Design Of Master-slave Mode Management Chip For Multi-cell Li-ion Battery Pack

By recent years, Li-ion battery has already become the most widely used chargeable battery for portable electronic products for its excellent performances such as high voltage rating, high energy ratio, no memory effect, low self-discharge rate, etc, it also begins to apply to motive force domain gradually, commonly used in laptops and power tools. The present multi-cell Li-ion battery management systems usually use a SCM combined with protection ASICs or ASICs fabricated by high voltage process, which always cause more cost, less reliability or lower accuracy. Hence, this thesis proposes a novel master-slave chip set formed management system, while devoting to research on various protection and management solutions. This system is appropriate for Li-ion battery pack with any number of cells. Each battery works with a slave-chip which is used for cell state information collecting, these information would be processed and exchanged with adjacent slave-chips through a special cascaded communication mechanism and finally reach the master-chip. The master-chip then processes these information as a processor and returns control signals, while directly communicating with the charger and discharging loop. Especially, both master and slave chips could be realized with 5V standard CMOS process, which makes low voltage processes managing high voltage applications possible. This system could not only achieve the necessary charging over-voltage first & second protection and discharging under-voltage first & second protection, but also realize the fast charging cell balancing and discharging PWM overload modulation, besides, it also integrates many practical functions by controlling LEDs like electric quantity display, timing, state & alarm indication, etc.