Research On High Precision Voltage And Current Sampling Scheme Based On Automotive Battery Cells

As the government and the public pay more and more attention to renewable resources and new energy technologies,the development of new energy vehicles,portable devices and smart grid technologies has great prospects,and batteries as the power source of these devices also attracts much attention.The battery management system is the key to ensure the safe,efficient and intelligent operation of the battery.The battery management system can monitor and manage the battery in real time,and one of the most important functions is to monitor the battery power.Accurate monitoring of battery power requires high-precision sampling of the battery voltage and current signals.Therefore,this thesis investigates the high-precision voltage and current sampling scheme for battery cells,and designs a high-precision voltage and current sampling circuit for battery cells based on automotive battery cells,which consists of a sampling front-end circuit and a Delta Sigma modulator.The main work of this thesis is as follows:1.For the high common mode voltage of the automotive battery pack,a sampling scheme using the sampling capacitor of switched-capacitor circuit to isolate the high common mode voltage is proposed,and the sampling scheme is applied to the signal sampling front-end circuit.However,since the design of the high-voltage circuit involves many difficulties such as circuit reliability and surge protection,this thesis chooses to verify the feasibility and accuracy of the scheme in the low-voltage domain.2.The sampling front-end circuit and the modulator are designed and simulated separately,where the sampling front-end circuit is a switched-capacitor structure and the Delta Sigma modulator has a precision of 16 bits with a second-order one-bit quantized CIFB structure.The chopping technique is introduced to reduce the offset voltage and low frequency noise of the circuit,the thermal noise of the circuit is decomposed to calculate the value of the capacitor in the circuit,and the index parameters of the op-amp in the circuit are calculated.The gain error,the offset error and the temperature drift of the error of the circuit are simulated by inputting a step wave at different temperatures,and the linearity of the circuit is simulated by inputting a sine wave.3.The circuit is designed and simulated based on a 55 nm CMOS process.The voltage sampling range of the circuit is 0～5.5V,and the sampling error is less than 0.5m V after calibration,and the minimum resolution is about 16 bit.The current is calculated by sampling the voltage across the resistor in series with the battery,and the sampling range of the voltage across the resistor is-0.1～0.1V,and the sampling error of the circuit is less than 20μV after calibration.The minimum resolution of the circuit is about 15 bits.The conversion time of the voltage and current sampling circuit is 15.6ms,and the total typical static power consumption is about 30μA.