A multi-cell battery management chip voltage sampling circuit with positive and negative voltage pretreatment structure of the battery

There are two problems with the traditional lithium battery voltage sampling circuit based on operational amplifier voltage conversion: First, the use of more high-voltage MOS transistor in the operational amplifier leads to the reduction of detection accuracy; Second, there is a current path from battery positive to the ground during voltage detection, and the detection current from the positive pole is also inconsistent. It leads to the imbalance of each battery after the end of the detection. This paper proposes a multi-cell battery-management-system voltage sampling circuit that uses the super source follower structure for battery positive voltage pretreatment and ordinary source follower for battery negative voltage pretreatment. The circuit ensures that the upper and lower voltage difference of the operational amplifier is within the low voltage range of a battery voltage and the input transistor gate-source voltage of the operational amplifier, which avoids the use of high-voltage MOS transisitor. At the same time, the detection current is provided by all series batteries, and there is no current outflow at the positive and negative, ensures balance of the battery. The simulation test is carried out under the conditions of 0.35umBCD process, ss, tt, ff process angle and temperature 27 °C, and the circuit function is normal. The positive and negative current of the battery is less than 1fA, and the voltage sampling max error is 1.4mV.