BMS system battery total voltage acquisition precision calibration method

Abstract

The invention discloses a battery total voltage acquisition precision calibration method for a BMS (Battery Management System). Comprising the following steps: calibrating a hardware circuit, and calibrating software. The hardware circuit is composed of a resistance voltage divider, a relay A, a differential amplification circuit, a relay B, an ADC chip, a voltage reference and an MCU, the resistance voltage divider is connected with the relay A, the relay A is connected with the differential amplification circuit, the differential amplification circuit is connected with the relay B, the relay B is connected with the ADC chip, the voltage reference and the MCU, the ADC chip is connected with the MCU, and the MCU is connected with the relay A. Vos and a voltage reference error are calculated through switching of the front-stage relay set and the rear-stage relay set, the voltage acquisition precision can be rapidly and efficiently calibrated, and then the voltage acquisition precision is further improved through software calibration.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and particularly relates to a method for calibrating the acquisition accuracy of the total voltage of a BMS system battery. Background Art

[0003] At present, the BMS system can collect battery voltages from 0 to 1000V. Most manufacturers adopt a sampling scheme that converts large voltages into small voltage signals for acquisition through resistor voltage division. The small signals are conditioned by the pre-stage circuit and differentially amplified before entering the ADC for sampling and calculation. Currently, the overall acquisition scheme uses this circuit design. Although this scheme is technically mature and widely used, its disadvantage is that the accuracy error of the pre-stage voltage-dividing resistor is large, and the operational amplifier has offset voltage and bias current factors. The chip manufacturing process and temperature drift are uncontrollable factors, resulting in a certain error between the collected voltage value and the actual input voltage value. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for calibrating the acquisition accuracy of the total voltage of a BMS system battery, which can calculate Vos and voltage reference errors through the switching of the front and rear stage relay groups, quickly and efficiently calibrate the voltage acquisition accuracy, and then further improve the voltage acquisition accuracy through software calibration.

[0006] A method for calibrating the acquisition accuracy of the total voltage of a BMS system battery according to the present invention is characterized by including the following steps: 1) Calibrate the hardware circuit; Before collecting the voltage, the MCU first calibrates the hardware circuit, measures and calculates the offset voltage Vos of the operational amplifier and the voltage reference error Vr. The measurement of Vos and Vr requires the control and switching of the front and rear stage relay groups. First, the front stage relay group needs to be switched so that the input voltages Vin+ and Vin- of the differential amplification circuit are 0. At this moment, the output voltage of the differential amplification circuit is the offset voltage. Then, continue to control the rear stage relay group by the MCU to switch it to the direct connection of the differential amplification output to the ADC input, and at the same time disconnect the voltage provided by the voltage reference chip. Finally, the voltage value obtained by ADC conversion at this moment is Vos. Then, measure the actual voltage of the voltage reference source. By controlling the rear stage relay group by the MCU, the voltage output by the voltage reference is connected to the ADC for sampling, and at the same time disconnect the connection between the output end of the differential amplifier and the ADC input. Finally, the voltage value obtained by ADC conversion at this moment is Vr. After Vos and Vr are calculated, the acquisition circuit is restored to the normal state; 2) Software calibration; After hardware calibration, software calibration is still required. An adjustable power supply is externally connected, and several output voltages are set respectively. Then, Uad is sampled and calculated respectively. The voltage value output at that time is compared with the calculated value to obtain a difference. Finally, a design is made in the software to compensate and process the difference to obtain a calculated value with high accuracy.

[0007] The hardware circuit consists of a resistor divider, relay A, a differential amplifier circuit, relay B, an ADC chip, a voltage reference, and an MCU. The resistor divider is connected to relay A, relay A is connected to the differential amplifier circuit, the differential amplifier circuit is connected to relay B, relay B is respectively connected to the ADC chip, the voltage reference, and the MCU, the ADC chip is connected to the MCU, and the MCU is connected to relay A.

[0008] Compared with the prior art, the present invention has obvious beneficial effects. From the above technical solutions, it can be seen that in the present invention, the resistor divider is connected to relay A, relay A is connected to the differential amplifier circuit, the differential amplifier circuit is connected to relay B, relay B is respectively connected to the ADC chip, the voltage reference, and the MCU, the ADC chip is connected to the MCU, and the MCU is connected to relay A. The MCU first needs to calibrate the hardware circuit, measure and calculate the offset voltage Vos of the operational amplifier and the voltage reference error Vr. The measurement of Vos and Vr requires the control and switching of the front and rear stage relay groups. First, the front stage relay group needs to be switched so that the input voltages Vin+ and Vin- of the differential amplifier circuit are 0. At this moment, the output voltage of the differential amplifier circuit is the offset voltage. Then, the MCU continues to control the rear stage relay group to switch to the differential amplifier output directly connected to the ADC input, and at the same time disconnect the voltage provided by the voltage reference chip. Finally, the voltage value obtained by ADC conversion at this moment is Vos. Then, it is to measure the actual voltage of the voltage reference source. Through the MCU controlling the rear stage relay group, the voltage output by the voltage reference is connected to the ADC for sampling, and at the same time, the connection between the output end of the differential amplifier and the ADC input is disconnected. Finally, the voltage value obtained by ADC conversion at this moment is Vr. After Vos and Vr are calculated, the acquisition circuit is restored to the normal state. An adjustable power supply is externally connected, and several output voltages are set respectively. Then, Uad is sampled and calculated respectively. The voltage value output at that time is compared with the calculated value to obtain a difference. Finally, a design is made in the software to compensate and process the difference to obtain a calculated value with high accuracy. By switching the front and rear stage relay groups to calculate Vos and the voltage reference error, the voltage acquisition accuracy can be calibrated quickly and efficiently, and then the voltage acquisition accuracy is further improved through software calibration. Description of the Drawings

[0009] Figure 1 is the circuit diagram of the present invention. Detailed Embodiments

[0010] Embodiment 1: A method for calibrating the acquisition accuracy of the total voltage of a battery in a BMS system according to the present invention is characterized in that it includes the following steps: 1) Calibrate the hardware circuit; Before collecting the voltage, the MCU first calibrates the hardware circuit, measures and calculates the offset voltage Vos of the operational amplifier and the voltage reference error Vr. The measurement of Vos and Vr requires the control and switching of the front and rear stage relay groups. First, the front stage relay group needs to be switched so that the input voltages Vin+ and Vin- of the differential amplifier circuit are 0. At this moment, the output voltage of the differential amplifier circuit is the offset voltage. Then, continue to control the rear stage relay group by the MCU to switch it to the direct connection of the differential amplifier output to the ADC input, and at the same time disconnect the voltage provided by the voltage reference chip. Finally, the voltage value obtained by the ADC conversion at this moment is Vos. Then, measure the actual voltage of the voltage reference source. By controlling the rear stage relay group by the MCU, the voltage output by the voltage reference is connected to the ADC sampling, and at the same time, the connection between the output end of the differential amplifier and the ADC input is disconnected. Finally, the voltage value obtained by the ADC conversion at this moment is Vr. After Vos and Vr are calculated, the acquisition circuit is restored to the normal state. With a 3600-fold resistance voltage division, an 8-fold differential circuit amplification, and a 1V voltage reference voltage output, let the high voltage at the input end be Uin, and the voltage entering the ADC chip acquisition end be Uad. Then the voltage acquisition calculation formula is as follows: Uad = (Uin / 3600) * 8 - Vos + Vr Where Vos is the offset voltage. For the best operational amplifier circuit, Vos should be zero, and it actually needs to be calculated by the above calibration method. Vr is the actual output voltage of the voltage reference source. In the best case, it is 1V; 2) Software calibration; After the hardware calibration, software calibration is still required. An external adjustable power supply is provided, and the output voltages are set to 50V, 150V, 250V, 350V, 450V, 550V, 650V, 750V, 850V, and 950V respectively. Then, sample and calculate Uad respectively, compare the voltage value output in real time with the calculated value to obtain the difference, and finally design in the software to compensate and process the difference to obtain a highly accurate calculated value.

[0011] The hardware circuit is composed of a resistor voltage divider, relay A, differential amplifier circuit, relay B, ADC chip, voltage reference, and MCU. The resistor voltage divider is connected to relay A, relay A is connected to the differential amplifier circuit, the differential amplifier circuit is connected to relay B, relay B is respectively connected to the ADC chip, voltage reference, and MCU, the ADC chip is connected to the MCU, and the MCU is connected to relay A.

[0012] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for calibrating the acquisition accuracy of the total voltage of a battery in a BMS system, characterized in that; It includes the following steps: 1) Calibrate the hardware circuit; Before collecting the voltage, the MCU first needs to calibrate the hardware circuit, measure and calculate the offset voltage Vos of the operational amplifier and the voltage reference error Vr. The measurement of Vos and Vr requires the control and switching of the front and rear stage relay groups. First, the front stage relay group needs to be switched so that the input voltages Vin+ and Vin- of the differential amplifier circuit are 0. At this moment, the output voltage of the differential amplifier circuit is the offset voltage. Then, continue to control the rear stage relay group by the MCU to switch it to the differential amplifier output directly connected to the ADC input terminal, and at the same time disconnect the voltage provided by the voltage reference chip. Finally, the voltage value obtained by the ADC conversion at this moment is Vos. Then, measure the actual voltage of the voltage reference source. By controlling the rear stage relay group by the MCU, the voltage output by the voltage reference is connected to the ADC sampling, and at the same time disconnect the connection between the output terminal of the differential amplifier and the ADC input. Finally, the voltage value obtained by the ADC conversion at this moment is Vr. After Vos and Vr are calculated, the acquisition circuit is restored to the normal state; 2) Software calibration; After the hardware calibration, software calibration is still required. An external adjustable power supply is used, and several output voltages are set respectively. Then, Uad is sampled and calculated respectively. The difference is obtained by comparing the voltage value output in time with the calculated value. Finally, the difference compensation process is set in the software to obtain a calculated value with high accuracy.

2. The method for calibrating the acquisition accuracy of the total voltage of a battery in a BMS system according to claim 1, wherein; The hardware circuit consists of a resistor divider, relay A, differential amplifier circuit, relay B, ADC chip, voltage reference, and MCU. The resistor divider is connected to relay A, relay A is connected to the differential amplifier circuit, the differential amplifier circuit is connected to relay B, relay B is respectively connected to the ADC chip, voltage reference, and MCU, the ADC chip is connected to the MCU, and the MCU is connected to relay A.

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