Wide-range current high-precision measuring circuit

Abstract

The invention discloses a wide-range current high-precision measuring circuit, and belongs to the technical field of power electronics. The circuit comprises a channel selection circuit, a sampling resistor network, a measuring circuit and an overvoltage protection circuit. The channel selection circuit switches different paths according to the magnitude of the input current, so that the current flows through the adaptive sampling resistor network; the sampling resistor network converts the current into a corresponding voltage; the measuring circuit measures the voltage and converts the voltage into readable data; the overvoltage protection circuit provides bidirectional overvoltage protection. All the circuits work cooperatively, high-precision measurement of wide-range current is achieved, and meanwhile the stability and reliability of the circuit are improved. The method solves the problems that a traditional single sampling resistor is narrow in measurement range and insufficient in precision, is suitable for scenes such as an instrument circuit with a large current change range and high measurement precision requirements, and has high practicability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, and particularly to a circuit for wide-range current high-precision measurement by using multi-step switching. BACKGROUND

[0002] In existing power electronic devices, current measurement generally adopts a sampling resistor to convert into voltage, to realize current measurement. However, a single sampling resistor is only suitable for accurate measurement of a relatively narrow range of current. For excessively large or small current, the accuracy of the resistor will cause the measurement error of the current to exceed the accuracy requirement. For example, when measuring small current, the voltage generated by a single large-value sampling resistor is too small for the measurement chip to accurately capture, resulting in low measurement accuracy. When measuring large current, the voltage generated by a single small-value sampling resistor may exceed the range of the measurement chip, not only affecting the measurement accuracy, but also possibly damaging the chip. In some instrument circuits with large current variation range and high measurement accuracy, how to ensure a large input current range and high-precision measurement has become a problem to be solved. SUMMARY

[0003] The present application aims to solve the problem that a single sampling resistor cannot achieve high-precision measurement under a wide range of current in the prior art, and provides a wide-range current high-precision measurement circuit to meet the needs of scenarios with large current variation range and high measurement accuracy.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solution: A wide-range current high-precision measurement circuit, comprising a channel selection circuit, a sampling resistor network, a measurement circuit, and an overvoltage protection circuit. The channel selection circuit is connected to the sampling resistor network and is used to switch different current paths according to the size of the input current, so that the current flows through the appropriate sampling resistor network. The sampling resistor network is connected to the measurement circuit and is used to convert the current flowing through it into corresponding voltage. The measurement circuit is used to measure the voltage output by the sampling resistor network and convert the measurement result into readable data. The overvoltage protection circuit is connected to the channel selection circuit and the measurement circuit, respectively, and is used to provide bidirectional overvoltage protection. The present application achieves the measurement coverage of a wide range of current from the overall architecture by the collaborative design of the four circuit modules, while taking into account the high-precision measurement requirement. The addition of the overvoltage protection circuit provides safety protection for the overall circuit, solving the problem of narrow measurement range and vulnerability to overvoltage damage of the traditional single sampling resistor.

[0005] Further, the channel selection circuit comprises MOS tubes Q1, Q2, Q3, Q4, U1 and resistors R1-R8; the on and off of the MOS tubes Q1, Q2, Q3, Q4, U1 are controlled by three-way control signals CUR_CTR_L, CUR_CTR_M and CUR_CTR_H, and the on and off of different MOS tubes are controlled to switch different current paths. The application uses the switching characteristics of MOS tubes and the precise control of three-way control signals to realize flexible switching of current paths and ensure that different sizes of currents can be matched to appropriate sampling resistor combinations.

[0006] Further, the sampling resistor network comprises high-precision resistors R8, R9, R16, R17, R18, R19 and R20; according to the different current paths switched by the channel selection circuit, the current flows through one of the resistor combinations R8 / R9 / R16 / / R17, R9 / R16 / / R17 and R16 / / R17, and R8>>R9>>R16 / / R17. By setting resistor combinations with different resistance values and high precision, the application realizes the adaptive conversion of currents in different ranges in combination with channel switching, small currents flow through large resistor combinations and large currents flow through small resistor combinations, which ensures that the converted voltage values are in the high-precision measurement interval of the measurement circuit and effectively improves the accuracy of wide-range current measurement.

[0007] Further, the measurement circuit comprises a measurement chip U2, filter capacitors C1 and C2, pull-up resistors R13, R14 and R15, and interface protection resistors R10, R11 and R12; the filter capacitors C1 and C2 are used to filter out interference signals; the pull-up resistors R13, R14 and R15 are used to improve the anti-interference ability of the output level; the interface protection resistors R10, R11 and R12 are used to realize pin input matching and protection of the measurement chip U2; the measurement chip U2 is used to sample the voltage output by the sampling resistor network and convert it into data storage. The filter capacitors reduce signal interference and improve the stability of measurement; the pull-up resistors enhance the anti-interference ability of the output level; the interface protection resistors protect the pins of the measurement chip; and the measurement chip realizes accurate conversion of voltage to data, which overall improves the performance of the measurement circuit.

[0008] Further, the overvoltage protection circuit comprises diodes D1 and D2; the diodes D1 and D2 constitute a bidirectional clamping circuit for clamping the voltage across the sampling pins of the measurement chip U2 within a range less than 0.7V and providing a discharge path for bidirectional surge impact current. The bidirectional clamping circuit effectively limits the voltage of the sampling pins of the measurement chip, avoiding damage to the chip caused by excessive voltage; and it provides a discharge path for bidirectional surge impact current, protecting the chips, MOS tubes and sampling resistors in the entire circuit.

[0009] Further, when the CUR_CTR_L control signal is on, the MOS tube Q1 is on, and the current flows through the sampling resistance combination containing R8; when the CUR_CTR_M control signal is on, the MOS tubes Q2 and Q3 are on, and the current flows through the sampling resistance combination containing R9 but not R8; when the CUR_CTR_H control signal is on, the MOS tubes Q4 and U1 are on, and the current flows through the sampling resistance combination containing only R16 / / R17. Through the correspondence between different control signals, MOS tube on state and sampling resistance combination, accurate path switching of small, medium and large current in different ranges is realized, and it is ensured that each current can be converted into a suitable voltage through an appropriate resistance combination.

[0010] Further, the precision level of the high-precision resistor is not less than 0.1%, so as to ensure the accuracy of current and voltage conversion.

[0011] Further, the measurement chip U2 adopts a current measurement chip with an I2C interface, and the pull-up resistors R13, R14 and R15 are connected to a power supply to provide a pull-up voltage for the SDA and SCL lines of the I2C interface. The I2C interface facilitates data interaction with external devices (such as MCUs), improving the versatility and integration of the circuit; the pull-up resistors provide stable pull-up voltage for the I2C interface lines, ensuring the stability and reliability of the interface communication and reducing data transmission errors.

[0012] Further, the diodes D1 and D2 are Schottky diodes, which have a low forward conduction voltage and a fast response speed. The low forward conduction voltage of the Schottky diode ensures the accuracy of the clamping effect and avoids affecting the normal sampling voltage; the fast response speed enables it to quickly respond to overvoltage and surge impact and play a protective role in time, improving the reaction sensitivity of the overvoltage protection circuit.

[0013] Further, the current flows from the VO- end, passes through the channel selection circuit and the sampling resistance network in turn, and is processed by the measurement circuit, and the overvoltage protection circuit provides protection in real time throughout the process. The flow path of the current in the circuit ensures the standardization of the current measurement process; the real-time intervention of the overvoltage protection circuit makes the circuit in a safe protection state throughout the current measurement process, further ensuring the stability and safety of the circuit operation.

[0014] The present application has the following beneficial effects: Achieve high-precision measurement of a wide range of currents: by switching different sampling resistance combinations through the channel selection circuit, small, medium and large currents can all be converted into voltage values suitable for the measurement chip, and by combining high-precision resistors and the processing of the measurement circuit, high-precision measurement in a wide current range is achieved, solving the problem of narrow measurement range and insufficient precision of traditional single sampling resistor.

[0015] Improve the stability and reliability of the circuit: the filter capacitor reduces the influence of the interference signal on the measurement; the pull-up resistor ensures the stability of the interface output level, improves the reliability of data transmission; the interface protection resistor and the overvoltage protection circuit work together to prevent excessive current and high voltage from damaging the circuit components, prolong the service life of the circuit, and enhance the stability of the circuit in complex environment.

[0016] The structure is reasonable and practical: the functions of each part of the circuit are clear, the cooperation is efficient, the circuit structure is simple, and the circuit can be easily realized and integrated into various power electronic devices, meeting the needs of different devices for wide-range current high-precision measurement, and having strong practicality and popularization value. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The figure is a structural schematic diagram of a wide-range current high-precision measurement circuit. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0019] The wide-range current high-precision measurement circuit provided by the present application is composed of a channel selection circuit, a sampling resistor network, a measurement circuit and an overvoltage protection circuit, and the specific implementation process is as follows: The channel selection circuit includes MOS tubes Q1, Q2, Q3, Q4, U1 and resistors R1-R8. It is used for channel switching for different sizes of current, so that the current flows through the appropriate sampling resistor network.

[0020] The specific implementation process is as follows: the CUR_CTR_L, CUR_CTR_M and CUR_CTR_H control signals control the conduction and turn-off of different MOS tubes. When the input current is small, the CUR_CTR_L control signal is connected, so that the MOS tube Q1 is turned on, and at this time the current path is switched to the sampling resistor combination containing the large resistance R8; when the input current is medium, the CUR_CTR_M control signal is connected, the MOS tubes Q2 and Q3 are turned on, and the current path is switched to the sampling resistor combination containing the medium resistance R9; when the input current is large, the CUR_CTR_H control signal is connected, the MOS tube Q4 and U1 are turned on, and the current path is switched to the sampling resistor combination containing only the small resistance R16 / / R17. The resistors R1-R8 play the role of voltage division and current limiting in the circuit, ensuring that the MOS tube can be normally turned on and turned off, and ensuring the stability and reliability of channel switching.

[0021] Sampling resistance network: including R8, R9, R16, R17, R18, R19, R20 high-precision resistors, and R8>>R9>>R16 / / R17, the resistance precision level is not less than 0.1%. Specifically used to realize the conversion of current and voltage, according to the selection of different channels of channel selection circuit, the most suitable sampling resistance resistance value is provided, and different range of current is converted into voltage value suitable for measurement circuit.

[0022] Further, when the current flows through different sampling resistance combinations, according to Ohm's law U=IR, the current generates corresponding voltage on the resistance. For small current, the sampling resistance combination containing large resistance R8 can generate larger voltage, which is convenient for the measurement circuit to capture; for medium current, the sampling resistance combination containing medium resistance R9 generates moderate voltage; for large current, the small resistance R16 / / R17 combination is used to avoid generating too high voltage. High-precision resistors ensure the accuracy of current and voltage conversion, and reduce the measurement error caused by insufficient resistance accuracy. R18, R19 and R20 play the role of auxiliary voltage division and matching, further optimizing the sampling effect.

[0023] Measurement circuit: including measurement chip U2, filter capacitors C1, C2, pull-up resistors R13, R14, R15, interface protection resistors R10, R11, R12; the measurement chip U2 uses a current measurement chip with I2C interface, and the pull-up resistors R13, R14, R15 are connected to the power supply. The measurement of the sampling voltage is realized, and the data is converted for reading and feedback.

[0024] Further, the voltage signal output by the sampling resistance network enters the measurement chip U2, and the filter capacitors C1, C2 filter the input voltage signal, filter out the high-frequency interference signal, make the voltage signal input to the measurement chip U2 more stable, and improve the accuracy of measurement. The pull-up resistors R13, R14, R15 provide pull-up voltage for the SDA and SCL lines of the I2C interface of the measurement chip U2, ensure the stability of the output level of the interface, improve the anti-interference ability, and ensure the reliability of data transmission. The interface protection resistors R10, R11, R12 play the role of matching and protection, limit the current flowing into the pins of the measurement chip U2, and prevent the chip pins from being damaged by excessive current. The measurement chip U2 samples the processed voltage signal, converts it into digital data and stores it for the MCU to extract at any time through the I2C interface.

[0025] Overvoltage protection circuit: including diodes D1, D2, and being Schottky diodes. Used for providing bidirectional overvoltage protection, using the forward conduction voltage of the diode as the clamping voltage, ensuring that the current conversion voltage of the sampling circuit does not exceed the pin voltage of the chip U2, while allowing bidirectional impact current to pass through the diode to release the channel.

[0026] Further, the diodes D1 and D2 constitute a bidirectional clamping circuit. When the voltage output by the sampling resistance network is too high and may exceed the voltage resistance of the sampling pin of the measurement chip U2, the diodes are turned on to clamp the voltage across the pin within a range of less than 0.7 V, avoiding damage to the chip. When there is a bidirectional surge current, the surge current can form a discharge channel through the diode D1 or D2, thereby protecting the chips, MOS tubes, and sampling resistance network in the entire circuit. The Schottky diode has a low forward conduction voltage and a fast response speed, and can quickly respond to overvoltage conditions and provide protection in a timely manner.

[0027] In the present application, the channel selection circuit and the sampling resistance network: the channel selection circuit switches different channels according to the current size, so that different ranges of currents can flow through the corresponding sampling resistance combinations. Since the resistance values in the sampling resistance network have the relationship R8 >> R9 >> R16 / / R17, small currents flow through large resistances and large currents flow through small resistances, ensuring that different ranges of currents can be converted into voltage values that can be accurately measured by the measurement circuit, and the two together achieve the conversion of wide-range currents to appropriate voltages.

[0028] In the present application, the sampling resistance network and the measurement circuit: the voltage signal output by the sampling resistance network is directly input to the measurement circuit, and the filter capacitor in the measurement circuit performs filtering processing on the voltage signal to reduce interference, allowing the measurement chip U2 to sample more accurately. At the same time, the interface protection resistor ensures that the voltage and current input to the measurement chip are within a safe range, and the two work together to improve the accuracy and reliability of the measurement.

[0029] In the present application, the overvoltage protection circuit constantly monitors the voltage output by the sampling resistance network to the measurement circuit and the possible surge current. When the voltage is too high or the surge current occurs, the diode is turned on for protection, ensuring that the MOS tube in the channel selection circuit, the resistance in the sampling resistance network, and the measurement chip in the measurement circuit are not damaged, and the entire circuit operates stably.

[0030] Embodiment 1, as shown in the figure, a wide-range current high-precision measurement circuit, the circuit consists of four main parts: Figure 1 Channel selection circuit: including MOS tubes Q1, Q2, Q3, Q4; resistors R1-R8; channel switching for different size currents, flowing through the appropriate sampling resistance network. Sampling resistance network: including R8, R9, R16, R17, R18, R19, R20 high-precision resistors, realizing the conversion of current and voltage.

[0031]

[0032] ​Measuring circuit: contains measuring chip U2; filter capacitor C1, C2; pull-up resistor R13, R14, R15; interface protection resistor R10, R11, R12. Realize the measurement of sampling voltage, and convert into data for reading and feedback.

[0033] Overvoltage protection circuit: provide bidirectional overvoltage protection through diode D1, D2.

[0034] The application can realize high-precision measurement of input current, and due to the adoption of channel switching circuit to cooperate with the sampling resistance network, accurate measurement of ultra-wide range current value is realized, and the overvoltage protection device provides a current shunt channel to prevent damage to the chip, MOS tube and sampling resistance network caused by excessive current instantaneous impact.

[0035] The circuit adopts four parts to constitute a wide-range current high-precision measurement circuit. The first part of the circuit includes MOS tubes Q1, Q2, Q3 and U1; resistors R1-R8 constitute a current measurement range channel selection part of the measurement circuit; the second part of the circuit includes R8, R9, R16, R17, R18, R19 and R20 high-precision resistors constituting a sampling resistance network, which provides the most suitable sampling resistance value according to the selection of different measurement channels, and converts it into a suitable voltage value for the measurement circuit to sample; the third part of the circuit is a measuring chip U2; filter capacitors C1 and C2; pull-up resistors R13, R14 and R15; interface protection resistors R10, R11 and R12 constitute a measurement circuit to sample the voltage value converted by the sampling resistance and convert it into data storage for MCU to extract at any time. The fourth part provides bidirectional overvoltage protection through diodes D1 and D2, and uses the forward conduction voltage of the diode as a clamping voltage to ensure that the current conversion voltage of the sampling circuit does not exceed the pin voltage of the chip U2, and at the same time allows bidirectional impact current to pass through the diode to release the channel.

[0036] The working principle of the circuit is: current flows from the VO- end, and the CUR_CRL_L\M\H three-way control signal is connected in turn, and MOS tubes Q1, Q2, Q3 and U1 are opened in turn, so that the current flows through one of the three sampling resistance networks R8 / R9 / R16 / / R17; R9 / R16 / / R17; R16 / / R17; The resistance values of the three resistance networks R8>>R9>>R16 / / R17 make it possible to select the best sampling resistance value for different range currents, so that the sampling voltage adapts to the highest precision measurement range of the chip U2, and at the same time meets the requirements of the circuit for wide-range current interval and high-precision measurement.

[0037] The resistance R8 and R18, the capacitor C1 are as the sampling input network of U2, improve the sampling anti-interference ability; The capacitor C2 is the working voltage filter capacitor of the chip U2, increases the working stability; The resistance R13-R15 makes the output level of the chip U2 stronger; The resistance R10-R12 makes the pin input matching resistance and protection resistance of the chip U2.

[0038] The two-way clamping circuit formed by diode D1, D2 makes the voltage between the sampling pin of the chip U2 less than 0.7V, meets the overvoltage protection between the sampling pin of the chip without affecting the sampling voltage range; At the same time, when there is a two-way surge impact current, the diode can be used as a discharge channel to provide protection for the entire circuit.

[0039] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the foregoing embodiments of the present application are described in detail, for those skilled in the art, it still can be modified, or part of the technical features of the equivalent replacement, within the spirit and principles of the present application, any modification, equivalent replacement, improvement, etc., should be included in the scope of the present application.

Claims

1. A wide-range, high-precision current measurement circuit, characterized in that, It includes a channel selection circuit, a sampling resistor network, a measurement circuit, and an overvoltage protection circuit. The channel selection circuit is connected to the sampling resistor network and is used to switch different current paths according to the magnitude of the input current, so that the current flows through the appropriate sampling resistor network. The sampling resistor network is connected to the measurement circuit and is used to convert the flowing current into the corresponding voltage. The measurement circuit is used to measure the voltage output by the sampling resistor network and convert the measurement result into readable data. The overvoltage protection circuit is connected to both the channel selection circuit and the measurement circuit to provide bidirectional overvoltage protection.

2. The wide-range high-precision current measurement circuit according to claim 1, characterized in that, The channel selection circuit includes MOSFETs Q1, Q2, Q3, Q4, and U1, as well as resistors R1-R8. The switching on and off of MOSFETs Q1, Q2, Q3, Q4, and U1 is controlled by three control signals: CUR_CTR_L, CUR_CTR_M, and CUR_CTR_H. By controlling the switching on and off of different MOSFETs, the switching of different current paths is achieved.

3. The wide-range high-precision current measurement circuit according to claim 1, characterized in that, The sampling resistor network includes high-precision resistors R8, R9, R16, R17, R18, R19, and R20. Depending on the different current paths switched by the channel selection circuit, the current flows through one of the following resistor combinations: R8 / R9 / R16 / / R17, R9 / R16 / / R17, and R16 / / R17, with R8>>R9>>R16 / / R17.

4. The wide-range high-precision current measurement circuit according to claim 1, characterized in that, The measurement circuit includes a measurement chip U2, filter capacitors C1 and C2, pull-up resistors R13, R14, and R15, and interface protection resistors R10, R11, and R12. The filter capacitors C1 and C2 are used to filter out interference signals. The pull-up resistors R13, R14, and R15 are used to improve the anti-interference capability of the output level. The interface protection resistors R10, R11, and R12 are used to achieve pin input matching and protection for the measurement chip U2. The measurement chip U2 is used to sample the voltage output from the sampling resistor network and convert it into data storage.

5. The wide-range high-precision current measurement circuit according to claim 1, characterized in that, The overvoltage protection circuit includes diodes D1 and D2; diodes D1 and D2 form a bidirectional clamping circuit, which is used to clamp the voltage across the sampling pin of the measurement chip U2 within a range of less than 0.7V, and at the same time provide a discharge channel when there is a bidirectional surge current.

6. The wide-range high-precision current measurement circuit according to claim 2, characterized in that, When the CUR_CTR_L control signal is turned on, MOSFET Q1 is turned on, and current flows through the sampling resistor combination including R8; when the CUR_CTR_M control signal is turned on, MOSFETs Q2 and Q3 are turned on, and current flows through the sampling resistor combination that does not include R8 but includes R9; when the CUR_CTR_H control signal is turned on, MOSFETs Q4 and U1 are turned on, and current flows through the sampling resistor combination that only includes R16 / / R17.

7. The wide-range high-precision current measurement circuit according to claim 3, characterized in that, The accuracy class of the high-precision resistor is not less than 0.1%.

8. The wide-range high-precision current measurement circuit according to claim 4, characterized in that, The measurement chip U2 is a current measurement chip with an I2C interface. The pull-up resistors R13, R14, and R15 are connected to the power supply to provide pull-up voltage for the SDA and SCL lines of the I2C interface.

9. The wide-range high-precision current measurement circuit according to claim 5, characterized in that, The diodes D1 and D2 are Schottky diodes, which have a low forward conduction voltage and a fast response speed.

10. The wide-range high-precision current measurement circuit according to claim 1, characterized in that, Current flows in from the VO- terminal, passes through the channel selection circuit and the sampling resistor network in sequence, and is then processed by the measurement circuit. The overvoltage protection circuit provides real-time protection throughout the entire process.

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