The rapid introduction of electric vehicles is accelerating the innovation of battery technology, including battery management chips. One of the key aspects is that integration can realize the benefits of easy design, security and high performance. New progress in this field will help to maximize the potential of electric vehicle batteries without affecting the health and safety of batteries.

    Electric vehicle batteries may fail for a variety of reasons. Mechanical stress or damage after a collision may puncture the battery pack or damage a single battery. Electrical stress, such as overcharging, can also cause safety problems and reduce overall battery life.

    The battery management system (BMS) helps to monitor the safety and efficiency of EV Batteries. One of its main functions is to ensure that each lithium-ion battery in the battery pack operates in its safe working area (SOA) defined by voltage, current and temperature. Operating outside a fairly rigorous SOA can lead to serious consequences, such as catastrophic battery failure or, worse, thermal runaway. This is why the battery junction box (BJB) is particularly important.

    BJB is one of the three functional modules in BMS. It measures and records the total battery voltage and the current flowing into and out of the battery, so as to accurately calculate its state of charge (SOC). This enables accurate mileage calculation and allows the driver to know the amount of battery remaining. It also implements key safety functions, such as contact inspection, isolation monitoring and overcurrent detection. BJB needs to meet ASIL C or ASIL D functional safety level for current and voltage measurement in automotive applications.

    One of the challenges of high-voltage system communication is to isolate the low-voltage semiconductor (12 V) from the high-voltage (400 V) battery side. Here, the communication of BMU (battery management unit) is traditionally carried out through CAN bus, but the daisy chain connection of BJB through transformer physical layer (TPL) is an attractive alternative. TPL interface is specially designed for BMS and supports high isolation voltage up to 2KV. The benefits of this solution include stronger electromagnetic compatibility (EMC) characteristics, higher high voltage isolation, better communication speed and synchronous measurement. Thus, the complexity related to software is reduced and the BOM cost is reduced.