| The cycle life of the battery string has direct impact on the energy utilization and the whole life,reliability and cost of the corresponding system.This dissertation explores the topic on the charge of series battery string from the aspect of increasing its cycle life,and puts forward a novel single cell charging solution of the battery string based on the magnetic amplifier(MA) and the high frequence Bus.Each secondary circuit,controlled by the MA and parallel connected with a single cell,shared one primary ciruit with the others by the high frequency Bus.This design figures out the problem of the battery string unbalanced charge with the consideration of efficiency,volume and cost effectively.The characteristics of the MA as the post regulator in different circuit topology was explored,and the different operation modes and reset methods of MA in the single-ended forward and flyback converter and the half-bridge converter were presented.Then drew the conclusion that the forward type converter was more suitable for this project,which was verified by the experiments.The small-signal models of the MA was derived,and the feedback compensation was given,which was the basis of the control cicuit design of the charger.At last,a single-battery charging system of the battery string that consists of 3600mAh,3.7V lithium-ion batteries was designed.The primary circuit was the dual switched forward converter,and the secondary circuit was the post regulator based on the MA of Toshiba cobalt based amorphous alloy.The charger which could realize the function of trickle charge,constant-current charge, constant-voltage charge and floating charge was controlled by the MA completely.The charging voltage and current could be controlled with the precision of 1%.The charger had the self pretection mechanism of overdischarge,full-charged,overvoltage, overcurrent and overheat.The design detail was given and the reliability was verified by the experiments.
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