Detection circuit and steering wheel alarm device

Abstract

The application relates to a detection circuit and a steering wheel alarm device. The circuit comprises M first shielding modules, a second shielding module and a capacitance detection module; the i-th first shielding module is connected with the i-th sensing electrode and the i-th end of the capacitance detection module respectively, the second shielding module is connected with the M+1-th end of the capacitance detection module and a shielding electrode respectively; the capacitance detection module is used for transmitting a first initial voltage signal to the M first shielding modules and transmitting a second initial voltage signal to the second shielding module; the first shielding module is used for generating a first voltage signal transmitted to the corresponding sensing electrode based on the first initial voltage signal; the second shielding module is used for generating a second voltage signal transmitted to the shielding electrode based on the second initial voltage signal; and the capacitance detection module is further used for receiving current signals from the sensing electrodes through the first shielding modules; and based on the current signals, a capacitance signal is output.

Description

Technical Field

[0001] This application relates to the field of circuit technology, and in particular to a detection circuit and a steering wheel alarm device. Background Technology

[0002] With the rapid development of circuit technology, Hand-Off Detection (HOD) technology has emerged and is now used in vehicle steering wheels. To ensure high accuracy and reliability in the implementation of HOD technology, it is first necessary to ensure that the capacitive sensing chip can detect accurate touch data. Utility Model Content

[0003] Therefore, it is necessary to provide a detection circuit and a steering wheel alarm device that can improve the accuracy of the capacitance signal detected by the capacitance detection module.

[0004] In a first aspect, embodiments of this application provide a detection circuit, the circuit comprising:

[0005] M first shielding modules, second shielding modules, and capacitance detection modules, where M is an integer greater than or equal to 1;

[0006] The first shielding module is connected to the first sensing electrode and the first terminal of the capacitance detection module respectively, i=1,…,M; the second shielding module is connected to the (M+1)th terminal of the capacitance detection module and the shielding electrode respectively.

[0007] The capacitance detection module is used to transmit the first initial voltage signal to M first shielding modules and the second initial voltage signal to the second shielding module;

[0008] The first shielding module is used to generate a first voltage signal that is transmitted to the corresponding sensing electrode based on the first initial voltage signal;

[0009] The second shielding module is used to generate a second voltage signal that is delivered to the shielding electrode based on the second initial voltage signal; the error between the voltage value of the first voltage signal and the voltage value of the second voltage signal is less than or equal to a preset threshold.

[0010] The capacitance detection module is also used to receive current signals from each sensing electrode through each first shielding module; and to output capacitance signals based on each current signal.

[0011] In one exemplary embodiment, the first shielding module includes a first resistor and a first capacitor;

[0012] The first capacitor and the first resistor are connected in parallel.

[0013] The capacitance of the first capacitor is greater than the capacitance of the sensing electrode.

[0014] In one exemplary embodiment, the ratio between the capacitance value of the first capacitor and the capacitance value of the sensing electrode is greater than or equal to 10.

[0015] In one exemplary embodiment, the second shielding module includes a second resistor and a second capacitor;

[0016] The second capacitor is connected in parallel with the second resistor;

[0017] The capacitance of the second capacitor is greater than that of the shielding electrode.

[0018] In one exemplary embodiment, the ratio between the capacitance value of the second capacitor and the capacitance value of the sensing electrode is greater than or equal to 10.

[0019] In an exemplary embodiment, when M is 1, the capacitance detection module includes a signal generation unit, a first driving unit, a second driving unit, and a detection unit.

[0020] The signal generation unit is connected to the first end of the first driving unit and the first end of the second driving unit respectively; the second end of the first driving unit is connected to the third end of the first driving unit and the first end of the first shielding module respectively; and the target end of the first driving unit is connected to the detection unit.

[0021] The second end of the second drive unit is connected to the third end of the second drive unit and the first end of the second shielding module, respectively.

[0022] A signal generation unit is used to generate a third initial voltage signal; the third initial voltage signal is then transmitted to the first driving unit and the second driving unit respectively.

[0023] The first driving unit is used to generate a first initial voltage signal based on a third initial voltage signal, and to transmit the first initial voltage signal to a first shielding module; to receive a current signal from the sensing electrode through the first shielding module; and to transmit the current signal to the detection unit.

[0024] The second driving unit is used to generate a second initial voltage signal based on the third initial voltage signal and to transmit the second initial voltage signal to the second shielding module;

[0025] The detection unit is used to output a capacitance signal based on the current signal.

[0026] In one exemplary embodiment, the detection unit includes a current-to-voltage converter, an analog-to-digital converter, and a data processor;

[0027] The current-voltage converter is connected to the target terminal of the first drive unit and the first terminal of the analog-to-digital converter, respectively; the second terminal of the analog-to-digital converter is connected to the data processor, and the data processor is connected to the control module.

[0028] A current-to-voltage converter is used to convert a current signal into a third voltage signal;

[0029] An analog-to-digital converter is used to convert a third voltage signal from analog to digital to obtain a digital voltage signal.

[0030] A data processor is used to process digital voltage signals to obtain capacitance signals.

[0031] In an exemplary embodiment, when M is greater than 1, the capacitance detection module includes a signal generation unit, M first driving units, a second driving unit, and a detection unit.

[0032] The signal generation unit is connected to the first end of each of the M first driving units and the first end of the second driving unit respectively; the second end of the i-th first driving unit is connected to the third end of the i-th first driving unit and the first end of the i-th first shielding module respectively; the target ends of the M first driving units are connected to the detection unit respectively; and the second end of the second driving unit is connected to the third end of the second driving unit and the first end of the second shielding module respectively.

[0033] A signal generation unit is used to generate a third initial voltage signal; the third initial voltage signal is then transmitted to M first driving units and second driving units respectively.

[0034] Each first driving unit is used to generate a first initial voltage signal based on a third initial voltage signal, receive a current signal from the corresponding sensing electrode through a corresponding first shielding module, and transmit the current signal to the detection unit.

[0035] The second driving unit is used to generate a second initial voltage signal based on the third initial voltage signal;

[0036] The detection unit is used to output a capacitance signal based on the current signal.

[0037] In one exemplary embodiment, the detection unit includes a data selector, a current-to-voltage converter, an analog-to-digital converter, and a data processor;

[0038] The data selector is connected to the target terminal of each first drive unit and the first terminal of the current-to-voltage converter, respectively; the two ends of the analog-to-digital converter are connected to the second terminal of the current-to-voltage converter and the data processor, respectively; the data processor is connected to the control module.

[0039] A data selector is used to transmit current signals from the corresponding sensing electrodes to a current-to-voltage converter based on a first preset timing sequence.

[0040] A current-to-voltage converter is used to convert a current signal into a third voltage signal;

[0041] An analog-to-digital converter is used to convert a third voltage signal from analog to digital to obtain a digital voltage signal.

[0042] A data processor is used to process digital voltage signals to obtain capacitance signals.

[0043] Secondly, embodiments of this application provide a steering wheel alarm device, the device including a control module, an alarm module, and a detection circuit, M sensing electrodes, and a shielding electrode as described in any of the first aspects of embodiments of this application;

[0044] The control module is connected to the M+2 terminal of the capacitance detection module and the alarm module, respectively.

[0045] The control module is used to control the alarm module to issue an alarm signal when the capacitance change corresponding to the capacitance signal is less than the capacitance threshold.

[0046] The aforementioned detection circuit includes M first shielding modules, second shielding modules, and a capacitance detection module. By setting a first shielding module between the capacitance detection module and the sensing electrode, and setting a second shielding module between the capacitance detection module and the shielding electrode, the error between the voltage value of the first voltage signal output to the sensing electrode and the voltage value of the second voltage signal output to the shielding electrode can be minimized. This avoids the accumulation of charge in the coupling capacitor between the sensing electrode and the shielding electrode, ensuring that the coupling capacitor does not affect the detection accuracy of the capacitance detection module. In other words, it improves the accuracy of the capacitance signal detected by the capacitance detection module. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of a structure in which a coupling capacitor is formed between a sensing electrode and a shielding electrode.

[0049] Figure 2 This is a schematic diagram of a detection circuit provided in an embodiment of this application;

[0050] Figure 3 This is a schematic diagram of another detection circuit provided in an embodiment of this application;

[0051] Figure 4This is a schematic diagram of another detection circuit provided in an embodiment of this application;

[0052] Figure 5 This is a schematic diagram of a steering wheel alarm device provided in an embodiment of this application. Detailed Implementation

[0053] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0054] Unless otherwise defined, 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 is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0055] It is understood that the terms "first," "second," etc., 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. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0056] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0057] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0058] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0059] As described in the background section, HOD technology applied to vehicle steering wheels has already emerged. For example... Figure 1As shown, the sensing electrode 102 in the vehicle steering wheel can form a capacitive circuit with the driver's hand placed on the steering wheel. Specifically, different capacitance changes occur on the sensing electrode 102 when the driver's hand touches the steering wheel and when the driver's hand leaves the steering wheel. The capacitance detection chip outputs a capacitance signal based on these capacitance changes, which can be used to determine whether the driver is holding the steering wheel. The vehicle steering wheel also contains a heating wire. To prevent the electric field generated by the heating wire when energized from interfering with the capacitance value Csense of the sensing electrode 102, a shielding electrode 104 is used to mitigate the influence of the electric field from the heating wire. However, a coupling capacitance Cm also exists between the sensing electrode 102 and the shielding electrode 104. During the operation of the capacitance detection chip, the sensing electrode 102 frequently needs to be charged and discharged, which causes changes in the capacitance value Cm between the capacitance value Csense' of the sensing electrode 102 and the capacitance value Cshield' of the shielding electrode. Obviously, this leads to a decrease in the accuracy of capacitance detection.

[0060] Based on the aforementioned technical issues, research has revealed that by incorporating a voltage follower module and using the output signal from the sensing electrode as its input signal, the voltage value of the output signal from the voltage follower module to the shielding electrode can have a very small error compared to the voltage value of the output signal from the sensing electrode; that is, there is almost no voltage difference between the sensing electrode and the shielding electrode. Consequently, the charge on the coupling capacitor between the sensing electrode and the shielding electrode remains close to zero during capacitance detection, effectively shielding this coupling capacitor and thus improving the accuracy of the capacitance signal detected by the capacitance detection module.

[0061] The above is the core idea of ​​this application. The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0062] like Figure 2 As shown, one embodiment of the detection circuit includes:

[0063] M first shielding modules 202, second shielding modules 204, and capacitance detection modules 206, where M is an integer greater than or equal to 1.

[0064] The first shielding module 202 is connected to the i-th sensing electrode and the i-th end of the capacitance detection module 206, respectively, i=1,…,M. The second shielding module 204 is connected to the M+1-th end of the capacitance detection module 206 and the shielding electrode, respectively.

[0065] The capacitance detection module 206 is used to transmit the first initial voltage signal to M first shielding modules 202 and the second initial voltage signal to the second shielding module 204.

[0066] The first shielding module 202 is used to generate a first voltage signal that is delivered to the corresponding sensing electrode based on the first initial voltage signal.

[0067] The second shielding module 204 is used to generate a second voltage signal that is delivered to the shielding electrode based on the second initial voltage signal; the error between the voltage value of the first voltage signal and the voltage value of the second voltage signal is less than or equal to a preset threshold.

[0068] The capacitance detection module 206 is also used to receive current signals from each sensing electrode through each first shielding module 202; and output capacitance signals based on each current signal.

[0069] The first shielding module 202 is connected to the first sensing electrode and the first end of the capacitance detection module 206, respectively, indicating that there is a one-to-one correspondence between the first shielding module 202, the sensing electrode and the first end of the capacitance detection module 206.

[0070] The sensing electrode is used to sense the touch of an external human hand through its capacitance to ground. When a human hand touches the sensing electrode, the capacitance to ground of the sensing electrode changes.

[0071] The shielding electrode is used to isolate the electric field interference caused by the outside world to the sensing electrode, so that the capacitance to ground of the sensing electrode can only change when a touch event is applied to the sensing electrode.

[0072] Optionally, the sensing electrode and the shielding electrode can be located in the vehicle steering wheel. Alternatively, the sensing electrode and the shielding electrode can be located in the sensing layer electrode and the shielding layer electrode of the vehicle steering wheel, respectively.

[0073] The capacitance detection module 206 is used to detect changes in capacitance on the sensing electrode to determine whether a touch event has occurred on the sensing electrode. When the sensing electrode and the shielding electrode are located in the vehicle steering wheel, a touch event can be a person's hand placing on the vehicle steering wheel.

[0074] Optionally, the capacitance detection module 206 may include a capacitance detection chip.

[0075] The first shielding module 202 can also be used to isolate the first high-voltage signal transmitted from the sensing electrode to the capacitance detection module 206; the voltage value of the first high-voltage signal is greater than or equal to a first preset threshold.

[0076] The second shielding module 204 can also be used to isolate the second high-voltage signal transmitted from the shielding electrode to the capacitance detection module 206; the voltage value of the second high-voltage signal is greater than or equal to a second preset threshold.

[0077] In simple terms, the capacitance signal corresponds to the amount of capacitance change caused by a touch event acting on the sensing capacitor.

[0078] It is easy to understand that when a high-voltage signal is transmitted to the capacitance detection module 206, it may damage the capacitance detection module 206, making it difficult to guarantee the accuracy of the capacitance signal. Therefore, by setting the first shielding module 202 and the second shielding module 204 in the shielding circuit, the safety and reliability of the capacitance detection module 206 in high-voltage application scenarios can be ensured, thereby ensuring the accuracy and reliability of the capacitance signal detected by the capacitance detection module 206.

[0079] Optionally, the first preset threshold and the second preset threshold can be 16V, 32V or other voltage thresholds, respectively.

[0080] Since the first voltage signal is the voltage signal output to the sensing electrode and the second voltage signal is the voltage signal output to the shielding electrode, the error between the voltage values ​​of the first voltage signal and the second voltage signal is less than or equal to a preset threshold, meaning that the voltage difference between the voltage values ​​of the first voltage signal and the second voltage signal is extremely small, and the voltage difference between the sensing electrode and the shielding electrode can be regarded as 0.

[0081] It should be noted that, in order to ensure that the voltage difference between the sensing electrode and the shielding electrode can be regarded as 0, the preset threshold should be a sufficiently small threshold. This ensures that the coupling capacitance between the sensing electrode and the shielding electrode will not accumulate charge due to the voltage difference between them, and thus ensures that the coupling capacitance will not affect the accuracy of the capacitance signal obtained by the capacitance detection chip.

[0082] Optionally, if the error = voltage value of the first voltage signal - voltage value of the second voltage signal, then the preset threshold can be ±0.05V, ±0.1V, or other voltage thresholds.

[0083] For example, when the preset threshold is ±0.05V, the allowable voltage difference between the voltage values ​​of the first voltage signal and the second voltage signal is -0.05V to 0.05V.

[0084] For example, in order to ensure that the error between the first voltage signal and the second voltage signal is minimal, the voltage values ​​of the first initial voltage signal and the second initial voltage signal output by the capacitance detection module 206 can be the same, and the voltage waveforms can both be sinusoidal waveforms. Assuming that both the first initial voltage signal and the second initial voltage signal are represented as Vdrive, Vdrive can be expressed by the following formula:

[0085]

[0086] Where f is the frequency of the first initial voltage signal and the second initial voltage signal, and t is the time of the first initial voltage signal and the second initial voltage signal.

[0087] Optionally, the detection circuit provided in this application embodiment can be applied not only to vehicle steering wheels, but also to devices such as vehicle door handles.

[0088] It should be noted that applying the detection circuit to the vehicle steering wheel or vehicle door handle is merely an exemplary embodiment proposed for the purpose of explanation in this application. In specific implementation, since the detection circuit provided in this application can improve the accuracy of the capacitance signal detected by the capacitance detection module 206, the detection circuit provided in this application can be applied to any application scenario that requires shielding the coupling capacitor between the sensing electrode and the shielding electrode to ensure that the coupling capacitor does not affect the detection accuracy of the capacitance detection module 206. This application does not limit the application scenario of the detection circuit.

[0089] The aforementioned detection circuit includes M first shielding modules, second shielding modules, and a capacitance detection module. By setting a first shielding module between the capacitance detection module and the sensing electrode, and setting a second shielding module between the capacitance detection module and the shielding electrode, the error between the voltage value of the first voltage signal output to the sensing electrode and the voltage value of the second voltage signal output to the shielding electrode can be minimized. This avoids the accumulation of charge in the coupling capacitor between the sensing electrode and the shielding electrode, ensuring that the coupling capacitor does not affect the detection accuracy of the capacitance detection module. In other words, it improves the accuracy of the capacitance signal detected by the capacitance detection module.

[0090] In one exemplary embodiment, such as Figure 3 As shown, the first shielding module 202 includes a first resistor R1 and a first capacitor C1.

[0091] The first capacitor C1 is connected in parallel with the first resistor R1.

[0092] The capacitance of the first capacitor C1 is greater than the capacitance of the sensing electrode.

[0093] Wherein, the first capacitor C1 and the first resistor R1 are connected in parallel, meaning that the first end of the first resistor R1 is connected to the corresponding end of the capacitor detection module 206 and the first end of the first capacitor C1 respectively, and the second end of the first resistor R1 is connected to the corresponding sensing electrode and the second end of the first capacitor C1 respectively.

[0094] Optionally, the resistance value of the first resistor R1 can be greater than or equal to the first preset resistor. Optionally, the first preset resistor can be 4000Ω, 4700Ω, or other resistance values.

[0095] Optionally, the resistance value of the first resistor R1 can be determined by the current sinking capability of the capacitor detection module 206.

[0096] In one exemplary embodiment, the ratio between the capacitance value of the first capacitor C1 and the capacitance value of the sensing electrode is greater than or equal to 10.

[0097] For example, the capacitance value of the first capacitor C1 can be 10 times, 30 times, 50 times or other multiples of the capacitance value of the sensing electrode and the capacitance value of the shielding electrode, as long as the capacitance value of the first capacitor C1 is much greater than the capacitance value of the sensing electrode. This application does not limit this.

[0098] In this embodiment, the first shielding module includes a first resistor and a first capacitor, and the first resistor and the first capacitor are connected in parallel. Thus, the impedance effect of the first resistor in the shielding circuit can be effectively reduced by the first capacitor with a large capacitance value, ensuring that the first shielding module can isolate the high voltage signal from the sensing electrode while also ensuring that the detection circuit has high signal transmission efficiency.

[0099] In one exemplary embodiment, such as Figure 3 As shown, the second shielding module 204 includes a second resistor R2 and a second capacitor C2.

[0100] The second capacitor C2 is connected in parallel with the second resistor R2.

[0101] The capacitance of the second capacitor C2 is greater than that of the shielding electrode.

[0102] The second capacitor C2 and the second resistor R2 are connected in parallel, meaning that the first end of the second resistor R2 is connected to the corresponding end of the capacitor detection module 206 and the first end of the second capacitor C2, and the second end of the second resistor R2 is connected to the shielding electrode and the second end of the second capacitor C2.

[0103] Optionally, the resistance value of the second resistor R2 can be greater than or equal to the second preset resistor. Optionally, the second preset resistor can be 4000Ω, 4700Ω, or other resistance values.

[0104] Optionally, the resistance value of the second resistor R2 can be determined by the current sinking capability of the capacitor detection module 206.

[0105] It should be noted that, in order to ensure that the first resistor R1 can be used to isolate the high voltage signal transmitted from the sensing electrode to the capacitance detection module 206, and to ensure that the second resistor R2 can be used to isolate the high voltage signal transmitted from the shielding electrode to the capacitance detection module 206, the first preset resistor and the second preset resistor should each be a sufficiently large threshold value. This ensures that both the first resistor R1 and the second resistor R2 have sufficient isolation capability to isolate the high voltage signal, so as to ensure that the capacitance detection module 206 is not damaged by the high voltage signal.

[0106] In one exemplary embodiment, the ratio between the capacitance value of the second capacitor C2 and the capacitance value of the sensing electrode is greater than or equal to 10.

[0107] For example, the capacitance value of the second capacitor C2 can be 10 times, 30 times, 50 times or other multiples of the capacitance value of the sensing electrode and the capacitance value of the shielding electrode, as long as the capacitance value of the second capacitor C2 is much greater than the capacitance value of the shielding electrode. This application does not limit this.

[0108] In this embodiment, the second shielding module includes a second resistor and a second capacitor, and the second resistor and the second capacitor are connected in parallel. Thus, the impedance effect of the second resistor in the shielding circuit can be effectively reduced by the second capacitor with a large capacitance value, ensuring that the second shielding module can isolate the high voltage signal from the sensing electrode while also ensuring that the detection circuit has high signal transmission efficiency.

[0109] In an exemplary embodiment, when M is 1, the capacitance detection module 206 includes a signal generation unit 2062, a first driving unit 2064, a second driving unit 2066, and a detection unit 2068.

[0110] The signal generation unit 2062 is connected to the first end of the first driving unit 2064 and the first end of the second driving unit 2066 respectively; the second end of the first driving unit 2064 is connected to the third end of the first driving unit 2064 and the first end of the first shielding module 202 respectively; and the target end of the first driving unit 2064 is connected to the detection unit 2068.

[0111] The second end of the second driving unit 2066 is connected to the third end of the second driving unit 2066 and the first end of the second shielding module 204, respectively.

[0112] The signal generation unit 2062 is used to generate a third initial voltage signal; and to transmit the third initial voltage signal to the first driving unit 2064 and the second driving unit 2066 respectively.

[0113] The first driving unit 2064 is used to generate a first initial voltage signal based on a third initial voltage signal, and to transmit the first initial voltage signal to the first shielding module 202; to receive a current signal from the sensing electrode through the first shielding module 202; and to transmit the current signal to the detection unit 2068.

[0114] The second driving unit 2066 is used to generate a second initial voltage signal based on the third initial voltage signal and to transmit the second initial voltage signal to the second shielding module 204.

[0115] The detection unit 2068 is used to output a capacitance signal based on the current signal.

[0116] Among them, the signal generation unit 2062 can be a digital to analog converter (DAC).

[0117] Optionally, the first driving unit 2064 may include a first operational amplifier A1.

[0118] Optionally, the second driving unit 2066 may include a second operational amplifier A2.

[0119] Optionally, the third initial voltage signal can be a sinusoidal voltage signal. The frequency and time of the third initial voltage signal correspond to the frequency and time of the first initial voltage signal (or the second initial voltage signal), respectively.

[0120] The current signal from the sensing electrode refers to the signal fed back from the sensing electrode to the detection unit 2068 by the first shielding module 202 and the first driving unit 2064 under the action of the first voltage signal and the touch event.

[0121] In one exemplary embodiment, such as Figure 3 As shown, the first driving unit 2064 includes a first operational amplifier A1, and the second driving unit 2066 includes a second operational amplifier A2; the signal generation unit 2062 is connected to the non-inverting input terminal of the first operational amplifier A1 and the non-inverting input terminal of the second operational amplifier A2, respectively; the output terminal of the first operational amplifier A1 is connected to the inverting input terminal of the first operational amplifier A1 and the first terminal of the first shielding module 202, respectively; and the target terminal of the first operational amplifier A1 is connected to the detection unit 2068.

[0122] The output terminal of the second driving unit 2066 is connected to the inverting input terminal of the second driving unit 2066 and the first terminal of the second shielding module 204, respectively.

[0123] The target terminal of the first operational amplifier A1 can be any one of the output terminal of the first operational amplifier A1 (i.e., the second terminal of the first driving unit 2064), the positive power supply terminal, and the ground terminal.

[0124] In this embodiment, when M is 1, the capacitance detection module includes a signal generation unit, a first driving unit, a second driving unit, and a detection unit. Thus, the driving capability of the sensing electrode and the shielding electrode can be improved by the first driving unit and the second driving unit, respectively, thereby improving the accuracy of the capacitance signal detected by the capacitance detection module.

[0125] In one exemplary embodiment, such as Figure 3 As shown, the detection unit 2068 includes a current-to-voltage converter (I2V), an analog-to-digital converter (ADC), and a data processor (DSP).

[0126] The current-to-voltage converter I2V is connected to the target terminal of the first drive unit 2064 and the first terminal of the analog-to-digital converter ADC, respectively; the second terminal of the analog-to-digital converter ADC is connected to the data processor DSP, and the data processor DSP is connected to the control module.

[0127] The I2V current-to-voltage converter is used to convert current signals into a third voltage signal.

[0128] An analog-to-digital converter (ADC) is used to convert a third voltage signal from analog to digital to obtain a digital voltage signal.

[0129] The data processor (DSP) is used to process digital voltage signals to obtain capacitance signals.

[0130] Among them, the current-to-voltage converter I2V can be a transimpedance amplifier (I2V).

[0131] Analog-to-Digital Converter (ADC) is a type of digital converter.

[0132] DSP stands for Digital Signal Processor.

[0133] Optionally, the control module may be a microcontroller unit (MCU).

[0134] In one exemplary embodiment, such as Figure 4 As shown, when M is greater than 1, the capacitance detection module 206 includes a signal generation unit 2062, M first driving units 2064 (2064-1, 2064-2, ...), a second driving unit 2066, and a detection unit 2068.

[0135] The signal generation unit 2062 is connected to the first end of each of the M first driving units 2064 and the first end of the second driving unit 2066, respectively; the second end of the i-th first driving unit 2064 is connected to the third end of the i-th first driving unit 2064 and the first end of the i-th first shielding module 202, respectively; the target ends of the M first driving units 2064 are connected to the detection unit 2068, respectively; and the second end of the second driving unit 2066 is connected to the third end of the second driving unit 2066 and the first end of the second shielding module 204, respectively.

[0136] The signal generation unit 2062 is used to generate a third initial voltage signal; and to transmit the third initial voltage signal to M first driving units 2064 and second driving units 2066 respectively.

[0137] Each first driving unit 2064 is used to generate a first initial voltage signal based on a third initial voltage signal, receive current signals from the corresponding sensing electrode through the corresponding first shielding module 202 among multiple first shielding modules 202 (202-1, 202-2...), and transmit the current signals to the detection unit 2068.

[0138] The second driving unit 2066 is used to generate a second initial voltage signal based on the third initial voltage signal.

[0139] The detection unit 2068 is used to output a capacitance signal based on the current signal.

[0140] The number of sensing electrodes corresponds to M. For example, if M=3, then the number of sensing electrodes is also 3.

[0141] Optionally, the resistance value of the first resistor R1 in different first shielding modules 202 can be different, and the resistance value of the first capacitor C1 in different first shielding modules 202 can also be different. For example Figure 4 As shown, the first resistor R1-1 included in the first shielding module 202-1 and the first resistor R1-2 included in the first shielding module 202-2 may have different resistance values. Similarly, the first capacitor C1-1 included in the first shielding module 202-1 and the first capacitor C1-2 included in the first shielding module 202-2 may also have different capacitance values.

[0142] Optionally, the first operational amplifier A1 in different first driving units 2064 can also be different operational amplifiers. For example Figure 4 As shown, the first operational amplifier A1-1 included in the first driving unit 2064-1 may be a different operational amplifier from the first operational amplifier A1-2 included in the first driving unit 2064-2.

[0143] For example, when the detection circuit provided in this application embodiment is applied to a vehicle steering wheel and M is greater than 1, multiple sensing electrodes can be distributed at different angular positions on the vehicle steering wheel. For example, when M=3, the vehicle steering wheel is provided with a total of 3 sensing electrodes, which are evenly distributed along the circumference of the vehicle steering wheel. Each sensing electrode corresponds to a 120° position. For example, the 3 sensing electrodes can correspond to 0°~120°, 120°~240°, and 240°~360° positions respectively to achieve full circumferential coverage.

[0144] In this embodiment, when M is greater than 1, the first driving unit, the first shielding module, and the sensing electrode are in one-to-one correspondence, and only one detection unit is needed in the capacitance detection module of the detection circuit to realize the detection of multiple sensing electrodes. Thus, the applicability and flexibility of the detection circuit to vehicle steering wheels with different numbers of sensing electrodes are improved.

[0145] In one exemplary embodiment, such as Figure 4 As shown, the detection unit 2068 includes a data selector MUX, a current-to-voltage converter I2V, an analog-to-digital converter ADC, and a data processor DSP.

[0146] The data selector MUX is connected to the target terminal of each first drive unit 2064 and the first terminal of the current-to-voltage converter I2V, respectively; the two ends of the analog-to-digital converter ADC are connected to the second terminal of the current-to-voltage converter I2V and the data processor DSP, respectively, and the data processor DSP is connected to the control module.

[0147] The data selector MUX is used to transmit the current signal from the corresponding sensing electrode to the current-to-voltage converter I2V based on a first preset timing sequence.

[0148] The I2V current-to-voltage converter is used to convert current signals into a third voltage signal.

[0149] An analog-to-digital converter (ADC) is used to convert a third voltage signal from analog to digital to obtain a digital voltage signal.

[0150] The data processor (DSP) is used to process digital voltage signals to obtain capacitance signals.

[0151] Among them, the data selector MUX, or Multiplexer, is abbreviated as MUX in English.

[0152] The first preset timing sequence can be manually set in advance to achieve time-division detection of multiple sensing electrodes.

[0153] In this embodiment, when M is greater than 1, the detection unit 2068 includes a data selector, a current-to-voltage converter, an analog-to-digital converter, and a data processor. Thus, the data selector can transmit the current signal from the corresponding sensing electrode to the current-to-voltage converter based on a first preset timing sequence, realizing time-division detection of multiple sensing electrodes. Based on this, not only can the accuracy of the capacitance signal detected by the capacitance detection module be improved, but also the detection precision of the capacitance detection module can be improved.

[0154] The circuit structure of the above detection circuit is illustrated below with a detailed embodiment, assuming M is 1. See below for details. Figure 3 The detection circuit includes a first shielding module 202, a second shielding module 204, and a capacitance detection module 206;

[0155] The first shielding module 202 includes a first resistor R1 and a first capacitor C1; the capacitance value of the first capacitor C1 is greater than the capacitance value of the sensing electrode; the second shielding module 204 includes a second resistor R2 and a second capacitor C2; the capacitance value of the second capacitor C2 is greater than the capacitance value of the shielding electrode; the capacitance detection module 206 includes a signal generation unit 2062, a first operational amplifier A1, a second operational amplifier A2, a current-to-voltage converter I2V, an analog-to-digital converter ADC, and a data processor DSP.

[0156] The first end of the first resistor R1 is connected to the inverting input terminal and the output terminal of the first operational amplifier A1 and the first end of the first capacitor C1, respectively. The second end of the first resistor R1 is connected to the sensing electrode and the second end of the first capacitor C1, respectively. The first end of the second resistor R2 is connected to the inverting input terminal and the output terminal of the second operational amplifier A2 and the first end of the second capacitor C2, respectively. The second end of the second resistor R2 is connected to the shielding electrode and the second end of the second capacitor C2, respectively.

[0157] The signal generation unit 2062 is connected to the non-inverting input terminal of the first operational amplifier A1 and the non-inverting input terminal of the second operational amplifier A2, respectively; the positive or negative power supply terminal of the first operational amplifier A1 is connected to the first terminal of the current-to-voltage converter I2V; the first terminal of the analog-to-digital converter ADC is connected to the second terminal of the current-to-voltage converter I2V, the second terminal of the analog-to-digital converter ADC is connected to the data processor DSP, and the data processor DSP is connected to the control module.

[0158] The signal generation unit 2062 is used to generate a third initial voltage signal; and to send the third initial voltage signal to the first operational amplifier A1 and the second operational amplifier A2 respectively.

[0159] The first operational amplifier A1 is used to generate a first initial voltage signal based on a third initial voltage signal, and to send the first initial voltage signal to a parallel circuit formed by connecting the first resistor R1 and the first capacitor C1; to receive a current signal from the sensing electrode through the parallel circuit formed by connecting the first resistor R1 and the first capacitor C1; and to send the current signal to the current-to-voltage converter I2V.

[0160] The second operational amplifier A2 is used to generate a second initial voltage signal based on the third initial voltage signal, and to send the second initial voltage signal to the parallel circuit formed by the second resistor R2 and the second capacitor C2.

[0161] The parallel circuit formed by the first resistor R1 and the first capacitor C1 is used to generate a first voltage signal that is delivered to the corresponding sensing electrode based on the first initial voltage signal.

[0162] The parallel circuit formed by the second resistor R2 and the second capacitor C2 is used to generate a second voltage signal that is delivered to the shielding electrode based on the second initial voltage signal; the error between the voltage value of the first voltage signal and the voltage value of the second voltage signal is less than or equal to a preset threshold.

[0163] A current-to-voltage converter I2V is used to convert the current signal from the first operational amplifier A1 into a third voltage signal;

[0164] An analog-to-digital converter (ADC) is used to convert a third voltage signal from analog to digital to obtain a digital voltage signal.

[0165] The data processor (DSP) is used to process digital voltage signals to obtain capacitance signals.

[0166] For example, the first voltage signal is denoted as Vsense, the second voltage signal is denoted as Vshield, the sensing electrode is denoted as Csense (which, for ease of understanding, can also be expressed mathematically as the capacitance value of the sensing electrode), and the shielding electrode is denoted as Cshield (which, for ease of understanding, can also be expressed mathematically as the capacitance value of the shielding electrode). Figure 3 As shown, the first shielding module 202 includes a first resistor R1 and a first capacitor C1 connected in parallel, and the second shielding module 204 includes a second resistor R2 and a second capacitor C2 connected in parallel. The voltage values ​​of both the first initial voltage signal and the second initial voltage signal are expressed as follows: Based on the circuit principle and the specific circuit connection relationship provided in the embodiments of this application, the first voltage signal Vsense transmitted to the sensing electrode Csense can be expressed by the following formula (1):

[0167] (1)

[0168] Similarly, the second voltage signal Vshield transmitted to the shielding electrode Cshield at this time can be expressed by the following formula (2):

[0169] (2)

[0170] When the capacitance C of the first capacitor C1 is much larger than the capacitance of the sensing electrode Csense (for example, the ratio between the two is greater than or equal to 10), and the capacitance of the first capacitor C1 is much larger than the capacitance of the shielding electrode Cshield, it is easy to understand that the constant parts of the first voltage signal Vsense and the second voltage signal Vshield are close to 1, that is, the following formulas (3) and (4) can be obtained:

[0171] (3)

[0172] (4)

[0173] Based on this, when the capacitance value of the first capacitor C1 is much greater than the capacitance value of the sensing electrode Csense, and the capacitance value of the first capacitor C1 is much greater than the capacitance value of the shielding electrode Cshield, the first voltage signal Vsense can be expressed by the following formula (5), which is easy to understand based on formulas (1) and (3):

[0174] (5)

[0175] Similarly, based on formulas (2) and (4), the second voltage signal Vshield transmitted to the shielding electrode Cshield can be expressed by the following formula (6):

[0176] (6)

[0177] Obviously, based on formulas (5) and (6), it can be seen that the first voltage signal transmitted to the sensing electrode Csense and the second voltage signal transmitted to the shielding electrode Cshield can maintain the same voltage value. Based on this, the charge of the coupling capacitor between the sensing electrode Csense and the shielding electrode Cshield is always close to 0 during the capacitance detection process. Therefore, it is equivalent to achieving the shielding effect of this coupling capacitor, thereby improving the accuracy of the capacitance signal detected by the capacitance detection module 206.

[0178] In this embodiment, based on the specific circuit connection relationship between the first shielding module, the second shielding module, and the capacitance detection module included in the detection circuit, it is possible to ensure that the high voltage signal from the sensing electrode and the high voltage signal from the shielding electrode will not damage the capacitance detection module. At the same time, it is possible to ensure that the voltage between the sensing electrode and the shielding electrode is dynamically consistent, so that the coupling capacitance between the sensing electrode and the shielding electrode will not affect the touch data detection accuracy of the capacitance detection module. In other words, it is possible to improve the accuracy of the touch data detected by the capacitance detection module.

[0179] It is understood that the detection circuit described above can also take other forms, and is not limited to the forms mentioned in the above embodiments, as long as it can achieve the function of improving the accuracy of the capacitance signal detected by the capacitance detection module.

[0180] In one exemplary embodiment, such as Figure 5 As shown, a steering wheel alarm device is also proposed, which includes a control module 502, an alarm module 504, and a detection circuit 20 as described in any of the above detection circuit embodiments, M sensing electrodes Csense and shielding electrodes Cshield.

[0181] The control module 502 is connected to the M+2 terminal of the capacitance detection module and the alarm module 504, respectively.

[0182] The control module 502 is used to control the alarm module 504 to issue an alarm signal when the capacitance change corresponding to the capacitance signal is less than the capacitance threshold.

[0183] In an exemplary embodiment, the control module 502 is specifically configured to control the alarm module 504 to issue an alarm signal when the duration of the capacitance change corresponding to the capacitance signal being less than the capacitance threshold reaches a time threshold.

[0184] In an exemplary embodiment, the control module 502 is specifically configured to control the alarm module 504 to issue an alarm signal when the duration of the capacitor signal being less than the voltage threshold reaches a time threshold.

[0185] In an exemplary embodiment, when M is greater than 1, the control module 502 is further configured to determine the position of at least one sensing electrode affected by the touch event based on the capacitance signal.

[0186] The solution provided by the steering wheel warning device is similar to the solution described in the detection circuit above. Therefore, the specific limitations of one or more steering wheel warning device embodiments provided below can be found in the limitations of the detection circuit above, and will not be repeated here.

[0187] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0188] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0189] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A detection circuit, characterized in that, The circuit includes: M first shielding modules, second shielding modules, and capacitance detection modules, where M is an integer greater than or equal to 1; The first shielding module is connected to the i-th sensing electrode and the i-th end of the capacitance detection module, i=1,…,M respectively; the second shielding module is connected to the M+1-th end of the capacitance detection module and the shielding electrode respectively. The capacitance detection module is used to transmit a first initial voltage signal to M of the first shielding modules and a second initial voltage signal to the second shielding module; The first shielding module is used to generate a first voltage signal that is transmitted to the corresponding sensing electrode based on the first initial voltage signal; The second shielding module is used to generate a second voltage signal that is supplied to the shielding electrode based on the second initial voltage signal; the error between the voltage value of the first voltage signal and the voltage value of the second voltage signal is less than or equal to a preset threshold. The capacitance detection module is further configured to receive current signals from each of the sensing electrodes through each of the first shielding modules; and output capacitance signals based on each of the current signals.

2. The circuit according to claim 1, characterized in that, The first shielding module includes a first resistor and a first capacitor; The first capacitor is connected in parallel with the first resistor; The capacitance value of the first capacitor is greater than the capacitance value of the sensing electrode.

3. The circuit according to claim 2, characterized in that, The ratio between the capacitance value of the first capacitor and the capacitance value of the sensing electrode is greater than or equal to 10.

4. The circuit according to claim 1, characterized in that, The second shielding module includes a second resistor and a second capacitor; The second capacitor is connected in parallel with the second resistor; The capacitance value of the second capacitor is greater than the capacitance value of the shielding electrode.

5. The circuit according to claim 4, characterized in that, The ratio between the capacitance value of the second capacitor and the capacitance value of the sensing electrode is greater than or equal to 10.

6. The circuit according to claim 1, characterized in that, When M is 1, the capacitance detection module includes a signal generation unit, a first driving unit, a second driving unit, and a detection unit; The signal generation unit is connected to the first end of the first driving unit and the first end of the second driving unit respectively; the second end of the first driving unit is connected to the third end of the first driving unit and the first end of the first shielding module respectively; and the target end of the first driving unit is connected to the detection unit. The second end of the second driving unit is connected to the third end of the second driving unit and the first end of the second shielding module, respectively. The signal generation unit is used to generate a third initial voltage signal; The third initial voltage signal is transmitted to the first driving unit and the second driving unit respectively; The first driving unit is configured to generate the first initial voltage signal based on the third initial voltage signal, and to transmit the first initial voltage signal to the first shielding module; The current signal from the sensing electrode is received through the first shielding module; The current signal is transmitted to the detection unit; The second driving unit is used to generate the second initial voltage signal based on the third initial voltage signal, and to transmit the second initial voltage signal to the second shielding module; The detection unit is used to output the capacitance signal based on the current signal.

7. The circuit according to claim 6, characterized in that, The detection unit includes a current-to-voltage converter, an analog-to-digital converter, and a data processor; The current-to-voltage converter is connected to the target terminal of the first driving unit and the first terminal of the analog-to-digital converter, respectively; the second terminal of the analog-to-digital converter is connected to the data processor, and the data processor is connected to the control module. The current-to-voltage converter is used to convert the current signal into a third voltage signal; The analog-to-digital converter is used to perform analog-to-digital conversion on the third voltage signal to obtain a digital voltage signal; The data processor is used to process the digital voltage signal to obtain the capacitance signal.

8. The circuit according to claim 1, characterized in that, When M is greater than 1, the capacitance detection module includes a signal generation unit, M first driving units, a second driving unit, and a detection unit; The signal generation unit is connected to the first end of each of the M first driving units and the first end of the second driving unit; the second end of the i-th first driving unit is connected to the third end of the i-th first driving unit and the first end of the i-th first shielding module; the target ends of the M first driving units are connected to the detection unit; and the second end of the second driving unit is connected to the third end of the second driving unit and the first end of the second shielding module. The signal generation unit is used to generate a third initial voltage signal; and to transmit the third initial voltage signal to M first driving units and second driving units respectively; Each of the first driving units is configured to generate the first initial voltage signal based on the third initial voltage signal, and receive the current signal from the corresponding sensing electrode through the corresponding first shielding module; The current signal is transmitted to the detection unit; The second driving unit is used to generate the second initial voltage signal based on the third initial voltage signal; The detection unit is used to output the capacitance signal based on the current signal.

9. The circuit according to claim 8, characterized in that, The detection unit includes a data selector, a current-to-voltage converter, an analog-to-digital converter, and a data processor; The data selector is connected to the target terminal of each of the first driving units and the first terminal of the current-to-voltage converter, respectively; the two ends of the analog-to-digital converter are connected to the second terminal of the current-to-voltage converter and the data processor, respectively; the data processor is connected to the control module. The data selector is used to transmit the current signal from the corresponding sensing electrode to the current-voltage converter based on a first preset timing sequence. The current-to-voltage converter is used to convert the current signal into a third voltage signal; The analog-to-digital converter is used to perform analog-to-digital conversion on the third voltage signal to obtain a digital voltage signal; The data processor is used to process the digital voltage signal to obtain the capacitance signal.

10. A steering wheel alarm device, characterized in that, The device includes a control module, an alarm module, a detection circuit as described in any one of claims 1 to 9, M sensing electrodes, and a shielding electrode; The control module is connected to the M+2 terminal of the capacitance detection module and the alarm module, respectively. The control module is used to control the alarm module to issue an alarm signal when the capacitance change corresponding to the capacitance signal is less than the capacitance threshold.

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