Differential mutual capacitance detection circuit, method, chip and device

Abstract

The present invention discloses a differential mutual capacitance detection circuit, method, chip and device, which relates to the field of mutual capacitance detection. Excitation signals are applied to at least two sensing elements independently, and a working voltage is applied to the in-phase input terminal of an amplifier; one of the sensing elements is selected as a first sensing element, and the output voltage of the amplifier, the capacitance value of the feedback capacitor and the mutual capacitance value of the first sensing element are obtained; the mutual capacitance difference between two sensing elements with similar distances is calculated according to the excitation signal, the capacitance value of the feedback capacitor, the working voltage of the in-phase input terminal of the amplifier and the output voltage of the amplifier; the mutual capacitance value of other sensing elements is calculated according to the mutual capacitance value of the first sensing element and the mutual capacitance difference. The present invention can detect the mutual capacitance value of the sensing element and increase the proportion of the effective mutual capacitance value of the sensing element.

Description

Technical Field

[0001] This invention relates to the field of mutual capacitance detection, and in particular to a differential mutual capacitance detection circuit, method, chip, and device. Background Technology

[0002] Mutual capacitance detection technology has a wide range of applications, such as detecting finger touch on touchscreens or sensing fingerprint patterns during fingerprint recognition. Figure 1 This is a schematic diagram of an array of sensing elements based on the mutual capacitance detection principle in the prior art. Since the induced electric field between the driving electrode TX and the sensing electrode RX in the sensing element 1 weakens as the conductor approaches, the distance between the conductors can be determined by detecting the change in the mutual capacitance value of the sensing element 1.

[0003] The mutual capacitance of a sensing element includes intrinsic mutual capacitance and effective mutual capacitance. The intrinsic mutual capacitance is the mutual capacitance unaffected by the conductor, while the effective mutual capacitance varies with the distance from the conductor. Increasing the proportion of effective mutual capacitance in the sensing element can increase the amplification factor of the output signal of the detection circuit and reduce the requirements for the dynamic range of the subsequent analog-to-digital converter. Since the effective mutual capacitance of the sensing element is variable, increasing its proportion requires considering how to reduce the intrinsic mutual capacitance of the sensing element.

[0004] Existing technologies primarily involve incorporating a base capacitor within the detection circuit. This base capacitor's value is used to offset the intrinsic mutual capacitance of the sensing element, thereby increasing the proportion of effective mutual capacitance. However, incorporating a base capacitor in the detection circuit requires additional chip area, increasing chip cost. Furthermore, since the base capacitor is fixed to the detection circuit, adjusting its value necessitates additional adjustment circuitry, making the base capacitor value difficult to adjust and limiting the chip's application range. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a differential mutual capacitance detection circuit, which can detect the mutual capacitance value of sensing elements and increase the proportion of effective mutual capacitance value of sensing elements.

[0006] This invention also proposes a differential mutual capacitance detection method.

[0007] This invention also proposes a differential mutual capacitance detection chip.

[0008] This invention also proposes a differential mutual capacitance detection device.

[0009] In a first aspect, one embodiment of the present invention provides a differential mutual capacitance detection circuit: including an amplifier, a feedback capacitor and a first switch, and at least two sensing elements;

[0010] At least two sensing elements are connected in parallel and independently connected to the inverting input terminal of the amplifier; one end of the feedback capacitor is connected to the inverting input terminal of the amplifier, and the other end of the feedback capacitor is connected to the output terminal of the amplifier, forming a first feedback loop; one end of the first switch is connected to the inverting input terminal of the amplifier, and the other end of the first switch is connected to the output terminal of the amplifier, forming a second feedback loop.

[0011] A differential mutual capacitance detection circuit according to an embodiment of the present invention has at least the following beneficial effects:

[0012] 1. Capable of detecting the mutual capacitance value of each sensing element;

[0013] 2. The number of sensing elements is adjustable and easily expandable;

[0014] 3. It can increase the proportion of effective mutual capacitance of sensing elements through differential methods;

[0015] 4. No additional base capacitor is required, simplifying the structure of the detection circuit.

[0016] According to some embodiments of the present invention, a differential mutual capacitance detection circuit further includes a second switch, which is connected in series with a feedback capacitor and in parallel with a first switch.

[0017] By setting a second switch, a differential mutual capacitance detection circuit according to an embodiment of the present invention can perform summation calculation, thereby improving the signal-to-noise ratio of the output signal of the detection circuit.

[0018] Secondly, one embodiment of the present invention provides a differential mutual capacitance detection method, based on a differential mutual capacitance detection circuit, comprising the following steps:

[0019] Excitation signals are applied independently to at least two sensing elements, and a working voltage is applied to the non-inverting input of the amplifier;

[0020] Select one of the sensing elements as the first sensing element, and obtain the amplifier's output voltage, the capacitance value of the feedback capacitor, and the mutual capacitance value of the first sensing element;

[0021] Based on the excitation signal, the capacitance value of the feedback capacitor, the operating voltage of the amplifier's non-inverting input, and the amplifier's output voltage, calculate the mutual capacitance difference between two closely spaced sensing elements.

[0022] Calculate the mutual capacitance values ​​of the other sensing elements based on the mutual capacitance value and mutual capacitance difference of the first sensing element.

[0023] The differential mutual capacitance detection method of this invention has at least the following beneficial effects:

[0024] 1. Using a differential method, based on the mutual capacitance value of one sensing element, the mutual capacitance values ​​of other sensing elements can be detected sequentially;

[0025] 2. The intrinsic mutual capacitance values ​​of two sensing elements that are close to each other can cancel each other out, increasing the proportion of the effective mutual capacitance value of the sensing elements.

[0026] According to some embodiments of the present invention, a differential mutual capacitance detection method applies excitation signals of the same frequency and amplitude but opposite direction to two sensing elements that are close to each other.

[0027] By applying excitation signals of the same frequency and amplitude but opposite direction to two sensing elements that are close to each other, a differential mutual capacitance detection circuit according to an embodiment of the present invention can simplify calculations.

[0028] According to another embodiment of the present invention, a differential mutual capacitance detection method performs dual correlation sampling on the output voltage of the amplifier.

[0029] By performing dual correlation sampling on the amplifier's output voltage, a differential mutual capacitance detection circuit according to an embodiment of the present invention can eliminate the amplifier's mismatch voltage.

[0030] According to another embodiment of the present invention, a differential mutual capacitance detection method performs multiple summation calculations on the charge quantity of the differential mutual capacitance detection circuit.

[0031] Through cumulative calculation, a differential mutual capacitance detection circuit according to an embodiment of the present invention can increase the signal quantity output by the amplifier, improve the signal-to-noise ratio of the amplifier output signal, and reduce the accuracy requirements of the subsequent analog-to-digital converter.

[0032] Thirdly, one embodiment of the present invention provides a differential mutual capacitance detection chip, including a differential mutual capacitance detection circuit.

[0033] A differential mutual capacitance detection chip according to an embodiment of the present invention has at least the following beneficial effects:

[0034] 1. Capable of detecting the mutual capacitance value of sensing elements;

[0035] 2. The differential mutual capacitance detection circuit inside the chip does not require a base capacitor, which reduces the chip area and lowers the chip cost.

[0036] Fourthly, one embodiment of the present invention provides a differential mutual capacitance detection device, including a differential mutual capacitance detection chip.

[0037] A differential mutual capacitance detection device according to an embodiment of the present invention has at least the following beneficial effects:

[0038] 1. Capable of detecting the mutual capacitance value of sensing elements;

[0039] 2. The differential mutual capacitance detection chip inside the equipment does not require a built-in base capacitor, which reduces the equipment cost. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of a sensing element array based on the mutual capacitance detection principle in the prior art;

[0041] Figure 2 This is a schematic diagram of a specific embodiment of a differential mutual capacitance detection circuit according to an embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of another specific embodiment of a differential mutual capacitance detection circuit according to an embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram of another specific embodiment of a differential mutual capacitance detection circuit in this invention. Detailed Implementation

[0044] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0045] In the description of this invention, if a feature is referred to as "setting", "fixing", "connecting", or "installing" on another feature, it can be set, fixed, or connected directly to the other feature, or it can be set, fixed, connected, or installed indirectly on the other feature.

[0046] In the description of the embodiments of the present invention, the term "multiple" means two or more; the terms "first" and "second" should be understood as distinguishing technical features, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0047] Reference Figure 1 This diagram illustrates a sensing element array based on the mutual capacitance detection principle in the prior art. Figure 1As shown, the horizontally connected rhombuses represent the driving electrode TX, and the vertically connected rhombuses represent the sensing electrode RX. The intersection of the driving electrode TX and the sensing electrode RX forms the sensing element 1. The driving electrode TX and the sensing electrode RX constitute the two poles of the sensing element 1. When a conductor approaches the sensing element, it affects the coupling between the two electrodes near the conductor, thereby changing the mutual capacitance value of the sensing element between these two electrodes. Since the induced electric field between the driving electrode and the sensing electrode within the sensing element weakens as the conductor approaches, the distance of the conductor can be determined by detecting the change in the mutual capacitance value of the sensing element.

[0048] Example 1

[0049] Reference Figure 2 The diagram illustrates a schematic of a specific embodiment of a differential mutual capacitance detection circuit according to an embodiment of the present invention. Figure 2 As shown, the first sensing element 10 and the second sensing element 11 are connected in parallel and are independently connected to the inverting input terminal N of the amplifier; one end of the feedback capacitor C is connected to the inverting input terminal N of the amplifier, and the other end of the feedback capacitor C is connected to the output terminal V of the amplifier. O This forms the first feedback loop; one end of the first switch S1 is connected to the inverting input terminal N of the amplifier, and the other end of the first switch S1 is connected to the output terminal V of the amplifier. O This forms a second feedback loop. The mutual capacitance value C of the first sensing element 10 is... a Including intrinsic mutual capacitance value C Ma and effective mutual capacitance value C TMa The mutual capacitance value C of the second sensing element 11 b Including intrinsic mutual capacitance value C Mb and effective mutual capacitance value C TMb C TM The larger the value, the closer the conductor is to the sensing element. The driving electrode of the first sensing element 10 is TXa, and the driving electrode of the second sensing element 11 is TXb.

[0050] Reset phase

[0051] Close S1, apply voltage VTX1 to TXa, apply voltage VTX2 to TXb, and apply operating voltage VCM to the non-inverting input P of the amplifier.

[0052] The amplifier's inverting input N and output V O The voltages are reset to VCM, and the total charge of the detection circuit is:

[0053] Q1=(VCM-VTX1)·(C Ma -C TMa )+(VCM-VTX2)·(C Mb -C TMb(1)

[0054] Charge transfer stage

[0055] Disconnect S1, apply voltage VTX2 to TXa, and voltage VTX1 to TXb. Due to the virtual short-circuit characteristic of the amplifier input, the voltage at the inverting input N of the amplifier remains VCM, and the voltage at the output V... O The voltage is VOUT, and the capacitance of the feedback capacitor C is C. F The total charge of the detection circuit is:

[0056]

[0057] Based on the law of charge conservation, Q1 = Q2, we can calculate:

[0058]

[0059] Since the inductive elements have basically the same structure and the process deviation within a small range is also very small, the intrinsic mutual capacitance values ​​of inductive elements that are close to each other are very similar. The intrinsic mutual capacitance values ​​of the first inductive element 10 and the second inductive element 11 cancel each other out, and equation (3) can be simplified to:

[0060]

[0061] Due to the mutual capacitance value C of the first sensing element 10 a =C Ma -C TMa The mutual capacitance value C of the second sensing element 11 b =C Mb -C TMb Then the mutual capacitance difference between the first sensing element 10 and the second sensing element 11 is:

[0062]

[0063] Measuring the mutual capacitance value C of the first sensing element 10 a According to the measured C a And ΔC calculated by equation (5) ab The mutual capacitance value C of the second sensing element 11 was calculated. b .

[0064] In some other specific embodiments of a differential mutual capacitance detection circuit according to an example of the present invention, based on embodiment 1, the normalized mutual capacitance value C of the first sensing element 10 is preset. a Let x be any real number, and let ΔC be calculated from equation (5). ab The normalized mutual capacitance value C of the second sensing element 11 was calculated. b .

[0065] Example 2

[0066] Reference Figure 3 The diagram illustrates a schematic of another specific embodiment of a differential mutual capacitance detection circuit according to an embodiment of the present invention. Figure 3 As shown, based on Embodiment 1, a third sensing element 12 is added. The first sensing element 10, the second sensing element 11, and the third sensing element 12 are connected in parallel and are independently connected to the inverting input terminal N of the amplifier. One end of the feedback capacitor C is connected to the inverting input terminal N of the amplifier, and the other end of the feedback capacitor C is connected to the output terminal V of the amplifier. O This forms the first feedback loop; one end of the first switch S1 is connected to the inverting input terminal N of the amplifier, and the other end of the first switch S1 is connected to the output terminal V of the amplifier. O This forms a second feedback loop. The mutual capacitance value C of the first sensing element 10 is... a Including intrinsic mutual capacitance value C Ma and effective mutual capacitance value C TMa The mutual capacitance value C of the second sensing element 11 b Including intrinsic mutual capacitance value C Mb and effective mutual capacitance value C TMb The mutual capacitance value C of the third sensing element 12 c Including intrinsic mutual capacitance value C Mc and effective mutual capacitance value C TMc The driving electrode of the first sensing element 10 is TXa, the driving electrode of the second sensing element 11 is TXb, and the driving electrode of the third sensing element 12 is TXc.

[0067] First, following the steps of Example 1, based on the measured C a And ΔC calculated by equation (5) ab The mutual capacitance value C of the second sensing element 11 was calculated. b Then, disconnect the voltage inputs to TXa and TXb, and then perform the following steps:

[0068] Reset phase

[0069] When S1 is closed, voltage VTX2 is applied to TXb and voltage VTX3 is applied to TXc. The operating voltage of the non-inverting input terminal P of the amplifier remains VCM.

[0070] The amplifier's inverting input N and output V O The voltages are reset to VCM, and the total charge of the detection circuit is:

[0071] Q1=(VCM-VTX2)·(C Mb -C TMb )+(VCM-VTX3)·(C Mc-C TMc ) (6)

[0072] Charge transfer stage

[0073] Disconnect S1, apply voltage VTX3 to TXb, and voltage VTX2 to TXc. Due to the virtual short-circuit characteristic of the amplifier input, the voltage at the inverting input N of the amplifier remains VCM, and the voltage at the output V... O The voltage is VOUT, and the capacitance of the feedback capacitor C is C. F The total charge of the detection circuit is:

[0074]

[0075] Based on the law of charge conservation, Q1 = Q2, we can calculate:

[0076]

[0077] Since the intrinsic mutual capacitance values ​​of the closely spaced sensing elements are very similar, the intrinsic mutual capacitance values ​​of the second sensing element 11 and the third sensing element 12 cancel each other out, and equation (8) can be simplified to:

[0078]

[0079] Due to the mutual capacitance value C of the second sensing element 11 b =C Mb -C TMb The mutual capacitance value C of the third sensing element 12 c =C Mc -C TMc The difference in mutual capacitance between the second sensing element 11 and the third sensing element 12 is:

[0080]

[0081] The mutual capacitance value C of the second sensing element 11 is calculated. b And ΔC calculated by equation (10) bc The mutual capacitance value C of the third sensing element 12 was calculated. c .

[0082] In another specific embodiment of a differential mutual capacitance detection circuit according to an embodiment of the present invention, based on embodiment 1, the normalized mutual capacitance value C of the first sensing element 10 is preset. a The result is 0, based on the ΔC calculated from equation (5). ab The normalized mutual capacitance value C of the second sensing element 11 was calculated. b According to the normalized mutual capacitance value C of the second sensing element 11 b And ΔC calculated by equation (10) bcThe normalized mutual capacitance value C of the third sensing element 12 was calculated. c .

[0083] Example 3

[0084] In another specific embodiment of a differential mutual capacitance detection circuit according to an embodiment of the present invention, based on embodiment 1, the input voltages of TXa and TXb are in phase and have the same frequency and amplitude.

[0085] Reset phase

[0086] When S1 is closed, the input voltages of TXa and TXb are both 0V, and the operating voltage of the amplifier's non-inverting input terminal P remains VCM.

[0087] The amplifier's inverting input N and output V O The voltages are reset to VCM, and the total charge of the detection circuit is:

[0088] Q1 = VCM·(C Ma -C TMa )+VCM·(C Mb -C TMb (11)

[0089] Charge transfer stage

[0090] Disconnect S1, apply voltage -VTX to TXa, and voltage VTX to TXb. Due to the virtual short-circuit characteristic of the amplifier input, the voltage at the inverting input N of the amplifier remains VCM, and the voltage at the output V... O The voltage is VOUT, and the capacitance of the feedback capacitor C is C. F The total charge of the detection circuit is:

[0091]

[0092] Based on the law of charge conservation, Q1 = Q2, we can calculate:

[0093]

[0094] The intrinsic mutual capacitance values ​​of the first sensing element 10 and the second sensing element 11 cancel each other out, and equation (13) can be simplified to:

[0095]

[0096] Due to the mutual capacitance value C of the first sensing element 10 a =C Ma -C TMa The mutual capacitance value C of the second sensing element 11 b =C Mb -C TMbThen the mutual capacitance difference between the first sensing element 10 and the second sensing element 11 is:

[0097]

[0098] Measuring the mutual capacitance value C of the first sensing element 10 a According to the measured C a And ΔC calculated by equation (15) ab The mutual capacitance value C of the second sensing element 11 was calculated. b .

[0099] Example 4

[0100] In another specific embodiment of a differential mutual capacitance detection circuit according to an embodiment of the present invention, based on embodiment 1, since the amplifier has a mismatch voltage, the mutual capacitance difference will be affected by the mismatch voltage. This embodiment uses dual correlation sampling to eliminate the mismatch voltage of the amplifier.

[0101] Reset phase

[0102] When S1 is closed, voltage VTX1 is applied to TXa and voltage VTX2 is applied to TXb. The operating voltage of the non-inverting input terminal P of the amplifier remains VCM.

[0103] The amplifier's inverting input N and output V O The voltage is reset. Due to the mismatch voltage in the amplifier, the reset voltage is VCM1 (the sum of VCM and the mismatch voltage), which is the voltage obtained by sampling the amplifier's output terminal V. O The voltage is VOUT1 = VCM1, and the total charge of the detection circuit is:

[0104] Q1=(VCM1-VTX1)·(C Ma -C TMa )+(VCM1-VTX2)·(C Mb -C TMb (16)

[0105] Charge transfer stage

[0106] Disconnect S1, apply voltage VTX2 to TXa, and voltage VTX1 to TXb. Due to the virtual short-circuit characteristic of the amplifier input, the voltage at the inverting input N of the amplifier is VCM1, and the voltage at the output V... O The voltage is VOUT2, and the capacitance of the feedback capacitor C is C. F The total charge of the detection circuit is:

[0107]

[0108] Based on the law of charge conservation, Q1 = Q2, we can calculate:

[0109]

[0110] Subtracting the amplifier output voltages from the two samples, ΔVOUT=VOUT2-VOUT1, we get:

[0111]

[0112] The intrinsic mutual capacitance values ​​of the first sensing element 10 and the second sensing element 11 cancel each other out, and equation (19) can be simplified to:

[0113]

[0114] As can be seen from equation (20), this embodiment eliminates the amplifier's mismatch voltage through dual-correlated sampling.

[0115] Example 5

[0116] Reference Figure 4 The diagram illustrates a schematic of another specific embodiment of a differential mutual capacitance detection circuit according to an embodiment of the present invention. Figure 4 As shown, based on Embodiment 1, a second switch S2 is added. The second switch S2 is connected in series with the feedback capacitor C. One end of the feedback capacitor C is connected to the inverting input terminal N of the amplifier, and the other end of the feedback capacitor C is connected to one end of the second switch S2. The other end of the second switch S2 is connected to the output terminal V of the amplifier. O This forms the first feedback loop; one end of the first switch S1 is connected to the inverting input terminal N of the amplifier, and the other end of the first switch S1 is connected to the output terminal V of the amplifier. O This forms a second feedback loop. The mutual capacitance value C of the first sensing element 10 is... a Including intrinsic mutual capacitance value C Ma and effective mutual capacitance value C TMa The mutual capacitance value C of the second sensing element 11 b Including intrinsic mutual capacitance value C Mb and effective mutual capacitance value C TMb The driving electrode of the first sensing element 10 is TXa, and the driving electrode of the second sensing element 11 is TXb.

[0117] First reset phase

[0118] Close S1 and S2, apply voltage VTX1 to TXa, apply voltage VTX2 to TXb, and apply operating voltage VCM to the non-inverting input P of the amplifier.

[0119] The amplifier's inverting input N and output V O The voltages are reset to VCM, and the total charge of the detection circuit is:

[0120] Q1=(VCM-VTX1)·(C Ma -C TMa )+(VCM-VTX2)·(C Mb -C TMb ) (twenty one)

[0121] First charge transfer stage

[0122] With S1 open and S2 still closed, apply voltage VTX2 to TXa and voltage VTX1 to TXb. Due to the virtual short-circuit characteristic of the amplifier input, the voltage at the inverting input N of the amplifier remains VCM.

[0123] The change in charge of the first sensing element 10 is ΔQ Ma =(VTX1-VTX2)·(C Ma -C TMa The charge change of the second sensing element 11 is ΔQ. Mb =(VTX2-VTX1)·(C Mb -C TMb The change in charge of the first sensing element 10 and the second sensing element 11 is transferred to the feedback capacitor C, and the amount of charge stored in the feedback capacitor C is Q. CF1 =-(ΔQ) Ma +ΔQ Mb ),Right now:

[0124] Q CF1 =(VTX2-VTX1)·(C TMb -C TMa )+(VTX1-VTX2)·(C Mb -C Ma ) (twenty two)

[0125] Second reset phase

[0126] With S1 closed and S2 open, a voltage VTX1 is applied to TXa and a voltage VTX2 is applied to TXb. The charge stored in the feedback capacitor C remains unchanged. The total charge of the detection circuit is:

[0127] Q3=(VCM-VTX1)·(C Ma -C TMa )+(VCM-VTX2)·(C Mb -C TMb )+Q CF1 (twenty three)

[0128] Second charge transfer stage

[0129] Open S1, close S2, apply voltage VTX2 to TXa, and apply voltage VTX1 to TXb.

[0130] The change in charge of the first sensing element 10 is ΔQ Ma =(VTX1-VTX2)·(C Ma -C TMa The charge change of the second sensing element 11 is ΔQ. Mb =(VTX2-VTX1)·(C Mb -C TMb The change in charge of the first sensing element 10 and the second sensing element 11 is transferred to the feedback capacitor C, and the amount of charge stored in the feedback capacitor C is Q. CF2 =Q CF1 -(ΔQ Ma +ΔQ Mb ),Right now:

[0131] Q CF2 =2·(VTX2-VTX1)·(C TMb -C TMa )+2·(VTX1-VTX2)·(C Mb -C Ma ) (twenty four)

[0132] Repeat the steps of the second reset stage and the second charge transfer stage m times (m is a natural number) to obtain the amount of charge stored in the feedback capacitor C:

[0133]

[0134] Additionally, based on the capacitance C of the feedback capacitor C... F And the voltage value distributed across the feedback capacitor C, we get:

[0135] Q CF(m+2) =C F (VCM-VOUT) (26)

[0136] From equations (25) and (26), we obtain:

[0137]

[0138] The intrinsic mutual capacitance values ​​of the first sensing element 10 and the second sensing element 11 cancel each other out, and equation (27) can be simplified to:

[0139]

[0140] Due to the mutual capacitance value C of the first sensing element 10 a =C Ma -C TMa The mutual capacitance value C of the second sensing element 11 b =C Mb -C TMbThen the mutual capacitance difference between the first sensing element 10 and the second sensing element 11 is:

[0141]

[0142] From equations (28) and (29), it can be seen that by performing m summation calculations on the charge stored in the feedback capacitor C, the output V of the amplifier can be increased. O The voltage VOUT is increased, thereby improving the signal-to-noise ratio of the amplifier output signal and reducing the accuracy requirements of the subsequent analog-to-digital converter.

[0143] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features within the embodiments may be combined with one another unless there is a conflict.

Claims

1. A differential mutual capacitance detection method, characterized in that: A differential mutual capacitance detection circuit is applied to a circuit comprising an amplifier, a feedback capacitor, a first switch, and at least two sensing elements. The differential mutual capacitance detection circuit comprises: At least two of the inductive elements are connected in parallel to each other and are independently connected to the inverting input terminal of the amplifier; one end of the feedback capacitor is connected to the inverting input terminal of the amplifier, and the other end of the feedback capacitor is connected to the output terminal of the amplifier to form a first feedback loop; one end of the first switch is connected to the inverting input terminal of the amplifier, and the other end of the first switch is connected to the output terminal of the amplifier to form a second feedback loop; The differential mutual capacitance detection method comprises: Applying excitation signals to at least two of the sensing elements independently and respectively, and applying a working voltage to the in-phase input terminal of the amplifier; Selecting one of the sensing elements as a first sensing element, and obtaining an output voltage of the amplifier, a capacitance value of the feedback capacitor, and a mutual capacitance value of the first sensing element; According to the excitation signal, the capacitance value of the feedback capacitor, the working voltage applied to the in-phase input terminal of the amplifier and the output voltage of the amplifier, a mutual capacitance difference between two sensing elements with close distances is calculated; wherein the intrinsic mutual capacitance values ​​of the two sensing elements with close distances cancel each other out, so as to increase the proportion of the effective mutual capacitance values ​​of the two sensing elements with close distances; Mutual capacitance values ​​of other sensing elements are calculated according to the mutual capacitance value of the first sensing element and the mutual capacitance difference.

2. A differential mutual capacitance detection method according to claim 1, characterized in that: The differential mutual capacitance detection circuit further includes a second switch, which is connected in series with the feedback capacitor and in parallel with the first switch.

3. The differential mutual capacitance detection method according to claim 1, characterized in that: Apply excitation signals of the same frequency, same amplitude and opposite directions to the two sensing elements that are close to each other.

4. A differential mutual capacitance detection method according to claim 1 or 3, characterized in that: The output voltage of the amplifier is double-correlatedly sampled.

5. A differential mutual capacitance detection method according to claim 1 or 3, characterized in that: The charge amount of the differential mutual capacitance detection circuit is cumulatively calculated multiple times.

6. A differential mutual capacitance detection chip, characterized in that: The differential mutual capacitance detection chip includes a differential mutual capacitance detection circuit, and the differential mutual capacitance detection circuit includes: at least two sensing elements are connected in parallel and are independently connected to the inverting input terminal of the amplifier; one end of the feedback capacitor is connected to the inverting input terminal of the amplifier, and the other end of the feedback capacitor is connected to the output terminal of the amplifier to form a first feedback loop; one end of the first switch is connected to the inverting input terminal of the amplifier, and the other end of the first switch is connected to the output terminal of the amplifier to form a second feedback loop; the differential mutual capacitance detection chip performs the differential mutual capacitance detection method described in claim 1.

7. The differential mutual capacitance detection chip according to claim 6, characterized in that: The differential mutual capacitance detection circuit further includes a second switch, which is connected in series with the feedback capacitor and in parallel with the first switch.

8. A differential mutual capacitance detection device, characterized in that: It comprises the differential mutual capacitance detection chip as described in claim 6 or 7.

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