CN111595494A

CN111595494A - Capacitance detection circuit, integrated circuit, electronic device, and capacitance detection method

Info

Publication number: CN111595494A
Application number: CN202010437983.0A
Authority: CN
Inventors: 陈培腾; 陈敏; 吴红兵
Original assignee: Chipsea Technologies Shenzhen Co Ltd
Current assignee: Chipsea Technologies Shenzhen Co Ltd
Priority date: 2020-05-21
Filing date: 2020-05-21
Publication date: 2020-08-28
Anticipated expiration: 2040-05-21
Also published as: CN111595494B; CN114924128A

Abstract

The embodiment of the application provides a capacitance detection circuit, an integrated circuit, electronic equipment and a capacitance detection method, wherein the capacitance detection circuit comprises an integrating circuit, a voltage detection circuit and a capacitance adjusting circuit, and the integrating circuit comprises a comparator and an integrating capacitor; the integrating capacitor is connected between the input end and the output end of the comparator; the voltage detection circuit is connected with the integration circuit and used for detecting the accumulated voltage of the integration capacitor in a single integration mode and outputting the regulated voltage according to the accumulated voltage; the capacitance adjusting voltage is connected with the voltage detection circuit and the integrating circuit and used for adjusting the equivalent capacitance of the integrating capacitor according to the adjusting signal so as to adjust the accumulated voltage of the next integration of the integrating capacitor. The capacitance detection circuit provided by the embodiment of the application can realize accurate detection of large capacitance and quick detection of small capacitance.

Description

Capacitance detection circuit, integrated circuit, electronic device, and capacitance detection method

Technical Field

The present application relates to the field of capacitance detection technologies, and in particular, to a capacitance detection circuit, an integrated circuit, an electronic device, and a capacitance detection method.

Background

Through technical evolution and mass production inspection for many years, the touch key technology is mature day by day. Due to the advantages of convenience, fashion, low cost, and the like, more and more electronic products are turning from traditional mechanical keys to touch keys. The touch key judges the occurrence of a touch event by detecting the capacitance change on the key through the capacitance detection integrated circuit, and the capacitance change on the detection pin of the capacitance detection integrated circuit can be caused by the capacitance change of the key so as to detect the touch event.

However, capacitance changes on the detection pins under different working conditions are different, and the conventional capacitance detection integrated circuit is often difficult to deal with the capacitance changes under different working conditions. For example, when the capacitance change on the detection pin is small, multiple integrations are needed to reach the touch activation threshold, resulting in a slow detection speed; when the capacitance change on the detection pin is large, then integration overflow can result. Therefore, there is a need for improvement in the prior art.

Disclosure of Invention

In view of the above problems, embodiments of the present application provide a capacitance detection circuit, an integrated circuit, an electronic device, and a capacitance detection method to solve the above technical problems.

The embodiment of the application is realized by adopting the following technical scheme:

a capacitance detection circuit comprises an integrating circuit, a voltage detection circuit and a capacitance adjusting circuit, wherein the integrating circuit comprises a comparator and an integrating capacitor; the integrating capacitor is connected between the input end and the output end of the comparator; the voltage detection circuit is connected with the integration circuit and used for detecting the accumulated voltage of the integration capacitor in a single integration mode and outputting the regulated voltage according to the accumulated voltage; the capacitance adjusting voltage is connected with the voltage detection circuit and the integrating circuit and used for adjusting the equivalent capacitance of the integrating capacitor according to the adjusting signal so as to adjust the accumulated voltage of the next integration of the integrating capacitor.

In some embodiments, the adjustment signal includes a first adjustment signal and a second adjustment signal; the voltage detection circuit is used for outputting a first adjusting signal when the accumulated voltage is smaller than a first preset threshold voltage; the capacitance adjusting circuit is used for reducing the equivalent capacitance of the integrating capacitor according to the first adjusting signal so as to increase the accumulated voltage of the next integration of the integrating capacitor; the capacitance detection circuit is also used for outputting a second adjusting signal when the accumulated voltage is greater than a second preset threshold voltage; the capacitance adjusting circuit is also used for increasing the equivalent capacitance of the integrating capacitor according to the second adjusting signal so as to reduce the accumulated voltage of the next integration of the integrating capacitor; wherein. The first preset threshold voltage is less than or equal to the second preset threshold voltage.

In some embodiments, the capacitance adjusting circuit is further configured to reduce an equivalent capacitance of the integrating capacitor according to the first adjusting signal to increase an accumulated voltage of a next integration of the integrating capacitor to a first preset voltage; and increasing the equivalent capacitance of the integrating capacitor according to the second adjusting signal so as to reduce the accumulated voltage of the integrating capacitor at the next integration time to a second preset voltage.

In some embodiments, the voltage detection circuit is further configured to adjust a magnitude of the first adjustment signal or the second adjustment signal according to a magnitude of the accumulated voltage, wherein the first adjustment signal and the second adjustment signal respectively have a positive correlation with the accumulated voltage; the capacitance adjusting circuit is also used for reducing the equivalent capacitance of the integrating capacitor step by step when the first adjusting signal is reduced; the capacitance adjusting circuit is further used for increasing the equivalent capacitance of the integrating capacitor step by step when the second adjusting signal is increased.

In some embodiments, the adjustment signal is a current adjustment signal; the capacitance adjusting circuit comprises a transconductance amplifier, a first resistor and a second resistor, wherein the first resistor is connected between a first input end and a second input end of the transconductance amplifier, the second resistor is connected between an output end of the transconductance amplifier and a first input end of the transconductance amplifier, one end of an integrating capacitor is connected to the second input end of the transconductance amplifier, the other end of the integrating capacitor is connected to an output end of a comparator, the first input end of the transconductance amplifier is further connected to an input end of the comparator, and a current input end of the transconductance amplifier is connected to the voltage detecting circuit to receive a current adjusting signal.

In some embodiments, the voltage detection circuit includes a step detection circuit, a quantizer and a current control circuit, the compensation detection circuit is connected to the output end of the comparator and is used for detecting the accumulated voltage of the integration capacitor for single integration; the quantizer is connected with the step length detection circuit and used for outputting a voltage regulation signal according to the accumulated voltage; the current control circuit is connected to the quantizer and is used for outputting a current adjusting signal to the transconductance amplifier according to the voltage adjusting signal.

In some embodiments, the capacitance detection circuit further comprises a first switched-capacitor circuit, a second switched-capacitor circuit, and a second switched-capacitor circuit; one end of the first switch capacitor circuit is used for receiving an input signal, and the other end of the first switch capacitor circuit is connected to the integrating circuit; one end of the second switched capacitor circuit is used for receiving an input signal, and the other end of the second switched capacitor circuit is connected to the integrating circuit; the first switch capacitor circuit and the second switch capacitor circuit have opposite integration directions, and the first switch capacitor circuit is also used for connecting a detection pin; the magnitude of the accumulated voltage is positively correlated with the change in capacitance of the detection pin.

In some embodiments, the first switched-capacitor circuit includes a first capacitor, a first switch, a second switch, a third switch, a fourth switch, and a fifth switch; the first end of the first capacitor is connected to one end of the first switch, the other end of the first switch is connected to one end of the second switch, the other end of the second switch is used for receiving an input signal, the first end of the first capacitor is grounded through a third switch, the second end of the first capacitor is connected to the integrating circuit through a fourth capacitor, the second end of the first capacitor is grounded through a fifth switch, and a connection node of the first switch and the second switch is used for connecting a detection pin;

the second switch capacitor circuit comprises a second capacitor, a third capacitor, a sixth switch, a seventh switch and an eighth switch; one end of the sixth switch is used for receiving an input signal, the other end of the sixth switch is connected to one end of the seventh switch, the other end of the seventh switch is connected to one end of the eighth switch, the other end of the eighth switch is connected to the integrating circuit, the first end of the second capacitor is connected between the seventh switch and the eighth switch, the second end of the second capacitor is grounded, the first end of the third capacitor is connected between the sixth switch and the seventh switch, and the second end of the third capacitor is grounded.

An embodiment of the present application further provides an integrated circuit, including any one of the capacitance detection circuits described above.

The embodiment of the application also provides electronic equipment which comprises an equipment main body and the integrated circuit arranged on the equipment main body.

The embodiment of the application also provides a capacitance detection method which is applied to any one of the capacitance detection circuits, and the method comprises the steps of detecting the accumulated voltage of the integral capacitor in single integration and outputting an adjusting signal according to the accumulated voltage; and adjusting the equivalent capacitance of the integrating capacitor according to the adjusting signal so as to adjust the accumulated voltage of the integrating capacitor for the next integration.

In some embodiments, the adjustment signal includes a first adjustment signal and a second adjustment signal; outputting a regulation signal based on the accumulated voltage, comprising: outputting a first adjusting signal when the accumulated voltage is smaller than a first preset threshold voltage; or outputting a second adjusting signal when the accumulated voltage is greater than a second preset threshold voltage, wherein the first preset threshold voltage is less than or equal to the second preset threshold voltage; adjusting the equivalent capacitance of the integrating capacitor according to the adjusting signal to adjust the accumulated voltage of the integrating capacitor for the next integration, comprising: reducing the equivalent capacitance of the integrating capacitor according to the first adjusting signal to increase the accumulated voltage of the next integration of the integrating capacitor; or increasing the equivalent capacitance of the integrating capacitor according to the second adjusting signal to reduce the accumulated voltage of the next integration of the integrating capacitor.

According to the capacitance detection circuit, the integrated circuit, the electronic device and the capacitance detection method, the capacitance detection circuit is provided with the integrating circuit, the voltage detection circuit and the capacitance adjusting circuit; the integrating circuit comprises a comparator and an integrating capacitor, and the integrating capacitor is connected between the input end and the output end of the comparator; detecting the accumulated voltage of the single integral of the integral capacitor through a voltage detection circuit, and outputting an adjusting signal according to the accumulated voltage; and then the capacitance adjusting circuit adjusts the equivalent capacitance of the integrating capacitor according to the adjusting signal to adjust the accumulated voltage of the integrating capacitor for the next time, so that the capacitance detecting circuit can adaptively adjust the voltage of the integrating capacitor for the next time according to the voltage accumulated by the integrating capacitor for a single time, for example, the voltage accumulated by the integrating capacitor for the next time is increased when the voltage accumulated by the integrating capacitor for a single time is smaller, or the voltage accumulated by the integrating capacitor for the next time is decreased when the voltage accumulated by the integrating capacitor for a single time is larger. Therefore, the problem that the touch threshold value can be reached by multiple times of integration when the capacitance change is large, so that the detection speed is low is solved, or the problem that the integration overflows when the capacitance change is large is solved, so that the accurate detection of the large capacitance and the quick detection of the small capacitance are realized.

These and other aspects of the present application will be more readily apparent from the following description of the embodiments.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 shows a schematic diagram of a capacitive sensing system provided by an embodiment of the present application.

Fig. 2 shows a block diagram of a capacitance detection circuit provided in an embodiment of the present application.

Fig. 3 is a schematic diagram illustrating an accumulated voltage adjustment according to an embodiment of the present application.

Fig. 4 is a schematic diagram illustrating another accumulated voltage adjustment provided in the embodiment of the present application.

Fig. 5 is a schematic diagram illustrating another accumulated voltage adjustment provided in the embodiment of the present application.

Fig. 6 is a schematic diagram illustrating another accumulated voltage adjustment provided in the embodiment of the present application.

Fig. 7 shows a schematic structural diagram of a capacitance detection circuit provided in an embodiment of the present application.

Fig. 8 shows a schematic diagram of the multiplication of the integral capacitance provided by the embodiment of the present application.

Fig. 9 shows a schematic structural diagram of an integrated circuit provided in an embodiment of the present application.

Fig. 10 shows a schematic structural diagram of an electronic device provided in an embodiment of the present application.

Fig. 11 shows a schematic flow chart of a capacitance detection method provided in the present application.

Detailed Description

Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are exemplary only for the purpose of explaining the present application and are not to be construed as limiting the present application.

In order to make the technical solutions of the present application better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Through technical evolution and mass production inspection for many years, the touch key technology is mature day by day. Due to the advantages of convenience, fashion, low cost, and the like, more and more electronic products are turning from traditional mechanical keys to touch keys. The touch key judges the occurrence of a touch event by detecting the capacitance change on the key through the capacitance detection chip, and the capacitance change on the detection pin of the capacitance detection chip can be caused by the capacitance change of the key, so that the touch event is detected.

The existing capacitive touch technology can be classified into Self-Capacitance (Self-Capacitance) and Mutual-Capacitance (Mutual-Capacitance). The current self-contained detection technology mainly has two realization modes:

1. charging and discharging the capacitor by using a pull-up resistor or current, and realizing capacitor key detection according to the difference of system time constants;

2. based on the charge sharing principle, capacitance information is converted into a pull-up resistor or a pull-down resistor, and the obtained voltage or current signal is processed by a signal processing circuit.

In order to solve the above-described problems, the inventors have made a long-term study and have proposed a capacitance detection circuit, an integrated circuit, an electronic apparatus, and a capacitance detection method in the embodiments of the present application, the capacitance detection circuit being provided with an integration circuit, a voltage detection circuit, and a capacitance adjustment circuit; the integrating circuit comprises a comparator and an integrating capacitor, and the integrating capacitor is connected between the input end and the output end of the comparator; detecting the accumulated voltage of the single integral of the integral capacitor through a voltage detection circuit, and outputting an adjusting signal according to the accumulated voltage; adjusting the equivalent capacitance of the integrating capacitor through a capacitance adjusting circuit according to the adjusting signal so as to adjust the accumulated voltage of the next integration of the integrating capacitor; the capacitance detection circuit can adaptively adjust the voltage of the integration capacitor accumulated next time according to the voltage of the integration capacitor accumulated once, for example, the voltage of the integration capacitor accumulated next time is increased when the voltage of the integration capacitor accumulated once is smaller, and the voltage of the integration capacitor accumulated next time is decreased when the voltage of the integration capacitor accumulated once is larger. Therefore, the problems that the detection speed is low due to the fact that the touch threshold value can be reached through multiple times of integration when the capacitance change is large and the integration overflows when the capacitance change is large are solved, and therefore accurate detection of large capacitance and quick detection of small capacitance are achieved.

As shown in fig. 1, fig. 1 schematically illustrates a capacitive sensing system 10 provided by an embodiment of the present invention. The system 10 includes an Excitation Source (Excitation Source)11, a Capacitor-to-voltage converter (CVC) unit 12, and an Analog Signal Process (ASP) unit 13, which are connected in sequence. The CVC unit 12 includes a detection pin TK, which is connected to an external sensor 20, and the sensor 20 may be a capacitive sensor. When a touch event occurs, the signal output by the sensor 20 causes a change in capacitance on the detection pin TK. The CVC unit 12 converts the capacitance change on the detection pin TK into a voltage signal and outputs a signal Vout, the ASP unit 13 quantizes the output signal Vout, and the ASP unit 13 is connected to the external determination circuit 30 so that the external determination circuit 30 determines the occurrence of the touch event based thereon. Specifically, when no touch event occurs, the ASP unit 13 outputs a reference signal, and the determination circuit 30 records the reference signal; the determination circuit 30 simultaneously detects the current signal output by the ASP unit, and determines whether a touch event occurs at the time according to a voltage difference between the current signal and the reference signal, for example, when the voltage difference between the current signal and the reference signal is higher than a preset threshold, it may be determined that the touch event occurs at the time. In the embodiment of the present application, the capacitance variation caused on the detection pin TK due to the touch event is hereinafter referred to as a touch capacitance Ctk.

The ASP unit 13 may be, but is not limited to, an Analog-to-Digital Converter (ADC), a comparator, and a Voltage Controlled Oscillator (VCO). the ASP unit 13 may be selected based on the requirement of an Analog back-end circuit, and is not limited herein.

As shown in fig. 2, based on the capacitance sensing system 10, the present embodiment provides a capacitance detection circuit 100, where the capacitance detection circuit 100 is specifically applied to the CVC unit and is used to convert a capacitance signal into a voltage signal for output.

The capacitance detection circuit 100 includes an integration circuit 110, a voltage detection circuit 120, and a capacitance adjustment circuit 130. The integrating circuit 110 includes a comparator 111 and an integrating capacitor 112, and the integrating capacitor 112 is connected between the input end and the output end of the comparator 111; the voltage detection circuit 120 is connected to the integration circuit 110, and is configured to detect an accumulated voltage of a single integration of the integration capacitor 112, and output an adjustment signal according to the accumulated voltage; the capacitance adjusting circuit 130 is connected to the voltage detecting circuit 120 and the integrating circuit 110, and is configured to adjust an equivalent capacitance of the integrating capacitor 112 according to the adjusting signal, so as to adjust an accumulated voltage of the integrating capacitor 112 for the next integration.

Generally, when the integration circuit works, the touch capacitance Ctk may cause a voltage change at two ends of the integration capacitance 112, and in the conventional capacitance detection circuit, the larger the touch capacitance Ctk is, the larger a voltage difference at two ends of the integration capacitance 112 after a single integration is, that is, the larger the voltage accumulated at two ends of the integration capacitance 112 is, so that the voltage accumulated at two ends of the integration capacitance 112 and the touch capacitance Ctk have a linear relationship, which results in a poor self-adaptive capacity of the conventional capacitance detection circuit for different touch capacitances Ctk. It is specifically shown that when the touch capacitance Ctk is large, the voltage accumulated across the integrating capacitor 112 is large, which may cause the final integration to overflow or saturate; when the touch capacitance Ctk is small, the voltage accumulated at the two ends of the integration capacitor 112 is small, and multiple integrations are needed to reach the touch threshold of the capacitive button, which results in a slow detection speed of the touch event.

In the embodiment of the present application, the voltage detection circuit 120 detects the accumulated voltage of the single integration of the integration capacitor 112, and outputs an adjustment signal according to the accumulated voltage; the capacitance adjusting circuit 130 adjusts the equivalent capacitance of the integrating capacitor 112 according to the adjusting signal, and further adjusts the accumulated voltage of the integrating capacitor 112 for the next time, so that the capacitance detecting circuit 100 can adaptively adjust the voltage of the integrating capacitor 112 for the next time according to the voltage accumulated by the integrating capacitor 112 for a single time. For example, when the voltage accumulated by the integration capacitor 112 at a time is small, the voltage accumulated by the integration capacitor 112 at the next time is increased, so that the integration times can be reduced when the touch capacitor Ctk is small, and the touch event can be quickly detected; when the voltage accumulated by the integration capacitor 112 at a time is larger, the voltage accumulated by the integration capacitor 112 at the next time is reduced, so that integration overflow or saturation is avoided when the touch capacitor Ctk is larger, and accurate detection of a touch event is realized.

Specifically, the adjustment signal includes a first adjustment signal and a second adjustment signal. The voltage detection circuit 120 is configured to output a first adjustment signal when the accumulated voltage of the single integration of the integration capacitor 112 is smaller than a first preset threshold voltage, or output a second adjustment signal when the accumulated voltage of the single integration of the integration capacitor 112 is larger than a second preset threshold voltage; the capacitance adjusting circuit 130 is configured to decrease the equivalent capacitance of the integrating capacitor 112 according to the first adjusting signal to increase the accumulated voltage of the integrating capacitor 112 for the next integration, or to increase the equivalent capacitance of the integrating capacitor 112 according to the second adjusting signal to decrease the accumulated voltage of the integrating capacitor 112 for the next integration. The first preset threshold voltage is less than or equal to the second preset threshold voltage.

In this embodiment, when the accumulated voltage is smaller than the first preset threshold voltage, which indicates that the integrating circuit 110 performs the integration, the integrating capacitor 112 needs more integration times to reach the touch threshold value when accumulating with the accumulated voltage, which results in a slow detection speed of the touch event; when the accumulated voltage is greater than the second predetermined threshold voltage, indicating that the integrating circuit 110 performs the integration, the integrating capacitor 112 may overflow or saturate when performing the accumulation with the accumulated voltage; the voltage range between the first preset threshold voltage and the second preset threshold voltage is a voltage range in which the accumulated voltage of the single integration is appropriate, and within the voltage range, the capacitance detection circuit 100 can achieve accurate touch detection with an appropriate number of integrations on the basis of accumulating the voltage of the single integration. It should be noted that the touch threshold is set manually, and when the voltage across the integrating capacitor 112 reaches a preset touch threshold voltage, it means that the multiple integrations of the integrating circuit 110 have reached the touch threshold, so that the first preset threshold voltage and the second preset threshold voltage can be set according to the touch threshold, so as to achieve fast and accurate touch detection.

In this embodiment, the equivalent capacitance between the input terminal and the output terminal of the comparator is referred to as the equivalent capacitance of the integrating capacitor 112. During the integration process of the integration circuit 110, the magnitude of the equivalent capacitance of the integration capacitor 112 affects the accumulated charge amount of the integration capacitor 112 per integration, i.e. the voltage accumulated across the integration capacitor 112, and the equivalent capacitance of the integration capacitor 112 is inversely proportional to the accumulated voltage per integration, and the larger the equivalent capacitance is, the smaller the accumulated voltage per integration is. Therefore, when the capacitance adjusting circuit 130 receives the first adjusting signal, the accumulated voltage of the integration capacitor 112 for the next integration can be increased by reducing the equivalent capacitance of the integration capacitor 112; when the capacitance adjusting circuit 130 receives the second adjusting signal, the equivalent capacitance of the integrating capacitor 112 is increased, so that the accumulated voltage of the integrating capacitor 112 for the next integration can be decreased.

Further, the capacitance adjusting circuit 130 is further configured to decrease the equivalent capacitance of the integrating capacitor 112 according to the first adjusting signal, so as to increase the accumulated voltage of the integrating capacitor 112 integrated next time to a first preset voltage; or the equivalent capacitance of the integrating capacitor 112 is increased according to the second adjusting signal, so as to reduce the accumulated voltage of the integrating capacitor 112 integrated next time to the second preset voltage.

The first preset voltage and the second preset voltage are both in a voltage range between the first preset threshold voltage and the second preset threshold voltage. For example, the first preset voltage may be greater than or equal to a first preset threshold voltage, and the second preset voltage may be less than or equal to a second preset threshold voltage. Alternatively, the first preset voltage and the second preset voltage may be equal or unequal. In a voltage range between the first preset voltage and the second preset voltage, the capacitance detection circuit 100 can achieve accurate touch detection with an optimal number of integration times on the basis of accumulating the voltage by single integration.

As shown in fig. 2 and 3, fig. 3 is a schematic diagram illustrating adjustment of the accumulated voltage when the accumulated voltage of a single integration is smaller than a first predetermined threshold voltage. Wherein, U_THIs touch threshold voltage, U_BAIs the initial accumulated voltage, U_CBFor the adjusted accumulated voltage, U₁Is a first predetermined threshold voltage. As can be seen from fig. 3, when the touch capacitance Ctk is small, the initial accumulated voltage U of the integration circuit 110_BALess than a first predetermined threshold voltage U₁After the capacitance adjusting circuit 130 adjusts the equivalent capacitance of the integrating capacitor 112, the accumulated voltage U of the next integration_CBWill be greater than the initial accumulated voltage U_BAAccumulated voltage U of the next integration_CBI.e. the first predetermined voltage, will be summed with the sum voltage U in the subsequent integration_CBThe same voltage value is continuously accumulated on the integrating capacitor 112 until the voltage across the integrating capacitor 112 reaches the touch threshold voltage U_TH. In this process, the capacitance detection circuit 100 can reach the touch threshold more quickly with fewer integration times, and realize quick detection when the touch capacitance Ctk is small.

As shown in fig. 2 and 4, fig. 4 is a schematic diagram illustrating adjustment of the accumulated voltage when the accumulated voltage of a single integration is greater than a second predetermined threshold voltage. Wherein, U_THIs touch threshold voltage, U_BAIs the initial accumulated voltage, U_CBFor the adjusted accumulated voltage, U₂Is the second predetermined threshold voltage. As can be seen from fig. 4, when the touch capacitance Ctk is large, the initial accumulated voltage U is greater_BAGreater than a second predetermined threshold voltage U₂After the capacitance adjusting circuit 130 adjusts the equivalent capacitance of the integrating capacitor 112, the accumulated voltage U of the next integration_CBWill be less than the initial accumulated voltage U_BACumulative voltage U_CBI.e. the second predetermined voltage, will be at the accumulated voltage U in the subsequent integration_CBThe same voltage value is continuously accumulated on the integrating capacitor 112 until the voltage across the integrating capacitor 112 reaches the touch threshold voltage U_TH. In this process, the capacitance detection circuit 100 can avoid integral overflow or saturation, thereby realizing accurate detection of touch when the touch capacitance Ctk is large.

In some embodiments, the voltage detection circuit 120 is further configured to adjust the magnitude of the first adjustment signal or the second adjustment signal according to the magnitude of the accumulated voltage; the capacitance adjusting circuit 130 is further configured to gradually decrease the equivalent capacitance of the integrating capacitor 112 when the first adjusting signal decreases; or the equivalent capacitance of the integrating capacitor 112 is increased step by step as the second adjustment signal increases. The first adjusting signal and the second adjusting signal respectively have positive correlation with the accumulated voltage.

When the touch capacitance Ctk is smaller, the accumulated voltage of the single integration of the integration circuit 110 is smaller than the first preset threshold voltage, and in the first adjustment process of the accumulated voltage, the voltage detection circuit 120 may output an initial first adjustment signal according to the initial accumulated voltage, trigger the capacitance adjustment circuit 130 to decrease the equivalent capacitance of the integration capacitor 112 from the initial capacitance value to the first capacitance value, and further increase the second accumulated voltage of the second integration from the initial voltage value to the second voltage value. In the second adjustment process of the accumulated voltage, since the second accumulated voltage is greater than the initial accumulated voltage, the voltage detection circuit 120 may output a second-level first adjustment signal according to the second accumulated voltage, where the second-level first adjustment signal is greater than the initial first adjustment signal. When the capacitance adjustment signal receives the two-stage first adjustment signal, the equivalent capacitance of the integration capacitor 112 is decreased from the first capacitance value to the second capacitance value, so that the third accumulated voltage of the third integration is increased from the second voltage value to the third voltage value. In the subsequent integration process, the equivalent capacitance of the integrating capacitor 112 is gradually decreased, and the accumulated voltage of the single integration is further gradually increased, so that the accumulated voltage of the single integration gradually approaches to the first preset voltage, and the accuracy of adjusting the accumulated voltage is improved. In some embodiments, in the process of gradually approaching the accumulated voltage to the first preset voltage, if the current accumulated voltage has reached the minimum requirement of the fast touch detection, the subsequent approaching process may be stopped, and in the subsequent integration, the voltages across the integrating capacitor 112 are accumulated by the current accumulated voltage until the voltages across the integrating capacitor 112 reach the touch threshold voltage, so that the subsequent approaching of the accumulated voltage is omitted in the process, and the operating cost of the system is further reduced.

As shown in fig. 2 and 5, U_THIs touch threshold voltage, U_BAIs the initial accumulated voltage, U_CBIs the second accumulated voltage, U_DCIs the third accumulated voltage, U₁Is a first predetermined threshold voltage. As can be seen from FIG. 5, when the touch capacitance Ctk is small, the initial accumulated voltage U is small_BALess than a first predetermined threshold voltage U₁After the capacitance adjusting circuit 130 adjusts the equivalent capacitance of the integrating capacitor 112, the second integrated second accumulated voltage U is obtained_CBWill be greater than the initial accumulated voltage U_BAAnd a third accumulated voltage U of a third integration_DCWill be greater than the second accumulated voltage U_CBIn the subsequent integration, the accumulated voltage of the single integration is continuously increased until the accumulated voltage of the single integration is greater than or equal to the first preset voltage. After multiple integrations, the voltages across integrating capacitor 112 continue to accumulate until a touch threshold voltage U is reached_TH。

When the touch capacitance Ctk is large, the accumulated voltage of the single integration of the integration circuit 110 is greater than the second preset threshold voltage, and in the first adjustment process of the accumulated voltage, the voltage detection circuit 120 may output an initial second adjustment signal according to the initial accumulated voltage, and trigger the capacitance adjustment circuit 130 to increase the equivalent capacitance of the integration capacitor 112 from the initial capacitance value to the first capacitance value, so that the second accumulated voltage of the second integration is reduced from the initial voltage value to the second voltage value. In the second adjustment process of the accumulated voltage, since the second accumulated voltage is already smaller than the initial accumulated voltage, the voltage detection circuit 120 may output a second level second adjustment signal according to the second accumulated voltage, where the second level second adjustment signal is smaller than the initial second adjustment signal. When the capacitance adjustment signal receives the two-stage second adjustment signal, the equivalent capacitance of the integration capacitor 112 is increased from the first capacitance value to the second capacitance value, so that the third accumulated voltage of the third integration is decreased from the second voltage value to the third voltage value. In the subsequent integration process, the equivalent capacitance of the integrating capacitor 112 is gradually increased, and the accumulated voltage of the single integration is further gradually decreased, so that the accumulated voltage of the single integration gradually approaches to the second preset voltage, and the accuracy of adjusting the accumulated voltage is improved. In some embodiments, in the process of gradually approaching the accumulated voltage to the second preset voltage, if the current accumulated voltage has reached the minimum requirement for accurate touch detection, the subsequent approaching process may be stopped, and in the subsequent integration, the voltages across the integrating capacitor 112 are accumulated by the current accumulated voltage until the voltages across the integrating capacitor 112 reach the touch threshold voltage, so that the subsequent approaching of the accumulated voltage is omitted in the process, and the operating cost of the system is further reduced.

As shown in fig. 2 and 6, U_THIs touch threshold voltage, U_BAIs the initial accumulated voltage, U_CBIs the second accumulated voltage, U_DCIs the third accumulated voltage, U₂Is the second predetermined threshold voltage. As can be seen from fig. 6, when the touch capacitance Ctk is large, the initial accumulated voltage U is greater_BAGreater than a second predetermined threshold voltage U₂After the capacitance adjusting circuit 130 adjusts the equivalent capacitance of the integrating capacitor 112, the second integrated second accumulated voltage U is obtained_CBWill be less than the initial accumulated voltage U_BAAnd a third accumulated voltage U of a third integration_DCWill be less than the second accumulated voltage U_CBIn the subsequent integration, the accumulated voltage of the single integration is continuously reduced until the accumulated voltage of the single integration is less than or equal to the second preset voltage. The voltages across integrating capacitor 112 are continuously accumulated through multiple integrations until a touch threshold voltage U is reached_TH。

As shown in fig. 7, fig. 7 is a schematic diagram illustrating a circuit structure of the capacitance detection circuit 100 according to an embodiment of the present application. The capacitance detection circuit 100 includes an integration circuit 110, a voltage detection circuit 120 connected to the integration circuit 110, and a capacitance adjustment circuit 130 connected to the voltage detection circuit 120 and the integration circuit 110. The integrating circuit 110 includes a comparator a1 and an integrating capacitor Cint connected between the input terminal and the output terminal of the comparator a 1.

The voltage detection circuit 120 includes a step detection circuit 121, a quantizer 122, and a current control circuit 123. The step length detection circuit 121 is connected to the output end of the comparator a1, and is used for detecting the accumulated voltage of the single integral of the integral capacitor Cint; the quantizer 122 is connected to the step detection circuit 121, and is configured to output a voltage adjustment signal according to the accumulated voltage; the current control circuit 123 is connected to the quantizer 122, and is configured to output a current adjustment signal according to the voltage adjustment signal. The first adjusting signal and the second adjusting signal are both current adjusting signals.

The capacitance adjusting circuit 130 includes a transconductance amplifier a2, a first resistor R1, and a second resistor R2. The first resistor R1 is connected between the first input terminal and the second input terminal of the transconductance amplifier a2, the second resistor R2 is connected between the output terminal of the transconductance amplifier a2 and the first input terminal of the transconductance amplifier a2, one end of the integrating capacitor Cint is connected to the second input terminal of the transconductance amplifier a2, the other end of the integrating capacitor Cint is connected to the output terminal of the comparator a1, the first input terminal of the transconductance amplifier a2 is further connected to the input terminal of the comparator a1, and the current input terminal of the transconductance amplifier a2 is connected to the voltage detection circuit 120 to receive the current adjustment signal.

Further, the capacitance detection circuit 100 further includes a first switched-capacitor circuit 140 and a second switched-capacitor circuit 150. The first switched capacitor circuit 140 has one end for receiving the input signal Vs and the other end connected to the integrating circuit 110; the second switched-capacitor circuit 150 has one end for receiving the input signal Vs and the other end connected to the integrating circuit 110. The integration directions of the first switched capacitor circuit 140 and the second switched capacitor circuit 150 are opposite, and the first switched capacitor circuit 140 is further used for connecting a detection pin TK; the magnitude of the accumulated voltage is in positive correlation with the capacitance change of the TK.

In this embodiment, the first switched capacitor circuit 140 includes a first capacitor C1, a first switch SA1, a second switch SA2, a third switch SA3, a fourth switch SA4, and a fifth switch SA 5; a first end of a first capacitor C1 is connected to one end of a first switch SA1, the other end of the first switch SA1 is connected to one end of a second switch SA2, the other end of the second switch SA2 is used for receiving an input signal, a first end of a first capacitor C1 is further connected to ground through a third switch SA3, a second end of the first capacitor C1 is connected to the integrating circuit 110 through a fourth switch SA4, a second end of the first capacitor C1 is further connected to ground through a fifth switch SA5, and a connection node between the first switch SA1 and the second switch SA2 is used for connecting the detection pin TK; the second switched-capacitor circuit 150 includes a second capacitor C2, a third capacitor C3, a sixth switch SA6, a seventh switch SA7, and an eighth switch SA 8; one end of the sixth switch SA6 is used for receiving the input signal Vs, the other end is connected to one end of the seventh switch SA7, the other end of the seventh switch SA7 is connected to one end of the eighth switch SA8, the other end of the eighth switch SA8 is connected to the integrating circuit 110, the first end of the second capacitor C2 is connected between the seventh switch SA7 and the eighth switch SA8, the second end is grounded, and the first end of the third capacitor C3 is connected between the sixth switch SA6 and the seventh switch SA7, and the second end is grounded.

The principle of the capacitance detection circuit is as follows:

the switches (SA1, SA2, SA3, SA4, SA5, SA6, SA7, SA8) are electronic switches, which may be, but not limited to, a triode, a MOS transistor, and a thyristor. The switches (SA1, SA2, SA3, SA4, SA5, SA6, SA7, SA8) are controlled by a set of external non-overlapping clock signals (Ph1, Ph2), i.e. the clock signal Ph1 and the clock signal Ph2 cannot be high at the same time.

The second switch SA2, the third switch SA3, the fourth switch SA4, the sixth switch SA6 and the eighth switch SA8 are controlled by a clock signal Ph1, and when the clock signal Ph1 is at a high level, the switches (SA2, SA3, SA4, SA6 and SA8) are controlled to be turned on; the first switch SA1, the fifth switch SA5, and the seventh switch SA7 are controlled by a clock signal Ph2, and the switches (SA1, SA5, SA7) are controlled to be turned on when the clock signal Ph2 is at a high level.

The input signal VS is an external signal and can be generated by an external excitation source. Due to the capacitive coupling effect in the circuit, there will be an inherent capacitance Cpin of the coupling on the detection pin TK. When a touch event occurs, a touch capacitance Ctk is generated on the detection pin TK, and at this time, the capacitance on the detection pin TK is actually the sum of the inherent capacitance Cpin and the touch capacitance Ctk.

In a single integration period, when the clock signal Ph2 is at a high level, the charge on the inherent capacitor Cpin is shared with the first capacitor C1, so that part of the charge on the inherent capacitor Cpin is transferred to the first capacitor C1, and simultaneously the charge on the third capacitor C3 is shared with the second capacitor C2, so that part of the charge on the third capacitor C3 is transferred to the second capacitor C2; when the clock signal Ph1 is at a high level, the input signal Vs charges the inherent capacitor Cpin and the third capacitor C3 on the detection pin TK, and the charges of the first capacitor C1 and the second capacitor C2 are all transferred to the integrating capacitor Cint, thereby accumulating the voltage on the integrating capacitor Cint.

Assume that the voltage value of the input signal Vs is V_sThe capacitance values of the first capacitor C1 and the second capacitor C2 are both C_iThe capacitance value of the inherent capacitance Cpin is C_pinThe capacitance value of the touch capacitance Ctk is C_tkThe capacitance value of the third capacitor C3 is C_refThe equivalent capacitance value of the integrating capacitor Cint is Ceq. Then the accumulated voltage of the integrating capacitor Cint during a single integration period is:

according to the equation (1), in the detection of a single touch event, that is, under the condition that the touch capacitance Ctk is not changed, the equivalent capacitance of the integration capacitance Cint and the accumulated voltage of the integration capacitance Cint in the single integration form a negative correlation relationship. The larger the equivalent capacitance of the integrating capacitor Cint is, the smaller the accumulated voltage of single integration is; the smaller the equivalent capacitance of the integration capacitor Cint, the larger the accumulated voltage of a single integration.

Further, the step detection circuit 121 detects a change in voltage across the integrating capacitor Cint, and after the voltage is accumulated across the integrating capacitor Cint, the step detection circuit 121 detects the magnitude of the accumulated voltage at the same time, at this time, the quantizer 122 outputs a control voltage to the current control circuit 123 according to the accumulated voltage, and the current control circuit 123 outputs a corresponding control current to the transconductance amplifier a2 after receiving the control voltage. The control current is a bias current of the transconductance amplifier a2, and since the transconductance of the transconductance amplifier a2 is proportional to the bias current, the bias current can cause the change of the transconductance amplifier a2, and the change of the transconductance amplifier a2 can cause the change of the equivalent capacitance of the integration capacitor Cint, thereby changing the accumulated voltage of the integration capacitor Cint at the next integration time.

Specifically, as shown in FIG. 8, I_scFor short-circuit current, V_inIs the input voltage of the integrating circuit 110, I_inIs the input current, V, of the integrating circuit 110₊And V-is the non-inverting and inverting input voltages, I, of the transconductance amplifier A2₀Is the current of the second resistor R2. Wherein the content of the first and second substances,

I₀＝gm(V₊-V_-)＝gm×R×I_sc(3)

r is the resistance value of the resistor R1; s is a complex frequency; gm is the transconductance of the transconductance amplifier a 2; c_intIs the capacitance value of the integrating capacitor Cint.

Further, the input current of the integrating circuit 110 is equal to the sum of the short-circuit current and the current of the second resistor R2, that is:

thus, the equivalent impedance of the integrating circuit 110 is:

in formula (5), (1+ gm × R) C_intI.e. the equivalent capacitance of the integrating capacitor Cint. Therefore, by the action of the transconductance amplifier a2, the original capacitance value C of the integrating capacitor Cint can be set_intMultiplication to (1+ gm × R) C_intThe effect of large capacitance is achieved by small capacitance, so that the area of a chip is effectively reduced, and the cost is reduced; on the other hand, the equivalent capacitance Ceq of the integrating capacitor Cint can be changed by controlling the transconductance of the transconductance amplifier a2, so that the accumulated voltage of the integrating capacitor in single integration can be changed.

When the touch capacitance Ctk is smaller, the voltage accumulated on the integration capacitor Cint by the integration circuit 110 through single integration is smaller than the first preset threshold voltage, at this time, the step detection circuit 121 detects the change of the voltage at the two ends of the integration capacitor Cint, at this time, the quantizer 122 outputs a smaller control voltage to the current control circuit 123, so that the current control circuit 123 outputs a smaller control current to the transconductance amplifier a2, the control current is the bias current of the transconductance amplifier a2, and at this time, the bias current of the transconductance amplifier a2 is reduced. Since the transconductance of the transconductance amplifier a2 is positively correlated with the bias current, the decrease in the bias current causes a corresponding decrease in the transconductance, and thus the equivalent capacitance of the integrating circuit 110 is decreased. After the equivalent capacitance of the integration circuit 110 is reduced, in the subsequent integration process, the accumulated voltage accumulated on the integration capacitor Cint by single integration is increased, so that the voltages at the two ends of the integration capacitor can quickly reach the touch threshold voltage with fewer integration times, and the quick detection of the touch event is realized.

When the touch capacitance Ctk is large, the voltage accumulated on the integration capacitance Cint by the integration circuit 110 through single integration is larger than the second preset threshold voltage, at this time, the step detection circuit 121 detects the change of the voltage at the two ends of the integration capacitance Cint, at this time, the quantizer 122 outputs a large control voltage to the current control circuit 123, so that the current control circuit 123 outputs a large control current to the transconductance amplifier a2, the control current is the bias current of the transconductance amplifier a2, and at this time, the bias current of the transconductance amplifier a2 is increased. Since the transconductance of the transconductance amplifier a2 is in positive correlation with the bias current, the increase in the bias current leads to a corresponding increase in the transconductance, and thus the equivalent capacitance of the integrating circuit 110 is increased. After the equivalent capacitance of the integration circuit 110 is increased, in the subsequent integration process, the accumulated voltage accumulated on the integration capacitor Cint by single integration is reduced, so that the integration overflow or saturation is avoided, and the accurate detection of the touch event is realized.

In summary, the capacitance detection circuit provided in this embodiment detects the voltage change at the two ends of the integrating capacitor through the step detection circuit, and then controls the control current output by the current control circuit through the quantizer to change the bias current of the transconductance amplifier, so as to change the equivalent capacitance of the integrating capacitor, thereby changing the accumulated voltage of the integrating capacitor in a single integration, so that when the capacitance change on the detection pin is small, the touch activation threshold is reached with a small number of integration times, the detection speed is increased, and the rapid detection of the touch event is realized; when the capacitance change on the detection pin is large, integral overflow or saturation is avoided, and accurate detection of the touch event is realized.

As shown in fig. 9, an integrated circuit 200 is further provided in the embodiment of the present application, where the integrated circuit 200 includes the capacitance detection circuit described above.

In this embodiment, the integrated circuit 200 may be, but is not limited to, a capacitance detection chip.

As shown in fig. 10, an electronic device 300 is further provided in the embodiment of the present application, where the electronic device 300 includes a device main body 310 and the integrated circuit 200, where the integrated circuit 200 is disposed in the device main body 310.

In this embodiment, the electronic device 300 may be a mobile phone or a smart phone (e.g., an iPhone (TM) based phone), a portable game device (e.g., Nintendo DS (TM), PlayStation portable (TM), Gameboy Advance (TM), iPhone (TM)), a laptop, a PDA, a portable internet appliance, a music player, and a data storage device, other handheld devices, and a Head Mounted Device (HMD) such as a watch, a headset, a pendant, etc., and the electronic device 300 may also be other wearable devices (e.g., a Head Mounted Device (HMD) such as electronic glasses, an electronic garment, an electronic bracelet, an electronic necklace, an electronic tattoo, an electronic device, or a smart watch).

The electronic device 300 may also be any of a number of electronic devices including, but not limited to, cellular phones, smart phones, other wireless communication devices, personal digital assistants, audio players, other media players, music recorders, video recorders, cameras, other media recorders, radios, medical devices, vehicle transportation equipment, calculators, programmable remote controllers, pagers, laptop computers, desktop computers, printers, netbook computers, Personal Digital Assistants (PDAs), Portable Multimedia Players (PMPs), moving Picture experts group (MPEG-1 or MPEG-2) Audio layer 3(MP3) players, portable medical devices, and digital cameras, and combinations thereof.

As shown in fig. 11, the present embodiment further provides a capacitance detection method 400, which is applied to the capacitance detection circuit 100. The capacitance detection method 400 may include the following steps S410 to S420.

Step S410: and detecting the accumulated voltage of the single integration of the integration capacitor, and outputting an adjusting signal according to the accumulated voltage.

The adjustment signal includes a first adjustment signal and a second adjustment signal. In this embodiment, the first adjustment signal is output when the accumulated voltage is less than the first preset threshold voltage; or outputting a second adjusting signal when the accumulated voltage is greater than a second preset threshold voltage.

When the accumulated voltage is smaller than the first preset threshold voltage, it indicates that when the integration is performed, the integration capacitor needs more integration times to reach the touch threshold value when the accumulation is performed by using the accumulated voltage, and the detection speed of the touch event is slow; when the accumulated voltage is greater than the second preset threshold voltage, the integration capacitor is indicated to overflow or saturate when accumulated by the accumulated voltage; the voltage range between the first preset threshold voltage and the second preset threshold voltage is a voltage range in which the accumulated voltage of the single integration is appropriate, and within the voltage range, accurate touch detection can be achieved by appropriate integration times on the basis of accumulating the voltage of the single integration. It should be noted that the touch threshold is set manually, and when the voltage at the two ends of the integration capacitor reaches a preset touch threshold voltage, it indicates that the multiple integrations have reached the touch threshold, so that the first preset threshold voltage and the second preset threshold voltage can be set according to the touch threshold, so as to achieve fast and accurate touch detection.

In some embodiments, the magnitude of the first adjustment signal or the second adjustment signal may be adjusted according to the magnitude of the accumulated voltage. The first adjusting signal and the second adjusting signal respectively form positive correlation with the accumulated voltage.

Step S420: and adjusting the equivalent capacitance of the integrating capacitor according to the adjusting signal so as to adjust the accumulated voltage of the next integration of the integrating capacitor.

In this embodiment, the equivalent capacitance of the integrating capacitor is reduced according to the first adjustment signal to increase the accumulated voltage of the integrating capacitor at the next integration; or increasing the equivalent capacitance of the integrating capacitor according to the second adjusting signal to reduce the accumulated voltage of the integrating capacitor at the next time.

In the integration process, the magnitude of the equivalent capacitance of the integration capacitor affects the charge amount accumulated by the integration capacitor at each time, namely the voltage accumulated at two ends of the integration capacitor, and the equivalent capacitance of the integration capacitor is in inverse proportion to the accumulated voltage at each time of integration, and the larger the equivalent capacitance is, the smaller the accumulated voltage at a single time of integration is. Therefore, the equivalent capacitance of the integrating capacitor is reduced by reducing the first adjusting signal, so that the accumulated voltage of the integrating capacitor in the next integration can be increased; the equivalent capacitance of the integrating capacitor is increased by increasing the second adjusting signal, so that the accumulated voltage of the integrating capacitor at the next integration can be reduced.

In this embodiment, the equivalent capacitance of the integrating capacitor is reduced according to the first adjusting signal to increase the accumulated voltage of the integrating capacitor at the next integration time to a first preset voltage; or increasing the equivalent capacitance of the integrating capacitor according to the second adjusting signal so as to reduce the accumulated voltage of the integrating capacitor at the next integration time to a second preset voltage. The first preset voltage and the second preset voltage are both within a voltage range between the first preset threshold voltage and the second preset threshold voltage. For example, the first preset voltage may be greater than or equal to a first preset threshold voltage, and the second preset voltage may be less than or equal to a second preset threshold voltage. Alternatively, the first preset voltage and the second preset voltage may be equal or unequal. In a voltage range between the first preset voltage and the second preset voltage, the capacitance detection circuit 100 can achieve accurate touch detection with an optimal number of integration times on the basis of accumulating the voltage by single integration.

Specifically, when the touch capacitance is small, the initial accumulation voltage of the integration circuit is smaller than a first preset threshold voltage, after the equivalent capacitance of the integration capacitor is adjusted, the accumulation voltage of the next integration is larger than the initial accumulation voltage, the accumulation voltage of the next integration is also the first preset voltage, and in the subsequent integration, the accumulation is continuously performed on the integration capacitor by the same voltage value as the first preset voltage until the voltages at the two ends of the integration capacitor reach the touch threshold voltage. In this process, the touch threshold can be reached more quickly with fewer integration times, enabling fast detection of touch events when the touch capacitance is small.

When the touch capacitor is large, the initial accumulation voltage is larger than the second preset threshold voltage, after the equivalent capacitance of the integration capacitor is adjusted, the accumulation voltage of the next integration is smaller than the initial accumulation voltage, the accumulation voltage of the next integration is also the second preset voltage, and in the subsequent integration, the same voltage value of the accumulation voltage is continuously accumulated on the integration capacitor until the voltages at the two ends of the integration capacitor reach the touch threshold voltage. In the process, the overflow or saturation of the integral can be avoided, so that the accurate detection of the touch is realized when the touch capacitance is large.

In some embodiments, after adjusting the magnitude of the first adjustment signal or the second adjustment signal according to the accumulated voltage, the equivalent capacitance of the integration capacitor may be further decreased step by step when the first adjustment signal is decreased, or increased step by step when the second adjustment signal is increased.

Specifically, when the touch capacitance is small, the accumulated voltage of the single integration is smaller than a first preset threshold voltage, in the first adjustment process of the accumulated voltage, an initial first adjustment signal can be output according to the initial accumulated voltage, and then the equivalent capacitance of the integration capacitor is reduced from the initial capacitance value to the first capacitance value, so that the second accumulated voltage of the second integration is increased from the initial voltage value to the second voltage value. In the second adjustment process of the accumulated voltage, because the second accumulated voltage is greater than the initial accumulated voltage, a second-level first adjustment signal can be output according to the second accumulated voltage, and the second-level first adjustment signal is greater than the initial first adjustment signal. And according to the second-stage first adjusting signal, the equivalent capacitance of the integrating capacitor is reduced from the first capacitance value to the second capacitance value, and further the third accumulated voltage of the third integration is increased from the second voltage value to the third voltage value. In the subsequent integration process, the equivalent capacitance of the integration capacitor is gradually reduced, and then the accumulated voltage of the single integration is gradually increased, so that the accumulated voltage of the single integration gradually approaches to the first preset voltage, and the accuracy of adjusting the accumulated voltage is improved. In some embodiments, in the process of gradually approaching the accumulated voltage to the first preset voltage, if the current accumulated voltage has reached the minimum requirement of the fast touch detection, the subsequent approaching process may be stopped, and in the subsequent integration, the voltages at the two ends of the integrating capacitor are accumulated by the current accumulated voltage until the voltages at the two ends of the integrating capacitor reach the touch threshold voltage, so that the subsequent approaching of the accumulated voltage is omitted in the process, and the operating cost of the system is further reduced.

When the touch capacitor is large, the accumulated voltage of the single integral is larger than the second preset threshold voltage, in the first adjustment process of the accumulated voltage, an initial second adjusting signal can be output according to the initial accumulated voltage, the equivalent capacitor of the integral capacitor is increased from the initial capacitance value to the first capacitance value, and then the second accumulated voltage of the second integral is reduced from the initial voltage value to the second voltage value. In the second adjustment process of the accumulated voltage, because the second accumulated voltage is already smaller than the initial accumulated voltage, a secondary second adjustment signal can be output according to the second accumulated voltage, and the secondary second adjustment signal is smaller than the initial second adjustment signal. And increasing the equivalent capacitance of the integrating capacitor from the first capacitance value to a second capacitance value according to the secondary second adjusting signal, so that a third accumulated voltage of the third integration is reduced from a second voltage value to a third voltage value. In the subsequent integration process, the equivalent capacitance of the integration capacitor is gradually increased, and then the accumulated voltage of single integration is gradually reduced, so that the accumulated voltage of single integration gradually approaches to the second preset voltage, and the accuracy of adjusting the accumulated voltage is improved. In some embodiments, in the process of gradually approaching the accumulated voltage to the second preset voltage, if the current accumulated voltage has reached the minimum requirement for accurate touch detection, the subsequent approaching process may be stopped, and in the subsequent integration, the voltages at the two ends of the integrating capacitor are accumulated by the current accumulated voltage until the voltages at the two ends of the integrating capacitor reach the touch threshold voltage, so that the subsequent approaching of the accumulated voltage is omitted in the process, and the operating cost of the system is further reduced.

According to the capacitance detection method provided by the embodiment of the application, the accumulated voltage of the integral capacitor in single integration is detected, and an adjusting signal is output according to the accumulated voltage; and then the equivalent capacitance of the integrating capacitor is adjusted according to the adjusting signal, so that the accumulated voltage of the integrating capacitor at the next time is adjusted, and the voltage of the integrating capacitor at the next time can be adaptively adjusted according to the voltage accumulated by the integrating capacitor at a single time. For example, when the voltage accumulated by the integration capacitor for a single time is small, the voltage accumulated by the integration capacitor for the next time is increased, so that the integration times can be reduced when the touch capacitor is small, and the touch event can be quickly detected; when the voltage accumulated by the integration capacitor for a single time is larger, the voltage accumulated by the integration capacitor for the next time is reduced, the phenomenon that the integration overflows or is saturated when the touch capacitor is larger is avoided, and the accurate detection of the touch event is realized.

Although the present application has been described with reference to the preferred embodiments, it is to be understood that the present application is not limited to the disclosed embodiments, but rather, the present application is intended to cover various modifications, equivalents and alternatives falling within the spirit and scope of the present application.

Claims

1. A capacitance detection circuit, comprising:

the integrating circuit comprises a comparator and an integrating capacitor, and the integrating capacitor is connected between the input end and the output end of the comparator;

the voltage detection circuit is connected with the integrating circuit and used for detecting the accumulated voltage of the integrating capacitor in single integration and outputting an adjusting signal according to the accumulated voltage;

and the capacitance adjusting circuit is connected with the voltage detection circuit and the integrating circuit and is used for adjusting the equivalent capacitance of the integrating capacitor according to the adjusting signal so as to adjust the accumulated voltage of the next integration of the integrating capacitor.

2. The capacitance detection circuit of claim 1, wherein the adjustment signal comprises a first adjustment signal and a second adjustment signal;

the voltage detection circuit is used for outputting the first adjusting signal when the accumulated voltage is smaller than a first preset threshold voltage; the capacitance adjusting circuit is used for reducing the equivalent capacitance of the integrating capacitor according to the first adjusting signal so as to increase the accumulated voltage of the next integration of the integrating capacitor;

the voltage detection circuit is further used for outputting the second adjusting signal when the accumulated voltage is greater than a second preset threshold voltage; the capacitance adjusting circuit is further used for increasing the equivalent capacitance of the integrating capacitor according to the second adjusting signal so as to reduce the accumulated voltage of the next integration of the integrating capacitor;

wherein the first preset threshold voltage is less than or equal to the second preset threshold voltage.

3. The capacitance detection circuit of claim 2, wherein the capacitance adjustment circuit is further configured to decrease an equivalent capacitance of the integration capacitance according to the first adjustment signal to increase an accumulated voltage of a next integration of the integration capacitance to a first preset voltage; and increasing the equivalent capacitance of the integrating capacitor according to the second adjusting signal so as to reduce the accumulated voltage of the integrating capacitor at the next integration time to a second preset voltage.

4. The capacitance detection circuit of claim 2, wherein the voltage detection circuit is further configured to adjust a magnitude of the first adjustment signal or the second adjustment signal according to a magnitude of the accumulated voltage, wherein the first adjustment signal and the second adjustment signal are respectively in a positive correlation with the accumulated voltage;

the capacitance adjusting circuit is further used for reducing the equivalent capacitance of the integrating capacitor step by step when the first adjusting signal is reduced; the capacitance adjusting circuit is further configured to increase the equivalent capacitance of the integrating capacitor step by step when the second adjustment signal increases.

5. The capacitance detection circuit of claim 3, wherein the adjustment signal is a current adjustment signal;

the capacitance adjusting circuit comprises a transconductance amplifier, a first resistor and a second resistor, the first resistor is connected between a first input end and a second input end of the transconductance amplifier, the second resistor is connected between an output end of the transconductance amplifier and a first input end of the transconductance amplifier, one end of the integrating capacitor is connected to the second input end of the transconductance amplifier, the other end of the integrating capacitor is connected to an output end of the comparator, the first input end of the transconductance amplifier is further connected to an input end of the comparator, and a current input end of the transconductance amplifier is connected to the voltage detecting circuit to receive the current adjusting signal.

6. The capacitance detection circuit of claim 5, wherein the voltage detection circuit comprises:

the step length detection circuit is connected to the output end of the comparator and used for detecting the accumulated voltage of the single integration of the integration capacitor;

the quantizer is connected with the step length detection circuit and used for outputting a voltage regulation signal according to the accumulated voltage;

and the current control circuit is connected with the quantizer and used for outputting a current adjusting signal to the transconductance amplifier according to the voltage adjusting signal.

7. The capacitance detection circuit according to any one of claims 1 to 6, further comprising:

the first switch capacitor circuit, one end is used for receiving the input signal, another end is connected to the said integrating circuit; and

a second switched capacitor circuit, one end of which is used for receiving the input signal and the other end of which is connected to the integrating circuit;

the first switched capacitor circuit and the second switched capacitor circuit have opposite integration directions, and the first switched capacitor circuit is also used for connecting a detection pin; wherein the magnitude of the accumulated voltage is positively correlated with the capacitance change of the detection pin.

8. The capacitance detection circuit of claim 7, wherein the first switched-capacitor circuit comprises a first capacitor, a first switch, a second switch, a third switch, a fourth switch, and a fifth switch; the first end of the first capacitor is connected to one end of the first switch, the other end of the first switch is connected to one end of the second switch, the other end of the second switch is used for receiving the input signal, the first end of the first capacitor is grounded through the third switch, the second end of the first capacitor is connected to the integrating circuit through the fourth capacitor, the second end of the first capacitor is grounded through the fifth switch, and a connection node of the first switch and the second switch is used for connecting a detection pin;

the second switch capacitor circuit comprises a second capacitor, a third capacitor, a sixth switch, a seventh switch and an eighth switch; one end of the sixth switch is used for receiving the input signal, the other end of the sixth switch is connected to one end of the seventh switch, the other end of the seventh switch is connected to one end of the eighth switch, the other end of the eighth switch is connected to the integrating circuit, the first end of the second capacitor is connected between the seventh switch and the eighth switch, the second end of the second capacitor is grounded, and the first end of the third capacitor is connected between the sixth switch and the seventh switch, and the second end of the third capacitor is grounded.

9. An integrated circuit comprising a capacitance detection circuit according to any one of claims 1 to 8.

10. An electronic device comprising a device body and the integrated circuit according to claim 9 provided in the device body.

11. A capacitance detection method applied to the capacitance detection circuit according to any one of claims 1 to 8, comprising:

detecting the accumulated voltage of the single integration of the integration capacitor, and outputting an adjusting signal according to the accumulated voltage; and

and adjusting the equivalent capacitance of the integrating capacitor according to the adjusting signal so as to adjust the accumulated voltage of the next integration of the integrating capacitor.

12. The capacitance detection method of claim 11, wherein the adjustment signal comprises a first adjustment signal and a second adjustment signal; the outputting of the adjustment signal according to the accumulated voltage includes:

outputting the first adjusting signal when the accumulated voltage is smaller than a first preset threshold voltage; or outputting the second adjusting signal when the accumulated voltage is greater than a second preset threshold voltage, wherein the first preset threshold voltage is less than or equal to the second preset threshold voltage;

the adjusting the equivalent capacitance of the integrating capacitor according to the adjusting signal to adjust the accumulated voltage of the integrating capacitor for the next integration includes:

reducing the equivalent capacitance of the integrating capacitor according to the first adjusting signal to increase the accumulated voltage of the integrating capacitor at the next integration; or increasing the equivalent capacitance of the integrating capacitor according to the second adjusting signal to reduce the accumulated voltage of the integrating capacitor in the next integration.