Method for preventing chip burnout caused by overcurrent of NFC antenna
By setting up a current detection module in the NFC antenna loop and dynamically adjusting the RF power, the shortcomings of the static current limiting solution in the NFC card reader are solved, and a balance between high performance and high safety is achieved to prevent chip burning.
Patent Information
- Application Number
- CN202510482285.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-17
- Publication Date
- 2025-07-22
AI Technical Summary
The static current limiting scheme of existing NFC card readers cannot respond dynamically to load changes, resulting in overcurrent burning of the chip at high power output, while sacrificing card read performance and distance.
Set up a current detection module in the NFC antenna loop, convert the current signal through ADC, monitor the current value in real time and dynamically adjust the RF transmission power to ensure that the current is within the safe range, and use a closed-loop feedback mechanism to optimize the RF parameters.
While ensuring card reading performance and distance, it effectively prevents chip burning, improving the security and sensitivity of NFC card readers and reducing the probability of chip burning.
Smart Images
Figure CN120354873A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of NFC (Near Field Communication), and particularly to a method for preventing a chip from being burned due to overcurrent of an NFC antenna. Background Art
[0002] In the practical application of a near field communication (NFC) card reader, the resonance point of the NFC antenna may shift towards the low impedance direction due to load changes (such as different card types, metal object interference, or position offset), thereby causing an instantaneous surge in the antenna loop current. If the current exceeds the tolerance limit of the NFC chip, it will directly lead to chip burnout, resulting in equipment failure or even scrapping. The prior art usually adopts the method of a fixed current-limiting resistor to suppress the overcurrent risk, but this solution has a significant contradiction: although static current limiting can reduce part of the overcurrent risk, it needs to sacrifice the radio frequency transmission power, resulting in a shortened card reading distance and degraded performance; at the same time, due to the inability to dynamically respond to load changes, there is still a hidden danger of chip burnout in the critical current scenario.
[0003] Specifically, the setting of the fixed current-limiting resistor needs to take into account both maximum current protection and card reading performance, and the diversity and dynamics of the load in actual applications make it difficult for a single current-limiting value to adapt to all working conditions. For example, although high power output can increase the card reading distance, it may cause overcurrent due to sudden load changes; while low power output reduces the risk but limits the effective working range of the device. This static protection mechanism lacks real-time feedback and dynamic adjustment capabilities, resulting in the inability to achieve both performance and security. Summary of the Invention
[0004] The present invention provides a solution that can maintain a high radio frequency transmission power to optimize card reading performance while real-time detecting and dynamically suppressing the overcurrent risk.
[0005] The technical solution adopted by the present invention is as follows: A method for preventing a chip from being burned due to overcurrent of an NFC antenna, comprising the following steps:
[0006] Step 1: Set a current detection module in the current loop of the NFC antenna to real-time detect the current value flowing through the antenna;
[0007] Step 2: Collect the level signal output by the current detection module through the analog-to-digital conversion (ADC) pin of the main chip and convert it into the corresponding current value;
[0008] Step 3: Preset a current threshold V1, where V1 is the voltage value corresponding to the maximum safe current allowed by the NFC chip;
[0009] Step 4: During the card detection process and transaction process of the NFC card reader, the main chip continuously monitors the current value. If it detects that the current value exceeds V1, it immediately adjusts the RF transmission power parameter to dynamically reduce the transmission power from the initial maximum value P1 to the protection value P2;
[0010] Step 5: When the card reading process ends and the next card reading is started, the main chip restores the RF transmission power to the initial maximum value P1 again.
[0011] As a further improvement of the present invention, the current detection module includes a sampling resistor connected in series in the NFC antenna loop, and converts the current signal into a voltage signal through a voltage division circuit and outputs it to the ADC pin of the main chip.
[0012] As a further improvement of the present invention, the main chip communicates with the NFC chip through the SPI interface to adjust the RF transmission power parameter in real time.
[0013] As a further improvement of the present invention, the current threshold V1 is determined through experiments and is independent of the NFC antenna resonance point offset direction and load type.
[0014] As a further improvement of the present invention, the main chip periodically collects the current value at a fixed time interval T1 during the card detection process and collects the current value in real time during the transaction process.
[0015] As a further improvement of the present invention, the process of dynamically adjusting the RF transmission power includes: the main chip sends a control instruction to the NFC chip to reduce the duty cycle and amplitude of the RF output; verifies whether the adjusted current value is lower than V1 through a closed-loop feedback mechanism. If it still exceeds the threshold, further reduce the transmission power until the current value is within the safe range.
[0016] As a further improvement of the present invention, the protection value P2 is 50%-80% of P1, and the specific value is dynamically set according to the current tolerance characteristics of the NFC chip and the load change range.
[0017] An NFC card reader adopting the method for preventing the chip from being burned due to overcurrent of the NFC antenna as described above includes a main chip, an NFC chip, a current detection module and an NFC antenna.
[0018] The beneficial effects of the present invention: By dynamically detecting the NFC antenna current and adjusting the RF transmission power in real time, while ensuring the safety of the chip, maintaining a high RF field strength to optimize the card reading performance, solving the core contradiction of "incompatibility between performance and safety" in the traditional static current limiting scheme, and realizing the coordinated improvement of overcurrent protection and card reading distance and sensitivity. Description of the Drawings
[0019] Figure 1It is a schematic diagram of the hardware connection of a method for preventing chip burnout caused by overcurrent in the NFC antenna according to the present invention;
[0020] Figure 2 It is a specific flowchart of the logic control within the MCU main chip of a method for preventing chip burnout caused by overcurrent in the NFC antenna according to the present invention. Specific embodiments
[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be further described in detail below in conjunction with the drawings and embodiments. It should be understood that the embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0022] The present invention provides a method for preventing chip burnout caused by overcurrent in the NFC antenna, including the following steps:
[0023] Step 1: Set a current detection module in the current loop of the NFC antenna to detect the current value flowing through the antenna in real time;
[0024] Step 2: Collect the level signal output by the current detection module through the analog-to-digital conversion (ADC) pin of the main chip and convert it into a corresponding current value;
[0025] Step 3: Preset a current threshold V1, where V1 is the voltage value corresponding to the maximum safe current allowed by the NFC chip;
[0026] Step 4: During the card detection process and transaction process of the NFC card reader, the main chip continuously monitors the current value. If it is detected that the current value exceeds V1, the transmission power will be immediately dynamically reduced from the initial maximum value P1 to the protection value P2 by adjusting the radio frequency transmission power parameters;
[0027] Step 5: When the card reading process ends and the next card reading is started, the main chip restores the radio frequency transmission power to the initial maximum value P1 again.
[0028] In the present invention, the current detection module includes a sampling resistor connected in series in the NFC antenna loop, and the current signal is converted into a voltage signal through a voltage division circuit and output to the ADC pin of the main chip.
[0029] In the present invention, the main chip communicates with the NFC chip through the SPI interface to adjust the radio frequency transmission power parameters in real time.
[0030] In the present invention, the current threshold V1 is determined through experiments and is independent of the offset direction of the NFC antenna resonance point and the load type.
[0031] In the present invention, the main chip periodically collects the current value at a fixed time interval T1 during the card detection process and collects the current value in real time during the transaction process.
[0032] The process of dynamically adjusting the RF transmission power in the present invention includes: the main chip sends a control instruction to the NFC chip to reduce the duty cycle and amplitude of the RF output; through a closed-loop feedback mechanism, it is verified whether the adjusted current value is lower than V1. If it still exceeds the threshold, the transmission power is further reduced until the current value is within the safe range.
[0033] The protection value P2 in the present invention is 50%-80% of P1, and the specific value is dynamically set according to the current tolerance characteristics of the NFC chip and the load change range.
[0034] An NFC card reader adopts the method for preventing the chip from being burned out due to overcurrent of the NFC antenna as described above, and includes a main chip, an NFC chip, a current detection module and an NFC antenna.
[0035] Embodiment:
[0036] This embodiment provides a specific implementation manner of the method for preventing the chip from being burned out due to overcurrent of the NFC antenna. Combining the hardware architecture and the dynamic control process, it is specifically described as follows.
[0037] Hardware configuration
[0038] The hardware composition of the NFC card reader: includes a main chip (MCU), an NFC chip, an NFC antenna, and a current detection module.
[0039] Design of the current detection module: A sampling resistor with an accuracy of 1% (resistance value 0.1Ω) is connected in series in the current loop of the NFC antenna, and the voltage signal across the sampling resistor is converted into the range of 0-3.3V through a voltage division circuit and output to the ADC pin of the main chip.
[0040] Communication interface: The main chip is connected to the NFC chip through the SPI interface for sending RF power control instructions.
[0041] Parameter setting
[0042] Initial transmission power P1: Set to the maximum RF output power allowed by the NFC chip (for example, 30dBm) to ensure the farthest initial card reading distance.
[0043] Current threshold V1: Determined through experiments, the voltage value (for example, 1.65V) corresponding to the maximum safe current of the NFC chip (such as 500mA) is set as the threshold.
[0044] Protection power P2: Dynamically set to 50%-80% of P1 (for example, 15dBm to 24dBm), and the specific value is automatically adjusted according to the current load impedance change.
[0045] Sampling time interval T1: During the card detection process, the main chip collects the ADC level at a cycle of 10 ms; during the transaction process, it switches to real-time continuous sampling.
[0046] Dynamic control process
[0047] Step 1, Initial power startup:
[0048] When the card reader starts, the main chip sends an instruction to the NFC chip through the SPI interface to set the radio frequency transmission power to P1 (30 dBm) and start the card detection process with the maximum power.
[0049] Step 2, Current detection and judgment:
[0050] The chip periodically (every 10 ms during card detection) or in real-time (continuously during transactions) collects the voltage signal of the current detection module through the ADC pin and converts it into a current value. For example, if the ADC reads a voltage of 2.0 V (corresponding to a current of 600 mA), it is determined that the threshold V1 (1.65 V) is exceeded.
[0051] Step 3, Dynamic power adjustment:
[0052] When the current is detected to exceed the limit, the main chip immediately sends an instruction through the SPI interface to reduce the radio frequency output duty cycle of the NFC chip from 100% to 70%, and at the same time reduce the amplitude to the preset P2 (for example, 24 dBm).
[0053] Step 4, Closed-loop feedback verification:
[0054] After adjusting the power, the main chip continuously monitors the current value: if the current is still higher than V1, further reduce the duty cycle to 50% (corresponding to P2 = 15 dBm); if the current returns to the safe range, maintain the current power until the process ends.
[0055] Step 5, Power recovery mechanism:
[0056] After a single card reading or transaction is completed, the main chip resets the radio frequency power to P1 (30 dBm) to ensure that it works at the maximum power when starting next time.
[0057] Actual application scenario verification
[0058] Scenario 1, Metal object interference:
[0059] When a metal object approaches the NFC antenna and causes the resonance point to shift, the current detection module detects in real-time that the current rises to 550 mA (exceeding V1), and the main chip reduces the power to 20 dBm within 5 ms, causing the current to drop back to 400 mA to avoid chip burnout.
[0060] Scenario 2, Adaptation to multiple types of cards:
[0061] For high-impedance cards (such as bank cards with a metal layer), the system automatically maintains the P1 power to ensure the card reading distance; when a low-impedance card (such as a bus card) enters, the power is dynamically reduced to P2 to prevent overcurrent.
[0062] Effect verification
[0063] Through the above implementation, on the premise of ensuring the safety of the NFC chip, this solution improves the card reading distance from 3 cm in the traditional solution to 5 cm. At the same time, the overcurrent trigger response time is less than 10 ms, and the probability of chip burnout is reduced to less than 0.1%.
[0064] This embodiment realizes the balance between high performance and high security of the NFC card reader through hardware co-design, dynamic parameter adjustment and closed-loop feedback mechanism, and effectively solves the core contradiction of the traditional static current limiting scheme.
[0065] In summary, a method for preventing chip burnout caused by overcurrent of the NFC antenna of the present invention not only significantly improves the card reading performance of the card reader, but also greatly enhances the operating safety of the device through an innovative dynamic current detection and radio frequency power adjustment strategy. Compared with the traditional static current limiting method, the present invention can effectively prevent the chip burnout problem caused by overcurrent of the NFC antenna without sacrificing the card reading distance and sensitivity. This technological breakthrough is of great significance for promoting the application and development of NFC technology. Especially in fields such as payment, access control, and public transportation that require high reliability and high efficiency, it will bring a more convenient and secure near-field communication experience to users.
[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preventing a chip from being burned out due to overcurrent in an NFC antenna, characterized in that, Including the following steps: Step 1: Set a current detection module in the current loop of the NFC antenna to detect the current value flowing through the antenna in real time; Step 2: Collect the level signal output by the current detection module through the analog-to-digital conversion (ADC) pin of the main chip and convert it into the corresponding current value; Step 3: Preset a current threshold V1, where V1 is the voltage value corresponding to the maximum safe current allowed by the NFC chip; Step 4: During the card detection process and transaction process of the NFC card reader, the main chip continuously monitors the current value. If it is detected that the current value exceeds V1, immediately adjust the radio frequency transmission power parameter to dynamically reduce the transmission power from the initial maximum value P1 to the protection value P2; Step 5: When the card reading process ends and the next card reading is started, the main chip restores the radio frequency transmission power to the initial maximum value P1 again.
2. A method for preventing a chip from being burned out due to overcurrent of an NFC antenna according to claim 1, characterized in that, The current detection module includes a sampling resistor connected in series in the NFC antenna loop, and converts the current signal into a voltage signal through a voltage division circuit and outputs it to the ADC pin of the main chip.
3. A method for preventing a chip from being burned out due to overcurrent of an NFC antenna according to claim 1, characterized in that, The main chip communicates with the NFC chip through the SPI interface to adjust the radio frequency transmission power parameter in real time.
4. A method for preventing a chip from being burned due to overcurrent of an NFC antenna according to claim 1, characterized in that, The current threshold V1 is determined through experiments and is independent of the offset direction of the NFC antenna resonance point and the load type.
5. A method for preventing a chip from being burned out due to overcurrent of an NFC antenna according to claim 1, characterized in that, The main chip periodically collects the current value at a fixed time interval T1 during the card detection process and collects the current value in real time during the transaction process.
6. A method for preventing a chip from being burned due to overcurrent of an NFC antenna according to claim 1, characterized in that, The process of dynamically adjusting the radio frequency transmission power includes: the main chip sends a control instruction to the NFC chip to reduce the duty cycle and amplitude of the radio frequency output; verify whether the adjusted current value is lower than V1 through a closed-loop feedback mechanism. If it still exceeds the threshold, further reduce the transmission power until the current value is within the safe range.
7. A method for preventing a chip from being burned due to overcurrent of an NFC antenna according to claim 1, characterized in that, The protection value P2 is 50%-80% of P1, and the specific value is dynamically set according to the current-carrying characteristics of the NFC chip and the load change range.
8. An NFC card reader, characterized in that, Using the method for preventing the chip from being burned due to overcurrent of the NFC antenna according to any one of claims 1-7, including a main chip, an NFC chip, a current detection module, and an NFC antenna.