor.

Detailed Description

In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Embodiments of the application are illustrated in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

It will be understood that the terms first, second, etc. as used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element. For example, a first resistance may be referred to as a second resistance, and similarly, a second resistance may be referred to as a first resistance, without departing from the scope of the application. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

It is to be understood that in the following embodiments, "connected" is understood to mean "electrically connected", "communicatively connected", etc., if the connected circuits, modules, units, etc., have electrical or data transfer between them.

It is understood that "at least one" means one or more and "a plurality" means two or more. "at least part of an element" means part or all of the element.

As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," and/or the like, specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof. Also, the term "and/or" as used in this specification includes any and all combinations of the associated listed items.

Fig. 2 is a schematic diagram of an equivalent circuit of a piezoelectric sensor. As shown in fig. 2, in which MEMS represents a piezoelectric sensor, which may be equivalently referred to as a charge source q, a second capacitor Cp, and a resistor Rp are connected in parallel with each other, vout represents an output voltage of the piezoelectric sensor, and Vref represents a reference voltage of the piezoelectric sensor. When the plate is pressed, the charge source q generates a charge and stores the charge in the second capacitor Cp, forming a voltage difference of Vout-vref=q/Cp, however, due to the resistor Rp, the charge on the second capacitor Cp leaks slowly through Rp, resulting in a decrease in the charge amount on the second capacitor Cp, and thus the value of Vout-Vref decreases until vout=vref, where the charge is 0.

Fig. 3 is a schematic diagram of a response curve of a piezoelectric sensor. As shown in fig. 3, in the front section of the curve, when a reverse pressure is applied to the piezoelectric sensor (e.g., the lower plate of fig. 1a is forced), an electrical charge is generated on the plate, creating a voltage; as the force increases, the amount of charge increases and the output voltage Vout increases. The output voltage Vout peaks when the force just changes from increasing to remaining unchanged. Subsequently, the output voltage Vout slowly decreases due to the aforementioned charge leakage. If the "force-withdrawing process" occurs before the charge is completely leaked, the charges with opposite signs are generated inside the piezoelectric sensor, so that the charges generated in the "force-withdrawing process" are counteracted, and the steep force-withdrawing edge and the rebound voltage are shown on the output voltage. The rebound voltage is a voltage formed by the residual charge on the second capacitor Cp after the residual charge generated by the "force removing process" and the residual charge generated by the "force removing process start time" have been cancelled. With the slow leakage of the residual charge, the rebound voltage is gradually restored to the baseline potential (the schematic is shown as 0 potential for convenience).

In the middle section of the curve, the temperature of the surrounding environment of the piezoelectric sensor rises due to heating of the power device or charging of the device. When the temperature rises, the output voltage Vout also shifts in the increasing direction due to the additional charge generated by the piezoelectric sensor, resulting in a rise in the baseline voltage, i.e., a temperature drift voltage.

In the latter section of the curve, if the piezoelectric sensor receives an external pressure (for example, applies a force to the upper plate in fig. 1 a) during the temperature rising process, an output voltage increment caused by the pressure will be superimposed on the temperature drift voltage, which easily causes misjudgment when the subsequent signal processing circuit processes the signal. The back section of the curve shows the situation of forward force application, and similar to the front section of the curve, the process of forward force application, charge leakage, force removal, rebound voltage and rebound voltage recovery is successively carried out. Finally, due to the charge leakage principle, the extra charge caused by temperature drift also leaks slowly, so that the temperature drift voltage falls back to the baseline voltage.

Normally (irrespective of the rebound voltage and temperature drift effects), a pressure event means that the output voltage of the piezoelectric sensor is not less than the voltage threshold. Whether the positive pressure event or the negative pressure event is judged, whether the output voltage is larger than a voltage threshold value or not is only needed to be detected, and if so, the pressure event is judged to occur. The voltage threshold determination herein refers to comparing the voltage amplitude, regardless of the direction. As for the direction of application of force, it can be determined by comparing the magnitude of the output voltage with the baseline voltage.

To further reveal the effect of the characteristics of the piezoelectric sensor, FIG. 4 shows a second response curve of the piezoelectric sensor. As shown in fig. 4, V1 represents a first threshold voltage (amplitude equal to a voltage threshold). If the output voltage of the piezoelectric sensor is detected to be greater than the first threshold voltage V1, a pressure event is triggered. However, there are two situations that may cause misjudgment. First, if the amplitude of the rebound voltage generated by the reverse pressure event in the force removing process exceeds the judgment threshold value of the forward pressure event, the forward pressure event is mistakenly considered to occur. Secondly, if the temperature drift voltage caused by the temperature change is greater than the threshold value, the occurrence of an event is also mistakenly considered. It can be seen that the rebound voltage and the temperature excursion voltage are the main causes of the false triggering pressure event.

In view of the above problems, the related art provides a solution that an analog-to-digital conversion circuit is used to convert the output voltage of the piezoelectric sensor into a digital signal, and then a digital signal processing circuit is used to identify the digitized "rebound voltage" and "temperature drift voltage", so as to prevent misjudgment and correctly perform pressure event judgment. The main problem of this scheme is that, on the one hand, the analog-to-digital conversion circuit is relatively complex, and the circuit area overhead and the power consumption overhead are both large, resulting in high design and use costs. On the other hand, in order to match with the analog-digital conversion circuit, the digital signal processing circuit connected with the analog-digital conversion circuit is complex, and the design and use cost are also brought.

Based on the above analysis, in one embodiment, a signal processing method is provided. Fig. 5 is a flowchart of the signal processing method of the present embodiment, and as shown in fig. 5, the flowchart includes the steps of:

In step S501, in response to a force-removing event occurring in the piezoelectric sensor, an output voltage of the piezoelectric sensor is controlled to be within a preset range.

The force-removing event includes the gradual decrease of the pressure applied by the piezoelectric sensor from the peak value. When the pressure applied by the piezoelectric sensor is detected to gradually decrease from the peak value, a force withdrawal event is considered to be possible. The preset range refers to a voltage range in which the output voltage of the piezoelectric sensor cannot trigger a pressure event by mistake under the condition of no stress.

In step S502, the piezoelectric sensor is periodically reset in the case where the piezoelectric sensor does not have a pressure event.

A pressure event includes an output voltage of the piezoelectric sensor not being less than a voltage threshold. When the output voltage of the piezoelectric sensor is detected not to be smaller than the voltage threshold value, the output voltage represents that the increment caused by the pressure exists in the output voltage, and the pressure event is considered to exist possibly. The piezoelectric sensor is reset, namely the voltage output pin of the piezoelectric sensor and the reference voltage input pin are short-circuited, namely Vout=Vref is forced, and the charge of the piezoelectric sensor is discharged, so that the function of recovering the baseline voltage is achieved.

In the above-mentioned steps S501 to S502, on the one hand, considering that the rebound voltage occurs following the force-removing event, when the force-removing event is detected, the output voltage of the piezoelectric sensor is immediately controlled to be in the preset range, so as to reduce the rebound voltage, thereby avoiding false triggering of the pressure event due to the rebound voltage. On the other hand, in the case that the pressure event is not detected, the piezoelectric sensor is periodically reset to inhibit the baseline voltage from rising, so that the pressure event is prevented from being triggered by mistake due to the influence of temperature drift.

To further disclose the effect of the signal processing method, fig. 6 shows a schematic diagram of the effect of the signal processing method. Referring to fig. 6, V1 represents a first threshold voltage for detecting a forward pressure event; v2 represents a second threshold voltage for detecting a reverse pressure event; the first threshold voltage V1 and the second threshold voltage V2 are equal in magnitude and opposite in direction. T represents a reset period of the periodic reset. Fig. 6 shows MEMS response curves for 4 different signal processing stages, respectively. The process of switching from the MEMS response curve 1 to the MEMS response curve 2 and then to the MEMS response curve 3 represents that the output voltage of the piezoelectric sensor is controlled to be in a preset range in response to the force withdrawal event occurring by the piezoelectric sensor, and the process of switching from the MEMS response curve 3 to the MEMS response curve 4 represents that the piezoelectric sensor is periodically reset under the condition that the piezoelectric sensor does not have the pressure event. And the reset piezoelectric sensor is reset again and quickly after every reset period T, and the reset piezoelectric sensor is reset repeatedly until the next reset period T, so that the temperature drift voltage is reset before exceeding the first threshold voltage V1, and misjudgment caused by the temperature drift voltage exceeding the first threshold voltage V1 is avoided.

It should be understood that, although the steps in fig. 5 are shown in sequence as indicated by arrows, the steps are not necessarily performed in sequence as indicated by the arrows. Similarly, although the respective MEMS response curves in fig. 6 are sequentially displayed as indicated by arrows, this does not represent that the respective signal processing methods are necessarily sequentially performed in the order indicated by the arrows. The steps in fig. 5 may be performed in other orders and the MEMS response curves in fig. 6 may be displayed in other orders. For example, if the piezoelectric sensor is detected to have no pressure event, the piezoelectric sensor is reset periodically; and when the piezoelectric sensor generates a force removing event, controlling the output voltage of the piezoelectric sensor to be in a preset range. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least a portion of the steps in the flowcharts may include a plurality of steps or stages that are not necessarily performed at the same time, but may be performed at different times, and the order of execution of the steps or stages is not necessarily sequential, but may be performed in rotation or alternately with at least a portion of the steps or stages in other steps or other steps.

In some embodiments, referring to the signal processing circuit shown in fig. 10 or 11, step S501 may be implemented in the following manner.

Scheme 1: dynamic capacitance switching. A first capacitor Cn is arranged between the voltage output pin Vout of the piezoelectric sensor and the reference voltage input pin Vref, such that the first capacitor Cn is connected in parallel with a second capacitor Cp (the internal capacitor of the piezoelectric sensor), wherein the capacitance value of the first capacitor Cn is adjustable. At this time, the output voltage vout=q/(cp+cn) of the piezoelectric sensor. When a force withdrawal event is detected, the output voltage of the piezoelectric sensor can be reduced to a value not exceeding the voltage threshold by increasing the capacitance value of the first capacitance Cn. Further, after the first capacitor Cn is increased and maintained for the first preset time, the capacitance value of the first capacitor Cn is reduced, so that the first capacitor Cn is restored to the initial value, and the rebound voltage can be better eliminated. The first preset time is not less than the release time of residual charges in the piezoelectric sensor, wherein the residual charges can trigger a pressure event.

Scheme 2: and (5) force removal and resetting. A reset switch K is provided between the voltage output pin Vout of the piezoelectric sensor and the reference voltage input pin Vref. When a force removal event is detected, the piezoelectric sensor is in a reset state by closing the reset switch K, and the second capacitor Cp starts to discharge charges, so that the rebound voltage is reduced. The longer the reset switch K is closed, the more charge is drained. In order to drain all residual charges as much as possible, the reset switch K is turned on and turned off after a first preset time. The first preset time is not less than the release time of residual charges in the piezoelectric sensor, wherein the residual charges can trigger a pressure event.

Scheme 3: dynamic capacitance switching + force-withdrawal reset. Meanwhile, a first capacitor Cn and a reset switch K are arranged between a voltage output pin Vout and a reference voltage input pin Vref of the piezoelectric sensor, so that the piezoelectric sensor is in a reset state when the reset switch K is closed. When the force-withdrawal event is detected, the peak value of the rebound voltage can be reduced by increasing the first capacitor Cn, and then the reset switch K is closed and maintained for a first preset time before being opened. Therefore, the time period that the rebound voltage is higher than the voltage threshold value is reduced, so that the design range of the first preset time for the force removal reset is wider, and reset can not occur when the output voltage of the piezoelectric sensor rises/falls due to the fact that the first preset time is too short, and the normal functions of the piezoelectric sensor are affected. In addition, the capacity of the capacitor is in direct proportion to the area of the capacitor plate, but due to the introduction of force-removing reset, the first capacitor Cn can meet the residual charge discharging requirement without increasing to a particularly large capacity value, and the circuit space is saved.

In one embodiment, a method of determining a withdrawal event is provided. Detecting the output voltage of the piezoelectric sensor; when the output voltage of the piezoelectric sensor is detected to be converted from a first voltage area to a second voltage area, judging that the piezoelectric sensor generates a force removing event; the voltage of the first voltage area is not smaller than the voltage threshold value, and the voltage of the second voltage area is smaller than the voltage threshold value.

FIG. 7 is a schematic diagram of the detection principle of the force-removing event, as shown in FIG. 7, V1 represents a first threshold voltage for detecting the positive pressure event; v2 represents a second threshold voltage for detecting a reverse pressure event; the first threshold voltage V1 and the second threshold voltage V2 are equal in magnitude and opposite in direction. The first threshold voltage V1 and above is defined as a region a, the second threshold voltage V2 and below is defined as a region C, and both the region a and the region C belong to the first voltage region. The portion between the first threshold voltage V1 and the second threshold voltage V2 is defined as a region B, and the region B is the second voltage region. A force withdrawal event may be considered to occur when it is detected that the output voltage of the piezoelectric sensor exhibits a transition from a first voltage region (region a or region C) to a second voltage region (region B). For example, for a forward pressure event, the process of Vout exceeding V1 is considered to be forced, and the process of Vout changing from greater than V1 to less than V1 is considered to be de-forced. Similarly, the reverse pressure event can also be determined by the process of Vout going up and down over V2 to determine whether force is applied or removed.

It should be noted that, in the above embodiment, the threshold voltage (V1 or V2) is used to determine the force application and the force removal. In practice, the force application and the force removal can be determined by two different threshold voltages, respectively. For example, V1 is used to determine the forward pressure force, V1 'is used to determine the withdrawal force, V2 is used to determine the reverse pressure force, and V2' is used to determine the withdrawal force. The present application is exemplified by a threshold voltage for convenience of description.

In one embodiment, referring to the signal processing circuit shown in fig. 10 or 11, step S502 may be implemented as follows.

Scheme 4: and periodically resetting. A reset switch K is provided between the voltage output pin Vout of the piezoelectric sensor and the reference voltage input pin Vref. If the output voltage of the piezoelectric sensor is detected to be smaller than the voltage threshold, the voltage output pin Vout of the piezoelectric sensor is short-circuited with the reference voltage input pin Vref by closing the reset switch K, namely Vout=Vref is forced, and the charge of the piezoelectric sensor is discharged, so that the function of recovering the baseline voltage is achieved. Further, the closing time of the reset switch K may also be according to the design concept of the force-removing reset time, that is, the reset switch K may be opened after being closed and maintained for the first preset time. The first preset time is not less than the release time of residual charges in the piezoelectric sensor, wherein the residual charges can trigger a pressure event.

Regarding the reset period, it can be designed based on the magnitude of the temperature drift, with the purpose that the voltage change caused by the temperature drift does not cause false triggering of the pressure event during two adjacent reset time intervals. With continued reference to fig. 3, in the back section of the curve, when the temperature rises to a certain value and remains unchanged, the temperature drift of the voltage slowly falls back due to the charge leakage principle described above. This means that the temperature drift of the piezoelectric sensor output voltage is independent of the absolute value of the temperature and is only dependent on the rate of temperature change.

Based on the above analysis, in one embodiment, the reset period of the periodic reset is less than a second preset time, where the second preset time is a time required for the piezoelectric sensor to ramp up the output voltage from the baseline voltage to the voltage threshold due to the temperature drift effect when the piezoelectric sensor is not under pressure. For convenience of description, the baseline voltage that is raised due to the temperature drift effect is defined as the temperature drift voltage. By the arrangement, the piezoelectric sensor can be reset before the temperature drift voltage rises to the voltage threshold value, and the false triggering of the pressure event is avoided in time. The temperature drift voltage climbing time can be obtained through experimental tests, and can also be obtained through calculation of corresponding parameters. For example, a change rate of a temperature drift voltage of the piezoelectric sensor and a baseline voltage are obtained, wherein the change rate of the temperature drift voltage is a rate of change of an output voltage of the piezoelectric sensor due to a temperature drift effect; and determining preset time according to the change rate of the temperature drift voltage, the voltage threshold value and the baseline voltage. Specifically, the second preset time= (voltage threshold-baseline voltage)/rate of change of temperature drift voltage. The change rate of the temperature drift voltage is related to the current temperature change rate, and the change rate of the temperature drift voltage can be calculated based on the current temperature by acquiring the association relation between the temperature drift voltage and the temperature.

In order that the voltage change caused by temperature drift does not cause false triggering of the pressure event in two adjacent reset time intervals, the shorter the reset period should be, the better. However, too short a reset period may result in resetting in the event of a force being applied or removed, i.e., a falling edge of the piezoelectric sensor output voltage, which may affect the proper functioning of the piezoelectric sensor. With continued reference to fig. 3, it should be noted that the additional charge generation rate of the piezoelectric sensor due to temperature rise is much slower than the charge generation rate of the piezoelectric sensor when the piezoelectric sensor is under pressure, in other words, the rising edge and the falling edge of the output voltage of the piezoelectric sensor due to force application and force withdrawal are much steeper than the rising slope of the output voltage due to temperature rise.

Based on the above analysis, in some embodiments, the reset period may be determined based on a rising edge time and/or a falling edge time of the output voltage when the piezoelectric sensor experiences a pressure event. With continued reference to fig. 6, T1 represents a rising edge time, which refers to a time when the output voltage starts from the baseline voltage because the pressure rises to a peak when the pressure is applied; t2 represents the falling edge time, which refers to the time at which the output voltage drops to the baseline voltage with a steeper slope when the pressure is removed.

In one embodiment, the reset period is greater than the rising edge time of the output voltage when the piezoelectric sensor experiences a pressure event, avoiding erroneous resets when pressure is applied.

In one embodiment, the reset period is greater than the falling edge time of the output voltage when the piezoelectric sensor experiences a pressure event, avoiding erroneous resets when the pressure is removed.

In one embodiment, the reset period is greater than the maximum of the rising edge time and falling edge time of the output voltage when the piezoelectric sensor experiences a pressure event, avoiding erroneous resets when pressure is applied or removed.

In one embodiment, the reset period is greater than a rising edge time or a falling edge time of the output voltage when the piezoelectric sensor is subjected to a pressure event, and the reset period is less than a second preset time, avoiding erroneous resetting when the pressure is applied or removed, and avoiding false triggering of the pressure event.

In one embodiment, the reset period is greater than a maximum of a rising edge time and a falling edge time of the output voltage when the piezoelectric sensor is subjected to the pressure event, and the reset period is less than a second preset time, avoiding erroneous resetting when the pressure is applied or removed, and avoiding false triggering of the pressure event.

In one embodiment, combining one of the schemes of step S501 with step S502 may result in scheme 5: dynamic capacitive switching + periodic reset. Meanwhile, a first capacitor Cn and a reset switch K are arranged between a voltage output pin Vout and a reference voltage input pin Vref of the piezoelectric sensor, so that the first capacitor Cn and a second capacitor Cp are connected in parallel, and when the reset switch K is closed, the piezoelectric sensor is in a reset state. The first capacitor Cn has two working states, namely a large capacitor and a small capacitor. Under the condition that the pressure event is not detected, the first capacitor Cn can be switched to a working state of a large capacitor, so that a voltage slope caused by temperature drift is slowed down, and then periodic reset is performed to eliminate extra charges caused by temperature drift.

In combination with the design principle above regarding the reset period, since the first capacitance Cn is at a larger value in the scenario of scheme 5, the temperature drift voltage will also decrease because vout=q/(cp+cn). On one hand, the temperature drift voltage is more difficult to exceed V1, so that misjudgment is avoided with higher probability; on the other hand, this also makes the reset period design range wider (i.e., the reset period upper limit becomes high), and the temperature drift voltage does not exceed V1 even if the reset period interval is made longer. Further, the longer the reset period is, the less likely the output voltage is erroneously reset at a stage where the rise of the output voltage does not exceed V1 during the biasing.

In one embodiment, when step S502 is performed, if it is detected that the output voltage of the piezoelectric sensor is not less than the voltage threshold, the periodic reset of the piezoelectric sensor is aborted. I.e. the periodic reset continues until the next pressure event forcing process is detected, in order not to affect the decision of a normal pressure event.

In one embodiment, referring to the signal processing circuit shown in fig. 10 or 11, fig. 8 shows a flowchart of another signal processing method, as shown in fig. 8, the flowchart includes the steps of:

Step S801, judging whether a force withdrawal event is detected; if yes, go to step S802; if not, stay at the current step;

step S802, increasing a first capacitor Cn;

Step S803, resetting the piezoelectric sensor, and releasing the resetting after maintaining the first preset time;

Step S804, periodically resetting the piezoelectric sensor;

step S805, judging whether a force application event is detected; if yes, go to step S806; if not, returning to the step S804;

Step S806, suspending periodic reset of the piezoelectric sensor;

Step S807, decreasing the first capacitance Cn; the process goes to step S801.

The above steps may be performed in a loop.

In connection with fig. 6 and 8, taking the detected force withdrawal event as a flow starting point, the bounce voltage is reduced by increasing the first capacitor Cn, i.e. switching it to the working state of the large capacitor, which shortens the duration of the bounce voltage exceeding the voltage threshold.

Next, the reset switch K is controlled to be closed, and charges in the first capacitor Cn and the second capacitor Cp are rapidly discharged. Since the piezoelectric sensor continuously generates charges during the force removal process, the reset process needs to be maintained for a first preset time, which is longer than the duration that the rebound voltage exceeds V1, so as to ensure that the charges continuously generated during the force removal process of the piezoelectric sensor do not cause the rebound voltage of the piezoelectric sensor to exceed V1 again. Since the duration of the rebound voltage exceeding V1 has been reduced by increasing the first capacitance Cn in step S802, the design range of the duration of the force-withdrawal reset becomes larger.

The reset switch K is then controlled to be closed periodically, i.e. every one cycle, the reset switch K is closed and then rapidly opened until the next cycle. The temperature drift voltage is reset before exceeding V1, so that misjudgment caused by exceeding V1 by the temperature drift voltage is avoided. In combination with the above design principle about the reset period, since the first capacitor Cn is at a larger value in this process, the temperature drift voltage is also reduced due to vout=q/(cp+cn). On one hand, the temperature drift voltage is more difficult to exceed V1, so that misjudgment is avoided with higher probability; on the other hand, this also makes the reset period design range wider (i.e., the reset period upper limit becomes high), and the temperature drift voltage does not exceed V1 even if the reset period interval is made longer. Further, the longer the reset period is, the less likely the output voltage is erroneously reset at a stage where the rise of the output voltage during the biasing has not exceeded V1.

The periodic reset is continued until the next time the force application process of the pressure event is detected; while decreasing the first capacitance Cn, returning to the initial state and still based on the vout=q/(cp+cn) principle, this makes the voltage increase caused by the pressure event larger.

According to the embodiment, the force-removing reset duration and the reset period are enabled to be wider by combining dynamic change of the capacitance value and capacitance charge discharging reset, so that the signal processing method has wider application scenes and piezoelectric sensor types.

In one embodiment, a signal processing circuit is provided for implementing the signal processing of the above embodiments. Fig. 9 is a block diagram of a signal processing circuit of the present embodiment, and as shown in fig. 9, the signal processing circuit 1 includes: a control module 11 and a controlled module 12; the control module 11 is connected to the controlled module 12. Wherein the control module 11 is configured to perform the signal processing method of any of the above embodiments; the controlled module 12 can make the output voltage of the piezoelectric sensor be in a preset range by switching the working state in response to the control signal output by the control module 11.

The signal processing circuit of the embodiment can perform post-processing on the output voltage of the piezoelectric sensor on one hand so as to meet the actual application requirements. On the other hand, in the process of executing the signal processing method, the signal processing circuit controls the output voltage of the piezoelectric sensor to be in a preset range when a force removing event occurs, and periodically resets the piezoelectric sensor (which is equivalent to controlling the output voltage of the piezoelectric sensor to be in the preset range) when a pressure event does not occur, so that the rebound voltage can be eliminated, the temperature drift influence can be restrained, and the probability of false triggering of the pressure event can be reduced. Reference may be made to the above embodiments for further principles and effects of the signal processing method, which are not described here again.

In one embodiment, fig. 10 shows a schematic diagram of the structure of the signal processing circuit. As shown in fig. 10, the control module 11 includes a comparison unit 111 and a logic unit 112, and the controlled module 12 includes a first capacitor Cn and a reset switch K. The input end of the comparison unit 111 is connected with a voltage output pin Vout of the piezoelectric sensor, the output end of the comparison unit 111 is connected with the input end of the logic unit 112, and the output end of the logic unit 112 is respectively connected with the first capacitor Cn and the reset switch K. The first capacitor Cn is arranged between the voltage output pin Vout of the piezoelectric sensor and the reference voltage input pin Vref; the first end of the reset switch K is connected with the voltage output pin Vout of the piezoelectric sensor, the second end of the reset switch K is connected with the reference voltage input pin Vref of the piezoelectric sensor, and the third end of the reset switch K is connected with the output end of the logic unit 112. The comparing unit 111 is configured to compare an output voltage of the piezoelectric sensor with a voltage threshold value to obtain a comparison result; the logic unit 112 is configured to output a control signal according to the comparison result, and send the control signal to the first capacitor Cn and/or the reset switch K. The working state of the first capacitor Cn comprises increasing the capacitance value or restoring to the initial capacitance value; the working state of the reset switch K comprises that the first end of the reset switch K is connected with the second end or the third end. Alternatively, logic 112 may be implemented using any one or more combinations of flip-flops, AND gates, NOT gates, OR gates.

The control signal includes a first signal and a second signal. Wherein the first signal is used to control the first capacitance Cn, for example to increase the capacitance value or to restore the initial capacitance value. The second signal is used to control a reset switch K, for example a short reset or a periodic reset.

In conjunction with fig. 6 and 8, taking the detection of the force withdrawal event by the comparing unit 111 and the logic unit 112 as a flow start point, the logic unit 112 increases the first capacitor Cn, i.e. switches it to the working state of the large capacitor, to reduce the rebound voltage, which shortens the duration of the rebound voltage exceeding the voltage threshold.

Next, the logic unit 112 controls the reset switch K to be closed, and rapidly discharges the charges in the first capacitor Cn and the second capacitor Cp. Since the piezoelectric sensor continuously generates charges during the force removal process, the reset process needs to be maintained for a first preset time, which is longer than the duration that the rebound voltage exceeds V1, so as to ensure that the charges continuously generated during the force removal process of the piezoelectric sensor do not cause the rebound voltage of the piezoelectric sensor to exceed V1 again. Since the duration of the rebound voltage exceeding V1 has been reduced by increasing the first capacitance Cn in step S802, the design range of the duration of the force-withdrawal reset becomes larger.

Next, the logic unit 112 periodically controls the reset switch K to be closed, i.e. every one period, the reset switch K is closed and then the switch is rapidly opened until the next period, and the cycle is repeated. The temperature drift voltage is reset before exceeding V1, so that misjudgment caused by exceeding V1 by the temperature drift voltage is avoided. In combination with the above design principle about the reset period, since the first capacitor Cn is at a larger value in this process, the temperature drift voltage is also reduced due to vout=q/(cp+cn). On one hand, the temperature drift voltage is more difficult to exceed V1, so that misjudgment is avoided with higher probability; on the other hand, this also makes the reset period design range wider (i.e., the reset period upper limit becomes high), and the temperature drift voltage does not exceed V1 even if the reset period interval is made longer. Further, the longer the reset period is, the less likely the output voltage rises during the application of the force does not exceed V1, and the periodic reset is erroneously reset.

The periodic reset is continued until the next time the force application process of the pressure event is detected; the logic unit 112 simultaneously controls the first capacitance Cn to decrease, return to the initial state, and still be based on vout=q/(cp+cn) principle, which makes the voltage increase caused by the pressure event larger.

Optionally, the signal processing circuit 1 further comprises a first pin 13, a second pin 14, and a third pin 15. The first pin 13 is used for being connected with a voltage output pin Vout of the piezoelectric sensor, the second pin 14 is used for being connected with a reference voltage input pin Vref of the piezoelectric sensor, the third pin 15 is used as a signal output end of the whole signal processing circuit, and the meaning represented by the output signal is determined by application requirements.

Alternatively, the signal processing circuit 1 may also be provided with an amplifying unit 16 and a voltage generating module 17. The amplifying unit 16 is connected between the first pin 14 and the comparing unit 111 for amplifying the output voltage of the piezoelectric sensor and improving the driving capability. The amplifying unit 16 may be implemented with a buffer amplifier, a single-ended amplifier, a differential amplifier, or a programmable gain amplifier. The voltage generating module 17 is connected to the second pin 14 and is responsible for providing a dc bias to the piezoelectric sensor. The voltage generating module 17 can be selected and removed according to the application requirement, and at this time, the reference voltage input pin Vref of the piezoelectric sensor can be grounded according to the application requirement.

In fig. 10, a comparison unit 111 is used to determine the forward pressure event and the reverse pressure event. In some of these embodiments, two comparators may be designed to determine the forward pressure event and the reverse pressure event. Fig. 11 shows a schematic diagram of another signal processing circuit, as shown in fig. 11, and on the basis of fig. 10, the comparing unit 11 includes a first comparator 11a and a second comparator 11b, wherein the first comparator 11a is used for judging the forward pressure force application and the reverse pressure force application, and the second comparator 11b is used for judging the reverse pressure force application and the reverse pressure force application.

In addition, the piezoelectric sensor of the above embodiment is single-ended, and in practical application, a piezoelectric sensor with differential output at both ends may occur, and for this case, the circuit configuration of fig. 10 or 11 need only be changed to a circuit for processing differential signals.

In addition, the signal processing circuit provided by the embodiment can be integrated into a chip, the hardware area cost and the power consumption cost are fully considered, the misjudgment influence caused by the rebound voltage and the temperature drift voltage of the piezoelectric sensor can be eliminated with the smaller circuit area cost and the smaller power consumption cost, the use of an analog-digital conversion circuit is avoided, and the design of a complex digital signal processing circuit is also avoided. It will be appreciated that the above-described signal processing circuit may take other forms, not limited to the forms already mentioned in the above-described embodiments, as long as it can achieve the rebound voltage elimination and temperature drift suppression functions.

In one embodiment, a piezoelectric sensing system is provided that includes a piezoelectric sensor and a signal processing circuit, the piezoelectric sensor being coupled to the signal processing circuit. The piezoelectric sensor converts the physical quantity into an electrical signal, and the processing of the electrical signal can be accomplished by a signal processing circuit. The signal processing circuit can reduce rebound voltage and periodically reset the piezoelectric sensor to inhibit baseline voltage from rising, so that false triggering of pressure event is avoided, and the reliability of the piezoelectric sensing system is improved. The piezoelectric sensing system can be widely applied to various fields, including but not limited to: industrial automation, piezoelectric sensors can be used to measure the execution dynamics of the robot terminal actuators to ensure that they operate accurately; the medical equipment, the piezoelectric sensor can be used for measuring physiological parameters such as blood pressure, respiratory rate, heartbeat rate and the like; the piezoelectric sensor can be used for measuring the weight and pressure distribution of the vehicle in the automobile industry, providing data support for the design of the vehicle and monitoring the systems such as an air bag, a brake and the like; air quality detection, piezoelectric sensors can be used to measure pressure and humidity in the air, thereby helping to detect harmful gases in the air; the piezoelectric sensor can be used for monitoring the structural safety and stability of a building and measuring the vibration conditions of structures such as bridges, tunnels and the like; consumer electronics, such as electronic cigarettes, piezoelectric sensors may be used to detect a smoking or blowing action, triggering a function switch of the electronic cigarette.

In one embodiment, an electronic cigarette is provided that includes a body configured with a piezoelectric sensor, the body further configured with the signal processing circuit described above, or integrated with a chip including the signal processing circuit described above, or configured with the piezoelectric sensing system described above. Optionally, the main body further comprises a PCB motherboard, and the piezoelectric sensor is disposed on the PCB motherboard.

The influence of temperature drift is mainly reflected when the temperature rate changes greatly. Since the volume of an electronic cigarette is generally small, the capacity of its battery is also generally limited. When the electronic cigarette is charged, the charging can be completed within about 3 minutes. Under the charging scene, the PCB main board heats and conducts heat to the piezoelectric sensor, so that the temperature rise of about 3min can reach 30-40 ℃. The temperature drift effect is particularly obvious at such a large rate of temperature change, and therefore, the probability of the electronic cigarette being misfiring/activation/ignition is also high.

Compared with other schemes for solving the problem by improving external conditions (such as improving heat dissipation performance), the electronic cigarette provided by the embodiment can effectively inhibit temperature drift in the scene by arranging the signal processing circuit, and avoid false triggering pressure event, thereby reducing the probability of false triggering/false activating/false igniting of the electronic cigarette, and has better effect and cost control.

In the description of the present specification, reference to the term "some embodiments," "other embodiments," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples merely represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of the application should be assessed as that of the appended claims.

Claims

1. A signal processing method, comprising:

2. The signal processing method according to claim 1, wherein controlling the output voltage of the piezoelectric sensor to be in a preset range includes:

3. The signal processing method of claim 1, wherein responding to a force withdrawal event occurring at the piezoelectric sensor comprises:

detecting an output voltage of the piezoelectric sensor;

the voltage of the first voltage area is not smaller than the voltage threshold, and the voltage of the second voltage area is smaller than the voltage threshold.

4. The signal processing method according to claim 1, wherein the reset period of the periodic reset is smaller than a second preset time, the second preset time being a time required for the piezoelectric sensor to ramp up the output voltage from the baseline voltage to the voltage threshold due to a temperature drift effect in an unpressurized condition.

5. A signal processing method according to claim 1 or 4, wherein the reset period of the periodic reset is greater than the rising edge time and/or falling edge time of the output voltage when a pressure event occurs to the piezoelectric sensor.

6. The signal processing method of claim 1, wherein periodically resetting the piezoelectric sensor in the event that a pressure event does not occur in the piezoelectric sensor comprises:

7. The signal processing method according to claim 1 or 6, characterized in that the method further comprises:

and if the output voltage of the piezoelectric sensor is detected not to be smaller than the voltage threshold value, stopping periodic resetting of the piezoelectric sensor.

8. The signal processing method of claim 7, wherein controlling the output voltage of the piezoelectric sensor to be within a preset range comprises: increasing the capacitance of the first capacitor so that the output voltage of the piezoelectric sensor decreases to not exceed the voltage threshold; the first capacitor is arranged between a voltage output pin and a reference voltage input pin of the piezoelectric sensor; after suspending the periodic reset of the piezoelectric sensor, the method further comprises: reducing the capacitance of the first capacitor.

9. A signal processing circuit, comprising:

a control module for performing the signal processing method of any one of claims 1 to 8;

10. The signal processing circuit of claim 9, wherein the control module comprises: a comparison unit and a logic unit; the input end of the comparison unit is connected with the voltage output pin of the piezoelectric sensor, the output end of the comparison unit is connected with the input end of the logic unit, and the output end of the logic unit is connected with the controlled module; wherein,

11. The signal processing circuit of claim 9, wherein the controlled module comprises: a first capacitor; the first capacitor is arranged between a voltage output pin and a reference voltage input pin of the piezoelectric sensor; the working state of the first capacitor comprises increasing the capacitance value or recovering to the initial capacitance value.

12. The signal processing circuit according to claim 9 or 11, wherein the controlled module comprises:

A reset switch; the first end of the reset switch is connected with a voltage output pin of the piezoelectric sensor, the second end of the reset switch is connected with a reference voltage input pin of the piezoelectric sensor, and the third end of the reset switch is connected with the output end of the control module; wherein,

13. A piezoelectric sensing system, comprising: a piezoelectric sensor and the signal processing circuit of any one of claims 9 to 12, the piezoelectric sensor being connected to the signal processing circuit.

14. An electronic cigarette, comprising: a main body on which a piezoelectric sensor and the signal processing circuit of any one of claims 9 to 12 are provided, the piezoelectric sensor being connected to the signal processing circuit.