CN114859100A - Measuring circuit and measuring method of alternating voltage and intelligent equipment - Google Patents

Abstract

The invention discloses a measuring circuit, a measuring method and intelligent equipment of alternating voltage, wherein the measuring circuit of the alternating voltage is only provided with a voltage comparison circuit in front of an optical coupling circuit, so that the alternating voltage of an external power supply controls the on-off of the optical coupling circuit under the control of a preset reference voltage of the voltage comparison circuit, a level signal is output to a controller, the controller determines the on duration of the optical coupling circuit according to the level signal, and the voltage value of the alternating voltage of the external alternating power supply can be quickly determined by only combining simple circuit design and the software logic principle of the controller without the aid of complex and expensive electronic components, thereby reducing the cost for measuring the voltage value of the alternating voltage of the external alternating power supply.

Description

Measuring circuit and measuring method of alternating voltage and intelligent equipment

Technical Field

The invention relates to the technical field of alternating voltage measurement, in particular to a measuring circuit, a measuring method and intelligent equipment for alternating voltage.

Background

At present, the measurement schemes of ac voltage mainly include two main categories, wherein the first category is: the method comprises the following steps that a micro mutual inductor is used as a core element, an input high-voltage signal is directly converted into a low-voltage signal, or the input voltage is converted into a small-current signal through a primary series resistor of the mutual inductor, then the mutual inductor with the ratio of 1 to 1 is used for conversion, the converted current signal is converted into a voltage signal through resistance circuit processing, an alternating current signal output by the mutual inductor is processed through a proper operational amplifier circuit and then sent to an analog-to-digital conversion (ADC) chip for acquisition and conversion, a conversion result is sent to a Digital Signal Processing (DSP) chip for further algorithm processing, such as fast Fourier transform, and finally fundamental wave components and harmonic wave components of alternating current voltage can be obtained to obtain an effective value of the alternating current voltage; the second type is: the alternating current high voltage is converted into direct current low voltage in a mode of rectifying and then resistance voltage dividing, the direct current low voltage value is acquired and converted by an analog-to-digital conversion ADC (analog-to-digital converter) of the measurement chip, and then the effective value of the alternating current voltage is estimated by the measurement chip according to the average value of conversion results in a mode of fixing mathematical proportion.

However, the first category is found in practice because the mutual inductor itself is not cheap, and the digital processing of the alternating current signal requires an additional digital processing circuit and the processing flow is complex; in the second category, a voltage reduction and stabilization circuit for measuring power supply of the chip and an optical coupling isolation circuit for informing a main control chip of a measurement result are additionally arranged. It can be seen that the cost is relatively high for both the first and second types of measurement schemes.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide an ac voltage measuring circuit, which can quickly determine the voltage value of the ac voltage of the external ac power supply, and reduce the cost for measuring the voltage value of the ac voltage of the external ac power supply.

In order to solve the technical problem, the invention discloses a measuring circuit of alternating voltage in a first aspect, wherein the measuring circuit comprises an optical coupling circuit and a voltage comparison circuit, wherein the optical coupling circuit comprises an optical coupling primary circuit and an optical coupling secondary circuit;

the output end of the voltage comparison circuit is electrically connected with the input end of the primary circuit of the optical coupler; the output end of the optical coupler primary circuit is inductively connected with the input end of the optical coupler secondary circuit, and the output end of the optical coupler secondary circuit is electrically connected with a controller; the input end of the voltage comparison circuit is used for being electrically connected with an external alternating current power supply;

the voltage comparison circuit is used for providing reference voltage for measuring the alternating voltage of the external alternating current power supply and controlling the on-off of the primary circuit of the optical coupler;

the optical coupler primary circuit is used for outputting an optical signal under the control of the voltage comparison circuit;

the optical coupling secondary circuit is used for sensing the photoelectric signal, converting the photoelectric signal into a level signal and outputting the level signal to the controller so as to trigger the controller to determine the voltage value of the alternating voltage of the external alternating current power supply according to the duration of receiving the level signal.

As an optional implementation manner, in the first aspect of the present invention, the voltage comparison circuit includes a zener diode P or an adjustable voltage stabilizing circuit;

when the voltage comparison circuit is the adjustable voltage stabilizing circuit, the measuring circuit further comprises a voltage stabilizing power supply circuit;

the first output end of the voltage-stabilizing power supply circuit is electrically connected with the input end of the optocoupler primary circuit, the second output end of the voltage-stabilizing power supply circuit is electrically connected with the input end of the adjustable voltage stabilizing circuit, and the input end of the voltage-stabilizing power supply circuit is used for being electrically connected with the external alternating current power supply;

and the voltage-stabilizing power supply circuit is used for extracting an alternating voltage half wave from an alternating voltage wave of the external alternating current power supply and providing matched current for the primary circuit of the optical coupler.

As an optional implementation manner, in the first aspect of the present invention, the voltage stabilizing and supplying circuit includes a resistance-capacitance step-down voltage stabilizing circuit and a voltage extracting module;

the output end of the resistance-capacitance voltage reduction and stabilization circuit is electrically connected with the input end of the optical coupler primary circuit, the output end of the voltage extraction module is electrically connected with the input end of the resistance-capacitance voltage reduction and stabilization circuit and the input end of the voltage comparison circuit, and the input end of the voltage extraction module is used for being electrically connected with the external alternating current power supply;

the voltage extraction module is used for extracting an alternating voltage half wave from an alternating voltage wave of the external alternating current power supply;

and the resistance-capacitance voltage reduction and stabilization circuit is used for taking voltage from the extracted half-wave of the alternating voltage and providing current for the primary circuit of the optical coupler.

As an optional implementation manner, in the first aspect of the present invention, the measurement circuit further includes a transition edge processing circuit;

the input end of the hopping edge processing circuit is electrically connected with the output end of the optical coupling secondary circuit, and the output end of the hopping edge processing circuit is electrically connected with the controller;

and the transition edge processing circuit is used for changing the steepness of the rising edge of the level signal and the steepness of the falling edge of the level signal and transmitting the changed level signal to the controller.

As an alternative implementation manner, in the first aspect of the present invention, the optical coupler primary circuit includes a first resistor R1, a second resistor R2, and a light emitting diode D1, and the optical coupler secondary circuit includes a phototransistor Q1 and a pull-up resistor R0; wherein the first resistor R1 is connected in parallel with the light emitting diode D1; the collector of the phototransistor Q1 is electrically connected with one end of the pull-up resistor R0, the base of the phototransistor Q1 is inductively connected with the light emitting diode D1, the emitter of the phototransistor Q1 is used for connecting with a secondary reference ground end, and the other end of the pull-up resistor R0 is electrically connected with an internal power supply V1;

when the voltage comparison circuit is the voltage regulator diode P, the cathode of the light emitting diode D1 is used for being electrically connected to the external ac power supply, one end of the second resistor R2 is electrically connected to the anode of the light emitting diode D1, the other end of the second resistor R2 is electrically connected to the anode of the voltage regulator diode P, and the cathode of the voltage regulator diode P is used for being electrically connected to the external ac power supply;

when the voltage comparison circuit is the adjustable voltage stabilizing circuit, the cathode of the light emitting diode D1 is electrically connected with the output end of the adjustable voltage stabilizing circuit; one end of the second resistor R2 is electrically connected with the anode of the light emitting diode D1, and the other end of the second resistor R2 is electrically connected with the output end of the voltage-stabilizing power supply circuit.

In an optional implementation manner, in the first aspect of the present invention, the adjustable voltage stabilizing circuit includes a controllable voltage regulator K, a third resistor R3, and a fourth resistor R4;

a cathode of the controllable voltage regulator K is electrically connected with the optocoupler circuit, a reference electrode of the controllable voltage regulator is electrically connected with a first end of the fourth resistor R4 and a first end of the third resistor R3 respectively, and a second end of the fourth resistor R4 is electrically connected with an input end of the voltage comparison circuit;

and the second end of the third resistor R3 and the anode of the controllable voltage regulator are connected with a primary reference ground end.

As an optional implementation manner, in the first aspect of the present invention, the resistance-capacitance voltage reduction and stabilization circuit includes a voltage regulator tube Z, a capacitor C, a fifth resistor R5, and a first diode D2;

one end of the fifth resistor R5 is electrically connected to the cathode of the first diode D2, the other end of the fifth resistor R5, one end of the capacitor C, the cathode of the voltage regulator tube Z, and the other end of the second resistor R2 are electrically connected to a second internal power supply V2, respectively, and the anode of the first diode D2 is electrically connected to the output end of the voltage extraction module;

the other end of the capacitor C and the positive electrode of the voltage stabilizing tube Z are both used for being connected with a primary reference ground end.

As an optional implementation manner, in the first aspect of the present invention, the edge-skipping processing circuit includes a transistor Q2, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8;

one end of the sixth resistor R6 is electrically connected to an output end of the optocoupler circuit, the other end of the sixth resistor R6 is electrically connected to a base of the transistor Q2 and one end of the seventh resistor R7, a collector of the transistor Q2 is electrically connected to one end of the eighth resistor R8, one end of the eighth resistor R8 is electrically connected to the controller, and the other end of the eighth resistor R8 is electrically connected to the internal power supply V1;

the other end of the seventh resistor R7 and the emitter of the triode Q2 are both used for being connected with a secondary reference ground.

As an alternative implementation, in the first aspect of the present invention, the voltage extraction module includes a second diode D3;

the voltage extraction module further comprises a third diode D4, wherein the anode of the third diode D4 is used for connecting a primary reference ground, the cathode of the third diode D4 is used for electrically connecting a zero line end of the external alternating current power supply, the anode of the second diode D3 is used for electrically connecting a live wire end of the external alternating current power supply, and the cathode of the second diode D3 is electrically connected with the input end of the voltage comparison circuit.

The second aspect of the present invention discloses a method for measuring an ac voltage, wherein the method is applied to a measurement circuit for measuring an ac voltage, the measurement circuit includes an optical coupler circuit and a voltage comparison circuit, the optical coupler circuit includes an optical coupler primary circuit and an optical coupler secondary circuit, and the method includes:

the voltage comparison circuit acquires alternating current voltage of an external alternating current power supply and controls the on-off of the primary circuit of the optical coupler according to the acquired alternating current voltage of the external alternating current power supply and preset reference voltage, and the preset reference voltage is used for measuring the alternating current voltage of the external alternating current power supply;

under the control of the voltage comparison circuit, the primary circuit of the optical coupler outputs an optical signal;

the optical coupling secondary circuit senses the photoelectric signal, converts the photoelectric signal into a level signal, and outputs the level signal to the controller so as to trigger the controller to determine the voltage value of the alternating voltage of the external alternating current power supply according to the duration of receiving the level signal.

As an optional implementation manner, in the second aspect of the present invention, the measurement circuit further includes a voltage stabilization power supply circuit;

and, the method further comprises:

the voltage-stabilizing power supply circuit extracts alternating-current voltage half waves from alternating-current voltage waves of the external alternating-current power supply and provides matched current for the primary circuit of the optical coupler.

As an optional implementation manner, in the second aspect of the present invention, the measurement circuit further includes a transition edge processing circuit, wherein the transition edge processing circuit is disposed between the optical coupler secondary circuit and the controller;

and after the optical coupling secondary circuit senses the photoelectric signal and converts the photoelectric signal into a level signal, the method further comprises:

the transition edge processing circuit changes the steepness of the rising edge of the level signal and the steepness of the falling edge of the level signal;

wherein, the outputting the level signal to the controller to trigger the controller to determine the voltage value of the alternating current voltage of the external alternating current power supply according to the duration of receiving the level signal includes:

and the jumping edge processing circuit transmits the changed level signal to the controller so as to trigger the controller to determine the voltage value of the alternating current voltage of the external alternating current power supply according to the duration of receiving the level signal.

A third aspect of the present invention discloses a smart device, characterized in that the smart device includes the measurement circuit of the alternating voltage according to any one of the first aspects.

The implementation of the invention has the following beneficial effects:

the invention provides a measuring circuit of alternating voltage, which comprises an optical coupler circuit and a voltage comparison circuit, wherein the optical coupler circuit comprises an optical coupler primary circuit and an optical coupler secondary circuit; the output end of the voltage comparison circuit is electrically connected with the input end of the primary circuit of the optical coupler; the output end of the optical coupler primary circuit is inductively connected with the input end of the optical coupler secondary circuit, and the output end of the optical coupler secondary circuit is electrically connected with a controller; the input end of the voltage comparison circuit is used for being electrically connected with an external alternating current power supply; the voltage comparison circuit is used for providing reference voltage for measuring the alternating voltage of the external alternating current power supply and controlling the on-off of the primary circuit of the optical coupler; the optical coupler primary circuit is used for outputting an optical signal under the control of the voltage comparison circuit; and the optocoupler secondary circuit is used for sensing the photoelectric signal, converting the photoelectric signal into a level signal and outputting the level signal to the controller so as to trigger the controller to determine the voltage value of the alternating voltage of the external alternating current power supply according to the duration of the received level signal. Therefore, according to the invention, only the voltage comparison circuit is arranged in front of the optical coupling circuit, so that the AC voltage of the external power supply is controlled to be on or off under the control of the preset reference voltage of the voltage comparison circuit, the level signal is output to the controller, the controller determines the on duration of the optical coupling circuit according to the level signal, the voltage value of the AC voltage of the external AC power supply can be quickly determined without using complex and expensive electronic components and only by combining simple circuit design and the software logic principle of the controller, and the cost for measuring the voltage value of the AC voltage of the external AC power supply is reduced.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of an ac voltage measuring circuit according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of another alternate current voltage measurement circuit according to the embodiment of the present invention;

FIG. 3 is a schematic structural diagram of another alternative AC voltage measurement circuit according to the present disclosure;

FIG. 4 is a schematic structural diagram of another alternative AC voltage measuring circuit according to the present disclosure;

FIG. 5 is a schematic structural diagram of a method for measuring an AC voltage according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of an intelligent device disclosed in the embodiment of the present invention.

Detailed Description

For better understanding and implementation, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is to be understood that, unless otherwise explicitly specified or limited, the term "electrically connected" in the description and claims of the present invention and the above drawings is to be interpreted broadly, e.g., as a fixed electrical connection, a detachable electrical connection, or an integral electrical connection; can be mechanically and electrically connected, can be electrically connected or can be communicated with each other; either directly or indirectly through intervening media, either internally or in any other relationship. Furthermore, the terms "first," "second," and the like in the description and claims of the present invention and in the above-described drawings are used for distinguishing between different elements and not necessarily for describing a particular order, and the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusions. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

Example one

Referring to fig. 1, fig. 1 is a schematic structural diagram of a measurement circuit for ac voltage according to an embodiment of the present invention. As shown in fig. 1, the ac voltage measuring circuit includes an optical coupler circuit and a voltage comparison circuit, wherein the optical coupler circuit includes an optical coupler primary circuit and an optical coupler secondary circuit;

the output end of the voltage comparison circuit is electrically connected with the input end of the primary circuit of the optical coupler; the output end of the optical coupler primary circuit is inductively connected with the input end of the optical coupler secondary circuit, and the output end of the optical coupler secondary circuit is electrically connected with a controller; the input end of the voltage comparison circuit is used for being electrically connected with an external alternating current power supply; the voltage comparison circuit is used for providing reference voltage for measuring the alternating voltage of the external alternating current power supply and controlling the on-off of the primary circuit of the optical coupler; the optical coupler primary circuit is used for outputting an optical signal under the control of the voltage comparison circuit; and the optocoupler secondary circuit is used for sensing the photoelectric signal, converting the photoelectric signal into a level signal and outputting the level signal to the controller so as to trigger the controller to determine the voltage value of the alternating voltage of the external alternating current power supply according to the duration of the received level signal.

In the embodiment of the invention, specifically, the controller calculates the duration of the received level signal through a counter obtained by a high-speed oscillator and a frequency divider, so as to determine the conduction duration of the secondary circuit of the optocoupler, and further calculate the voltage value of the alternating voltage of the external alternating current power supply.

Therefore, according to the invention, only the voltage comparison circuit is arranged in front of the optical coupling circuit, so that the AC voltage of the external power supply is controlled to be on or off under the control of the preset reference voltage of the voltage comparison circuit, the level signal is output to the controller, the controller determines the on duration of the optical coupling circuit according to the level signal, the voltage value of the AC voltage of the external AC power supply can be quickly determined without using complex and expensive electronic components and only by combining simple circuit design and the software logic principle of the controller, and the cost for measuring the voltage value of the AC voltage of the external AC power supply is reduced.

In the embodiment of the present invention, as shown in fig. 3 or 4, the primary optical coupler circuit includes a first resistor R1, a second resistor R2, and a light emitting diode D1, and the secondary optical coupler circuit includes a phototransistor Q1 and a pull-up resistor R0; the first resistor R1 is connected in parallel with the light-emitting diode D1; the collector of the phototransistor Q1 is electrically connected with one end of a pull-up resistor R0, the base of the phototransistor Q1 is inductively connected with a light-emitting diode D1, the emitter of the phototransistor Q1 is used for connecting with a secondary reference ground end, and the other end of the pull-up resistor R0 is used for electrically connecting with an internal power supply V1. Optionally, the combination of the light emitting diode D1 and the phototransistor Q1 may be EL817 or EL357 as a core element of the optical coupling circuit, which can reduce the cost. Further, by setting a preset reference voltage of the measuring circuit, for example, 83.7V, and because the switching time of the optocoupler transistor Q1 is fixed after the components of the optocoupler circuit are selected, the lower the preset reference voltage value is under the same ac voltage, the longer the on-time of the optocoupler is, which means that the influence of the secondary switching time of the optocoupler on the optocoupler is smaller, and the higher the measurement accuracy of the ac voltage is.

In the embodiment of the invention, in order to ensure the measurement accuracy, for the optocoupler secondary circuit, the resistance value of the pull-up resistor R0 connected with the collector of the optocoupler phototransistor Q1 is determined according to the specific models of the selected phototransistor Q1 and the selected light-emitting diode D1. Generally speaking, the smaller the value of the pull-up resistor R0, the less the phototransistor Q1 of the optocoupler secondary circuit is likely to enter saturation, the longer it takes to go from off to on, the shorter it takes to go from on to off, and the difference between the time it takes for phototransistor Q1 to go from off to on and the time it takes for phototransistor Q1 to go back off can generally be shortened by reducing the resistance of pull-up resistor R0, but the curves of different optical coupler models, which change from cut-off to conduction and from conduction to cut-off along with the change of the resistance value of the pull-up resistor R0, are different, and too small a resistance value of pull-up resistor R0 affects the voltage difference between the collector and emitter of phototransistor Q1 during on-state of the optocoupler, and further influences the judgment of the controller on the high and low level signals, so that a pull-up resistor R0 with a proper resistance value (e.g., 8.2k Ω) needs to be selected. For example: the actual electrifying time of the light-emitting diode D1 of the optical coupler is 8000us, time delay exists when electricity is converted into light waves, time delay also exists when light waves are converted into electrons, the conducting time of the phototransistor Q1 of the optical coupler detected by the controller can be 8010us, and therefore a measuring error of more than 1V can be introduced.

In an alternative embodiment, as shown in FIG. 2, the measurement circuit further includes a transition edge processing circuit; the input end of the hopping edge processing circuit is electrically connected with the output end of the optical coupler secondary circuit, and the output end of the hopping edge processing circuit is electrically connected with the controller; and the transition edge processing circuit is used for changing the steepness of the rising edge of the level signal and the steepness of the falling edge of the level signal and transmitting the changed level signal to the controller. Therefore, the rising edge and the falling edge of the level signal input into the controller become steep through the jump edge processing circuit, different controllers can stably identify the level jump moment, and therefore the measurement accuracy and efficiency of the alternating voltage are improved.

In this optional embodiment, as shown in fig. 3 or 4, optionally, the edge-skipping processing circuit includes a transistor Q2, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8; one end of the sixth resistor R6 is electrically connected with the output end of the optocoupler circuit, the other end of the sixth resistor R6 is electrically connected with the base of the triode Q2 and one end of the seventh resistor R7 respectively, the collector of the triode Q2 is electrically connected with one end of the eighth resistor R8, one end of the eighth resistor R8 is electrically connected with the controller, and the other end of the eighth resistor R8 is electrically connected with the internal power supply V1; the other end of the seventh resistor R7 and the emitter of the transistor Q2 are both used for being connected with the secondary reference ground end.

In this alternative embodiment, in order to ensure the measurement accuracy, the transition timing of the level signal input to the controller is changed by the transition edge processing circuit, thereby reducing the difference between the time period during which the ordinary optocoupler phototransistor Q is turned on from off and the time period during which the phototransistor Q is turned back off from on. For example, the voltage at the collector of the phototransistor Q1 of the optocoupler secondary circuit continuously drops during the time period when the phototransistor Q1 goes from off to on, and normally, when the controller detects that the voltage at the collector of the phototransistor Q1 drops below 1.5V, the controller recognizes the switching of the input signal from high to low, and through the transition edge processing circuit, the controller may recognize the transition edge only when the voltage at the collector of the phototransistor Q1 drops below 1.2V, which is equivalent to the extension of the time period when the phototransistor Q1 goes from off to on, and similarly, the voltage at the collector of the phototransistor Q1 continuously rises during the time period from on to off, and normally, when the controller detects that the voltage at the collector of the phototransistor Q1 rises above 3.5V, the controller recognizes the switching of the input signal from low to high, through the transition edge processing circuit, so that the controller recognizes a transition edge when the voltage at the collector of phototransistor Q1 rises to 3.2V, which is equivalent to a reduction in the time period for phototransistor Q1 to go back from on to off, while the time period for phototransistor Q1 to go back from on to off is typically greater than the time period for phototransistor Q1 to go from off to on, so the difference between the time period for phototransistor Q1 to go from off to on and the time period for phototransistor Q1 to go back from on to off can be reduced by additional circuitry. For example, the transistor Q2 in the transition edge processing circuit may use a simple transistor circuit, a transistor with a base voltage difference of 0.6V and an emitter voltage is selected as a core element, and a pull-down resistor R7 of 10k ohms is selected, when the base resistor R6 of the transistor Q2 is 10k ohms, the transistor Q2 with an input level greater than 1.2V is turned on, that is, when the phototransistor Q1 is turned on from off, the voltage of the collector of the phototransistor Q1 is decreased from 5V to below 1.2V, the transistor Q2 is turned off, when the phototransistor Q is turned off from on, the voltage of the collector of the phototransistor Q1 is increased from 0V to above 1.2V, the transistor Q2 is turned on, and the off time of the transistor Q2 corresponds to the on time of the optocoupler D1.

It should be noted that, the TLP2301 of TOSHIBA may be selected as a core element of the optocoupler circuit for the combination of the light emitting diode D1 and the phototransistor Q1, so that the measurement accuracy of the alternating voltage can be further improved.

In an embodiment of the present invention, optionally, the voltage comparison circuit includes a zener diode P or an adjustable voltage stabilizing circuit. When the voltage comparison circuit is an adjustable voltage stabilizing circuit, the measuring circuit also comprises a voltage stabilizing power supply circuit; the first output end of the voltage-stabilizing power supply circuit is electrically connected with the input end of the optocoupler primary circuit, the second output end of the voltage-stabilizing power supply circuit is electrically connected with the input end of the adjustable voltage stabilizing circuit, and the input end of the voltage-stabilizing power supply circuit is used for being electrically connected with an external alternating current power supply; the voltage stabilizing power supply circuit is used for extracting an alternating voltage half wave from an alternating voltage wave of an external alternating current power supply and providing matched current for the primary circuit of the optical coupler.

In the embodiment of the invention, optionally, the voltage stabilizing power supply circuit comprises a resistance-capacitance voltage reducing and stabilizing circuit and a voltage extracting module; the output end of the resistance-capacitance voltage reduction and stabilization circuit is electrically connected with the input end of the optocoupler primary circuit, the output end of the voltage extraction module is electrically connected with the input end of the resistance-capacitance voltage reduction and stabilization circuit and the input end of the voltage comparison circuit, and the input end of the voltage extraction module is used for being electrically connected with an external alternating current power supply; the voltage extraction module is used for extracting an alternating voltage half wave (such as 0-180 degrees) from an alternating voltage wave of an external alternating current power supply; and the resistance-capacitance voltage reduction and stabilization circuit is used for taking voltage from the extracted half-wave of the alternating voltage and providing current for the primary circuit of the optical coupler. As shown in fig. 4, optionally, the resistance-capacitance voltage reduction and stabilization circuit includes a voltage regulator tube Z, a capacitor C, a fifth resistor R5, and a first diode D2; one end of a fifth resistor R5 is electrically connected with the cathode of a first diode D2, the other end of the fifth resistor R5, one end of a capacitor C, the cathode of a voltage-regulator tube Z and the other end of a second resistor R2 are respectively electrically connected with a second internal power supply V2, and the anode of the first diode D2 is electrically connected with the output end of the voltage extraction module; the other end of the capacitor C and the positive electrode of the voltage-stabilizing tube Z are both used for being connected with a primary reference ground end. Wherein, the voltage that resistance-capacitance voltage reduction and voltage regulation circuit extracted is the voltage in the preset voltage range, if: 6.8V between 6.0V and 7.0V can reduce the occurrence of circuit heating caused by overlarge extracted voltage, and find a voltage stabilizing tube Z which can meet the requirement of different working currents and voltages and keep stable, thereby improving the universal applicability of the circuit. And the current provided by the resistance-capacitance voltage reduction and stabilization circuit to the primary circuit of the rear-stage optocoupler is the current within a preset current range, such as: 0.8mA-1.2mA, so that the cost of the resistance-capacitance voltage reduction and stabilization circuit can be reduced, the heating of elements can be reduced, the standby power consumption can be reduced, and the applicability of the circuit can be improved; the influence on the normal work of the voltage comparison circuit and the switching time of the level signal of the optical coupling secondary circuit can be reduced, and the measurement accuracy of the alternating voltage is further improved. It should be noted that the resistance-capacitance voltage reduction and stabilization circuit can be replaced by a switching power supply circuit.

When the voltage comparison circuit is a zener diode P, as shown in fig. 3, a cathode of the light emitting diode D1 is used to electrically connect to an external ac power supply, one end of the second resistor R2 is electrically connected to an anode of the light emitting diode D1, the other end of the second resistor R2 is electrically connected to an anode of the zener diode P, and a cathode of the zener diode P is used to electrically connect to the external ac power supply; in this way, the second resistor R2 controls the current flowing through the zener diode P, thereby reducing the occurrence of the situation that the zener diode P is burnt out due to overheating and the ac voltage of the external ac power supply cannot be measured. The second resistor R2 may be a single resistor, or may be composed of a plurality of resistors with equal or unequal resistance values. Further, as shown in fig. 3, the ac voltage measuring circuit further includes a third diode D4, and the third diode D4 is disposed between the first resistor R1 and the external ac power supply, so that by disposing the third diode D4, the current flowing through the second resistor R2 and the first resistor R1 can be cut off during the negative half-wave of the ac, the heat generation of the second resistor R2 and the first resistor R1 can be reduced, and the light emitting diode D1 of the optical coupler can be protected.

When the voltage comparison circuit is an adjustable voltage stabilizing circuit, as shown in fig. 4, the cathode of the light emitting diode D1 is electrically connected with the output end of the adjustable voltage stabilizing circuit; one end of the second resistor R2 is electrically connected with the anode of the light emitting diode D1, and the other end of the second resistor R2 is electrically connected with the output end of the voltage stabilizing power supply circuit. The adjustable voltage stabilizing circuit comprises a controllable voltage stabilizing source K, a third resistor R3 and a fourth resistor R4; the cathode of the controllable voltage-stabilizing source K is electrically connected with the optocoupler circuit, the reference electrode of the controllable voltage-stabilizing source is electrically connected with the first end of the fourth resistor R4 and the first end of the third resistor R3 respectively, and the second end of the fourth resistor R4 is electrically connected with the input end of the voltage comparison circuit; the second end of the third resistor R3 and the anode of the controllable voltage regulator are used for being connected with the secondary reference ground. The preset reference voltage mentioned in the present invention may be determined by the controllable regulator voltage source K, the third resistor R3 and the fourth resistor R4. The controllable voltage-stabilizing source K may include a TL431 voltage stabilizer or a comparator chip. And, as shown in fig. 4, the voltage extraction module includes a second diode D3; the voltage extraction module further comprises a third diode D4, wherein the anode of the third diode D4 is used for being connected with the primary reference ground, the cathode of the third diode D4 is used for being electrically connected with the zero line end of the external alternating current power supply, the anode of the second diode D3 is used for being electrically connected with the live wire end of the external alternating current power supply, and the cathode of the second diode D3 is electrically connected with the input end of the voltage comparison circuit. Therefore, by adding the third diode D4, the situation that when a reverse surge voltage occurs, the second diode D3 is broken down to cause the second diode D3 to be in an open-circuit state, so that the circuit cannot measure the alternating-current voltage, or the second diode D3 is in a short-circuit state, so that the circuit cannot cut off the current flowing through the fourth resistor R4 and the third resistor R3 during a negative half-wave, so that the heating of the fourth resistor R4 and the third resistor R3 is increased, and the controllable voltage regulator K is easily damaged is reduced, the surge resistance of the measuring circuit of the alternating-current voltage is improved, and the measuring circuit is protected.

In the embodiment of the invention, optionally, when the electrical control device corresponding to the measurement circuit of the alternating-current voltage is provided with the switching power supply, the voltage extraction module can be a rectifier bridge, and at the moment, the low-voltage direct-current power supply output by the bias winding of the transformer of the switching power supply can replace a resistance-capacitance voltage reduction and stabilization circuit, so that the cost of the measurement circuit can be further reduced.

The embodiment of the invention uses fig. 4 to explain the working principle of the measuring circuit of the alternating voltage:

according to the embodiment of the invention, when the external alternating current power supply is electrified, the alternating voltage measuring circuit starts to work, and when the instantaneous voltage of the external alternating current power supply is 0V, the second diode D3 and the third diode D4 are in a cut-off state, and no current flows through the diodesA fourth resistor R4 and a third resistor R3, at this time, the voltage of the reference electrode of the controllable voltage regulator K is 0V and is less than the reference voltage (such as 2.5V) inside the controllable voltage regulator K, and the controllable voltage regulator K is in a cut-off state; when the instantaneous voltage of the external ac power supply is greater than the sum of the conduction voltages of the second diode D3 and the third diode D4 (e.g., 1.4V), the second diode D3 and the third diode D4 are in a conduction state, at this time, current flows through the fourth resistor R4 and the third resistor R3, so that a voltage drop is formed across the third resistor R3, and the difference between the voltage drop formed across the third resistor R3 and the sum of the instantaneous voltage of the external ac power supply and the conduction voltages of the second diode D3 and the third diode D4 is in a fixed direct proportion relationship. Therefore, the voltage drop formed across the third resistor R3 increases as the instantaneous voltage of the external ac power supply increases and decreases as the instantaneous voltage of the external ac power supply decreases. At this time, if the voltage drop formed on the third resistor R3 is smaller than the reference voltage inside the controllable voltage regulator K, that is, when the instantaneous voltage of the external ac power supply is smaller than the preset comparison voltage, the controllable voltage regulator K is still in a cut-off state, the primary circuit of the optocoupler is in a cut-off state, the light emitting diode D1 does not emit light, the phototransistor Q1 is in a cut-off state, at this time, the triode Q2 is in a conduction state under the power supply of the internal power supply V1, the voltage of the collector of the triode Q2 is pulled down to 0V, and the voltage signal flowing into the controller is a low level signal; when the voltage drop formed on the third resistor R3 is greater than the reference voltage inside the controllable voltage regulator source K, that is, the instantaneous voltage of the external ac power supply is greater than the preset comparison voltage, the voltage of the reference electrode of the controllable voltage regulator source K is greater than or equal to the reference voltage inside the controllable voltage regulator source K, the controllable voltage regulator source K is in a conducting state, the primary circuit of the optocoupler is switched on, when the voltage at the two ends of the light emitting diode D1 is greater than or equal to the conducting voltage, the light emitting diode D1 emits light, and the phototransistor Q1 is in a conducting state. At this time, the voltage at the base of the transistor Q2 is pulled down to 0V by the phototransistor Q1, the transistor Q2 is in the off state, the voltage at the collector of the transistor Q2 is pulled up by the internal power supply V1, and at this time, the voltage signal flowing into the controller is a high level signal. And the instantaneous voltage waveform of the external AC power supply is sine waveTherefore, as time goes on, during each period of the alternating voltage wave, the voltage signal flowing into the controller has continuous high level period, and during each period of the alternating voltage wave, as the instantaneous voltage of the external alternating current power supply is increased from 0V, the voltage drop formed on the third resistor R3 is increased to the reference voltage value inside the controllable voltage-stabilizing source K as the effective voltage value of the external alternating current power supply is higher, and as the instantaneous voltage of the external alternating current power supply is decreased from the peak value, as the effective voltage value of the external alternating current power supply is higher, the speed of the voltage drop formed on the third resistor R3 is slower, and finally the high level period of the voltage signal flowing into the controller is lengthened as the effective voltage value of the external alternating current power supply is increased, the effective voltage value of the external AC power supply is shortened along with the reduction of the effective voltage value of the external AC power supply. At this time, when the effective voltage value of the external ac power supply is known, the duration required for the instantaneous voltage of the external ac power supply to rise from 0V to the preset comparison voltage may be obtained through a sine function y ═ a sin (x), and vice versa, where y is the preset comparison voltage value, and a is the effective voltage value of the external ac power supply

And x is an arc value corresponding to a time period T1 required by the instantaneous voltage of the external alternating current power supply to rise from 0V to a preset comparison voltage, wherein the arc value x is 2 × pi × T1/T, T is a periodic value of the waveform of the external alternating current power supply voltage, for example, T is 20ms, and the high-level time period T2 is T/2-2 × T1. Therefore, the controller can quickly determine the alternating voltage value of the external alternating current power supply by capturing the duration of the high level of the input voltage signal, without the aid of complex and expensive electronic components and by the aid of combination of simple circuit design and the software logic principle of the controller, and the cost of measuring the alternating voltage value of the external alternating current power supply is reduced.

Example two

Referring to fig. 5, fig. 5 is a schematic flowchart of a method for measuring an ac voltage according to an embodiment of the present invention, where the method is applied to a measurement circuit for measuring an ac voltage, where the measurement circuit includes an optical coupler circuit and a voltage comparison circuit, where the optical coupler circuit includes an optical coupler primary circuit and an optical coupler secondary circuit. As shown in fig. 5, the method for measuring the ac voltage may include the steps of:

101. the voltage comparison circuit obtains alternating voltage of the external alternating current power supply, and controls the on-off of the primary circuit of the optocoupler according to the obtained alternating voltage of the external alternating current power supply and preset reference voltage, wherein the preset reference voltage is used for measuring the alternating voltage of the external alternating current power supply.

102. Under the control of the voltage comparison circuit, the primary circuit of the optical coupler outputs an optical signal.

103. The optical coupling secondary circuit senses a photoelectric signal, converts the photoelectric signal into a level signal, and outputs the level signal to the controller so as to trigger the controller to determine the voltage value of the alternating voltage of the external alternating current power supply according to the duration of the received level signal.

Therefore, the voltage comparison circuit is arranged in front of the optical coupling circuit, so that the alternating current voltage of the external power supply is controlled to be on or off by the control of the preset reference voltage of the voltage comparison circuit, the level signal is output to the controller, the controller determines the duration of the conduction of the optical coupling circuit according to the level signal, complex and expensive electronic components are not needed, the voltage value of the alternating current voltage of the external alternating current power supply can be quickly determined by only combining simple circuit design and the software logic principle of the controller, and the cost of measuring the voltage value of the alternating current voltage of the external alternating current power supply is reduced.

In an optional embodiment, the measurement circuit further includes a transition edge processing circuit, wherein the transition edge processing circuit is disposed between the optical coupling secondary circuit and the controller; and after the optical coupling secondary circuit senses the photoelectric signal and converts the photoelectric signal into a level signal, the method for measuring the alternating voltage may include the steps of:

the jump edge processing circuit changes the steepness of the rising edge of the level signal and the steepness of the falling edge of the level signal;

wherein, export the level signal for the controller to trigger the controller and confirm the voltage value of external AC power supply's alternating voltage according to the duration of receiving the level signal, include:

and the jumping edge processing circuit transmits the changed level signal to the controller so as to trigger the controller to determine the voltage value of the alternating current voltage of the external alternating current power supply according to the duration of the received level signal.

Therefore, the optional embodiment is implemented to enable rising edges and falling edges of level signals input into the controllers to become steep through the jump edge processing circuit, so that different controllers can stably identify level jump moments, and the measurement accuracy of the alternating-current voltage is improved.

In another optional embodiment, the measurement circuit further includes a voltage-stabilizing power supply circuit; the method for measuring the alternating voltage may include the steps of:

the voltage-stabilizing power supply circuit extracts alternating voltage half waves from alternating voltage waves of an external alternating current power supply and provides matched current for the primary circuit of the optical coupler.

In this optional embodiment, the voltage stabilizing and supplying circuit includes a voltage extracting module and a resistance-capacitance voltage reducing and stabilizing circuit, wherein an output end of the resistance-capacitance voltage reducing and stabilizing circuit is electrically connected with an input end of the optocoupler primary circuit, an input end of the resistance-capacitance voltage reducing and stabilizing circuit is electrically connected with an output end of the voltage extracting module, and an input end of the voltage extracting module is used for electrically connecting an external ac power supply; the voltage extraction module is used for extracting an alternating current voltage half-wave from an alternating current voltage wave of an external alternating current power supply; and the resistance-capacitance voltage reduction and stabilization circuit is used for taking voltage from the extracted half-wave of the alternating voltage and providing current for the primary circuit of the optical coupler.

Therefore, the alternative embodiment is implemented to extract the alternating-current voltage half-wave from the alternating-current voltage wave of the external alternating-current power supply through the voltage extraction module and provide proper voltage for the resistance-capacitance voltage reduction and voltage stabilization circuit, so that the resistance-capacitance voltage reduction and voltage stabilization circuit can provide proper current for the primary circuit of the optical coupler, the cost of the resistance-capacitance voltage reduction and voltage stabilization circuit can be reduced, heating of elements can be reduced, standby power consumption can be reduced, and the applicability of the circuit is improved; the influence on the normal work of the voltage comparison circuit and the switching time of the level signal of the optical coupling secondary circuit can be reduced, and the measurement accuracy of the alternating voltage is further improved.

It should be noted that, for other descriptions of the optocoupler primary circuit, the optocoupler secondary circuit, the voltage comparison circuit, the transition edge processing circuit, and the voltage stabilizing power supply circuit, please refer to the description of the relevant contents in the first embodiment, which is not described herein again.

EXAMPLE III

Fig. 6 discloses a schematic structural diagram of an intelligent device, which is a device requiring measurement of an ac voltage and includes an ac voltage measurement circuit according to the first embodiment. It should be noted that, for the detailed description of the measurement circuit of the ac voltage, please refer to the detailed description of the related contents in the embodiment, which is not repeated in this embodiment.

It can be seen that, in the intelligent device described in fig. 6, only the voltage comparison circuit is arranged in front of the optical coupler circuit, so that the ac voltage of the external power supply is controlled to be on or off by the preset reference voltage of the voltage comparison circuit, and the level signal is output to the controller, and the controller determines the duration of the on state of the optical coupler circuit according to the level signal, without using complex and expensive electronic components, and only by combining simple circuit design and the software logic principle of the controller, the voltage value of the ac voltage of the external ac power supply can be quickly determined, and the cost for measuring the voltage value of the ac voltage of the external ac power supply is reduced.

The above detailed description is provided for the measuring circuit, the measuring method and the intelligent device of the ac voltage disclosed in the embodiment of the present invention, and the specific embodiment is applied herein to illustrate the principle and the implementation manner of the present invention, but the above preferred embodiment is not intended to limit the present invention, and the above description of the embodiment is only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be changes in the specific embodiments and the application range without departing from the spirit and scope of the present invention, and therefore, the protection scope of the present invention is subject to the scope defined by the claims.

Claims (13)

1. The measuring circuit of the alternating voltage is characterized by comprising an optical coupling circuit and a voltage comparison circuit, wherein the optical coupling circuit comprises an optical coupling primary circuit and an optical coupling secondary circuit;

the output end of the voltage comparison circuit is electrically connected with the input end of the primary circuit of the optical coupler; the output end of the optical coupler primary circuit is inductively connected with the input end of the optical coupler secondary circuit, and the output end of the optical coupler secondary circuit is electrically connected with a controller; the input end of the voltage comparison circuit is used for being electrically connected with an external alternating current power supply;

the voltage comparison circuit is used for providing reference voltage for measuring the alternating voltage of the external alternating current power supply and controlling the on-off of the primary circuit of the optical coupler;

the optical coupler primary circuit is used for outputting an optical signal under the control of the voltage comparison circuit;

the optical coupling secondary circuit is used for sensing the photoelectric signal, converting the photoelectric signal into a level signal and outputting the level signal to the controller so as to trigger the controller to determine the voltage value of the alternating voltage of the external alternating current power supply according to the duration of receiving the level signal.

2. The alternating voltage measuring circuit according to claim 1, characterized in that said voltage comparison circuit comprises a zener diode (P) or an adjustable voltage regulation circuit;

when the voltage comparison circuit is the adjustable voltage stabilizing circuit, the measuring circuit further comprises a voltage stabilizing power supply circuit;

the first output end of the voltage-stabilizing power supply circuit is electrically connected with the input end of the optocoupler primary circuit, the second output end of the voltage-stabilizing power supply circuit is electrically connected with the input end of the adjustable voltage stabilizing circuit, and the input end of the voltage-stabilizing power supply circuit is used for being electrically connected with the external alternating current power supply;

and the voltage-stabilizing power supply circuit is used for extracting an alternating voltage half wave from an alternating voltage wave of the external alternating current power supply and providing matched current for the primary circuit of the optical coupler.

3. The alternating voltage measuring circuit according to claim 2, wherein the voltage stabilizing and supplying circuit comprises a resistance-capacitance voltage reducing stabilizing circuit and a voltage extracting module;

the output end of the resistance-capacitance voltage reduction and stabilization circuit is electrically connected with the input end of the optical coupler primary circuit, the output end of the voltage extraction module is electrically connected with the input end of the resistance-capacitance voltage reduction and stabilization circuit and the input end of the voltage comparison circuit, and the input end of the voltage extraction module is used for being electrically connected with the external alternating current power supply;

the voltage extraction module is used for extracting an alternating voltage half wave from an alternating voltage wave of the external alternating current power supply;

and the resistance-capacitance voltage reduction and stabilization circuit is used for taking voltage from the extracted half-wave of the alternating voltage and providing current for the primary circuit of the optical coupler.

4. An alternating voltage measuring circuit according to any of claims 1-3, characterized in that the measuring circuit further comprises a transition edge processing circuit;

the input end of the hopping edge processing circuit is electrically connected with the output end of the optical coupling secondary circuit, and the output end of the hopping edge processing circuit is electrically connected with the controller;

and the transition edge processing circuit is used for changing the steepness of the rising edge of the level signal and the steepness of the falling edge of the level signal and transmitting the changed level signal to the controller.

5. An alternating voltage measuring circuit according to claim 2 or 3, characterized in that the optocoupler primary circuit comprises a first resistor (R1), a second resistor (R2) and a light emitting diode (D1), and the optocoupler secondary circuit comprises a phototransistor (Q1) and a pull-up resistor (R0); wherein the first resistor (R1) is connected in parallel with the light emitting diode (D1); the collector of the phototransistor (Q1) is electrically connected with one end of the pull-up resistor (R0), the base of the phototransistor (Q1) is inductively connected with the light-emitting diode (D1), the emitter of the phototransistor (Q1) is used for connecting with a secondary reference ground end, and the other end of the pull-up resistor (R0) is used for electrically connecting with an internal power supply (V1);

when the voltage comparison circuit is the voltage stabilizing diode (P), the cathode of the light emitting diode (D1) is used for being electrically connected with the external alternating current power supply, one end of the second resistor (R2) is electrically connected with the anode of the light emitting diode (D1), the other end of the second resistor (R2) is electrically connected with the anode of the voltage stabilizing diode (P), and the cathode of the voltage stabilizing diode (P) is used for being electrically connected with the external alternating current power supply;

when the voltage comparison circuit is the adjustable voltage stabilizing circuit, the cathode of the light emitting diode (D1) is electrically connected with the output end of the adjustable voltage stabilizing circuit; one end of the second resistor (R2) is electrically connected with the positive electrode of the light-emitting diode (D1), and the other end of the second resistor (R2) is electrically connected with the output end of the voltage-stabilizing power supply circuit.

6. An alternating voltage measuring circuit according to claim 2 or 3, characterized in that the adjustable voltage regulation circuit comprises a controllable regulator supply (K), a third resistor (R3) and a fourth resistor (R4);

the cathode of the controllable voltage regulator (K) is electrically connected with the optocoupler circuit, the reference electrode of the controllable voltage regulator is electrically connected with the first end of the fourth resistor (R4) and the first end of the third resistor (R3), and the second end of the fourth resistor (R4) is electrically connected with the input end of the voltage comparison circuit;

and the second end of the third resistor (R3) and the anode of the controllable voltage regulator are connected with a primary reference ground end.

7. An alternating voltage measuring circuit according to claim 3, characterized in that said resistance-capacitance step-down voltage stabilizing circuit comprises a voltage regulator tube (Z), a capacitor (C), a fifth resistor (R5) and a first diode (D2);

one end of the fifth resistor (R5) is electrically connected with the cathode of the first diode (D2), the other end of the fifth resistor (R5), one end of the capacitor (C), the cathode of the voltage regulator tube (Z) and the other end of the second resistor (R2) are respectively electrically connected with a second internal power supply (V2), and the anode of the first diode (D2) is electrically connected with the output end of the voltage extraction module;

the other end of the capacitor (C) and the positive electrode of the voltage stabilizing tube (Z) are both used for being connected with a primary reference ground end.

8. The alternating voltage measuring circuit according to claim 4, wherein the jump edge processing circuit comprises a transistor (Q2), a sixth resistor (R6), a seventh resistor (R7) and an eighth resistor (R8);

one end of the sixth resistor (R6) is electrically connected with an output end of the optical coupler circuit, the other end of the sixth resistor (R6) is electrically connected with a base of the triode (Q2) and one end of the seventh resistor (R7), respectively, a collector of the triode (Q2) is electrically connected with one end of the eighth resistor (R8), one end of the eighth resistor (R8) is used for electrically connecting the controller, and the other end of the eighth resistor (R8) is used for electrically connecting an internal power supply (V1);

the other end of the seventh resistor (R7) and the emitter of the triode (Q2) are connected with a secondary reference ground terminal.

9. The alternating voltage measuring circuit according to claim 3, characterized in that said voltage extraction module comprises a second diode (D3);

the voltage extraction module further comprises a third diode (D4), wherein the anode of the third diode (D4) is used for connecting a primary reference ground end, the cathode of the third diode (D4) is used for electrically connecting a zero line end of the external alternating current power supply, the anode of the second diode (D3) is used for electrically connecting a live wire end of the external alternating current power supply, and the cathode of the second diode (D3) is electrically connected with the input end of the voltage comparison circuit.

10. The measuring method is applied to a measuring circuit for measuring alternating voltage, wherein the measuring circuit comprises an optical coupling circuit and a voltage comparison circuit, the optical coupling circuit comprises an optical coupling primary circuit and an optical coupling secondary circuit, and the method comprises the following steps:

the voltage comparison circuit acquires alternating current voltage of an external alternating current power supply and controls the on-off of the primary circuit of the optical coupler according to the acquired alternating current voltage of the external alternating current power supply and preset reference voltage, and the preset reference voltage is used for measuring the alternating current voltage of the external alternating current power supply;

under the control of the voltage comparison circuit, the optical coupler primary circuit outputs an optical electric signal;

the optical coupling secondary circuit senses the photoelectric signal, converts the photoelectric signal into a level signal, and outputs the level signal to the controller so as to trigger the controller to determine the voltage value of the alternating voltage of the external alternating current power supply according to the duration of receiving the level signal.

11. The method according to claim 10, wherein the measuring circuit further comprises a regulated power supply circuit;

and, the method further comprises:

the voltage-stabilizing power supply circuit extracts alternating-current voltage half waves from alternating-current voltage waves of the external alternating-current power supply and provides matched current for the primary circuit of the optical coupler.

12. The method according to claim 10 or 11, wherein the measurement circuit further comprises a transition edge processing circuit, wherein the transition edge processing circuit is disposed between the optical coupler secondary circuit and the controller;

and after the optical coupling secondary circuit senses the photoelectric signal and converts the photoelectric signal into a level signal, the method further comprises:

the transition edge processing circuit changes the steepness of the rising edge of the level signal and the steepness of the falling edge of the level signal;

wherein, the outputting the level signal to the controller to trigger the controller to determine the voltage value of the alternating current voltage of the external alternating current power supply according to the duration of receiving the level signal includes:

and the jumping edge processing circuit transmits the changed level signal to the controller so as to trigger the controller to determine the voltage value of the alternating current voltage of the external alternating current power supply according to the duration of receiving the level signal.

13. A smart device, characterized in that it comprises a measuring circuit of an alternating voltage according to any one of claims 1-9.

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