New Testing System Ensures Safety of EV Charging Cables
As electric vehicles (EVs) continue to gain traction across global markets, the infrastructure supporting their operation must evolve with equal rigor. Among the most critical components of this ecosystem is the In-Cable Control and Protection Device (IC-CPD), a compact yet vital safeguard embedded within Mode 2 charging cables. These cables, commonly used for home or portable charging, connect standard household sockets to EVs, offering convenience and flexibility. However, this very convenience introduces potential safety risks—especially when high-power AC charging occurs in uncontrolled environments such as garages, driveways, or public outlets. To mitigate these risks, international standards mandate that all Mode 2 chargers be equipped with an IC-CPD, which monitors electrical parameters and intervenes during fault conditions.
Despite its growing importance, the reliability of IC-CPD units hinges on rigorous pre-deployment testing. A recent breakthrough in test methodology, developed by researchers at Jiangsu Aviation Technical College and Suzhou Ulicar Technology Limited Company, introduces a comprehensive and automated system designed to validate the functionality and response times of IC-CPD devices before they reach consumers. The study, published in Computing Technology and Automation, details a hardware and software framework capable of simulating real-world charging scenarios, monitoring control pilot (CP) signal behavior, and verifying the performance of internal relays under fault conditions.
The research, led by Chen Cong, addresses a critical gap in manufacturing quality assurance. While IC-CPDs are mass-produced and widely distributed, their internal mechanisms must respond within milliseconds to overcurrent, overvoltage, ground faults, and leakage currents. A failure in any of these protective functions could lead to equipment damage, fire hazards, or even electric shock. Traditional manual testing methods are not only time-consuming but also prone to human error and inconsistency. The new system automates the entire evaluation process, ensuring repeatability, precision, and compliance with IEC 61851 and IEC 62752 standards—the benchmark regulations governing EV charging safety.
At the heart of the innovation is a custom-built test device that emulates the behavior of an electric vehicle during the charging initiation sequence, known as the CP (Control Pilot) guidance process. This multi-stage handshake between the IC-CPD and the vehicle ensures safe power delivery before the main contactors engage. The test system replicates each phase of this interaction, beginning with the detection of cable insertion, progressing through voltage level transitions, and culminating in the validation of PWM (Pulse Width Modulation) signal integrity.
The CP guidance process begins when the charging cable is plugged into a standard wall socket. At this point, the IC-CPD outputs a +12 V signal on the CP line, indicating readiness. When the vehicle connector is inserted, the onboard circuitry pulls this voltage down to approximately +9 V via a resistor network, signaling successful connection. The IC-CPD detects this change and responds by switching the CP line to a PWM signal—typically oscillating between +12 V and -12 V at 1 kHz with a specific duty cycle. This modulation communicates the maximum allowable current to the vehicle. Once the vehicle confirms the signal, it closes its internal relay, allowing the IC-CPD to activate its own power relays and begin energy transfer.
Chen Cong’s test system precisely mimics this sequence. It uses a microcontroller-based platform centered around the STM32F103RET6, a 32-bit ARM Cortex-M3 processor known for its robust peripheral support and real-time performance. The device actively participates in the CP handshake by dynamically switching between different resistor networks to simulate the vehicle’s expected responses. For instance, upon detecting the initial +12 V from the IC-CPD, the test system engages a 2.7 kΩ resistor to ground, replicating the first stage of vehicle detection. Subsequently, it introduces a 1.3 kΩ resistor in parallel, reducing the CP voltage to around +6 V—the final state indicating full readiness for charging.
What sets this system apart is its ability to monitor and verify the PWM signal with high temporal accuracy. By sampling the CP line through optically isolated input circuits, the device calculates both the frequency and duty cycle of the modulation. In validation tests, the system confirmed a PWM frequency of 1 kHz with a duty cycle of approximately 16.34%, aligning perfectly with standard specifications. Any deviation beyond acceptable tolerances triggers an immediate failure flag, preventing non-compliant units from passing inspection.
Beyond basic signal verification, the system performs advanced functional tests under simulated fault conditions. One of the most critical safety features of an IC-CPD is its ability to disconnect power rapidly when anomalies occur. The test platform evaluates four primary fault scenarios: overcurrent, overvoltage, residual (leakage) current, and loss of protective earth (PE) continuity. Each test measures not only whether the IC-CPD initiates a shutdown but also how quickly it does so—a parameter crucial for preventing thermal runaway or insulation breakdown.
For overcurrent testing, the system instructs the IC-CPD to enter a normal charging state and then simulates an overload condition. This is achieved through coordinated communication rather than physical load manipulation. Using LIN (Local Interconnect Network) bus protocols, the test device sends command signals to the IC-CPD, prompting it to artificially detect an overcurrent event. Upon receiving the command, the IC-CPD must deactivate its internal relays within a predefined time window. The system records the exact moment of disconnection via high-speed digital inputs and compares it against regulatory thresholds. For example, in the case of residual current detection—typically triggered by leakage exceeding 25 mA ± 5 mA—the IC-CPD must cut off power within 20 milliseconds. The test setup confirms compliance by capturing the relay status change with microsecond-level resolution.
The integration of LIN communication is particularly noteworthy. While the CP line serves as the primary analog control channel, many modern IC-CPDs also support digital diagnostics via LIN bus. This allows for bidirectional data exchange, enabling the test system to query internal status registers, retrieve error logs, and issue remote commands. The researchers implemented a fully isolated LIN transceiver circuit using the TJA1021T chip, ensuring signal integrity and protecting the test equipment from electrical transients. An additional layer of isolation is provided by the PI122U31 digital isolator, which separates the microcontroller’s UART interface from the LIN physical layer, enhancing system reliability in industrial environments.
Another key design consideration was power management and electrical isolation. Given that the test system interfaces directly with high-voltage AC circuits through the IC-CPD, galvanic isolation is essential to protect both the equipment and the operator. The solution incorporates multiple DC-DC converters and isolation modules. A TPS54331DR chip steps down the external 24 V supply to 5 V, which is then converted to 12 V using an FP6291 boost converter and to 3.3 V via an AMS1117 LDO regulator. These voltages power various subsystems, including optocouplers, relays, and the main processor.
To prevent ground loops and suppress noise, a B0505S isolated DC-DC converter separates the control logic ground from the communication and power grounds. This architectural choice ensures that transient spikes or leakage currents on the AC side do not interfere with the sensitive digital circuitry. Furthermore, solid-state relays (TLP172GM) are used to switch between test modes, allowing the system to alternate between CP signal monitoring and LIN communication without cross-talk or signal degradation.
From a user perspective, the system is controlled via a dedicated upper computer interface developed using PyQt5, a Python-based GUI framework. Operators can choose between manual step-by-step testing and fully automated sequences. In automatic mode, the software executes a predefined test flow, logging results in real time and generating pass/fail reports. All data is transmitted over Ethernet using the ENC424J600 controller, ensuring stable, low-latency communication even in electromagnetically noisy environments. The use of wired networking, as opposed to wireless alternatives, eliminates packet loss and timing jitter—critical factors when synchronizing with fast-acting protection circuits.
The practical implications of this work extend beyond laboratory validation. As EV adoption accelerates, especially in regions with aging electrical grids and diverse socket types, the role of portable charging solutions will only grow. Ensuring that every IC-CPD functions correctly is not merely a matter of regulatory compliance—it is a cornerstone of public trust in electric mobility. Defective or poorly tested devices could lead to catastrophic failures, undermining consumer confidence and stalling market growth.
Manufacturers of charging equipment can integrate this test system into their production lines, enabling 100% unit testing with minimal human intervention. The scalability of the design allows for parallel deployment across multiple stations, supporting high-throughput quality assurance. Moreover, the modular architecture means that future updates—such as support for new communication protocols or expanded test profiles—can be implemented through firmware upgrades rather than hardware redesigns.
While the current implementation focuses on Mode 2 charging, the underlying principles are adaptable to other charging architectures. For instance, similar methodologies could be applied to validate the control logic in AC wall boxes (Mode 3) or even in DC fast chargers, where protection mechanisms are equally critical. The emphasis on signal fidelity, timing accuracy, and fault simulation provides a template for next-generation test systems across the EV charging spectrum.
One limitation acknowledged by the authors is the current state of the user interface, which, while functional, lacks the polish expected in commercial-grade applications. Future iterations aim to enhance the graphical experience, incorporating real-time waveform visualization, historical trend analysis, and cloud-based reporting. Nevertheless, the core functionality has already been deployed in real-world testing environments, demonstrating its robustness and reliability.
The broader significance of this research lies in its contribution to the standardization and professionalization of EV component testing. As the industry moves toward greater interoperability and safety, independent verification tools like the one developed by Chen Cong and her team become indispensable. They empower manufacturers to go beyond minimum requirements, fostering a culture of proactive safety and continuous improvement.
In conclusion, the development of a comprehensive IC-CPD test system marks a significant advancement in electric vehicle infrastructure. By combining precise signal emulation, high-speed fault detection, and secure digital communication, the system ensures that one of the smallest components in the EV ecosystem performs one of the most important roles—protecting people, property, and the promise of sustainable transportation.
Chen Cong, Jiangsu Aviation Technical College; NI Feng, Suzhou Ulicar Technology Limited Company. Computing Technology and Automation. DOI:10.16339/j.cnki.jjsyzzdh.202402033