Biography
Enrollment Date: 2012
Graduation Date：2015
Degree：M.S.
Defense Date：2015.06.03
Advisors：Liji Wu
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Design and Implementation of High Precision Acquisition Front-end Circuit for BMS SoC in New Energy Vehicles
Abstract:
With the rapid promotion of new energy vehicles, how to increase the cruising distance and service life, and how to improve security of its battery system are becoming tough and urgent problems. Design of battery management system (BMS) and battery management IC, which can monitor and manage power batteries, is now a hot research topic. One of the key design challenges is battery parameters detection with high accuracy, which means that the research of high-precision battery parameters acquisition front-end circuit for BMS IC is of great value.This paper, using IC design methodology of System to Chip, studies the design of high-precision battery parameters acquisition front-end circuit for BMS SoC (System on Chip). The system-level PCB circuit design and verification are done. High-precision and synchronous detection of multi-channel cell voltage is achieved by two editions of BMS PCB implementation. On chip level, this paper designs a 16bit Σ-Δ ADC modulator, which is the key module to achieve high detection accuracy of BMS IC.Firstly, based on the research of BMS structure and acquisition front-end circuit, the first version of BMS PCB is designed, which completes the implementation and verification of basic functionality of the acquisition front-end circuit and achieves its core function, including voltage, current and temperature detections. Secondly, in order to achieve high-precision multi-channel voltage synchronous detection, this paper presents a new acquisition front-end circuit based on improved flying capacitor structure. The second edition BMS PCB is designed, which can detect multi-channel cell voltage simultaneously. Cell voltage detection error is less than 5mV, and accuracy is about 0.15%. They can monitor cell voltage variation during battery charge and discharge processes. System-level high-precision acquisition front-end circuit design and implementation verifies the feasibility of circuit design in BMS SoC.Then, since the chip-level acquisition front-end circuit require higher AD conversion precision, and voltage holding time of synchronous sampling circuit is limited by the ADC conversion time, a 16 bit Σ-ΔADC modulator, the key module of the chip-level acquisition front-end circuit, is designed in this paper, based on ASMC 0.5μm 60V BCD automotive electronics process. First, Matlab behavioral simulations are done to study the effects of non-ideal factors on modulator performance. Transistor-level circuit design and simulation are then carried out, along with the layout design and post-simulation. Simulation result shows: at 1.024MHz sampling frequency and over sampling rate of 256, the Σ-Δ modulator ENOB (Effective Number of Bits) reaches 16.58，SNDR (Signal To Noise And Distortion Ratio) achieves 101.6dB. The circuit is taped out.