A Resistance-Based Micro-Current Acquisition Circuit and Method

Abstract

The present invention provides a micro-current acquisition circuit and method based on resistance in the technical field of lithium battery pack protection board testing. The circuit includes a micro-control unit U1, an analog-to-digital conversion chip U2, a current acquisition module, a single-pole double-throw switch K1, a constant current source V, and a wiring terminal J1. One end of the analog-to-digital conversion chip U2 is connected to the micro-control unit U1, and the other end is connected to the current acquisition module. The pins 1, 2, and 3 of the single-pole double-throw switch K1 are respectively connected to the constant current source V, the wiring terminal J1, and the current acquisition module. The advantages of the present invention are as follows: greatly improving the accuracy of micro-current acquisition.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery pack protection board testing, and particularly to a micro-current acquisition circuit and method based on a resistor. Background Art

[0002] After the production of a lithium battery pack, it is necessary to use a testing device to test its protection board. With the progress of technology, the testing device for the protection board is also developing towards being more convenient and miniaturized. Since a large number of protection boards need to be tested, it is inevitable to frequently charge the testing device.

[0003] In order to extend the usage time of the testing device, there are two methods: increasing the battery capacity of the testing device and reducing the power consumption. Increasing the battery capacity undoubtedly goes against the development direction of being convenient and miniaturized. Therefore, the method of reducing power consumption is generally adopted.

[0004] Reducing power consumption means reducing the working current, static current, sleep current, and power-down current. In order to better reduce power consumption, it is first necessary to accurately collect the current. For current collection, the following traditional method is adopted: when the current flows through the sampling resistor Rs, the sampling voltage across the sampling resistor Rs is collected, and the corresponding current is calculated based on the sampling voltage and the resistance value of the sampling resistor Rs.

[0005] Since the resistance value of the sampling resistor Rs in actual use is affected by factors such as temperature, humidity, dust, and vibration, according to Ohm's law, when the resistance value of the sampling resistor Rs changes, the calculated current value will also deviate, directly affecting the accuracy of current collection.

[0006] Therefore, how to provide a micro-current acquisition circuit and method based on a resistor to improve the accuracy of micro-current acquisition has become an urgent technical problem to be solved. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a micro-current acquisition circuit and method based on a resistor to improve the accuracy of micro-current acquisition.

[0008] In a first aspect, the present invention provides a micro-current acquisition circuit based on a resistor, including a microcontroller unit U1, an analog-to-digital conversion chip U2, a current acquisition module, a single-pole double-throw switch K1, a constant current source V, and a terminal block J1;

[0009] One end of the analog-to-digital conversion chip U2 is connected to the microcontroller unit U1, and the other end is connected to the current acquisition module; the pins 1, 2, and 3 of the single-pole double-throw switch K1 are respectively connected to the constant current source V, the terminal block J1, and the current acquisition module.

[0010] Further, the current acquisition module includes an operational amplifier U3 and a sampling resistor Rs;

[0011] Pin 1 of the operational amplifier U3 is connected to the resistor Rs and the analog-to-digital conversion chip U2, pin 2 is connected to the resistor Rs and pin 3 of the single-pole double-throw switch K1, and pin 3 is grounded.

[0012] Further, the control end of the single-pole double-throw switch K1 is connected to the micro-control unit U1.

[0013] In a second aspect, the present invention provides a micro-current acquisition method based on a resistor, including the following steps:

[0014] Step S10: The micro-control unit U1 controls the constant current source V to input a current I_cc, and the analog-to-digital conversion chip U2 acquires the voltage Vo1 output by the current acquisition module;

[0015] Step S20: The micro-control unit U1 calculates the actual resistance value Rs1 of the sampling resistor Rs based on the I_cc and Vo1;

[0016] Step S30: The micro-control unit U1 controls the wiring terminal J1 to input a current I_in, and the analog-to-digital conversion chip U2 acquires the voltage Vo2 output by the current acquisition module;

[0017] Step S40: The micro-control unit U1 calculates the current value of the current I_in based on the Rs1 and Vo2.

[0018] Further, the specific content of step S10 is as follows:

[0019] The micro-control unit U1 controls pins 1 and 3 of the single-pole double-throw switch K1 to conduct, so as to connect the constant current source V, and the current I_cc output by the constant current source V is input into the current acquisition module through the single-pole double-throw switch K1. The analog-to-digital conversion chip U2 performs analog-to-digital conversion on the voltage output by the current acquisition module to obtain the voltage Vo1, and transmits the voltage Vo1 to the micro-control unit U1.

[0020] Further, in step S20, the calculation formula for the actual resistance value Rs1 is:

[0021] Rs1 = Vo1 / I_cc.

[0022] Further, the specific content of step S30 is as follows:

[0023] The microcontroller unit U1 controls the pins 2 and 3 of the single-pole double-throw switch K1 to conduct, so as to access the current I_in to be measured through the terminal block J1. The current I_in is input into the current acquisition module through the single-pole double-throw switch K1. The analog-to-digital conversion chip U2 performs analog-to-digital conversion on the voltage output by the current acquisition module to obtain the voltage Vo2, and transmits the voltage Vo2 to the microcontroller unit U1.

[0024] Further, in the step S40, the calculation formula for the current value of the current I_in is:

[0025] I_in = Vo2 / Rs1.

[0026] The advantages of the present invention are as follows:

[0027] By setting the single-pole double-throw switch K1 and the constant current source V, the microcontroller unit U1 first accesses the constant current source V to input the current I_cc through the single-pole double-throw switch K1, and collects the voltage Vo1 output by the current acquisition module through the analog-to-digital conversion chip U2 to calculate the actual resistance value Rs1 of the sampling resistor Rs; then accesses the current I_in to be measured through the single-pole double-throw switch K1 and the terminal block J1, and collects the voltage Vo2 output by the current acquisition module through the analog-to-digital conversion chip U2. Finally, based on the actual resistance value Rs1 and the voltage Vo2, the current value of the current I_in is calculated, rather than using the initially calibrated Rs for calculation, which overcomes the problem that the resistance value of the sampling resistor Rs changes due to environmental factors, and ultimately greatly improves the accuracy of microcurrent acquisition. Description of the Drawings

[0028] The present invention will be further described below with reference to the drawings in conjunction with embodiments.

[0029] Figure 1 is the circuit diagram of a microcurrent acquisition circuit based on resistance according to the present invention.

[0030] Figure 2 is the flowchart of a microcurrent acquisition method based on resistance according to the present invention. Detailed Embodiments

[0031] The overall idea of the technical solution in the embodiment of the present application is as follows: input the current I_cc through the constant current source V, collect the voltage Vo1 output by the current acquisition module, calculate the actual resistance value Rs1 of the sampling resistor Rs by using I_cc and Vo1, then collect the voltage Vo2 output by the current acquisition module when the current I_in is input, and calculate the current value of the current I_in by using Rs1 and Vo2, that is, use the actual resistance value Rs1 of the sampling resistor Rs after recalibration for calculation to improve the accuracy of microcurrent acquisition.

[0032] Please refer to Figures 1 to 2As shown in the figure, a preferred embodiment of a micro-current acquisition circuit based on resistance according to the present invention includes a micro-control unit (MCU) U1, an analog-to-digital conversion chip (A / D chip) U2, a current acquisition module, a single-pole double-throw switch K1, a constant current source V, and a wiring terminal J1;

[0033] The micro-control unit U1 is used to control the on / off of the single-pole double-throw switch K1, receive the voltage signal output by the analog-to-digital conversion chip U2, and calculate the actual resistance value Rs1 of the sampling resistor Rs and the current value of the current I_in. In specific implementation, any micro-control unit that can achieve this function can be selected from the prior art, and it is not limited to any model. For example, the MCU of the STM32F103 series of ST Company, and the control program is well-known to those skilled in the art, which can be obtained by those skilled in the art without creative labor; the analog-to-digital conversion chip U2 is used to perform analog-to-digital conversion on the voltage signal output by the current acquisition module. In specific implementation, any analog-to-digital conversion chip that can achieve this function can be selected from the prior art, and it is not limited to any model. For example, AD9280, which can be obtained by those skilled in the art without creative labor; the current acquisition module is used to amplify and acquire the input current; the single-pole double-throw switch K1 is used to switch whether the input is I_cc or I_in; the constant current source V is used to output a high-precision and fixed current I_cc.

[0034] One end of the analog-to-digital conversion chip U2 is connected to the micro-control unit U1, and the other end is connected to the current acquisition module; the pins 1, 2, and 3 of the single-pole double-throw switch K1 are respectively connected to the constant current source V, the wiring terminal J1, and the current acquisition module.

[0035] The current acquisition module includes an operational amplifier U3 and a sampling resistor Rs; the operational amplifier U3 is used to amplify the input current. In specific implementation, any operational amplifier that can achieve this function can be selected from the prior art, and it is not limited to any model. For example, TL082, which can be obtained by those skilled in the art without creative labor;

[0036] The pin 1 of the operational amplifier U3 is connected to the resistor Rs and the analog-to-digital conversion chip U2, the pin 2 is connected to the resistor Rs and the pin 3 of the single-pole double-throw switch K1, and the pin 3 is grounded.

[0037] The control end of the single-pole double-throw switch K1 is connected to the micro-control unit U1, and can conduct pins 1, 3 or 2, 3 as required, and the current to be measured is input from pin 2.

[0038] A preferred embodiment of a micro-current acquisition method based on resistance according to the present invention includes the following steps:

[0039] Step S10: The microcontroller unit U1 controls the constant current source V to input current I_cc, and the analog-to-digital conversion chip U2 collects the voltage Vo1 output by the current acquisition module; the current value of the current I_cc is known;

[0040] Step S20: The microcontroller unit U1 calculates the actual resistance value Rs1 of the sampling resistor Rs based on the I_cc and Vo1; that is, the resistance value of the sampling resistor Rs is recalibrated by the high-precision constant current source V to improve the current acquisition accuracy;

[0041] Step S30: The microcontroller unit U1 controls the connection terminal J1 to input current I_in, and the analog-to-digital conversion chip U2 collects the voltage Vo2 output by the current acquisition module; the current value of the current I_in is unknown and is the current value to be measured;

[0042] Step S40: The microcontroller unit U1 calculates the current value of the current I_in based on the Rs1 and Vo2.

[0043] During specific implementation, the voltage Vo1 and the voltage Vo2 can be collected simultaneously at time T to ensure the current acquisition accuracy.

[0044] The specific content of step S10 is as follows:

[0045] The microcontroller unit U1 controls the pins 1 and 3 of the single-pole double-throw switch K1 to conduct, so as to connect the constant current source V, and let the current I_cc output by the constant current source V input the current acquisition module through the single-pole double-throw switch K1. The analog-to-digital conversion chip U2 performs analog-to-digital conversion on the voltage output by the current acquisition module to obtain the voltage Vo1, and transmits the voltage Vo1 to the microcontroller unit U1.

[0046] In step S20, the calculation formula for the actual resistance value Rs1 is:

[0047] Rs1 = Vo1 / I_cc.

[0048] The specific content of step S30 is as follows:

[0049] The microcontroller unit U1 controls the pins 2 and 3 of the single-pole double-throw switch K1 to conduct, so as to connect the current I_in to be measured through the connection terminal J1. The current I_in inputs the current acquisition module through the single-pole double-throw switch K1. The analog-to-digital conversion chip U2 performs analog-to-digital conversion on the voltage output by the current acquisition module to obtain the voltage Vo2, and transmits the voltage Vo2 to the microcontroller unit U1.

[0050] In step S40, the calculation formula for the current value of the current I_in is:

[0051] I_in = Vo2 / Rs1.

[0052] In summary, the advantages of the present invention are as follows:

[0053] By setting the single-pole double-throw switch K1 and the constant current source V, the microcontroller unit U1 first accesses the input current I_cc of the constant current source V through the single-pole double-throw switch K1, and collects the voltage Vo1 output by the current acquisition module through the analog-to-digital conversion chip U2 to calculate the actual resistance value Rs1 of the sampling resistor Rs; then accesses the current I_in to be measured through the single-pole double-throw switch K1 and the terminal block J1, collects the voltage Vo2 output by the current acquisition module through the analog-to-digital conversion chip U2, and finally calculates the current value of the current I_in based on the actual resistance value Rs1 and the voltage Vo2, rather than calculating using the initially calibrated Rs, thus overcoming the problem that the resistance value of the sampling resistor Rs changes due to environmental factors, and ultimately greatly improving the accuracy of micro-current acquisition.

[0054] Although the specific implementation manners of the present invention have been described above, those skilled in the art should understand that the specific embodiments we described are illustrative rather than used to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered by the scope protected by the claims of the present invention.

Claims

1. A micro-current acquisition circuit based on resistance, characterized in that: It includes a microcontroller unit U1, an analog-to-digital conversion chip U2, a current acquisition module, a single-pole double-throw switch K1, a constant current source V, and a terminal block J1; One end of the analog-to-digital conversion chip U2 is connected to the microcontroller unit U1, and the other end is connected to the current acquisition module; Pins 1, 2, and 3 of the single-pole double-throw switch K1 are respectively connected to the constant current source V, the terminal block J1, and the current acquisition module; The current acquisition module includes an operational amplifier U3 and a sampling resistor Rs; Pin 1 of the operational amplifier U3 is connected to the resistor Rs and the analog-to-digital conversion chip U2, pin 2 is connected to the resistor Rs and pin 3 of the single-pole double-throw switch K1, and pin 3 is grounded.

2. The micro-current acquisition circuit based on resistance according to claim 1, characterized in that: The control end of the single-pole double-throw switch K1 is connected to the microcontroller unit U1.

3. A micro-current acquisition method based on resistance, characterized in that: The method needs to use the acquisition circuit as described in any one of claims 1 to 2, and includes the following steps: Step S10: The microcontroller unit U1 controls the constant current source V to input a current I_cc, and acquires the voltage Vo1 output by the current acquisition module through the analog-to-digital conversion chip U2; Step S20: The microcontroller unit U1 calculates the actual resistance value Rs1 of the sampling resistor Rs based on the I_cc and Vo1; Step S30: The microcontroller unit U1 controls the terminal block J1 to input a current I_in, and acquires the voltage Vo2 output by the current acquisition module through the analog-to-digital conversion chip U2; Step S40: The microcontroller unit U1 calculates the current value of the current I_in based on the Rs1 and Vo2.

4. The micro-current acquisition method based on resistance according to claim 3, characterized in that: The specific content of step S10 is: The microcontroller unit U1 controls pins 1 and 3 of the single-pole double-throw switch K1 to conduct, so as to connect the constant current source V. Let the current I_cc output by the constant current source V input the current acquisition module through the single-pole double-throw switch K1. The analog-to-digital conversion chip U2 performs analog-to-digital conversion on the voltage output by the current acquisition module to obtain the voltage Vo1, and transmits the voltage Vo1 to the microcontroller unit U1.

5. The micro-current acquisition method based on resistance according to claim 3, characterized in that: In step S20, the calculation formula for the actual resistance value Rs1 is: Rs1 = Vo1 / I_cc.

6. The micro-current acquisition method based on resistance according to claim 3, characterized in that: The specific content of step S30 is: The microcontroller unit U1 controls pins 2 and 3 of the single-pole double-throw switch K1 to conduct, so as to connect the current I_in to be measured through the terminal block J1. The current I_in inputs the current acquisition module through the single-pole double-throw switch K1. The analog-to-digital conversion chip U2 performs analog-to-digital conversion on the voltage output by the current acquisition module to obtain the voltage Vo2, and transmits the voltage Vo2 to the microcontroller unit U1.

7. The micro-current acquisition method based on resistance according to claim 3, characterized in that: In step S40, the calculation formula for the current value of the current I_in is: I_in = Vo2 / Rs1.

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