With the rapid expansion of the electric car industry, particularly in regions like China EV markets, the demand for electromagnetic compatibility (EMC) testing has surged. This growth is driven by the implementation of standards such as GB/T 40428-2021, which sets requirements for conductive charging of electric vehicles. In practical testing, electromagnetic interference (EMI) from charging equipment’s CP signals often leads to inaccurate results, making fault identification challenging. To address this, we designed and developed a low EMI intelligent CP signal generator. This device employs innovative signal control technologies to ensure precise output and minimal interference, significantly enhancing the accuracy and efficiency of EMC testing for electric cars. The proliferation of China EV models underscores the importance of such advancements, as they support the broader adoption of sustainable transportation solutions.
In this paper, we present a comprehensive study on the design, implementation, and validation of the intelligent CP signal generator. We begin by discussing the research background, highlighting the exponential growth in electric car production and the corresponding need for robust EMC testing frameworks. For instance, the China EV sector has seen a dramatic increase in sales, necessitating reliable testing tools to ensure compliance with international standards. We then analyze the specific problems encountered during EMC testing, such as the variability in CP signals from external charging devices, which can cause false failures in conducted and radiated emission tests. Our research aims to mitigate these issues through a modular system design that incorporates low EMI principles, advanced signal processing, and optimized PCB layouts. The significance of this work lies in its potential to standardize testing processes, reduce external interference, and foster the development of safer, more efficient electric cars in global and China EV markets.
The system architecture is built on a modular approach, comprising power, signal processing, control, and human-machine interface (HMI) modules. The power module utilizes a 12 V lithium battery with DC-DC conversion to provide stable energy, while the signal processing module generates and modulates CP signals based on control inputs. A 32-bit MCU serves as the core of the control module, orchestrating system operations, and the HMI module features an LCD display and keypad for parameter adjustment and status monitoring. This design ensures seamless integration and reliable performance, which is critical for adapting to various electric car models, including those prevalent in the China EV industry. The interconnection of these modules facilitates precise CP signal output, with voltage ranges from -15 V to 15 V and duty cycle adjustments from 0% to 100%, operating at a stable frequency of 1,000 Hz. The following table summarizes the key specifications of the system modules:
| Module | Function | Key Components | Performance Metrics |
|---|---|---|---|
| Power Module | Supply stable DC power | 12 V battery, DC-DC converter | Output stability: ±0.1 V |
| Signal Processing | Generate and modulate CP signals | AD5761R DAC, AD8610 op-amp | Voltage range: -15 V to 15 V |
| Control Module | System coordination | 32-bit MCU | Processing speed: 100 MHz |
| HMI Module | User interaction | LCD, keypad | Display resolution: 128×64 pixels |
Low electromagnetic interference design is a cornerstone of our approach, as it directly impacts the accuracy of EMC testing for electric cars. The reference voltage generation circuit employs a 16-bit high-precision DAC chip, AD5761R, known for its excellent temperature stability and linearity. This is coupled with a buffer stage using the AD8610 operational amplifier, which features low input offset voltage and minimal temperature drift. The output voltage \( V_{\text{out}} \) can be expressed as:
$$ V_{\text{out}} = V_{\text{ref}} \times \frac{D}{2^n} $$
where \( V_{\text{ref}} \) is the reference voltage, \( D \) is the digital input code, and \( n \) is the resolution in bits (16 in this case). This equation ensures precise voltage control, which is vital for maintaining signal integrity in diverse testing environments, including those for China EV models. Additionally, temperature compensation networks are integrated to minimize drift, further enhancing reliability. For PWM-based duty cycle control, we use a high-speed comparator, LT1719, to generate pulses with minimal propagation delay. The duty cycle \( \delta \) is defined as:
$$ \delta = \frac{T_{\text{on}}}{T} \times 100\% $$
where \( T_{\text{on}} \) is the on-time and \( T \) is the total period. A dead time control circuit, incorporating RC delay networks and Schmitt triggers, prevents shoot-through by enforcing a 200 ns gap between switching events. In the output stage, the IR2110 half-bridge driver ensures robust operation with built-in protection mechanisms, such as overcurrent and undervoltage lockout, which activate within 2 μs of fault detection. These design elements collectively reduce EMI emissions by more than 15 dB below standard limits, as validated through rigorous testing.
PCB design optimization plays a critical role in minimizing electromagnetic interference, which is essential for the reliable EMC testing of electric cars. We adopted a four-layer stack-up: the top layer for analog and control signals, the second layer as a solid ground plane, the third for power distribution, and the bottom layer for digital circuits. This arrangement provides low-impedance return paths and effective shielding. Key considerations include strict partitioning between analog and digital domains, star-topology power distribution to prevent cross-talk, and localized shielding for noise-prone components like switching regulators. The following table outlines the PCB layer specifications and their functions:
| Layer | Function | Key Features |
|---|---|---|
| Top Layer | Analog and control signals | Differential pairs with controlled impedance |
| Second Layer | Ground plane | Continuous copper pour for EMI reduction |
| Third Layer | Power distribution | Segmented regions for different voltage levels |
| Bottom Layer | Digital circuits | Isolated sections to minimize noise coupling |
To further enhance signal integrity, we implemented length-matching for critical traces and used multiple decoupling capacitors in parallel to lower equivalent series inductance. The characteristic impedance \( Z_0 \) of transmission lines is calculated using:
$$ Z_0 = \sqrt{\frac{L}{C}} $$
where \( L \) is the inductance per unit length and \( C \) is the capacitance per unit length. By optimizing these parameters, we achieved a balanced design that supports the high-frequency operation required for CP signals in electric car testing, particularly for the evolving China EV sector. Experimental results confirm that these PCB strategies contribute significantly to the device’s overall EMI performance, ensuring compliance with international standards.
Experimental validation was conducted in accordance with GB/T 40428-2021, focusing on the device’s EMI characteristics and CP signal quality. The testing protocol included three phases: functional verification, EMC compliance checks, and real-world application with various electric car models. In the functional tests, we measured key parameters such as output voltage, duty cycle, and frequency stability. The results, summarized in the table below, demonstrate that the device meets all design specifications, with a signal frequency fixed at 1,000 Hz and precise adjustability across the entire range. This is crucial for accommodating the diverse requirements of China EV manufacturers, who often face unique charging compatibility challenges.
| Parameter | Design Target | Measured Value | Tolerance |
|---|---|---|---|
| Output Voltage | -15 V to 15 V | -14.98 V to 15.02 V | ±0.02 V |
| Duty Cycle | 0% to 100% | 0.1% to 99.9% | ±0.1% |
| Frequency | 1,000 Hz | 999.5 Hz to 1000.5 Hz | ±0.5 Hz |
| EMI Margin | >15 dB below limit | 18 dB below limit | N/A |
EMC testing involved comprehensive assessments of conducted and radiated emissions, electrostatic discharge, electrical fast transients, and surge immunity. The device’s emission levels were consistently more than 15 dB below the standard limits, confirming the effectiveness of our low EMI design. For instance, the radiated emission \( E_{\text{rad}} \) can be modeled as:
$$ E_{\text{rad}} = k \cdot \frac{I \cdot l \cdot f^2}{r} $$
where \( k \) is a constant, \( I \) is the current, \( l \) is the antenna length, \( f \) is the frequency, and \( r \) is the distance. By minimizing \( I \) and \( l \) through optimized circuitry, we achieved significant attenuation. In real-vehicle tests, the device seamlessly integrated with multiple electric car models, eliminating external charging interference and improving test accuracy by over 40%. This success highlights its applicability in China EV environments, where standardization is key to market growth.
Analysis of the test results reveals several key insights. First, the intelligent CP signal generator consistently delivered stable performance across all operating conditions, with no significant drift in output parameters. Second, the low EMI design not only met but exceeded regulatory requirements, providing a buffer that accounts for environmental variations. Third, the device’s adaptability to different electric car architectures, including those in the China EV domain, underscores its versatility. We attribute these outcomes to the synergistic combination of advanced components, meticulous PCB layout, and robust control algorithms. The following equation illustrates the overall system efficiency \( \eta \):
$$ \eta = \frac{P_{\text{out}}}{P_{\text{in}}} \times 100\% $$
where \( P_{\text{out}} \) is the useful signal power and \( P_{\text{in}} \) is the input power. In our tests, \( \eta \) averaged 92%, indicating minimal energy loss and high reliability. These findings validate the device as a dependable tool for EMC testing, paving the way for broader adoption in the electric car industry.
In conclusion, our research demonstrates significant innovations in the development of a low EMI intelligent CP signal generator for EMC testing of electric vehicles. Key technological advancements include a multi-stage EMI filtering approach for power supply design, which achieved emission levels more than 18 dB below standard limits, and a high-precision signal control circuit enabling wide-range voltage and duty cycle adjustment. The engineering application value is evident in its deployment across multiple automotive testing facilities, where it has reduced average testing time by 42.6% and enhanced fault detection accuracy. For the future, we plan to refine electromagnetic shielding techniques, expand protocol support for emerging China EV standards, integrate network-based monitoring capabilities, develop intelligent diagnostic algorithms for fault localization, and explore novel EMC testing methodologies. These efforts will further solidify the role of such devices in promoting the safe and efficient growth of the electric car ecosystem worldwide.