The Design Of The Protection Circuit For Over-voltage And Over-current Of The Battery For Portable Device

As the power supply of electronic devices, the batteries are booming with the development of market of portable electronic devices. The requirement of secondary batteries is increasing for their reusable and safety for environment, and the Lithium-ion Polymer Battery has become more popular than the Nickel-cadmium Battery and the Nickel-hydrogen Battery within the secondary batteries. But the Lithium-ion Polymer Battery is easy to be damaged by over-charge, over-discharge, over-discharge current and short, so each of them needs a protection circuit.This thesis makes analyzing and design begins with the principle and structure of protection circuit, and sets defense mechanism to the error states. At the same time, this thesis designs self-biasing referenced circuit and comparator operating on the sub threshold region, the state of standby to reduce the power consumption effectively. Based on the discussion above, main sub-blocks of the protection circuit are designed and the process is demonstrated. The sub-blocks include over-charge comparator, over-discharge comparator, over-discharge current comparator, short delay, oscillator, counter, level shift, vref&bias and logic circuit.Finally, the design is simulated with HSpice based on the UMC 0.6μm high withstand voltage CMOS process, and the simulation results proved the success of front-ended design.