CN106841762A - Zero cross detection circuit and home appliance - Google Patents

Abstract

The invention provides a kind of zero cross detection circuit and home appliance, wherein, zero cross detection circuit includes：Transistor switch, is connected in series between the negative electrode interface of optical coupling module and the sampling end L of civil power live wire；Current-limiting resistance, current-limiting resistance is connected in series between the sampling end of the drive end of transistor switch and civil power zero line, wherein, when transistor switch is turned on, the first output end of optical coupling module exports zero cross signal to load control module.By technical scheme, the power consumption of zero cross detection circuit is reduced, and then improve the versatility of zero cross detection circuit.

Description

Zero-crossing detection circuit and home appliances

technical field

The present invention relates to the technical field of household electrical appliances, in particular to a zero-crossing detection circuit and a household electrical appliance.

Background technique

When household electrical appliances are connected to AC mains (usually including three-phase AC signals of mains zero wire N, mains live wire L and mains ground wire), it is necessary to set up a zero-crossing detection circuit to control the high-power load in household appliances. The opening point and closing point are especially used to reduce the inrush current at the moment the load is turned on, thereby reducing the risk of device damage in household appliances and grid fluctuations.

In related technologies, the connection mode of the zero-crossing detection circuit is shown in Figure 1, which specifically includes a current limiting resistor R1, an optocoupler module (or photocoupler) IC, a rectifier diode D1, a pull-up resistor R3, and an output protection resistor R4 And filter capacitor C and other devices, wherein the current limiting resistor R1 is used to control the working current I of the optocoupler module IC to satisfy 1mA≤I≤50mA.

As shown in Figure 2, the optocoupler module IC includes a light-emitting diode and a photosensitive device. The pull-up resistor R3 and the photosensitive device are connected in series between the DC source U and the ground wire GND. When the anode interface a1 of the optocoupler module IC is connected to the cathode interface a2 When the potential difference is greater than the conduction voltage of the LED, the LED turns on and emits light.

When the AC mains is reversed, the light-emitting diode is not turned on and emits light. Since the photosensitive device is under the condition of light-emitting diode and non-light-emitting, the electrical signal of the photosensitive device, such as the divided voltage value and current value, are not the same. Therefore, through the light The first output terminal a3 and the second output terminal a4 of the coupling module IC transmit the electrical signal as a trigger signal to a designated I/O interface of the processor through the output protection resistor R4 and the filter capacitor C.

However, the zero-crossing detection circuit in the related art has at least the following technical defects:

(1) When the zero-crossing detection circuit shown in Figure 1 is applied in European countries, the AC mains power is 230V/50Hz, and the power consumption of the zero-crossing detection circuit is about 0.24 watts. If it is not greater than the requirement of 0.5 watts, it has already accounted for nearly half of the power consumption.

(2) The CTR (Current Transfer Ratio, current transfer ratio) value of the optocoupler module will attenuate with the increase of temperature, so it must be ensured that the input current of the optocoupler module is greater than or equal to 1 mA, therefore, it must match the corresponding The current limiting resistors lead to poor versatility of the zero-crossing detection circuit.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

Therefore, an object of the present invention is to provide a zero-crossing detection circuit.

Another object of the present invention is to provide a household electrical appliance.

In order to achieve the above object, according to the technical solution of the first aspect of the present invention, a zero-crossing detection circuit is proposed, including: a transistor switch, connected in series between the cathode interface of the optocoupler module and the sampling terminal L of the mains live wire; A current-limiting resistor, the current-limiting resistor is connected in series between the drive end of the transistor switch and the sampling end of the mains zero line, wherein, when the transistor switch is turned on, the first output end of the optocoupler module outputs a zero-crossing signal to the load control module .

In this technical solution, the above-mentioned zero-crossing detection circuit also includes an optocoupler module, the first output terminal of the optocoupler module is connected to the load control module, and the optocoupler module and the transistor switch are used to sample the mains power. The lower transistor switch can enter a saturated state under a small current change, thereby triggering the conduction of the optocoupler module, and the optocoupler module outputs a zero-crossing signal, thereby achieving the purpose of zero-crossing detection.

It is worth pointing out that by connecting the current-limiting resistor in series with the driving end of the transistor switch, the transistor switch can obtain a smaller current under different AC mains power, which effectively reduces the power consumption of the zero-crossing detection circuit and improves the efficiency of the zero-crossing detection circuit. Versatility of the zero detection circuit.

According to the zero-crossing detection circuit of the above technical solution of the present invention, it can also have the following technical characteristics:

In the above technical solution, preferably, when the transistor switch is a triode, the driving terminal is the base of the triode, the collector of the triode is connected to the cathode interface of the optocoupler module, and the emitter of the triode is connected to the ground.

In this technical solution, when the transistor switch is a triode, the base of the triode is used as the driving terminal, the collector of the triode is connected to the cathode interface of the optocoupler module, and the emitter of the triode is grounded.

Specifically, the triode controls the conduction and cut-off of the anode interface and the cathode interface of the optocoupler module. The conduction (saturation or amplification) and cut-off of the triode are determined by the positive half cycle and negative half cycle of the sinusoidal AC mains. When the triode is NPN type When the voltage between the base and the emitter is greater than 0.7V, a very small base current can make the triode enter a saturated state, so that the optocoupler module is in a conducting state.

Among them, the triode can be selected as NPN type or PNP type according to the actual requirement of detecting the zero crossing point.

By setting the emitter of the triode connected to the sampling terminal L of the mains live wire, the base is connected to the sampling terminal of the mains neutral line through a series connected current-limiting resistor. When the positive half cycle arrives, the triode enters a saturated state, and because the base current demand of the triode is relatively small, generally in the microampere level, the resistance value of the current-limiting resistor can be very large.

Specifically, according to the power formula P=U×U/R, it can be seen that the larger the resistance R is, the smaller the power P is. Assuming that the electrical equipment using the above zero-crossing detection circuit is used in Europe, the AC mains power is 230V, and the current limiting resistor The resistance value of the circuit is 3 megohms, then the power of the circuit is P=230×230/3000000=0.0176W, which is far less than the power consumption of the existing zero-crossing detection circuit and can meet the power consumption requirement of standby.

Wherein, the current-limiting resistor can be a plurality of resistor elements connected in series and/or in parallel, or a resistor element with a relatively large resistance value.

In the above technical solution, preferably, the zero-crossing detection circuit further includes: a first diode, the anode of the first diode is connected to the emitter of the triode, and the cathode of the first diode is connected to the sampling electrode of the mains live wire. End L.

In this technical solution, a first diode is connected between the emitter of the triode and the sampling terminal L of the commercial live wire, and the anode of the first diode is connected to the emitter of the triode, and the cathode is connected to the above-mentioned commercial live wire In this way, due to the one-way conductivity of the diode, when the AC power comes in the negative half cycle of the AC power, the first diode is in the cut-off state, and the triode exits the saturation state at this time, so that the optocoupler module is in In the cut-off state, when the AC mains arrives in the positive half cycle of the AC mains, the current can pass through the first diode. At this time, the triode enters a saturated state, which makes the optocoupler module conduct, so that the output terminal of the optocoupler module can be collected To determine the time of the zero crossing of the mains power.

Among them, the unidirectional conductivity of the diode is the function of the PN junction in the diode. When the reverse voltage is large, the PN junction may be damaged, that is, when the diode is in the cut-off state, if the AC power exceeds the reverse strike of the diode When the diode is reversely broken down, the current in the circuit may increase sharply, which may damage other components in the zero-crossing detection circuit.

In the above technical solution, preferably, the zero-crossing detection circuit further includes: a second diode, the cathode of the second diode is connected to the base of the triode, and the anode of the second diode is connected to the emitter of the triode.

In this technical scheme, by connecting a second diode between the base and the emitter of the triode, and the cathode of the second diode is connected to the base of the triode, and the anode is connected to the emitter of the triode, The possibility of reverse breakdown of the triode is reduced, and the reliability of the zero-crossing detection circuit is improved.

In any of the above technical solutions, preferably, the resistance of the current limiting resistor is greater than or equal to 3 megohms.

In this technical solution, since the base current demand of the triode is relatively small, generally in the microampere level, in order to reduce the power consumption of the zero-crossing detection circuit, it is necessary to reduce the current value in the zero-crossing detection circuit, so the current limiting resistor The resistance value is very large.

Among them, when the resistance value of the current-limiting resistor is greater than or equal to 3 megohms, according to the power calculation formula, it can be concluded that the power consumption of the zero-crossing detection circuit is far less than the international power consumption for different AC mains in various countries in the world. Standby power consumption requirements of home appliances.

For example, when the electrical equipment with the above-mentioned zero-crossing detection circuit is used in Europe, the AC mains power is 230V, and the resistance value of the current-limiting resistor is 3 megohms, then the power of the circuit is P=230×230/3000000=0.0176W , which is far less than the power consumption of the existing zero-crossing detection circuit, and can meet the requirement of standby power consumption. Wherein, the current-limiting resistor can be in the form of multiple resistor elements connected in series and/or in parallel, or can use one resistor, which is determined according to the specific practice of the present invention.

In the above technical solution, preferably, the optocoupler module includes a light-emitting diode and a photosensitive device oppositely arranged, the first output end of the optocoupler module is connected to the first end of the photosensitive device, and the second end of the photosensitive device is connected to the ground wire, The zero-crossing detection circuit also includes: a high-frequency transformer winding; a third diode, the anode of the third diode is connected to the first output end of the high-frequency transformer winding, and the cathode of the third diode is connected to the anode interface ; Electrolytic capacitor, the positive electrode of the electrolytic capacitor is connected to the negative electrode of the third diode, and the negative electrode of the electrolytic capacitor is connected to the ground wire and the second output terminal of the high-frequency transformer winding simultaneously, wherein, the negative electrode of the third diode and the electrolytic The positive electrode of the capacitor is connected to the anode interface of the optocoupler module at the same time, and is used to provide light-emitting electrical signals to the light-emitting diode, the cathode interface is connected to the cathode of the light-emitting diode, and the anode interface is connected to the anode of the light-emitting diode.

In this technical solution, the optocoupler module includes a light-emitting diode and a photosensitive device arranged opposite to each other, and is an electrical-optical-electrical conversion device. The light emitting source and the light receiver are located in the same airtight housing and are isolated from each other by a transparent insulator. The commonly used light source is a light-emitting diode, and the light receiver is a photosensitive device, usually a photoresistor.

The light-emitting diode emits light of a specific wavelength under the action of the input electrical signal, which is received by the photosensitive device to generate a photocurrent output. The input and output of the optocoupler module are electrically isolated, and the transmission of the electrical signal is unidirectional. Therefore, The light-emitting diode has a good isolation effect on the input and output electrical signals, and has good anti-interference ability, which reduces the unstable signal caused by external interference or fluctuation interference in the zero-crossing detection circuit.

Among them, the voltage generated by multiple sets of high-frequency transformer windings (one main winding and multiple auxiliary windings) is used as the supply voltage of the optocoupler module, and a set of high-frequency transformer windings can also be used to drive the light-emitting diode to emit light.

Specifically, due to the high operating frequency of the high-frequency transformer winding, it can be divided into several grades. In the case of high switching frequency, the ripple of the output voltage is small, and the voltage is smooth and stable. At the same time, because the operating frequency is high , the voltage transmission efficiency is higher, and the power consumption of the zero-crossing detection circuit can be further reduced.

In addition, the zero-crossing detection circuit also includes a third diode and an electrolytic capacitor, which are used to rectify and filter the voltage generated by the high-frequency transformer winding, so as to protect the optocoupler module and reduce the frequency of the optocoupler module being transformed by high frequency. The possibility of damage caused by the large instantaneous current generated by the winding, thereby improving the reliability of the zero-crossing detection circuit.

In the above technical solution, preferably, the second output terminal of the optocoupler module is connected to the ground wire, and the zero-crossing detection circuit further includes: a DC source connected to the first output terminal of the optocoupler module; a pull-up resistor connected in series to Between the DC source and the first output terminal of the optocoupler module; the output protection resistor is connected in series between the first output terminal of the optocoupler module and the load control module; the filter capacitor is connected in series between the load control module and the ground wire .

In this technical solution, by setting the pull-up resistor in series with the photosensitive device, that is, when the photosensitive device is turned on, the pull-up resistor plays the role of voltage division and protection. Connecting the output protection resistors in series between the load control modules can further reduce the current reaching the load control modules and reduce the possibility of the current causing damage to the load control modules. A filter capacitor can also be connected in series between the load control module and the ground wire to reduce the impact of voltage fluctuations in the circuit on the load control module and improve the reliability of the zero-crossing detection circuit.

In the above technical solution, preferably, the output voltage range of the direct current source is 3-24 volts.

In this technical solution, the DC source can be set to a DC source of 3-24 volts, wherein, when the DC source voltage is greater than 5V, it is necessary to use a triode for isolation to reduce the damage caused by a greater voltage to the zero-crossing detection circuit Possibility, but the power consumption of the circuit will increase. The voltage range of the DC source is preferably 3.0-5V, and a DC source with a DC source of 3.5V is usually used.

In the above technical solution, preferably, the zero-crossing detection circuit further includes: an anode protection resistor connected in series between the cathode of the third diode and the anode interface of the optocoupler module.

In this technical solution, the anode protection resistor is connected in series between the cathode of the third diode and the anode interface of the optocoupler module, which can divide the supply voltage transmitted by the high-frequency transformer winding, thereby reducing the high-frequency transformer The possibility of damaging the light-emitting diodes by the current generated by the voltage winding improves the reliability of the zero-crossing detection circuit.

According to the technical solution of the second aspect of the present invention, a household electrical appliance is also proposed, including: a zero-crossing detection circuit as proposed in any one of the technical solutions of the first aspect of the present invention, therefore, the technical solution of the second aspect of the present invention The proposed home appliance has all the beneficial effects of the zero-crossing detection circuit proposed in the technical solution of the first aspect of the present invention, and will not be repeated here.

Additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

FIG. 1 shows a schematic diagram of a circuit structure of a zero-crossing detection circuit in the prior art;

FIG. 2 shows a schematic diagram of a voltage waveform of a zero-crossing detection circuit in the prior art;

FIG. 3 shows a schematic diagram of the circuit structure of Embodiment 1 of the zero-crossing detection circuit according to the present invention;

FIG. 4 shows a schematic diagram of the circuit structure of Embodiment 2 of the zero-crossing detection circuit according to the present invention.

detailed description

In order to understand the above-mentioned purpose, features and advantages of the present invention more clearly, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the case of no conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described here. Therefore, the protection scope of the present invention is not limited by the specific details disclosed below. EXAMPLE LIMITATIONS.

On the basis of the existing zero-crossing detection circuit shown in FIG. 1 and FIG. 2 , the zero-crossing detection circuit according to an embodiment of the present invention will be specifically described below in conjunction with FIG. 3 and FIG. 4 .

Embodiment one:

FIG. 3 shows a schematic diagram of the circuit structure of Embodiment 1 of the zero-crossing detection circuit according to the present invention.

As shown in Figure 3, the zero-crossing detection circuit according to Embodiment 1 of the present invention includes: a transistor switch Q, connected in series between the cathode interface a2 of the optocoupler module IC and the sampling terminal L of the mains live wire; R1, the current limiting resistor R1 is connected in series between the driving terminal of the transistor switch Q and the sampling terminal N of the mains neutral line, wherein, when the transistor switch Q is turned on, the first output terminal a3 of the optocoupler module IC is connected to the load control module Output zero-crossing signal (I/O port represents a general interface of the load control module).

In this technical solution, the above-mentioned zero-crossing detection circuit also includes an optocoupler module IC, the first output terminal a3 of the optocoupler module IC is connected to the load control module, combined with the optocoupler module IC and the transistor switch Q to sample the mains power, in Under the action of the current-limiting resistor R1, the transistor switch Q can enter a saturated state under a small current change, thereby triggering the conduction of the optocoupler module IC under the action of the voltage U2 connected to the first output terminal a3 of the optocoupler module IC, and the light The coupling module IC outputs a zero-crossing signal, thereby achieving the purpose of zero-crossing detection.

It is worth noting that by connecting the current-limiting resistor R1 in series with the driving terminal of the transistor switch Q, the transistor switch Q can obtain a smaller current under different AC mains power, effectively reducing the power consumption of the zero-crossing detection circuit. The versatility of the zero-crossing detection circuit is improved.

Among them, the transistor switch Q can be a PNP structure, an NPN structure, or a MOS transistor, but the control method of the entire zero-crossing detection circuit is the same, all based on the positive and negative half cycles of the sinusoidal AC mains (including the sinusoidal AC Mains full-wave and half-wave mode) to make the transistor switch Q work in the conduction (saturation or amplification) or cut-off state, so as to determine the conduction or cut-off of the optocoupler module IC, and then determine the output level of the optocoupler module IC High and low, determine whether to cross zero. The current-limiting resistor R1 can be a plurality of resistor elements connected in series and/or in parallel, or a resistor element with a larger resistance value, but the purpose is to achieve the requirement of low power consumption by selecting a resistor with a larger resistance value.

In addition, under the AC mains, a small change in the current in the driving end of the transistor switch Q can make the transistor switch Q enter a saturated state, therefore, between the driving end of the transistor switch Q and the sampling end N of the mains neutral line The current-limiting resistor R1 is connected in series to reduce the current in the zero-crossing detection circuit, and the power of the zero-crossing detection circuit can be reduced under the premise that the transistor switch Q can enter a saturated state to control the optocoupler module IC, thereby reducing the standby state The power consumption of the electrical equipment where the circuit is located.

Further, due to the existence of the current-limiting resistor R1, the current in the zero-crossing detection circuit can be limited to a very small value for the AC mains in different countries, so that the power consumption of the zero-crossing detection circuit can be reduced to the required range, thereby improving The versatility of the zero-crossing detection circuit.

Embodiment two:

FIG. 4 shows a schematic diagram of the circuit structure of Embodiment 2 of the zero-crossing detection circuit according to the present invention.

As shown in Figure 4, on the basis of the zero-crossing detection circuit in Embodiment 1, preferably, when the transistor switch Q is a triode, the drive terminal is the base of the triode, and the collector of the triode is connected to the cathode interface of the optocoupler module IC a2, the emitter of the triode is connected to the ground wire.

In this technical solution, when the transistor switch Q is a triode, the base of the triode is used as the driving terminal, the collector of the triode is connected to the cathode interface a2 of the optocoupler module IC, and the emitter of the triode is grounded.

Specifically, the triode controls the conduction and cut-off of the anode interface a1 and the cathode interface a2 of the optocoupler module IC. When it is NPN type, when the voltage between its base and emitter is greater than 0.7V, a very small base current can make the triode enter a saturated state, so that the optocoupler module IC is in a conducting state.

Among them, the triode can be selected as NPN type or PNP type according to the actual requirement of detecting the zero crossing point.

By setting the emitter of the triode connected to the sampling terminal L of the live line of the mains, and the base connected to the sampling terminal N of the neutral line of the mains through a series-connected current-limiting resistor R1, for any country’s mains, it can be used in the city. When the positive half cycle of electricity arrives, the triode enters into a saturated state, and because the base current demand of the triode is relatively small, generally in the microampere level, the resistance value of the current limiting resistor R1 can be very large.

Specifically, according to the power formula P=U×U/R, it can be seen that the larger the resistance R is, the smaller the power P is. Assuming that the electrical equipment using the above zero-crossing detection circuit is used in Europe, the AC mains power is 230V, and the current limiting resistor The resistance value of R1 is 3 megohm, then the power of the circuit is P=230×230/3000000=0.0176W, which is far less than the power consumption of the existing zero-crossing detection circuit, and can meet the standby power consumption requirement.

Wherein, the current limiting resistor R1 may be a plurality of resistor elements connected in series and/or in parallel, or may be a resistor element with a relatively large resistance value.

In the above technical solution, preferably, the zero-crossing detection circuit further includes: a first diode D1, the anode of the first diode D1 is connected to the emitter of the triode, and the cathode of the first diode D1 is connected to the mains The sampling end L of the live wire.

In this technical solution, the first diode D1 is connected between the emitter of the triode and the sampling terminal L of the mains live wire, and the anode of the first diode D1 is connected to the emitter of the triode, and the cathode is connected to the above-mentioned market The sampling terminal L of the electric fire wire, so, due to the unidirectional conductivity of the diode, when the negative half cycle of the AC mains arrives, the first diode D1 is in the cut-off state, and the triode exits the saturation state at this time, so that the optocoupler module IC is in In the cut-off state, when the positive half cycle of the AC power comes, the current can pass through the first diode D1, and the triode enters a saturated state at this time, making the optocoupler module IC conduct, so that it can be collected according to the output terminal of the optocoupler module IC. The change of the level state of the grid can judge the time of the zero crossing of the mains power.

Among them, the unidirectional conductivity of the diode is the function of the PN junction in the diode. When the reverse voltage is large, the PN junction may be damaged, that is, when the diode is in the cut-off state, if the AC power exceeds the reverse strike of the diode When the diode is reversely broken down, the current in the circuit may increase sharply, which may damage other components in the zero-crossing detection circuit.

In the above technical solution, preferably, the zero-crossing detection circuit further includes: a second diode D2, the cathode of the second diode D2 is connected to the base of the triode, and the anode of the second diode D2 is connected to the base of the triode. emitter.

In this technical solution, the second diode D2 is connected between the base and the emitter of the triode, and the cathode of the second diode D2 is connected to the base of the triode, and the anode is connected to the emitter of the triode. pole, which reduces the possibility of the triode being reversely broken down and improves the reliability of the zero-crossing detection circuit.

In any of the above technical solutions, preferably, the resistance of the current limiting resistor R1 is greater than or equal to 3 megohms.

In this technical solution, since the base current demand of the triode is relatively small, generally in the microampere level, in order to reduce the power consumption of the zero-crossing detection circuit, it is necessary to reduce the current value in the zero-crossing detection circuit, so the current limiting resistor R1 The resistance value is obtained very large.

Among them, when the resistance value of the current-limiting resistor R1 is greater than or equal to 3 megohms, according to the power calculation formula, it can be concluded that the power consumption of the zero-crossing detection circuit is far less than the international power consumption for different AC mains in various countries in the world. Requirements for standby power consumption of home appliances.

For example, when the electrical equipment with the above-mentioned zero-crossing detection circuit is used in Europe, the AC mains power is 230V, and the resistance value of the current limiting resistor R1 is 3 megohms, then the power of the circuit is P=230×230/3000000=0.0176 W, which is far less than the power consumption of the existing zero-crossing detection circuit, and can meet the power consumption requirement of standby. Wherein, the current-limiting resistor R1 can be in the form of a plurality of resistor elements connected in series and/or in parallel, or can use one resistor, which is determined according to the specific practice of the present invention.

In the above technical solution, preferably, the optocoupler module IC includes a light-emitting diode LED and a photosensitive device PR arranged oppositely, the first output terminal a3 of the optocoupler module IC is connected to the first end of the photosensitive device PR, and the first end a3 of the photosensitive device PR The two terminals are connected to the ground wire GND, and the zero-crossing detection circuit also includes: a high-frequency transformer winding T1 (an auxiliary winding T2 can be additionally set); a third diode D3, and the anode of the third diode D3 is connected to the high-frequency transformer The first output terminal d of the pressure winding, the cathode c of the third diode D3 is connected to the anode interface a1; the electrolytic capacitor E, the positive pole of the electrolytic capacitor E is connected to the cathode c of the third diode D3, and the negative pole of the electrolytic capacitor E Simultaneously connected to the ground wire and the second output terminal b of the high-frequency transformer winding, wherein, the cathode of the third diode D3 and the anode of the electrolytic capacitor are simultaneously connected to the anode interface a1 of the optocoupler module IC for feeding the light-emitting diode The LED provides light-emitting electrical signals, the cathode interface a2 is connected to the cathode of the light-emitting diode LED, and the anode interface a1 is connected to the anode of the light-emitting diode LED.

In this technical solution, the optocoupler module IC includes a light-emitting diode LED and a photosensitive device PR arranged opposite to each other. It is an electrical-optical-electrical conversion device. Insulator isolation, the commonly used light source is a light-emitting diode LED, and the light receiver is a photosensitive device PR, usually a photoresistor.

The light-emitting diode LED emits light of a specific wavelength under the action of the input electrical signal, which is received by the photosensitive device PR to generate a photocurrent output. The input and output of the optocoupler module IC are electrically isolated, and the transmission of electrical signals is unidirectional. Therefore, the light-emitting diode LED has a good isolation effect on the input and output electrical signals, and has good anti-interference ability, which reduces the unstable signal caused by external interference or fluctuation interference in the zero-crossing detection circuit.

Among them, multiple sets of voltage generated by multiple sets of high-frequency transformer windings T1 and additional auxiliary windings T2 are used as the supply voltage of the optocoupler module IC, and a set of high-frequency transformer windings T1 can also be used to drive the light-emitting diode LED glow.

Specifically, due to the high operating frequency of the high-frequency transformer winding T1, it can be divided into several grades. In the case of high switching frequency, the ripple of the output voltage is small, and the voltage is smooth and stable. At the same time, because the operating frequency is relatively high High, the transmission efficiency of the voltage is higher, and the power consumption of the zero-crossing detection circuit can be further reduced.

In addition, the zero-crossing detection circuit also includes a third diode D3 and an electrolytic capacitor E, which are used to rectify and filter the voltage generated by the high-frequency transformer winding T1, thereby protecting the optocoupler module IC and reducing the voltage of the optocoupler module IC. The possibility of being damaged by the large instantaneous current generated by the high-frequency transformer winding T1, thereby improving the reliability of the zero-crossing detection circuit.

In the above technical solution, preferably, the second output terminal a4 of the optocoupler module IC is connected to the ground wire GND, and the zero-crossing detection circuit further includes: a DC source U1 connected to the first output terminal a3 of the optocoupler module IC; The pull resistor R3 is connected in series between the DC source U1 and the first output terminal a3 of the optocoupler module IC; the output protection resistor R4 is connected in series between the first output terminal a3 of the optocoupler module IC and the load control module; the filter The capacitor C is connected in series between the load control module and the ground wire GND.

In this technical solution, by setting the pull-up resistor R3 in series with the photosensitive device PR, that is, when the photosensitive device PR is turned on, the pull-up resistor R3 plays the role of voltage division and protection. The output protection resistor R4 is connected in series between the first output terminal a3 and the load control module, which can further reduce the current reaching the load control module and reduce the possibility of the current causing damage to the load control module. A filter capacitor C can also be connected in series between the load control module and the ground wire GND to reduce the impact of voltage fluctuations in the circuit on the load control module and improve the reliability of the zero-crossing detection circuit.

In the above technical solution, preferably, the output voltage range of the direct current source U1 is 3-24 volts.

In this technical solution, the DC source U1 can be set as a DC source of 3 to 24 volts, wherein, when the voltage of the DC source U1 is greater than 5V, it is necessary to use a triode for isolation to reduce the impact of a greater voltage on the zero-crossing detection circuit. The possibility of damage, but the power consumption of the circuit will increase. The voltage range of the DC source is preferably 3.0-5V, and the DC source U1 with a DC source of 3.5V is usually used.

In the above technical solution, preferably, the zero-crossing detection circuit further includes: an anode protection resistor R2 connected in series between the cathode of the third diode D3 and the anode interface a1 of the optocoupler module IC.

In this technical solution, the anode protection resistor R2 is connected in series between the cathode of the third diode D3 and the anode interface a1 of the optocoupler module IC, which can divide the supply voltage transmitted by the high-frequency transformer winding T1, thereby The possibility of damaging the light-emitting diode LED by the current generated by the high-frequency transformer winding T1 is reduced, and the reliability of the zero-crossing detection circuit is improved.

Among them, home appliances include but are not limited to refrigerators, washing machines, rice cookers, induction cookers and televisions.

It is worth pointing out that the zero-crossing detection circuit in this technical solution is built by discrete components and belongs to an analog signal circuit. Therefore, the circuit has a relatively strong anti-leakage interference ability. Among them, the leakage wave interference refers to the microwave equipment in the microwave working process, because the microwave will reflect the characteristics of the metal, and the leakage wave interference signal of about 0.1 to 3 milliwatts will generally be generated at the place where the circuit control board is installed, which can be radiated through space. Directly acting on the component body of the circuit control board, it will have a greater impact on relatively sensitive devices such as comparators, making them work abnormally.

The above describes the embodiments of the present invention in detail in conjunction with the accompanying drawings. Considering the technical problems of high power consumption and poor circuit versatility of the existing zero-crossing detection circuit proposed in the related art, the present invention proposes a zero-crossing detection scheme. By connecting the current-limiting resistor and the driving end of the transistor switch in series, the transistor switch can obtain a smaller current under different AC mains, effectively reducing the power consumption of the zero-crossing detection circuit and improving the versatility of the zero-crossing detection circuit .

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A zero-crossing detection circuit, the zero-crossing detection circuit includes an optocoupler module, the first output of the optocoupler module is connected to the load control module, it is characterized in that the zero-crossing detection circuit also includes: A transistor switch is connected in series between the cathode interface of the optocoupler module and the sampling end of the mains live wire; A current-limiting resistor, the current-limiting resistor is connected in series between the driving terminal of the transistor switch and the sampling terminal of the neutral line of the commercial power, Wherein, when the transistor switch is turned on, the first output terminal of the optocoupler module outputs a zero-crossing signal to the load control module. 2. The zero-crossing detection circuit according to claim 1, characterized in that, When the transistor switch is a triode, the driving terminal is the base of the triode, the collector of the triode is connected to the anode interface of the optocoupler module, and the emitter of the triode is connected to the ground. 3. The zero-crossing detection circuit according to claim 2, further comprising: A first diode, the anode of the first diode is connected to the emitter of the triode, and the cathode of the first diode is connected to the sampling terminal of the mains live line. 4. The zero-crossing detection circuit according to claim 2, further comprising: A second diode, the anode of the second diode is connected to the base of the triode, and the cathode of the second diode is connected to the emitter of the triode. 5. The zero-crossing detection circuit according to any one of claims 1 to 4, characterized in that, The resistance value of the current limiting resistor is greater than or equal to 3 megohm. 6. The zero-crossing detection circuit according to claim 5, characterized in that, The optocoupler module includes a light-emitting diode and a photosensitive device oppositely arranged, the first output end of the optocoupler module is connected to the first end of the photosensitive device, and the second end of the photosensitive device is connected to the ground wire, so The zero-crossing detection circuit also includes: High frequency transformer winding; a third diode, the anode of the third diode is connected to the first output end of the high-frequency transformer winding, and the cathode of the third diode is connected to the anode interface; An electrolytic capacitor, the anode of the electrolytic capacitor is connected to the anode of the third diode, and the negative electrode of the electrolytic capacitor is connected to the ground wire and the second output end of the high-frequency transformer winding, Wherein, the anode of the third diode and the anode of the electrolytic capacitor are connected to the anode interface of the optocoupler module at the same time, for providing light-emitting electrical signals to the light-emitting diode, and the cathode interface is connected to the The cathode of the light emitting diode, the anode interface is connected to the anode of the light emitting diode. 7. The zero-crossing detection circuit according to claim 6, wherein the second output terminal of the optocoupler module is connected to the ground wire, and the zero-crossing detection circuit further comprises: a DC source connected to the first output end of the optocoupler module; a pull-up resistor connected in series between the DC source and the first output terminal of the optocoupler module; an output protection resistor connected in series between the first output end of the optocoupler module and the load control module; The filter capacitor is connected in series between the load control module and the ground. 8. The zero-crossing detection circuit according to claim 7, characterized in that, The output voltage range of the direct current source is 3-24 volts. 9. The zero-crossing detection circuit according to any one of claims 6 to 8, further comprising: The anode protection resistor is connected in series between the anode of the third diode and the anode interface of the optocoupler module. 10. A household electrical appliance, characterized in that it comprises: The zero-crossing detection circuit as claimed in any one of claims 1-9.