| Due to the advantages of fast charge-discharge,long life,and high-power density,lithium-ion batteries have gradually occupied a larger share of the energy market and have been widely concerned by researchets.Aimed at lithium batteries for portable electronic products,a withstand high-voltage charging circuit is designed for lithium-ion batteries of portable electronic products in this thesis.The main contens including:Firstly,based on the analysis of the current-voltage characteristics and temperature characteristics of the lithium battery during the charging process,this thesis discusses six kinds of common charging control modes and analyzes the mainstream charging topology.At the same time,the charging scheme of the withstand high-voltage charging circuit for lithium battery is given in this thesis.Secondly,the constant voltage(CV)loop and a constant current(CC)loop of ithium battery charging circuit are modeled respectively in this thesis.And,this thesis discusses the small signal model of each module in the charging circuit and the system transfer function.Based on analyzing the loop compensation network,this thesis discusses the type II-B compensation of transconductance amplifier and the stability of the charging circuit system.according to the stable conditions of the charging circuit system,the design specifications of the key circuit of the CV loop and the CC loop are given in this thesis.Thirdly,based on the second-order temperature model of the MOS transistor threshold voltage in BSIM4.5.0,a full MOS voltage reference circuit is designed by adopting the square law current relationship of MOS transistor and body diode temperature compensation technology.And,the designed voltage reference achieves the temperature coefficient of 9.79ppm/℃ and power supply rejection ratio of 109 d B at low frequency.Finally,these key sub-circuits of lithium battery charging cuircuit,which include low dropout regulator circuit,bandgap reference,error amplifier,high gain comparator,oscillator,charge pump,ramp generation circuit and driving circuit,are designed in TSMC 0.18μm BCD process.Based on the functional requirements of the lithium battery charging circuit,these auxiliary circuits,which include the target voltage setting circuit,input voltage monitoring,temperature detection and LED status display are designed.Simulation results show that the input voltage of the lithium battery charging circuit is 5～12V,the switching frequency is 500 k Hz,and the maximum constant current is 3A.And the lithium battery charging circuit can charge the lithium battery with a rated voltage of 3.6～4.4V,and has these performance of the charging voltage accuracy of ±0.19%,the charging current accuracy of ±1.77% and the peak efficiency of 93.2%. |
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