Modularized Lithium-ion Battery Equalization Circuit Based On Energy Bus

With the continuous improvement of people's awareness of environmental protection and the development of new energy technologies,lithium-ion batteries,as a carrier for storing electrical energy,are favored by people for their long life,no memory,small size,and high energy density.At present,lithium-ion batteries have been widely used in electric vehicles,communication energy storage,spacecraft energy storage,and new energy energy storage.Because lithium battery cells have the disadvantages of low voltage level and small capacity when used alone,it is generally necessary to use multiple lithium-ion batteries in series.Due to the individual differences of lithium-ion batteries,a single-cell battery is overcharged or over-discharged during the use of the lithium-ion battery,which affects the battery life and reduces the available capacity of the lithium-ion battery.Introduce battery equalization technology.In view of the above,this paper proposes a modular lithium-ion battery equalization circuit based on the energy bus topology.In terms of specific circuit implementation,in order to meet the balancing needs of batteries with different capacities,this paper proposes two specific balancing circuits,a low-power equalization scheme and a high-power equalization scheme.The low-power equalization solution maps battery voltages at different levels to the energy bus through capacitors,and realizes energy transfer from high-voltage batteries to low-voltage batteries.The high-power equalization scheme uses a transformer as a bridge,which can transfer high-power electrical energy to the energy bus for exchange.In order to further improve the energy balance efficiency of the high power equalization scheme,this design cleverly uses the resonant frequency of the resonant capacitor and the primary inductance of the transformer as the frequency of the driving signal to implement the soft switching technology,which greatly reduces the energy loss during the switching process of the MOS tube.In addition,in order to meet the demand for weight in the aerospace field,this paper uses a planar transformer,which has smaller magnetic loss,higher consistency,and lighter weight than traditional transformers.The two sets of schemes are compared.The low-power scheme has the advantages of small size,low cost,and simple structure.The high-power scheme has the advantages of high balancing efficiency and fast speed.In order to better realize the battery equalization technology,a voltage acquisition circuit is designed in this paper.The voltage acquisition circuit designed in this paper uses the LTC6804-2 chip as the battery voltage acquisition chip,which can achieve a sampling error of less than 1.2m V.The low power equalization circuit proposed in this paper can achieve 30 m V equalization accuracy,and the high power equalization circuit can achieve 15 m V equalization accuracy.In addition,the equalization time of the equalization scheme proposed in this paper has nothing to do with the number of batteries,but only with the capacity of the batteries.