A High Precision Multi-Cell Battery Voltage Detecting Circuit for Battery Management Systems

This paper presents a high precision direct multi-cell Battery Voltage Detecting Circuit (BVDC) for Battery Management Systems (BMS) in electric vehicles. BVDC in BMS must be able to accommodate direct voltage input up to tens of volts from series connected batteries, fulfil the precision needs by battery state of charge estimation algorithm. The BVDC circuit is designed with a 0.5μm 1-poly 3-metal high voltage (HV) 60V Bipolar-CMOS-DMOS (BCD) semiconductor process. System optimization design of HV multiplexer and incremental sigma-delta analog-to-digital converter (ADC) in BVDC circuit eliminates the need of amplifier-resistor based level shift, and any static current through HV signal path, which greatly improved the conversion accuracy. Post layout extracted simulation result shows that the typical conversion error is less than 0.3mV@1MHz for series connected batteries without extra calibration.