WO2021212839A1 - Electric leakage detection circuit, electric leakage protection circuit, and household appliance - Google Patents

Abstract

An electric leakage detection circuit (101), an electric leakage protection circuit (10), and a household appliance. The electric leakage detection circuit (101) comprises a charged conductor (G) with an alternating current, and a connecting end (H) for connecting to a conductor (B) to be tested, wherein the connecting end (H) is connected to a voltage detection circuit; the voltage detection circuit comprises a first coupling capacitor (C1), a sampling resistor (R1) and a second coupling capacitor (C2) which are successively connected; and the first coupling capacitor (C1) is connected to the conductor (B) to be tested, and the second coupling capacitor (C2) is grounded. By means of adding a capacitor structure with a coupling property to the electric leakage detection circuit (101), detection reference points of voltages at two ends of the sampling resistor (R1) form a relatively strong and stable coupling with a reference potential, and therefore, the measurement is stable and reliable.

Description

A leakage detection circuit, a leakage protection circuit and household appliances Technical field

The invention belongs to the field of household appliances, and specifically relates to a leakage detection circuit, a leakage protection circuit and a household appliance.

Background technique

Household appliances free people from arduous, trivial, and time-consuming housework, create a more comfortable and beautiful life and working environment that is more conducive to physical and mental health, and provide a variety of cultural and entertainment conditions. It has become a modern family Necessities of life.

Due to the requirements of installation strength and safety and reliability, some household appliances have shells made of metal processing. The power supply of household appliances is provided by strong electricity, which is directly connected to the power terminal of the household appliance. If the internal equipment of the household appliance leaks due to aging or breakage of the insulation, when the metal shell grounding fails, or effective grounding is not achieved When a user touches the metal shell, it will bring a safety hazard to the user. Therefore, a leakage detection and protection device is usually provided on the household electrical appliance or the household electrical connection terminal in the user's home.

In the prior art, the reference potential point for capacitance-sensing electrical measurement devices, such as non-contact electrical test pens, leakage induction modules in household appliances, etc., is generally the floor of the circuit board, and there is no substantial reference potential. The ground capacitance is uncertain, the anti-interference ability is poor, and it is greatly affected by the environment. Factors such as whether it is held or not have an impact on it.

However, if the reference point acquisition method is used for electrical connection with the neutral line, the detection circuit will be energized with strong current, which will cause certain difficulties in isolation of the strong current, and it is difficult for the product to comply with safety regulations.

In view of this, the present invention is proposed.

Summary of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a leakage detection circuit. By adding a capacitive structure with coupling characteristics in the leakage detection circuit, the voltage detection reference point and the reference potential form a stronger and more Stable coupling makes the measurement stable and reliable.

Another object of the present invention is to provide a leakage protection circuit including the above-mentioned leakage detection circuit.

Another object of the present invention is to provide a household appliance including the above-mentioned leakage detection circuit and/or leakage protection circuit.

In order to solve the above technical problems, the basic idea of the technical solution adopted by the present invention is:

A leakage detection circuit includes a live conductor with alternating current and a connecting end for connecting with the conductor under test. The connecting end is connected with a voltage detection circuit; the voltage detection circuit includes a first coupling capacitor connected in sequence, Sampling resistor and second coupling capacitor;

The first coupling capacitor is connected to the conductor under test, and the second coupling capacitor is grounded.

Further, a voltage dividing resistor is also provided between the first coupling capacitor and the sampling resistor.

Preferably, the first coupling capacitor and/or the second coupling capacitor are electronic components with capacitive characteristics, or capacitors formed by two metal structures close to each other.

Further, it also includes a voltage collection circuit, which is connected to both ends of the sampling resistor, and is used to detect the voltage at both ends of the sampling resistor.

Further, the charged conductor has a first state and a second state,

When the voltage across the sampling resistor is lower than the set threshold, the live conductor is in the first state, and at this time, the live conductor does not leak;

When the voltage across the sampling resistor is greater than or equal to the set threshold, the charged conductor is in the second state. At this time, the charged conductor is leaking.

A leakage protection circuit includes the above-mentioned leakage detection circuit.

Further, it also includes a detection circuit, which is connected to both ends of the sampling resistor, and is used to detect whether the voltage at both ends of the sampling resistor is greater than a set threshold.

Further, the detection circuit includes a voltage conditioning circuit, a comparison circuit, a warning circuit and/or a switch circuit; wherein

The voltage conditioning circuit is connected to both ends of the sampling resistor, and is used to adjust the voltage at both ends of the sampling resistor and output to the comparison circuit;

The comparison circuit is used to compare the conditioned voltage with the reference voltage of the comparison circuit, and output the comparison result to the warning circuit and/or the switch circuit;

The warning circuit sends out warning information according to the comparison result; and/or, the switch circuit is disconnected or connected according to the comparison result.

A household appliance characterized by comprising the above-mentioned leakage detection circuit, and/or the above-mentioned leakage protection circuit.

Further, the household appliance is a gas water heater, an electric water heater or a heat pump water heater.

After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art.

The scheme adopted by the present invention uses the neutral line or the ground line as the reference potential, and by setting a second coupling capacitor with coupling characteristics, the reference point on the circuit is coupled to the AC neutral line using a capacitor structure, so that the voltage across the sampling resistor is detected At the time, the reference point and the reference potential form a strong and stable coupling, making the reference point of the voltage acquisition circuit a reliable reference, making the measurement stable and reliable, and avoiding "missing but not reporting" or "not missing false alarms" on live conductors. Case.

The specific embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings.

Description of the drawings

The accompanying drawings are used as a part of the present invention to provide a further understanding of the present invention. The exemplary embodiments of the present invention and the description thereof are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings in the following description are only some embodiments, and for those of ordinary skill in the art, other drawings can be obtained from these drawings without creative work. In the attached picture:

Figure 1 is a schematic diagram of the circuit structure of the leakage detection circuit of the present invention;

2 is a schematic diagram of the circuit structure of the leakage protection circuit of the present invention;

3 is a schematic diagram of functional modules of an embodiment of the leakage protection circuit of the present invention;

4 is a schematic diagram of functional modules of another embodiment of the leakage protection circuit of the present invention;

In the figure: 10, leakage protection circuit; 101, leakage detection circuit; 102, detection circuit; 1021, voltage conditioning circuit; 1022, comparison circuit; 1023, warning circuit; 1024, switch circuit;

A. Leakage point; B. Conductor under test; C1, first coupling capacitor; C2, second coupling capacitor; L, live wire; D, access point; E, reference point; F, reference potential point; N, zero line ; R1, sampling resistor; R2, voltage divider resistance; T, transformer; G, live conductor; H, connecting terminal.

It should be noted that these drawings and text descriptions are not intended to limit the scope of the present invention in any way, but to explain the concept of the present invention for those skilled in the art by referring to specific embodiments.

Detailed ways

In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention. , But not used to limit the scope of the present invention.

In the description of the present invention, it should be noted that the terms "up", "down", "front", "rear", "left", "right", "vertical", "horizontal," "inner," and "outer" indicate the orientation or position The relationship is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, therefore It cannot be understood as a limitation to the present invention.

In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be interpreted broadly. For example, it can be a fixed connection or a detachable connection. Or integrally connected; it can be mechanically or electrically connected; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above-mentioned terms in the present invention can be understood in specific situations.

As shown in Figures 1 to 4, the present invention provides a leakage detection circuit, a leakage protection circuit and a household appliance.

FIG. 1 shows a schematic diagram of the circuit structure of the leakage detection circuit 101. The leakage detection circuit 101 includes a live conductor G with alternating current, a connection terminal H is provided on the conductor B under test, and a voltage detection circuit is connected to the connection terminal H; the voltage detection circuit includes a first coupling capacitor connected in sequence C1, a sampling resistor R1, and a second coupling capacitor C2; the first coupling capacitor C1 is connected to the conductor B under test, and the second coupling capacitor C2 is grounded.

The intersection of the sampling resistor R1 and the second coupling capacitor C2 constitutes a reference point E for detecting the voltage across the sampling resistor R1.

The charged conductor G has a first state and a second state. When the voltage across the sampling resistor R1 is less than the set threshold, the charged conductor G is in the first state. At this time, the charged conductor G does not leak. The charged conductor G is equivalent to disconnection from the measured conductor B; when the voltage across the sampling resistor R1 is greater than or equal to the set threshold, the charged conductor G is in the second state. At this time, the charged conductor G is leaking , Which is equivalent to that the live conductor G is connected to the conductor B under test.

In detail, as shown in Figure 1, the circuit structure includes the power system, which includes the earth, the output winding of the transformer T, the live wire L, the live conductor G, and the conductor B under test. Among them, the transformer T specifically refers to a transformer whose neutral point is grounded. The live conductor is connected to the live wire, so the live conductor has an alternating voltage to the earth.

When there is no leakage of the charged conductor G, the voltage across the sampling resistor R1 in the voltage detection circuit is less than the set threshold. At this time, the charged conductor G and the measured conductor B are in the first state, that is, the charged conductor G and If the conductor B to be tested is disconnected, then no current will flow through the voltage detection circuit connected between the connection terminal H and the conductor B to be tested, or the current will be very small.

When the leakage of the charged conductor G occurs, it is equivalent to the connection between the charged conductor G and the measured conductor B at the leakage point A. At this time, the conductive between the charged conductor G and the measured conductor B, then the current in the charged conductor G It will flow through the voltage detection circuit through the connection terminal H and form a loop with the earth. There will be a potential difference between the access point D of the sampling resistor R1 and the reference point E in the voltage detection circuit, that is, the two ends of the sampling resistor R1 The voltage is greater than or equal to the set threshold. At this time, it means that there is current passing through the conductor B under test.

Therefore, it can be determined whether there is a leakage point in the charged conductor G according to whether the AC voltage collected by the sampling resistor is higher than a certain set threshold.

The measured conductor B can be the housing of a household appliance or a conductor that should not be charged but may be charged. For example, when the measured conductor B is the housing of a household appliance, when the insulating layer of the live conductor G is damaged, a leakage point A appears on the live conductor G, so that the measured conductor B is the housing of the household appliance and the live conductor G At this time, if the user accidentally touches the shell, there will be a danger of electric shock.

When the voltage detection circuit is connected to the charged conductor G, since the first coupling capacitor C1 and the second coupling capacitor C2 have the characteristics of "passing and blocking", the charged conductor G, the voltage detection circuit and the ground form Loop with current.

At this time, the two ends of the sampling resistor R1 have a certain voltage, and the voltage at the two ends of the sampling resistor R1 can be detected by connecting a voltmeter at both ends of the sampling resistor R1. For example, when using a multimeter to detect the voltage across the sampling resistor R1, connect the two terminals of the multimeter to the two ends of the sampling resistor R1, and the multimeter will display the specific value of the voltage across the sampling resistor R1 at this time.

In other words, if you use a multimeter to detect that there is voltage at both ends of the sampling resistor R1, it means that the charged conductor G is leaking, and the housing of the household appliance may have been charged. If you touch the housing at this time, there will be a risk of electric shock. .

Conversely, if a multimeter is used to detect the voltage at both ends of the sampling resistor R1, no voltage is detected, indicating that there is no leakage in the conduction, and the casing is not electrified. The risk of electric shock when the user touches the casing is very small, almost no.

In the leakage detection circuit 101 of the present invention, when a leakage occurs, one end of the voltage detection circuit is connected to the charged conductor G, and the other end is grounded. The intersection of the sampling resistor R1 and the second coupling capacitor C2 is the reference point E when the voltage across the sampling resistor R1 is obtained.

The above process is the process of detecting whether there is leakage of the charged conductor G. In this process, the scheme adopted by the present invention takes the earth as the reference potential point, and sets the second coupling capacitor C2 to detect the voltage at both ends of the sampling resistor R1. A strong and stable coupling is formed between the reference point E and the reference potential point, so that the reference point E of the voltage acquisition circuit becomes a reliable reference.

Further, by setting the second coupling capacitor C2, a circuit loop combining electrical connection and capacitive coupling is completely set up, so that the measurement is stable and reliable.

In a further solution, a voltage divider resistor R2 is further provided between the first coupling capacitor C1 and the sampling resistor R1.

In detail, the function of setting the voltage divider resistor R2 is to make the voltage value at both ends of the sampling resistor R1 smaller, so as to facilitate the subsequent collection of the voltage of the sampling resistor R1 for comparison with the comparator.

For example, when using the transistor on-voltage as the comparison voltage, the required threshold should be around 0.7 volts.

In the above solution, setting the voltage divider resistor R2 makes it more accurate to obtain the voltage across the sampling resistor R1, which is convenient for implementation and debugging.

In a further solution, the second coupling capacitor C2 may be an electronic component with capacitive characteristics, or a capacitor formed by two metal structures close to each other.

In detail, the function of the second coupling capacitor C2 is to make the two ends of the second coupling capacitor C2, that is, the reference point E and the reference potential point F, form a stronger and more stable coupling.

Therefore, the second coupling capacitor C2 of the present invention only needs to be able to achieve the purpose of conducting the reference point E and the reference potential point F in an AC state.

Preferably, in some embodiments, in order to simplify the circuit structure, an electronic component with capacitive characteristics can be selected as the second coupling capacitor C2.

In other embodiments, in order to make full use of the existing structure in the circuit, the second coupling capacitor C2 is designed as two metal structures close to each other, so that the two metal structures close to each other form a capacitor. "Characteristics.

In a further solution, the first coupling capacitor C1 is an electronic component with capacitive characteristics, or a capacitor formed by two metal structures close to each other.

In detail, the function of the first coupling capacitor C1 is to make the two ends of the first coupling capacitor C1 form a stronger and more stable coupling.

Therefore, the first coupling capacitor C1 of the present invention only needs to be able to perform the purpose of conducting in an AC state.

Preferably, in some embodiments, in order to simplify the circuit structure, an electronic component with capacitive characteristics can be selected as the first coupling capacitor C1.

In other embodiments, in order to make full use of the existing structure in the circuit, the first coupling capacitor C1 is designed as two metal structures close to each other, so that the two metal structures close to each other form a capacitor. "Characteristics.

In a further solution, a voltage acquisition circuit is connected to both ends of the sampling resistor R1 for detecting the voltage across the sampling resistor R1.

For example, a voltmeter is connected between the two ends of the sampling resistor R1.

Or, the sampling resistor R1 itself can be set as a combination of a resistance with a large impedance and an indicator light, similar to the principle of an electric pen, when the voltage across the indicator light reaches a certain value, the indicator light will glow.

The present invention also provides a leakage protection circuit, which includes the above-mentioned leakage detection circuit 101 and the detection circuit 102.

As shown in FIG. 2, the detection circuit 102 is used in the voltage acquisition circuit to amplify and process the voltage across the sampling resistor R1. When there is a sufficiently large AC voltage across the sampling resistor R1, a display or alarm signal will be formed in the detection circuit 102.

The above-mentioned leakage detection circuit 101 obtains the voltage across the sampling resistor R1. When the voltage across the sampling resistor R1 is lower than the set threshold, no leakage occurs, and the leakage protection circuit 10 is maintained in a normal state. When the voltage across the sampling resistor R1 is greater than or equal to the set threshold, it indicates that a leakage phenomenon has occurred, and the leakage protection circuit 10 issues a warning message or directly cuts off the power supply source of the live conductor G.

It should be pointed out that the sensitivity of the leakage detection circuit 101 can be adjusted by adjusting the size of the set threshold. The sensitivity is low, and the current flowing through the human body is too large to provide leakage protection; if the sensitivity is too high, it will cause the leakage protector to malfunction due to the normal small leakage of the circuit or electrical equipment, and the power supply will be cut off, so it needs to be adjusted. To the most suitable value.

For example, when the requirements for leakage protection are high, the set threshold can be set to a smaller value, so that the sensitivity of leakage detection is higher, and the higher requirements for leakage protection can be met. When the requirements for leakage protection are slightly lower, the set threshold can be set to a relatively large value, so the sensitivity of leakage detection is relatively low, and misoperation caused by small leakage can be avoided.

As shown in FIG. 3, in one embodiment, the leakage protection circuit 10 includes a leakage detection circuit 101 and a detection circuit 102, where the detection circuit 102 includes a voltage conditioning circuit 1021, a comparison circuit 1022 and a warning circuit 1023.

The voltage conditioning circuit 1021 is connected to both ends of the sampling resistor R1 in the leakage detection circuit 101, and is used to adjust the voltage across the sampling resistor R1 and output to the comparison circuit 1022.

The voltage conditioning circuit 1021 may include one or more combinations of functions such as voltage conversion, rectification, filtering, and amplification, and convert the voltage across the sampling resistor R1 into a suitable voltage and output it to the comparison circuit 1022.

The comparison circuit 1022 is used to compare the conditioned voltage with the reference voltage in the comparison circuit 1022 and output the comparison result to the warning circuit 1023.

The warning circuit 1023 sends out warning information according to the comparison result.

In detail, since the voltage introduced on the live wire L is 220 volts AC mains, when the live conductor G leaks, and there is a transformer T, it is like connecting the AC power to the leakage detection circuit, and the coupling capacitor provides an AC channel for it. The AC voltage is generated across the sampling resistor R1. Because of its voltage amplitude, period, noise and other factors, it is usually not directly used for detection, but must be processed by a conditioning circuit and output. The function of the voltage conditioning circuit 1021 is to transform, rectify, and filter the voltage across the sampling resistor R1. , Amplification and other processing, so that the AC voltage at both ends of the resistor corresponds to a DC output voltage with a suitable amplitude. Then, the adjusted voltage is output to the comparison circuit 1022.

The comparison circuit 1022 is provided with a reference voltage, and the comparison circuit 1022 compares and outputs the output voltage of the conditioning circuit with the reference voltage, so as to realize the judgment of the voltage amplitude at both ends of the sampling resistor R1. Preferably, the reference voltage here is the set threshold. For example, when the voltage across the sampling resistor R1 is greater than the set threshold, that is, when the input voltage of the comparison circuit 1022 is greater than the reference voltage of the comparison circuit 1022, the comparison circuit 1022 outputs a high-level signal; when the voltage across the sampling resistor R1 is less than the set threshold That is, when the input voltage of the comparison circuit 1022 is less than the reference voltage of the comparison circuit 1022, the comparison circuit 1022 outputs a low level. Then, regardless of the high level or the low level, the comparison result is output to the warning circuit 1023.

The warning circuit 1023 can be a light warning, a sound warning, or a combination of the two. For example, when the warning circuit 1023 receives a high level, it controls the lights to flicker and the warning horn to sound, indicating that a leakage phenomenon has occurred at this time, and prompting the user or operator to perform the next operation to cut off the power supply to the live conductor G. When the warning circuit 1023 receives the low level, it controls the light or the whistle to keep the light off and the whistle does not sound, indicating that there is no leakage phenomenon at this time, and power can continue to be supplied to the live conductor G to make the equipment connected to the live conductor G normal operation.

As shown in FIG. 4, in another embodiment, the leakage protection circuit 10 includes a leakage detection circuit 101 and a detection circuit 102, wherein the detection circuit 102 includes a voltage conditioning circuit 1021, a comparison circuit 1022, and a switching circuit 1024. The switch circuit 1024 is used to control the conduction and disconnection of the charged conductor G and the power supply terminal.

The voltage conditioning circuit 1021 is connected to both ends of the sampling resistor R1 in the leakage detection circuit 101, and is used to convert the AC voltage across the sampling resistor R1 to a DC output voltage with a suitable amplitude, and output to the comparison circuit 1022.

In detail, the voltage conditioning circuit 1021 may include one or more combinations of functions such as voltage conversion, rectification, filtering, amplifying, etc., to convert the voltage across the sampling resistor R1 into a suitable voltage and output it to the comparison Circuit 1022.

The comparison circuit 1022 is used to compare the conditioned voltage with a reference voltage, and output the comparison result to the switch circuit 1024.

The switch circuit 1024 is disconnected or connected according to the comparison result.

In detail, since the voltage introduced on the live conductor G is 220 volts AC mains, when the live conductor G has a leakage, and there is a transformer T, as if the AC is connected to the leakage detection circuit, the coupling capacitor provides an AC channel for it , So that AC voltage is generated across the sampling resistor R1. AC voltage is usually not directly used for detection due to its voltage amplitude, period, noise and other factors, but must be processed by a conditioning circuit and output. The function of the voltage conditioning circuit 1021 is to transform and rectify the voltage across the sampling resistor R1. , Filtering, amplifying, etc., so that the AC voltage at both ends of the resistor corresponds to a DC output voltage with a suitable amplitude. Then, the adjusted voltage is output to the comparison circuit 1022.

The comparison circuit 1022 is provided with a reference voltage, and the comparison circuit 1022 compares and outputs the output voltage of the conditioning circuit with the reference voltage, so as to realize the judgment of the voltage amplitude at both ends of the sampling resistor R1. For example, when the voltage across the sampling resistor R1 is greater than the set threshold, that is, when the input voltage of the comparison circuit 1022 is greater than the reference voltage of the comparison circuit 1022, the comparison circuit 1022 outputs a high-level signal; when the voltage across the sampling resistor R1 is less than the set threshold That is, when the input voltage of the comparison circuit 1022 is less than the reference voltage of the comparison circuit 1022, the comparison circuit 1022 outputs a low level. Then, regardless of the high level or the low level, the comparison result is output to the switch circuit 1024.

For example, when the switch circuit 1024 receives a high level, it indicates that a leakage phenomenon has occurred at this time, and the switch circuit 1024 is controlled to be turned off to cut off the power supply to the live conductor G. When the switch circuit 1024 receives a low level, it means that no leakage occurs at this time. The control switch circuit 1024 is turned on and can continue to supply power to the live conductor G, so that the equipment connected to the live conductor G can operate normally.

The voltage conditioning circuit 1021, the comparison circuit 1022, the warning circuit 1023, and the switching circuit 1024 in the above solution have various implementation forms. The present invention does not limit the specific structure of the voltage conditioning circuit 1021, the warning circuit 1023 and the switching circuit 1024. Any structure capable of realizing the above-mentioned solution of the present invention falls within the protection scope of the present invention.

In the above solution, the leakage detection circuit 101 with the second coupling capacitor C2 is used to make the detection reference point E and the reference potential point F form a strong and stable coupling, so that the detection reference point E becomes a reliable reference, and the measurement is stable and reliable. There will be no leakage of electricity or false alarms.

In another embodiment, the leakage protection circuit 10 may include the above-mentioned warning circuit 1023 and the switch circuit 1024 at the same time. The specific working process is as described above and will not be repeated here.

The present invention also provides a household appliance, which includes the above-mentioned leakage detection circuit 101 and/or the leakage protection circuit 10.

In detail, the above-mentioned leakage detection circuit 101 and/or leakage protection circuit 10 can be used in a safety detection function module in a household appliance to improve the efficiency of leakage detection and improve the safety performance of the household appliance.

Further, the household appliance is a gas water heater, an electric water heater or a heat pump water heater.

In detail, the shells of gas water heaters, electric water heaters and heat pump water heaters mostly adopt metal structures. Therefore, the use of the above leakage detection circuit and/or leakage protection circuit of the present invention can greatly improve the safety performance of gas water heaters, electric water heaters and heat pump water heaters .

The above are only the preferred embodiments of the present invention and do not limit the present invention in any form. Although the present invention has been disclosed as above in preferred embodiments, it is not intended to limit the present invention. Any technology familiar with this patent Without departing from the scope of the technical solution of the present invention, the personnel can use the technical content suggested above to make slight changes or modification into equivalent embodiments with equivalent changes. However, any content that does not deviate from the technical solution of the present invention is based on the technology of the present invention. Essentially, any simple modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the solution of the present invention.

Claims (10)

1. A leakage detection circuit includes a live conductor with alternating current and a connecting end for connecting with the conductor to be measured, the connecting end is connected with a voltage detection circuit; characterized in that,

   The voltage detection circuit includes a first coupling capacitor, a sampling resistor, and a second coupling capacitor connected in sequence;

   The first coupling capacitor is connected to the conductor under test, and the second coupling capacitor is grounded.
2. The leakage detection circuit according to claim 1, wherein:

   A voltage dividing resistor is also provided between the first coupling capacitor and the sampling resistor.
3. A leakage detection circuit according to claim 1 or 2, characterized in that:

   The first coupling capacitor and/or the second coupling capacitor are electronic components with capacitive characteristics, or capacitors formed by two metal structures close to each other.
4. The leakage detection circuit according to any one of claims 1 to 3, further comprising a voltage collection circuit, connected to both ends of the sampling resistor, and used for detecting the voltage across the sampling resistor.
5. A leakage detection circuit according to any one of claims 1-3, wherein:

   The live conductor has a first state and a second state,

   When the voltage across the sampling resistor is lower than the set threshold, the live conductor is in the first state, and at this time, the live conductor does not leak;

   When the voltage across the sampling resistor is greater than or equal to the set threshold, the charged conductor is in the second state. At this time, the charged conductor is leaking.
6. A leakage protection circuit, characterized by comprising the leakage detection circuit according to any one of claims 1-5.
7. The leakage protection circuit according to claim 6, further comprising a detection circuit, the detection circuit is connected to both ends of the sampling resistor, and is used to detect whether the voltage across the sampling resistor is greater than the set voltage. Set threshold.
8. The leakage protection circuit according to claim 7, wherein the detection circuit comprises a voltage conditioning circuit, a comparison circuit, a warning circuit and/or a switch circuit; wherein

   The voltage conditioning circuit is connected to both ends of the sampling resistor, and is used to adjust the voltage at both ends of the sampling resistor and output to the comparison circuit;

   The comparison circuit is used to compare the conditioned voltage with the reference voltage of the comparison circuit, and output the comparison result to the warning circuit and/or the switch circuit;

   The warning circuit sends out warning information according to the comparison result; and/or, the switch circuit is disconnected or connected according to the comparison result.
9. A household appliance, characterized by comprising the leakage detection circuit according to any one of claims 1-5, and/or the leakage protection circuit according to any one of claims 6-8.
10. A household appliance according to claim 9, characterized in that,

    The household appliances are gas water heaters, electric water heaters or heat pump water heaters.

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