A strong current non-isolated detection method

Abstract

The application discloses a strong current non-isolation detection method, and belongs to the technical field of current detection, and specifically comprises the following steps: establishing a current measurement circuit, wherein the current measurement circuit comprises an isolation switch power supply, a resistance group, an operational amplifier and a single-chip microcomputer; a firewire or a zero line of a strong current circuit is split into two branch lines, the branch lines are respectively short-circuited with ground wires of the isolation switch power supply, the resistance group is connected in series in the branch lines, and the equivalent resistances of the resistance group in the two branch lines are different; a voltage signal after voltage division of the resistance group is acquired through the operational amplifier, the operational amplifier offsets and amplifies the voltage signal and outputs the voltage signal to an A / D interface of the single-chip microcomputer, the single-chip microcomputer acquires the effective value of the voltage signal through the numerical value of the A / D interface, so that the current value of the strong current circuit is calculated; and the single-chip microcomputer outputs the current value signal to an LED display screen; and the application realizes simple and low-cost detection of the strong current.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current detection, in particular to a strong current non-isolated detection method. BACKGROUND

[0002] Strong current is mainly a kind of power transmission property, generally refers to the power supply system, lighting system and other power supply systems, strong current is the power source of all power equipment, the characteristics are large power, large current and low frequency, mainly considering the problems of small loss and high efficiency, and common household appliances also belong to strong current equipment.

[0003] Since strong current involves high voltage, in order to ensure safety, the existing technology adopts the method of current transformer isolation to realize the detection of strong current, however, due to the existence of load resistance, core loss, and primary and secondary DC resistance, the loss of the current transformer will cause the loss of part of the energy, thereby causing the measurement error of the current, the circuit of the existing strong current detection technology is relatively complex, the cost of the detection device is high, and it is not suitable for circuit system and electric appliance detection in conventional environment. SUMMARY

[0004] The purpose of the present application is to provide a strong current non-isolated detection method, which solves the following technical problems:

[0005] For circuit system and electric appliance detection in conventional environment, the existing isolated current detection technology circuit is relatively complex and has high cost.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A strong current non-isolated detection method, comprising the following steps:

[0008] Establish a current measurement circuit, the current measurement circuit comprises an isolated switch power supply, a resistance group, an operational amplifier and a single-chip microcomputer;

[0009] The live wire or the zero line of the strong current circuit is split into two branch lines ACL1 and ACL2, the branch lines are respectively short-circuited with the ground wire of the isolated switch power supply, and a resistance group is connected in series in the branch lines, and the equivalent resistance of the resistance group in the two branch lines is different;

[0010] The voltage signals of ACL1 and ACL2 after voltage division by the resistance group are obtained through the operational amplifier, and the operational amplifier offsets and amplifies the voltage signals and outputs them to the A / D interface of the single-chip microcomputer;

[0011] The single-chip microcomputer obtains the effective value of the voltage signals through the numerical value of the A / D interface, thereby calculating the current value of the strong current circuit;

[0012] The single-chip microcomputer outputs the current value signal to an LED display screen.

[0013] As a further scheme of the present application: the operational amplifier obtains the voltage signal through the non-inverting input terminal and the inverting input terminal, the voltage signal is amplified by the operational amplifier, the amplification factor is 1 times, the operational amplifier amplifies the negative voltage bias in the voltage signal to a positive voltage, and the operational amplifier buffers and isolates the voltage signal.

[0014] As a further scheme of the present application: after the voltage signal is output by the operational amplifier, the voltage signal is filtered by an RC circuit.

[0015] As a further scheme of the present application: the single-chip microcomputer calculates the effective value of the voltage signal through the numerical value of the A / D interface, calculates the frequency and amplitude of the voltage signal, obtains the effective value of the voltage signal, subtracts the bias voltage superimposed by the operational amplifier from the effective value to obtain a difference value, multiplies the difference value by a voltage reduction coefficient to obtain the voltage effective value of ACL1 and ACL2, and obtains the current value according to Ohm's law.

[0016] As a further scheme of the present application: the resistance groups are replaced several times, the sum of the equivalent resistances of the resistance groups in the two branch lines remains unchanged, the equivalent resistances of the resistance groups in the single branch line are all different, the current values corresponding to different resistance groups are sequentially obtained, the mean value and the standard deviation of the current values are calculated, the current values within 3 standard deviations above and below the mean value are screened, the screened current values are calculated again, a new mean value of the current values is obtained and output as the current value signal.

[0017] As a further scheme of the present application: the isolating power supply converts the commercial alternating power supply into a low-voltage direct current power supply, the low-voltage direct current power supply outputs a 5V low-voltage direct current power supply through a voltage stabilizer, the 5V low-voltage direct current power supply supplies power to the operational amplifier and the single-chip microcomputer, and the input terminal and the output terminal of the voltage stabilizer are both connected with a smoothing capacitor.

[0018] As a further scheme of the present application: the single-chip microcomputer outputs the current value signal to the LED display screen through optical coupling communication, the optical coupling communication is realized through an optical coupler, when the single-chip microcomputer outputs a low-level signal, the light-emitting diode of the optical coupler is turned on, and the light-emitting diode emits light; when the single-chip microcomputer outputs a high-level signal, the light-emitting diode of the optical coupler is not turned on, and the light-emitting diode does not emit light.

[0019] As a further scheme of the present application: a photosensitive triode is added to the output terminal of the optical coupler, when the light-emitting diode emits light, the photosensitive triode of the output terminal is turned on, and when the light-emitting diode does not emit light, the photosensitive triode of the output terminal is not turned on.

[0020] Advantages of the present application:

[0021] The present application short-circuits the live wire or the zero wire of the strong current circuit with the ground wire of the isolation switch power supply, and then divides the voltage through the resistance, thereby avoiding the danger caused by high voltage, processing the voltage signal using the operational amplifier and the RC circuit, isolating and buffering the voltage signal, eliminating the ripple interference, ensuring the stability of the voltage signal, calculating the effective value of the voltage through the single-chip microcomputer, and finally obtaining the current value of the strong current circuit using the Ohm's law; compared with the existing isolation type current detection technology, the present application has simple structure and low cost, and is suitable for the current detection of the strong current circuit in the conventional scene. BRIEF DESCRIPTION OF DRAWINGS

[0022] The present application will be further described below in combination with the drawings.

[0023] Figure 1 is a flowchart of the present application;

[0024] Figure 2 is a circuit diagram of the ACL1 and the ACL2 of the present application and the isolation switch power supply;

[0025] Figure 3 is a circuit diagram of the voltage stabilizer of the present application;

[0026] Figure 4 is a circuit diagram of the ACL1 and the ACL2 of the present application and the operational amplifier;

[0027] Figure 5 is a circuit diagram of the ACL1 and the ACL2 of the present application and the single-chip microcomputer;

[0028] Figure 6 is a circuit diagram of the optical coupling communication of the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below 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, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0030] Please refer to Figures 1-6 The present application is a strong current non-isolation detection method, which comprises the following steps:

[0031] A current measurement circuit is established, which comprises an isolation switch power supply, a resistance group, an operational amplifier and a single-chip microcomputer;

[0032] The live wire or the zero line of the strong current circuit is split into two branch lines ACL1 and ACL2, the branch lines are respectively short-circuited with the ground wire of the isolating switch power supply, a resistance group is connected in series in the branch lines, and the equivalent resistances of the resistance groups in the two branch lines are different;

[0033] The voltage signals of ACL1 and ACL2 after voltage division by the resistance group are obtained by an operational amplifier, the operational amplifier offsets and amplifies the voltage signals and outputs to an A / D interface of a single-chip microcomputer, the single-chip microcomputer obtains the effective value of the voltage signals through the numerical value of the A / D interface, and thus the current value of the strong current circuit is calculated;

[0034] The single-chip microcomputer outputs the current value signal to an LED display screen.

[0035] Since the strong current involves high voltage, the prior art usually adopts an isolation method such as a current transformer to detect the strong current, however, due to the load resistance, core loss, and the existence of primary and secondary DC resistances, the loss of the current transformer will cause a part of energy to be lost, thus causing errors in the measurement of the current, and due to the relatively complex technology and structure of the current transformer, the cost is high, which limits the use scenarios.

[0036] The live wire or the zero line of the strong current circuit is split into two branch lines, and the branch lines are short-circuited with the ground wire of the isolating switch power supply, the isolating switch power supply is weak current, then the voltage of the strong current is reduced to a safe range through resistance voltage division, then the alternating voltage signal of the strong current is offset and amplified by an operational amplifier, and is isolated and buffered, then the voltage signal is output to an A / D interface of a single-chip microcomputer, thus the effective value of the voltage signal is obtained, and finally the current value of the strong current circuit is calculated, compared with the prior art isolation type current detection technology, the structure is simple, the cost is low, and the current detection is suitable for conventional strong current circuits and strong current appliances.

[0037] In a preferred embodiment of the present application, the operational amplifier obtains the voltage signal through the non-inverting input terminal and the inverting input terminal, the voltage signal is amplified by the operational amplifier, the amplification factor is 1, the operational amplifier offsets and amplifies the negative voltage in the voltage signal into positive voltage, and the operational amplifier buffers and isolates the voltage signal.

[0038] The effective value of the voltage after voltage reduction needs to be within the working voltage (3.3V to 5.5V) of the single-chip microcomputer, the voltage after voltage reduction is differentially amplified, the amplification factor of the differential amplifier is 1, the main function of the differential amplifier is that of a follower, which is a buffer stage, and plays a role in isolation and buffering, the input impedance of the follower is very large, and the output impedance is very small, since the commercial alternating current is a sine wave, there is a negative half cycle, and the voltage of the half cycle is negative, so the overall voltage must be raised, and the overall voltage is raised by adding resistors.

[0039] In one case of the embodiment, the voltage signal is filtered by an RC circuit after being output by the operational amplifier.

[0040] The RC circuit is a circuit composed of a resistor and a capacitor, and the RC circuit can be used to filter signals by blocking some frequencies and passing other frequencies to eliminate ripple interference.

[0041] In another preferred embodiment of the application, the single-chip microcomputer calculates the effective value of the voltage signal through the numerical value of the A / D interface, calculates the frequency and amplitude of the voltage signal, obtains the effective value of the voltage signal, subtracts the bias voltage superimposed by the operational amplifier from the effective value to obtain a difference value, and multiplies the difference value by a voltage reduction coefficient to obtain the voltage effective value of ACL1 and ACL2, and obtains the current value according to Ohm's law.

[0042] Measuring voltage by a single-chip microcomputer is to convert analog quantity into digital quantity, and an A / D (analog-to-digital) conversion interface must be used, most single-chip microcomputers are equipped with an A / D conversion interface, the sampling frequency of the voltage signal is preferably greater than 1KHz, and then the effective value is calculated.

[0043] In another preferred embodiment of the application, the resistance groups are replaced several times, the sum of the equivalent resistances of the resistance groups in the two branch lines remains unchanged, the equivalent resistances of the resistance groups in the single branch line are all different, the current values corresponding to different resistance groups are sequentially obtained, the mean and standard deviation of the current values are calculated, the current values within 3 standard deviations above and below the mean are screened, the screened current values are calculated again, a new mean of the current values is obtained and output as a current value signal.

[0044] In order to avoid errors in single measurement and errors that may be caused by voltage fluctuations to the measurement results, multiple measurements are adopted to calculate the mean and standard deviation of the current values to remove abnormal current values, so as to ensure the accuracy of the measurement data.

[0045] In another preferred embodiment of the application, the isolating switch power supply converts the commercial AC power supply into a low-voltage DC power supply, the low-voltage DC power supply outputs a 5V low-voltage DC power supply through the voltage stabilizer, the 5V low-voltage DC power supply supplies power to the operational amplifier and the single-chip microcomputer, and the input and output ends of the voltage stabilizer are both connected with a smoothing capacitor.

[0046] Switching mode power supply, is a high frequency power conversion device, is a power supply. According to whether there is electrical isolation between input and output can be divided into isolated and non-isolated, its function is to convert a voltage, through different forms of architecture to the user end needs voltage or current. Switching power supply input is mostly alternating current (such as mains) or is direct current, and output is mostly need direct current power supply equipment, in this embodiment, the mains alternating current power supply through the isolation switching power supply and voltage regulator output for the single chip microcomputer said 5V direct current working voltage.

[0047] In another preferred embodiment of the application, the single chip microcomputer outputs the current value signal to the LED display screen through optical coupling communication, the optical coupling communication is realized through an optical coupler, when the single chip microcomputer outputs a low level signal, the light emitting diode of the optical coupler is turned on, and the light emitting diode emits light, when the single chip microcomputer outputs a high level signal, the light emitting diode of the optical coupler is not turned on, and the light emitting diode does not emit light.

[0048] It is worth noting that a photosensitive triode is added at the output end of the optical coupler, when the light emitting diode emits light, the photosensitive triode at the output end is turned on, and when the light emitting diode does not emit light, the photosensitive triode at the output end is not turned on.

[0049] When the single chip microcomputer outputs a signal, it is often interfered by radio frequency or fast electric pulse group, which is very easy to cause control failure between two systems or communication error code; for this case, the isolation circuit is a good solution, the main purpose of the isolation circuit is to cut off the electrical connection between two systems through “electro-optical-optical” conversion device or “electromagnetic-magneto” conversion device; there is no direct electrical relationship between the two circuits, so the radio frequency radiation or conduction radiation between the two systems cannot interfere with each other, thereby achieving the purpose of anti-interference.

[0050] In the “electro-optical-optical” isolator, we generally choose optical coupling isolator, the input end of the optical coupler is a current type working low resistance element, so it has strong common mode rejection capability. Therefore, it can greatly improve the signal-to-noise ratio as a terminal isolation element in long line transmission information, and can greatly increase the reliability of computer work as a signal isolation interface device in computer digital communication and real-time control.

[0051] The photosensitive triode and the photosensitive diode can both convert the received light signal into an electrical signal, but the base area of the photosensitive triode is the place where light is received, so the base area is larger than that of the ordinary triode, and the converted photo current is tens of times or even hundreds of times larger than that of the photosensitive diode.

[0052] The above has been described in detail one embodiment of the present application, but the content is only the preferred embodiment of the present application, cannot be considered for limiting the scope of the present application. Any equivalent changes and improvements made in the scope of the present application, should still belong to the scope of the present application.

Claims

1. A non-isolated method for detecting high-voltage current, characterized in that, Includes the following steps: A current measurement circuit is established, which includes an isolated switching power supply, a resistor group, an operational amplifier, a microcontroller, and an LED display screen; The live or neutral wire of the high-voltage circuit is split into two branches, ACL1 and ACL2. The branches are short-circuited to the ground wire of the isolation switching power supply respectively. A first resistor group is connected in series in ACL1 and a second resistor group is connected in series in ACL2. The operational amplifier obtains the voltage signals of ACL1 and ACL2 after being divided by resistors. The operational amplifier biases and amplifies the voltage signals and outputs them to the A / D interface of the microcontroller. The microcontroller obtains the effective value of the voltage signal through the A / D interface, and then calculates the current value of the high-voltage circuit. The microcontroller outputs a current value signal to the LED display screen; The operational amplifier acquires the voltage signal through the non-inverting input terminal and the inverting input terminal. The voltage signal is amplified by the operational amplifier with a magnification factor of 1. The operational amplifier amplifies the negative voltage in the voltage signal into a positive voltage and buffers and isolates the voltage signal. The microcontroller calculates the effective value of the voltage signal through the A / D interface, calculates the frequency and amplitude of the voltage signal, obtains the effective value of the voltage signal, subtracts the bias voltage superimposed by the operational amplifier from the effective value to obtain the difference, multiplies the difference by the step-down factor to obtain the effective voltage values ​​of ACL1 and ACL2, and then obtains the current value of the high-voltage circuit according to Ohm's law. The resistor group in the branch line is replaced several times, while keeping the sum of the equivalent resistances of ACL1 and ACL2 constant. Each time the resistor group is replaced, the corresponding current value is measured, and the mean and standard deviation of the current value are calculated. Only the current values ​​within three standard deviations above and below the mean are selected. The selected current values ​​are recalculated to obtain a new mean current value, which is then output as the current value signal.

2. The high-voltage non-isolated detection method according to claim 1, characterized in that, The voltage signal is output by the operational amplifier and then filtered by an RC circuit.

3. The high-voltage non-isolated detection method according to claim 1, characterized in that, The isolated switching power supply converts AC mains power into low-voltage DC power. The low-voltage DC power is output as 5V low-voltage DC power through a voltage regulator. The 5V low-voltage DC power supplies power the operational amplifier and the microcontroller. A smoothing capacitor is connected between the input and output terminals of the voltage regulator.

4. The high-voltage non-isolated detection method according to claim 1, characterized in that, The microcontroller outputs the current value signal to the LED display screen via optocoupler communication. The optocoupler communication is implemented through an optocoupler. When the microcontroller outputs a low-level signal, the LED of the optocoupler is turned on and emits light; when the microcontroller outputs a high-level signal, the LED of the optocoupler is not turned on and emits no light.

5. The high-voltage non-isolated detection method according to claim 4, characterized in that, A phototransistor is added to the output terminal of the optocoupler. When the light-emitting diode emits light, the phototransistor at the output terminal is turned on; when the light-emitting diode does not emit light, the phototransistor at the output terminal is not turned on.

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