基于P型功率管电流采样和自适应参考电压的Buck型充电器设计

High Efficiency Buck Charger for Li-ion Battery with Power PMOS Current Sensing and Adaptive Reference Voltage

介绍了一种具有高效率、开关频率为2 MHz的Buck型锂电池充电器,它的工作过程分为启动、小恒定电流充电、大恒定电流充电、恒定电压控制和结束五个阶段。在恒流充电阶段,通过对P型功率管电流的采样和采用自适应参考电压,可以对充电电流的平均值进行控制,使得充电电流恒定,不受电池电压升高的影响。在恒压控制阶段,附加一条电压反馈回路,使得恒流阶段到恒压阶段的转换平滑。本设计用2P4M 350nm CMOS工艺实现,芯片面积2.8mm2。测试结果表明,芯片实现了充电的完整过程,其充电峰值效率为91%。

A high efficiency Li-ion battery charger operating at 2 MHz was presented.The charging procedure included start-up stage,small constant-current(CC)charging,large CC charging,constant-voltage(CV)controlling and turn-off.In CC mode,the converter regulated the average output current by sensing PMOS current and using adaptive reference voltage.By adopting this approach,the charger average output current kept constant during CC mode,regardless of battery voltage increasing.In CV mode,a feedback loop was established in addition to the preexisting current control loop,preserving the smoothness of the output voltage at the transition from CC to CV mode.The charger was implemented by 2P4 M 350nm CMOS process,wich a chip size of 2.8mm2(includes PADs).The test result shows that the whole charging procedure is realized,and the peak charging efficiency is 91%.