In new energy electric vehicles, the BMS (Battery Management System) acts as a guardian, silently protecting the safety and performance of the battery. It accurately monitors voltage, current, and temperature, preventing overcharging and over-discharge, and enhances endurance through intelligent balancing technology. Inductors play an indispensable role in key aspects of the BMS system's power conversion, filtering, and isolated communication, particularly in noise suppression, voltage conversion, and signal integrity. Therefore, selecting the right inductor is crucial for improving the safety and efficiency of electric vehicles.
1- The main application of inductors in BMS
In the automotive BMS system, inductors are primarily used in power conversion, balancing circuits, and filtering circuits, with specific applications and requirements as follows.
1.1 DC-DC Converter
The DC-DC converter is one of the most common modules in a BMS. The various modules within the BMS (MCU, AFE chip, temperature sensor, current sensor, etc.) typically require different, stable low-voltage DC voltages (such as 5V, 3.3V, 1.8V, etc.). These voltages are generated by the DC-DC converter from the battery pack's bus voltage (high voltage) or low-voltage auxiliary battery (12V). In Buck/Boost circuits, the inductor is the core component for energy storage and filtering. It stores energy when the switching transistor is on and releases it to the output when the transistor is off, thereby achieving voltage conversion and stabilization.
The selection of inductance value directly affects current ripple, conversion efficiency, and transient response. The demand for power inductors in Buck/Boost converters primarily includes: high rated current, low DC resistance, good temperature stability, and miniaturized design.
1.2 Active Balancing Circuit
Active balancing circuits achieve charge balance between battery cells through energy transfer, thereby improving the use efficiency of the battery pack. In some types of active balancing topologies, inductors are used as media for energy transfer. Inductors alternately store and release energy within a switching cycle to achieve energy transfer between cells or between cells and the bus. Some auxiliary DC-DC converters in balancing circuits also use inductors for filtering.
The performance requirements for inductors in active balancing circuits primarily include miniaturization, low loss, high efficiency, appropriate inductance values, and saturation current, while meeting automotive-grade performance requirements such as wide temperature range and vibration resistance.
1.3 EMI/EMC Filter Circuit
Filtering inductors in BMS are primarily used for power input/output filtering or communication line filtering, placed at power input/output ports and communication line interfaces. Common mode chokes are used to suppress common mode noise on power lines, preventing internal noise in the BMS from interfering with other devices or external noise from coupling into the BMS. Differential-mode inductors are used to suppress differential-mode noise on power lines.
EMI/EMC filter inductors (differential mode and common mode) must meet the following requirements:
◾ Impedance characteristics: Good high-frequency impedance characteristics.
◾ Rated current: Relatively smaller than power inductors, but greater than the maximum working current flowing through this line.
◾ Saturation current: Need to withstand possible transient high currents (such as load sudden drop) without saturating and failing.
◾ Frequency range: Covers the noise frequency band to be suppressed.
Application of Codaca inductors in automotive BMS systems
2- Requirements for Inductors in Automotive BMS
Inductors for automotive BMS systems must not only meet basic performance requirements such as inductance value, current, impedance, and frequency, but also comply with the following automotive-grade standards:
◾ Operating temperature: -40°C to +125°C, or even higher, capable of adapting to all possible automotive operating environments.
◾ High reliability: Product life (10-15 years or longer), compliant with AEC-Q200 standards, strong resistance to vibration and shock.
◾ Environmental standards: Compliant with RoHS, REACH, halogen-free, and other environmental standards.
◾ Traceability: Certified under the IATF16949 system, meeting the stringent supply chain management and quality traceability requirements of the automotive industry.
Different circuits in automotive BMS have distinctly different requirements for the core performance parameters of inductors (saturated current, DCR, high-frequency impedance, filtering band), but all applications must meet stringent automotive-grade standards for temperature, reliability, mechanical, and environmental aspects (compliant with AEC-Q200). When selecting inductors, it is essential to carefully evaluate these key parameters based on the specific application and conduct thorough testing and verification to ensure the performance, reliability, and safety of the entire BMS system.
3- Codaca Provides High-Performance Automotive-Grade Inductors for Automotive BMS
Codaca has been dedicated to inductor research and development over24 years, providing the automotive industry with a variety of high-performance inductors in multiple series. Codaca has independently developed several series, including automotive-grade molded power inductors, automotive-grade high current power inductors, and automotive-grade common mode chokes, to meet the design requirements of automotive electronics miniaturization, integration, low loss, and high efficiency.
[Click on the image to learn more about Codaca's automotive-grade inductors]
3.1 Automotive-Grade High Current Power Inductors
Codaca's independently developed automotive-grade high current power inductors use low-loss magnetic core materials and flat wire coil design, featuring extremely low core loss and excellent soft saturation characteristics, enabling them to withstand higher transient peak currents. The inductor's maximum saturation current can reach 350A, with a working temperature range of -55℃ to +155℃, meeting the demanding automotive electronic environments of high current and high operating temperatures. It can maintain low temperature rise on the inductor surface while enduring high current for extended periods, making it widely used in various topological solutions for automotive BMS systems.
Recommended products: VSRU / VSBX / VPRX and other series.
3.2 Automotive-Grade Molded Power Inductors
Codaca's independently developed automotive-grade molded Power inductors utilize innovative technologies and processes, including low-loss core materials and a new electrode design. This significantly reduces inductor size and losses while improving reliability. This solves technical challenges such as coil deformation and crack issues during the inductor molding process. This reduces overall losses in automotive-grade molded power inductors by over 30%, allows for an operating temperature of up to 165°C, and achieves power efficiency of up to 98%, effectively improving BMS system reliability and DC-DC conversion efficiency.
Recommended Products: VSAB / VSEB / VSEB-H / VPAB and other series.
3.3 Automotive Grade Common Mode Chokes
Codaca's automotive grade common mode choke features high impedance characteristics, efficiently suppressing common mode noise. With a compact size and low profile design, it is suitable for surface mount technology, meeting the demands of miniaturization in automotive electronics; high reliability, operating temperature: -40℃ ～ +125℃ / -55℃~+150℃, effectively suppressing common mode noise interference in DC power lines, particularly in circuits such as DC-DC converters in new energy vehicles and BMS battery management systems, effectively reducing the impact of electromagnetic interference on system stability.
Recommended Products: VSTCB / VCRHC / VSTP, and other series.
