A High-precision Analog-digital Conversion Nicd / Nimh Fast Charge Management Circuit Design Research,

With the development of the society, the charging management IC for modern battery is in strict demand, especially in the extensive application of portable products based on battery power supply. Both NiCd and NiMH battery are main competitors among numerous charge batteries, so the charging management IC for them has developing continuously.A novel fast charging management IC is designed in this thesis, achieving high stability and high efficiency. It is based on 0.5μm CMOS process with input voltage range from 4V to 6V and it can operate in the temperature range from 0℃to 70℃. The whole circuit is controlled by state machine, which can achieve charge control and state display through driving system's output with different state codings by operating all kinds of modules'output signals. For the safe and full charge, after the fast charging is finished, charger will change into Top-Off or Pulse-Trickle charge process automatically. Fast charge can be terminated by some modes such as negative delta voltage detection and maximum time. Voltage of battery can be sampled and analog-to-digital converted by an ADC with high precision inside and digital signals will be detected through ALU, then fast charging can be terminated reliably. Co-operated with the controllable current limiter or constant current source, the fast-charge IC can be not only made into high quality and low price independent charger, but also into in-machine charger. This circuit can realize the fast charge to one or more nickel cadmium or nickel metal hydride batteries.In this thesis, basic principles and some key points of fast charge management IC were given firstly. Then, the whole chip diagram was proposed according to the design specification and the whole chip operational principle was introduced. Based on the whole chip function requirements, sub-block design and simulation were completed. Since the chip was accomplished through the team work, the author payed particular attention to the analysis of the whole chip architecture and the design of sub-blocks. At last, the whole chip function simulation and typical performance characteristics simulation were presented. In the conclusion of this thesis, the research value of this circuit was pointed out, but it was suggested that layout and post-layout simulation should be indispensable.This thesis is a production of circuit principles and simulation practice. Based on the circuit principle analysis, the author simulated the sub-block circuits and the whole chip circuit by applying the EDA tool HSPICE. The simulation results indicated that the IC has achieved the expectation, both function target and electrical characteristics. The basic principle of fast charging management IC is testified, and this effort accumulates more experience to design with more perfect performance for the future.