Distributed Single Cell Chargers Of Battery String

Battery string is being more and more widely used in the fields of transportation, power system, communication, etc. The cycle life of 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 puts forward a novel single cell charging solution of the battery string based on switch transistor style post regulation and the high frequency Bus. Each secondary circuit, controlled by the switch transistor and parallel connected with a single cell, shares one primary circuit through the high frequency Bus. This design figures out the problem of the battery string unbalanced charge with the consideration of efficiency, volume and cost.This dissertation gives exhaustive narration of the high frequency bus design using the two-transistor forward topology, and introduces common post regulation methods and their respective advantages and disadvantages. In view of the synchronization problem in post regulation, this dissertation proposed several solutions of producing synchronous saw-tooth wave. Finally we used the chip UC3843 to produce stable and reliable synchronous saw-tooth wave. Aiming at multi-output post regulation situation, take measures to minify the glitch on the voltage wave of the bus, meanwhile, improved the current sampling waveform.A single-battery charging system of the battery string that consists of 3500mAh, 3.7V lithium-ion batteries was designed. The primary circuit was the dual switched forward converter, and the secondary circuit was the post regulator with switch transistor as the charging circuit module. In the experiment, we used four charging circuit modules to charge four Lithium-ion batteries. The charger which could realize the function of constant-current charge, constant-voltage charge and charging circuit cut off while battery fully charged. These were controlled by the switch transistor. The charging voltage and current could be controlled with the precision of 1%.The charger can realize fully charged state display, and can transmit the charging state signal among single-battery charging circuits and finally transmit to the bus circuit. Especially, the circuit can use the energy of the battery to detect the battery itself to get over discharge judging signal and transmit within modules to finally get the over discharge judging signal of the battery string. The charging circuit module had low standby power consumption, and all devices were low cost devices.The design detail was given and the reliability was verified by its experiments compared with series-charging solution experiment.