Total current measuring circuit

Abstract

The utility model belongs to the technical field of current measuring circuits, and particularly relates to a total current measuring circuit, which comprises a common-mode filter L7. A terminal 4 and a terminal 3 of the common mode filter L7 are respectively connected to a positive electrode and a negative electrode of the capacitor C11; the positive electrode of the capacitor C11 is connected with the first end of the sampling resistor R20 in series, and the two ends of the sampling resistor R20 are connected with a signal processing and amplifying module; two ends of the sampling resistor R20 are respectively connected with an input end Vin + and an input end Vin-of the measuring chip U4; the operational amplifier U11 is connected with the output end of the measuring chip U4, and the positive input end of the operational amplifier U11 is connected with a load resistor R13; the output end of the operational amplifier U11 is connected to the input end of the AD converter of the single-chip microcomputer. The total current measuring circuit provided by the utility model can realize high-precision current measurement.

Description

TECHNICAL FIELD

[0001] The utility model belongs to current measurement circuit technical field, more particularly to a total current measurement circuit. BACKGROUND

[0002] Current measurement systems are widely used in power systems, industrial automation, new energy vehicles, aerospace and other fields. For example, in the power system, current measurement systems are used to monitor the current changes of the power grid to ensure the stable operation of the power grid; in industrial automation, they are used to monitor the current consumption of equipment to achieve energy saving and optimize production; in new energy vehicles, current measurement systems are used to monitor the charge and discharge current of the battery to protect the battery and prolong its service life.

[0003] In the current current measurement system, most current measurements are obtained by sampling resistance to input the AD converter, and the current sampling resistance is a special resistor whose main function is to convert the current in the circuit into a voltage signal. When the current passes through the sampling resistance, according to Ohm's law, a voltage drop proportional to the current will be generated across the resistance. By measuring this voltage drop, the current in the circuit can be indirectly obtained. This voltage signal is then input to the AD converter, which converts it into a digital signal for further processing and analysis by a computer or microcontroller, thereby achieving indirect measurement of the current.

[0004] However, in the face of some complex signals, the signal changes quickly, the current waveform is irregular, and it is difficult to capture the true current, resulting in insufficient current measurement accuracy, so it is necessary to monitor the total current in the circuit. UTILITY MODEL CONTENT

[0005] In order to solve the technical problem of "facing some complex signals, signal changes quickly, current waveform is irregular, it is difficult to capture the true current, resulting in insufficient current measurement accuracy", the utility model provides a total current measurement circuit capable of improving current measurement accuracy.

[0006] The utility model provides the following technical scheme:

[0007] A total current measurement circuit, comprising a current measurement and conversion module, a signal processing and amplification module;

[0008] The current measurement and conversion module comprises a common mode filter L7, an input end of the common mode filter L7 being connected to a power supply input end; a capacitor C11, a terminal 4 of the common mode filter L7 being connected to a positive pole of the capacitor C11, and a terminal 3 of the common mode filter L7 being connected to a negative pole of the capacitor C11; and a sampling resistor R20, the positive pole of the capacitor C11 being connected in series with a first end of the sampling resistor R20, and the sampling resistor R20 being connected with a signal processing and amplification module at both ends, and the sampling resistor R20 being used to provide a current path for the signal processing and amplification module;

[0009] The signal processing and amplification module comprises a measurement chip U4, the sampling resistor R20 being connected with an input end Vin+ and an input end Vin- of the measurement chip U4 at both ends respectively, and the measurement chip U4 being capable of measuring a differential voltage generated by a current passing through the sampling resistor R20; and an operational amplifier U11 connected to an output end of the measurement chip U4, the operational amplifier U11 being an inverting operational amplifier, a load resistor R13 being grounded, and a resistance value of the load resistor R13 being divided by internal resistances of the input ends Vin+ and Vin- of the measurement chip U4 to constitute an amplification multiple, so as to realize amplification of an input signal, and then pass through a signal follower composed of the operational amplifier U11.

[0010] An output end of the operational amplifier U11 is connected to an AD converter input end of a single-chip microcomputer.

[0011] Further, the capacitor C11 is connected in parallel with a capacitor C115.

[0012] Further, the second end of the sampling resistor R20 is further connected with a positive pole of a diode D15, and a negative pole of the diode D15 is connected to an output voltage.

[0013] Further, the output voltage of the negative pole of the diode D15 is equal to 24V.

[0014] Further, the second end of the sampling resistor R20 is connected with the diode D15, the diode D15 being connected in series with a positive pole of a voltage stabilizing diode D15, and a negative pole of the voltage stabilizing diode D15 being connected to a 24V voltage.

[0015] Further, the measurement chip U4 adopts a current measurement chip INA138.

[0016] Further, an output end of the measurement chip U4 is connected with the operational amplifier U11, a positive input end of the operational amplifier U11 being connected with the output end of the measurement chip U4, and a negative input end of the operational amplifier U11 being connected in feedback with an output end of the operational amplifier U11.

[0017] Further, the operational amplifier U11 adopts a voltage follower operational amplifier TLV333.

[0018] Further, the output end of the operational amplifier U11 is connected with the negative pole of the stabilizing tube D38, and the positive pole of the stabilizing tube D38 is grounded.

[0019] Further, the total current measurement circuit comprises a connector J3, the connector J3 is used as an input point of the circuit, and is used for receiving an external signal, and a stabilizing diode D1 is connected between a terminal 1 and a terminal 3 of the connector J3, wherein a positive pole end of the stabilizing diode D1 is connected with the terminal 3 of the connector J3, and a negative pole end of the stabilizing diode D1 is connected with the terminal 1 of the connector J3.

[0020] Further, the stabilizing diode D1 is connected with a capacitor C12 in parallel, and the capacitor C12 is connected with the terminal 1 and the terminal 2 of the common mode filter L7 respectively.

[0021] Compared with the prior art, the total current measurement circuit has the following beneficial effects:

[0022] (1) The total current measurement circuit can realize high-precision current measurement and signal amplification by accurately measuring the voltage drop generated by the current flowing through the sampling resistor R20, and using the measurement chip U4 and the operational amplifier U11 to amplify and convert the signal, and finally converting the analog signal into a digital signal for single-chip microcomputer processing.

[0023] (2) The circuit can provide high-precision current measurement, which is crucial for applications that require accurate current monitoring; the circuit current detection has high reliability and is not prone to failure, and the maintenance is relatively convenient. This is particularly important for industrial applications that need to run stably for a long time; the circuit current detection can set different output ratios or mixing ratios according to needs, providing a certain flexibility. This is very useful for occasions that need to adjust the measurement range and precision according to different application scenarios.

[0024] The use of the circuit current detection is very simple, only needs to connect the input signal, and then can distribute or mix the output signal according to the predetermined ratio, without complex setting or calibration process. The circuit current detection is designed to accurately measure extremely low detection voltage within a wide common mode voltage range, which is very useful for power management, motor control and current monitoring in battery-powered devices and other applications. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a circuit diagram of the total current measurement circuit. DETAILED DESCRIPTION

[0026] The technical scheme of the utility model will be clearly described below in combination with the drawings. Obviously, the described embodiments are not all the embodiments of the utility model, and all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the utility model.

[0027] As shown in Figure 1 The utility model provides a total current measurement circuit, total current measurement circuit includes connector J3, connector J3 is this circuit's input point, as power input end. Connector J3 has three terminals, and the terminal 1 of connector J3 is connected with terminal 3 and is connected with the zener diode D1, wherein the anode of zener diode D1 is connected with the terminal 3 of connector J3, and the cathode of zener diode D1 is connected with the terminal 1 of connector J3;When input voltage fluctuation, zener diode D1 will adjust the voltage across its two terminals to maintain a relatively stable output voltage.

[0028] Reverse a zener diode D1 (usually refers to zener diode or schottky diode) in power input end is mainly for protecting circuit from reverse voltage or overvoltage, mainly has reverse voltage protection, overvoltage protection, voltage stabilization, current limiting effect. When selecting zener diode D1, the zener voltage should be higher than the normal working voltage of power supply, to ensure that the diode will not be turned on during normal operation;The power rating should be high enough to withstand the power loss under the condition of possible overvoltage;Reverse breakdown voltage can provide protection when the power supply is reversed, to avoid damaging the subsequent circuit.

[0029] Zener diode D1 is connected with capacitor C12 in parallel, and capacitor C12 is used for smoothing voltage fluctuation and reducing noise.

[0030] The two ends of capacitor C12 are connected with the terminal 1 and the terminal 2 of common mode filter L7 respectively, the voltage across capacitor C12 is the same as the voltage at the input end of common mode filter L7, and the input end of common mode filter L7 is used for connecting the power input end. Common mode filter L7 is used for suppressing common mode interference, improving power quality, reducing radiation interference, enhancing system anti-interference ability and improving electromagnetic compatibility (EMC).

[0031] The use of common mode filter L7 in the power input end is mainly to suppress electromagnetic interference (EMI) and improve the power quality of power supply.

[0032] The output terminal 4 of common mode filter L7 is connected to the positive electrode of capacitor C11, and the output terminal 3 of common mode filter L7 is connected to the negative electrode of capacitor C11. Capacitor C11 is used for further filtering the common mode interference that cannot be completely suppressed by the output end of common mode filter L7 and stabilizing the power voltage.

[0033] Capacitor C11 is connected in parallel with capacitor C115, which is used to enhance the filtering effect. The negative pole of capacitor C115 is connected to ground, providing a stable reference potential point and reducing interference in the circuit.

[0034] The positive pole of capacitor C11 is connected in series with the first end of sampling resistor R20, and the two ends of sampling resistor R20 are connected in parallel with measurement chip U4.

[0035] The first end of sampling resistor R20 is connected to the input terminal Vin+ of measurement chip U4, and the second end of sampling resistor R20 is connected to the input terminal Vin- of measurement chip U4. Since the input terminal Vin+ and the input terminal Vin- are differential inputs, sampling resistor R20 is used to provide a current path so that measurement chip U4 can measure the differential voltage generated by the current passing through sampling resistor R20. Sampling resistor R20 acts as a current sensing resistor here, which generates a voltage drop proportional to the current when current passes through it. This voltage drop is captured and amplified by the differential input terminals of measurement chip U4.

[0036] Measurement chip U4 uses current measurement chip INA138. INA138 measurement chip is a high-precision, low-noise instrumentation amplifier. It is commonly used to amplify differential signals and suppress common-mode signals.

[0037] Current measurement chip INA138 is a single-ended current monitor for high-side current measurement, which can convert a differential input voltage into a current output, and this current is converted back into a voltage using an external load resistor with a settable gain range of 1 to 100 or more. Current measurement chip INA138 chip usually contains the following pins:

[0038] Vin+: differential input positive terminal, used to receive the positive voltage signal generated by the current to be measured.

[0039] Vin-: differential input negative terminal, used to receive the negative voltage signal generated by the current to be measured.

[0040] V+: power voltage input terminal, used to provide working voltage for the chip.

[0041] GND: ground terminal, providing a stable potential reference point for the chip.

[0042] OUT: output terminal, outputting the amplified current or voltage signal.

[0043] The input terminal V+ of measurement chip U4 is connected to a 3.3V working voltage.

[0044] The input terminal GND of measurement chip U4 is grounded, providing a stable potential reference point for measurement chip U4.

[0045] The input end V+ of the measuring chip U4 is connected with the input end GND through a capacitor C15, which is used for filtering to reduce the influence of the fluctuation and noise of the power supply voltage on the performance of the measuring chip U4.

[0046] The second end of the sampling resistor R20 is connected with the positive electrode of a diode D15, which is a Schottky diode; the negative electrode of the diode D15 is connected with an output voltage, such as a 24V voltage, and the value of the output voltage depends on the value of the input voltage of the connector J3; if the input voltage of the connector J3 is 24V, the output voltage at the negative electrode of the diode D15 is 24V, and if the input voltage is other values, the output voltage will also change with the input voltage.

[0047] The main purpose of connecting the diode D15 in series with the voltage output end is to protect the circuit and prevent reverse current. The rated current of the diode D15 should be greater than or equal to the maximum current that may flow in the circuit to avoid damage to the diode due to overcurrent; the reverse breakdown voltage of the diode D15 should be higher than the output voltage to ensure that it will not be turned on under normal working conditions. Selecting a diode with a small forward voltage drop (such as a Schottky diode) can reduce the power loss of the power supply output and improve efficiency. If there is a high-frequency signal in the circuit, a fast recovery diode with a short recovery time should be selected to avoid affecting the signal.

[0048] The output end OUT of the measuring chip U4 is connected with an operational amplifier U11, the positive input end of the operational amplifier U11 is connected with the output end of the measuring chip U4, and the reverse input end of the operational amplifier U11 is connected in feedback with the output end of the operational amplifier U11. The operational amplifier U11 serves as a signal follower.

[0049] The operational amplifier U11 adopts a voltage follower operational amplifier TLV333, which is a zero drift CMOS operational amplifier produced by Texas Instruments (TI),

[0050] The first end of a load resistor R13 is connected at the connection node between the positive input end of the operational amplifier U11 and the output end OUT of the measuring chip U4, and the second end of the load resistor R13 is grounded. The load resistor R13 serves as a part of the input circuit of the operational amplifier U11 and determines the voltage division of the input signal together with the internal input impedance of the operational amplifier U11. The load resistor R13 and the internal resistors of the input end Vin+ and Vin- of the measuring chip U4 constitute an amplification factor, so as to realize the amplification of the input signal, and then the signal follower composed of the operational amplifier U11.

[0051] The output end of the operational amplifier U11 is connected with the negative pole of the stabilizing tube D38, and the positive pole of the stabilizing tube D38 is grounded. The stabilizing tube D38 is used for protecting the operational amplifier U11 from high output voltage. When the output voltage of the operational amplifier U11 exceeds the breakdown voltage of the stabilizing tube D38, the stabilizing tube D38 will be turned on and the voltage will be limited near the breakdown voltage.

[0052] The other way of the output end of the operational amplifier U11 is connected to the AD converter input end EXTISENSE of the single-chip microcomputer, so as to provide the analog signal input for the single-chip microcomputer.

[0053] The working voltage of the operational amplifier U11 is 3.3V, and the working voltage input end of the operational amplifier U11 is connected with the first end of the capacitor C112, and the second end of the capacitor C112 is grounded. The capacitor C112 is used for smoothing the power supply voltage and reducing the influence of the power supply noise on the performance of the operational amplifier U11.

[0054] Working principle:

[0055] The power supply is input through the connector J3, and first passes through the voltage stabilizing diode D1 for voltage stabilization.

[0056] The stabilized voltage passes through the capacitor C12 for smoothing and then enters the common-mode filter L7 for common-mode interference suppression.

[0057] The filtered voltage is further filtered through the capacitors C11 and C115, so as to stabilize the power supply voltage.

[0058] When the current flows through the sampling resistor R20, a voltage drop proportional to the current will be generated. The voltage drop is captured and amplified by the differential input end of the measurement chip U4;

[0059] The operational amplifier U11 receives the output signal of the measurement chip U4 and further amplifies the output signal;

[0060] The output signal of the operational amplifier U11 is sent to the AD converter input end of the single-chip microcomputer. The single-chip microcomputer converts the analog signal into a digital signal through the AD converter;

[0061] The whole circuit generates the voltage drop by accurately measuring the current flowing through the sampling resistor R20, and uses the high-precision instrument amplifier INA138 and the operational amplifier U11 for signal amplification and conversion, so as to finally convert the analog signal into a digital signal for the single-chip microcomputer processing. The stabilizing tube, capacitor and resistor and other components in the circuit jointly ensure the stability and accuracy of the circuit.

[0062] In one specific embodiment:

[0063] The gain GAIN of the operational amplifier U11 is 20; and the resistance value of the sampling resistor R20 is 0.01Ω;

[0064] The voltage output load resistor R13 is 100KΩ; the voltage follower operational amplifier TLV333;

[0065] When the working current in the circuit flows through the sampling resistor R20, a voltage difference will be generated on the sampling resistor R20,

[0066] The voltage across the sampling resistor R20 is Vin+-Vin-, and if the current flowing through the sampling resistor R20 is Is, then the voltage across the sampling resistor R20 is Vr20=Is x 0.01;

[0067] When the load resistor R13 is connected with the resistor of 100KΩ, the internal gain GAIN of the measurement chip U4 is 20, and the output voltage of the measurement chip U4 is Is x 0.01 x 20;

[0068] The operational amplifier U11 is the voltage follower operational amplifier TLV333, and the output signal EXT_ISENSE of the operational amplifier U11 is still Is x 0.01 x 20.

[0069] If the current Is flowing through the sampling resistor R20 is 10A, then the output voltage of the EXT_ISENSE signal is 10 x 0.01 x 20 = 2V, that is, the signal entering the single-chip microcomputer AD is 2V.

[0070] In a specific embodiment, if the integrated measurement chip U4 is not used, a discrete operational amplifier and a triode or MOS tube can also be used to build this circuit.

[0071] In a specific embodiment, the type of the current measurement chip is TP181A1, and at this time, the sampling resistor can be adjusted, and the same output voltage as the current measurement chip INA138 can be obtained under the same condition.

[0072] The above technical features constitute the best embodiment of the present application, which has strong adaptability and the best implementation effect, and unnecessary technical features can be added or reduced according to actual needs to meet the needs of different situations.

[0073] Finally, it should be noted that the above content is only used to illustrate the technical scheme of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical scheme of the present application made by those skilled in the art do not deviate from the essence and scope of the technical scheme of the present application.

Claims

1. A total current measuring circuit, characterized in that, Includes a current measurement and conversion module, and a signal processing and amplification module; The current measurement and conversion module includes a common-mode filter L7, the input terminal of which is connected to the power input terminal; a capacitor C11, the terminal 4 of the common-mode filter L7 is connected to the positive terminal of the capacitor C11, and the terminal 3 of the common-mode filter L7 is connected to the negative terminal of the capacitor C11; and a sampling resistor R20, the positive terminal of the capacitor C11 is connected in series with the first terminal of the sampling resistor R20, and the two ends of the sampling resistor R20 are connected to a signal processing and amplification module. The sampling resistor R20 is used to provide a current path for the signal processing and amplification module. The signal processing and amplification module includes a measurement chip U4, with sampling resistor R20 connected to the input terminals Vin+ and Vin- of the measurement chip U4, respectively. The measurement chip U4 can measure the differential voltage generated by the current passing through the sampling resistor R20. The output terminal of the measurement chip U4 is connected to an operational amplifier U11, which is an inverting operational amplifier. The non-inverting input terminal of the operational amplifier U11 is connected to a grounded load resistor R13. The value of the load resistor R13 divided by the internal resistances of the input terminals Vin+ and Vin- of the measurement chip U4 constitutes the amplification factor, thereby amplifying the input signal. The signal then passes through a signal follower composed of the operational amplifier U11. The output of operational amplifier U11 is connected to the input of the microcontroller's AD converter.

2. The total current measuring circuit according to claim 1, characterized in that, Capacitor C11 is connected in parallel with capacitor C115.

3. The total current measuring circuit according to claim 1, characterized in that, The sampling resistor R20 is also connected to the positive terminal of diode D15, and the negative terminal of diode D15 is connected to the output voltage.

4. The total current measuring circuit according to claim 3, characterized in that, The output voltage of the negative terminal of diode D15 is 24V.

5. The total current measuring circuit according to claim 4, characterized in that, The measurement chip U4 uses the current measurement chip INA138.

6. The total current measuring circuit according to claim 5, characterized in that, The output terminal OUT of the measurement chip U4 is connected to the operational amplifier U11. The positive input terminal of the operational amplifier U11 is connected to the output terminal of the measurement chip U4, and the inverting input terminal of the operational amplifier U11 is connected to the output terminal of the operational amplifier U11 as feedback.

7. The total current measuring circuit according to claim 6, characterized in that, Operational amplifier U11 uses voltage follower op-amp TLV333.

8. The total current measuring circuit according to claim 7, characterized in that, One output terminal of operational amplifier U11 is connected to the negative terminal of Zener diode D38, and the positive terminal of Zener diode D38 is grounded.

9. The total current measuring circuit according to claim 8, characterized in that, The total current measurement circuit includes connector J3, which serves as the input point of the circuit. A Zener diode D1 is connected between terminals 1 and 3 of connector J3, with the positive terminal of Zener diode D1 connected to terminal 3 of connector J3 and the negative terminal of Zener diode D1 connected to terminal 1 of connector J3.

10. The total current measuring circuit according to claim 9, characterized in that, A Zener diode D1 is connected in parallel with a capacitor C12. The two ends of capacitor C12 are connected to terminals 1 and 2 of the common-mode filter L7, respectively.

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