Alternating voltage acquisition circuit and voltage monitoring equipment comprising same

Abstract

The utility model provides an AC voltage acquisition circuit and a voltage monitoring device comprising the same, and the AC voltage acquisition circuit comprises a current-limiting protection circuit, a mutual inductor circuit, a voltage conversion circuit, a second-order active filter circuit, a signal rectification circuit and a sampling signal output circuit which are connected in sequence. The signal rectification circuit comprises an operational amplifier chip U3, an operational amplifier chip U4, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a diode D1, a diode D2, a capacitor C11 and the like. The voltage monitoring equipment comprises a main controller and a plurality of alternating current voltage acquisition circuits connected with the main controller, wherein the alternating current voltage acquisition circuits are the alternating current voltage acquisition circuits. Therefore, the isolation filtering circuit not only has isolation filtering effects, but also has high linearity of output waveforms, and is convenient for follow-up processing.

Description

Technical Field

[0001] The utility model relates to the technical field of signal acquisition, in particular to an AC voltage acquisition circuit and a voltage monitoring device comprising the circuit. Background Art

[0002] AC voltage acquisition is an indispensable component of the industrial control field. It is used to collect the output voltage values ​​of various power supply devices in real time. It is one of the key technologies for ensuring the stable operation of power supply equipment, monitoring the status of the power system, and performing fault diagnosis and preventive maintenance. It should be noted that existing AC voltage acquisition circuits generally use a rectifier bridge method for signal processing. For example, Chinese patent application number 202221162015.4 discloses an AC voltage segmented sampling circuit. The circuit includes a rectifier amplifier module, which uses a rectifier bridge. Due to the presence of the dead zone voltage of the diodes in the rectifier bridge, the linearity of the AC voltage acquisition circuit is poor, and the sampled waveform is not conducive to acquisition by the microcontroller ADC.

[0003] It should also be noted that in the railway disaster prevention environment, high-frequency electromagnetic interference is an important consideration because it may have a significant impact on the accuracy and stability of the voltage acquisition circuit, but some existing voltage acquisition circuits lack filtering functions.

[0004] It should also be noted that the logic level of the existing AC voltage acquisition circuit cannot be set, and it can usually only meet the use of a single-chip microcomputer of one voltage level, and its versatility is poor. For example, the Chinese patent application number 201521110827.4 contains an AC voltage conversion branch including the secondary coil of the current transformer T1, the resistor R2 and the capacitor C1 in sequence.

[0005] In order to solve the above problems, people have been seeking an ideal technical solution. Summary of the Invention

[0006] The purpose of the utility model is to address the deficiencies of the prior art and thus provide an AC voltage acquisition circuit and a voltage monitoring device comprising the circuit.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides an AC voltage acquisition circuit, which includes a current limiting protection circuit, a mutual inductor circuit, a voltage conversion circuit, a second-order active filter circuit, a signal rectification circuit and a sampling signal output circuit connected in sequence, wherein the mutual inductor circuit adopts a current transformer;

[0008] The signal rectifier circuit includes an operational amplifier chip U3, an operational amplifier chip U4, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a diode D1, a diode D2 and a capacitor C11; the positive input terminal of the operational amplifier chip U3 is connected to the ground terminal through the resistor R9, the negative input terminal of the operational amplifier chip U3 is respectively connected to one end of the resistor R10, the cathode of the diode D1 and one end of the resistor R11, and the other end of the resistor R10 is respectively connected to one end of the resistor R13 and the output end of the second-order active filter circuit; the anode of the diode D1 is respectively connected to the output end of the operational amplifier chip U3 and the cathode of the diode D2, and the other end of the resistor R11 is respectively connected to one end of the resistor R12 and the anode of the diode D2;

[0009] The positive input terminal of the operational amplifier chip U4 is connected to the ground terminal through the resistor R14, and the negative input terminal of the operational amplifier chip U4 is respectively connected to the other end of the resistor R12 and the other end of the resistor R13; the resistor R15 and the capacitor C11 are connected in parallel between the negative input terminal of the operational amplifier chip U4 and the output terminal of the operational amplifier chip U4.

[0010] In order to achieve the above-mentioned purpose, the second aspect of the present invention provides a voltage monitoring device, which includes a main controller and also includes several AC voltage acquisition circuits connected to the main controller, and the AC voltage acquisition circuit is the above-mentioned AC voltage acquisition circuit.

[0011] The beneficial effects of the utility model are:

[0012] 1) This utility model proposes an AC voltage acquisition circuit that uses an operational amplifier chip and resistors instead of a rectifier bridge. This circuit will not cause waveform clipping due to the presence of dead-zone voltage, and the sampled signal has high linearity, which can maintain linear integrity when acquiring a wide voltage range.

[0013] 2) The utility model can effectively filter signals through a second-order active filter circuit to meet the high-frequency electromagnetic interference environment in railway disaster prevention environments;

[0014] 3) The utility model adopts an adjustable voltage conversion circuit and uses potentiometer R7 to achieve adjustable logic level, thereby making the AC voltage acquisition circuit more versatile and able to meet the use of single-chip microcomputers with different voltage levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the circuit structure of the AC voltage acquisition circuit of the present utility model;

[0016] Figure 2 This is a circuit schematic diagram of the AC voltage acquisition circuit of the utility model;

[0017] Figure 3 This is a schematic diagram of the circuit structure of the voltage monitoring device of the utility model;

[0018] Figure 4 It is a circuit principle diagram of the DC voltage acquisition circuit of the utility model. DETAILED DESCRIPTION

[0019] The technical solution of the present utility model is further described in detail below through specific implementation methods.

[0020] Example 1

[0021] As shown in Figures 1 and 2 Figure 2 As shown, this embodiment provides a specific implementation of an AC voltage acquisition circuit;

[0022] The AC voltage acquisition circuit includes a current limiting protection circuit, a mutual inductor circuit, a voltage conversion circuit, a second-order active filter circuit, a signal rectification circuit and a sampling signal output circuit connected in sequence, and the mutual inductor circuit adopts a current mutual inductor;

[0023] As attached Figure 2 As shown, the signal rectifier circuit includes an operational amplifier chip U3, an operational amplifier chip U4, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a diode D1, a diode D2 and a capacitor C11; the positive input terminal of the operational amplifier chip U3 is connected to the ground terminal through the resistor R9, the negative input terminal of the operational amplifier chip U3 is respectively connected to one end of the resistor R10, the cathode of the diode D1 and one end of the resistor R11, and the other end of the resistor R10 is respectively connected to one end of the resistor R13 and the output end of the second-order active filter circuit; the anode of the diode D1 is respectively connected to the output end of the operational amplifier chip U3 and the cathode of the diode D2, and the other end of the resistor R11 is respectively connected to one end of the resistor R12 and the anode of the diode D2;

[0024] The positive input terminal of the operational amplifier chip U4 is connected to the ground terminal through the resistor R14, and the negative input terminal of the operational amplifier chip U4 is respectively connected to the other end of the resistor R12 and the other end of the resistor R13; the resistor R15 and the capacitor C11 are connected in parallel between the negative input terminal of the operational amplifier chip U4 and the output terminal of the operational amplifier chip U4.

[0025] It should be noted that traditional diode rectifiers have a dead-zone voltage. When the input signal amplitude is small, this dead-zone voltage may cause the rectified waveform to be clipped. To solve this problem, the signal rectification circuit in the AC voltage acquisition circuit uses the nonlinear characteristics of the operational amplifier chip U3 and the operational amplifier chip U4 (such as working in the saturation zone) to realize the rectification function, which can realize the rectification and filtering of the sampled AC signal, and will not cause the waveform to be clipped due to the dead-zone voltage. This effectively solves the problem of the dead-zone voltage of the diode when using the rectifier bridge solution.

[0026] It should also be noted that the (small) signal rectifier circuit also completes the conversion of AC signals into DC signals through hardware circuits, and makes the voltage signal input to the controller ADC port by the sampling signal output circuit an effective voltage value and a DC voltage, which is convenient for controller sampling, thereby eliminating the need for the controller to enter interrupt sampling at a high frequency. Therefore, the utility model does not require complex integration processing in software, nor does it require support from high-performance hardware processors to complete AC effective value sampling.

[0027] It should also be noted that the AC voltage signal is a sinusoidal wave, which is divided into two cycles. During the positive half-cycle, diode D1 is turned off and diode D2 is turned on, according to the principle of "virtual disconnection" during negative feedback in the operational amplifier. This causes the voltage at the anode of diode D2 and the voltage on the left side of resistor R10 to be equal, but in opposite directions. This in turn activates the inverting proportional circuit of operational amplifier chip U4, causing the voltage at U4's output terminal to be the same magnitude and direction as the voltage at the input of resistor R10. During the negative half-cycle, diode D1 is turned on and diode D2 is turned off. Current flows from the left side of resistor R10 through resistors R13 and R15 to the output terminal. U4's inverting proportional circuit causes the voltage at U4's output terminal to be opposite in magnitude and direction to the voltage at the input of resistor R10. This is the negative half-cycle, and the output is a positive voltage. Therefore, during both half-cycles, capacitor C11 filters the signal to form a smooth DC voltage. This results in a highly linear output signal from the signal rectifier circuit, maintaining linear integrity during wide voltage acquisition.

[0028] It should also be noted that the current limiting protection circuit is used to limit the input current of the transformer circuit, the transformer circuit is used to convert the current input to the current limiting protection circuit into a voltage signal and perform electrical isolation, the voltage conversion circuit is used to perform voltage conversion on the voltage signal output by the transformer circuit, the second-order active filter circuit is used to filter the voltage signal after voltage conversion, and the signal rectifier circuit is used to rectify the voltage signal after filtering.

[0029] In some embodiments, as shown in the attached Figure 2As shown, the current limiting protection circuit includes a current limiting resistor R1, a current limiting resistor R2, a current limiting resistor R3, a current limiting resistor R4 and a transient suppression diode TV1, one end of the current limiting resistor R1 serves as a sampling voltage input positive terminal, and one end of the current limiting resistor R2 serves as a sampling voltage input negative terminal;

[0030] The other end of the current limiting resistor R1 is respectively connected to one end of the current limiting resistor R3 and one end of the transient suppression diode TV1, and the other end of the current limiting resistor R2 is respectively connected to one end of the current limiting resistor R4 and the other end of the transient suppression diode TV1;

[0031] The other end of the current limiting resistor R3 and the other end of the current limiting resistor R4 are respectively connected to the mutual inductor circuit.

[0032] It should be noted that actual railway applications involve complex electromagnetic interference environments, and the input voltage is not a standard sinusoidal signal; it may contain spikes or instantaneous high currents. The transient suppression diode TV1 protects the downstream circuit from damage when subjected to current and voltage shocks. The current-limiting protection circuit uses current-limiting resistors in the upstream stage to ensure that the sampled voltage meets the transformer input current. The four current-limiting resistors can limit the current passing through a certain part to prevent excessive current from damaging components. Therefore, the current-limiting protection circuit not only ensures that the sampled voltage meets the transformer input current but also improves the protection performance of the entire circuit.

[0033] In some embodiments, as shown in the attached Figure 2 As shown, the voltage conversion circuit is an adjustable voltage conversion circuit, which includes an operational amplifier chip U1, a resistor R5 and a potentiometer R7. The positive input end of the operational amplifier chip U1 is connected to one of the output ends of the mutual inductor circuit, and the negative input end of the operational amplifier chip U1 is respectively connected to the other output end of the mutual inductor circuit and one end of the potentiometer R7. The other end of the potentiometer R7 is connected to the output end of the operational amplifier chip U1 through the resistor R5.

[0034] It should be noted that the adjustable voltage conversion circuit utilizes the high input impedance of the operational amplifier to convert the tiny current signal output by the transformer into a voltage signal, thus achieving voltage conversion. The adjustable voltage conversion circuit also utilizes potentiometer R7 to enable adjustable logic levels, allowing it to be used with microcontrollers of different voltage levels, making the AC voltage acquisition circuit more versatile.

[0035] Specifically, the potentiometer R7 is a synthetic top adjustment potentiometer with a maximum value of 1K, which can convert 1mA current into 1V voltage.

[0036] In some embodiments, as shown in the attached Figure 2As shown, the second-order active filter circuit includes an operational amplifier chip U2, a resistor R6, a resistor R8, a capacitor C3 and a capacitor C4, the positive input terminal of the operational amplifier chip U2 is connected to one end of the resistor R8 and one end of the capacitor C4 respectively, the negative input terminal of the operational amplifier chip U2 is connected to the output terminal of the operational amplifier chip U2, and the other end of the capacitor C4 is connected to the ground terminal;

[0037] The other end of the resistor R8 is connected to one end of the resistor R6 and one end of the capacitor C3 respectively. The other end of the resistor R6 is connected to the output end of the adjustable voltage conversion circuit. The other end of the capacitor C3 is connected to the output end of the operational amplifier chip U2.

[0038] It should be noted that the cutoff frequency calculation formula for the second-order active filter circuit is f=1 / 2πRC. Depending on the resistor and capacitor combination, it can effectively filter out clutter above a certain frequency, meeting the high-frequency electromagnetic interference requirements of railway disaster prevention. For example, when using a 10K resistor and a 100nF capacitor, the cutoff frequency is 340Hz, and any input signal above 340Hz is blocked.

[0039] In some embodiments, as shown in the attached Figure 2 As shown, the sampling signal output circuit includes an operational amplifier chip U5, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a magnetic bead L1, a voltage regulator Z1 and a capacitor C14. The positive input terminal of the operational amplifier chip U5 is connected to the output terminal of the signal rectifier circuit through the resistor R16, and the negative input terminal of the operational amplifier chip U5 is connected to the ground terminal through the resistor R17. The negative input terminal of the operational amplifier chip U5 is also connected to the output terminal of the operational amplifier chip U5 through the resistor R18.

[0040] The output end of the operational amplifier chip U5 is connected to one end of the magnetic bead L1 through the resistor R19, and the other end of the magnetic bead L1 serves as the output end of the sampling signal output circuit;

[0041] The voltage regulator Z1 and the capacitor C14 are connected in parallel between the other end of the magnetic bead L1 and the ground end.

[0042] It should be noted that the sampling signal output circuit uses the operational amplifier chip U5, resistor R16, resistor R17 and resistor R18 to form a common-mode proportional operational amplifier circuit, uses the operational amplifier chip U5 and the like to amplify the output signal, uses the magnetic bead L1 to further filter out the noise in the output signal, and uses the voltage regulator tube Z1 and capacitor C14 to stabilize and filter the output signal, thereby further adjusting the sampling signal, realizing the protection of the single-chip microcomputer IO, and facilitating the collection of voltage signals.

[0043] Example 2

[0044] Based on Example 1, this example provides a specific implementation of a voltage monitoring device;

[0045] The voltage monitoring device includes a main controller and a plurality of AC voltage acquisition circuits connected to the main controller. The AC voltage acquisition circuit is the AC voltage acquisition circuit in Example 1.

[0046] It should be noted that the AC voltage acquisition circuit uses a hardware circuit to make the output voltage a scaled-down voltage of the front-end input voltage. The specific scale-down ratio can be determined according to the device parameters and will not be described here. If the effective value of the front-end input voltage is 220V, the output voltage of the AC voltage acquisition circuit is 0.22V.

[0047] Specifically, the main controller may be STM32F103RC, or other controllers with ADC sampling function.

[0048] In some embodiments, the voltage monitoring device further includes a plurality of DC voltage acquisition circuits connected to the main controller, such as the attached Figure 3 shown.

[0049] In some embodiments, as shown in the attached Figure 4 As shown, the DC voltage acquisition circuit includes a DC voltage input protection circuit, a voltage sensor T1, a voltage follower, a filter circuit and an output circuit connected in sequence;

[0050] The DC voltage input protection circuit includes a resistor R20, a resistor R21, a resistor R22, a resistor R23 and a transient suppression diode TV2. The principle is similar to that of the current limiting protection circuit in the AC voltage acquisition circuit and will not be repeated here.

[0051] The voltage sensor T1 is a V121G27 element type AC / DC universal voltage sensor, which is used to collect DC voltage signals to obtain standardized and electrically isolated voltage signals;

[0052] The voltage follower includes an operational amplifier chip U6, a resistor R30, a capacitor C15, and a capacitor C16. The positive input terminal of the operational amplifier chip U6 is connected to the voltage sensor T1 and one end of the resistor 30 respectively, the other end of the resistor R30 is grounded, and the negative input terminal of the operational amplifier chip U6 is connected to the output terminal of the operational amplifier chip U6.

[0053] The filtering circuit includes an operational amplifier chip U7, a resistor R24, a resistor R25, a capacitor C18, a capacitor C19 and a capacitor C20, and is used to filter the voltage signal output by the voltage follower. The principle is similar to that of the second-order active filtering circuit in the AC voltage acquisition circuit, and will not be repeated here;

[0054] The output circuit includes an operational amplifier chip U8, resistors R26, R27, R28, R29, a magnetic bead L2, a voltage regulator Z2 and a capacitor C23. The operational amplifier chip U8 is used to amplify the output signal, and the magnetic bead L2 is used to further filter out high-frequency noise in the output signal. The voltage regulator Z2 is used to prevent damage to the ADC port when the acquisition voltage is abnormally high.

[0055] It should be noted that the number of AC voltage acquisition circuits and DC voltage acquisition circuits in the voltage monitoring device is not limited to the following. Figure 3 As shown, adaptive adjustment can be made according to actual conditions and the selected main controller model.

[0056] It should also be noted that the voltage monitoring equipment not only has an AC voltage sampling function but also a DC voltage sampling function, and the monitored power supply equipment can be an AC power supply or a DC power supply; therefore, the voltage monitoring equipment can be used as an online voltage monitoring equipment for mains power, UPS (Uninterruptible Power Supply), foreign power grid, meteorological collection equipment, switch monitoring equipment, etc. It has high real-time performance, no voltage collection lag, and is convenient for subsequent processing.

[0057] It should also be noted that if the voltage monitoring device cannot collect voltage or the voltage is abnormal (such as not within the preset range), the disaster prevention terminal will alarm.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model and not to limit it; although the utility model is described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the utility model can still be modified or some technical features can be replaced by equivalents; without departing from the spirit of the technical solution of the utility model, they should all be included in the scope of the technical solution for protection of the utility model.

Claims

1. An AC voltage acquisition circuit, characterized in that: It includes a current limiting protection circuit, a mutual inductor circuit, a voltage conversion circuit, a second-order active filter circuit, a signal rectification circuit and a sampling signal output circuit connected in sequence, wherein the mutual inductor circuit adopts a current mutual inductor; The signal rectifier circuit includes an operational amplifier chip U3, an operational amplifier chip U4, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a diode D1, a diode D2 and a capacitor C11; the positive input terminal of the operational amplifier chip U3 is connected to the ground terminal through the resistor R9, the negative input terminal of the operational amplifier chip U3 is respectively connected to one end of the resistor R10, the cathode of the diode D1 and one end of the resistor R11, and the other end of the resistor R10 is respectively connected to one end of the resistor R13 and the output end of the second-order active filter circuit; the anode of the diode D1 is respectively connected to the output end of the operational amplifier chip U3 and the cathode of the diode D2, and the other end of the resistor R11 is respectively connected to one end of the resistor R12 and the anode of the diode D2; The positive input terminal of the operational amplifier chip U4 is connected to the ground terminal through the resistor R14, and the negative input terminal of the operational amplifier chip U4 is respectively connected to the other end of the resistor R12 and the other end of the resistor R13; the resistor R15 and the capacitor C11 are connected in parallel between the negative input terminal of the operational amplifier chip U4 and the output terminal of the operational amplifier chip U4.

2. The AC voltage acquisition circuit according to claim 1, characterized in that: The current limiting protection circuit includes a current limiting resistor R1, a current limiting resistor R2, a current limiting resistor R3, a current limiting resistor R4 and a transient suppression diode TV1, one end of the current limiting resistor R1 is used as the sampling voltage input positive terminal, and one end of the current limiting resistor R2 is used as the sampling voltage input negative terminal; The other end of the current limiting resistor R1 is respectively connected to one end of the current limiting resistor R3 and one end of the transient suppression diode TV1, and the other end of the current limiting resistor R2 is respectively connected to one end of the current limiting resistor R4 and the other end of the transient suppression diode TV1; The other end of the current limiting resistor R3 and the other end of the current limiting resistor R4 are respectively connected to the mutual inductor circuit.

3. The AC voltage acquisition circuit according to claim 1 or 2, characterized in that: The voltage conversion circuit is an adjustable voltage conversion circuit, which includes an operational amplifier chip U1, a resistor R5 and a potentiometer R7. The positive input end of the operational amplifier chip U1 is connected to one of the output ends of the mutual inductor circuit, and the negative input end of the operational amplifier chip U1 is respectively connected to the other output end of the mutual inductor circuit and one end of the potentiometer R7. The other end of the potentiometer R7 is connected to the output end of the operational amplifier chip U1 through the resistor R5.

4. The AC voltage acquisition circuit according to claim 3, characterized in that: The second-order active filter circuit includes an operational amplifier chip U2, a resistor R6, a resistor R8, a capacitor C3, and a capacitor C4. The positive input terminal of the operational amplifier chip U2 is connected to one end of the resistor R8 and one end of the capacitor C4, respectively. The negative input terminal of the operational amplifier chip U2 is connected to the output terminal of the operational amplifier chip U2. The other end of the capacitor C4 is connected to the ground terminal. The other end of the resistor R8 is connected to one end of the resistor R6 and one end of the capacitor C3 respectively. The other end of the resistor R6 is connected to the output end of the adjustable voltage conversion circuit. The other end of the capacitor C3 is connected to the output end of the operational amplifier chip U2.

5. The AC voltage acquisition circuit according to claim 4, characterized in that: The sampling signal output circuit includes an operational amplifier chip U5, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a magnetic bead L1, a voltage regulator Z1 and a capacitor C14. The positive input terminal of the operational amplifier chip U5 is connected to the output terminal of the signal rectifier circuit through the resistor R16, and the negative input terminal of the operational amplifier chip U5 is connected to the ground terminal through the resistor R17. The negative input terminal of the operational amplifier chip U5 is also connected to the output terminal of the operational amplifier chip U5 through the resistor R18. The output end of the operational amplifier chip U5 is connected to one end of the magnetic bead L1 through the resistor R19, and the other end of the magnetic bead L1 serves as the output end of the sampling signal output circuit; The voltage regulator Z1 and the capacitor C14 are connected in parallel between the other end of the magnetic bead L1 and the ground end.

6. A voltage monitoring device, characterized in that: The main controller also includes several AC voltage acquisition circuits connected to the main controller, and the AC voltage acquisition circuit is the AC voltage acquisition circuit according to any one of claims 1 to 5.

7. The voltage monitoring device according to claim 6, characterized in that: It also includes several DC voltage acquisition circuits connected to the main controller.

8. The voltage monitoring device according to claim 7, wherein: The DC voltage acquisition circuit includes a DC voltage input protection circuit, a voltage sensor T1, a voltage follower, a filter circuit and an output circuit which are connected in sequence.

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