NFC power adaptive adjusting system and method for EMVCo authentication

Abstract

The invention discloses an NFC (Near Field Communication) power self-adaptive adjusting system and method for EMVCo (Empirical Mode Vector Co) authentication. The system comprises a power supply, a DC-DC boost converter, a power control module, a low dropout regulator and a radio frequency transmitter module. A mapping table of field intensity, voltage, current and impedance under different distances is established through a pretest stage; in the working stage, the power control module calculates the load impedance according to the current value measured by the low dropout linear regulator in real time and the current voltage, inquires the mapping table to obtain the target voltage, and cooperatively adjusts the output voltage of the DC-DC boost converter and the low dropout linear regulator. According to the invention, the closed-loop control of the NFC transmitting power is realized, so that the field intensity can be stabilized within the EMVCo standard range under different distances, the power supply fluctuation and load change are effectively adapted, and the system stability and the authentication debugging efficiency are improved.

Description

Technical Field

[0001] This invention relates to an NFC power adaptive adjustment system for EMVCo certification, and also to a corresponding NFC power adaptive adjustment method, belonging to the field of near-field communication technology. Background Technology

[0002] With the widespread adoption of Near Field Communication (NFC) technology in the financial payment sector, NFC-enabled POS machines have become core terminals for offline transactions. To ensure interoperability and transaction security between NFC payment devices and POS machines globally, the industry generally regards EMVCo L1 certification as a mandatory standard for the NFC radio frequency performance of POS machines. This certification imposes extremely stringent and precise requirements on the range of field strength that analog payment cards (PICC) can sense at different coupling distances.

[0003] To meet the aforementioned field strength requirements, existing technologies generally employ a debugging scheme based on a fixed impedance matching circuit. This type of scheme attempts to bring the field strength within the certification range at a specific distance by repeatedly adjusting the matching network (such as capacitors and inductors) around the antenna. However, the inherent "stronger near, weaker far" distribution characteristic of magnetic fields presents a natural contradiction with the EMVCo certification requirement of "stable field strength across multiple distances." Even more challenging is the fact that the equivalent impedance of the antenna dynamically changes with communication distance, card type, and environmental factors during actual operation. This makes the fixed-circuit-based debugging process exceptionally complex, time-consuming, and highly dependent on engineer experience, severely hindering large-scale production and rapid market launch.

[0004] While some attempts at improvement exist, such as the table-lookup method used in Chinese patent application CN119129616A to adjust communication parameters (e.g., modulation depth), these solutions are mostly limited to optimizing internal chip registers or subsequent stages of the signal chain, representing "local corrections." These solutions fail to fundamentally address the instability in RF energy output caused by power supply fluctuations and load impedance changes, lacking a proactive and rapid compensation power supply system. Specifically, existing solutions cannot effectively handle voltage drops during battery-powered devices during discharge, nor can they compensate for antenna impedance changes caused by distance variations in real time. This results in drastic fluctuations in field strength throughout the certification space, making it difficult to guarantee certification pass rates and product consistency.

[0005] Therefore, there is an urgent need in this field for a new technical solution that can start from the power supply head to achieve global, closed-loop, and adaptive adjustment of NFC transmission power, so as to fundamentally solve the core pain points faced in EMVCo certification debugging, such as uneven field strength at multiple distances, poor power supply adaptability, and low debugging efficiency. Summary of the Invention

[0006] The primary technical problem to be solved by this invention is to provide an NFC power adaptive adjustment system for EMVCo certification.

[0007] Another technical problem to be solved by the present invention is to provide an NFC power adaptive adjustment method for EMVCo certification.

[0008] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: According to a first aspect of the present invention, an NFC power adaptive adjustment system for EMVCo certification is provided, comprising a power supply, a DC-DC boost converter, a power control module, a low dropout linear regulator, and an RF transmitter module; The input terminal of the DC-DC boost converter is connected to the power supply to provide an adjustable first voltage; The input terminal of the low dropout linear regulator is connected to the output terminal of the DC-DC boost converter, and the output terminal of the low dropout linear regulator is connected to the power input terminal of the RF transmitter module to provide an adjustable second voltage and power the RF transmitter module. The low dropout linear regulator integrates a current measurement circuit to measure the load current at the output terminal in real time. The power control module is communicatively connected to the DC-DC boost converter, the low dropout linear regulator, and the radio frequency transmitter module, respectively. The power control module internally stores a mapping table established during the pre-test phase. The mapping table contains the corresponding relationships between the second voltage, load current, and calculated load impedance required to achieve the target field strength at different communication distances. The power control module is configured to, during operation: receive the load current measured by the low-dropout linear regulator, calculate the real-time load impedance in conjunction with the current second voltage; query the mapping table to determine the target second voltage corresponding to the real-time load impedance; and generate control commands based on the target second voltage to coordinately adjust the first voltage output by the DC-DC boost converter and the second voltage output by the low-dropout linear regulator, so that the field strength generated by the RF transmitter module is stabilized within the EMVCo specification range.

[0009] Preferably, the power control module uses a first I-channel... 2 The C-bus connects to and controls the DC-DC boost converter, via a second independent I-channel. 2 The C-bus connects to and controls the output voltage of the low-dropout linear regulator, and the SPI bus connects to the low-dropout linear regulator to read the load current measurement data.

[0010] Preferably, the power control module is further configured to: calculate the target second voltage using linear interpolation when the real-time load impedance is between two pre-stored impedance values ​​in the mapping table.

[0011] Preferably, when the power control module adjusts the first voltage output by the DC-DC boost converter, it ensures that the first voltage is always higher than the second voltage output by the low-dropout linear regulator, and maintains a preset fixed voltage difference.

[0012] Preferably, a self-resetting fuse is connected in series between the output terminal of the low-dropout linear regulator and the power input terminal of the radio frequency transmitter module.

[0013] According to a second aspect of the present invention, an NFC power adaptive adjustment method for EMVCo certification is provided, comprising the following steps: During the pre-test phase, the second voltage output by the low dropout linear regulator is first adjusted at different communication distances so that the field strength coupled to the test card reaches the predetermined target value within the EMVCo specification range. The second voltage and the load current measured by the internal current measurement circuit of the low dropout linear regulator are recorded simultaneously. The load impedance is calculated, and a mapping table containing distance, second voltage, load current and load impedance is formed and stored. During operation, the load current is monitored in real time through the internal current measurement circuit of the low-dropout linear regulator. Calculate the real-time load impedance based on the second voltage output of the low-dropout linear regulator and the real-time monitored load current. Query the mapping table to determine the target second voltage corresponding to the real-time load impedance; Based on the target second voltage, the first voltage output by the DC-DC boost converter and the second voltage output by the low dropout linear regulator are dynamically and collaboratively adjusted.

[0014] Preferably, the step of adjusting the first voltage output by the DC-DC boost converter specifically includes: The target second voltage is added to a preset fixed voltage difference value, and the resulting voltage value is used as the target value of the first voltage for adjustment.

[0015] Preferably, in the pre-testing phase, the predetermined target field strength is set to the same constant value at all test distances, and the constant value is located in the middle region of the EMVCo specification field strength range.

[0016] Preferably, during the working phase, if the calculated real-time load impedance is between two pre-stored impedance values ​​in the mapping table, the target second voltage is calculated using linear interpolation.

[0017] Preferably, the method further includes a field strength verification step: after voltage adjustment, the field strength is verified by the field strength detection auxiliary circuit inside the radio frequency transmitter module. If the field strength deviation exceeds the tolerance, the pre-test stage process is triggered for recalibration.

[0018] Compared with existing technologies, this invention achieves precise control of NFC transmission power by constructing a dynamic closed-loop power system consisting of a power control module, a DC-DC boost converter, and a low-dropout linear regulator, combined with a pre-test mapping table adjustment mechanism based on real-time impedance calculation. Using this invention, the NFC field strength can stably meet EMVCo specifications within a distance range of 0cm to 4cm, effectively improving field strength uniformity. It also possesses adaptability to power supply voltage fluctuations and load impedance changes, enhancing the stability of NFC devices under different operating conditions. Furthermore, by transforming the traditional manual trial-and-error debugging process into an automated data-driven workflow, it improves the efficiency of certification debugging and the consistency of product performance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of an NFC power adaptive adjustment system for EMVCo certification in the first embodiment of the present invention; Figure 2 The circuit diagram of the DC-DC boost converter, low-dropout linear regulator, and power control module in the first embodiment of the present invention is shown below. Figure 3 This is a flowchart illustrating the working principle of an NFC power adaptive adjustment system for EMVCo certification, as shown in the first embodiment of the present invention. Detailed Implementation

[0020] The technical content of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] The technical concept of this invention lies in providing a dynamic closed-loop control logic that "coordinates the adjustment of two-stage voltages based on a real-time load impedance lookup mapping table." Specifically, by establishing a precise mapping relationship between communication distance, target field strength, output voltage, load current, and calculated impedance during the pre-testing phase, the complex field strength testing problem is transformed into monitoring and responding to the key electrical parameter of load impedance. During the operating phase, by measuring the load current and voltage in real time, the current load impedance is dynamically calculated and used as an index to look up the pre-stored mapping table, quickly determining the optimal operating voltage required to maintain the target field strength under the current communication environment. Subsequently, the power control module generates coordinated control commands based on this target voltage, synchronously adjusting the output voltages of the front-end DC-DC boost converter and the rear-end low-dropout linear regulator, thus forming a complete closed loop from impedance sensing to power execution. This original design enables this NFC power adaptive adjustment system to proactively and quickly compensate for antenna impedance changes and energy supply fluctuations caused by changes in communication distance, card type differences, and power supply fluctuations, ensuring the stability and consistency of the NFC field strength across the entire distance range required for EMVCo certification from the source.

[0022] First Embodiment like Figure 1 As shown, the first embodiment of the present invention provides an NFC power adaptive adjustment system for EMVCo certification, including a power supply, a DC-DC boost converter, a power control module, a low dropout linear regulator, and an RF transmitter module.

[0023] The power supply provides initial power to the entire NFC power adaptive regulation system. This battery can be a lithium battery, a nickel-metal hydride battery, or a DC adapter connected to AC power; no specific limitation is made in this invention. The first input terminal of the DC-DC boost converter is connected to the power supply, and its function is to boost the voltage output by the power supply to meet the system's high-voltage requirements. The first input terminal of the low-dropout linear regulator is connected to the output terminal of the DC-DC boost converter. On the one hand, it can reduce the high voltage output by the DC-DC boost converter to a suitable level. On the other hand, it can measure its own output current in real time and transmit the measured current information to the power control module. The voltage output by the low-dropout linear regulator is finally sent to the RF transmitter module through the second output terminal as the power supply to drive the RF transmitter module. The power control module is connected to the second input terminal of the DC-DC boost converter, the second input terminal of the low-dropout linear regulator, and the first output terminal of the low-dropout linear regulator. It is used to receive the current measurement data transmitted from the low-dropout linear regulator and adjust the output voltage of the DC-DC boost converter and the low-dropout linear regulator based on this data, thereby forming a closed-loop control system to realize real-time dynamic adjustment of NFC transmission power.

[0024] In one embodiment of the invention, the positive terminal of the power supply is connected to the input terminal of the DC-DC boost converter via a low-impedance wire. This connection must ensure no significant voltage drop to avoid input voltage fluctuations due to excessive wire resistance. The negative terminal of the power supply is directly connected to the system ground, forming a complete current loop. To suppress grounding noise, a 10μF ceramic capacitor is typically connected in parallel between the negative terminal and ground to absorb high-frequency interference signals.

[0025] In addition, a self-resetting fuse is connected in series between the power supply and the DC-DC boost converter. When an overcurrent occurs in the circuit, the fuse automatically trips, protecting the power supply and subsequent modules from damage. After the fault is cleared, the fuse automatically resets its conduction, requiring no manual replacement. The power supply has no other control signal connections; it transmits power solely through wires. Its output state is entirely determined by the operating state of the DC-DC boost converter. When the DC-DC boost converter starts, the power supply begins supplying power; when the DC-DC boost converter stops, the power supply stops outputting current and enters standby mode. This connection method ensures efficient use of power and avoids unnecessary power consumption.

[0026] like Figure 2 As shown, in one embodiment of the present invention, the DC-DC boost converter specifically adopts a Boost converter topology. Based on the first digital reference control signal REF1_CTRL<7:0> output by the power control module, it dynamically adjusts the internal reference voltage REF, thereby precisely setting its output voltage VUP. Considering the relatively stable load current of the NFC system during operation, this embodiment preferably employs pulse width modulation (PWM) control. This control method offers higher stability and simpler control logic in a stable state, which is beneficial for improving system reliability.

[0027] It's important to note that the DC-DC boost converter is the "first hurdle" in voltage regulation, and its connections involve three dimensions: power input, voltage output, and control signal interaction. At the power input level, the DC-DC boost converter's input terminal is directly connected to the positive output terminal of the power supply, receiving a raw voltage of 3.0V to 4.2V; its ground terminal is connected to the system common ground, forming a loop with the negative terminal of the power supply. To stabilize the input voltage, a 100μF electrolytic capacitor and a 1μF ceramic capacitor are typically connected in parallel between the VIN pin and GND of the DC-DC boost converter. The former filters out low-frequency ripple, and the latter absorbs high-frequency noise, ensuring the stability of the input voltage.

[0028] The output of the DC-DC boost converter is connected to the input of the low-dropout linear regulator via a shielded wire, with the shield grounded to reduce electromagnetic interference. The core function of this connection is to transmit the boosted voltage to the low-dropout linear regulator, providing the basis for subsequent buck regulation. A capacitor array is also connected in parallel between the output and ground to further filter out ripple generated during the boost process, ensuring the purity of the output voltage.

[0029] The control interface of the DC-DC boost converter is I 2 It consists of a C bus and an enable pin. Among them, I... 2 The C bus is directly connected to the corresponding I bus of the power control module. 2 The Type-C interface is used to receive voltage adjustment commands from the power control module. For example, when the power control module needs to adjust the output voltage to 5.7V, it will do so via the I / O interface. 2 The C bus sends a data packet containing the target voltage value. The DC-DC boost converter receives and parses the instruction, then adjusts the output voltage through its internal PWM controller. The SCL pin is the clock line, responsible for synchronous data transmission; the SDA pin is the data line, enabling bidirectional data communication. The enable pin is connected to a GPIO pin of the power control module. When the power control module outputs a high level, the DC-DC boost converter starts working; when it outputs a low level, the DC-DC boost converter enters sleep mode, stopping the output voltage to reduce standby power consumption.

[0030] In addition, the over-temperature detection pin of the DC-DC boost converter is connected to the GPIO pin of the power control module through a 10kΩ pull-up resistor. When the internal temperature of the module exceeds the set threshold, the OT pin will output a low level. After the power control module detects the signal, it will immediately send a command to reduce the output voltage until the temperature returns to normal, thus forming an overheat protection mechanism.

[0031] In one embodiment of the present invention, the low-dropout linear regulator (labeled TX_LDO in the figure) performs a dual function in this system: firstly, it provides a highly stable voltage source for the subsequent RF transmitter module; secondly, it detects the load current of the RF transmitting circuit in real time. The low-dropout linear regulator also receives the second digital reference control signal REF2_CTRL<7:0> from the power control module and precisely sets its output voltage VOUT_TXLDO by adjusting its internal reference voltage. By ensuring that the value of REF2_CTRL<7:0> is always smaller than REF1_CTRL<7:0> by a fixed difference (Delta), it can be ensured that the output voltage VUP of the DC-DC boost converter is always higher than the output voltage VOUT_TXLDO of the low-dropout linear regulator by a preset fixed difference. This design enables the entire NFC power adaptive adjustment system to achieve stable output while optimizing energy conversion efficiency. In terms of current detection, the low-dropout linear regulator generates a detection voltage signal TXI_DET that is strictly linearly related to the load current through its internal integrated mirror circuit, providing a key technical means for realizing real-time, non-destructive current measurement.

[0032] As a composite unit for voltage regulation and current measurement, the low-dropout linear regulator (LDLV) needs to meet the dual requirements of power transmission and data acquisition in its connection configuration. For power input, the LLV's input terminal is directly connected to the output terminal of the DC-DC boost converter to receive the boosted voltage signal. To accommodate dynamic changes in the DC-DC boost converter's output voltage, a tantalum capacitor is connected in parallel between the LLV's input pin and ground. The low ESR (equivalent series resistance) characteristic of the tantalum capacitor stabilizes the input voltage and prevents voltage spikes caused by sudden load changes.

[0033] In one embodiment of the present invention, the output terminal of the low-dropout linear regulator is connected to the power input terminal of the RF transmitter module via a twisted pair cable. The output voltage range is 1.8V to 5.0V, which directly serves as the operating power supply for the RF transmitter module. A 10μF ceramic capacitor and a 100nF ceramic capacitor are connected in parallel between the output terminal and ground. The former is used to filter out low-frequency ripple, and the latter is used to suppress high-frequency noise, ensuring that the RF transmitter module operates in a stable voltage environment.

[0034] The low-dropout linear regulator transmits the amplified voltage signal to the power control module via the SPI bus. The internal AD converter of the power control module converts the amplified voltage signal into a digital current value. The SPI bus connections are as follows: the SCK (clock) pin of the low-dropout linear regulator is connected to the SPI clock output pin of the power control module; the MISO (master input, slave output) pin is connected to the SPI data input pin of the power control module; the MOSI (master output, slave input) pin is connected to the SPI data output pin of the power control module; and the CS (chip select) pin is connected to the GPIO pin of the power control module. When the power control module needs to read current data, it pulls the CS pin low and then sends a clock signal through the SCK pin. Driven by the clock, the low-dropout linear regulator transmits the current data to the power control module through the MISO pin. Each data transmission takes no more than 10μs, ensuring real-time performance.

[0035] It should be noted that the quantization objects of the aforementioned AD converter include, but are not limited to, the output voltage VOUT_TXLDO of the low-dropout linear regulator and the TXI_DET voltage characterizing the load current. After converting the acquired analog voltage and current information into digital signals, the AD converter transmits them to the power control module. Based on this real-time data, the power control module calculates the optimal reference voltage control words REF1_CTRL<7:0> and REF2_CTRL<7:0> using an internal adaptive algorithm, thereby completing the coordinated regulation of the two power supplies. Once the regulation is complete, the system reaches a stable state, obtaining the desired operating voltage VOUT_TXLDO, and thus outputting RF power conforming to the EMVCo field strength specification.

[0036] The voltage regulation interface of the low dropout linear regulator also adopts I... 2 C bus, and the power control module's I / O 2 Connected to the C interface (multiplexing the I of the DC-DC boost converter) 2 The C-bus (distinguished by different device addresses) allows the power control module to precisely regulate the output voltage by sending commands to the internal reference voltage source of the low-dropout linear regulator. The enable pin of the low-dropout linear regulator is connected to the GPIO pin of the power control module, and the control logic is consistent with that of the DC-DC boost converter: high-level start-up and low-level sleep.

[0037] It should be noted that a self-resetting fuse is connected in series between the output of the low-dropout linear regulator and the RF transmitter module. This fuse has a resistance of less than 50mΩ at room temperature. When the load current exceeds a set threshold, its resistance increases rapidly to the kiloohm level within milliseconds, effectively cutting off the power supply circuit. After the fault is cleared and the temperature returns to normal, the fuse resistance automatically returns to its normal value. This protection design not only prevents equipment damage under overcurrent conditions but also enables automatic recovery from system faults, significantly improving system reliability and lifespan, especially demonstrating a clear advantage in frequent debugging and certification testing scenarios. Simultaneously, a current detection point is also set on this series path, allowing real-time monitoring of the output current waveform via an oscilloscope for troubleshooting during the debugging phase.

[0038] In one embodiment of the present invention, the power control module uses two independent I / O pins. 2 The C-bus establishes control connections with both the DC-DC boost converter and the low-dropout linear regulator, and communicates with the low-dropout linear regulator via an SPI bus. Specifically, the power control module communicates with the low-dropout linear regulator via the first I-bus. 2 The C bus (SCL1, SDA1 pins) connects to the control interface of the DC-DC boost converter, using standard I... 2 The C-type communication protocol sends a digital command packet containing the target voltage value via a specified device address. This data frame format includes a start bit, device address, register address, 8 bits of voltage data, and a checksum sequence to ensure the integrity and reliability of the command transmission. Upon receiving the command, the DC-DC boost converter immediately adjusts its output voltage and can return the current actual output voltage value via a read operation for verification by the power control module. Simultaneously, the power control module communicates via a second physically isolated I-type... 2 The C bus (SCL2, SDA2 pins) connects to the control interface of the low dropout linear regulator. It uses the same communication protocol as the DC-DC boost converter but is assigned a different device address, which effectively avoids bus conflicts and enables precise setting of the output voltage of the low dropout linear regulator.

[0039] To acquire load status information in real time, the power control module reads the current measurement data integrated into the low-dropout linear regulator via the SPI bus (SCK, MISO, MOSI, CS pins) at a sampling rate of 1MHz. The SPI communication protocol is configured in mode 0, including clock synchronization, 16-bit data frames, and a CRC check mechanism, ensuring that a single current sample is completed within 10μs, providing a high-precision data foundation for real-time impedance calculation. The power control module immediately verifies the received current data; if the data is valid, it is used for impedance calculation; if invalid, the data is discarded and the module waits for the next frame transmission, preventing erroneous data from causing abnormal regulation. This multi-bus independent collaborative communication architecture achieves both precise control of each power module and ensures real-time acquisition of load status information.

[0040] The power control module employs linear interpolation to achieve continuous impedance-voltage mapping. When the real-time calculated load impedance falls between two pre-stored impedance values ​​in the mapping table, interpolation calculations are automatically initiated. Based on the proportional relationship between the impedance difference and the voltage difference, the microprocessor performs mathematical calculations to derive the precise target second voltage. For example, when an impedance of 17.0Ω is detected, based on the pre-stored data of 16.4Ω corresponding to 2.6V and 17.4Ω corresponding to 3.1V, the target second voltage is calculated using the formula (17.0-16.4) / (17.4-16.4)×(3.1-2.6)+2.6=2.9V. This linear interpolation method is implemented in real-time in hardware with a processing delay of less than 5μs, effectively avoiding field strength step fluctuations caused by the discreteness of the mapping table, and significantly improving the continuity and control accuracy of power regulation.

[0041] It should be noted that the power control module ensures system efficiency through a fixed differential voltage maintenance mechanism. Specifically, when adjusting the first voltage output of the DC-DC boost converter, the control logic always sets the first voltage to the sum of the target second voltage and the preset fixed differential voltage. This differential voltage is typically set to 0.2V and is dynamically adjusted according to the minimum differential voltage requirement of the low-dropout linear regulator. In practice, the differential voltage compensation unit within the power control module calculates the target first voltage value in real time and transmits it via I... 2 The C-bus synchronously sends signals to the DC-DC boost converter, ensuring that the input voltage of the low-dropout linear regulator is always higher than the output voltage and maintaining the optimal operating dropout voltage. This coordinated regulation strategy not only guarantees the stable operation of the power supply system but also optimizes the overall power conversion efficiency.

[0042] In one embodiment of the invention, the field strength verification process is automatically initiated after each voltage adjustment. The power control module acquires an analog voltage signal proportional to the field strength through the field strength detection auxiliary circuit integrated within the RF transmitter module, and performs digitization processing at a rate of 100kSPS using a 12-bit ADC. When the deviation between the detected field strength value and the target value exceeds the tolerance range, a pre-test process is automatically triggered for recalibration, updating the voltage-impedance correspondence in the mapping table. This closed-loop verification mechanism effectively compensates for performance changes caused by environmental factors such as device aging and temperature drift, ensuring the long-term stability of the system and fundamentally solving the technical problem of easy field strength drift in traditional open-loop solutions.

[0043] Furthermore, in terms of pre-test parameter settings, an optimization strategy using a unified field strength benchmark is adopted. For all test distances, the target field strength is set to the median value within the EMVCo specification's field strength range. This setting method avoids the critical risks associated with boundary value adjustments and simplifies the mapping table data structure. By establishing a voltage-impedance mapping relationship with a constant field strength as the target, the system can achieve field strength stability with minimal adjustment costs at different communication distances, significantly improving the EMVCo certification pass rate and debugging efficiency.

[0044] In the connection with the RF transmitter module, the GPIO1 pin of the power control module is connected to the enable pin of the RF transmitter module. When GPIO1 outputs a high level, the RF transmitter module starts working and begins transmitting a 13.56MHz RF signal; when it outputs a low level, the RF transmitter module shuts down and stops transmitting signals. The GPIO2 pin of the power control module is connected to the mode control pin (MODE) of the RF transmitter module, used to switch the operating mode of the RF transmitter module. A high level indicates active mode (the RF transmitter module actively transmits carrier signals), and a low level indicates passive mode (it only responds when receiving external signals). This switching function can adapt to different NFC communication scenarios. In addition, the status feedback pin (READY) of the RF transmitter module is connected to the GPIO3 pin of the power control module through a pull-up resistor. When the RF transmitter module completes initialization and is ready, the status feedback pin outputs a high level. The power control module detects this signal and then starts the subsequent power adjustment process to ensure that the RF transmitter module is working properly.

[0045] The power control module also integrates a storage unit, whose data interface is connected to the main controller via an internal bus. This storage unit stores the "distance-voltage-current-impedance" parameter table during the pre-test phase. During data writing, the main controller sends the address and data to the storage unit via the SPI interface to complete the table storage. During dynamic adjustment, the main controller quickly reads the corresponding data via address lookup, with a lookup time of no more than 10μs, ensuring rapid adjustment response.

[0046] To enable debugging and configuration with external devices, the power control module also features a UART interface (TX and RX pins), which connects to the host computer's USB interface via a level conversion chip. Engineers can send commands through the host computer, and the power control module receives and executes the corresponding operations, returning the results. This interface plays a crucial role in the equipment development and production debugging phases, and can be used for parameter calibration, fault diagnosis, and other tasks.

[0047] In one embodiment of the present invention, the RF transmitter module serves as the NFC signal transmitter, and its connection directly affects signal quality and power control accuracy. Regarding power connection, the power input terminal of the RF transmitter module is directly connected to the output terminal of the low-dropout linear regulator, receiving an operating voltage of 1.8V to 5.0V. A 2.2μF ceramic capacitor is connected in parallel between the power pin and ground to filter high-frequency noise on the power line, ensuring stable operation of the internal oscillation circuit of the RF transmitter module. The ground terminal of the RF transmitter module is connected to the system common ground, and shares a common ground with the ground terminals of the low-dropout linear regulator and the DC-DC boost converter through a large-area copper plating, reducing potential differences caused by grounding impedance and avoiding noise coupling.

[0048] For radio frequency (RF) signal transmission, the antenna interface of the RF transmitter module is connected to the NFC antenna via a matching circuit. The matching circuit consists of two adjustable capacitors and one adjustable inductor. Its function is to match the output impedance of the RF transmitter module with the actual impedance of the antenna, minimizing signal reflection and improving power transmission efficiency. The antenna uses a PCB planar coil structure, with its two leads connected to the output of the matching circuit. When the RF transmitter module outputs alternating current, the antenna generates an alternating magnetic field. The magnetic field strength is proportional to the current magnitude, thus determining the field strength coupled to the PICC.

[0049] Regarding control signal connections, the enable pin of the RF transmitter module is connected to the GPIO1 pin of the power control module. As mentioned earlier, the RF transmitter module's startup and shutdown are controlled by high and low levels. The modulation signal input pin of the RF transmitter module is connected to the PWM output pin of the power control module. The power control module outputs PWM signals with different duty cycles to perform ASK modulation on the 13.56MHz carrier wave output by the RF transmitter module, thereby achieving data transmission. The modulation depth can be adjusted via the PWM duty cycle to meet the modulation signal requirements of the NFC communication standard.

[0050] The RF transmitter module also integrates a field strength detection auxiliary circuit, whose output is connected to the ADC input pin of the power control module. This circuit is used to assist in calibrating the field strength during the pre-test phase. When the PICC is at different distances, the voltage signal output by the FS pin is proportional to the field strength. The power control module acquires this signal through the ADC and can quickly determine whether the field strength has reached the target value, thus assisting in recording the pre-test parameters.

[0051] The working principle of this invention will be explained in detail below: like Figure 3 As shown, firstly, a pre-test is conducted. Based on the median value of EMVCoL1 certification (to avoid approaching the upper or lower limit), the target field strength from 0cm to 4cm is set to 5V (this value is within the specification range for all distances: 4.3 to 7.35V for 0cm and 3.84 to 7.35V for 4cm).

[0052] Next, tests were conducted at various distances: 0cm distance test: Fix the PICC at a distance of 0cm from the antenna (closely fit); The power control module initializes the DC-DC boost converter output to 3.0V and the low dropout linear regulator output to 2.0V. At this time, the RF transmitter module starts working, and the PICC measures a field strength of 3.2V (lower than the 5V target). The power control module gradually increases the output voltage of the low dropout linear regulator (by 0.1V each time) through instructions from the host computer, while recording the output current of the low dropout linear regulator and the field strength value of the PICC. When the PICC field strength reaches 5V, stop adjusting and record the parameters at this time: Low dropout linear regulator output voltage 2.2V, current 145mA, calculate impedance: Z = 2.2V / 0.145A ≈ 15.2Ω The parameters "distance 0cm, target field strength 5V, voltage 2.2V, current 145mA, impedance 15.2Ω" are stored in the storage unit of the power control module.

[0053] 1cm distance test: When the PICC is moved to a distance of 1cm, the electric field strength at the original voltage of 2.2V drops to 3.8V (below the target) due to the increased distance. Gradually increase the output voltage of the low-dropout linear regulator to 2.6V. At this point, the current rises to 159mA, and the PICC field strength reaches 5V. Calculate the impedance: Z = 2.6V / 0.159A ≈ 16.4Ω Storage parameters: "Distance 1cm, Voltage 2.6V, Current 159mA, Impedance 16.4Ω".

[0054] 2cm, 3cm, 4cm distance tests: Repeat the above steps and record the results: 2cm: Voltage 3.1V, Current 178mA, Impedance 17.4Ω; 3cm: Voltage 4.4V, Current 234mA, Impedance 18.8Ω; 4cm: Voltage 5.7V, Current 288mA, Impedance 19.8Ω.

[0055] Data verification: After completing all distance tests, reposition the PICC in each position, retrieve the stored voltage parameters, and verify whether the field strength is stable within the range of 5V±0.1V. If the deviation exceeds 0.1V, retesting and calibration are required.

[0056] The pre-test data is stored in tabular form in the power control module's storage unit, in the following format (array form): Table 1 Pre-test Data Table The table above supports interpolation calculations. When the actual impedance falls between two recorded values ​​(e.g., 17.0Ω is between 16.4Ω and 17.4Ω), the power control module will calculate the corresponding target voltage using linear interpolation. For example: It should be noted that the "distance-voltage-current-impedance" mapping table established during the pre-testing phase is the core of achieving adaptive adjustment. To further improve the precision of power control, the sampling range of the pre-test can be increased. For example, within the current range of 0cm to 4cm, the distance step size can be increased from 1cm to 0.5cm or 0.25cm. In addition, horizontal position offsets can be introduced at a fixed height for multi-point testing to construct a more comprehensive spatial impedance mapping model.

[0057] To ensure the stable and reliable operation of the NFC power adaptive regulation system provided by this invention, a crucial design principle is that the load impedance of the RF transmitter module must exhibit strict monotonicity as the output voltage of the low-dropout linear regulator changes throughout the entire effective operating range of the system. This means that for a given load impedance value, there is one and only one corresponding target output voltage value in the mapping table. This monotonicity constraint is key to ensuring the determinism and uniqueness of the control logic. If the impedance and voltage are not monotonic or have multiple corresponding values, ambiguity will arise when querying the target voltage based on the load impedance, leading to regulation oscillation or field strength runaway. Therefore, in the pre-testing phase, it is necessary not only to record data but also to verify and ensure the validity of this monotonicity.

[0058] Next, certification testing will be conducted. In the EMVCoL1 certification test, the test equipment will gradually move a simulated payment card (PICC) from 4cm to 0cm. The system needs to adjust the transmission power in real time to ensure that the field strength of the PICC meets the specifications at all locations. The following details the dynamic adjustment process using a specific scenario: Initial state (PICC located at 4cm): At the start of the test, the PICC was fixed at 4cm. The power control module called the parameters corresponding to 4cm in the pre-test table: voltage 5.7V, current 288mA, impedance 19.8Ω. The power control module sends a command to the DC-DC boost converter: "Adjust the output voltage to 5.7V + the voltage drop of the low dropout linear regulator (0.2V) = 5.9V" (the voltage drop of the low dropout linear regulator is the difference between the input and output, ensuring that the input voltage is more than 0.2V higher than the output voltage). The DC-DC boost converter responds to the command and adjusts the output voltage to 5.9V. After receiving the command, the low dropout linear regulator module stabilizes the output voltage at 5.7V. At this time, the power supply voltage of the RF transmitter module is 5.7V. The low-dropout linear regulator module measures the current current as 288mA and transmits it to the power control module in real time. The calculated impedance Z = 5.7V / 0.288A ≈ 19.8Ω, which is consistent with the preset value. The field strength is stable at 5V (which meets the specification of 3.84~7.35V at 4cm).

[0059] The adjustment process of moving the PICC to 2cm: When the test equipment moves the PICC from 4cm to 2cm, the magnetic field coupling is enhanced due to the shortened distance. If the voltage remains unchanged at 5.7V, the field strength of the PICC will rise to 6.8V (exceeding the 5V target). At the same time, the load impedance of the RF transmitter module will drop from 19.8Ω to 17.4Ω (the shortened distance leads to a decrease in the equivalent impedance of the antenna). The impedance change caused the output current of the low-dropout linear regulator to rise from 288mA to 327mA. The low-dropout linear regulator module transmits 327mA of current data to the power control module in real time, and calculates the current impedance Z = 5.7V / 0.327A ≈ 17.4Ω; The power control module consulted the pre-test table and found that 17.4Ω corresponds to a target voltage of 3.1V at 2cm. Immediately send the command to the DC-DC boost converter: "Adjust the output voltage to 3.1V + 0.2V = 3.3V", and at the same time send the command to the low dropout linear regulator module: "Adjust the output voltage to 3.1V". The DC-DC boost converter reduces the output voltage from 5.9V to 3.3V within 100μs, while the low-dropout linear regulator module simultaneously reduces the output voltage to 3.1V. After adjustment, the measured current of the low dropout linear regulator is 178mA, the impedance is restored to 17.4Ω, and the electric field strength is stabilized at 5V (compliant with the specification of 4.2~7.35V at 2cm).

[0060] It should be noted that the above embodiments are merely illustrative examples. The technical solutions of each embodiment can be combined, and all are within the protection scope of this invention.

[0061] The above provides a detailed description of the NFC power adaptive adjustment system and method for EMVCo certification provided by this invention. Any obvious modifications made by those skilled in the art without departing from the essence of this invention will constitute an infringement of the patent rights of this invention and will incur corresponding legal liability.

Claims

1. An NFC power adaptive adjustment system for EMVCo certification, characterized in that... Includes power supply, DC-DC boost converter, power control module, low dropout linear regulator and RF transmitter module; The input terminal of the DC-DC boost converter is connected to the power supply to provide an adjustable first voltage; The input terminal of the low dropout linear regulator is connected to the output terminal of the DC-DC boost converter, and the output terminal of the low dropout linear regulator is connected to the power input terminal of the RF transmitter module to provide an adjustable second voltage and power the RF transmitter module. The low dropout linear regulator integrates a current measurement circuit to measure the load current at the output terminal in real time. The power control module is communicatively connected to the DC-DC boost converter, the low dropout linear regulator, and the radio frequency transmitter module, respectively. The power control module internally stores a mapping table established during the pre-test phase. The mapping table contains the corresponding relationships between the second voltage, load current, and calculated load impedance required to achieve the target field strength at different communication distances. The power control module is configured to, during operation: receive the load current measured by the low-dropout linear regulator and calculate the real-time load impedance in conjunction with the current second voltage; The mapping table is queried to determine the target second voltage corresponding to the real-time load impedance; based on the target second voltage, control commands are generated to coordinately adjust the first voltage output by the DC-DC boost converter and the second voltage output by the low-dropout linear regulator, so that the field strength generated by the RF transmitter module is stabilized within the EMVCo specification range.

2. The NFC power adaptive adjustment system as described in claim 1, characterized in that: The power control module is connected to the first I... 2 The C-bus connects to and controls the DC-DC boost converter, via a second independent I-channel. 2 The C-bus connects to and controls the output voltage of the low-dropout linear regulator, and the SPI bus connects to the low-dropout linear regulator to read the load current measurement data.

3. The NFC power adaptive adjustment system as described in claim 1 or 2, characterized in that: The power control module is further configured to calculate the target second voltage using linear interpolation when the real-time load impedance is between two pre-stored impedance values ​​in the mapping table.

4. The NFC power adaptive adjustment system as described in claim 3, characterized in that: When the power control module adjusts the first voltage output by the DC-DC boost converter, it ensures that the first voltage is always higher than the second voltage output by the low-dropout linear regulator and maintains a preset fixed voltage difference.

5. The NFC power adaptive adjustment system as described in claim 1, characterized in that: A resettable fuse is connected in series between the output terminal of the low dropout linear regulator and the power input terminal of the radio frequency transmitter module.

6. An NFC power adaptive adjustment method for EMVCo certification, implemented based on the NFC power adaptive adjustment system according to any one of claims 1 to 5, characterized in that... Includes the following steps: During the pre-test phase, the second voltage output by the low dropout linear regulator is first adjusted at different communication distances so that the field strength coupled to the test card reaches the predetermined target value within the EMVCo specification range. The second voltage and the load current measured by the internal current measurement circuit of the low dropout linear regulator are recorded simultaneously. The load impedance is calculated, and a mapping table containing distance, second voltage, load current and load impedance is formed and stored. During operation, the load current is monitored in real time through the internal current measurement circuit of the low-dropout linear regulator. Calculate the real-time load impedance based on the second voltage output of the low-dropout linear regulator and the real-time monitored load current. Query the mapping table to determine the target second voltage corresponding to the real-time load impedance; Based on the target second voltage, the first voltage output by the DC-DC boost converter and the second voltage output by the low dropout linear regulator are dynamically and collaboratively adjusted.

7. The NFC power adaptive adjustment method as described in claim 6, characterized in that... The specific steps for adjusting the first voltage output of the DC-DC boost converter are as follows: The target second voltage is added to a preset fixed voltage difference value, and the resulting voltage value is used as the target value of the first voltage for adjustment.

8. The NFC power adaptive adjustment method as described in claim 6, characterized in that: During the pre-testing phase, the predetermined target field strength is set to the same constant value at all test distances, and the constant value is located in the middle region of the EMVCo specification field strength range.

9. The NFC power adaptive adjustment method as described in claim 6, characterized in that: During the working phase, if the calculated real-time load impedance is between two pre-stored impedance values ​​in the mapping table, the target second voltage is calculated using linear interpolation.

10. The NFC power adaptive adjustment method as described in claim 6, characterized in that... It also includes the field strength verification step: After voltage regulation is completed, the field strength is verified by the field strength detection auxiliary circuit inside the radio frequency transmitter module. If the field strength deviation exceeds the tolerance, the pre-test stage process is triggered for recalibration.

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