Nfc circuit with adjustable inductive distance and electronic device

Abstract

The application provides an NFC circuit with adjustable induction distance and an electronic device. The NFC circuit comprises an NFC coil, a grounding coil and a tuning circuit. The grounding coil is arranged outside the NFC coil and is used for generating an induction current based on NFC coil current excitation. The tuning circuit is arranged on the grounding coil and is used for adjusting the size of the induction current, thereby offsetting part of the electromagnetic signal of the NFC coil, i.e. reducing the field strength of the electromagnetic signal of the NFC coil, so that the induction range of the NFC coil is reduced to the required size. No adjustment is required for the front-end circuit of the NFC coil, no additional energy is consumed, and the loss, cost and board area can be reduced. In addition, the method can avoid the problem that a plurality of NFC devices (NFC coils) are mis-triggered simultaneously when a plurality of NFC coils are very close to each other in the coil position.

Description

Technical Field

[0001] This application belongs to the field of power electronics technology, and in particular relates to an NFC circuit and electronic device with adjustable sensing distance. Background Technology

[0002] In common Near Field Communication (NFC) applications, adjusting the sensing range of the NFC coil is mainly achieved through: adjusting the amplifier output power, adjusting the link attenuation coefficient, and adding an external radiator. Of these three methods, the first increases the field strength by increasing the output power, thus improving the sensing range. However, this requires a chip with controllable and self-calibrating output power, significantly increasing costs. The second method adds a tuning circuit or attenuation array to control the signal strength and adjust the sensing range by changing the link attenuation value. This requires additional circuitry and control logic, occupying more board space and increasing link losses. Both of these solutions involve modifications to the active components, increasing the power consumption of the entire NFC section and occupying more board space. The third method increases the field strength in all directions by adding an external radiator, thus increasing the sensing range. However, this method requires repeated simulation testing, which is time-consuming and labor-intensive, and the added external structure may alter the product's shape, affecting the overall design. Utility Model Content

[0003] The purpose of this application is to provide an NFC circuit and electronic device with adjustable sensing distance, which aims to solve the problems of high loss, high cost and large board area occupied by traditional NFC circuits when adjusting the sensing range of NFC coils.

[0004] In a first aspect, embodiments of this application provide an NFC circuit with adjustable sensing distance, comprising: NFC coils are used to couple electromagnetic signals; A grounding coil is disposed outside the NFC coil and is used to generate an induced current based on the NFC coil current excitation. A tuning circuit, disposed on the grounding coil, is used to adjust the magnitude of the induced current to cancel out part of the electromagnetic signal of the NFC coil.

[0005] In the technical solution of this application embodiment, the tuning circuit adjusts the magnitude of the induced current to cancel out part of the electromagnetic signal of the NFC coil, that is, to reduce the field strength of the electromagnetic signal of the NFC coil, so that the sensing range of the NFC coil is reduced to the required size. This does not require any adjustment to the front-end circuit of the NFC coil, does not consume additional energy, and can reduce losses, costs, and board space. Furthermore, this method can avoid the problem of multiple NFC devices (NFC coils) being falsely triggered by a single NFC card simultaneously induction of multiple NFC coils when the coil positions are very close to each other.

[0006] In some embodiments, the NFC coil and the grounding coil are arranged in the same plane, and the NFC coil current is in the opposite direction to the induced current.

[0007] In the technical solutions of this application embodiment, for example, the NFC coil and the grounding coil are arranged on the same circuit board 10, which occupies a small board area and is conducive to product cost reduction and miniaturization. In some embodiments, the tuning circuit includes an impedance-adjustable circuit connected in series with the grounding coil.

[0008] In the technical solution of this application embodiment, the impedance of the adjustable circuit is configured, that is, the grounding impedance of the grounding coil is adjusted, thereby adjusting the induced current, canceling part of the electromagnetic signal of the appropriate NFC coil, and reducing the sensing range.

[0009] In some embodiments, the impedance-adjustable circuit includes at least one resistor and at least one controllable switch, with one of the resistors and one controllable switch connected in series on the grounding coil.

[0010] In the technical solution of this application embodiment, multiple resistors and controllable switches constitute a switch array, and through the combination of switches, it can adapt to various sensing ranges of the NFC coil.

[0011] In some embodiments, the controllable switch includes an electronic switch connected in series with the resistor, the controlled terminal of the electronic switch being used to receive a drive signal, the drive signal being used to control the electronic switch to turn on and off.

[0012] In the technical solution of this application embodiment, the controllable switch is an electronic switch, which is convenient and reliable to adjust.

[0013] In some embodiments, the tuning circuit further includes a control chip connected to the controlled terminal of the electronic switch, which is used to output the drive signal to the controlled terminal of the electronic switch.

[0014] In the technical solutions of this application embodiment, adjustment via a control chip is convenient and reliable.

[0015] In some embodiments, the tuning circuit further includes a first mechanical switch connected to the control chip, the first mechanical switch being operable to output a switching signal to the control chip so that the control chip outputs the drive signal.

[0016] In the technical solution of this application embodiment, the grounding impedance can also be adjusted by controlling the control chip through the first mechanical switch, which is convenient and reliable.

[0017] In some embodiments, the controllable switch includes a second mechanical switch connected in series with the resistor, and the second mechanical switch is operable to control the connection and disconnection of the resistor with the grounding coil.

[0018] In the technical solution of this application embodiment, the grounding impedance can also be directly adjusted through the second mechanical switch, which is highly flexible.

[0019] In some embodiments, the impedance-adjustable circuit includes a potentiometer connected in series with the grounding coil. Secondly, embodiments of this application provide an electronic device including the NFC circuit described above.

[0020] The beneficial effects of this application embodiment compared with related technologies are as follows: The electronic device provided in this application embodiment includes an NFC circuit with adjustable sensing distance. The NFC circuit includes an NFC coil, a grounding coil, and a tuning circuit. The NFC coil is used to couple electromagnetic signals; the grounding coil is disposed outside the NFC coil and is used to generate an induced current based on the NFC coil current excitation; the tuning circuit is disposed on the grounding coil and is used to adjust the magnitude of the induced current, thereby canceling part of the electromagnetic signal of the NFC coil, that is, reducing the field strength of the electromagnetic signal of the NFC coil, so that the sensing range of the NFC coil is reduced to the required size. No adjustment is required to the front-end circuit of the NFC coil, and no additional energy is consumed. It can also reduce losses, costs, and board area. In addition, this method can avoid the problem of multiple NFC devices (NFC coils) being falsely triggered by a single NFC card simultaneously when the coil positions are very close to each other. Attached Figure Description

[0021] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic diagram of the NFC circuit provided in one embodiment of this application.

[0022] Figure 2 This is a schematic diagram of the NFC circuit provided in one embodiment of this application.

[0023] Figure 3 This is a circuit diagram of an NFC circuit provided in one embodiment of this application.

[0024] Figure 4 This is a circuit diagram of an NFC circuit provided in one embodiment of this application.

[0025] Figure 5 This is a circuit diagram of an NFC circuit provided in one embodiment of this application. Detailed Implementation

[0026] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0027] 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 pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0028] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0029] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0030] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0031] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0032] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0033] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0034] Please see Figure 1 This application provides an NFC circuit with adjustable sensing distance, comprising: The NFC coil 100 is used to couple electromagnetic signals to interact with other NFC devices or cards and achieve near-field communication.

[0035] A grounding coil 200 is arranged outside the NFC coil 100 and is used to generate an induced current based on the current excitation of the NFC coil 100.

[0036] The tuning circuit 300, located on the grounding coil 200, is used to adjust the magnitude of the induced current to cancel out part of the electromagnetic signal from the NFC coil 100.

[0037] The NFC coil 100 can be a copper-clad conductor arranged on the circuit board 10. The grounding coil 200 can be enclosed or semi-enclosed around the NFC coil 100. It can be grounded through the circuit board 10 with only one or more turns of copper-clad conductor. The circuit board 10 is, for example, a printed circuit board (PCB) or a flexible printed circuit board (FPC).

[0038] When there is current in the NFC coil 100, this NFC coil current will excite the grounding coil 200 to generate an induced current.

[0039] Because the current in NFC coil 100 and the induced current in ground coil 200 are in different directions, the electromagnetic fields they generate are also in different directions. The electromagnetic field generated by ground coil 200 will cancel out part of the electromagnetic signal of NFC coil 100, thereby reducing the magnetic field strength of NFC coil 100 and reducing its sensing range (i.e., distance).

[0040] In some scenarios, when the sensing range of the NFC coil 100 is too large, the impedance of the grounding coil 200 is adjusted by the tuning circuit 300 to change the magnitude of the induced current, thereby simultaneously reducing the field strength of the NFC coil 100 and shrinking its sensing range to the desired size. This method does not require any adjustments to the front-end circuitry of the NFC coil 100 and does not consume additional energy. Furthermore, this avoids the problem of multiple NFC devices simultaneously triggering multiple NFC coils 100 when multiple NFC devices are located very close to each other.

[0041] In some scenarios, when the NFC sensing range is moderate, the grounding coil 200 can be adjusted to 0 by the tuning circuit 300, that is, the grounding coil 200 is disconnected from the grounding loop of the circuit board 10. This way, no conducting loop of induced current is formed, and the sensing effect of the NFC coil 100 is basically unaffected.

[0042] In some embodiments, the NFC coil 100 and the ground coil 200 are arranged on the same plane, and the NFC coil current is opposite in direction to the induced current.

[0043] For example, the NFC coil 100 and the grounding coil 200 can be arranged on the same circuit board 10, which occupies a small area and is conducive to product cost reduction and miniaturization.

[0044] Please see Figure 2 In some embodiments, the tuning circuit 300 includes an impedance-adjustable circuit 310 connected in series with the grounding coil 200.

[0045] It is understandable that the sensing range of the NFC coil 100 is maximized when the grounding coil 200 is disconnected. Therefore, by configuring the impedance of the impedance-adjustable circuit 310, i.e., adjusting the grounding impedance of the grounding coil 200, the induced current is adjusted to offset a portion of the electromagnetic signal from the NFC coil 100, thereby reducing the sensing range.

[0046] Please see Figure 3 In some embodiments, the impedance-adjustable circuit 310 includes at least one resistor R and at least one controllable switch S1, with the resistor R and the controllable switch S1 connected in series on the grounding coil 200.

[0047] For example, there are multiple controllable switches S1 to form a switch array. Through the combination of switches, the impedance adjustable circuit 310 can adjust the grounding impedance of the grounding coil 200 to multiple levels, adapting to the various sensing ranges of the NFC coil 100.

[0048] For example, the controllable switch S1 can be any device that can be equivalent to a switch, such as an electronic switch or a mechanical switch. The resistance values ​​of different resistors R should be different.

[0049] In some embodiments, the controllable switch S1 includes an electronic switch connected in series with a resistor R. The controlled terminal of the electronic switch is used to receive a drive signal, which is used to control the electronic switch to turn on and off.

[0050] Electronic switches can be semiconductor transistors such as bipolar junction transistors (BJTs) or MOSFETs, or relays. When an electronic switch is a BJT, the base is the controlled terminal; when it's a MOSFET, the gate is the controlled terminal. When an electronic switch is a relay, one end of the relay coil is the controlled terminal, and the other end is grounded or connected to the power supply. The switching part of the relay is connected to a resistor R and a grounding coil 200. The switching part of the relay includes a moving contact and normally open / normally closed contacts.

[0051] Please see Figure 4 In some embodiments, the tuning circuit 300 further includes a control chip 320, which is connected to the controlled terminal of the electronic switch and is used to output a drive signal to the controlled terminal of the electronic switch.

[0052] The control chip 320 is connected to the controlled terminal of the electronic switch via an I / O port. Thus, the impedance of the impedance-adjustable circuit 310 can be adjusted via the control chip 320.

[0053] Please see Figure 4 In some embodiments, the tuning circuit 300 further includes a first mechanical switch 330, which is connected to the control chip 320. The first mechanical switch 330 can operably output a switching signal to the control chip 320 so that the control chip 320 outputs a drive signal.

[0054] The first mechanical switch 330 can be a rotary switch, a push-button switch, or a touch switch, etc. The user can operate the first mechanical switch 330 to adjust the gear position and input the corresponding switch signal to the control chip 320. The control chip 320 controls the corresponding controllable switch S1 to be turned on or off according to the corresponding switch signal, thereby realizing the impedance adjustment of the impedance adjustable circuit 310 and thus adjusting the induced current.

[0055] Please see Figure 3In some embodiments, the controllable switch S1 includes a second mechanical switch connected in series with a resistor R. The second mechanical switch is operable to control the connection and disconnection of the resistor R with the grounding coil 200.

[0056] The second mechanical switch can be a push switch or a touch switch, etc. The user can control the second mechanical switch to open or close, control whether the connected resistor R is connected to the grounding coil 200, adjust the grounding impedance of the grounding coil 200, and thus adjust the induced current.

[0057] Please see Figure 5 In some embodiments, the impedance-adjustable circuit 310 includes a potentiometer R0 connected in series with the grounding coil 200. For example, potentiometer R0 can be a mechanical potentiometer R0, allowing the user to directly adjust the grounding impedance of the grounding coil 200.

[0058] Potentiometer R0 can be an electronic potentiometer R0, which can be connected to the control chip 320. Similar to the embodiment of the electronic switch, the impedance of the electronic potentiometer R0 can be directly adjusted by the control chip 320 to adjust the grounding impedance of the grounding coil 200; or the impedance of the electronic potentiometer R0 can be adjusted by the first mechanical switch 330 through the control chip 320 to adjust the grounding impedance of the grounding coil 200.

[0059] Secondly, embodiments of this application provide an electronic device including the NFC circuit described above. The NFC coil 100 and grounding coil 200 in the NFC circuit can be arranged on the casing or circuit board of the electronic device.

[0060] The beneficial effects of this application embodiment compared with related technologies are as follows: The NFC circuit with adjustable sensing distance provided in this application embodiment includes: an NFC coil 100, a grounding coil 200, and a tuning circuit 300. The NFC coil 100 is used to couple electromagnetic signals; the grounding coil 200 is disposed outside the NFC coil 100 and is used to generate an induced current based on the excitation of the current-driven NFC coil 100 to cancel part of the radiation from the NFC coil 100; the tuning circuit 300 is disposed on the grounding coil 200 and is used to adjust the magnitude of the induced current, thereby canceling part of the radiation from the NFC coil 100 and simultaneously reducing the field strength of the electromagnetic signal of the NFC coil 100, so that the sensing range of a single NFC coil 100 is reduced to a reasonable size. The method does not require any adjustment to the front-end circuit of the NFC coil 100, does not consume additional energy, and can also reduce losses, costs, and board area. In addition, this method can avoid the problem of multiple NFC devices (NFC coils 100) being falsely triggered by a single NFC card when the coil positions are very close to each other.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. An NFC circuit with adjustable sensing distance, characterized in that, include: NFC coils are used to couple electromagnetic signals; A grounding coil is disposed outside the NFC coil and is used to generate an induced current based on the NFC coil current excitation. A tuning circuit, disposed on the grounding coil, is used to adjust the magnitude of the induced current to cancel out part of the electromagnetic signal of the NFC coil.

2. The NFC circuit as described in claim 1, characterized in that, The NFC coil and the grounding coil are arranged in the same plane, and the NFC coil current is in the opposite direction to the induced current.

3. The NFC circuit as described in claim 1 or 2, characterized in that, The tuning circuit includes an impedance-adjustable circuit, which is connected in series with the grounding coil.

4. The NFC circuit as described in claim 3, characterized in that, The impedance-adjustable circuit includes at least one resistor and at least one controllable switch, with one of the resistors and one controllable switch connected in series with the grounding coil.

5. The NFC circuit as described in claim 4, characterized in that, The controllable switch includes an electronic switch connected in series with the resistor. The controlled terminal of the electronic switch is used to receive a drive signal, which is used to control the electronic switch to turn on and off.

6. The NFC circuit as described in claim 5, characterized in that, The tuning circuit also includes a control chip, which is connected to the controlled terminal of the electronic switch and is used to output the drive signal to the controlled terminal of the electronic switch.

7. The NFC circuit as described in claim 6, characterized in that, The tuning circuit further includes a first mechanical switch, which is connected to the control chip. The first mechanical switch can operably output a switching signal to the control chip, so that the control chip outputs the drive signal.

8. The NFC circuit as described in claim 4, characterized in that, The controllable switch includes a second mechanical switch, which is connected in series with the resistor. The second mechanical switch can operate to control the connection and disconnection of the resistor and the grounding coil.

9. The NFC circuit as described in claim 3, characterized in that, The impedance-adjustable circuit includes a potentiometer, which is connected in series with the grounding coil.

10. An electronic device, characterized in that, Includes the NFC circuit as described in any one of claims 1 to 9.

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