Current measuring circuit

Abstract

The invention provides a current measuring circuit which comprises a micro-control unit and at least two measuring range circuits, and each measuring range circuit comprises a resistor, an MOS tube and an operational amplifier. The resistor of the previous measuring range circuit is connected in series with the resistor of the next measuring range circuit, the resistor of the first measuring range circuit is connected with power supply equipment, and the resistor of the last measuring range circuit is connected with a load to be measured; the micro-control unit is used for traversing the output voltage of the operational amplifier of each range circuit in sequence; if it is determined that target voltages on the two sides of a resistor of the measuring range circuit are smaller than a preset threshold value based on the output voltage, target current of a to-be-measured load is determined based on the output voltage and the resistance value of the resistor; and if the target voltage is not less than the preset threshold value, continuing to traverse the output voltage of the operational amplifier of the next range circuit. According to the technical scheme of the invention, the current measurement circuit meets the measurement requirements of a plurality of current ranges, the current ranges can be automatically switched, and the current output is not interrupted.

Description

Technical Field

[0001] The present application relates to the field of circuit technology, and in particular to a current measurement circuit. Background Art

[0002] The current measurement circuit can also be called the current detection circuit. The current measurement circuit measures the current by sensing the voltage across the resistor. The current measurement circuit can be applied to high-voltage short-circuit protection, motor control, DC / DC converter, system power consumption management, secondary battery current management, battery management and other scenarios.

[0003] In these scenarios, the voltage across the resistor is usually between tens of mV and hundreds of mV. Based on this, if the resistor uses a larger resistance value, the current measurement circuit can measure a smaller current value, and if the resistor uses a smaller resistance value, the current measurement circuit can measure a larger current value. However, if the resistor uses a larger resistance value, a larger current value cannot be measured, and if the resistor uses a smaller resistance value, a smaller current value cannot be measured, so the current measurement circuit cannot meet the measurement requirements of multiple current ranges.

[0004] For example, if there are smaller current values ​​and larger current values ​​in the same scenario, it is impossible to select a suitable resistance value to simultaneously meet the measurement requirements of the smaller current value and the larger current value. Summary of the invention

[0005] The present application provides a current measurement circuit, which includes a microcontroller unit and at least two range circuits. For each range circuit, the range circuit includes a resistor, a MOS tube and an operational amplifier; wherein the resistor is connected in parallel with the MOS tube, the first input end of the operational amplifier is connected to the first end of the resistor, the second input end of the operational amplifier is connected to the second end of the resistor, and the output end of the operational amplifier is connected to the microcontroller unit;

[0006] The resistor of the first range circuit is connected in series with the resistor of the second range circuit, the resistor of the first range circuit is connected to the power supply device, and the resistor of the last range circuit is connected to the load to be measured;

[0007] The microcontrol unit is used to sequentially traverse the output voltage of the operational amplifier of each range circuit; if it is determined based on the output voltage that the target voltage on both sides of the resistor of the range circuit is less than a preset threshold, then determine the target current of the load to be measured based on the output voltage and the resistance value of the resistor; if the target voltage is not less than the preset threshold, then continue to traverse the output voltage of the operational amplifier of the next range circuit;

[0008] When the target voltage is not less than a preset threshold, the MOS tube of the range circuit is controlled to be turned on so that the current from the power supply device to the load to be measured passes through the MOS tube.

[0009] Exemplarily, the microcontroller unit is used to send a control signal to the MOS tube of the range circuit when the target voltage on both sides of the resistor of the range circuit is not less than a preset threshold value, and the control signal is used to control the conduction of the MOS tube of the range circuit so that the current from the power supply device to the load to be measured passes through the MOS tube.

[0010] Exemplarily, the microcontroller unit is used to determine the voltage across the resistor of the next range circuit based on the output voltage of the operational amplifier of the next range circuit of the range circuit after the MOS tube of the range circuit is turned on; determine the predicted voltage across the resistor of the next range circuit based on the voltage across the resistor of the next range circuit, the resistance value of the resistor of the range circuit and the resistance value of the resistor of the next range circuit; the microcontroller unit is used to send a recovery signal to the MOS tube of the range circuit if the predicted voltage is less than a preset threshold value, and the recovery signal is used to control the MOS tube of the range circuit to disconnect so that the current from the power supply device to the load to be measured passes through the resistor of the range circuit.

[0011] Exemplarily, for each range circuit, the range circuit further includes a differential operational amplifier, a comparator and a trigger; wherein the first input terminal of the differential operational amplifier is connected to the first end of the resistor, the second input terminal of the differential operational amplifier is connected to the second end of the resistor, the output terminal of the differential operational amplifier is connected to the comparator, and the comparator is connected to the trigger; the differential operational amplifier is used to amplify the target voltage on both sides of the resistor of the range circuit to obtain an amplified voltage, and input the amplified voltage to the comparator;

[0012] The comparator is used to compare the amplified voltage with a reference voltage, wherein the reference voltage is determined based on the preset threshold and the amplification factor corresponding to the differential operational amplifier; if the amplified voltage is not less than the reference voltage, a first level is output to the trigger;

[0013] The micro control unit is used to output a second level to the trigger;

[0014] The trigger is used to send a control signal to the MOS tube of the range circuit when receiving the first level and the second level, and the control signal is used to control the MOS tube of the range circuit to be turned on.

[0015] Exemplarily, the trigger is used to send a first response signal to the microcontroller unit when receiving the first level and the second level, wherein the first response signal indicates that the MOS tube of the range circuit is turned on so that the microcontroller unit stops traversing the output voltage of the operational amplifier of the range circuit.

[0016] Exemplarily, the comparator is used to output a third level to the trigger when the amplified voltage is less than the reference voltage; wherein, if the first level is a high level, the third level is a low level, and if the first level is a low level, the third level is a high level;

[0017] The trigger is used to maintain the previous signal transmission state when receiving the third level and the second level; wherein, maintaining the previous signal transmission state includes: if the previous signal transmission state is to send a control signal and a first response signal, the trigger sends the control signal to the MOS tube of the range circuit, and the trigger sends the first response signal to the micro control unit.

[0018] Exemplarily, the microcontroller unit is used to determine the voltage on both sides of the resistor of the next range circuit based on the output voltage of the operational amplifier of the next range circuit of the range circuit after the MOS tube of the range circuit is turned on; determine the predicted voltage on both sides of the resistor of the next range circuit based on the voltage on both sides of the resistor of the next range circuit, the resistance value of the resistor of the range circuit and the resistance value of the resistor of the next range circuit; the microcontroller unit is used to output a fourth level to the trigger if the predicted voltage is less than a preset threshold; wherein, if the second level is a high level, the fourth level is a low level, and if the second level is a low level, the fourth level is a high level;

[0019] The trigger is used to send a recovery signal to the MOS tube of the range circuit when receiving the fourth level and the third level, and the recovery signal is used to control the MOS tube of the range circuit to disconnect.

[0020] Exemplarily, the trigger is used to send a second response signal to the microcontroller unit when receiving the fourth level and the third level, and the second response signal indicates that the MOS tube of the range circuit is disconnected, so that the microcontroller unit continues to traverse the output voltage of the operational amplifier of the range circuit.

[0021] Exemplarily, if the target voltage across the resistor of the last range circuit is not less than the preset threshold, the resistance value of the resistor of the last range circuit is adjusted; wherein the adjusted resistance value is less than the resistance value before the adjustment. For each range circuit, the MOS tube of the range circuit includes a parasitic diode; for each range circuit, the MOS tube of the range circuit is an NMOS tube or a PMOS tube; wherein the preset threshold is determined based on the conduction voltage of the parasitic diode of the MOS tube.

[0022] As can be seen from the above technical solutions, in the embodiment of the present application, the current measurement circuit includes at least two range circuits, and the resistance values ​​of the resistors of different range circuits are different, that is, there are resistors with larger resistance values ​​and resistors with smaller resistance values. Based on the voltage across the resistor with larger resistance value, a smaller current value can be measured, and based on the voltage across the resistor with smaller resistance value, a larger current value can be measured, so that the measurement requirements of multiple current ranges are met through the current measurement circuit. For example, if there are smaller current values ​​and larger current values ​​in the same scenario, the measurement requirements of smaller current values ​​and larger current values ​​can be met at the same time. A larger measurement range and measurement accuracy can be taken into account by automatically switching the current range. When switching from a small current to a large current, automatic switching can be achieved, the current output is not interrupted, and the circuit elements of the current measurement circuit will not be damaged. For example, when the current reaches a certain threshold, it can flow directly from the parasitic diode of the MOS tube to prevent the resistor from burning out, and the current will not be interrupted, and will not affect the subsequent load. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram of a current measurement circuit in one embodiment of the present application;

[0024] Figure 2 is a schematic structural diagram of a current measurement circuit in one embodiment of the present application;

[0025] Figure 3 It is a structural schematic diagram of a current measurement circuit in one embodiment of the present application. DETAILED DESCRIPTION

[0026] In the embodiment of the present application, a current measurement circuit is proposed, which is a current measurement circuit with automatic range switching, and can also be called a current detection circuit. The current measurement circuit measures the current by sensing the voltage across the resistor. The current measurement circuit can be applied to high-voltage short-circuit protection, motor control, DC / DC converter, system power consumption management, secondary battery current management, battery management, etc., and there is no restriction on this application scenario.

[0027] The current measurement circuit may include a microcontroller unit and at least two range circuits. The microcontroller unit may be an MCU (Micro Controller Unit) or other types of control units. There is no limitation on the implementation of the microcontroller unit as long as it can realize the control of the range circuit.

[0028] The at least two range circuits can be two range circuits, three range circuits, four range circuits, etc. There is no limit on the number of range circuits. For the convenience of description, taking three range circuits as an example, these three range circuits are called range circuit a1, range circuit a2 and range circuit a3. When the number of range circuits is more or less, the working principle of the current measurement circuit is similar and will not be repeated in this embodiment.

[0029] For each range circuit, the range circuit may include a resistor, a MOS tube and an operational amplifier. Wherein, the resistor is connected in parallel with the MOS tube, the first input end of the operational amplifier is connected to the first end of the resistor, the second input end of the operational amplifier is connected to the second end of the resistor, and the output end of the operational amplifier is connected to the micro control unit. In addition, the resistor of the previous range circuit is connected in series with the resistor of the next range circuit, the resistor of the first range circuit is connected to the power supply device, and the resistor of the last range circuit is connected to the load to be measured. The resistance value of the resistor of the previous range circuit may be greater than the resistance value of the resistor of the next range circuit, and the resistance value of the resistor of the previous range circuit may also be less than the resistance value of the resistor of the next range circuit.

[0030] See also Figure 1 As shown, it is a schematic diagram of the structure of the current measurement circuit, taking the current measurement circuit including three range circuits as an example. The range circuit a1 may include a resistor R1, a MOS tube Q1 and an operational amplifier K1. The range circuit a2 may include a resistor R2, a MOS tube Q2 and an operational amplifier K2. The range circuit a3 may include a resistor R3, a MOS tube Q3 and an operational amplifier K3. The range circuit a1 is the first range circuit, and the resistor R1 of the range circuit a1 is connected to the power supply device (the power supply device is used to provide power to the load to be measured, and the power supply device is the current input terminal). The range circuit a3 is the last range circuit, and the resistor R3 of the range circuit a3 is connected to the load to be measured (the load to be measured is an electrical device). The current measurement circuit is used to measure the current of the load to be measured. The load to be measured can be any type of electrical device, and there is no restriction on the load to be measured.

[0031] See also Figure 1 As shown, for two adjacent range circuits, the resistance of the previous range circuit is connected in series with the resistance of the next range circuit. For example, the resistance R1 of the range circuit a1 is connected in series with the resistance R2 of the range circuit a2, and the resistance R2 of the range circuit a2 is connected in series with the resistance R3 of the range circuit a3.

[0032] The resistor R1 is connected in parallel with the MOS tube Q1, the first input end of the operational amplifier K1 is connected to the first end of the resistor R1, the second input end of the operational amplifier K1 is connected to the second end of the resistor R1, and the output end of the operational amplifier K1 is connected to the MCU. The resistor R2 is connected in parallel with the MOS tube Q2, the first input end of the operational amplifier K2 is connected to the first end of the resistor R2, the second input end of the operational amplifier K2 is connected to the second end of the resistor R2, and the output end of the operational amplifier K2 is connected to the MCU. The resistor R3 is connected in parallel with the MOS tube Q3, the first input end of the operational amplifier K3 is connected to the first end of the resistor R3, the second input end of the operational amplifier K3 is connected to the second end of the resistor R3, and the output end of the operational amplifier K3 is connected to the MCU.

[0033] The resistance value of the resistor of the previous range circuit is greater than or less than the resistance value of the resistor of the next range circuit, for example, the resistance value of the resistor of the previous range circuit is greater than the resistance value of the resistor of the next range circuit. For example, the resistance value of the resistor R1 of the range circuit a1 is greater than the resistance value of the resistor R2 of the range circuit a2, and the resistance value of the resistor R2 of the range circuit a2 is greater than the resistance value of the resistor R3 of the range circuit a3.

[0034] For example, resistors R1, R2 and R3 are all sampling resistors, the resistance value of resistor R1 is the largest, the resistance value of resistor R2 is moderate, and the resistance value of resistor R3 is the smallest, that is, R1>R2>R3.

[0035] See also Figure 1 As shown, for the range circuit, the MOS tube (MOS is the abbreviation of MOSFET, Metal Oxide Semiconductor Field Effect Transistor) of the range circuit can be an NMOS tube (N-Metal-Oxide-Semiconductor, N-type metal oxide semiconductor field effect transistor) or a PMOS tube (P-Metal-Oxide-Semiconductor, P-type metal oxide semiconductor field effect transistor).

[0036] For example, the MOS transistor Q1 may be an NMOS transistor or a PMOS transistor, the MOS transistor Q2 may be an NMOS transistor or a PMOS transistor, and the MOS transistor Q3 may be an NMOS transistor or a PMOS transistor.

[0037] For each range circuit, the MOS tube of the range circuit may also include a parasitic diode, such as MOS tube Q1 includes a parasitic diode, MOS tube Q2 includes a parasitic diode, and MOS tube Q3 includes a parasitic diode. For example, due to the limitation of the manufacturing process, there is a parasitic diode inside the MOS tube. When the voltage difference between the drain and the source of the MOS tube reaches the conduction voltage of the parasitic diode (such as 0.7V), the parasitic diode will be turned on. Figure 1 As shown, when the voltage U1 across the resistor R1 reaches the turn-on voltage of the parasitic diode, the parasitic diode of the MOS tube Q1 is turned on, so that the current flows through the parasitic diode instead of the resistor R1. When the voltage U2 across the resistor R2 reaches the turn-on voltage of the parasitic diode, the parasitic diode of the MOS tube Q2 is turned on, so that the current flows through the parasitic diode instead of the resistor R2. When the voltage U3 across the resistor R3 reaches the turn-on voltage of the parasitic diode, the parasitic diode of the MOS tube Q3 is turned on, so that the current flows through the parasitic diode instead of the resistor R3.

[0038] For example, since ADC (Analog-to Digital Converter) sampling has a sampling range and sampling bits, in order to ensure sampling accuracy, it is necessary to make the maximum measured voltage as close as possible to (but not exceed) the maximum sampling voltage of the ADC, so as to ensure that the sampling bits of the ADC are used as much as possible. In this way, if the sampling bits are large, then even if the LSB (Least Significant Bit) data is flipped (that is, the minimum sampling bit is unstable), the impact on the stability of the data is small.

[0039] Based on the above principle, a higher measurement accuracy can be obtained by using a larger resistor without exceeding the range. For example, if the voltage U1 across the resistor R1 is less than the preset threshold value (i.e., the voltage U1 does not exceed the range), the target current of the load to be measured is determined based on the voltage U1 across the resistor R1 and the resistance value of the resistor R1. If the voltage U1 across the resistor R1 is not less than the preset threshold value (i.e., the voltage U1 exceeds the range), and the voltage U2 across the resistor R2 is less than the preset threshold value (i.e., the voltage U2 does not exceed the range), the target current of the load to be measured is determined based on the voltage U2 across the resistor R2 and the resistance value of the resistor R2. If the voltage U2 across the resistor R2 is not less than the preset threshold value, and the voltage U3 across the resistor R3 is less than the preset threshold value, the target current of the load to be measured is determined based on the voltage U3 across the resistor R3 and the resistance value of the resistor R3.

[0040] Exemplarily, the microcontroller unit may sequentially traverse the output voltage of the operational amplifier of each range circuit. If the target voltage on both sides of the resistor of the range circuit is determined to be less than a preset threshold value based on the output voltage, the target current of the load to be measured is determined based on the output voltage and the resistance value of the resistor. If the target voltage is not less than the preset threshold value, the output voltage of the operational amplifier of the next range circuit is continued to be traversed, and so on. Among them, when the target voltage is not less than the preset threshold value, the microcontroller unit may also control the MOS tube of the range circuit to be turned on so that the current from the power supply device to the load to be measured passes through the MOS tube. For example, the microcontroller unit sends a control signal to the MOS tube of the range circuit, and the control signal is used to control the MOS tube of the range circuit to be turned on so that the current from the power supply device to the load to be measured passes through the MOS tube.

[0041] The preset threshold value may be determined based on the conduction voltage of the parasitic diode of the MOS tube, such as the preset threshold value is equal to the conduction voltage of the parasitic diode, or the preset threshold value is less than the conduction voltage of the parasitic diode, but the difference between the preset threshold value and the conduction voltage of the parasitic diode is small, such as the difference is less than a certain empirical value. For example, if the conduction voltage of the parasitic diode is 0.7V, the preset threshold value may be 0.7V.

[0042] See also Figure 1 As shown, the microcontroller unit traverses the output voltage of the operational amplifier K1 of the range circuit a1, and determines the target voltage U1 on both sides of the resistor R1 of the range circuit a1 based on the output voltage of the operational amplifier K1, such as determining the target voltage U1 based on the output voltage and the amplification factor of the operational amplifier K1.

[0043] If the target voltage U1 is less than the preset threshold, it means that the conduction voltage of the parasitic diode has not been reached, the parasitic diode will not be turned on, and the current passes through the resistor R1. Based on this, the target current of the load to be measured can be determined based on the output voltage of the operational amplifier K1 and the resistance value of the resistor R1. For example, the target voltage U1 is determined based on the output voltage of the operational amplifier K1 and the amplification factor of the operational amplifier K1, and the target voltage U1, the resistance value of the resistor R1 and the target current of the load to be measured satisfy Ohm's law, that is, the target current of the load to be measured is proportional to the target voltage U1 at both ends of the resistor R1. Therefore, the target current of the load to be measured can be determined based on the output voltage of the operational amplifier K1 and the resistance value of the resistor R1, and there is no restriction on this process.

[0044] For example, when R1=100Ω, R2=1Ω, R3=0.05Ω, and I=1mA, U1=0.1V, U2=0.001V, and U3=0.00005V. Based on this, since the target voltage U1 is less than the preset threshold and is directly sampled or sampled after amplification, the signal-to-noise ratio of the target voltage U1 will be significantly better than the signal-to-noise ratio of the target voltage U2 and the signal-to-noise ratio of the target voltage U3. Therefore, the target current of the load to be measured is determined based on the target voltage U1.

[0045] If the target voltage U1 is not less than the preset threshold, it means that the conduction voltage of the parasitic diode has been reached, the parasitic diode is turned on, and the current passes through the parasitic diode of the MOS tube Q1. Based on this, the micro control unit needs to continue to traverse the output voltage of the operational amplifier K2 of the range circuit a2, and determine the target voltage U2 on both sides of the resistor R2 of the range circuit a2 based on the output voltage of the operational amplifier K2, for example, the target voltage U2 is determined based on the output voltage of the operational amplifier K2 and the amplification factor of the operational amplifier K2.

[0046] If the target voltage U2 is less than the preset threshold, the current flows through the resistor R2. Based on this, the target current of the load to be measured can be determined based on the output voltage of the operational amplifier K2 and the resistance value of the resistor R2.

[0047] For example, when R1=100Ω, R2=1Ω, R3=0.05Ω, I=0.5A, U1=50V (theoretical value, cannot be achieved in practice), U2=0.5V, U3=0.025V. Based on this, since the target voltage U1 is not less than the preset threshold, and the target voltage U2 is less than the preset threshold, the target current of the load to be measured is no longer determined based on the target voltage U1, but is determined based on the target voltage U2.

[0048] For example, if the MOS tube Q1 does not have a parasitic diode, the following problem occurs: the power consumption on the resistor R1 is W=I 2 *R1, due to the sudden increase in current, the power consumption W will increase exponentially with the square of the current, which can easily burn out the resistor. The voltage across resistor R1 is U1=I*R1. Due to the sudden increase in current, U1 suddenly increases, which may burn out the operational amplifier K1 and other subsequent circuits. The voltage across resistor R1 is U1=I*R1. If the voltage at the power input is Ui and the voltage at the load is Uo=Ui-U1, due to the sudden increase in current, U1 suddenly increases and Uo suddenly decreases, which may cause the load to be tested to restart, freeze, and other problems.

[0049] In order to avoid the above problems, the MOS tube Q1 may have a parasitic diode, so that when the target current of the load to be measured suddenly increases, the target voltage U1 is not less than the preset threshold value, such as the target voltage U1 is greater than or equal to 0.7V, so that the parasitic diode of the MOS tube Q1 is turned on, and the large current flows directly through the parasitic diode of the MOS tube Q1. When the large current passes through the parasitic diode of the MOS tube Q1, a voltage drop of about 0.7V will be generated, and the voltage drop will fluctuate with the fluctuation of the current, which will reduce the power quality of the load to be measured and also waste some energy. In view of the problem caused by the voltage drop of about 0.7V caused by the above parasitic diode, in this embodiment, if the target voltage U1 is not less than the preset threshold value, the micro control unit can also send a control signal (such as a Small range Control signal, such as a low level signal) to the MOS tube Q1. After receiving the control signal, the MOS tube Q1 is turned on based on the control signal. After the MOS tube Q1 is turned on, the current from the power supply device to the load to be measured passes through the MOS tube Q1.

[0050] By turning on the MOS tube Q1, the current from the power supply device to the load to be tested passes through the MOS tube Q1, which can prevent the resistor R1 or the subsequent circuit from being burned out, and can also prevent the load to be tested from restarting. For example, after the MOS tube Q1 is turned on, since the internal resistance of the MOS tube Q1 is very small after the MOS tube Q1 is turned on, and the current does not flow through the parasitic diode of the MOS tube Q1, the impact on the circuit can be ignored. Therefore, the power consumption W is 0, the resistor will not be burned out, U1 is 0, and there will be no impact on the subsequent circuit, such as restarting the subsequent circuit, freezing, etc.

[0051] If the target voltage U2 is not less than the preset threshold, the current passes through the parasitic diode of the MOS tube Q2, and the micro control unit needs to continue to traverse the output voltage of the operational amplifier K3 of the range circuit a3, and determine the target voltage U3 on both sides of the resistor R3 of the range circuit a3 based on the output voltage of the operational amplifier K3. For example, the target voltage U3 is determined based on the output voltage of the operational amplifier K3 and the amplification factor of the operational amplifier K3.

[0052] If the target voltage U3 is less than the preset threshold, the current flows through the resistor R3. Based on this, the target current of the load to be measured can be determined based on the output voltage of the operational amplifier K3 and the resistance value of the resistor R3.

[0053] For example, when R1=100Ω, R2=1Ω, R3=0.05Ω, I=10A, U1=1000V (theoretical value, cannot be achieved in practice), U2=10V (theoretical value, cannot be achieved in practice), U3=0.5V. Based on this, since the target voltage U1 is not less than the preset threshold, and the target voltage U2 is not less than the preset threshold, and the target voltage U3 is less than the preset threshold, the target current of the load to be measured is no longer determined based on the target voltage U1 and the target voltage U2, but is determined based on the target voltage U3.

[0054] If the target voltage U2 is not less than the preset threshold, the microcontroller unit may also send a control signal (such as a Mid range Control signal, such as a low level signal) to the MOS tube Q2. After receiving the control signal, the MOS tube Q2 may be turned on based on the control signal. After the MOS tube Q2 is turned on, the current from the power supply device to the load to be tested may pass through the MOS tube Q2.

[0055] If the target voltage U3 is not less than the preset threshold value, since the range circuit a3 is already the last range circuit, the output voltage of the operational amplifier is no longer traversed, and the target current of the load to be measured is no longer determined, that is, the target current of the load to be measured is stopped. For example, when R1 = 100Ω, R2 = 1Ω, R3 = 0.05Ω, I = 50A, U1 = 5000V (theoretical value, which cannot be achieved in practice), U2 = 50V (theoretical value, which cannot be achieved in practice), U3 = 2.5V (theoretical value, which cannot be achieved in practice), based on this, since the target voltage U1, the target voltage U2 and the target voltage U3 are not less than the preset threshold value, the target current of the load to be measured is not determined.

[0056] If the target voltage U3 is not less than the preset threshold, the microcontroller unit may also send a control signal (such as a Big range Control signal, such as a low level signal) to the MOS tube Q3. After receiving the control signal, the MOS tube Q3 may be turned on based on the control signal. After the MOS tube Q3 is turned on, the current from the power supply device to the load to be tested may pass through the MOS tube Q3.

[0057] Exemplarily, if the target voltage U3 on both sides of the resistor R3 of the last range circuit a3 is not less than the preset threshold, it means that the current has exceeded the maximum measurement value of the current measurement circuit. Therefore, the resistance value of the resistor R3 of the last range circuit a3 can be adjusted, and the adjusted resistance value is less than the resistance value before adjustment, that is, by reducing the resistance value of the resistor R3, a larger current can be measured. For example, the resistor R3 can be a variable resistor that can dynamically adjust the resistance value of the resistor R3. On this basis, if it is determined that the target voltage U3 is not less than the preset threshold, the resistance value of the resistor R3 can be reduced, and the above process is repeated.

[0058] From the above, it can be seen that when the target voltage U1 is less than 0.7V, the target voltage U1 on both sides of the resistor R1 is considered to be valid, the data collected on the resistor R1 (i.e., the target voltage U1) is saved, and the target current of the load to be measured is determined based on the target voltage U1. When the target voltage U1 is greater than or equal to 0.7V, it is considered that the MOS tube Q1 is already turned on, the resistor R1 has been bypassed, and it is necessary to switch to the resistor R2 or the resistor R3. When the target voltage U2 is less than 0.7V, the target voltage U2 on both sides of the resistor R2 is considered to be valid, the data collected on the resistor R2 (i.e., the target voltage U2) is saved, and the target current of the load to be measured is determined based on the target voltage U2. When the target voltage U2 is greater than or equal to 0.7V, it is considered that the MOS tube Q2 is already turned on, the resistor R2 has been bypassed, and it is necessary to switch to the resistor R3. When the target voltage U3 is less than 0.7V, it is considered that the target voltage U3 on both sides of the resistor R3 is valid, the data collected on the resistor R3 (i.e., the target voltage U3) is saved, and the target current of the load to be measured is determined based on the target voltage U3. When the target voltage U3 is greater than or equal to 0.7V, it is considered that the MOS tube Q3 has been turned on, the resistor R3 has been bypassed, and the current has exceeded the maximum measurement value of the current measurement circuit, indicating that the subsequent stage is abnormal (short circuit) or exceeds the maximum range, and the resistance value of the resistor R3 needs to be adjusted.

[0059] When the load current is small, the microcontroller unit uses resistor R1 for sampling, and determines the target current of the load to be measured based on the target voltage U1 across the resistor R1 (for example, the voltage U1 generated across the resistor R1 = I*R1, which is amplified by the operational amplifier and then sampled by the microcontroller unit). When the load current increases, the microcontroller unit switches to resistor R2 or resistor R3 for sampling, and determines the target current of the load to be measured based on the target voltage U2 across the resistor R2 or the target voltage U3 across the resistor R3.

[0060] In the above process, the processing process of the load current changing from small to large is introduced. When the load current changes from large to small, for each range circuit, after the MOS tube of the range circuit is turned on, the micro control unit can also determine the voltage on both sides of the resistor of the next range circuit based on the output voltage of the operational amplifier of the next range circuit of the range circuit. Based on the voltage on both sides of the resistor of the next range circuit, the resistance value of the resistor of the range circuit and the resistance value of the resistor of the next range circuit, the predicted voltage on both sides of the resistor of the range circuit is determined. On this basis, if the predicted voltage is less than the preset threshold, the micro control unit can send a recovery signal to the MOS tube of the range circuit, and the recovery signal is used to control the MOS tube of the range circuit to be disconnected, so that the current from the power supply device to the load to be measured passes through the resistor of the range circuit.

[0061] For example, after the MOS tube Q2 of the range circuit a2 is turned on, if the MOS tube Q3 of the range circuit a3 is not turned on, that is, the voltage U3 on both sides of the resistor R3 is less than the preset threshold, the microcontroller unit can obtain the output voltage of the operational amplifier K3 of the range circuit a3, and determine the voltage U3 on both sides of the resistor R3 based on the output voltage of the operational amplifier K3. For example, the microcontroller unit determines the voltage U3 on both sides of the resistor R3 based on the output voltage of the operational amplifier K3 and the amplification factor of the operational amplifier K3.

[0062] Then, the microcontroller unit can determine the predicted voltage U2 across the resistor R2 of the range circuit a2 based on the voltage U3 across the resistor R3, the resistance value of the resistor R2 of the range circuit a2, and the resistance value of the resistor R3 of the range circuit a3. For example, the predicted voltage U2 can be a predicted value rather than an actual measured value, such as the ratio of the voltage U3 to the predicted voltage U2 is equal to the ratio of the resistance value of the resistor R3 to the resistance value of the resistor R2, and therefore, the predicted voltage U2 across the resistor R2 can be predicted.

[0063] If the predicted voltage U2 is less than the preset threshold, it means that the load current is reduced. Even if the MOS tube Q2 is disconnected, the voltage on both sides of the resistor R2 can be reduced to below the preset threshold. Therefore, the micro control unit can send a recovery signal to the MOS tube Q2 (such as a Mid range Control signal, such as a high level signal, which is similar to the above control signal, except that one is a high level signal and the other is a low level signal). After receiving the recovery signal, the MOS tube Q2 can disconnect the MOS tube Q2 based on the recovery signal. After the MOS tube Q2 is disconnected, the current from the power supply device to the load to be measured does not pass through the MOS tube Q2, that is, the current from the power supply device to the load to be measured passes through the resistor R2 of the range circuit a2.

[0064] For example, after the MOS tube Q1 of the range circuit a1 is turned on, if the MOS tube Q2 of the range circuit a2 is not turned on, that is, the voltage U2 across the resistor R2 is less than the preset threshold, the micro control unit can obtain the output voltage of the operational amplifier K2 of the range circuit a2, and determine the voltage U2 across the resistor R2 based on the output voltage of the operational amplifier K2. Then, based on the voltage U2 across the resistor R2, the resistance value of the resistor R1 and the resistance value of the resistor R2, the predicted voltage U1 across the resistor R1 is determined.

[0065] If the predicted voltage U1 is less than the preset threshold, the microcontroller unit may send a recovery signal (such as a Small range Control signal, such as a high level signal) to the MOS transistor Q1. After receiving the recovery signal, the MOS transistor Q1 may disconnect the MOS transistor Q1 based on the recovery signal.

[0066] After the MOS tube Q1 is disconnected, the current from the power supply device to the load to be measured does not pass through the MOS tube Q1, that is, the current from the power supply device to the load to be measured passes through the resistor R1 of the range circuit a1.

[0067] As can be seen from the above technical solutions, in the embodiment of the present application, the current measurement circuit includes at least two range circuits, and the resistance values ​​of the resistors of different range circuits are different. The voltage across the resistor with a larger resistance value can measure a smaller current value, and the voltage across the resistor with a smaller resistance value can measure a larger current value, so that the measurement requirements of multiple current ranges are met through the current measurement circuit. The current range can be automatically switched to take into account a larger measurement range and measurement accuracy. When switching from a small current to a large current, automatic switching can be achieved through a microcontroller unit, and the current output is not interrupted, and the circuit elements of the current measurement circuit will not be damaged. For example, when the current reaches a certain threshold, it flows directly from the parasitic diode of the MOS tube to prevent the resistor from burning out, and the current will not be interrupted, and will not affect the subsequent load. When switching from a small current to a large current, the relevant data can be saved, and the current during the switching process is also valid and will not be interrupted.

[0068] A current measurement circuit is proposed in an embodiment of the present application, which is a current measurement circuit that automatically switches the range. The current measurement circuit may include a microcontroller unit and at least two range circuits, and the microcontroller unit may be an MCU. The at least two range circuits may be two range circuits, three range circuits, four range circuits, etc., taking three range circuits as an example. For each range circuit, the range circuit may include a resistor, a MOS tube, an operational amplifier, a differential operational amplifier (the differential operational amplifier is another operational amplifier), a comparator, and a trigger (such as an RS trigger, where R and S in the RS trigger represent reset and set, respectively).

[0069] Among them, the resistor is connected in parallel with the MOS tube, the first input end of the operational amplifier is connected to the first end of the resistor, the second input end of the operational amplifier is connected to the second end of the resistor, and the output end of the operational amplifier is connected to the microcontroller unit. The resistor of the previous range circuit is connected in series with the resistor of the next range circuit, the resistor of the first range circuit is connected to the power supply device, and the resistor of the last range circuit is connected to the load to be measured. The resistance value of the resistor of the previous range circuit is greater than the resistance value of the resistor of the next range circuit.

[0070] The first input terminal of the differential operational amplifier is connected to the first end of the resistor, the second input terminal of the differential operational amplifier is connected to the second end of the resistor, the output terminal of the differential operational amplifier is connected to the comparator, and the comparator is connected to the trigger.

[0071] See also Figure 2 As shown, it is a schematic diagram of the structure of the current measurement circuit, taking three range circuits as an example. The range circuit a1 may include a resistor R1, a MOS tube Q1, an operational amplifier K1, a differential operational amplifier AMP1, a comparator COMP1 and a trigger 1. The range circuit a2 may include a resistor R2, a MOS tube Q2, an operational amplifier K2, a differential operational amplifier AMP2, a comparator COMP2 and a trigger 2. The range circuit a3 may include a resistor R3, a MOS tube Q3, an operational amplifier K3, a differential operational amplifier AMP3, a comparator COMP3 and a trigger 3. In addition, the range circuit a1 is the first range circuit, and the resistor R1 of the range circuit a1 is connected to the power supply device. The range circuit a3 is the last range circuit, and the resistor R3 of the range circuit a3 is connected to the load to be measured. In addition, the resistor of the previous range circuit is connected in series with the resistor of the next range circuit. The resistance value of the resistor of the previous range circuit is greater than the resistance value of the resistor of the next range circuit, or the resistance value of the resistor of the previous range circuit is smaller than the resistance value of the resistor of the next range circuit.

[0072] For range circuit a1, resistor R1 is connected in parallel with MOS tube Q1, the first input terminal of operational amplifier K1 is connected to the first terminal of resistor R1, the second input terminal of operational amplifier K1 is connected to the second terminal of resistor R1, and the output terminal of operational amplifier K1 is connected to MCU. The first input terminal of differential operational amplifier AMP1 is connected to the first terminal of resistor R1, the second input terminal of differential operational amplifier AMP1 is connected to the second terminal of resistor R1, the output terminal of differential operational amplifier AMP1 is connected to comparator COMP1 (such as the output terminal of differential operational amplifier AMP1 is connected to the positive input terminal of comparator COMP1), the negative input terminal of comparator COMP1 is connected to reference voltage VREF, and the output terminal of comparator COMP1 is connected to trigger 1. The connection relationship between range circuit a2 and range circuit a3 is similar to that of range circuit a1, which can be seen in Figure 2 As shown, no further description is given here.

[0073] See also Figure 2 As shown, for the range circuit, the MOS transistor of the range circuit can be an NMOS transistor or a PMOS transistor. For each range circuit, the MOS transistor of the range circuit can also include a parasitic diode.

[0074] Exemplarily, the microcontroller unit can sequentially traverse the output voltage of the operational amplifier of each range circuit. If the target voltage on both sides of the resistor of the range circuit is determined to be less than a preset threshold value based on the output voltage, the target current of the load to be measured is determined based on the output voltage and the resistance value of the resistor. If the target voltage is not less than the preset threshold value, the output voltage of the operational amplifier of the next range circuit is continued to be traversed, and so on. Among them, when the target voltage is not less than the preset threshold value, the MOS tube of the range circuit can be controlled to be turned on through the differential operational amplifier AMP, the comparator COMP and the trigger, that is, the MOS tube of the range circuit is controlled to be turned on through the hardware circuit, so that the current from the power supply device to the load to be measured passes through the MOS tube.

[0075] For example, the preset threshold value may be determined based on the conduction voltage of the parasitic diode of the MOS tube, such as the preset threshold value is equal to the conduction voltage of the parasitic diode, or the preset threshold value is less than the conduction voltage of the parasitic diode, but the difference between the preset threshold value and the conduction voltage of the parasitic diode is small, such as the difference is less than a certain empirical value. For example, if the conduction voltage of the parasitic diode is 0.7V, the preset threshold value may be 0.7V.

[0076] For example, when the MOS tube of the range circuit is turned on by controlling the hardware circuit (such as the differential operational amplifier AMP, the comparator COMP and the trigger), the differential operational amplifier can amplify the target voltage on both sides of the resistor of the range circuit to obtain the amplified voltage, and input the amplified voltage to the comparator. The comparator can compare the amplified voltage with the reference voltage (the reference voltage is determined based on the preset threshold and the amplification factor corresponding to the differential operational amplifier). If the amplified voltage is not less than the reference voltage, the comparator outputs the first level to the trigger, and if the amplified voltage is less than the reference voltage, the comparator outputs the third level to the trigger. If the first level is a high level, the third level is a low level, and if the first level is a low level, the third level is a high level. In addition, the micro control unit can output a second level to the trigger, such as continuously outputting the second level.

[0077] When the trigger receives the first level and the second level, the control signal is sent to the MOS tube of the range circuit, and the control signal is used to control the MOS tube of the range circuit to be turned on. When the trigger receives the first level and the second level, the trigger can also send a first response signal to the micro control unit, and the first response signal indicates that the MOS tube of the range circuit is turned on, so that the micro control unit stops traversing the output voltage of the operational amplifier of the range circuit, that is, no longer determines the target current of the load to be measured based on the output voltage. When the trigger receives the third level and the second level, the last signal transmission state is maintained. Maintaining the last signal transmission state may include: if the last signal transmission state is to send a control signal and a first response signal, the trigger sends a control signal to the MOS tube of the range circuit, and the trigger sends a first response signal to the micro control unit.

[0078] See also Figure 2 As shown, the microcontroller unit traverses the output voltage of the operational amplifier K1 of the range circuit a1, and determines the target voltage U1 on both sides of the resistor R1 of the range circuit a1 based on the output voltage of the operational amplifier K1. If the target voltage U1 is less than the preset threshold, the microcontroller unit determines the target current of the load to be measured based on the output voltage of the operational amplifier K1 and the resistance value of the resistor R1, and this process will not be repeated.

[0079] The differential amplifier AMP1 can amplify the target voltage U1 on both sides of the resistor R1 to obtain the amplified voltage U1', and the differential amplifier AMP1 inputs the amplified voltage U1' (i.e., the output voltage of the differential amplifier AMP1) to the comparator COMP1. The two input voltages of the comparator COMP1 are the amplified voltage U1' and the reference voltage VREF, and the reference voltage VREF can be determined based on the preset threshold and the amplification factor corresponding to the differential amplifier AMP1. For example, if the amplified voltage U1' is M times (i.e., the amplification factor) of the target voltage U1, the reference voltage VREF can be M times the preset threshold (e.g., 0.7V).

[0080] The comparator COMP1 can compare the amplified voltage U1' and the reference voltage VREF. If the amplified voltage U1' is less than the reference voltage VREF, it means that the target voltage U1 is less than the preset threshold value. In this case, the comparator COMP1 can output a third level to the trigger 1, and the third level can be a low level, such as 0. If the amplified voltage U1' is not less than the reference voltage VREF, it means that the target voltage U1 is not less than the preset threshold value. The comparator COMP1 can output a first level to the trigger 1, and the first level can be a high level, such as 0.

[0081] Exemplarily, a control switch for the current measurement circuit can also be configured, and the control switch can be turned on when the target current of the load to be measured needs to be measured. When the control switch is turned on, the target current of the load to be measured is small, so the target voltage U1 is small, the output voltage U1' of the differential operational amplifier AMP1 is less than the reference voltage VREF, and the comparator COMP1 outputs a third level 0. When the control switch is turned on, the microcontroller unit can output a first level to the trigger 1, and the first level can be a high level, such as 1. The microcontroller unit only outputs a high level 1 to the trigger 1, and then the microcontroller unit continuously outputs a low level 0 to the trigger 1.

[0082] When the trigger receives the third level 0 and the first level 1, the trigger sends a high level (such as 1, i.e., a recovery signal in the subsequent process) to the MOS tube Q1, and the high level is used to control the MOS tube Q1 to be disconnected, i.e., the MOS tube Q1 is in a disconnected state, and the current does not pass through the MOS tube Q1. The trigger sends a second response signal (low level, such as 0) to the micro control unit, and the second response signal indicates that the MOS tube Q1 is disconnected, so that the micro control unit continues to traverse the output voltage of the operational amplifier K1 of the range circuit a1, so that the target voltage U1 on both sides of the resistor R1 of the range circuit a1 can be determined based on the output voltage of the operational amplifier K1.

[0083] For example, see Table 1, which is an example of a truth table of a trigger. When the control switch is turned off, the device under test has no current, and the amplified voltage U1' is less than the reference voltage VREF, then the comparator COMP1 outputs the third level 0 (indicated by S) to the trigger 1, and the microcontroller unit outputs the first level 1 (indicated by R) to the trigger 1. The trigger 1 sends a high level 1 to the MOS tube Q1 (indicated by The trigger 1 sends a second response signal 0 (indicated by Q) to the micro control unit.

[0084] Table 1

[0085]

[0086] After the microcontroller unit outputs a high level 1 to the trigger 1 , the microcontroller unit may output a second level (low level, such as 0) to the trigger 1 .

[0087] When it is necessary to obtain the current of the device under test, turn on the control switch. When the current of the device under test is small, the microcontroller outputs the second level 0 to the trigger 1. Since the amplified voltage U1' is less than the reference voltage VREF, the comparator COMP1 outputs the third level 0 to the trigger 1. When the trigger receives the third level and the second level, it maintains the previous signal transmission state. Maintaining the previous signal transmission state means that the trigger sends a high level to the MOS tube Q1, and the trigger sends a second response signal (such as a low level) to the microcontroller. For example, see Table 2, which is an example of a truth table for the trigger. R represents the second level 0, and S represents the third level 0. Trigger 1 sends a high level 1 to the MOS tube Q1 (through The trigger 1 sends a second response signal 0 (indicated by Q) to the micro control unit.

[0088] Table 2

[0089]

[0090] It can be seen from Table 2 that when the current is small, the target voltage U1 is small, the output voltage U1' of the differential amplifier AMP1 is less than the reference voltage VREF, the comparator COMP1 outputs 0, the S of the trigger 1 is 0, R is 0, and Q remains in the previous state 0. The previous state 1 is maintained, and the MOS tube Q1 is disconnected.

[0091] If the target voltage U1 is not less than the preset threshold, the microcontroller unit needs to continue to traverse the output voltage of the operational amplifier K2 of the range circuit a2, and determine the target voltage U2 on both sides of the resistor R2 of the range circuit a2 based on the output voltage of the operational amplifier K2. If the target voltage U2 is less than the preset threshold, the target current of the load to be measured can be determined based on the output voltage of the operational amplifier K2 and the resistance value of the resistor R2.

[0092] If the target voltage U1 is not less than the preset threshold, the MOS tube Q1 of the range circuit can also be controlled to be turned on through the hardware circuit (such as differential operational amplifier AMP1, comparator COMP1 and trigger 1), for example:

[0093] The differential operational amplifier AMP1 amplifies the target voltage U1 on both sides of the resistor R1 to obtain an amplified voltage U1', and the differential operational amplifier AMP1 inputs the amplified voltage U1' to the comparator COMP1. The comparator COMP1 can compare the amplified voltage U1' and the reference voltage VREF. If the amplified voltage U1' is not less than the reference voltage VREF, it means that the target voltage U1 is not less than the preset threshold. In this case, the comparator COMP1 can output a first level to the trigger 1, and the first level can be a high level, such as 1. The micro control unit can output a second level to the continuous trigger 1, and the second level can be a low level, such as 0.

[0094] On this basis, when the trigger receives the first level and the second level, it sends a control signal (the control signal may be a low level signal, such as a Small range Control signal) to the MOS transistor Q1, and the control signal is used to control the MOS transistor Q1 to be turned on. In addition, the trigger sends a first response signal (the first response signal may be a high level, such as 1) to the micro control unit, and the first response signal indicates that the MOS transistor Q1 is turned on.

[0095] After receiving the control signal, the MOS transistor Q1 is turned on based on the control signal. After the MOS transistor Q1 is turned on, the current from the power supply device to the load to be tested passes through the MOS transistor Q1.

[0096] When the microcontroller receives the first response signal, it learns that the MOS tube Q1 is turned on and stops traversing the output voltage of the operational amplifier K1 of the range circuit a1, that is, it no longer determines the target current of the load to be measured based on the output voltage of the operational amplifier K1, that is, it no longer collects data from the resistor R1.

[0097] For example, see Table 3, which is an example of a truth table of a trigger. The microcontroller outputs a second level 0 (indicated by R, denoted as QS_R1) to trigger 1. If the amplified voltage U1' is not less than the reference voltage VREF, the comparator COMP1 outputs a first level 1 (indicated by S) to trigger 1. Trigger 1 sends a low level 0 (indicated by The trigger 1 sends a first response signal 1 (indicated by Q) to the microcontroller unit.

[0098] Table 3

[0099]

[0100] It can be seen from Table 3 that when the current increases, the target voltage U1 exceeds the preset threshold, the output voltage U1' of the differential amplifier AMP1 is not less than the reference voltage VREF, the comparator COMP1 outputs 1, the trigger's S=1, R=0, therefore, the trigger's Q outputs 1, Output 0, thus controlling MOS tube Q1 to conduct large current directly through MOS tube Q1, and no longer through resistor R1, to avoid problems such as resistor burnout and subsequent load drop caused by large current flowing through resistor R1. In addition, the Q output of the trigger is sent to the interrupt pin of the microcontroller unit, informing the microcontroller unit that the sampling current in this path is too large and has been bypassed, so that the microcontroller unit can sample from resistor R2 or resistor R3 instead of resistor R1.

[0101] After the MOS tube Q1 is turned on, the target voltage U1 on both sides of the resistor R1 is approximately 0. At this time, the following processing can also be performed through the hardware circuit (such as the differential operational amplifier AMP, the comparator COMP and the trigger):

[0102] The differential operational amplifier AMP1 amplifies the target voltage U1 on both sides of the resistor R1 to obtain an amplified voltage U1', and the differential operational amplifier AMP1 inputs the amplified voltage U1' to the comparator COMP1. The comparator COMP1 can compare the amplified voltage U1' with the reference voltage VREF. If the amplified voltage U1' is less than the reference voltage VREF, it means that the target voltage U1 is less than the preset threshold. In this case, the comparator COMP1 can output the third level 0 to the trigger 1. The micro control unit can output the second level 0 to the continuous trigger 1.

[0103] When the trigger receives the third level and the second level, the trigger maintains the previous signal transmission state. For example, if the previous signal transmission state is to send a control signal and a first response signal, the trigger sends a control signal (low level signal) to the MOS tube Q1, and the control signal is used to control the MOS tube Q1 to be turned on. The trigger sends a first response signal (such as 1) to the micro control unit. After receiving the control signal, the MOS tube Q1 turns on the MOS tube Q1 based on the control signal. When the micro control unit receives the first response signal, it knows that the MOS tube Q1 is turned on and stops traversing the output voltage of the operational amplifier K1 of the range circuit a1.

[0104] For example, as shown in Table 4, the microcontroller outputs the second level 0 (indicated by R) to the trigger 1. If the amplified voltage U1' is less than the reference voltage VREF, the comparator COMP1 outputs the third level 0 (indicated by S) to the trigger 1. The trigger 1 sends a low level 0 (indicated by The trigger 1 sends a first response signal 1 (indicated by Q) to the microcontroller unit.

[0105] Table 4

[0106]

[0107] It can be seen from Table 4 that even if the target voltage U1 is less than the preset threshold, the MOS tube Q1 will not be disconnected again, so as to avoid the MOS tube Q1 being turned on again after being disconnected, and to avoid repeated switching of the MOS tube Q1.

[0108] See also Figure 2As shown, when the control switch is turned on, if the target voltage U2 is less than the preset threshold, the differential amplifier AMP2 amplifies the target voltage U2 on both sides of the resistor R2 to obtain the amplified voltage U2', and the amplified voltage U2' is input to the comparator COMP2. If the amplified voltage U2' is less than the reference voltage VREF, the comparator COMP2 outputs the third level to the trigger 2. The micro control unit outputs the first level to the trigger 2, the micro control unit outputs the first level to the trigger 1, and then continuously outputs the second level to the trigger 1.

[0109] When the control switch is turned on, trigger 2 sends a high level to MOS tube Q2, controls MOS tube Q1 to be disconnected, and trigger 2 sends a second response signal to the microcontroller unit, which indicates that MOS tube Q2 is disconnected, so that the microcontroller unit continues to traverse the output voltage of the operational amplifier K2 of the range circuit a2.

[0110] When the microcontroller unit continuously outputs the second level to the trigger 1, the trigger maintains the previous signal transmission state when receiving the third level and the second level. For example, the trigger sends a high level to the MOS tube Q1, and the trigger sends a second response signal to the microcontroller unit.

[0111] If the target voltage U2 is not less than the preset threshold, the microcontroller unit needs to continue to traverse the output voltage of the operational amplifier K3 of the range circuit a3, and determine the target voltage U3 on both sides of the resistor R3 of the range circuit a3 based on the output voltage of the operational amplifier K3. If the target voltage U3 is less than the preset threshold, the target current of the load to be measured can be determined based on the output voltage of the operational amplifier K3 and the resistance value of the resistor R3.

[0112] If the target voltage U2 is not less than the preset threshold, the MOS tube Q2 of the range circuit can also be controlled to be turned on through the hardware circuit (such as the differential operational amplifier AMP2, the comparator COMP2 and the trigger 2). The control process can refer to the process of controlling the MOS tube Q1 to be turned on through the hardware circuit, and will not be repeated here. In the control process, the trigger 2 can send a control signal (such as a Mid range Control signal) to the MOS tube Q2. After receiving the control signal, the MOS tube Q2 is turned on based on the control signal.

[0113] If the target voltage U3 is less than the preset threshold, the processing process of the hardware circuit (such as differential op amp AMP3, comparator COMP3 and trigger 3) can refer to the processing process of the hardware circuit (such as differential op amp AMP2, comparator COMP2 and trigger 2), which will not be repeated here.

[0114] If the target voltage U3 is not less than the preset threshold value, since the range circuit a3 is already the last range circuit, the output voltage of the operational amplifier is no longer traversed, and the target current of the load to be measured is no longer determined, that is, the target current of the load to be measured is stopped. For example, if an abnormality such as a short circuit occurs in the load, in order to prevent further damage, the control switch can be turned off, and the target current of the load to be measured is stopped when the control switch is turned off. Alternatively, if the abnormality is caused by unreasonable range selection, the resistance value of the resistor R3 of the last range circuit a3 can also be adjusted, and the adjusted resistance value is less than the resistance value before adjustment.

[0115] If the target voltage U3 is not less than the preset threshold, the MOS tube Q3 of the range circuit can also be controlled to be turned on through the hardware circuit (such as the differential operational amplifier AMP3, the comparator COMP3 and the trigger 3). The control process can refer to the process of controlling the MOS tube Q1 to be turned on through the hardware circuit, and will not be repeated here. In the control process, the trigger 3 can send a control signal (such as a Big range Control signal) to the MOS tube Q3. After receiving the control signal, the MOS tube Q3 is turned on based on the control signal.

[0116] In the above process, the preset threshold value can be controlled by adjusting the value of the reference voltage VREF. For example, when a larger voltage (such as as close to 0.7V as possible, but not exceeding 0.7V) is required to turn on the MOS tube, the reference voltage VREF can be increased, and when a smaller voltage (such as less than 0.7V and with a certain interval from 0.7V, such as 0.4V, 0.3V, etc.) is required to turn on the MOS tube, the reference voltage VREF can be reduced. In this way, the on-voltage of the MOS tube can be flexibly controlled by the reference voltage VREF, instead of sampling a fixed 0.7V to control the on-voltage of the MOS tube, and different reference voltages VREF can be configured based on different scenarios.

[0117] In the above process, the processing process of the load current changing from small to large is introduced. When the load current changes from large to small, for each range circuit, after the MOS tube of the range circuit is turned on, the micro control unit can also determine the voltage on both sides of the resistor of the next range circuit based on the output voltage of the operational amplifier of the next range circuit of the range circuit. Based on the voltage on both sides of the resistor of the next range circuit, the resistance value of the resistor of the range circuit and the resistance value of the resistor of the next range circuit, the predicted voltage on both sides of the resistor of the range circuit is determined. On this basis, if the predicted voltage is less than the preset threshold, the MOS tube of the range circuit can also be controlled to be disconnected through the hardware circuit (such as the differential operational amplifier AMP, the comparator COMP and the trigger). For example, the micro control unit outputs the fourth level to the trigger; wherein, if the second level is a high level, the fourth level is a low level, and if the second level is a low level, the fourth level is a high level. When the trigger receives the fourth level and the third level, it sends a recovery signal to the MOS tube of the range circuit, and the recovery signal is used to control the MOS tube of the range circuit to be disconnected, so that the current from the power supply device to the load to be measured passes through the resistance of the range circuit. And, when the trigger receives the fourth level and the third level, it sends a second response signal to the micro control unit, and the second response signal indicates that the MOS tube of the range circuit is disconnected, so that the micro control unit continues to traverse the output voltage of the operational amplifier of the range circuit.

[0118] For example, after the MOS tube Q2 of the range circuit a2 is turned on, if the MOS tube Q3 of the range circuit a3 is not turned on, the micro control unit can obtain the output voltage of the operational amplifier K3 of the range circuit a3, and determine the voltage U3 across the resistor R3 based on the output voltage of the operational amplifier K3. Then, the micro control unit determines the predicted voltage U2 across the resistor R2 of the range circuit a2 based on the voltage U3 across the resistor R3, the resistance value of the resistor R2 of the range circuit a2, and the resistance value of the resistor R3 of the range circuit a3.

[0119] If the predicted voltage U2 is less than the preset threshold, it means that the load current is reduced. Even if the MOS tube Q2 is disconnected, the voltage on both sides of the resistor R2 can be reduced below the preset threshold. Based on this, the micro control unit can output a fourth level to the trigger 2, and the fourth level can be a high level, such as 1.

[0120] The differential operational amplifier AMP2 can amplify the target voltage U2 (approximately 0) on both sides of the resistor R2 to obtain an amplified voltage U2', and input the amplified voltage U2' to the comparator COMP2. The comparator COMP2 compares the amplified voltage U2' with the reference voltage VREF. If the amplified voltage U2' is less than the reference voltage VREF, the comparator COMP2 outputs a third level to the trigger 2. The third level can be a low level, such as 0.

[0121] When trigger 2 receives the fourth level and the third level, it sends a recovery signal (such as a Mid range Control signal, the recovery signal can be a high level signal, the recovery signal is similar to the above control signal, except that one is a high level signal and the other is a low level signal) to MOS tube Q2, and the recovery signal is used to control the MOS tube Q2 to be disconnected, so that the current from the power supply device to the load to be measured passes through the resistor R2. In addition, trigger 2 sends a second response signal to the micro control unit, and the second response signal indicates that the MOS tube Q2 is disconnected, so that the micro control unit continues to traverse the output voltage of the operational amplifier K2 of the range circuit a2.

[0122] After receiving the recovery signal, the MOS tube Q2 can be disconnected based on the recovery signal. After the MOS tube Q2 is disconnected, the current from the power supply device to the load to be measured does not pass through the MOS tube Q2, that is, the current from the power supply device to the load to be measured passes through the resistor R2 of the range circuit a2.

[0123] For example, as shown in Table 5, the microcontroller outputs the fourth level 1 (indicated by R) to the trigger 2. If the amplified voltage U2' is less than the reference voltage VREF, the comparator COMP2 outputs the third level 0 (indicated by S) to the trigger 2. The trigger 2 sends a high level 1 (indicated by R) to the MOS tube Q2. The trigger 2 sends a second response signal 0 (indicated by Q) to the microcontroller unit.

[0124] Table 5

[0125]

[0126] Exemplarily, when the microcontroller unit outputs the fourth level to the trigger 2, it may only output a fourth level, and then resume outputting the second level to the trigger 2, and the second level may be a low level, such as 0. At this time, if the amplified voltage U2' is less than the reference voltage VREF, the comparator COMP2 outputs the third level to the trigger 2. When the trigger 2 receives the second level and the third level, it maintains the previous signal transmission state, that is, the trigger 2 sends a recovery signal (such as a high level) to the MOS tube Q2, and the recovery signal is used to control the MOS tube Q2 to disconnect, and the trigger 2 sends a second response signal to the microcontroller unit. As shown in Table 6, the microcontroller unit outputs the second level 0 (indicated by R) to the trigger 2, and the comparator COMP2 outputs the third level 0 (indicated by S) to the trigger 2. The trigger 2 sends a high level 1 ( Indicated by, high level 1 indicates a recovery signal), and sends a second response signal 0 (indicated by Q) to the micro control unit.

[0127] Table 6

[0128]

[0129]

[0130] For example, after the MOS tube Q1 of the range circuit a1 is turned on, if the MOS tube Q2 of the range circuit a2 is not turned on (disconnected), the micro control unit obtains the output voltage of the operational amplifier K2 of the range circuit a2, and determines the voltage U2 on both sides of the resistor R2 based on the output voltage of the operational amplifier K2. Based on the voltage U2 on both sides of the resistor R2, the resistance value of the resistor R1 and the resistance value of the resistor R2, the predicted voltage U1 on both sides of the resistor R1 is determined. If the predicted voltage U1 is less than the preset threshold, the MOS tube Q1 is controlled to be disconnected through the hardware circuit (such as the differential operational amplifier AMP1, the comparator COMP1 and the trigger 1). The processing process of the hardware circuit can refer to the processing process of the MOS tube Q2 disconnection, which will not be repeated here. During the processing process of the hardware circuit, a recovery signal (such as a Small range Control signal, such as a high level signal) can be sent to the MOS tube Q1. The MOS tube Q1 can disconnect the MOS tube Q1 based on the recovery signal.

[0131] After the MOS tube Q1 is disconnected, the micro control unit resumes acquiring the output voltage of the operational amplifier K1 of the range circuit a1, and determines the target current of the load to be measured based on the output voltage of the operational amplifier K1.

[0132] In one possible implementation, Figure 2 The control process of the PMOS tube is taken as an example. When the NMOS tube is used, the control process of the NMOS tube is similar. The difference is that: for the control process of the PMOS tube, the trigger The signal is output to the PMOS tube, and the Q signal of the trigger is output to the microcontroller unit or the trigger The signal is output to the microcontroller unit ( Figure 2 For the control process of the PMOS tube, see Figure 3 As shown in the figure, it is a schematic diagram of the structure of the current measurement circuit, the Q signal of the trigger is output to the PMOS tube, the Q signal of the trigger is output to the micro control unit or the trigger The signal is output to the microcontroller unit ( Figure 2 In this example, the Q signal of the trigger is output to the microcontroller unit). Figure 3 For the implementation method, see Figure 2 , I will not go into details here.

[0133] As can be seen from the above technical solutions, in the embodiment of the present application, the current measurement circuit includes at least two range circuits, and the resistance values ​​of the resistors of different range circuits are different. The voltage across the resistor with a larger resistance value can measure a smaller current value, and the voltage across the resistor with a smaller resistance value can measure a larger current value, so that the measurement requirements of multiple current ranges are met through the current measurement circuit. The current range can be automatically switched to take into account a larger measurement range and measurement accuracy. When switching from a small current to a large current, automatic switching can be achieved through a microcontroller unit, and the current output is not interrupted, and the circuit elements of the current measurement circuit will not be damaged. For example, when the current reaches a certain threshold, it flows directly from the parasitic diode of the MOS tube to prevent the resistor from burning out, and the current will not be interrupted, and will not affect the subsequent load. When switching from a small current to a large current, the relevant data can be saved, and the current during the switching process is also valid and will not be interrupted.

[0134] When switching from a small current to a large current, automatic switching can be achieved based on a hardware circuit (such as a differential operational amplifier AMP, a comparator COMP, and a trigger), that is, the MOS tube can be directly turned on through the differential operational amplifier AMP, the comparator COMP, and the trigger, so that the MOS tube is turned on, and automatic switching of the MOS tube is achieved. When the automatic switching of the MOS tube is achieved through a hardware circuit, when the target voltage is greater than or equal to the preset threshold, the comparator COMP can quickly sense the situation, and then the trigger controls the MOS tube to be turned on, thereby achieving fast switching of the MOS tube (switching between on and off), and the delay of the automatic switching is small.

[0135] In a possible implementation manner, all data involved in this embodiment (ie, data involved in the current measurement circuit) are acquired and used only with the knowledge and authorization of the relevant users.

[0136] In the embodiment of the present application, a current measurement circuit is proposed, which is a current measurement circuit that automatically switches the range. The current measurement circuit includes a microcontroller unit and at least two range circuits. For each range circuit, the range circuit includes a resistor, a MOS tube and an operational amplifier; wherein the resistor is connected in parallel with the MOS tube, the first input end of the operational amplifier is connected to the first end of the resistor, the second input end of the operational amplifier is connected to the second end of the resistor, and the output end of the operational amplifier is connected to the microcontroller unit. The resistor of the previous range circuit is connected in series with the resistor of the next range circuit, the resistor of the first range circuit is connected to the power supply device, and the resistor of the last range circuit is connected to the load to be measured. The microcontroller unit is used to sequentially traverse the output voltage of the operational amplifier of each range circuit; if the target voltage on both sides of the resistor of the range circuit is determined to be less than a preset threshold value based on the output voltage, the target current of the load to be measured is determined based on the output voltage and the resistance value of the resistor; if the target voltage is not less than the preset threshold value, the output voltage of the operational amplifier of the next range circuit is continued to be traversed; wherein, when the target voltage is not less than the preset threshold value, the MOS tube of the range circuit is controlled to be turned on so that the current from the power supply device to the load to be measured passes through the MOS tube.

[0137] Exemplarily, a microcontroller unit is used to send a control signal to the MOS tube of the range circuit when the target voltage on both sides of the resistor of the range circuit is not less than a preset threshold value, and the control signal is used to control the conduction of the MOS tube of the range circuit so that the current from the power supply device to the load to be measured passes through the MOS tube.

[0138] Exemplarily, the microcontroller unit is used to determine the voltage on both sides of the resistor of the next range circuit based on the output voltage of the operational amplifier of the next range circuit of the range circuit after the MOS tube of the range circuit is turned on; and to determine the predicted voltage on both sides of the resistor of the next range circuit based on the voltage on both sides of the resistor of the next range circuit, the resistance value of the resistor of the range circuit and the resistance value of the resistor of the next range circuit. Further, the microcontroller unit is used to send a recovery signal to the MOS tube of the range circuit if the predicted voltage is less than a preset threshold value, and the recovery signal is used to control the MOS tube of the range circuit to disconnect so that the current from the power supply device to the load to be measured passes through the resistor of the range circuit.

[0139] Exemplarily, for each range circuit, the range circuit also includes a differential operational amplifier, a comparator and a trigger; wherein the first input terminal of the differential operational amplifier is connected to the first end of the resistor, the second input terminal of the differential operational amplifier is connected to the second end of the resistor, the output terminal of the differential operational amplifier is connected to the comparator, and the comparator is connected to the trigger; the differential operational amplifier is used to amplify the target voltage on both sides of the resistor of the range circuit to obtain an amplified voltage, and input the amplified voltage to the comparator; the comparator is used to compare the amplified voltage with a reference voltage, wherein the reference voltage is determined based on a preset threshold and the amplification factor corresponding to the differential operational amplifier; if the amplified voltage is not less than the reference voltage, a first level is output to the trigger; a microcontroller unit is used to output a second level to the trigger; the trigger is used to send a control signal to the MOS tube of the range circuit when receiving the first level and the second level, and the control signal is used to control the MOS tube of the range circuit to be turned on.

[0140] Exemplarily, a trigger is used to send a first response signal to the microcontroller unit when receiving a first level and a second level, wherein the first response signal indicates that the MOS tube of the range circuit is turned on so that the microcontroller unit stops traversing the output voltage of the operational amplifier of the range circuit.

[0141] Exemplarily, a comparator is used to output a third level to a trigger when the voltage after amplification is less than a reference voltage; wherein, if the first level is a high level, the third level is a low level, and if the first level is a low level, the third level is a high level; a trigger is used to maintain the last signal transmission state when receiving the third level and the second level; wherein maintaining the last signal transmission state includes: if the last signal transmission state is to send a control signal and a first response signal, the trigger sends a control signal to the MOS tube of the range circuit, and the trigger sends a first response signal to the micro control unit.

[0142] Exemplarily, a microcontroller unit is used to determine the voltage across the resistor of the next range circuit based on the output voltage of the operational amplifier of the next range circuit of the range circuit after the MOS tube of the range circuit is turned on; determine the predicted voltage across the resistor of the next range circuit based on the voltage across the resistor of the next range circuit, the resistance value of the resistor of the range circuit and the resistance value of the resistor of the next range circuit; the microcontroller unit is used to output a fourth level to a trigger if the predicted voltage is less than a preset threshold; wherein, if the second level is a high level, the fourth level is a low level, and if the second level is a low level, the fourth level is a high level; the trigger is used to send a recovery signal to the MOS tube of the range circuit when receiving the fourth level and the third level, and the recovery signal is used to control the MOS tube of the range circuit to disconnect.

[0143] Exemplarily, the trigger is used to send a second response signal to the micro control unit when receiving the fourth level and the third level, and the second response signal indicates that the MOS tube of the range circuit is disconnected so that the micro control unit continues to traverse the output voltage of the operational amplifier of the range circuit.

[0144] Exemplarily, if the target voltage across the resistor of the last range circuit is not less than a preset threshold, the resistance value of the resistor of the last range circuit is adjusted; wherein the adjusted resistance value is less than the resistance value before adjustment. For each range circuit, the MOS tube of the range circuit includes a parasitic diode; for each range circuit, the MOS tube of the range circuit is an NMOS tube or a PMOS tube; wherein the preset threshold can be determined based on the conduction voltage of the parasitic diode of the MOS tube.

[0145] As can be seen from the above technical solutions, in the embodiment of the present application, the current measurement circuit includes at least two range circuits, and the resistance values ​​of the resistors of different range circuits are different, that is, there are resistors with larger resistance values ​​and resistors with smaller resistance values. Based on the voltage across the resistor with larger resistance value, a smaller current value can be measured, and based on the voltage across the resistor with smaller resistance value, a larger current value can be measured, so that the measurement requirements of multiple current ranges are met through the current measurement circuit. For example, if there are smaller current values ​​and larger current values ​​in the same scenario, the measurement requirements of smaller current values ​​and larger current values ​​can be met at the same time. A larger measurement range and measurement accuracy can be taken into account by automatically switching the current range. When switching from a small current to a large current, automatic switching can be achieved, the current output is not interrupted, and the circuit elements of the current measurement circuit will not be damaged. For example, when the current reaches a certain threshold, it can flow directly from the parasitic diode of the MOS tube to prevent the resistor from burning out, and the current will not be interrupted, and will not affect the subsequent load.

[0146] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A current measurement circuit, characterized in that: The current measurement circuit includes a microcontroller unit and at least two range circuits. For each range circuit, the range circuit includes a resistor, a MOS tube and an operational amplifier; wherein the resistor is connected in parallel with the MOS tube, the first input end of the operational amplifier is connected to the first end of the resistor, the second input end of the operational amplifier is connected to the second end of the resistor, and the output end of the operational amplifier is connected to the microcontroller unit; The resistor of the first range circuit is connected in series with the resistor of the second range circuit, the resistor of the first range circuit is connected to the power supply device, and the resistor of the last range circuit is connected to the load to be measured; The microcontrol unit is used to sequentially traverse the output voltage of the operational amplifier of each range circuit; if it is determined based on the output voltage that the target voltage on both sides of the resistor of the range circuit is less than a preset threshold, then determine the target current of the load to be measured based on the output voltage and the resistance value of the resistor; if the target voltage is not less than the preset threshold, then continue to traverse the output voltage of the operational amplifier of the next range circuit; When the target voltage is not less than a preset threshold, the MOS tube of the range circuit is controlled to be turned on so that the current from the power supply device to the load to be measured passes through the MOS tube.

2. The current measurement circuit according to claim 1, characterized in that: The microcontrol unit is used to send a control signal to the MOS tube of the range circuit when the target voltage on both sides of the resistor of the range circuit is not less than a preset threshold value. The control signal is used to control the MOS tube of the range circuit to be turned on so that the current from the power supply device to the load to be measured passes through the MOS tube.

3. The current measurement circuit according to claim 2, characterized in that: The microcontrol unit is used to determine the voltage on both sides of the resistor of the next range circuit based on the output voltage of the operational amplifier of the next range circuit of the range circuit after the MOS tube of the range circuit is turned on; determine the predicted voltage on both sides of the resistor of the next range circuit based on the voltage on both sides of the resistor of the next range circuit, the resistance value of the resistor of the range circuit and the resistance value of the resistor of the next range circuit; The micro control unit is used to send a recovery signal to the MOS tube of the range circuit if the predicted voltage is less than a preset threshold value. The recovery signal is used to control the MOS tube of the range circuit to disconnect so that the current from the power supply device to the load to be measured passes through the resistance of the range circuit.

4. The current measurement circuit according to claim 1, characterized in that: For each range circuit, the range circuit further includes a differential operational amplifier, a comparator and a trigger; wherein the first input terminal of the differential operational amplifier is connected to the first end of the resistor, the second input terminal of the differential operational amplifier is connected to the second end of the resistor, the output terminal of the differential operational amplifier is connected to the comparator, and the comparator is connected to the trigger; The differential operational amplifier is used to amplify the target voltage on both sides of the resistor of the range circuit to obtain an amplified voltage, and input the amplified voltage to the comparator; The comparator is used to compare the amplified voltage with a reference voltage, wherein the reference voltage is determined based on the preset threshold and the amplification factor corresponding to the differential operational amplifier; if the amplified voltage is not less than the reference voltage, a first level is output to the trigger; The micro control unit is used to output a second level to the trigger; The trigger is used to send a control signal to the MOS tube of the range circuit when receiving the first level and the second level, and the control signal is used to control the MOS tube of the range circuit to be turned on.

5. The current measurement circuit according to claim 4, characterized in that: The trigger is used to send a first response signal to the micro control unit when receiving the first level and the second level, wherein the first response signal indicates that the MOS tube of the range circuit is turned on, so that the micro control unit stops traversing the output voltage of the operational amplifier of the range circuit.

6. The current measuring circuit according to claim 4 or 5, characterized in that: The comparator is configured to output a third level to the trigger when the amplified voltage is less than the reference voltage; wherein if the first level is a high level, the third level is a low level, and if the first level is a low level, the third level is a high level; The trigger is used to maintain the previous signal transmission state when receiving the third level and the second level; wherein, maintaining the previous signal transmission state includes: if the previous signal transmission state is to send a control signal and a first response signal, the trigger sends the control signal to the MOS tube of the range circuit, and the trigger sends the first response signal to the micro control unit.

7. The current measurement circuit according to claim 6, characterized in that: The microcontrol unit is used to determine the voltage on both sides of the resistor of the next range circuit based on the output voltage of the operational amplifier of the next range circuit of the range circuit after the MOS tube of the range circuit is turned on; determine the predicted voltage on both sides of the resistor of the next range circuit based on the voltage on both sides of the resistor of the next range circuit, the resistance value of the resistor of the range circuit and the resistance value of the resistor of the next range circuit; The micro control unit is configured to output a fourth level to the trigger if the predicted voltage is less than a preset threshold; wherein if the second level is a high level, the fourth level is a low level, and if the second level is a low level, the fourth level is a high level; The trigger is used to send a recovery signal to the MOS tube of the range circuit when receiving the fourth level and the third level, and the recovery signal is used to control the MOS tube of the range circuit to disconnect.

8. The current measurement circuit according to claim 7, characterized in that: The trigger is used to send a second response signal to the micro control unit when receiving the fourth level and the third level, wherein the second response signal indicates that the MOS tube of the range circuit is disconnected so that the micro control unit continues to traverse the output voltage of the operational amplifier of the range circuit.

9. The current measurement circuit according to any one of claims 1 to 5, characterized in that: If the target voltages across the resistor of the last range circuit are not less than the preset threshold, the resistance value of the resistor of the last range circuit is adjusted; wherein the adjusted resistance value is less than the resistance value before adjustment.

10. The current measurement circuit according to any one of claims 1 to 5, characterized in that: For each range circuit, the MOS tube of the range circuit includes a parasitic diode; For each range circuit, the MOS tube of the range circuit is an NMOS tube or a PMOS tube; The preset threshold is determined based on the turn-on voltage of the parasitic diode of the MOS tube.

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