BMS system charging current acquisition device

Abstract

The utility model relates to the technical field of BMS systems, and particularly discloses a BMS system charging current acquisition device, which comprises a micro-control unit, a diverter, a relay group, a differential amplification circuit, a voltage reference module and an ADC sampling module, the micro-control unit is electrically connected with the relay group and the ADC sampling module; the relay group comprises a pre-stage relay group and a post-stage relay group, the pre-stage relay group is electrically connected between the output end of the shunt and the input end of the differential amplification circuit, and the post-stage relay group is electrically connected between the output end of the differential amplification circuit and the input end of the ADC sampling module; and the post-stage relay group is also electrically connected between the voltage reference module and the bias end of the differential amplification circuit. According to the scheme, the problem that an existing BMS system battery pack current acquisition circuit is poor in precision during current acquisition can be solved.

Description

Technical Field

[0001] This utility model relates to the field of BMS system technology, specifically to a BMS system charging current acquisition device. Background Technology

[0002] Currently, there are two main methods for collecting current from battery packs in BMS systems: Hall effect sensors and shunts. Hall effect sensors calculate the current passing through them using the Hall effect, converting large currents into smaller output currents. A shunt is essentially a fixed resistor; its principle is that current flowing through the resistor generates a voltage difference, which is then used to calculate the current magnitude. Both methods ultimately convert the current into a voltage signal for sampling and calculation.

[0003] Weak voltage signals are processed through signal conditioning and pre-amplification before entering the ADC for sampling and calculation. This circuit design is currently the standard for most data acquisition schemes. While this approach is technically mature and widely used, it also has some drawbacks. For example, because the operational amplifier circuit is not an ideal amplifier circuit, and factors such as chip manufacturing processes and temperature environments can cause offset voltage and zero-point drift in the amplifier circuit. Therefore, it suffers from poor accuracy in current acquisition. Utility Model Content

[0004] The present invention provides a charging current acquisition device for a BMS system to solve the problem of poor accuracy in current acquisition by existing BMS system battery pack current acquisition circuits.

[0005] To solve the above problems, the technical solution adopted by this utility model is as follows: A charging current acquisition device for a BMS system, including a microcontroller, and further including a shunt, a relay group, a differential amplifier circuit, a voltage reference module, and an ADC sampling module; the microcontroller is electrically connected to the relay group and the ADC sampling module;

[0006] The relay group includes a front-stage relay group and a rear-stage relay group. The front-stage relay group is electrically connected between the output of the shunt and the input of the differential amplifier circuit. The rear-stage relay group is electrically connected between the output of the differential amplifier circuit and the input of the ADC sampling module. The rear-stage relay group is also electrically connected between the voltage reference module and the bias terminal of the differential amplifier circuit.

[0007] The pre-stage relay group is used to control the voltage signal received at the input terminal of the differential amplifier circuit, the post-stage relay is used to control the voltage signal received at the input terminal of the ADC sampling module, and the post-stage relay is also used to control the on / off connection between the voltage reference module and the bias terminal of the differential amplifier circuit.

[0008] The basic principle of this scheme is as follows: When the operational amplifier circuit and voltage reference module have no offset voltage and temperature drift, the offset voltage Vos = 0 and the voltage reference error voltage Vr = 0. At this time, the acquisition accuracy is very ideal. However, actual operational amplifiers have offset voltage and temperature drift, so calibration is required. This scheme controls the input terminal of the differential amplifier circuit and the input terminal of the ADC sampling module by switching the state of the front and rear relays, so that the ADC sampling module can measure the actual values ​​of Vos and Vr under different states. By calibrating and compensating the charging current calculation formula, high-precision current measurement effect is achieved during current acquisition.

[0009] The beneficial effects of this solution are: by switching between the front and rear relay groups, the Vos and voltage reference error can be calculated, which can quickly and efficiently calibrate the current acquisition accuracy without manual intervention. The automatic calibration function can be achieved through MCU software control.

[0010] Furthermore, the shunt, relay group, differential amplifier circuit, microcontroller, voltage reference module, and ADC sampling module are all mounted on the same circuit board.

[0011] Furthermore, during the calibration of the acquisition accuracy, the microcontroller controls the front-stage relay group, which switches to make the voltages at the input terminals Vin+ and Vin- of the differential amplifier circuit zero. The microcontroller then controls the rear-stage relay group, which switches to make the output terminal of the differential amplifier circuit directly connected to the input terminal of the ADC sampling module. At the same time, the rear-stage relay group disconnects the voltage provided by the voltage reference module to the bias terminal of the differential amplifier circuit. The voltage value obtained by the ADC sampling module at this moment is Vos.

[0012] Furthermore, during the calibration of the acquisition accuracy, the microcontroller controls the subsequent relay group to connect the voltage output of the voltage reference module to the ADC sampling module. At the same time, the subsequent relay group disconnects the output of the differential amplifier circuit from the ADC input. Finally, the ADC sampling module converts the voltage value at this moment into Vr.

[0013] Furthermore, during charging current measurement, the microcontroller controls the switching of the front-stage relay group to connect the voltage at both ends of the shunt output to the two input terminals of the differential amplifier circuit, so that the input terminal of the differential amplifier circuit obtains a differential signal. The switching of the rear-stage relay group connects the voltage reference module to the bias terminal of the differential amplifier circuit, and the output of the differential amplifier circuit is connected to the sampling input terminal of the ADC.

[0014] The microcontroller is also used to obtain the current acquisition calculation formula based on Uad=(0.000375*I*20-Vos)+(2.5-Vr), where I is the current flowing through the shunt and Uad is the voltage entering the acquisition terminal of the ADC chip, thus obtaining the charging current I.

[0015] Furthermore, it also includes a display module, which is used to display the voltage value sampled by the ADC and the current value of the charging current. The display module is electrically connected to the ADC sampling module and the microcontroller unit.

[0016] Furthermore, it also includes a storage unit, which stores current and voltage values ​​and is electrically connected to the ADC sampling module and the microcontroller unit.

[0017] Furthermore, the shunt is used to convert the current into a voltage signal with a voltage range of -75mV to +75mV. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an embodiment of the present utility model. Detailed Implementation

[0019] The following detailed description illustrates the specific implementation method:

[0020] The basic implementation examples are as follows: Figure 1 As shown:

[0021] A charging current acquisition device for a BMS system includes a microcontroller unit and at least two relay groups electrically connected to the microcontroller unit. The relay groups include a pre-stage relay group and a post-stage relay group. The input terminal of the pre-stage relay group is electrically connected to a shunt, and the output terminal of the pre-stage relay group is electrically connected to a differential amplifier circuit. The input terminal of the post-stage relay group is also electrically connected to a differential amplifier circuit. The input terminal of the post-stage relay group is also electrically connected to a voltage reference module, and the output terminal of the post-stage relay group is electrically connected to an ADC sampling module. The output terminal of the ADC sampling module is electrically connected to the microcontroller unit.

[0022] The shunt is used to convert current into a voltage signal; in this embodiment, the voltage range is -75mV to +75mV, and the voltage signal is a differential signal.

[0023] The pre-stage relay group is used to switch between the differential signal output by the shunt and the differential calibration circuit signal for calibration. The differential calibration circuit signal keeps the input terminals Vin+ and Vin- of the differential amplifier circuit at 0 voltage input. At this time, the output voltage value of the differential amplifier circuit is Vos, where Vos refers to the offset voltage.

[0024] A differential amplifier circuit is used to amplify the difference between two input signals, Vin+ and Vin-, i.e., the differential signal. This amplification method allows weak input signals to be amplified to the required level, and the appropriate voltage amplification factor is designed according to the actual application.

[0025] The voltage reference module provides a bias voltage to the bias terminal of the differential amplifier circuit. The voltage reference module is electrically connected to the bias terminal of the differential amplifier circuit, and a subsequent relay group is electrically connected between the voltage reference module and the bias terminal of the differential amplifier circuit.

[0026] The subsequent relay group is used to control the signal obtained by the ADC sampling module and also to control the on / off connection between the voltage reference module and the bias terminal of the differential amplifier circuit. Specifically, during calibration, the signal obtained by the ADC sampling module switches between the amplified output voltage Vos and the voltage reference error voltage Vr; and the subsequent relay group ensures that the ADC sampling module is not simultaneously connected to the voltage reference module and the output terminal of the differential amplifier circuit. During normal use of the current acquisition circuit, the subsequent relay group connects the voltage reference module to the bias terminal of the differential amplifier circuit.

[0027] It also includes a display module, which is used to display the voltage value sampled by the ADC and the current value of the charging current. The display module is electrically connected to the ADC sampling module and the microcontroller unit.

[0028] It also includes a storage unit, which stores current and voltage values ​​and is electrically connected to the ADC sampling module and the microcontroller unit.

[0029] The specific implementation process is as follows:

[0030] Before the MCU starts the current acquisition function, the current acquisition accuracy must first be calibrated by measuring and calculating Vos and the voltage reference error voltage Vr. The measurement of Vos and Vr requires the control switching of the upstream and downstream relay groups.

[0031] Vos measurement: First, the microcontroller unit controls the front-stage relay group to switch the voltage at the input terminals Vin+ and Vin- of the differential amplifier circuit to 0. Then, the MCU controls the rear-stage relay group, switching it so that the output of the differential amplifier circuit is directly connected to the input of the ADC. Simultaneously, the rear-stage relay group disconnects the voltage provided by the voltage reference chip to the bias terminal of the differential amplifier circuit. The voltage value obtained by the ADC sampling module at this moment is Vos.

[0032] Next, the Vr value is measured: the microcontroller controls the subsequent relay group to connect the voltage output of the voltage reference module to the ADC sampling module. At the same time, the subsequent relay group disconnects the output of the differential amplifier circuit from the ADC input. Finally, the ADC sampling module converts the voltage value at this moment into Vr.

[0033] After the calibration function is completed, the charging current of the BMS system can be collected. The microcontroller controls the switching of the front-stage relay group to connect the voltage at both ends of the shunt output to the two input terminals of the differential amplifier circuit. The differential amplifier circuit obtains a differential signal at its input terminal. The subsequent relay group switches to connect the voltage reference module to the bias terminal of the differential amplifier circuit. The output of the differential amplifier circuit is connected to the sampling input terminal of the ADC.

[0034] Taking a 200A / 75mV shunt, with a differential circuit amplification of 20 times and a voltage reference output of 2.5V as an example,

[0035] Let the current flowing through the shunt be I, and the voltage entering the ADC chip's acquisition terminal be Uad. Then the current acquisition calculation formula is as follows:

[0036] Uad=(0.000375*I*20-Vos)+(2.5-Vr)

[0037] Where 0.000375 is the resistance value of the shunt, and 2.5 is the input bias voltage of the differential amplifier. When the differential amplifier and voltage reference have no offset voltage or temperature drift, Vos = 0 and Vr = 0, and the acquisition accuracy is very ideal. In the ideal state, Uad = (0.000375 * I * 20) + (2.5), and the charging current value can be directly obtained by reading the ADC chip. However, actual operational amplifiers have offset voltage and temperature drift, so calibration is required. In this embodiment, by setting the front-stage relay group and the rear-stage relay group, the actual values ​​of Vos and Vr are calculated according to the above method, and then the charging current value is calibrated and compensated by the formula to achieve a high-precision current measurement effect.

[0038] The above descriptions are merely embodiments of this utility model, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of this utility model, and these should also be considered within the scope of protection of this utility model. These modifications will not affect the effectiveness of the implementation of this utility model or the practicality of the patent. The scope of protection claimed in this application shall be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A charging current acquisition device for a BMS system, comprising a microcontroller unit, characterized in that: It also includes a shunt, relay group, differential amplifier circuit, voltage reference module, and ADC sampling module; the microcontroller unit is electrically connected to the relay group and ADC sampling module; The relay group includes a front-stage relay group and a rear-stage relay group. The front-stage relay group is electrically connected between the output of the shunt and the input of the differential amplifier circuit. The rear-stage relay group is electrically connected between the output of the differential amplifier circuit and the input of the ADC sampling module. The rear-stage relay group is also electrically connected between the voltage reference module and the bias terminal of the differential amplifier circuit. The pre-stage relay group is used to control the voltage signal received at the input terminal of the differential amplifier circuit, the post-stage relay is used to control the voltage signal received at the input terminal of the ADC sampling module, and the post-stage relay is also used to control the on / off connection between the voltage reference module and the bias terminal of the differential amplifier circuit.

2. The BMS system charging current acquisition device according to claim 1, characterized in that: The shunt, relay group, differential amplifier circuit, microcontroller, voltage reference module, and ADC sampling module are all mounted on the same circuit board.

3. The BMS system charging current acquisition device according to claim 2, characterized in that: During the calibration of acquisition accuracy, the microcontroller controls the front-stage relay group, which switches to make the input voltages Vin+ and Vin- of the differential amplifier circuit zero. The microcontroller then controls the rear-stage relay group, which switches to make the output of the differential amplifier circuit directly connected to the input of the ADC sampling module. At the same time, the rear-stage relay group disconnects the voltage provided by the voltage reference module to the bias terminal of the differential amplifier circuit. The voltage value obtained by the ADC sampling module at this moment is Vos.

4. The BMS system charging current acquisition device according to claim 3, characterized in that: When calibrating the acquisition accuracy, the microcontroller controls the subsequent relay group to connect the voltage output of the voltage reference module to the ADC sampling module. At the same time, the subsequent relay group disconnects the output of the differential amplifier circuit from the ADC input. Finally, the ADC sampling module converts the voltage value at this moment into Vr.

5. A BMS system charging current acquisition device according to claim 4, characterized in that: When measuring charging current, the microcontroller controls the switching of the front-stage relay group, so that the voltage at both ends of the shunt output is connected to the two input terminals of the differential amplifier circuit, and the differential amplifier circuit input terminal obtains a differential signal. The switching of the rear-stage relay group connects the voltage reference module to the bias terminal of the differential amplifier circuit, and the output of the differential amplifier circuit is connected to the sampling input terminal of the ADC. The microcontroller is also used to obtain the current acquisition calculation formula based on Uad=(0.000375*I*20-Vos)+(2.5-Vr), where I is the current flowing through the shunt and Uad is the voltage entering the acquisition terminal of the ADC chip, thus obtaining the charging current I.

6. The BMS system charging current acquisition device according to claim 5, characterized in that: It also includes a display module, which is used to display the voltage value sampled by the ADC and the current value of the charging current. The display module is electrically connected to the ADC sampling module and the microcontroller unit.

7. A BMS system charging current acquisition device according to claim 6, characterized in that: It also includes a storage unit, which stores current and voltage values ​​and is electrically connected to the ADC sampling module and the microcontroller unit.

8. A BMS system charging current acquisition device according to claim 7, characterized in that: The shunt is used to convert current into a voltage signal with a voltage range of -75mV to +75mV.

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