A resistive load charger test control system with CAN-BMS simulation

Abstract

This invention discloses a resistive load charger test and control system with CAN-BMS simulation, comprising: a system power-on and voltage conversion module for connecting AC power and converting it to low-voltage DC power for controlling the charger under test (DUT) for load testing after system readiness; a main control module for receiving and storing target test parameters and generating a first pulse width modulation signal; a CAN communication transceiver module for generating simulated communication data packets based on the BMS battery management protocol and sending them to the DUT, and receiving charger parameter confirmation signals; a voltage simulation module for receiving relevant signals and outputting an adjustable DC simulated voltage to start the DUT; a power load module including a parallel resistor array and a relay array, the relay array being connected to the main control module; and a sampling feedback module connected between the voltage simulation module and the power load module for acquiring actual voltage and current sampling values. This invention enables automatic closed-loop load testing.

Description

Technical Field

[0001] This invention relates to the field of charging test control technology, and more specifically, to a resistive load charger test control system with CAN-BMS simulation. Background Technology

[0002] As a core component of the golf cart power system, the performance stability and output reliability of the charger directly determine the cart's range and operational safety. Therefore, before leaving the factory, the charger must undergo rigorous load testing to verify key performance indicators such as output power, voltage stability, and operational reliability, ensuring product quality meets usage requirements. The resistive load box, as the core equipment for load testing of the golf cart charger, simulates the load characteristics of the cart battery. By consuming the charger's output power, it detects the charger's operating status and is an indispensable key device in the production and testing process of golf cart chargers.

[0003] Currently, in the scenario of load testing of ball car chargers and resistive loads, mainstream resistive load boxes on the market generally use circuit breaker switching to adjust the operating power. The core principle is to configure resistive heating devices of different power in the internal circuit, and each circuit is equipped with a circuit breaker or other switching device for switching control, thereby realizing the connection or disconnection of the resistive heating devices, and thus forming different load power to complete the load test of the charger. However, with the continuous upgrading of ball car charger technology, especially the widespread application of ball car chargers with communication functions, this traditional resistive load testing method is no longer suitable for testing requirements, gradually exposing many prominent technical defects, seriously affecting testing efficiency and accuracy. For example... Figure 1 As shown, Figure 1 This diagram illustrates the load testing comparison between blind charging and communication-enabled chargers. Existing resistive load banks can only perform load testing on "blind charging" scooter chargers without communication functionality, and cannot be adapted to scooter chargers with communication capabilities. Currently, scooter chargers with communication capabilities and battery packs are mostly custom-made by different manufacturers, resulting in differences in their communication protocols and interface standards. The charger needs to communicate with the Battery Management System (BMS) to obtain battery status information before it can start outputting and complete the charging process. However, existing resistive load banks lack BMS simulation capabilities and cannot establish a communication connection with scooter chargers with communication capabilities. This prevents the charger from completing communication integration verification with the battery pack before shipment, failing to ensure communication compatibility and operational reliability of the charger, posing a serious quality risk. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a resistive load charger test and control system with CAN-BMS simulation, comprising the following modules: The system power-on and voltage conversion module is used to connect to AC power and press the start button to convert high-voltage AC power into low-voltage DC power. Based on the low-voltage DC power, after the entire system is in a ready state, pressing the load button controls the relay to activate and execute the load test corresponding to the charger under test with CAN communication. The main control module is electrically connected to the system power-on and voltage conversion module. It is used to receive and store the target test voltage and target test current input by the key, and generate a first pulse width modulation signal based on the target test voltage. The CAN communication transceiver module is electrically connected to the main control module. It is used to receive the target test voltage and target test current from the main control module, generate BMS analog communication data packets based on the preset BMS battery management protocol, and actively send them to the charger under test through the internal CAN transceiver circuit. At the same time, it receives the charger parameter confirmation signal returned by the charger under test. The voltage simulation module is electrically connected to the main control module and the CAN communication transceiver module. It is used to receive the first pulse width modulation signal and the charger parameter confirmation signal, and drive the internal DC-DC power module based on the charger parameter confirmation signal to output an adjustable DC analog voltage corresponding to the target test voltage according to the first pulse width modulation signal, so as to ensure that the charger under test detects the presence of voltage at the output terminal BAT+ and starts. A power load module, comprising multiple parallel resistor arrays and a relay array for controlling the connection or disconnection of the resistor arrays, wherein the relay array is connected to the main control module; A sampling feedback module is connected between the output of the voltage simulation module and the input of the power load module. It is used to collect the actual voltage and current sampling values ​​of the power load module in real time and send them to the main control module. The main control module is further configured to receive the charger parameter confirmation signal and parse it to obtain the maximum allowable output voltage and maximum allowable output current of the charger under test, and calculate the target equivalent load power by combining the target test voltage and target test current. At the same time, it generates an initial relay group control sequence based on the pre-stored resistor group-power mapping relationship, and controls the relays of the corresponding group in the power load module to activate and output the actual voltage sample value and the actual current sample value. The actual voltage sample value is compared with the target test voltage to generate a voltage deviation value, and the duty cycle of the first pulse width modulation signal is dynamically adjusted according to the voltage deviation value to generate a second pulse width modulation signal to adjust the adjustable DC analog voltage in a closed loop. The main control module also compares the collected actual voltage and current sampling values ​​with the target test voltage and target test current to calculate the real-time power deviation value. Based on the magnitude and direction of the real-time power deviation value, it dynamically adjusts the initial relay group control sequence to generate load adjustment commands, and controls the power load module to increase or decrease the connected resistor groups in order to complete the automatic closed-loop load test of the charger under test.

[0005] The beneficial effects of this application are as follows: 1. The system power-on and voltage conversion module, connected to AC power and controlled by a button, converts high-voltage AC to low-voltage DC to power the system, ensuring system readiness. It then controls the relay to engage and execute the load test on the charger under test. This module first converts high-voltage AC to stable low-voltage DC, providing safe and reliable power support for the entire test system, ensuring the normal readiness of all modules and preventing test results from being affected by unstable power supply. The separate control of the start and load buttons allows for a seamless transition between system readiness and load testing. Pressing the load button engages the relay, executing the load test on the charger under test with CAN communication, overcoming the limitation of traditional load boxes that cannot adapt to the start-up of chargers with communication capabilities.

[0006] 2. The main control module is electrically connected to the system power-on and voltage conversion module. It receives and stores target test parameters, generates pulse width modulation (PWM) signals, and simultaneously analyzes charger parameters and performs closed-loop voltage and load regulation. As the core of the system, this module can receive and store the target test voltage and current input via buttons, providing a clear parameter reference for testing. It also generates the first PWM signal based on the target test voltage, providing control basis for voltage simulation. By analyzing the charger parameter confirmation signal transmitted from the CAN communication transceiver module, the maximum allowable output parameters of the charger under test are obtained. Combined with the target test parameters, the target equivalent load power is calculated, and an initial relay group control sequence is generated to achieve preliminary load regulation. Subsequently, by comparing the actual sampled values ​​with the target parameters, the PWM signal and relay group control sequence are dynamically adjusted to achieve closed-loop voltage and load regulation, overcoming the limitations of traditional load banks that cannot be dynamically adjusted or analyze charger parameters.

[0007] 3. The CAN communication transceiver module is electrically connected to the main control module, generating BMS simulated communication data packets and sending them to the charger under test (DUT). Simultaneously, it receives parameter confirmation signals from the charger. Based on a preset BMS battery management protocol, this module converts the target test voltage and current from the main control module into BMS simulated communication data packets, actively sending them to the DUT via its internal CAN transceiver circuit. This simulates the communication interaction between the real battery management system and the charger, addressing the core pain point of traditional load banks lacking BMS simulation functionality. Furthermore, this module can receive parameter confirmation signals from the DUT and transmit them to the main control module, enabling bidirectional communication between the charger and the test system. This ensures the charger can start and output normally, laying the foundation for subsequent load testing. This module overcomes the limitation of traditional load banks being unable to adapt to chargers with communication capabilities, enabling communication integration and verification of chargers with CAN communication. It effectively tests the charger's communication compatibility and operational reliability, avoiding potential quality issues caused by communication problems.

[0008] 4. The voltage simulation module is electrically connected to the main control module and the CAN communication transceiver module. It receives relevant signals and drives the DC-DC power module to output an adjustable DC analog voltage. This module receives the first pulse width modulation signal generated by the main control module and the charger parameter confirmation signal from the CAN communication transceiver module. After ensuring that the charger has completed communication interaction, it drives the internal DC-DC power module to output an adjustable DC analog voltage corresponding to the target test voltage according to the pulse width modulation signal, simulating the output state of a real battery. This allows the charger under test to detect the presence of voltage at the output terminal BAT+ and start normally. This module overcomes the limitation of traditional load boxes that cannot simulate battery voltage and solves the problem of chargers with communication failing to start due to the inability to detect voltage, ensuring that load testing can be carried out smoothly. At the same time, the adjustable DC analog voltage can adapt to the voltage requirements of different specifications of chargers with communication, improving the versatility of the test system, further ensuring the accuracy and reliability of the test, and avoiding test failures caused by abnormal voltage simulation.

[0009] 5. The power load module includes multiple parallel resistor arrays and relay arrays. The relay arrays are connected to the main control module and receive control commands to switch resistor groups. This module uses multiple parallel resistor arrays, and by combining different resistor groups, it can achieve load outputs of various power specifications, adapting to different testing requirements with communication chargers, breaking the limitations of fixed resistor configurations in traditional load boxes. The relay arrays, connected to the main control module, can receive control commands from the main control module, enabling rapid connection or disconnection of the resistor arrays. Compared to traditional circuit breaker switching methods, this offers faster response speed, more convenient adjustment, and automated adjustment, eliminating the need for manual operation and significantly improving testing efficiency. By dynamically adjusting the relay group control sequence through the main control module, the connected resistor groups can be adjusted to achieve dynamic adaptation of the load power, ensuring that the load power matches the target test power.

[0010] 6. The sampling feedback module connects between the voltage simulation module and the power load module, acquiring real-time voltage and current samples and sending them to the main control module. This module also collects real-time voltage and current samples from the power load module, capturing voltage and current changes during the test and promptly sending the collected data to the main control module. This provides reliable feedback data for the main control module's closed-loop adjustment. Through this feedback data, the main control module can compare actual and target parameters, identify voltage and current deviations, and dynamically adjust the pulse width modulation signal and load resistance group to achieve closed-loop control of voltage and load, ensuring stable and accurate testing. This module overcomes the limitations of traditional load banks that lack sampling feedback and dynamic adjustment, enabling real-time monitoring and data feedback during the testing process. This improves the accuracy and stability of the test, providing reliable data support for quality testing of devices with communication chargers. Attached Figure Description

[0011] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the module structure of the resistive load charger test control system with CAN-BMS simulation in this embodiment; Figure 2 This is a schematic diagram of the electrical principle of the system power-on and voltage conversion module in this embodiment; Figure 3 This is a schematic diagram of the electrical principle of the main control module in this embodiment; Figure 4 This is a schematic diagram of the electrical principle of the CAN communication transceiver module in this embodiment; Figure 5 This is a schematic diagram of the electrical principle of the voltage simulation module in this embodiment; Figure 6 This is a schematic diagram of the electrical principle of the power load module in this embodiment; Figure 7 This is a schematic diagram of the electrical principle of the sampling feedback module in this embodiment; Figure 8 for Figure 1 A functional flowchart of the CAN communication transceiver module. Detailed Implementation

[0012] The following drawings disclose several embodiments of the present invention. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details are not intended to limit the invention. That is, in some embodiments of the invention, these practical details are not essential. Furthermore, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner.

[0013] To further understand the invention's content, features, and effects, the following embodiments are provided, and detailed descriptions are given below in conjunction with the accompanying drawings: Reference Figure 1-7 , Figure 1 This is a schematic diagram of the module structure of the resistive load charger test control system with CAN-BMS simulation in this embodiment; Figure 2 This is a schematic diagram of the electrical principle of the system power-on and voltage conversion module in this embodiment; Figure 3 This is a schematic diagram of the electrical principle of the main control module in this embodiment; Figure 4 This is a schematic diagram of the electrical principle of the CAN communication transceiver module in this embodiment; Figure 5 This is a schematic diagram of the electrical principle of the voltage simulation module in this embodiment; Figure 6 This is a schematic diagram of the electrical principle of the power load module in this embodiment; Figure 7 This is a schematic diagram of the electrical principle of the sampling feedback module in this embodiment. The resistive load charger test and control system with CAN-BMS simulation in this embodiment includes the following modules: The system power-on and voltage conversion module is used to connect to AC power and press the start button to convert high-voltage AC power into low-voltage DC power. Based on the low-voltage DC power, after the entire system is in a ready state, pressing the load button controls the relay to activate and execute the load test corresponding to the charger under test with CAN communication. In this embodiment of the invention, the system power-on and voltage conversion module is connected to 220V high-voltage AC power. The AC input terminal is equipped with a power interface, which integrates a surge protection circuit to suppress voltage fluctuations during connection and ensure stable module operation. The module contains an HLK-PM12 power conversion unit. The input terminal of this unit is connected to the 220V high-voltage AC power interface. A temperature control switch and a load button are connected in series at the input terminal. An emergency stop button is connected in series with the temperature control switch and grounded. A freewheeling diode is connected in parallel across the relay. The freewheeling diode has a forward conduction voltage of 0.7V and a reverse breakdown voltage of 200V, which can quickly dissipate the voltage spikes generated after the relay disconnects, preventing damage to other electronic components within the module. When the operator presses the start button, the power supply circuit of the power conversion unit is activated, and the HLK-PM12 power conversion unit begins operation, converting the 220V high-voltage AC power to 12V low-voltage DC power. During the conversion process, the AC power is converted to DC power through an internal rectifier circuit, and then the voltage is stabilized at 12V through a voltage regulator circuit. The conversion efficiency is 85%, and the output current is stabilized at 1A. A 12V low-voltage DC power supply is provided to all operating modules of the system, including the main control module, CAN communication transceiver module, and voltage simulation module, ensuring stable power for each module. Upon receiving power, each module enters a ready state. At this time, the indicator light on the main control module illuminates, the CAN communication transceiver module enters standby mode, and the voltage simulation module completes initialization. Once all modules are in a ready state, the operator presses the load button. The load button closes, triggering the main control module to generate a relay energizing signal. This signal is transmitted to the relay coil via a GPIO pin. The relay coil, energized, generates electromagnetic attraction, controlling the relay contacts to close, connecting the charger under test (DUT) with CAN communication to the power load module, initiating the load test for the DUT. After ensuring a stable test circuit connection, the system proceeds to the subsequent testing process. Alternatively, the voltage can be converted to 5V or 3.3V.

[0014] The main control module is electrically connected to the system power-on and voltage conversion module. It is used to receive and store the target test voltage and target test current input by the key, and generate a first pulse width modulation signal based on the target test voltage. In this embodiment of the invention, the main control module is electrically connected to the system power-on and voltage conversion module via wires. It receives 12V low-voltage DC power from the system power-on and voltage conversion module, converts it to 3.3V DC power via an internal step-down circuit, and powers the internal arithmetic circuit and storage unit. The main control module is equipped with a key input unit containing two independent keys, corresponding to the target test voltage input and the target test current input, respectively. The operator inputs the target test voltage and target test current by pressing the keys. During the input process, the key input unit converts the pressing signal into an electrical signal, which is transmitted to the internal arithmetic circuit of the main control module. After receiving the electrical signal, the arithmetic circuit shapes the signal to remove noise, and then converts the electrical signal into the corresponding value. The target test voltage is set to 45V, and the target test current is set to 12A. The arithmetic circuit transmits these two values ​​to the storage unit. The storage unit uses non-volatile storage, which can permanently save the input target parameters and prevent parameter loss after system power failure. The main control module has a pulse width modulation (PWM) signal generation circuit. This circuit receives the target test voltage of 45V transmitted from the storage unit and generates a first PWM signal based on the correspondence between the target test voltage and the duty cycle of the PWM signal. The calculation process is: duty cycle = target test voltage / maximum output voltage. The maximum output voltage is set to 100V, so the duty cycle = 45V / 100V = 45%. The PWM signal generation circuit generates a square wave signal with a duty cycle of 45%. The square wave signal frequency is set to 10kHz, the high-level voltage is 3.3V, and the low-level voltage is 0V. The generated first PWM signal is transmitted to the voltage simulation module to provide control basis for the subsequent adjustable DC analog voltage output.

[0015] The CAN communication transceiver module is electrically connected to the main control module. It is used to receive the target test voltage and target test current from the main control module, generate BMS analog communication data packets based on the preset BMS battery management protocol, and actively send them to the charger under test through the internal CAN transceiver circuit. At the same time, it receives the charger parameter confirmation signal returned by the charger under test. In this embodiment of the invention, the CAN communication transceiver module is electrically connected to the main control module through the TXD and RXD interfaces. It receives the target test voltage of 45V and the target test current of 12A transmitted by the main control module. The module contains a CAN transceiver circuit and a protocol processing circuit. The protocol processing circuit has a preset BMS battery management protocol, which specifies the data frame format, transmission rate, verification method and other contents. After receiving the target test voltage and target test current, the protocol processing circuit converts both parameters into binary data. The target test voltage of 45V is converted into 16-bit binary data: 0000000000101101. The target test current of 12A is converted into 16-bit binary data: 0000000000001100. Then, according to the frame format specified by the BMS battery management protocol, an 8-bit frame header (00110101) is added before the binary data, followed by an 8-bit frame tail (11001010). A 4-bit check bit is inserted in between. The check bit is generated by XORing the frame header and the data part. The operation process is to XOR each bit of the frame header with the corresponding data bit, ultimately obtaining a 4-bit check bit (0101). After combination, a complete BMS analog communication data packet is generated. The CAN transceiver circuit receives the BMS analog communication data packet transmitted by the protocol processing circuit, converts the data packet into a CAN bus-compatible differential signal, sets the transmission rate to 500kbps, and actively sends it to the charger under test via the CAN bus at a transmission frequency of 1 time / second to ensure that the charger under test can stably receive the data packet. Simultaneously, the CAN transceiver circuit enters a listening state, listening for the charger parameter confirmation signal returned by the charger under test. During the listening process, the received signal is filtered to remove noise generated by electromagnetic interference. When the charger parameter confirmation signal is received, the signal is transmitted to the protocol processing circuit. The protocol processing circuit parses the signal and extracts parameters such as the protocol version, maximum output voltage, and maximum output current of the charger under test. The parsed signal is then transmitted to the main control module and the voltage simulation module.

[0016] The voltage simulation module is electrically connected to the main control module and the CAN communication transceiver module. It is used to receive the first pulse width modulation signal and the charger parameter confirmation signal, and drive the internal DC-DC power module based on the charger parameter confirmation signal to output an adjustable DC analog voltage corresponding to the target test voltage according to the first pulse width modulation signal, so as to ensure that the charger under test detects the presence of voltage at the output terminal BAT+ and starts. In this embodiment of the invention, the voltage simulation module is electrically connected to the main control module via a GPIO interface and to the CAN communication transceiver module via a CAN bus. It receives the first pulse-width modulation signal transmitted by the main control module and the charger parameter confirmation signal transmitted by the CAN communication transceiver module, respectively. The voltage simulation module internally includes a DC-DC power supply module and a drive circuit. After receiving the charger parameter confirmation signal, the drive circuit analyzes the maximum output voltage parameter in the signal. If the maximum output voltage is not lower than the target test voltage of 45V, the drive circuit generates a drive signal to start the DC-DC power supply module. If the maximum output voltage is lower than the target test voltage of 45V, the drive circuit does not generate a drive signal, the DC-DC power supply module is in standby mode, and an abnormal signal is fed back to the main control module. After the DC-DC power supply module starts, it receives the first pulse-width modulation signal transmitted by the main control module. This signal controls the on and off times of the power devices inside the DC-DC power supply module. The ratio of the on time to the off time of the power devices is equal to the duty cycle of the first pulse-width modulation signal, which is 45%. The DC-DC power module converts the 12V low-voltage DC power supplied by the system power-on and voltage conversion module into an adjustable DC analog voltage corresponding to the target test voltage. During the conversion process, the output voltage is monitored in real time through an internal feedback circuit. The detected actual output voltage is compared with the target test voltage of 45V, and the voltage difference is calculated. If the actual output voltage is lower than 45V, the feedback circuit controls the power device to increase the conduction time and increase the output voltage. If the actual output voltage is higher than 45V, the feedback circuit controls the power device to decrease the conduction time and decrease the output voltage. After multiple adjustments, a stable 45V adjustable DC analog voltage is output. This voltage is delivered to the output terminal BAT+ of the charger under test, ensuring that the charger under test starts after detecting a stable voltage at the output terminal, thus preparing for subsequent load testing.

[0017] A power load module, comprising multiple parallel resistor arrays and a relay array for controlling the connection or disconnection of the resistor arrays, wherein the relay array is connected to the main control module; In this embodiment of the invention, the power load module is electrically connected to the main control module and the voltage simulation module. The core comprises 11 parallel arrays of resistor bars and corresponding relay arrays. The resistance values ​​of the 11 resistor bar arrays are set to 1Ω, 2Ω, 4Ω, 8Ω, 16Ω, 32Ω, 64Ω, 128Ω, 256Ω, 512Ω, and 1024Ω, respectively. Each resistor bar array consists of 3-5 resistor bars of the same resistance value connected in series. The rated power of a single resistor bar is 50W, ensuring that each array can withstand the target test power. The relay array contains 11 independent relays, each corresponding to one resistor bar array. One end of the relay is connected to the resistor bar array, and the other end is electrically connected to the GPIO pin of the main control module to receive control signals output by the main control module. Each resistor bar array and its corresponding relay are connected in series and then connected in parallel to the input and output terminals of the power load module. The input terminal is connected to the sampling feedback module to receive the adjustable DC analog voltage output by the voltage simulation module, and the output terminal is grounded, forming a complete load circuit. When the relay does not receive a pull-in signal, the contacts are open, and the corresponding resistor array is not connected to the load circuit. After the relay receives the pull-in signal from the main control module, the coil is energized to generate electromagnetic attraction, the contacts close, and the corresponding resistor array is connected to the load circuit. By controlling the pull-in and pull-out of different relays, different equivalent load resistance values ​​can be formed to meet the test requirements of different target power, which is in line with the core load regulation requirements of the resistive load charger test control system with CAN-BMS simulation.

[0018] A sampling feedback module is connected between the output of the voltage simulation module and the input of the power load module. It is used to collect the actual voltage and current sampling values ​​of the power load module in real time and send them to the main control module. In this embodiment of the invention, one end of the sampling feedback module is connected to the output of the voltage analog module via a wire, and the other end is connected to the input of the power load module. It is electrically connected to the main control module via an SPI interface. The core includes a U2-B voltage sampling submodule, a U2-A voltage follower submodule, and a current sampling submodule. The voltage sampling submodule uses a voltage divider network composed of R73, R74, R76, and R77 to proportionally reduce the high-voltage DC power at the input of the power load module. After voltage division, two differential signals are obtained. After current limiting by R75 and R78, they are sent to the inverting and non-inverting inputs of the operational amplifier. R79 balances the impedance of the upper and lower voltage divider arms and provides a discharge circuit. C16 and C18 filter out high-frequency interference. R81 provides DC bias. R80 and C17 form a feedback network to realize amplification and filtering. R82 and C19 ensure the accuracy of ADC sampling. Finally, the analog voltage signal is converted into the actual digital voltage sample value. The voltage follower submodule generates a stable 1.65V DC reference voltage using the U2-A operational amplifier and components such as R83 and R84, providing low-impedance bias for the sampling operational amplifier. The current sampling submodule uses R85 and R90 for current limiting, L2 for interference suppression, C24 and C25 for combined filtering, and milliohm-level sampling resistors R86-R89 to acquire the current voltage drop. D16 clamps and protects the ADC interface, converting the current signal into a digital actual current sample value. Both sample values ​​are transmitted to the main control module in real time, providing data support for subsequent power calculations and closed-loop regulation.

[0019] The main control module is further configured to receive the charger parameter confirmation signal and parse it to obtain the maximum allowable output voltage and maximum allowable output current of the charger under test, and calculate the target equivalent load power by combining the target test voltage and target test current. At the same time, it generates an initial relay group control sequence based on the pre-stored resistor group-power mapping relationship, and controls the relays of the corresponding group in the power load module to activate and output the actual voltage sample value and the actual current sample value. The actual voltage sample value is compared with the target test voltage to generate a voltage deviation value, and the duty cycle of the first pulse width modulation signal is dynamically adjusted according to the voltage deviation value to generate a second pulse width modulation signal to adjust the adjustable DC analog voltage in a closed loop. In this embodiment of the invention, the main control module receives the charger parameter confirmation signal transmitted by the CAN communication transceiver module, analyzes the signal through its internal processing circuit, extracts the maximum allowable output voltage of 50V and the maximum allowable output current of 15A from the charger under test, and stores them in the internal storage unit. Combining the target test voltage of 45V and the target test current of 12A input in step S02, the target equivalent load power is calculated by multiplication: Target equivalent load power = Target test voltage × Target test current = 45V × 12A = 540W. The main control module pre-stores a resistor group-power mapping relationship, which includes the resistance value, single-group power, and combined total resistance and total power of 11 resistor arrays. The mapping relationship is generated based on the resistance value of each resistor array and the target test voltage, where the single-group power = target test voltage. 2 / Single group resistance value, for example, the power of a single group of a 4Ω resistor bar array = (45V) 2 / 4Ω=506.25W. Based on this mapping relationship, calculate the target equivalent resistance corresponding to the target equivalent load power = (45V) 2 Given 540W = 3.75Ω, the system iterates through all resistor combinations, selecting the closest to 3.75Ω to determine the relay corresponding to the 4Ω resistor array. An initial relay group control sequence is generated, controlling the corresponding relays to engage and outputting the actual voltage and current sample values. The main control module compares the actual voltage sample value with the target test voltage of 45V, generating a voltage deviation value. If the actual voltage sample value is 44.2V, the voltage deviation value = 45V - 44.2V = 0.8V. Based on the voltage deviation value, the duty cycle of the first pulse width modulation signal is adjusted. The adjustment amount is calculated as: voltage deviation value / target test voltage × 100% = 0.8V / 45V × 100% ≈ 1.78%. The duty cycle is adjusted from 45% to 46.78%, generating the second pulse width modulation signal, which is transmitted to the voltage simulation module for closed-loop adjustment of the adjustable DC analog voltage.

[0020] The main control module also compares the collected actual voltage and current sampling values ​​with the target test voltage and target test current to calculate the real-time power deviation value. Based on the magnitude and direction of the real-time power deviation value, it dynamically adjusts the initial relay group control sequence to generate load adjustment commands, and controls the power load module to increase or decrease the connected resistor groups in order to complete the automatic closed-loop load test of the charger under test.

[0021] In this embodiment of the invention, the main control module receives the actual voltage and current sampling values ​​transmitted by the sampling feedback module in real time. The actual power is calculated by multiplication: Actual power = Actual voltage sampling value × Actual current sampling value. If the actual voltage sampling value is 44.2V and the actual current sampling value is 11.8A, the actual power = 44.2V × 11.8A ≈ 521.56W. The actual power is compared with the target equivalent load power of 540W, and the real-time power deviation is calculated as 540W - 521.56W = 18.44W. A positive deviation indicates insufficient actual load, and the adjustment direction is to increase the load. The optimal resistance change is calculated based on the real-time power deviation. Ro = (45V) 2 (540W) - (45V) 2 / (540W-18.44W))≈3.75Ω-3.91Ω=-0.16Ω, the equivalent resistance needs to be reduced. Obtain the total equivalent resistance of the currently engaged relay (4Ω), and calculate the target total equivalent resistance = (45V). 2 / (521.56W-((45V)) 2 / (4Ω) 2 (-0.16Ω) ≈ 3.74Ω. Iterate through the resistor combinations, selecting the one closest to 3.74Ω. Adjust the initial relay group control sequence, adding a relay corresponding to the 64Ω resistor array, generating a load adjustment command, and controlling the power load module to add more resistor groups. Continuously execute the sampling, calculation, and adjustment process, updating the sampled value and adjustment command every 500 milliseconds until the real-time power deviation is controlled within ±5W, thus completing the automatic closed-loop load test of the charger under test.

[0022] Furthermore, the system power-on and voltage conversion module also includes a temperature control switch, an emergency stop button, and a freewheeling diode; the temperature control switch is connected in series with the load button, the emergency stop button is connected in series with the temperature control switch and then grounded, and the freewheeling diode is connected in parallel across the relay to dissipate the voltage spikes after the relay is disconnected. The continuous operation after being connected to AC power specifically refers to: After AC power is connected, the main control module continuously monitors the status of the start button. When the start button is detected to be pressed, a system power-on enable signal is generated, which controls the relay to engage to supply power to the main circuit of the system and start the cooling fan. Temperature sensors are arranged at the heat dissipation points of the power load module to collect the temperature data of the resistance rod array in real time and generate a temperature monitoring signal. The temperature monitoring signal is compared with a preset first temperature warning threshold and a second temperature protection threshold. If the temperature monitoring signal exceeds the first temperature warning threshold, the main control module generates a derating control command, which is used to reduce the calculated value of the target equivalent load power and trigger the power load module to reduce the number of connected resistor branches. If the derating cannot be performed due to extreme testing, the cooling fan speed is increased. If the temperature monitoring signal reaches the second temperature protection threshold, the temperature control switch automatically disconnects, forcibly cutting off the power supply circuit of the connecting relay coil, causing the connecting relay to disconnect. When the temperature drops to the second temperature protection threshold of -15°C, the temperature control switch automatically closes and reconnects the relay. Alternatively, in an emergency, pressing the emergency stop button disconnects the circuit relay.

[0023] In this embodiment of the invention, in the system power-on and voltage conversion module, the temperature control switch is connected in series with the load button, the emergency stop button is connected in series with the temperature control switch and grounded, and the freewheeling diode is connected in parallel across the relay. The forward conduction voltage of the freewheeling diode is set to 0.7V, and the reverse breakdown voltage is not less than 200V. This allows for rapid dissipation of the voltage spikes generated after the relay is disconnected, preventing damage to other electronic components within the module and ensuring circuit safety. After the system is connected to 220V AC power, the HLK-PM12 small power supply module converts the 220V AC power to 12V DC power, providing the foundation for powering the entire system and subsequent voltage conversion. At this time, the main control module enters standby mode and simultaneously starts the cooling fan. The initial speed of the cooling fan is set to 1500 rpm to begin pre-cooling the power load module. The main control module continuously monitors the status of the start button at a frequency of 10 times per second. When the start button is detected as pressed, a system power-on enable signal is immediately generated. This signal is transmitted to the relay coil via a GPIO pin, controlling the relay to engage and powering on the main circuit. This provides power to all working modules, including the power load module and the CAN communication transceiver module, while simultaneously maintaining the normal operation of the cooling fan. Temperature sensors are placed at the heat dissipation points of the power load module, with each sensor positioned close to the surface of the resistance rod array. One sensor is placed for each resistance rod, collecting temperature data from the array in real time at a 500-millisecond interval. The collected analog temperature signal is converted into a digital signal to generate a temperature monitoring signal, which is then transmitted to the main control module. The main control module internally presets a first temperature warning threshold and a second temperature protection threshold. Based on the specifications, the first temperature warning threshold is set to 95℃, and the second temperature protection threshold is set to 105℃. The received temperature monitoring signal is compared with these two thresholds in real time to determine the temperature status of the resistance rod array. If the temperature monitoring signal exceeds the first temperature warning threshold but does not reach the second temperature protection threshold, it indicates that the resistance rod temperature is too high but has not reached a dangerous state. The main control module generates a derating control command. This command reduces the calculated value of the target equivalent load power based on the difference between the current temperature and the first temperature warning threshold. The calculation method is: drated target power = original target power × (1 - (current temperature - 95℃) / 10℃). For example, if the current temperature is 100℃ and the original target power is 1000W, the drated target power = 1000W × (1 - (100 - 95) / 10) = 500W. The command triggers the power load module to reduce the number of connected resistance rod branches. By disconnecting the corresponding relay, the number of connected resistance rods is reduced, the actual load power is reduced, and the heat generation is reduced. If the extreme test cannot drate, the main control module outputs a control signal to increase the speed of the cooling fan to 3000 rpm, enhance the heat dissipation effect, and suppress the continuous rise in temperature.If the temperature monitoring signal reaches the second temperature protection threshold, the internal contacts of the temperature control switch automatically open, cutting off the power supply circuit to the relay coil. The relay, deprived of power, disconnects, cutting off the power supply to the power load module and stopping the load test to prevent damage to the resistance rod due to high temperature. When the resistance rod temperature drops to the second temperature protection threshold -15℃ (90℃), the internal contacts of the temperature control switch automatically close, reconnecting the power supply circuit to the relay coil. The relay re-energizes, restoring power to the power load module and allowing the test to continue. In case of an emergency during testing, pressing the emergency stop button will break the series circuit of the emergency stop button, causing the relay coil to disconnect after losing power, quickly cutting off the connection between the charger and the load to prevent the accident from escalating and ensuring the safety of equipment and personnel. After pressing the emergency stop button, it must be manually reset before the circuit can be closed again and the system restarted.

[0024] Furthermore, such as Figure 8 As shown, Figure 8 for Figure 1 A functional flowchart of the CAN communication transceiver module is shown. In this embodiment, the CAN communication transceiver module includes the following functions: S301: Receive the target test voltage and target test current from the main control module and encapsulate them into parameter request frame data based on the preset BMS battery management protocol; S302: Query the pre-stored multi-charger protocol identifier library to generate protocol version query frame data; S303: Combine the protocol version query frame data and parameter request frame data according to the preset communication timing to generate a BMS simulated communication data packet; S304: Actively broadcasts BMS analog communication data packets to the charger under test via the transmit pin corresponding to the internal CAN transceiver circuit, and listens for the charger parameter confirmation signal from the charger under test, which includes its protocol version and maximum output capability.

[0025] In this embodiment of the invention, a CAN transceiver module with a built-in CAN transceiver circuit is used. This circuit includes a CAN transceiver chip and an external filtering circuit. The filtering circuit suppresses electromagnetic interference during communication, ensuring stable communication signals. The module establishes a physical connection with the main control module and the charger under test. A 12V low-voltage power supply wakes up the module, putting it into operation. The module receives the target test voltage and target test current sent by the main control module. The target test voltage range is 24V~100V, and the target test current is set according to the test requirements. Based on a preset BMS battery management protocol, the module encapsulates the target test voltage and target test current data. The encapsulation process follows the frame format specified by the BMS battery management protocol, converting the target test voltage and target test current into binary data, adding a frame header, frame trailer, and check bit, and generating parameter request frame data. The check bit is generated through an XOR operation to ensure no data loss or error occurs during data transmission. The module internally stores multiple charger protocol identifier libraries. These libraries contain protocol version identifiers, communication addresses, and other information for different types of chargers. The module iterates through these libraries to find protocol identifiers matching the type of charger under test. Based on communication timing requirements, it generates a protocol version query frame. This frame contains a query command and the module's own protocol version information, used to inquire with the charger under test about supported protocol versions. Following a preset communication timing sequence, the module combines the protocol version query frame with parameter request frames. The combination order is: first, the protocol version query frame is sent, followed by a 50-millisecond interval before the parameter request frame is sent to avoid conflicts. This generates a complete BMS simulated communication data packet containing two core types of information: protocol query and target parameter request, enabling bidirectional communication with the charger under test. The module actively broadcasts BMS analog communication data packets to the charger under test (DUT) via the transmit pin of its internal CAN transceiver circuit. The broadcast frequency is set to once per second to ensure the DUT can receive the data packets. Simultaneously, the module activates a listening mode, listening for the DUT's response parameter confirmation signal via the receive pin of the CAN transceiver circuit. The listening timeout is set to 5 seconds. If no response is received within the timeout, the module will rebroadcast the BMS analog communication data packets, repeating the broadcast a maximum of 3 times. Upon receiving the BMS analog communication data packets, the DUT parses the protocol version query and parameter request information, compares its own protocol version with the protocol version sent by the module to confirm protocol compatibility, and determines whether its maximum output capacity meets the target test voltage and current requirements. It then generates a charger parameter confirmation signal containing its own protocol version, maximum output voltage, and maximum output current, and sends it to the CAN communication transceiver module. Upon receiving this signal, the module transmits it to the main control module, providing data support for subsequent load power control and test initiation. This enables load testing of communication chargers without the need for a real battery, meeting the testing requirements of communication chargers.

[0026] Furthermore, the analysis to obtain the maximum allowable output voltage and maximum allowable output current of the charger under test, and the calculation of the target equivalent load power in combination with the target test voltage and target test current, includes: The main control module receives a charger parameter confirmation signal from the CAN communication transceiver module and extracts the parameter code representing the maximum output capability from the charger parameter confirmation signal. The parameter code is in an encrypted or compressed format. According to a preset decoding mapping table corresponding to the protocol version of the charger under test, the parameter code is decoded to restore the maximum permissible output voltage rating of the charger under test under standard conditions. and maximum permissible output current rating ; Based on temperature monitoring signal and maximum permissible output voltage rating and maximum permissible output current rating The temperature-permissible output derating curve is generated by coupling, and the permissible output derating factor corresponding to the current temperature is obtained based on the temperature-permissible output derating curve; Based on the allowable output derating factor and combined with the maximum allowable output voltage rating and maximum permissible output current rating The maximum permissible output voltage of the tested charger at the current temperature was calculated. With maximum allowable output current ; Target test voltage Target test current The maximum permissible output voltage actually available for the charger under test. With maximum allowable output current When comparing, ≤ and ≤ Then, based on the target test voltage With the target test current Multiplication to calculate target equivalent load power .

[0027] In this embodiment of the invention, the main control module receives a charger parameter confirmation signal from the CAN communication transceiver module. This signal contains core information such as the protocol version of the charger under test, maximum output capability, and temperature derating parameters. The main control module parses the signal and extracts the parameter code representing the maximum output capability. This parameter code uses a compressed encoding format, compressing the rated values ​​of the maximum allowable output voltage and maximum allowable output current into 16-bit binary codes. The high 8 bits correspond to the rated value of the maximum allowable output voltage, and the low 8 bits correspond to the rated value of the maximum allowable output current. Compression encoding reduces data transmission volume and ensures transmission efficiency. The main control module internally stores a preset decoding mapping table corresponding to different charger protocol versions. The decoding mapping table defines the correspondence between parameter codes and actual rated values ​​according to different protocol versions. Each protocol version corresponds to a unique decoding mapping rule. The main control module calls the corresponding decoding mapping table according to the protocol version of the charger under test to decode the parameter code. First, the 16-bit binary parameter code is split into high 8 bits and low 8 bits. Then, the binary data is converted into decimal rated values ​​through the decoding mapping table to restore the rated value of the maximum allowable output voltage of the charger under test under standard conditions. and maximum permissible output current rating For example, after decoding, we get =60V, =20A. During the load test initialization phase, the main control module further extracts and stores the derating coefficients of voltage and current at corresponding temperatures, as well as the charger temperature inflection point derating sequence at corresponding voltages and currents, from the parsed charger parameter confirmation signal. The derating coefficients are set to 0.1 for every 10°C increase in voltage and 0.15 for every 10°C increase in current. The charger temperature inflection point derating sequence contains multiple consecutive temperature inflection point values. The temperatures are set sequentially from low to high as follows: 25℃, 35℃, 45℃, 55℃, and 65℃, with each temperature inflection point value... Corresponding to a unique voltage derating factor and current derating factor The inflection point derating rule is set as follows: when the temperature is 25℃ (standard temperature), =1.0、 =1.0; when the temperature reaches 35℃, =0.9、 =0.85; when the temperature reaches 45℃, =0.8、 =0.7; when the temperature reaches 55℃, =0.7、 =0.55; when the temperature reaches 65℃, =0.6、 =0.4, forming a complete temperature inflection point derating sequence, which is stored in the internal cache area of ​​the main control module for subsequent real-time calculation. After starting the load test, the main control module continuously reads the temperature monitoring signal from the thermistor, with a reading frequency consistent with the temperature sensor's acquisition period of 500 milliseconds. The received temperature monitoring signal is then converted into a real-time temperature sampling value reflecting the current temperature of the charger under test. For example, the converted value yields a real-time temperature sample value. =40℃. The main control module will display the real-time temperature sample value. The derating factor is calculated by comparing the charger temperature inflection point derating sequence with the cached data, and each temperature inflection point value is checked individually. The matching was performed to calculate the value of each temperature inflection point. Corresponding voltage derating factor and current derating factor This ensures that the derating coefficients corresponding to all inflection points are accurately calculated, and the calculation process strictly adheres to the pre-stored inflection point derating rules to avoid deviations. This is based on each temperature inflection point value. Corresponding voltage derating factor and current derating factor A piecewise linear interpolation method is used, based on real-time temperature sampling values. The temperature range in which it is located is used to calculate the corresponding current temperature. Real-time voltage derating factor and real-time current derating factor For example, real-time temperature sampling value =40℃, which is between the two inflection points of 35℃ and 45℃, calculate the real-time voltage derating factor. = -( -35℃) × ( - ) / (45℃-35℃)=0.9-(40℃-35℃)×(0.9-0.8) / (45℃-35℃)=0.85, calculate the real-time current derating factor. = -(Ts-35℃)×( - (40℃-35℃) / (45℃-35℃)=0.85-(40℃-35℃)×(0.85-0.7) / (45℃-35℃)=0.775. The maximum permissible output voltage rating is... Multiply by the real-time voltage derating factor To obtain the permissible output voltage limit at the current temperature, the calculation method is: Permissible output voltage limit = ,For example =60V =0.85, the calculated allowable output voltage limit is 60V × 0.85 = 51V; at the same time, the maximum allowable output current rating is... Multiply by real-time current derating factor To obtain the permissible output current limit at the current temperature, the calculation method is: Permissible output current limit = ,For example =20A、 =0.775, the calculated allowable output current limit is 20A × 0.775 = 15.5A. Based on the allowable output voltage limit and allowable output current limit, the sampled value with real-time temperature is obtained. The changing functional relationship, with The x-axis represents the permissible output voltage limit, and the y-axis represents the permissible output current limit. Different values ​​are calculated point by point. The corresponding limit data is used to generate a temperature-permissible output derating curve, which clearly shows the impact of temperature changes on the charger's output capability. The main control module will then use the preset target test voltage. Target test current The calculated allowable output voltage limit and allowable output current limit are compared in real time. If... ≤ Permissible output voltage limit and ≤ Permissible output current limit This indicates that the charger under test can meet the target test requirements. At this point, the target test voltage can be used as the basis for further testing. With the target test current Multiply to calculate the target equivalent load power. The calculation method is as follows ,For example =45V =12A, calculated to =45V×12A=540W, providing a power basis for subsequent relay control and load regulation.

[0028] Furthermore, the step of simultaneously generating the initial relay group control sequence based on the pre-stored resistor group-power mapping relationship includes: Based on the maximum allowable output voltage With maximum allowable output current Calculate the instantaneous theoretical maximum output power of the charger under test. Based on target equivalent load power / Instantaneous theoretical maximum output power Calculated power request ratio ; Based on power request ratio The power request ratio is determined from the predefined mapping relationship between the safety margin coefficients corresponding to different power request ratio ranges within the main control module. Corresponding dynamic safety power margin coefficient ; Based on target equivalent load power And combined with dynamic safety power margin coefficient Generate an adjusted target power with a safety buffer. According to the target test voltage With the adjusted target power A reference value for the equivalent load resistance, taking into account safety margins, is generated by reverse calculation. Specifically ; Reference value of equivalent load resistance Match the resistor with the pre-stored resistor group-power mapping relationship, and select the resistance value that is closest to and not less than 1000 ohms. The available resistor rod branches or combinations of branches can be used to generate the corresponding initial relay control sequence.

[0029] In this embodiment of the invention, the main control module calculates the instantaneous theoretical maximum output power of the charger under test by multiplying the calculated allowable output voltage limit and allowable output current limit at the current temperature of the charger under test. The calculation method is as follows = Permissible output voltage limit × Permissible output current limit. For example, if the permissible output voltage limit is 51V and the permissible output current limit is 15.5A, the result is calculated as follows: =51V × 15.5A = 790.5W. The main control module calls the calculated target equivalent load power. The power request ratio is obtained by division. The calculation method is as follows ,For example =540W =790.5W, calculated as follows ≈0.68. The main control module internally predefines the mapping relationship between safety margin coefficients and different power request ratio ranges. The power request ratio ranges are divided into 0~0.5, 0.5~0.8, and 0.8~1.0, with corresponding dynamic safety power margin coefficients. The values ​​are 1.2, 1.1, and 1.05 respectively, based on the calculated power request ratio. Determine its corresponding interval, and then obtain the corresponding dynamic safety power margin coefficient. ,For example ≈0.68, falling within the 0.5~0.8 range, corresponding to =1.1. Based on target equivalent load power Combined with dynamic safety power margin coefficient The adjusted target power with a safety buffer is generated by multiplication. The calculation method is as follows ,For example =540W =1.1, calculated as follows =540W × 1.1 = 594W. The safety buffer prevents the load power from exceeding the charger's actual output capacity, ensuring test safety and conforming to the output capacity pattern presented by the temperature-permissible output derating curve. Based on the target test voltage... With the adjusted target power The equivalent load resistance reference value, taking into account safety margin, is generated by reverse calculation using the formula. The specific calculation formula is as follows: ,For example =45V =594W, calculated as follows = (45V) 2 / 594W=2025V 2 / 594W≈3.41Ω. The main control module pre-stores a resistor group-power mapping relationship. This mapping relationship includes the resistance value, single branch power, and total resistance and total power of 11 groups of resistor branches. The resistance value of each group of resistor branches is fixed, and the branches are combined in parallel. Different combinations correspond to different total resistance and total power. The resistance values ​​of the 11 groups of resistor branches are set to 1Ω, 2Ω, 4Ω, 8Ω, 16Ω, 32Ω, 64Ω, 128Ω, 256Ω, 512Ω, and 1024Ω, respectively. The power of a single branch is calculated based on the resistance value and the target test voltage, ensuring that the mapping relationship is consistent with the power calculation logic. The calculated equivalent load resistance reference value is then used. The resistors are matched one by one with the pre-stored resistor group-power mapping relationship to select the resistors with the closest resistance value and not less than 10 ... Available resistor rod branches or combinations of branches, for example The resistance is approximately 3.41Ω. A single-branch resistance of 4Ω is matched, which is the closest to the resistance of the branch. Then, the corresponding initial relay control sequence is generated. The control sequence includes the relay number (set as relay 3) and the activation command for the corresponding resistance branch. The control sequence explicitly controls relay 3 to activate and connect to the corresponding 4Ω resistance branch, while ensuring that other relays are in the off state. This provides a stable equivalent load for subsequent load testing and ensures that the deviation between the load power and the target value is controlled within a reasonable range during the test. This meets the core requirements of the system load test and forms a complete closed loop with the temperature derating calculation logic.

[0030] Furthermore, the step of generating the corresponding initial relay control sequence based on the pre-stored resistor group-power mapping relationship includes: The pre-stored resistor group-power mapping relationship is queried. The resistor group-power mapping relationship defines multiple independent resistor bar branches. Each resistor bar branch is composed of several resistor bars with corresponding resistance values ​​connected in series with a controlled relay, and the total resistance value of each branch is distributed according to binary weights or sequences. Based on the corresponding binary weights or sequence distribution matching, determine the resistance value that is closest to and not less than [the value]. The available resistor rod branches or combinations of branches are determined by solving the algorithm to identify the initial relay combination that needs to be activated, and a binary initial relay control sequence is generated.

[0031] In this embodiment of the invention, the main control module pre-stores a resistor group-power mapping relationship. This mapping relationship explicitly defines 11 independent resistor bar branches. Each resistor bar branch consists of several resistor bars with corresponding resistance values ​​connected in series with a controlled relay. Each branch's relay has a unique number, ranging from 1 to 11. The resistance values ​​of the resistor bars in each branch are fixed and distributed according to binary weights. Specifically, the resistance values ​​are set to 1Ω, 2Ω, 4Ω, 8Ω, 16Ω, 32Ω, 64Ω, 128Ω, 256Ω, 512Ω, and 1024Ω. The total resistance value of each branch corresponds one-to-one with the binary weights. Branch 1 corresponds to 2... 0 =1Ω, branch 2 corresponds to 2 1 =2Ω, branch 3 corresponds to 2 2 =4Ω, and so on, branch 11 corresponds to 2. 10 =1024Ω, the total power of each branch is determined based on the branch resistance and the target test voltage. The calculation method is: power of a single branch = target test voltage. 2 / Branch resistance values ​​are checked to ensure that the power of each branch matches the test requirements. The main control module initiates a query process, calling the internally cached resistor group-power mapping relationship, and reads the branch resistance value, relay number, and single branch power information for each branch. At the same time, it retrieves the calculated equivalent load resistance reference value considering safety margins. ,For example ≈3.41Ω, The resistance values ​​of all branches in the mapping relationship are matched one by one with the total resistance value of the combined branches. Based on the binary weight distribution pattern of each branch, a binary combination matching method is adopted, starting from the branch with the smallest resistance value, gradually combining branches, calculating the total resistance value after combination, and selecting the branch with the closest resistance value that is not less than the minimum resistance value. Available resistor rod branches or combinations of branches, for example ≈3.41Ω, among the single branches, the resistance of branch 3 is closest to 4Ω and not less than 3.41Ω. ≈5.41Ω, therefore, combining branch 2 (2Ω) and branch 3 (4Ω), the total resistance is 6Ω, which is closest to and not less than 5.41Ω. The initial relay combination that needs to be activated is determined by an algorithm. The algorithm process is as follows: Using the equivalent load resistance reference value... Convert to binary value, and determine whether the branch with the corresponding weight needs to be merged based on whether each bit of the binary value is 1. For example... ≈3.41Ω, which is approximately 11.011 in binary, corresponding to a weight of 2. 1 (2Ω) and 2 0 (1Ω), but the total resistance after combination is 3Ω, which is less than 3.41Ω, so it is matched upwards to weight 2. 2 (4Ω), corresponding to branch 3, determines that relay 3 will be activated; if ≈5.41Ω, which is approximately 101.011 in binary, corresponding to a weight of 2. 2 (4Ω) and 2 0 (1Ω), the total resistance after combination is 5Ω, which is less than 5.41Ω, and it is matched upwards to the weight 2. 2 (4Ω) and 2 1 (2Ω), the total resistance after combination is 6Ω, determining that relays 2 and 3 will be activated. Based on the determined relay combination to be activated, an initial binary relay control sequence is generated. The number of bits in the control sequence is consistent with the number of resistor branches, a total of 11 bits. Each bit corresponds to a relay in one branch. 1 indicates that the relay is activated, and 0 indicates that the relay is deactivated. For example, when only relay 3 is activated, the control sequence is 00000000100; when relays 2 and 3 are activated, the control sequence is 00000000110. The control sequence clearly defines the working state of each relay, providing clear instructions for subsequent load branch control.

[0032] Furthermore, the temperature monitoring signal and the maximum permissible output voltage rating are used as the basis for this. and maximum permissible output current rating Coupling generation temperature - allowable output derating curves include: During the initialization phase of the load test, the main control module extracts and stores the derating coefficients of voltage and current at the corresponding temperature and the derating sequence of the charger temperature inflection point at the corresponding voltage and current from the parsed charger parameter confirmation signal. After the load test is started, the main control module continuously reads the temperature monitoring signal from the thermistor and converts it into a real-time temperature sampling value reflecting the current temperature of the charger under test. The real-time temperature sampling value The derating factor is calculated by comparing the charger temperature inflection point derating sequence to obtain the value of each temperature inflection point. Corresponding voltage derating factor and current derating factor ; Based on each temperature inflection point value Corresponding voltage derating factor and current derating factor Piecewise linear interpolation is used based on real-time temperature sampling values. The temperature range in which it is located is calculated to obtain the corresponding current temperature. Real-time voltage derating factor and real-time current derating factor ; Maximum permissible output voltage rating Multiply by the real-time voltage derating factor Obtain the permissible output voltage limit at the current temperature, and simultaneously determine the maximum permissible output current rating. Multiply by real-time current derating factor The permissible output current limit at the current temperature is obtained, and the permissible output voltage limit and permissible output current limit are used to obtain the variable... The changing functional relationship generates the corresponding temperature-permissible output derating curve.

[0033] In this embodiment of the invention, during the initialization phase of the load test, the main control module receives and parses the charger parameter confirmation signal from the CAN communication transceiver module. From the parsed signal, it further extracts the derating coefficients of voltage and current at corresponding temperatures, as well as the charger temperature inflection point derating sequence at corresponding voltages and currents. The derating coefficients are set to 0.1 for every 10°C increase in voltage and 0.15 for every 10°C increase in current, ensuring that the derating range matches the actual output characteristics of the charger. The charger temperature inflection point derating sequence is set sequentially from low to high temperatures as 25°C, 35°C, 45°C, 55°C, 65°C, and 75°C, for a total of six temperature inflection point values. Value at each temperature inflection point Corresponding to a unique voltage derating factor and current derating factor The inflection point reduction rule strictly follows the extracted reduction magnitude coefficient, specifically set at 25℃. =1.0、 =1.0; at 35℃ =0.9、 =0.85; at 45℃ =0.8、 =0.7; at 55℃ =0.7、 =0.55; at 65℃ =0.6、 =0.4; at 75℃ =0.5、 =0.25, the extracted derating coefficient and the temperature inflection point derating sequence are stored together in the internal cache of the main control module, and a cache index is established for easy real-time retrieval later. After starting the load test, the main control module continuously reads the temperature monitoring signal from the thermistor. The reading frequency is consistent with the temperature sensor acquisition period, both being 500 milliseconds. The received temperature monitoring signal is processed by digital-to-analog conversion to convert it into a real-time temperature sampling value reflecting the current temperature of the charger under test. The conversion process is achieved through an internal digital-to-analog converter circuit, which converts the analog temperature signal into a decimal digital signal, such as obtaining a real-time temperature sampling value after conversion. =48℃. The main control module calls the cached charger temperature inflection point derating sequence and uses the real-time temperature sample value. With each temperature inflection point value Perform a one-by-one comparison and calculate the value of each temperature inflection point. Corresponding voltage derating factor and current derating factor The calculation process compares the calculation results with the pre-stored inflection point derating rules, verifying the derating coefficient for each inflection point one by one to ensure that the calculation results are completely consistent with the pre-stored rules and there are no deviations. For example, when calculating the derating coefficient for 35℃... =0.9、 =0.85, corresponding to 45℃ =0.8、 =0.7, corresponding to 55℃ =0.7、 =0.55. Based on each temperature inflection point value. Corresponding voltage derating factor and current derating factor A piecewise linear interpolation method is used to first determine the real-time temperature sampling value. The temperature range in which it is located =48℃ falls between the two inflection points of 45℃ and 55℃. Based on the derating coefficients at both ends of this interval, the corresponding temperature can be calculated using a linear interpolation formula. Real-time voltage derating factor and real-time current derating factor The calculation method is as follows = -( -45℃) × ( - (55℃-45℃) = 0.8 - (48℃-45℃) × (0.8-0.7) / (55℃-45℃) = 0.77 = -(Ts-45℃)×( - (55℃-45℃) = 0.7 - (48℃-45℃) × (0.7-0.55) / (55℃-45℃) = 0.655. Retrieve the maximum permissible output voltage rating obtained from the decoder. and maximum permissible output current rating ,For example =60V =20A, will Multiply by the real-time voltage derating factor To obtain the permissible output voltage limit at the current temperature, the calculation method is: Permissible output voltage limit = × =60V × 0.77 = 46.2V; at the same time, Multiply by real-time current derating factor To obtain the permissible output current limit at the current temperature, the calculation method is: Permissible output current limit = × =20A × 0.655 = 13.1A. Based on the allowable output voltage limit and allowable output current limit, obtain the sampled value with real-time temperature. The changing functional relationship, selecting all values ​​in the temperature inflection point sequence. And several intermediate temperature values, calculate the allowable output voltage limit and allowable output current limit corresponding to each temperature point by point. For example, 25℃ corresponds to 50V and 17A, 35℃ corresponds to 54V and 17A, 45℃ corresponds to 48V and 14A, 55℃ corresponds to 42V and 11A, 65℃ corresponds to 36V and 8A, and 75℃ corresponds to 30V and 5A. Using the x-axis as the horizontal axis and the allowable output voltage limit and allowable output current limit as the vertical axis, all the calculated coordinate points are connected sequentially to generate the corresponding temperature-allowable output derating curve. The curve clearly shows the law that the allowable output voltage and current of the charger gradually decrease as the temperature rises, providing a temperature correlation basis for subsequent load power adjustment.

[0034] Furthermore, the step of dynamically adjusting the duty cycle of the first pulse width modulation signal based on the voltage deviation value to generate a second pulse width modulation signal for closed-loop regulation of the adjustable DC analog voltage includes: For voltage deviation value Performing a first-order difference operation yields the deviation change rate, which characterizes the trend of voltage deviation variation. ; Obtain reference points at different duty cycles The output current state of the charger under test And based on different duty cycle reference points The output current state of the charger under test Determine the reference points at different duty cycles Below, the change in unit duty cycle The resulting steady-state output voltage change And based on the current duty cycle and The sign of the variable determines the dynamic gain coefficient corresponding to the current charger under test. ; voltage deviation value Input an adaptive state observer, which uses... and The input is used to estimate the equivalent disturbance voltage caused by the coupling between internal noise of the voltage simulation module and load step disturbance. ;according to Calculate the duty cycle compensation amount, where The disturbance compensation coefficient is used, and the duty cycle of the first pulse width modulation signal is dynamically adjusted based on the duty cycle compensation amount to generate the second pulse width modulation signal for closed-loop regulation of the adjustable DC analog voltage.

[0035] In this embodiment of the invention, the main control module first obtains the actual output value of the adjustable DC analog voltage and the preset target value, and then subtracts the two to obtain the voltage deviation value. For example, if the preset target value is 45V and the actual output value is 44.2V, the calculated value is... =45V - 44.2V = 0.8V. (Regarding the voltage deviation value) First-order difference calculation is performed, which is implemented through the internal calculation circuit of the main control module. The voltage deviation values ​​of two adjacent sampling periods are selected for difference calculation to obtain the deviation change rate, which characterizes the trend of voltage deviation change. The sampling period is set to 100 milliseconds, for example, the previous sampling period. =0.8V, current sampling period =0.9V, calculated as follows =0.9V - 0.8V = 0.1V / 100ms = 1V / s. The main control module internally stores reference points for different duty cycles. Specifically, four reference points are set: 20%, 40%, 60%, and 80%, with each duty cycle reference point corresponding to a preset output current state. , It is divided into three levels: low current state (≤5A), medium current state (5A~15A), and high current state (>15A). The current detection circuit inside the main control module obtains the current of the charger under test at different duty cycle reference points. The corresponding output current state Based on different duty cycle reference points Output current state under the following conditions Through multiple tests and calibrations, the change in unit duty cycle at each duty cycle reference point was determined. The steady-state output voltage change caused by D (set to 1%) ,For example =40% When in medium current condition (10A), =0.2V / 1%; =60% In the high current state (16A), =0.3V / 1%. Based on the current duty cycle. and the rate of change of deviation The sign of the dynamic gain coefficient determines the dynamic gain coefficient. ,like It is positive (the voltage deviation shows an increasing trend). Take the corresponding 1.1 times; if It is negative (the voltage deviation shows a decreasing trend). Take the corresponding 0.9 times, for example, the current =40% In medium current state, If positive, the calculation yields =0.2V / 1% × 1.1 = 0.22V / 1%. The voltage deviation value... The input is an adaptive state observer, which is integrated within the main control module, based on the rate of change of deviation. and dynamic gain coefficient As input, the equivalent disturbance voltage caused by the coupling between internal noise in the voltage simulation module and load step disturbance is estimated using an internal algorithm. The estimation process combines historical disturbance data with real-time input parameters, for example, the estimated... =0.12V. Set the disturbance compensation coefficient. =0.8, according to the formula Calculate the duty cycle compensation amount, substitute the values ​​to obtain the result. = (0.8V) 0.8×0.12V) / 0.22V / 1%≈(0.8V (0.096V) / 0.22V / 1%≈3.2%. This is based on the calculated duty cycle compensation. The duty cycle of the first pulse width modulation signal is dynamically adjusted. If the current duty cycle of the first pulse width modulation signal is 40%, the adjusted duty cycle is 40% + 3.2% = 43.2%. A second pulse width modulation signal is generated and transmitted to the voltage simulation module. The module controls the on and off times of the power devices inside, and the adjustable DC analog voltage is adjusted in a closed loop to make the actual output voltage gradually approach the preset target value, ensuring stable voltage output.

[0036] Furthermore, the step of dynamically adjusting the initial relay group control sequence to generate load regulation commands based on the magnitude and direction of the real-time power deviation value includes: The adjustment direction corresponding to the current relay group control is determined based on the direction of the real-time power deviation value. Based on the magnitude of the real-time power deviation and combined with the target test voltage Determine the optimal resistance change required to achieve real-time power deviation adjustment. ; Based on the adjustment direction and the amount of change in optimal resistance. And combined with the total equivalent resistance corresponding to the control sequence of the currently engaged relay group. Calculate the target total equivalent resistance. ,in This is the current power value; The main control module iterates through all possible relay combination states, calculates the theoretical equivalent resistance value corresponding to each combination, and selects the combination that satisfies the minimum |theoretical equivalent resistance value - target total equivalent resistance value| as the target relay group control sequence; The target relay group control sequence is compared with the current initial relay group control sequence to generate a load regulation command that only contains state change bits, specifically from 0 to 1 or from 1 to 0. Based on the load adjustment command, the magnitude and direction of the real-time power deviation are determined. If the real-time power deviation is positive and exceeds the first threshold, the current load is determined to be insufficient. The main control module selects one or more branches from the currently non-engaged relays that can make the total power closest to the target power after being connected, generates a relay activation command, and updates the relay group control sequence. If the real-time power deviation is negative and exceeds the second threshold, the current load is determined to be overloaded. The main control module selects one or more branches from the currently engaged relays that have the least impact on the total power after being disconnected, generates a relay disconnect command, and updates the relay group control sequence. The above steps are repeated cyclically to control the power load module to increase or decrease the number of connected resistor groups, so as to complete the automatic closed-loop load test of the charger under test.

[0037] In this embodiment of the invention, the main control module receives the actual voltage and current sample values ​​transmitted by the sampling feedback module in real time, and calculates the current power value of the charger under test by multiplication. Actual power = Actual voltage sample value × Actual current sample value. If the actual voltage sample value is 44.2V and the actual current sample value is 11.8A, the calculated value is... =44.2V × 11.8A ≈ 521.56W. (This refers to the current power value.) Compared with the previously calculated target equivalent load power Subtracting (540W) yields the real-time power deviation value. The calculation method is as follows Substituting the numerical values, we get =540W 521.56W = 18.44W. Based on real-time power deviation value. The direction determines the adjustment direction, if A positive value indicates that the current actual power is less than the target power, and the adjustment direction is to increase the load, i.e., to activate the relay and connect more resistor branches; if... A negative value indicates that the actual power is greater than the target power. The adjustment direction is to reduce the load, i.e., disconnect the relay and disconnect part of the resistor branch. =18.44W is positive; the adjustment direction is to increase the load. Based on real-time power deviation value. The size and combined with the set target test voltage (45V), the optimal resistance change required to achieve real-time power deviation adjustment is determined by formula calculation. The calculation method is as follows Substitute the values ​​and calculate step by step: First calculate =45V×45V=2025V 2 , =540W 18.44W = 521.56W, then calculate. =2025V 2 / 540W=3.75Ω, =2025V 2 / 521.56W≈3.91Ω, finally obtained =3.75Ω 3.91Ω= 0.16Ω, the negative sign indicates that the equivalent resistance needs to be reduced to increase the load. Obtain the total equivalent resistance corresponding to the currently engaged relay group control sequence. For example, the current relay number 3 (4Ω) is engaged. =4Ω, depending on the adjustment direction and the amount of resistance change at the optimal value. Combine with the correct formula = (45V) 2 / (521.56W) (45V) 2 / (4Ω) 2 )×( 0.16Ω) Recalculate the target total equivalent resistance. Substitute the values ​​and calculate step by step: First calculate (45V). 2 =2025V 2 (4Ω) 2 =16Ω2, (45V)2 / (4Ω) 2 =2025V 2 / 16Ω 2 ≈126.5625V 2 / Ω 2 Then calculate the value and ( The product of 0.16Ω is 126.5625V. 2 / Ω 2 ×( 0.16Ω)≈ 20.25V 2 / Ω, then calculated 521.56W. ( 20.25V 2 / Ω) = 521.56W + 20.25W = 541.81W (because V 2 / Ω is equivalent to W (the unit is equivalent to W), and finally calculate =2025V 2 / 541.81W≈3.74Ω, this calculation result is the correct target total equivalent resistance, and 3.74Ω is less than the current value. =4Ω, which conforms to the adjustment direction of "reducing resistance and increasing load", requiring no additional correction. The main control module traverses all possible relay combination states of the 11 groups of resistance rod branches, totaling 2048 combinations. Through its internal calculation circuit, it calculates the theoretical equivalent resistance value corresponding to each combination (the total resistance value of parallel branches is calculated as 1 / Rtotal = 1 / R1 + 1 / R2 + ... + 1 / Rn), calculating the theoretical equivalent resistance value and the target total equivalent resistance value for each combination one by one. The absolute value of the difference is approximately 3.74Ω. The combination with the smallest absolute value of the difference is selected as the control sequence for the target relay group. For example... ≈3.74Ω. After comprehensive calculation, the combined resistance of relay 3 (4Ω) and relay 1 (1Ω) is calculated as 1 / Rtotal = 1 / 4Ω + 1 / 1Ω = 0.25Ω. -1 +1Ω -1 =1.25Ω -1 Rtotal = 0.8Ω, and the absolute value of the difference is |0.8Ω. 3.74Ω|=2.94Ω; When relays #3 (4Ω) and #2 (2Ω) are engaged, the total resistance after combination is calculated as 1 / Rtotal = 1 / 4Ω + 1 / 2Ω = 0.25Ω. -1 +0.5Ω -1 =0.75Ω -1 Rtotal ≈ 1.33Ω, and the absolute value of the difference is |1.33Ω. 3.74Ω|=2.41Ω; When relays #3 (4Ω) and #7 (64Ω) are activated, the total resistance after combination is calculated as 1 / Rtotal = 1 / 4Ω + 1 / 64Ω = 0.25Ω. -1 +0.015625Ω -1 =0.265625Ω -1 Rtotal ≈ 3.76Ω, and the absolute value of the difference is |3.76Ω. 3.74Ω|=0.02Ω; When relays #3 (4Ω) and #8 (128Ω) are activated, the total resistance after combination is calculated as 1 / Rtotal = 1 / 4Ω + 1 / 128Ω = 0.25Ω. -1 +0.0078125Ω -1 =0.2578125Ω -1 Rtotal ≈ 3.88Ω, and the absolute value of the difference is |3.88Ω. 3.74Ω|=0.14Ω; When relays #3 (4Ω) and #6 (32Ω) are activated, the total resistance after combination is calculated as 1 / Rtotal = 1 / 4Ω + 1 / 32Ω = 0.25Ω. -1 +0.03125Ω -1 =0.28125Ω -1 Rtotal ≈ 3.55Ω, and the absolute value of the difference is |3.55Ω. 3.74Ω|=0.19Ω. Comparing the absolute values ​​of the differences among all combinations, the combination of engaging relay 3 (4Ω) and relay 7 (64Ω) has the smallest absolute value of difference, at only 0.02Ω, perfectly matching the target total equivalent resistance. The required resistance is approximately 3.74Ω, and the equivalent resistance after connection is 3.76Ω, which is less than the current resistance. =4Ω, which aligns with the adjustment direction of "reducing resistance and increasing load," therefore this combination is determined as the target relay group control sequence. Comparing the target relay group control sequence with the current initial relay group control sequence (only relay 3 is activated, sequence 00000000100), a discrepancy is found; relay 7 is not currently activated. The main control module immediately generates a relay 7 activation command, which is transmitted to the relay 7 coil via the GPIO pin. The coil is energized, generating electromagnetic attraction, closing the control contacts, and connecting the 64Ω resistor array corresponding to relay 7 to the load circuit, updating the relay group control sequence to 01000000100. After the command is executed, the main control module waits 500 milliseconds, then receives the new actual voltage and current sample values ​​from the sampling feedback module, recalculating the current power value. Real-time power deviation value If the new real-time power deviation value is still positive and exceeds the first threshold (set to 10W), the above calculation, filtering, and instruction generation process is repeated to continue increasing the load. If the new real-time power deviation value is negative and exceeds the second threshold (set to 10W), the current load is determined to be overloaded. The main control module selects the branch that will have the least impact on the total power after being disconnected from the currently engaged relays, i.e., disconnecting relay number 7 with the largest resistance, generating a relay disconnection command, and updating the relay group control sequence. The above steps are executed cyclically, collecting the real-time power value every 500 milliseconds, and sequentially completing deviation calculation, adjustment direction determination, target resistance value calculation, combination filtering, instruction generation, and sequence update. The power load module is controlled to increase or decrease the connected resistor groups until the real-time power deviation value is between the first and second thresholds, thus completing the automatic closed-loop load test of the charger under test.

[0038] Furthermore, such as Figure 7 As shown, the sampling feedback module includes a voltage sampling submodule, a voltage tracking submodule, and a current sampling submodule. The actual voltage sampling value and actual current sampling value of the real-time power load acquisition module include: The voltage sampling submodule extracts a small-amplitude voltage signal from the high voltage by connecting a resistor divider network consisting of corresponding sampling resistors between the positive and negative terminals of the AC power supply, which serves as the original voltage sampling signal. The original voltage sampling signal is then connected to the inverting and non-inverting inputs of the corresponding operational amplifier for isolation and amplification, generating a voltage analog signal that is linearly proportional to the AC power supply. After passing through anti-aliasing filtering, the voltage analog signal is sent to the first analog-to-digital converter channel of the main control module to be converted into a real-time digital voltage sampling value. The voltage tracking submodule is used to bias the system power-on and the real-time voltage sampling value corresponding to the subsequent conversion of the voltage to low impedance DC in the voltage conversion module. The current sampling submodule has a shunt resistor connected in series in the negative AC circuit and uses a current sampling chip to detect the voltage drop signal across the shunt resistor. At the same time, the voltage drop signal is amplified into a proportional voltage signal to generate a current analog signal. After the current analog signal is filtered by anti-aliasing, it is sent to the second analog-to-digital converter channel of the main control module and converted into a real-time digital current sampling value.

[0039] In this embodiment of the invention, the core of the U2-B voltage sampling submodule consists of voltage divider resistors, current limiting resistors, a balanced discharge resistor, a bypass capacitor, a bias resistor, a feedback network, and filtering and current limiting components. For the high-voltage DC signal connected to the power load module, a resistor divider network composed of R73, R74, R76, and R77 is connected between the positive and negative terminals of the resistive load, according to the circuit connection shown in the diagram. All four resistors use fixed-value resistors. Utilizing the principle of resistor voltage division, the high-voltage DC current at the positive and negative terminals of the resistive load is proportionally reduced, resulting in two differential signals, which are then fed into the U2-B operational amplifier. The inverting and non-inverting inputs are used to prepare for subsequent differential amplification. The voltage division ratio is determined based on the resistance ratio of the four components. For example, if R73=R74=100kΩ and R76=R77=1kΩ, the voltage division ratio is 1kΩ / (100kΩ+1kΩ). If the actual amplitude of the high voltage DC current at the positive and negative poles of the resistive load is 45V, the calculated amplitude of the two differential signals after voltage division is 45V×(1 / 101)≈0.446V. This amplitude is within the input range of the U2-B op-amp, avoiding signal overload and damage to the device. It is completely consistent with the output amplitude range and signal flow of the voltage divider network shown in the figure. According to the wiring diagram, R75 and R78 are current-limiting resistors, connected in series between the two differential signals and the inverting and non-inverting inputs of the U2-B op-amp, respectively. This limits the op-amp's input current, preventing high-voltage signals from damaging the U2-B op-amp and ensuring its safe operation. Both R75 and R78 are set to 10kΩ to limit the input current to a safe range, preventing excessive current from damaging internal components. R79 serves as a balancing and bleedering resistor. One end connects to the connection point between the inverting input of the U2-B op-amp and R75, and the other end connects to the connection point between the non-inverting input of the U2-B op-amp and R78. This balances the impedance of the upper and lower voltage divider arms, ensuring the two differential signals output by the voltage divider network are symmetrical and stable. It also provides a bleedering circuit for the voltage divider nodes, promptly dissipating residual charge generated during the voltage division process to prevent charge accumulation from affecting the voltage division accuracy. R79 is set to 100kΩ to match the voltage divider resistors, ensuring impedance balance. C16 serves as a bypass capacitor for the inverting input, with one end connected to the inverting input of the U2-B op-amp and the other end grounded. C18 serves as a bypass capacitor for the non-inverting input, with one end connected to the non-inverting input of the U2-B op-amp and the other end grounded. Both are 10nF capacitors, further filtering out high-frequency interference in the differential signal, smoothing the input signal, and preventing high-frequency noise from entering the op-amp and affecting the amplification effect. This is consistent with the installation position and function of the bypass capacitors shown in the diagram. R81 is connected to a 3.3V power supply on one end and to the non-inverting input of the U2-B op-amp on the other end, providing DC bias to the non-inverting input. This ensures that the AC signal is fully amplified within the linear region of the U2-B op-amp, avoiding signal distortion due to insufficient bias. The resistance of R81 is set to 10kΩ to provide a stable bias current and ensure the linear amplification performance of the op-amp.R80 and C17 form a feedback network. One end of R80 is connected to the output of the U2-B operational amplifier, and the other end is connected to the inverting input. C17 is connected in parallel across R80. Together, they form an active low-pass filter and a proportional amplifier circuit, which can further filter out high-frequency interference in the signal and proportionally amplify the differential signal. The amplification factor is determined by the resistance ratio of R80 and R75. Setting R80 = 100kΩ, the amplification factor = 100kΩ / 10kΩ = 10 times. After amplification, a voltage analog signal is generated that is linearly proportional to the high-voltage DC. For example, if the amplitude of the differential signal after voltage division is 0.446V, the amplitude of the amplified voltage analog signal = 0.446V × 10 = 4.46V. This signal maintains a linear correspondence with the amplitude of the high-voltage DC, ensuring the accuracy of signal transmission. R82 and C19 are connected in series between the output of the U2-B op-amp and the first analog-to-digital converter channel of the main control module. R82 acts as a current-limiting resistor to limit the current entering the analog-to-digital converter, and C19 acts as a filter capacitor to filter out residual high-frequency noise in the voltage analog signal. The two work together to ensure the accuracy of ADC sampling. The resistance of R82 is set to 1kΩ and the capacitance of C19 is set to 10nF, which perfectly matches the specifications of the filter current-limiting circuit in the figure. The filtered analog voltage signal is sent to the first analog-to-digital converter (ADC) channel of the main control module according to the signal transmission path shown in the diagram. The ADC uses a 12-bit resolution and the conversion range is set to 0~3.3V. It converts the analog voltage signal into a real-time digital voltage sample value. The conversion process is realized through the sample-and-hold circuit and quantization circuit inside the ADC. The sample-and-hold circuit holds the input analog signal stably for a period of time to ensure that the quantization circuit can accurately quantize the signal. The quantization circuit converts the amplitude of the analog signal into the corresponding digital quantity. The conversion formula is: real-time voltage sample value (digital quantity) = (analog voltage signal amplitude / 3.3V) × 4095. For example, if the amplitude of the analog voltage signal is 4.46V, after processing by R82 and C19, it is stabilized within 3.3V. Taking the stable value of 3.0V, the real-time voltage sample value (digital quantity) is calculated as (3.0 / 3.3) × 4095 ≈ 3723. This digital quantity can be directly read by the main control module and used for subsequent power calculation and load adjustment, which is consistent with the signal flow of the ADC channel shown in the diagram.

[0040] U2-A is a voltage follower submodule. Its core function is to generate a stable 1.65V DC reference voltage as the midpoint bias of the sampling circuit. This provides a low-impedance, high-stability bias for the subsequent sampling operational amplifier, preventing load fluctuations from affecting the reference accuracy. The module internally contains the U2-A operational amplifier and external components. Following the wiring logic shown in the diagram, R83 acts as a current-limiting resistor, with one end connected to the 3.3V power supply and the other end connected to the non-inverting input of the U2-A operational amplifier, limiting the input current to prevent damage from excessive current. The resistance value of R83 is set to 1kΩ. R84 acts as a feedback / bias resistor, with one end connected to the output of the U2-A operational amplifier and the other end connected to the inverting input, while also being grounded. This ensures that the U2-A operational amplifier operates in the linear region and provides a stable DC bias, ensuring stable output. The resistance value of R84 is set to 10kΩ to match the operational amplifier parameters and guarantee the bias effect. C20 and C21 are used as filter capacitors. One end of C20 is connected to the non-inverting input of the U2-A op-amp, and the other end is grounded. One end of C21 is connected to the connection node between R83 and the non-inverting input of the U2-A op-amp, and the other end is grounded. Both are 100nF capacitors used to stabilize the input potential and filter out high-frequency noise in the input signal, ensuring the stability of the input signal of the U2-A op-amp. C22 and C23 are also used as filter capacitors. One end of C22 is connected to the 5V power input interface, and the other end is grounded. One end of C23 is connected to the output terminal of the U2-A op-amp, and the other end is grounded. They are used to filter out noise in the 5V power input and the 1.65V reference output voltage, ensuring the stability of the 5V power supply and the high stability of the 1.65V reference voltage. Both C22 and C23 are 100nF capacitors, which perfectly match the installation position and function of the filter capacitors in the diagram. The 1.65V DC reference voltage output by the U2-A op-amp is directly connected to the bias interface of the subsequent sampling op-amp to achieve stable bias.

[0041] The core of the current sampling submodule consists of a current-limiting protection resistor, interference suppression components, a filter capacitor, a milliohm-level sampling resistor, and a clamping diode. It is connected in series in the current loop of the power load module. According to the circuit layout shown, R85 and R90 serve as current-limiting protection resistors, connected in series at the input and output terminals of the current sampling module, respectively, limiting the current in the entire current sampling loop and preventing excessive current from damaging the components within the module. The resistance values ​​of R85 and R90 are both set to 100Ω, effectively limiting the loop current within a safe range. L2 is connected in series between R85 ​​and the subsequent sampling resistor to suppress high-frequency interference in the current signal, preventing interference signals from affecting sampling accuracy. L2 uses a small surface-mount inductor, matching the mounting position and function of the interference suppression components shown in the diagram. C24 and C25 form a combined large and small capacitor filter circuit. C24 is a 100nF capacitor, and C25 is a 10μF capacitor. They are connected in parallel between the input terminal of the current sampling module and ground. Through the cooperation of the large and small capacitors, high-frequency noise and low-frequency ripple in the current signal are filtered out, ensuring the purity of the current signal, consistent with the specifications and connection method of the filter circuit in the figure. R86, R87, R88, and R89 are milliohm-level current sampling resistors. The four are connected in parallel in the current loop, with a total resistance of 10mΩ. The milliohm-level resistance ensures that the power consumption of the sampling resistor itself is extremely low and will not affect the normal operation of the current loop. At the same time, it can generate a small voltage drop signal proportional to the loop current. According to Ohm's law, the amplitude of the voltage drop signal across the sampling resistor = the amplitude of the loop current × 10mΩ. For example, if the amplitude of the loop current is 10A, the calculated amplitude of the voltage drop signal across the sampling resistor is 10A × 0.01Ω = 0.1V. This small voltage drop signal can accurately reflect the magnitude of the loop current. D16 acts as a clamping diode, with one end connected to the connection node between the sampling resistor output and the second analog-to-digital converter channel (MCU ADC-I) of the main control module, and the other end connected to a 3.3V power supply. Assuming the diode voltage drop is 0.7V, its core function is to protect the MCU ADC-I from damage by high voltage. When the voltage signal output by the sampling resistor is greater than 4V, D16 conducts in reverse, discharging the excess voltage through the 3.3V power supply and preventing high voltage signals from entering the MCU. Only when the voltage signal output by the sampling resistor is less than 4V, D16 is cut off, allowing the voltage signal to enter the MCU ADC-I, ensuring the safety of the ADC sampling interface.The voltage drop signal output from the sampling resistor is filtered by L2 for interference suppression and C24 and C25, and then sent to the second analog-to-digital converter channel of the main control module. This analog-to-digital converter has the same specifications as the first one, with 12-bit resolution and a conversion range of 0~3.3V. It converts the voltage drop signal into a real-time digital current sample value. The conversion formula is the same as the voltage sampling conversion formula, that is, real-time current sample value (digital quantity) = (voltage drop signal amplitude / 3.3V) × 4095. For example, if the voltage drop signal amplitude is 0.1V, the calculated real-time current sample value (digital quantity) is (0.1 / 3.3) × 4095 ≈ 124. After being read by the main control module, this digital quantity is used in conjunction with the real-time voltage sample value to calculate the actual power of the power load module. This provides core data support for subsequent load adjustment and closed-loop control of the test, ensuring that the entire test and control system can accurately obtain the working status of the power load module and completely match the signal output logic of the current sampling submodule in the diagram.

[0042] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A resistive load charger test control system with CAN-BMS emulation, characterized by, Includes the following modules: The system power-on and voltage conversion module is used to connect to AC power and press the start button to convert high-voltage AC power into low-voltage DC power. Based on the low-voltage DC power, after the entire system is in a ready state, pressing the load button controls the relay to activate and execute the load test corresponding to the charger under test with CAN communication. The main control module is electrically connected to the system power-on and voltage conversion module. It is used to receive and store the target test voltage and target test current input by the key, and generate a first pulse width modulation signal based on the target test voltage. The CAN communication transceiver module is electrically connected to the main control module. It is used to receive the target test voltage and target test current from the main control module, generate BMS analog communication data packets based on the preset BMS battery management protocol, and actively send them to the charger under test through the internal CAN transceiver circuit. At the same time, it receives the charger parameter confirmation signal returned by the charger under test. The voltage simulation module is electrically connected to the main control module and the CAN communication transceiver module. It is used to receive the first pulse width modulation signal and the charger parameter confirmation signal, and drive the internal DC-DC power module based on the charger parameter confirmation signal to output an adjustable DC analog voltage corresponding to the target test voltage according to the first pulse width modulation signal, so as to ensure that the charger under test detects the presence of voltage at the output terminal BAT+ and starts. A power load module, comprising multiple parallel resistor arrays and a relay array for controlling the connection or disconnection of the resistor arrays, wherein the relay array is connected to the main control module; A sampling feedback module is connected between the output of the voltage simulation module and the input of the power load module. It is used to collect the actual voltage and current sampling values ​​of the power load module in real time and send them to the main control module. The main control module is further configured to receive the charger parameter confirmation signal and parse it to obtain the maximum allowable output voltage and maximum allowable output current of the charger under test, and calculate the target equivalent load power by combining the target test voltage and target test current. At the same time, it generates an initial relay group control sequence based on the pre-stored resistor group-power mapping relationship, and controls the relays of the corresponding group in the power load module to activate and output the actual voltage sample value and the actual current sample value. The actual voltage sample value is compared with the target test voltage to generate a voltage deviation value, and the duty cycle of the first pulse width modulation signal is dynamically adjusted according to the voltage deviation value to generate a second pulse width modulation signal to adjust the adjustable DC analog voltage in a closed loop. The main control module also compares the collected actual voltage and current sampling values ​​with the target test voltage and target test current to calculate the real-time power deviation value. Based on the magnitude and direction of the real-time power deviation value, it dynamically adjusts the initial relay group control sequence to generate load adjustment commands, and controls the power load module to increase or decrease the connected resistor groups in order to complete the automatic closed-loop load test of the charger under test.

2. The resistive load charger test control system with CAN-BMS emulation of claim 1, wherein, The system power-on and voltage conversion module also includes a temperature control switch, an emergency stop button, and a freewheeling diode; the temperature control switch is connected in series with the load button, the emergency stop button is connected in series with the temperature control switch and then grounded, and the freewheeling diode is connected in parallel across the relay to dissipate the voltage spikes after the relay is disconnected. The continuous operation after being connected to AC power specifically refers to: After AC power is connected, the main control module continuously monitors the status of the start button. When the start button is detected to be pressed, a system power-on enable signal is generated, which controls the relay to engage to supply power to the main circuit of the system and start the cooling fan. Temperature sensors are arranged at the heat dissipation points of the power load module to collect the temperature data of the resistance rod array in real time and generate a temperature monitoring signal. The temperature monitoring signal is compared with the preset first temperature warning threshold and the second temperature protection threshold; If the temperature monitoring signal exceeds the first temperature warning threshold, the main control module generates a derating control command. This command is used to reduce the calculated value of the target equivalent load power, triggering the power load module to reduce the number of connected resistor branches. If derating is not possible due to extreme testing, the cooling fan speed is increased. If the temperature monitoring signal reaches the second temperature protection threshold, the temperature control switch automatically disconnects, forcibly cutting off the power supply circuit to the relay coil, causing the relay to disconnect. When the temperature drops to the second temperature protection threshold of -15°C, the temperature control switch automatically closes and reconnects the relay. Alternatively, in an emergency, pressing the emergency stop button disconnects the circuit relay.

3. The resistive load charger test control system with CAN-BMS emulation of claim 1, wherein, The CAN communication transceiver module includes the following functions: The target test voltage and target test current received from the main control module are encapsulated into parameter request frame data based on the preset BMS battery management protocol; Generate protocol version query frame data by querying a pre-stored library of multiple charger protocol identifiers; The protocol version query frame data and parameter request frame data are combined according to a preset communication sequence to generate BMS simulated communication data packets; The BMS analog communication data packets are actively broadcast to the charger under test via the transmit pin of the corresponding CAN transceiver circuit, and the charger under test will respond with a charger parameter confirmation signal containing its protocol version and maximum output capability.

4. The resistive load charger test control system with CAN-BMS simulation according to any one of claims 2 or 3, characterized in that, The analysis obtains the maximum allowable output voltage and maximum allowable output current of the charger under test, and calculates the target equivalent load power by combining the target test voltage and target test current, including: The main control module receives a charger parameter confirmation signal from the CAN communication transceiver module and extracts the parameter code representing the maximum output capability from the charger parameter confirmation signal. The parameter code is in an encrypted or compressed format. According to a preset decoding mapping table corresponding to the protocol version of the charger under test, the parameter code is decoded to restore the maximum permissible output voltage rating of the charger under test under standard conditions. and maximum permissible output current rating ; Based on temperature monitoring signal and maximum permissible output voltage rating and maximum permissible output current rating The temperature-permissible output derating curve is generated by coupling, and the permissible output derating factor corresponding to the current temperature is obtained based on the temperature-permissible output derating curve; Based on the allowable output derating factor and combined with the maximum allowable output voltage rating and maximum permissible output current rating The maximum permissible output voltage of the tested charger at the current temperature was calculated. With maximum allowable output current ; Target test voltage Target test current The maximum permissible output voltage actually available for the charger under test. With maximum allowable output current When comparing, ≤ and ≤ Then, based on the target test voltage With the target test current Multiplication to calculate target equivalent load power .

5. The resistive load charger test and control system with CAN-BMS simulation according to claim 4, characterized in that, The process of simultaneously generating the initial relay group control sequence based on the pre-stored resistor group-power mapping relationship includes: Based on the maximum allowable output voltage With maximum allowable output current Calculate the instantaneous theoretical maximum output power of the charger under test. Based on target equivalent load power / Instantaneous theoretical maximum output power Calculated power request ratio ; Based on power request ratio The power request ratio is determined from the predefined mapping relationship between the safety margin coefficients corresponding to different power request ratio ranges within the main control module. Corresponding dynamic safety power margin coefficient ; Based on target equivalent load power And combined with dynamic safety power margin coefficient Generate an adjusted target power with a safety buffer. According to the target test voltage With the adjusted target power A reference value for the equivalent load resistance, taking into account safety margins, is generated by reverse calculation. Specifically ; Reference value of equivalent load resistance Match the resistor with the pre-stored resistor group-power mapping relationship, and select the resistance value that is closest to and not less than 1000 ohms. The available resistor rod branches or combinations of branches can be used to generate the corresponding initial relay control sequence.

6. The resistive load charger test and control system with CAN-BMS simulation according to claim 5, characterized in that, The process of generating the corresponding initial relay control sequence based on the pre-stored resistor group-power mapping relationship includes: The pre-stored resistor group-power mapping relationship is queried. The resistor group-power mapping relationship defines multiple independent resistor bar branches. Each resistor bar branch is composed of several resistor bars with corresponding resistance values ​​connected in series with a controlled relay, and the total resistance value of each branch is distributed according to binary weights or sequences. Based on the corresponding binary weight or sequence distribution matching determines the resistance closest to and not less than The available resistance rod branch or branch combination, and through algorithm solving determines the initial relay combination that needs to be attracted, generates the binary initial relay control sequence.

7. The resistive load charger test and control system with CAN-BMS simulation according to claim 4, characterized in that, The temperature monitoring signal and the maximum allowable output voltage rating are used as the basis. and maximum permissible output current rating Coupling generation temperature - allowable output derating curves include: During the initialization phase of the load test, the main control module extracts and stores the derating coefficients of voltage and current at the corresponding temperature and the derating sequence of the charger temperature inflection point at the corresponding voltage and current from the parsed charger parameter confirmation signal. After the load test is started, the main control module continuously reads the temperature monitoring signal from the thermistor and converts it into a real-time temperature sampling value reflecting the current temperature of the charger under test. The real-time temperature sampling value The derating factor is calculated by comparing the charger temperature inflection point derating sequence to obtain the value of each temperature inflection point. Corresponding voltage derating factor and current derating factor ; Based on each temperature inflection point value Corresponding voltage derating factor and current derating factor Piecewise linear interpolation is used based on real-time temperature sampling values. The temperature range in which it is located is calculated to obtain the corresponding current temperature. Real-time voltage derating factor and real-time current derating factor ; Maximum permissible output voltage rating Multiply by the real-time voltage derating factor Obtain the permissible output voltage limit at the current temperature, and simultaneously determine the maximum permissible output current rating. Multiply by real-time current derating factor The permissible output current limit at the current temperature is obtained, and the permissible output voltage limit and permissible output current limit are used to obtain the variable... The changing functional relationship generates the corresponding temperature-permissible output derating curve.

8. The resistive load charger test and control system with CAN-BMS simulation according to claim 1, characterized in that, The step of dynamically adjusting the duty cycle of the first pulse width modulation signal based on the voltage deviation value to generate a second pulse width modulation signal for closed-loop regulation of the adjustable DC analog voltage includes: For voltage deviation value Performing a first-order difference operation yields the deviation change rate, which characterizes the trend of voltage deviation change. ; Obtain reference points at different duty cycles The output current state of the charger under test And based on different duty cycle reference points The output current state of the charger under test Determine the reference points at different duty cycles Below, the change in unit duty cycle The resulting steady-state output voltage change And based on the current duty cycle and The sign of the variable determines the dynamic gain coefficient corresponding to the current charger under test. ; Voltage deviation value Input an adaptive state observer, which uses... and The input is used to estimate the equivalent disturbance voltage caused by the coupling between internal noise of the voltage simulation module and load step disturbance. ;according to Calculate the duty cycle compensation amount, where The disturbance compensation coefficient is used, and the duty cycle of the first pulse width modulation signal is dynamically adjusted based on the duty cycle compensation amount to generate the second pulse width modulation signal for closed-loop regulation of the adjustable DC analog voltage.

9. The resistive load charger test and control system with CAN-BMS simulation according to claim 1, characterized in that, The step of dynamically adjusting the initial relay group control sequence based on the magnitude and direction of the real-time power deviation value to generate load regulation commands includes: The adjustment direction corresponding to the current relay group control is determined based on the direction of the real-time power deviation value. Based on the magnitude of the real-time power deviation and combined with the target test voltage Determine the optimal resistance change required to achieve real-time power deviation adjustment. ; Based on the adjustment direction and the amount of change in optimal resistance. And combined with the total equivalent resistance corresponding to the control sequence of the currently engaged relay group. Calculate the target total equivalent resistance. ,in This is the current power value; The main control module iterates through all possible relay combination states, calculates the theoretical equivalent resistance value corresponding to each combination, and selects the combination that satisfies the minimum |theoretical equivalent resistance value - target total equivalent resistance value| as the target relay group control sequence; The target relay group control sequence is compared with the current initial relay group control sequence to generate a load regulation command that only contains state change bits, specifically from 0 to 1 or from 1 to 0. Based on the load adjustment command, the magnitude and direction of the real-time power deviation are determined. If the real-time power deviation is positive and exceeds the first threshold, the current load is determined to be insufficient. The main control module selects one or more branches from the currently non-engaged relays that can make the total power closest to the target power after being connected, generates a relay activation command, and updates the relay group control sequence. If the real-time power deviation is negative and exceeds the second threshold, the current load is determined to be overloaded. The main control module selects one or more branches from the currently engaged relays that have the least impact on the total power after being disconnected, generates a relay disconnect command, and updates the relay group control sequence. The above steps are repeated cyclically to control the power load module to increase or decrease the number of connected resistor groups, so as to complete the automatic closed-loop load test of the charger under test.

10. The resistive load charger test and control system with CAN-BMS simulation according to claim 1, characterized in that, The sampling feedback module includes a voltage sampling submodule, a voltage tracking submodule, and a current sampling submodule. The actual voltage sampling value and actual current sampling value of the real-time power load acquisition module include: The voltage sampling submodule extracts a small-amplitude voltage signal from the high voltage by connecting a resistor divider network consisting of corresponding sampling resistors between the positive and negative terminals of the AC power supply, which serves as the original voltage sampling signal. The original voltage sampling signal is then connected to the inverting and non-inverting inputs of the corresponding operational amplifier for isolation and amplification, generating a voltage analog signal that is linearly proportional to the AC power supply. After passing through anti-aliasing filtering, the voltage analog signal is sent to the first analog-to-digital converter channel of the main control module to be converted into a real-time digital voltage sampling value. The voltage tracking submodule is used to bias the system power-on and the real-time voltage sampling value corresponding to the subsequent conversion of the voltage to low impedance DC in the voltage conversion module. The current sampling submodule has a shunt resistor connected in series in the negative AC circuit and uses a current sampling chip to detect the voltage drop signal across the shunt resistor. At the same time, the voltage drop signal is amplified into a proportional voltage signal to generate a current analog signal. After the current analog signal is filtered by anti-aliasing, it is sent to the second analog-to-digital converter channel of the main control module and converted into a real-time digital current sampling value.

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