The Design Of The Power Lithium-ion Battery Charger

Promoting the development of green energy and cycle energy has become anurgent subject to be solved in the international community. Lithium-ion batterybecomes the development direction of the new generation of the power supplybecause of its high density, high working voltage, no pollution, safely andquickly charging. However, Lithium-ion battery is different from otherrechargeable batteries. Lithium-ion battery has its special characteristics ofcharging and discharging which need to design the special charger. Due to thedesigns of the charger in the market are mostly just for their single user andobject, so the purpose of this paper is to design a high-performance charger thatcharging current is adjustable.This paper is based on the electrochemical reaction mechanism of lithium-ion battery charging, charging and discharging characteristics, the commonlyused charging methods. The way that constant current charging and constantvoltage charging is choosed. The overall design strategy is identified. Thecharger is divided into two parts, hardware circuit system and communicationsystem. The Linear Technology’s DC/DC controller chip LTC3891and powermanagement chip LTC4000are selected in the hardware circuit system, andcorresponding peripheral circuits are also built. The paper mainly introduces thebasic principle of the hardware circuit and the parameters calculation method ofthe peripheral circuit components. Combining LTC4000’s features, implementthe charging current is adjustable, and thus put forward a design scheme that donot rely on single chip microcomputer to control PWM waveform. Thecommunication system is designed for improving charger’s intelligent degree.The AD sampling circuit, DA converter circuit and CAN communication circuitare all designed, and corresponding program flow are also designed. The dedicated hardware simulation tools LTspice IV is used in this paper.The simulation focuses on two cases that the battery initial voltage is lower thanthe low battery threshold voltage and the battery initial voltage is higher than thelow battery threshold voltage. The simulation result consistent with thetheoretical analysis, show that the charger has the ability to intelligently charge,and thus proving the correctness and feasibility of this research.