Capacitance detection system using active shielding and operation method thereof

Abstract

A capacitance detection system includes a plurality of detection electrodes, an insulating layer, and a single active shield metal. The single active shielding metal has an overlapping region with each of the plurality of detection electrodes. The insulating layer is disposed between the single active shielding metal and the plurality of detection electrodes. When one of the plurality of detection electrodes is driven using a drive signal, the other plurality of detection electrodes are grounded or receive an active shield signal, while the single active shield metal receives the active shield signal.

Description

Technical Field

[0001] The present invention relates to a capacitance detection, and more particularly to a capacitance detection system using active shielding and an operation method thereof. Background Art

[0002] Please refer to Figure 1 As shown, it is a known capacitance detection system having a plurality of detection channels, shown as channels 1 to N. To improve the ability to resist noise, a corresponding shielding layer 15 is disposed for each channel, and the plurality of shielding layers 15 are separated from each other. An insulating layer 13 is disposed between the electrode layer 11 (including channels 1 to N) and the plurality of shielding layers 15. During operation, each shielding layer 15 receives a shielding signal corresponding to the charging signal of the channel above it.

[0003] However, since it is necessary to independently transmit the shielding signal to different shielding layers 15, a plurality of signal lines are required to be respectively connected to the plurality of shielding layers 15, resulting in high circuit complexity and increasing the manufacturing difficulty, especially when the configuration space is limited. Moreover, the calculation load of the processing unit for generating the driving signal and the shielding signal and processing the detection signal is also high.

[0004] Therefore, it is actually required to provide a capacitance detection system with a simple manufacturing process and capable of effectively forming noise shielding. Summary of the Invention

[0005] In view of this, the present invention provides a capacitance detection system and an operation method thereof that configure a single shielding metal to simultaneously shield a plurality of detection channels.

[0006] The present invention also provides a capacitance detection system and an operation method thereof for sequential detection. When one of the channels is being detected, the other channels are grounded for shielding or actively shielded, and at the same time, the single shielding metal is actively shielded, so as to achieve the purpose of reducing the wiring complexity.

[0007] The present invention also provides a capacitance detection system and an operation method thereof for synchronous detection. By configuring an operational amplifier and an input capacitor between the detection chip and the single shielding metal, noise interference is reduced, and active shielding covering a plurality of detection channels is achieved with the same shielding metal.

[0008] The present invention provides a capacitance detection system including an electrode layer and a single shielding metal. The electrode layer includes a first electrode and a second electrode. The first electrode is connected to a first detection line for receiving a first driving signal. The second electrode is connected to a second detection line for receiving a second driving signal. The single shielding metal is used to receive a shielding signal and has overlapping regions with the first electrode and the second electrode respectively.

[0009] The present invention also provides a capacitance detection system including a detection chip, an input capacitor, an electrode layer, a single shielding metal, and an operational amplifier. The input capacitor is connected to the detection chip. The electrode layer includes a first electrode and a second electrode. The first electrode is configured to receive a first driving signal from the detection chip through a first detection line. The second electrode is configured to receive a second driving signal from the detection chip through a second detection line. The single shielding metal is configured to receive a shielding signal from the detection chip and has overlapping regions with the first electrode and the second electrode respectively. The operational amplifier is connected between the single shielding metal and the input capacitor.

[0010] The present invention also provides an operation method for a capacitance detection system. The capacitance detection system includes a first electrode, a second electrode, and a single shielding metal having overlapping regions with the first electrode and the second electrode respectively. The operation method includes: charging the first electrode and the single shielding metal during a first period, wherein the first electrode and the single shielding metal have the same charging waveform during the first period; and charging the second electrode and the single shielding metal during a second period, wherein the second electrode and the single shielding metal have the same charging waveform during the second period.

[0011] In order to make the above and other objects, features, and advantages of the present invention more obvious, the following will be described in detail in conjunction with the accompanying drawings. In addition, in the description of the present invention, the same components are denoted by the same reference numerals, which are hereby stated in advance. Description of the Drawings

[0012] Figure 1 is a schematic diagram of a known multi-channel capacitance detection system;

[0013] Figure 2 is a schematic diagram of a capacitance detection device using active shielding according to an embodiment of the present invention;

[0014] Figure 3 is Figure 2 the signal timing diagram of the operation of the capacitance detection device;

[0015] Figure 4 is Figure 2 the signal timing diagram of another operation of the capacitance detection device;

[0016] Figure 5 is a schematic diagram of a capacitance detection system according to an embodiment of the present invention;

[0017] Figure 6 is Figure 5 the signal timing diagram of parallel detection and using active shielding of the capacitance detection system;

[0018] Figure 7is a flowchart of an operation method of a capacitance detection system according to an embodiment of the present invention; and

[0019] Figure 8 is Figure 2 another signal timing diagram of the operation of a capacitance detection device.

[0020] Description of Reference Numerals

[0021] 200 Capacitance detection device

[0022] 21 Electrode layer

[0023] 23 Insulating layer

[0024] 25 Shielding metal

[0025] 500 Capacitance detection system

[0026] 51 Detection chip

[0027] 53 Input capacitance

[0028] 55 Operational amplifier

[0029] L1 to LN Detection lines

[0030] E1 to EN Detection electrodes

[0031] S1 to SN Drive signals

[0032] S-AS Shielding signal Detailed Description of the Invention

[0033] An object of the present invention is to provide a hand detection using a capacitance detection system with active shielding, which can be applied, for example, to a vehicle steering wheel having the ability to detect whether a hand leaves the steering wheel (i.e., hand-off detection), but is not limited thereto. The active shielding of the present invention shields multiple detection electrodes with a single shielding metal to simplify the complexity of the circuit configuration and improve the noise resistance. The shielding object of the active shielding is, for example, a heater, but is not limited to a heater, as long as it is an element that generates noise to the detection electrodes described later.

[0034] Please refer to Figure 2 as shown, which is a schematic diagram of a capacitance detection device 200 according to an embodiment of the present invention. The capacitance detection device 200 includes an electrode layer 21, an insulating layer 23, and a single shielding metal 25. The insulating layer 23 includes any suitable insulating material or printed dielectric inks, and there is no specific limitation. In one embodiment, the electrode layer 21 and the single shielding metal 25 are printed on two opposite surfaces of the insulating layer 23 (such as Figure 2 the upper and lower surfaces), but is not limited thereto.

[0035] The electrode layer 21 includes a plurality of detection electrodes, such as shown as a first electrode E1, a second electrode E2, a third electrode E3, …, and an Nth electrode EN. The number of detection electrodes is determined according to actual requirements. Each detection electrode is formed, for example, by printed conductive inks, but is not limited thereto. The first electrode E1 receives a first driving signal S1 from a detection chip 51 (refer to Figure 5 ); the second electrode E2 receives a second driving signal S2 from the detection chip 51 through a second detection line L2; and so on. In one embodiment, the driving signals S1 to SN are charging currents to form charging waveforms for the respective detection electrodes E1 to EN. The charging waveforms (such as Cgp1 to CgpN described later) are different in the contact state and the non-contact state, so that a processor (such as a microprocessor, an application-specific integrated circuit, a programmable logic circuit) in the detection chip 51 can perform hand off detection according to the respective changes of the charging waveforms Cgp1 to CgpN. For example, when changing from the contact state to the non-contact state, or from the non-contact state to the contact state, the charging time will change.

[0036] A single shielding metal 25 receives a shielding signal S-AS (such as a charging current) from the detection chip 51, and the single shielding metal 25 has overlapping regions with the plurality of detection electrodes E1 to EN of the electrode layer 21 respectively. The so-called "single" shielding metal in the present invention means that the part overlapping with the plurality of detection electrodes E1 to EN (such as overlapping in the Figure 2 up and down directions) belongs to an entire metal. The single shielding metal 25 is formed, for example, by printed conductive inks, and can be formed into a mesh shape or a sheet shape, without specific limitation.

[0037] The following describes an operation method of the capacitance detection device 200, and takes two of the plurality of detection electrodes E1 to EN, such as the first electrode E1 and the second electrode E2, as an example for description.

[0038] Please refer to Figure 3 shown, which is Figure 2A signal timing diagram of an operation of a capacitance detection device 200. The first driving signal S1 charges the first electrode E1 during the first period St1 and has a charging waveform Cgp1 and a charging time Cgt1, such as a voltage rising period. The second driving signal S2 charges the second electrode E2 during the second period St2 that is later than the first period St1 and has a charging waveform Cgp2 and a charging time Cgt2, such as a voltage rising period. For the relative touch state (such as a hand on the steering wheel) and the non-contact state (such as a hand off the steering wheel), the charging waveforms Cgp1 and Cgp2 are different, resulting in different charging times Cgt1 and Cgt2. The processor in the detection chip 51 can perform a hand-off detection based on the change in the charging time, but is not limited thereto. The shielding signal S-AS is coupled to the single shielding metal 25 during the first period St1 and the second period St2 to form an active shield.

[0039] To form an active shield, the charging waveform Cgp-as of the shielding signal S-AS for the single shielding metal 25 preferably corresponds (equal or in a ratio) to the charging waveforms Cgp1, Cgp2... CgpN for each detection period, i.e., St1, St2... StN. It can be understood that when the first electrode E1 and the second electrode E2 have the same area, they have the same capacitance to ground. Therefore, the same driving signal can obtain the same charging waveform. The same charging waveforms of the first electrode E1 and the second electrode E2, for example, refer to having the same frequency, amplitude, and phase.

[0040] However, when the areas of the first electrode E1 and the second electrode E2 are different (e.g., E1 < E2), two methods can be used to achieve the active shield of the present invention.

[0041] In the first method, the charging waveform Cgp1 of the first driving signal S1 for the first electrode E1 during the first period St1 is different from the charging waveform Cgp2 of the second driving signal S2 for the second electrode E2 during the second period St2. For example, the driving signals S1 and S2 are the same so that the first electrode E1 charges faster. Therefore, the shielding signal S-AS has different charging waveforms Cgp-as for the single shielding metal 25 corresponding to the first period St1 and the second period St2, respectively, to correspond / match the charging waveform Cgp1 of the first electrode E1 and the charging waveform Cgp2 of the second electrode E2. For example, the single shielding metal 25 charges faster during the first period St1.

[0042] In the second method, the charging waveform Cgp1 of the first driving signal S1 to the first electrode E1 in the first period St1 is the same as the charging waveform Cgp2 of the second driving signal S2 to the second electrode E2 in the second period St2. For example, the driving signals S1 and S2 are different (e.g., S1 < S2). For example, an electrode with a larger area uses a larger charging current while an electrode with a smaller area uses a smaller charging current. Therefore, the shielding signal S-AS has the same charging waveform Cgp-as for the single shielding metal 25 corresponding to the first period St1 and the second period St2 to respectively correspond to / match the charging waveform Cgp1 of the first electrode E1 and the charging waveform Cgp2 of the second electrode E2.

[0043] Please refer to Figure 3 again. In the present invention, when a certain detection electrode (or called a sensor) is performing detection, other detection electrodes can be used as shielding electrodes at the same time. In one embodiment, in the first period St1, the second electrode E2 (and all other detection electrodes E3 to EN, if any) is grounded to form a ground shielding; in the second period St2, the first electrode E1 (and all other detection electrodes E3 to EN, if any) is grounded to form a ground shielding; and so on.

[0044] In another embodiment, when a certain detection electrode is performing detection, only the adjacent electrodes of the certain detection electrode are used as shielding electrodes while other detection electrodes are not used as shielding electrodes. For example, when the second electrode E2 is performing detection, only the detection electrodes E1 and E3 are grounded while other detection electrodes E4 to EN (if any) do not need to be grounded, and can be, for example, floating or maintained at a specific DC voltage.

[0045] Please refer to Figure 4As shown, in another embodiment, during the first period St1, the second electrode (and all other detection electrodes E3 to EN, if any) is coupled to the second shielding signal (e.g., S2 = S - AS2 < S - AS, because the single shielding metal 25 is larger than the second electrode E2) to form an active shield. Preferably, by controlling the driving parameters (e.g., driving current, but not limited to), the second electrode E2 (and all other detection electrodes E3 to EN, if any) has the same charging waveform as the first electrode E1; during the second period St2, the first electrode E1 (and all other detection electrodes E3 to EN, if any) is coupled to the first shielding signal (e.g., S1 = S - AS2 < S - AS, because the single shielding metal 25 is larger than the first electrode E1) to form an active shield. Preferably, by controlling the driving parameters (e.g., driving current, but not limited to), the first electrode E1 (and all other detection electrodes E3 to EN, if any) has the same charging waveform as the second electrode E2. Preferably, in this embodiment, during all detection periods St1 to StN, the charging waveforms of all detection electrodes E1 to EN and the single shielding metal 25 are the same, i.e., Cgp1 = Cgp2 =... = CgpN = Cgp - as, to achieve a good active shielding effect. In one embodiment, the capacitance detection device 200 is configured such that all detection electrodes E1 to EN have the same area. In another embodiment, when at least some of the detection electrodes E1 to EN of the capacitance detection device 200 have different areas (i.e., different capacitance values to ground), the corresponding driving signals (e.g., driving current) can be adjusted so that the charging waveforms are the same as each other.

[0046] In another embodiment, when a certain detection electrode is performing detection, only the adjacent electrodes of the certain detection electrode are used as active shielding electrodes while the other detection electrodes can be floating or grounded or maintained at a specific DC voltage. For example, when the second electrode E2 is performing detection, only the detection electrodes E1 and E3 are actively shielded while the other detection electrodes E4 to EN are floating or grounded shielded or maintained at a specific DC voltage, as Figure 8 shown, the detection electrodes E4 to EN are grounded shielded.

[0047] Please refer to Figure 5 shown, which is a schematic diagram of the capacitance detection system 500 according to an embodiment of the present invention, including a detection chip 51 connected to Figure 2 the capacitance detection device 200 to provide driving signals S1 to SN and shielding signal S - AS to the capacitance detection device 200 through detection lines L1 to LN and signal line Ls - as. The detection chip 51 (e.g., the processor therein) also determines the contact state according to the charging time (e.g., Figure 3 shown Cgt1, Cgt2... CgtN). Figure 5 The signals S1 to SN and S - AS in Figure 2signals S1 to SN and S-AS.

[0048] In an embodiment where the input resistance of the detection chip 51 is relatively large, the detection result is susceptible to noise interference. At this time, the capacitance detection system 500 further includes an input capacitor 53 and an operational amplifier 55 connected between the detection chip 51 and the single shielding metal 25 to reduce noise interference. In one embodiment, the capacitance value of the input capacitor 53 is selected to be equal to the larger of the capacitance values to ground of the first electrode E1 and the second electrode E2 (and all other detection electrodes E3 to EN, if any), preferably the detection electrode with the largest capacitance value, so as to be able to cover the active shielding ability for all the detection electrodes E1 to EN. In the present invention, the operational amplifier 55 is used as a voltage follower.

[0049] Figure 3 and Figure 4 show the sequential detection performed by the capacitance detection device 200 and the system 500 of the present invention. Please refer to Figure 6 shown, which shows the signal timing diagram of the parallel detection performed using the capacitance detection device 200 and the system 500 of the present invention. In this embodiment, the first drive signal S1, the second drive signal S2 (and all other drive signals S3 to SN, if any), and the shielding signal S-AS are respectively used to charge the first electrode E1, the second electrode E2 (and all other detection electrodes E3 to EN, if any), and the single shielding metal 25 during each detection period St1 to StN. Preferably, the charging waveforms Cgp1, Cgp2... CgpN and Cgp-as with respect to the first electrode E1, the second electrode E2 (and all other detection electrodes E3 to EN, if any), and the single shielding metal 25 are the same as each other to achieve a good active shielding effect. For example, as described above, it can be achieved by making all the detection electrodes E1 to EN have the same area, or by controlling the drive parameters.

[0050] Please refer to Figure 7 shown, which is a method of operating the capacitance detection device 200 and the capacitance detection system 500 according to an embodiment of the present invention, including the following steps: charging the first electrode and the single shielding metal during a first period, wherein the first electrode and the single shielding metal have the same charging waveform during the first period (step S71); and charging the second electrode and the single shielding metal during a second period, wherein the second electrode and the single shielding metal have the same charging waveform during the second period (step S72).

[0051] Please refer again to Figure 3 , Figure 4 and Figure 6 shown, whether performing sequential driving ( Figure 3 and Figure 4 ) or parallel driving (Figure 6 ) During the first period St1, the detection chip 51 charges the first electrode E1 with the first driving signal S1 and charges the single shielding metal 25 with the shielding signal S-AS. To achieve a good active shielding effect, the first electrode E1 and the single shielding metal 25 have the same charging waveform during the first period St1. For example, Cgp1 = Cgp-as (or Cgt1 = Cgt-as to have the same charging phase). During the second period St2, the detection chip 51 charges the second electrode E2 with the second driving signal S2 and charges the single shielding metal 25 with the shielding signal S-AS. To achieve a good active shielding effect, the second electrode E2 and the single shielding metal 25 have the same charging waveform during the second period St2. For example, Cgp2 = Cgp-as (or Cgt2 = Cgt-as to have the same charging phase).

[0052] The above operating modes of the first electrode E1 and the second electrode E2 can be applied to other detection electrodes E3 to EN and are shown in Figure 3 、 Figure 4 and Figure 6 Therefore, it will not be elaborated here.

[0053] One implementation of the capacitance detection device and system according to an embodiment of the present invention is a self-capacitance detection device and system.

[0054] It must be noted that although the single shielding metal 25 is shown to have a rectangular shape in the drawings of this case, the present invention is not limited thereto. In other embodiments, the single shielding metal 25 can have any shape as long as it has an overlapping area with each of the plurality of detection electrodes E1 to EN respectively. For example, it has a larger area at the overlap of each detection electrode and is only connected by at least one narrow area (such as forming a connection bridge) between the detection electrodes.

[0055] In summary, the known capacitance detection system is configured with multiple detection channels and shielding layers to resist noise interference, and thus has a complex circuit and a high computing load. Therefore, the present invention further provides a capacitance detection device using active shielding (refer to Figure 2 ), a capacitance detection system (refer to Figure 5 ), and an operating method thereof (refer to Figure 7 ). The present invention reduces the circuit complexity by configuring a single shielding metal. Other detection electrodes other than the currently operating detection electrodes are grounded shielded or actively shielded to further improve the signal-to-noise ratio and increase the detection accuracy.

[0056] Although the present invention has been disclosed by the foregoing examples, it is not intended to limit the present invention. Any person having ordinary knowledge and skills in the technical field to which the present invention pertains may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the appended claims.

Claims

1. A capacitance detection system, the capacitance detection system comprising: An electrode layer, the electrode layer comprising: A first electrode, the first electrode is connected to a first detection line for receiving a first driving signal; and A second electrode, the second electrode is connected to a second detection line for receiving a second driving signal; and A single shielding metal is used for receiving a shielding signal and has overlapping areas with the first electrode and the second electrode respectively.

2. The capacitance detection system according to claim 1, further comprising: The insulating layer is disposed between the electrode layer and the single shielding metal.

3. The capacitance detection system according to claim 1, wherein: The first driving signal charges the first electrode during a first period. The second driving signal charges the second electrode in a second period later than the first period, and The shielding signal is coupled to the single shielding metal during the first period and the second period to form active shielding.

4. The capacitance detection system according to claim 3, wherein: The first electrode and the second electrode have different areas, The charging waveform of the first electrode in the first period is different from that of the second electrode in the second period, and The shielding signal has different charging waveforms for the single shielding metal in response to the first period and the second period.

5. The capacitance detection system according to claim 3, wherein: The first electrode and the second electrode have different areas, The charging waveform of the first electrode in the first period is the same as that of the second electrode in the second period, and The shielding signal has the same charging waveform for the single shielding metal in response to the first period and the second period.

6. The capacitance detection system according to claim 3, wherein: During the first period, the second electrode is grounded, and During the second period, the first electrode is grounded.

7. The capacitance detection system according to claim 3, wherein: During the first period, the second electrode is coupled to a second shielding signal to form active shielding, and During the second period, the first electrode is coupled to a first shielding signal to form active shielding.

8. The capacitance detection system according to claim 7, wherein: In the first period and the second period, charging waveforms of the first electrode, the second electrode, and the single shielding metal are the same.

9. The capacitance detection system according to claim 8, wherein: The first electrode and the second electrode have different areas, The first driving signal and the second driving signal are respectively a first charging current and a second charging current, and The first charging current is different from the second charging current so that the charging waveforms are the same.

10. The capacitance detection system according to claim 1, further comprising an input capacitor and an operational amplifier coupled to the single shielding metal, wherein: The capacitance value of the input capacitor is equal to the larger capacitance value to ground of the first electrode and the second electrode.

11. A capacitance detection system, the capacitance detection system comprising: Detection chip; An input capacitor connected to the detection chip; An electrode layer, the electrode layer comprising: a first electrode, the first electrode being used to receive a first driving signal from the detection chip through a first detection line; and a second electrode, the second electrode being used to receive a second driving signal from the detection chip through a second detection line; A single shielding metal, the single shielding metal is used to receive a shielding signal from the detection chip and has overlapping areas with the first electrode and the second electrode respectively; as well as An operational amplifier is connected between the single shielding metal and the input capacitor.

12. The capacitance detection system according to claim 11, wherein: The capacitance value of the input capacitor is equal to the larger capacitance value to ground of the first electrode and the second electrode.

13. The capacitance detection system according to claim 11, wherein: The first driving signal, the second driving signal and the shielding signal respectively charge the first electrode, the second electrode and the single shielding metal in each detection period.

14. The capacitance detection system according to claim 13, wherein: In each of the detection periods, the charging waveforms of the first electrode, the second electrode, and the single shielding metal are the same.

15. The capacitance detection system according to claim 11, wherein: The operational amplifier is used as a voltage follower. 16 . The capacitance detection system according to claim 11 , further comprising an insulating layer disposed between the electrode layer and the single shielding metal.

17. A method for operating a capacitance detection system, the capacitance detection system comprising a first electrode, a second electrode, and a single shielding metal having overlapping areas with the first electrode and the second electrode, the method comprising: During a first period, the first electrode and the single shielding metal are charged, wherein: The first electrode and the single shielding metal have the same charging waveform during the first period; as well as The second electrode and the single shielding metal are charged during a second period, wherein the second electrode and the single shielding metal have the same charging waveform during the second period.

18. The operating method according to claim 17, further comprising: charging the second electrode during the first period so that the second electrode and the first electrode have the same charging waveform; and The first electrode is charged in the second period so that the first electrode and the second electrode have the same charging waveform.

19. The operating method according to claim 17, further comprising: During the first period, the second electrode is grounded; and The first electrode is grounded during the second period.

20. The operating method according to claim 17, wherein: The single shielding metal is connected to the detection chip through an input capacitor and an operational amplifier, and The capacitance value of the input capacitor is equal to the larger capacitance value to ground of the first electrode and the second electrode.

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