A large-range low-difference-voltage current measurement circuit

Abstract

This invention belongs to the field of circuit measurement technology and discloses a large-range, low-dropout current measurement circuit, including: a microprocessor, a sampling resistor R0, an output amplifier U7, and multiple parallel shunt circuits. Each shunt circuit includes a sampling resistor, an output amplifier, an automatic shunt adjustment module, and a shunt gate. One end of the sampling resistor R0 is connected to the current input terminal, and the other end is connected to the input terminal of the output amplifier. In each shunt circuit, the two input terminals of the automatic shunt adjustment module are respectively connected to the current input terminal and a comparison voltage, and its output terminal is connected to the control terminal of the shunt gate. One end of the shunt gate is connected to the current input terminal, and the other end is connected to one end of the sampling resistor, the other end of which is grounded. One end of the sampling resistor is connected to the input terminal of the output amplifier. The output terminal of the output amplifier is connected to the microprocessor. This invention can meet the requirements for high-speed, large-range current measurement.

Description

Technical Field

[0001] This invention relates to the field of current measurement technology, and in particular to a large-range, low-difference-voltage current detection circuit and its measurement method. Background Technology

[0002] With technological advancements, the power consumption of electronic devices is decreasing. In low-power operation, power consumption might be in the nanoampere range, while in high-power operation, the current could be in the ampere range. Measuring such currents requires wide-range analog-to-digital converters (ADCs), such as a 30-bit ADC to achieve current measurement across the nA to A range. Currently, there are no ADCs with such high bit depths available on the market. Moreover, as the number of bits in the ADC conversion result increases, the conversion time also increases. Therefore, it is impossible to achieve high-speed sampling of a large range of currents using a single sampling resistor. Furthermore, in the detection of certain sensor physical quantities, where current variations are large, there is also a need for high-precision measurement of large-range currents.

[0003] Current resistor switching solutions rely on the processor to switch the sampling resistor via a pin when the measurement result exceeds the range. This method requires precise processor execution, making rapid switching impossible. Furthermore, if the current changes drastically, much of the acquired data is invalid and fails to reflect the true current change. Additionally, multiple switches and resistors are connected in parallel; the more sampling resistor stages there are, the more corresponding switch stages there are, resulting in a larger sampling voltage drop, which is unsuitable for applications with strict requirements on sampling voltage drop. Summary of the Invention

[0004] To meet the practical needs of the field of current measurement technology, this invention overcomes the shortcomings of the existing technology. The technical problem to be solved is to provide a large-range, low-difference-voltage current detection circuit to improve the range and accuracy of current measurement.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a large-range low-dropout current measurement circuit, including a sampling resistor R0, one end of which is connected to the current input terminal and the other end of which is connected to the current output terminal; it also includes: a microprocessor and multiple parallel shunt circuits, each shunt circuit including a sampling resistor, an automatic shunt adjustment module and a shunt gate, the sampling resistors in each shunt circuit are divided into R1 to RN, where N represents the number of shunt circuits, and the resistance values ​​of each shunt resistor satisfy the condition: R0 > R1 > ... > Rn > ... > RN; the output terminal of the output amplifier is connected to the microprocessor;

[0006] In each shunt circuit, one input terminal of the automatic shunt adjustment module is connected to the current input terminal, the other input terminal is connected to the comparison voltage, and its output terminal is connected to the control terminal of the shunt gate. One end of the shunt gate is connected to the current input terminal, and the other end is connected to one end of the sampling resistor. The other end of the sampling resistor is connected to the current output terminal.

[0007] One end of each sampling resistor is connected to the input terminal of the microprocessor;

[0008] The microprocessor is used to determine the state of each shunt gate based on the output voltage of each sampling resistor, and then calculate the current value to be measured.

[0009] The comparison voltage connected to the automatic current shunt adjustment module corresponding to the sampling resistor Rn is less than the comparison voltage connected to the automatic current shunt adjustment module corresponding to the sampling resistor Rn+1.

[0010] Furthermore, the sampling resistor satisfies the following condition:

[0011] R n / R n+1 =Y, n=0……N;

[0012] Where Y represents a proportionality constant greater than 1, R n and R n+1 These represent the resistance values ​​of sampling resistor Rn and sampling resistor Rn+1, respectively.

[0013] Furthermore, the value of Y is 10.

[0014] Furthermore, the large-range low-dropout current measurement circuit further includes an analog-to-digital converter and N+1 output amplifiers. One end of each sampling resistor is connected to one of the output amplifiers. The analog-to-digital converter is used to convert the output voltage of each output amplifier into an analog-to-digital value and then send it to the microprocessor.

[0015] Furthermore, all output amplifiers have the same amplification factor.

[0016] Furthermore, in each shunt circuit, the shunt gate includes one or more field-effect transistors, whose gates are connected to the output terminal of the corresponding automatic shunt adjustment module.

[0017] Furthermore, the automatic shunt adjustment module is an operational amplifier.

[0018] Furthermore, the specific steps by which the microprocessor determines the state of each shunt gate based on the output voltage of the analog-to-digital converter, and then calculates the current value, are as follows:

[0019] S1. Determine whether the output voltage V0 corresponding to the sampling resistor R0 is less than Vth*T. If yes, then the current to be measured I = V0 / X / R0. If no, proceed to step S2. T represents the safety factor.

[0020] S2. Determine whether the output voltage V1 corresponding to the sampling resistor R1 is less than Vth*T. If yes, the current to be measured i = (V0 / R0 + V1 / R1) / X. If no, proceed to step S3.

[0021] S3. Determine whether the output voltage V2 corresponding to the sampling resistor R2 is less than Vth*T. If yes, then the current to be measured I = (V0 / R0 + V1 / R1 + V2 / R2) / X; if no, proceed to step S4.

[0022] ...

[0023] Sn, determine whether the output voltage Vn corresponding to the sampling resistor Rn is less than vth*T. If so, then the current to be measured... Where n = 0 ... N.

[0024] The non-inverting input of the output amplifier is connected to the current input of the corresponding sampling resistor, the inverting input is grounded through a resistor, and a feedback resistor is connected between the output and the inverting input.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] This invention provides a large-range, low-dropout current detection circuit. It employs a simple automated circuit for high-speed automatic switching of the sampling resistor, and the overall sampling voltage drop of the measurement circuit is controllable. It can meet the measurement requirements of high-speed, large-range current, and the sampling backend does not need to be changed. It can be widely used in various current fields and has the advantages of low cost, high reliability, and wide application. Attached Figure Description

[0027] Figure 1 This is a circuit structure block diagram of a large-range low-difference-voltage current detection circuit provided in Embodiment 1 of the present invention;

[0028] Figure 2 This is a circuit diagram of a large-range low-difference-voltage current detection circuit provided in Embodiment 1 of the present invention;

[0029] Figure 3 This is a circuit diagram of a large-range low-difference-voltage current detection circuit provided in Embodiment 2 of the present invention;

[0030] Figure 4 This is a circuit diagram of a large-range low-difference-voltage current detection circuit provided in Embodiment 3 of the present invention.

[0031] Specific implementation methods

[0032] To make the technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments and accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments; based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] like Figure 1 As shown, Embodiment 1 of the present invention provides a large-range low-difference-voltage current measurement circuit including: a microprocessor, a sampling resistor R0, an output amplifier U7, and three parallel shunt circuits. Each shunt circuit includes a sampling resistor, an output amplifier, an automatic shunt adjustment module, and a shunt gate. The sampling resistors in each shunt circuit are divided into R1 to R3. One end of the sampling resistor R0 is connected to the current input terminal and the input terminal of the output amplifier U7. The output terminal of the output amplifier U7 is connected to the microprocessor. In each shunt circuit, one input terminal of the automatic shunt adjustment module is connected to the current input terminal, and the other input terminal is connected to the comparison voltage. Its output terminal is connected to the control terminal of the shunt gate. One end of the shunt gate is connected to the current input terminal, and the other end is connected to one end of the sampling resistor. The other end of the sampling resistor is connected to the current output terminal (grounded). One end of the sampling resistor is connected to the input terminal of the output amplifier, and the output terminals of each output amplifier are connected to the microprocessor. The microprocessor is used to determine the state of each shunt gate based on the output voltage of each output amplifier, and then calculate the current value to be measured. The resistance values ​​of the sampling resistors must satisfy the following condition: R0 > R1 > R2 > R3.

[0035] Specifically, in this embodiment, an analog-to-digital converter M1 is further provided between the output amplifier and the microprocessor to convert the analog signals output by each output amplifier into digital signals and then send them to the microprocessor. Furthermore, in this embodiment, preferably, each output amplifier has the same amplification factor.

[0036] Specifically, in this embodiment, the sampling resistor satisfies the following condition:

[0037] R n / R n+1 =Y, n=0,1,2;

[0038] Where Y represents a proportionality constant greater than 1, R n and R n+1 These represent the resistance values ​​of sampling resistor Rn and sampling resistor Rn+1, respectively. Preferably, the value of Y is 10, so this embodiment can realize the measurement of four range currents with a range ratio of 10.

[0039] Specifically, such as Figure 2 The diagram shown is a circuit schematic of an embodiment of the present invention. In each shunt circuit, the sampling resistor R1 corresponds to output amplifier U1, with corresponding automatic shunt adjustment modules of operational amplifier U2 and shunt gates of field-effect transistor Q1. The sampling resistor R2 corresponds to output amplifier U3, with corresponding automatic shunt adjustment modules of operational amplifier U4 and shunt gates of field-effect transistor Q2. The sampling resistor R3 corresponds to output amplifier U5, with corresponding automatic shunt adjustment modules of operational amplifier U6 and shunt gates of field-effect transistors Q3 and Q4. The three terminals of field-effect transistors Q3 and Q4 are connected in parallel. The shunt gate corresponding to sampling resistor R3 schematically uses two PMOS transistors because when the current is large, the MOS transistors also have internal resistance, generating a voltage drop when current flows. Therefore, parallel connection of MOS transistors can reduce the sampling voltage drop of this circuit under high current conditions.

[0040] Specifically, the working principle of this embodiment is as follows: The maximum sampling voltage drop of the entire circuit is set to Vth. This sampling voltage drop can be generated by a specific voltage divider circuit and input to the operational amplifiers corresponding to each automatic shunt adjustment module. The resistance values ​​of sampling resistors R0, R1, R2, and R3 decrease sequentially, and their resistance values ​​have the following relationship: R0 / R1 = R1 / R2 = R2 / R3 = Y, where Y is a number greater than 1. The amplification factor of output amplifiers U1, U3, U5, and U7 is uniformly set to X, ensuring that Vth*X is not greater than the maximum input voltage of the analog-to-digital converter (ADC). Additionally, a safety factor T needs to be set, which can be set to 0.8. The current value to be detected can be calculated using the following judgment method: Following the order of sampling resistors from largest to smallest, the voltage value Vn (n is the resistor number, starting from 0) on the sampling resistors is read sequentially. When the output signal of the output amplifier corresponding to a certain sampling resistor is detected to be less than Vth*X*T, it can be determined that all shunt circuits with resistance values ​​smaller than that sampling resistor are in an open-circuit state. Therefore, the magnitude of the current to be sampled, I, is:

[0041]

[0042] Furthermore, it should be noted that in this embodiment, the amplification factor of the output amplifier corresponding to each sampling resistor can be the same, or it can be 1, that is, no output amplifier is set. In addition, the amplification factors of each output amplifier can also be different. During calculation, the current can be calculated by back-calculation based on the amplification factor of each output amplifier.

[0043] In this embodiment, the automatic shunt adjustment module is implemented by an operational amplifier. The specific working principle is as follows: The positive terminal (non-inverting input) of the operational amplifier is connected to the comparison threshold voltage Vth, and the negative terminal (inverting input) is connected to the current input terminal. When the voltage V at the current input terminal is less than Vth, the operational amplifier output is high, and the corresponding shunt gate (MOSFET) is completely closed. At this time, the voltage between the source and drain of the MOSFET is less than Vth, so the leakage current of the MOSFET is extremely small, and it can be considered that no current flows through the corresponding sampling resistor, thus the corresponding shunt gate is open. As the current gradually increases, the voltage at the negative terminal of the operational amplifier rises, the output voltage of the operational amplifier decreases, and the corresponding MOSFET gradually turns on. As the MOSFET gradually turns on, the current flowing through the MOSFET gradually increases, and the voltage at the negative terminal of the operational amplifier remains basically constant. It can be seen that the automatic shunt adjustment module achieves automatic current shunting, and the path of the measured current changes with the current magnitude, thereby achieving the purpose of large current flowing through small resistance and small current flowing through large resistance. At the same time, it also controls the overall voltage drop of the circuit. Therefore, automatic shunt adjustment is the core component of this invention.

[0044] Furthermore, in this embodiment, the comparison voltage connected to the non-inverting input terminal of the automatic shunt adjustment module in each shunt circuit is different. Specifically, the comparison voltage connected to the automatic shunt adjustment module corresponding to the larger sampling resistor is smaller than that connected to the smaller sampling resistor. In this embodiment, specifically: V'n = Vth + (n-2)delt; where V'n represents the comparison voltage connected to the other input terminal of the automatic shunt adjustment module in the nth shunt circuit, Vth represents the maximum sampling voltage drop of the circuit, and delt represents the voltage deviation. By making the comparison voltage connected to the other input terminal of each automatic shunt adjustment module different, and by making the comparison voltage connected to the positive input terminal of the automatic shunt adjustment module in the shunt circuit with the smaller sampling resistance larger, the shunt gates can be opened sequentially instead of simultaneously. This ensures that a larger sampling resistor is used when measuring small currents, thus guaranteeing higher measurement accuracy.

[0045] Furthermore, the specific steps by which the microprocessor determines the state of each shunt gate based on the output voltage of the analog-to-digital converter, and then calculates the current value, are as follows:

[0046] S1. Determine whether the output voltage V0 of the output amplifier corresponding to the sampling resistor R0 is less than Vth*X*T. If yes, then determine that the operational amplifiers U2, U4, and R6 are high, and the MOSFETs Q1, Q2, Q3, and Q4 are all in the off state. The current only flows through R0, and the current to be measured is I = V0 / X / R0. If no, proceed to step S2. Then the output state of the operational amplifier U2 is uncertain, and it is uncertain whether the field-effect transistor Q1 has started to turn on. Some current may flow through Q1.

[0047] S2. Determine whether the output voltage V1 of the output amplifier corresponding to the sampling resistor R1 is less than Vth*X*T. If yes, it is determined that the shunt gate corresponding to the sampling resistor R2 is not open, that is, the current to be measured only flows through the sampling resistors R0 and R1, and the current to be measured i = (V0 / R0 + V1 / R1) / X. If no, proceed to step S3.

[0048] S3. Determine whether the output voltage V2 of the output amplifier corresponding to the sampling resistor R2 is less than Vth*X*T. If yes, it is determined that the shunt gate corresponding to the sampling resistor R3 is not open, that is, the current to be measured only flows through the sampling resistors R0, R1 and R2. Then the current to be measured I = (V0 / R0 + V1 / R1 + V2 / R2) / X. If not, proceed to step S4.

[0049] ...

[0050] Sn, determine whether the output voltage Vn of the output amplifier corresponding to the sampling resistor Rn is less than Vth*X*T. If so, then the current to be measured... Where X represents the amplification factor of the output amplifier, and n = 0, 1, ..., N, where N represents the number of sampling resistors.

[0051] Following this process, the voltage outputs of all amplifiers are acquired via an analog-to-digital converter (ADC). The calculation begins with the sampling resistor values ​​decreasing in descending order. If the voltage across sampling resistor Rn-1, after amplification, exceeds Vth*T*X, the calculation continues with the voltage across the next sampling resistor Rn, until the voltage Vn corresponding to sampling resistor Rn is less than Vth*T*X. The current value is then determined. Vi and Ri are the voltage and resistance values ​​corresponding to a sampling resistor Ri.

[0052] Furthermore, such as Figure 2 As shown in this embodiment, the non-inverting input terminals of the output amplifiers U1, U3, U5, and U7 are connected to the near-current input terminals of the corresponding sampling resistors, the inverting input terminals are grounded through resistors, and a feedback resistor is connected between the output terminals and the inverting input terminals.

[0053] Example 2

[0054] like Figure 3 As shown, Embodiment 2 of the present invention provides a large-range low-difference-voltage current measurement circuit. Similar to Embodiment 1, it includes: a microprocessor, a sampling resistor R0, an output amplifier U7, and a shunt circuit. Each shunt circuit includes a sampling resistor, an output amplifier, an automatic shunt adjustment module, and a shunt gate.

[0055] Unlike Embodiment 1, in this embodiment, there are two shunt circuits, and the sampling resistors in each shunt circuit are divided into R1 to R2. In addition, in this embodiment, the resistance values ​​of the sampling resistors satisfy the following condition: R0 > R1 > R2.

[0056] Specifically, in this embodiment, an ADC module is further provided between the output amplifier and the microprocessor to convert the analog signals output by each output amplifier into digital signals and send them to the microprocessor. Furthermore, in this embodiment, preferably, each output amplifier has the same amplification factor.

[0057] Specifically, in this embodiment, the sampling resistor satisfies the following condition:

[0058] R n / R n+1 =Y, n=0,1;

[0059] Where Y represents a proportionality constant greater than 1, R n and R n+1 These represent the resistance values ​​of sampling resistor Rn and sampling resistor Rn+1, respectively. Preferably, the value of Y is 10, so this embodiment can realize the measurement of three range currents with a range ratio of 10.

[0060] Specifically, such as Figure 3 As shown, in each shunt circuit of this embodiment, the sampling resistor R1 corresponds to the output amplifier U1, the corresponding automatic shunt adjustment module is the operational amplifier U2, and the corresponding shunt gate is the field-effect transistor Q1. The sampling resistor R2 corresponds to the output amplifier U3, the corresponding automatic shunt adjustment module is the operational amplifier U4, and the corresponding shunt gate is the field-effect transistor Q2.

[0061] Furthermore, in this embodiment, the comparison voltage connected to the non-inverting input terminal of the automatic shunt adjustment module in each shunt circuit is different. Specifically, the comparison voltage connected to the automatic shunt adjustment module corresponding to the larger sampling resistor is smaller than that connected to the smaller sampling resistor. In this embodiment, specifically: V'n = Vth + (n-2)delt; where V'n represents the comparison voltage connected to the other input terminal of the automatic shunt adjustment module in the nth shunt circuit, Vth represents the maximum sampling voltage drop of the circuit, and delt represents the voltage deviation. By making the comparison voltage connected to the other input terminal of each automatic shunt adjustment module different, and by making the comparison voltage connected to the positive input terminal of the automatic shunt adjustment module in the shunt circuit with the smaller sampling resistance larger, the shunt gates can be opened sequentially instead of simultaneously. This ensures that a larger sampling resistor is used when measuring small currents, thus guaranteeing higher measurement accuracy.

[0062] Furthermore, such as Figure 3 As shown in this embodiment, the non-inverting input terminals of the output amplifiers U1, U3, and U7 are connected to the near-current input terminals of the corresponding sampling resistors, the inverting input terminals are grounded through resistors, and a feedback resistor is connected between the output terminals and the inverting input terminals.

[0063] Example 3

[0064] like Figure 4 As shown, Embodiment 3 of the present invention provides a large-range low-difference-voltage current measurement circuit. Similar to Embodiment 1, it includes: a microprocessor, a sampling resistor R0, an output amplifier U7, and a shunt circuit. Each shunt circuit includes a sampling resistor, an output amplifier, an automatic shunt adjustment module, and a shunt gate.

[0065] Unlike Embodiment 1, in this embodiment, there are 4 shunt circuits, and the sampling resistors in each shunt circuit are divided into R1 to R4. In addition, in this embodiment, the resistance values ​​of the sampling resistors satisfy the following condition: R0 > R1 > R2 > R3 > R4.

[0066] Specifically, in this embodiment, an ADC module is further provided between the output amplifier and the microprocessor to convert the analog signals output by each output amplifier into digital signals and send them to the microprocessor. Furthermore, in this embodiment, preferably, each output amplifier has the same amplification factor.

[0067] Specifically, in this embodiment, the sampling resistor satisfies the following condition:

[0068] R n / R n+1 =Y, n=0, 1, 2, 3, 4;

[0069] Where Y represents a proportionality constant greater than 1, R n and R n+1 These represent the resistance values ​​of sampling resistor Rn and sampling resistor Rn+1, respectively. Preferably, the value of Y is 10, so this embodiment can realize the measurement of five range currents with a range ratio of 10.

[0070] Specifically, such as Figure 3As shown, in each shunt circuit of this embodiment, the sampling resistor R1 corresponds to output amplifier U1, the corresponding automatic shunt adjustment module is operational amplifier U2, and the corresponding shunt gate is field-effect transistor Q1. The sampling resistor R2 corresponds to output amplifier U3, the corresponding automatic shunt adjustment module is operational amplifier U4, and the corresponding shunt gate is field-effect transistor Q2. The sampling resistor R3 corresponds to output amplifier U5, the corresponding automatic shunt adjustment module is operational amplifier U6, and the corresponding shunt gate is field-effect transistor Q5. The three terminals of field-effect transistors Q3 and Q4 are connected in parallel. The sampling resistor R4 corresponds to output amplifier U71, the corresponding automatic shunt adjustment module is operational amplifier U8, and the corresponding shunt gates are field-effect transistors Q3 and Q4. The three terminals of field-effect transistors Q3 and Q4 are connected in parallel. In this embodiment, the shunt gate corresponding to the sampling resistor R4 schematically uses two PMOS transistors because when the current is relatively large, the MOS transistor also has internal resistance, and a voltage drop is generated when the current flows through it. Therefore, connecting parallel MOSFETs can reduce the sampling voltage drop of this circuit under high current conditions.

[0071] Furthermore, in this embodiment, the comparison voltage connected to the non-inverting input terminal of the automatic shunt adjustment module in each shunt circuit is different. Specifically, the comparison voltage connected to the automatic shunt adjustment module corresponding to the larger sampling resistor is smaller than that connected to the smaller sampling resistor. In this embodiment, specifically: V'n = Vth + (n-3)delt; where V'n represents the comparison voltage connected to the other input terminal of the automatic shunt adjustment module in the nth shunt circuit, Vth represents the maximum sampling voltage drop of the circuit, and delt represents the voltage deviation. By making the comparison voltage connected to the other input terminal of each automatic shunt adjustment module different, and by making the comparison voltage connected to the positive input terminal of the automatic shunt adjustment module in the shunt circuit with the smaller sampling resistance larger, the shunt gates can be opened sequentially instead of simultaneously. This ensures that a larger sampling resistor is used when measuring small currents, thus guaranteeing higher measurement accuracy.

[0072] Furthermore, such as Figure 3 As shown in this embodiment, the non-inverting input terminals of the output amplifiers U1, U3, and U7 are connected to the near-current input terminals of the corresponding sampling resistors, the inverting input terminals are grounded through resistors, and a feedback resistor is connected between the output terminals and the inverting input terminals.

[0073] Example 4

[0074] Embodiment 4 of the present invention provides a current calculation method for a current measurement circuit provided in Embodiments 1 to 3 of the present invention, the specific steps of which are as follows:

[0075] S1. Determine whether the output voltage V0 corresponding to the sampling resistor R0 is less than Vth*T. If yes, then the current to be measured I = V0 / X / R0. If no, proceed to step S2. T represents the safety factor.

[0076] S2. Determine whether the output voltage V1 corresponding to the sampling resistor R1 is less than Vth*T. If yes, then the current to be measured i = V0 / R0 + V1 / R1. If no, proceed to step S3.

[0077] S3. Determine whether the output voltage V2 corresponding to the sampling resistor R2 is less than Vth*T. If yes, then the current to be measured I = V0 / R0 + V1 / R1 + V2 / R2; if no, proceed to step S4.

[0078] ...

[0079] Sn, determine whether the output voltage Vn corresponding to the sampling resistor Rn is less than vth*T. If so, then the current to be measured... Where n = 0 ... N.

[0080] Specifically, in this embodiment, the above-mentioned current calculation method can be set in a microprocessor and automatically calculated by a program set in the microprocessor.

[0081] In summary, the embodiments of the present invention provide a large-range, low-dropout current detection circuit and its measurement method. By employing a simple automated circuit for high-speed switching of the sampling resistor and controlling the overall sampling voltage drop of the circuit, it can meet the measurement requirements of high-speed, large-range current. Furthermore, no changes are required to the sampling backend, resulting in low cost, high reliability, and wide implementability.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A large-range low-difference-voltage current measurement circuit, comprising a sampling resistor R0, one end of which is connected to a current input terminal and the other end of which is connected to a current output terminal; characterized in that, Also includes: The microprocessor comprises a microprocessor and multiple parallel shunt circuits, which are connected in parallel with a sampling resistor R0. Each shunt circuit includes a sampling resistor, an automatic shunt adjustment module, and a shunt gate. The sampling resistors in each shunt circuit are divided into R1 to RN, where N represents the number of shunt circuits. The resistance values ​​of each sampling resistor satisfy the condition: R0 > R1 > ... > Rn > ... > RN. In each shunt circuit, one input terminal of the automatic shunt adjustment module is connected to the current input terminal, and the other input terminal is connected to the comparison voltage. Its output terminal is connected to the control terminal of the shunt gate. One end of the shunt gate is connected to the current input terminal, and the other end is connected to one end of the sampling resistor. The other end of the sampling resistor is connected to the current output terminal. One end of each sampling resistor is connected to the input terminal of the microprocessor through an output amplifier; The microprocessor is used to determine the state of each shunt gate based on the output voltage of each sampling resistor, and to superimpose the current flowing through all the sampling resistors of the shunt circuits that are turned on, thereby calculating the current value to be measured.

2. The large-range low-difference-voltage current measurement circuit according to claim 1, characterized in that, The comparison voltage connected to the automatic shunt adjustment module corresponding to the sampling resistor Rn is less than the comparison voltage connected to the automatic shunt adjustment module corresponding to the sampling resistor Rn+1.

3. The large-range low-difference-voltage current measurement circuit according to claim 1, characterized in that, In each shunt circuit, the sampling resistor satisfies the following condition: R n / R n+1 =Y,n=0……N; Where Y represents a proportionality constant greater than 1, R n and R n+1 These represent the resistance values ​​of sampling resistor Rn and sampling resistor Rn+1, respectively.

4. A large-range low-difference-voltage current measurement circuit according to claim 3, characterized in that, The value of Y is 10.

5. A large-range low-difference-voltage current measurement circuit according to claim 1, characterized in that, It also includes an analog-to-digital converter, with one end of each sampling resistor connected to one of the output amplifiers. The analog-to-digital converter is used to convert the output voltage of each output amplifier into an analog-to-digital value and then send it to the microprocessor.

6. A large-range low-difference-voltage current measurement circuit according to claim 5, characterized in that, All output amplifiers have the same amplification factor.

7. A large-range low-difference-voltage current measurement circuit according to claim 1, characterized in that, In each shunt circuit, the shunt gate includes one or more field-effect transistors, whose gates are connected to the output of the corresponding automatic shunt adjustment module.

8. A large-range low-difference-voltage current measurement circuit according to claim 1, characterized in that, The automatic shunt adjustment module is an operational amplifier.

9. A large-range low-difference-voltage current measurement circuit according to claim 5, characterized in that, The specific steps by which the microprocessor determines the state of each shunt gate based on the output voltage of the analog-to-digital converter, and then calculates the current value, are as follows: S1. Determine whether the output voltage V0 corresponding to the sampling resistor R0 is less than Vth*T. If yes, then the current to be measured I = V0 / R0. If no, proceed to step S2. T represents the safety factor. S2. Determine whether the output voltage V1 corresponding to the sampling resistor R1 is less than Vth*T. If yes, then the current to be measured I = (V0 / R0 + V1 / R1). If no, proceed to step S3. S3. Determine whether the output voltage V2 corresponding to the sampling resistor R2 is less than Vth*T. If yes, then the current to be measured I = (V0 / R0 + V1 / R1 + V2 / R2); if no, proceed to step S4. …… Sn, determine whether the output voltage Vn corresponding to the sampling resistor Rn is less than Vth * T. If so, then the current to be measured... Where n=0……N; R i The value of the sampling resistor Ri is represented, i=0……n, and Vth represents the maximum sampling voltage drop of the large-range low-dropout current measurement circuit.

10. A large-range low-difference-voltage current measurement circuit according to claim 1, characterized in that, The non-inverting input terminal of the output amplifier is connected to the current input terminal of the corresponding sampling resistor, the inverting input terminal is grounded through a resistor, and a feedback resistor is connected between the output terminal and the inverting input terminal.

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