Research And Design On Multi-Function And Multi-Mode Battery And Power Management ICs For Portable Electronic Devices

A complete power management solution should contain battery management ICs as well as varieties of regulators that provide stable power supplies to different kinds of loads. It's an inevitable trend in future to integrate the battery management ICs with the regulators for power management in a monolithic chip. Thus, this paper proposes an integrated battery and power management solution for portable electronic devices, which includes a lithium ion battery charger, a Battery Management System (BMS), two DC-DC converters with a maximum output current of 1A and two LDO linear regulators with a maximum output current of 800mA. In order to realize this system, it's necessary to do researches and designs on the sub-systems.In the research and design on the lithium ion battery charger, this paper adopts an improved Constant Current-Constant Voltage (CC-CV) charging approach, which is more secure and reliable than the traditional way by making a smooth transition between the CC and CV phases. Meanwhile, the charger IC also needs thermal protection. In order to avoid the charger IC turning on and off repeatedly around the protection points, this paper also adopts a soft thermal protection technique. A testing chip has been implemented in the CSMC 0.6μm mixed-signal CMOS process. The simulation and the testing results verify the proposed charging approach and the soft thermal protection technique.In the research and design on the BMS for lithium ion battery packs, this paper chooses the master-slave scheme based on a novel communication mechanism to ensure the system precision in the applications on multi-cell battery packs. The master-slave system is composed of a Master Processor (MP) and a string of slave manager cells (SMCs). Each SMC corresponds to a battery cell. The commands from MP and the battery status signals from SMCs are transferred cell by cell upwards and downwards respectively. The unique circuits transferring signals between two adjacent SMCs are the key to the proposed system. The testing results verify that the proposed method for data communication and the whole system functioned well.In the research and design on the DC-DC converter, this paper first proposes an averaged PWM model that is suitable for system stability design. Then a novel PWM/PFM dual-mode DC-DC Buck converter with a maximum output current of 1A is proposed. Switching between PWM and PFM is creatively controlled by limiting the minimum on-time, which is actively alters as the ratio of the output and input voltage varies. This scheme has a simple structure and switches naturally between PWM and PFM. The proposed DC-DC converter has a maximum input voltage up to 24V and a wide range for the output voltage. To keep the system stable in a wide range, the PWM loop utilizes novel active slope compensation. The chip is implemented in the TSMC 0.6μm 40V BCD process. The simulation and testing results show that the system keeps stable in a wide range; the transient response is less than 1.5% and 0.6% respectively when the load switches from 50mA to 200mA and the input voltage jumps from 19V to 24V; the maximum efficiency is up to 95%.In the research and design on LDO linear regulator, this paper first has analyzed the essential terms of LDO, including frequency compensation, dropout voltage, transient response, line regulation and load regulation. Then a high gain LDO with an additional fast response loop as well as SRE circuit is proposed. A testing chip has been implemented in the CSMC 0.5μm mixed-signal CMOS process. The simulation and the testing results show that due to the high gain and fast response design, the LDO has a line regulation of 1.77mV/V and a load regulation of merely 4.5μV/V. The transient response is less than 0.45% when the input voltage jumping between 4.5V and 5.5V.This paper has achieved the researches, designs and verifications on battery charger, BMS, DC-DC converter and LDO regulator. Integrating these sub-systems with I2C bus, a novel battery and power management for portable electronic device with multi-function and multi-mode outputs can be obtained. Due to the high integrity, low application complexity and intelligent control, this solution will replace the traditional battery and power management system composed of separated ICs.