CN217741305U - Protection circuit and household electrical appliances - Google Patents

Abstract

The utility model provides a protection circuit and household electrical appliance, which comprises an electric leakage detection module, a first temperature detection module, a second temperature detection module, a first switch module, a second switch module and a third switch module; the first input end of the electric leakage detection module is connected with the first end of the alternating current power supply, the second input end of the electric leakage detection module is connected with the second end of the alternating current power supply, and the output end of the electric leakage detection module is connected with the first end of the first switch module and the third end of the second switch module; the second end of the first switch module is grounded, and the third end of the first switch module is respectively connected with the first end of the second switch module, the first end of the third switch module, the output end of the first temperature detection module and the output end of the second temperature detection module; the second end of the second switch module is connected with a first power supply end, and the third end of the second switch module is connected with the first end of the first switch module; the second end of the third switch module is connected with the first end of the alternating current power supply, the third end of the third switch module is connected with the heater, and the circuit integrates the electric leakage protection function and the over-temperature protection function, simplifies the circuit and reduces the cost.

Description

Protection circuit and household electrical appliances

Technical Field

The embodiment of the utility model provides a relate to electronic circuit technical field, in particular to protection circuit and household electrical appliances.

Background

At present, to some household electrical appliances that have the heating function, like intelligent toilet bowl etc. be provided with earth leakage protection circuit respectively usually and overtemperature prote circuit, like this, when electric leakage appears in the electrical usage on household electrical appliances, earth leakage protection circuit can the break power in order to play earth leakage protection, when dry combustion method or the inside water of container were overheated appear in household electrical appliances, overtemperature prote circuit can the break power, realizes overtemperature prote.

However, in the existing household electrical appliance, the leakage protection circuit and the over-temperature protection circuit are two independent circuit units, which are not related to each other, so that the protection circuit has a complex structure and increases the circuit cost.

SUMMERY OF THE UTILITY MODEL

The embodiment of the utility model provides a protection circuit and household electrical appliances are mainly provided, this protection circuit collection earth leakage protection function and excess temperature protect function can simplify circuit structure, reduce circuit cost.

The utility model discloses a technical scheme that embodiment adopted is: there is provided a protection circuit for a heating apparatus including a heater and a container, the protection circuit including: the temperature detection module comprises a leakage detection module, a first temperature detection module, a second temperature detection module, a first switch module, a second switch module and a third switch module; the first input end of the leakage detection module is used for being connected with the first end of an alternating current power supply, the second input end of the leakage detection module is used for being connected with the second end of the alternating current power supply, the output end of the leakage detection module is connected with the first end of the first switch module, and the leakage detection module is used for outputting a first level signal to the first switch module according to the current difference between the first end and the second end of the alternating current power supply; the second end of the first switch module is grounded, the third end of the first switch module is respectively connected with the first end of the second switch module, the first end of the third switch module, the output end of the first temperature detection module and the output end of the second temperature detection module, and the first switch module is used for being conducted according to the first level signal and outputting a second level signal to the first end of the second switch module and the first end of the third switch module; the first temperature detection module is used for outputting a second level signal to the first end of the third switch module when the water temperature in the container exceeds a first temperature; the second temperature detection module is used for outputting a second level signal to the first end of the third switch module and the first end of the second switch module when the temperature of the container exceeds a second temperature; the second terminal of the second switch module is used for connecting a first power supply terminal, the third terminal of the second switch module is connected to the first terminal of the first switch module, and the second switch module is used for conducting according to the second level signal, so that the first power supply terminal outputs a first level signal to the first terminal of the first switch module through the second switch module, and the first switch module is conducted; the second end of the third switch module is used for being connected with the first end of the alternating current power supply, the third end of the third switch module is used for being connected with the heater, and the third switch module is used for disconnecting the alternating current power supply from the heater according to the second level signal.

In some embodiments, the protection circuit further comprises a first resistor; the first end of the first resistor is used for being connected with the first power supply end, and the second end of the first resistor is connected with the first end of the third switch module.

In some embodiments, the protection circuit further comprises a first diode pair comprising a first diode and a second diode; the cathode of the first diode is connected with the output end of the first temperature detection module, the cathode of the second diode is respectively connected with the output end of the second temperature detection module, the third end of the first switch module and the first end of the second switch module, and the anode of the first diode and the anode of the second diode are both connected with the first end of the third switch module.

In some embodiments, the protection circuit further comprises a voltage divider module; the first end of the voltage division module is used for being connected with the first power end, the second end of the voltage division module is connected with the second end of the second switch module, and the third end of the voltage division module is respectively connected with the cathode of the second diode, the third end of the first switch module and the output end of the first temperature detection module.

In some embodiments, the first switching module comprises a first switching tube; the first end of the first switch tube is connected with the output end of the electric leakage detection module and the third end of the second switch module respectively, the second end of the first switch tube is grounded, and the third end of the first switch tube is connected with the output end of the second temperature detection module, the first end of the second switch module and the first end of the third switch module respectively.

In some embodiments, the second switching module comprises a second switching tube; the first end of the second switch tube is connected with the third end of the first switch module, the output end of the second temperature detection module and the first end of the third switch module respectively, the second end of the second switch tube is used for being connected with the first power supply end, and the third end of the second switch tube is connected with the first end of the first switch module and the output end of the electric leakage detection module respectively.

In some embodiments, the third switching module comprises a third switching tube and a relay; the first end of the third switch tube is respectively connected with the output end of the first temperature detection module, the output end of the second temperature detection module, the third end of the first switch module and the first end of the second switch module, the second end of the third switch tube is grounded, the third end of the third switch tube is connected with the first end of the relay, the second end of the relay is used for being connected with the first power supply end, the third end of the relay is used for being connected with the first end of the alternating current power supply, and the fourth end of the relay is used for being connected with the heater.

In some embodiments, the leakage detection module comprises a current transformer, an anti-aliasing unit and a leakage detection chip; the current transformer is buckled at the first end of the alternating current power supply and the second end of the alternating current power supply respectively, the output end of the current transformer is connected with the input end of the anti-aliasing unit, the output end of the anti-aliasing unit is connected with the input end of the electric leakage detection chip, and the output end of the electric leakage detection chip is connected with the first end of the first switch module.

In some embodiments, the first temperature detection module comprises a first temperature detection unit, a first voltage division unit, a first comparator and a fourth switch tube; the output end of the first temperature detection unit is connected with the first input end of the first comparator, the output end of the first voltage division unit is connected with the second input end of the first comparator, the output end of the first comparator is connected with the first end of the fourth switch tube, the second end of the fourth switch tube is grounded, and the third end of the fourth switch tube is connected with the first end of the third switch module.

In some embodiments, the second temperature detection module includes a second temperature detection unit, a second voltage division unit, and a second comparator; the output end of the second voltage division unit is connected with the first input end of the second comparator, the output end of the second temperature detection unit is connected with the second input end of the second comparator, and the output end of the second comparator is respectively connected with the third end of the first switch module, the first end of the second switch module and the first end of the third switch module.

In some embodiments, the protection circuit further comprises a control module; the control module is connected with the first end of the third switch module.

In a second aspect, an embodiment of the present invention further provides a household electrical appliance, which includes a heating device and the protection circuit according to any one of the first aspect; the heating device comprises a heater and a container, wherein the heater is used for heating water in the container.

The utility model discloses embodiment's beneficial effect is: different from the prior art, the embodiment of the utility model provides a protection circuit and household electrical appliance, including electric leakage detection module, first temperature detection module, second temperature detection module, first switch module, second switch module and third switch module; the first input end of the electric leakage detection module is connected with the first end of the alternating current power supply, the second input end of the electric leakage detection module is connected with the second end of the alternating current power supply, and the output end of the electric leakage detection module is connected with the first end of the first switch module and the third end of the second switch module; the second end of the first switch module is grounded, and the third end of the first switch module is respectively connected with the first end of the second switch module, the first end of the third switch module, the output end of the first temperature detection module and the output end of the second temperature detection module; the second end of the second switch module is connected with a first power supply end, and the third end of the second switch module is connected with the first end of the first switch module; the second end of the third switch module is connected with the first end of the alternating current power supply, and the third end of the third switch module is connected with the heater. In the circuit, when electric leakage occurs, the electric leakage detection module outputs a first level signal to the first switch module to enable the first switch module to be conducted, so that the third switch module is disconnected between the alternating current power supply and the heater to realize electric leakage protection, when the temperature of water in the container exceeds a first temperature, the first temperature detection module outputs a second level signal to the third switch module to enable the third switch module to be disconnected between the alternating current power supply and the heater, or when the temperature of the container exceeds a second temperature, the second temperature detection module outputs a second level signal to the third switch module to also enable the third switch module to be disconnected between the alternating current power supply and the heater to realize over-temperature protection. Therefore, the protection circuit integrates the leakage protection function and the over-temperature protection function, simplifies the circuit structure and reduces the circuit cost.

Drawings

One or more embodiments are illustrated by the accompanying figures in the drawings that correspond thereto and are not to be construed as limiting the embodiments, wherein elements/modules and steps having the same reference numerals are represented by like elements/modules and steps, unless otherwise specified, and the drawings are not to scale.

Fig. 1 is a block diagram of a protection circuit according to an embodiment of the present invention;

fig. 2 is a schematic circuit diagram of a protection circuit according to an embodiment of the present invention.

Detailed Description

The present invention will be described in detail with reference to specific embodiments. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that various changes and modifications can be made by one skilled in the art without departing from the spirit of the invention. These all belong to the protection scope of the present invention.

In order to facilitate an understanding of the present application, the present application is described in more detail below with reference to the accompanying drawings and specific embodiments. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It should be noted that, if not conflicting, various features of the embodiments of the present invention may be combined with each other and all are within the scope of protection of the present application. In addition, although the functional blocks are divided in the device diagram, in some cases, the blocks may be divided differently from those in the device. Further, the terms "first," "second," and the like, as used herein, do not limit the data and the execution order, but merely distinguish the same items or similar items having substantially the same functions and actions.

In a first aspect, an embodiment of the present invention provides a protection circuit, which is applied to a heating device, where the heating device includes a heater and a container, and referring to fig. 1, the protection circuit 100 includes: the leakage detection module 10, the first temperature detection module 20, the second temperature detection module 30, the first switch module 40, the second switch module 50, and the third switch module 60.

The first input end of the leakage detection module 10 is used for connecting the first end of the ac power supply 200, the second input end of the leakage detection module 10 is used for connecting the second end of the ac power supply 200, the output end of the leakage detection module 10 is connected to the first end of the first switch module 40, and the leakage detection module 10 is used for outputting a first level signal to the first switch module 40 according to the current difference between the first end and the second end of the ac power supply 200.

A second end of the first switch module 40 is grounded to GND, a third end of the first switch module 40 is connected to a first end of the second switch module 50, a first end of the third switch module 60, an output end of the first temperature detection module 20, and an output end of the second temperature detection module 30, respectively, and the first switch module 40 is configured to be turned on according to the first level signal and output a second level signal to the first end of the second switch module 50 and the first end of the third switch module 60; the first temperature detecting module 20 is configured to output a second level signal to the first end of the third switching module 60 when the temperature of the water in the container exceeds a first temperature; the second temperature detecting module 30 is configured to output a second level signal to the first terminal of the third switching module 60 and the first terminal of the second switching module 50 when the temperature of the container exceeds a second temperature.

The second terminal of the second switch module 50 is used for connecting the first power terminal VCC, the third terminal of the second switch module 50 is connected to the first terminal of the first switch module 40, and the second switch module 50 is used for conducting according to the second level signal, so that the first power terminal VCC outputs the first level signal to the first terminal of the first switch module 40 through the second switch module 50, thereby conducting the first switch module 40.

The second terminal of the third switching module 60 is used for connecting the first terminal of the ac power supply 200, the third terminal of the third switching module 60 is used for connecting the heater 300, and the third switching module 60 is used for disconnecting the ac power supply 200 from the heater 300 according to the second level signal.

The first end of the ac power source 200 may be a live line, the second end of the ac power source 200 may be a neutral line, and the first end and the second end of the ac power source 200 may be set according to actual needs, which is not limited herein. The first level signal may be a high level signal, and the second level signal may be a low level signal.

In the protection circuit, on one hand, when leakage occurs after the household electrical appliance is powered on, the current difference between the live line and the zero line is not 0, and at this time, the leakage detection module 10 outputs a first level signal to the first switch module 40 according to the current difference between the live line and the zero line; then, the first switch module 40 is turned on according to the first level signal, so that the first end of the second switch module 50 and the first end of the third switch module 60 are both grounded to GND. At this time, after the first end of the third switching module 60 is grounded GND, that is, receives the second level signal, the third switching module 60 is turned off, so that the connection between the first end of the ac power supply 200 and the heater 300 is disconnected, the heater 300 cannot be powered, and stops working, thereby implementing leakage protection. At this time, the first end of the second switch module 50 is grounded GND, that is, the second switch module 50 receives the second level signal, the second switch module 50 is turned on, and the first power source terminal VCC outputs the first level signal to the first switch module 40 through the second switch module 50, so that the first switch module 40 is continuously turned on, the second switch module 50 and the third switch module 60 continuously receive the second level signal, the second switch module 50 is continuously turned on, and the third switch module 60 is continuously turned off, thereby maintaining self-locking and improving reliability of the leakage protection function.

On the other hand, if the water temperature in the container of the heating device is too high, such as exceeding the first temperature, at this time, the first temperature detecting module 20 outputs a second level signal to the first end of the third switching module 60, and the third switching module 60 disconnects the connection between the ac power supply 200 and the heater 300 after receiving the second level signal, so as to prevent the user from being scalded by the too high water temperature; if the temperature of the container is too high, for example, exceeds the second temperature, at this time, the second temperature detection module 30 outputs a second level signal to the first end of the third switching module 60, and the third switching module 60 disconnects the connection between the ac power supply 200 and the heater 300 after receiving the second level signal, thereby avoiding dry burning and realizing an over-temperature protection function.

If no electric leakage occurs after the household electrical appliance is powered on, the water temperature in the container of the heating device does not exceed the first temperature, and the temperature of the container does not exceed the second temperature, the electric leakage detection module 10 outputs a second level signal to the first switch module 40, the first temperature detection module 20 outputs a first level signal to the first end of the third switch module 60, and the second temperature detection module 30 outputs a first level signal to the first end of the third switch module 60, so that the protection circuit does not trigger the protection action.

In summary, in this circuit, when the ac power supply 200 leaks, the connection between the ac power supply 200 and the heater 300 can be disconnected, and the leakage protection function is performed; when the water temperature exceeds the first temperature and/or the temperature of the container exceeds the second temperature, the connection between the alternating current power supply 200 and the heater 300 can be disconnected, and the over-temperature protection function is realized. Therefore, the protection circuit combines the leakage protection circuit and the over-temperature protection circuit into a whole, thereby simplifying the circuit structure and reducing the circuit cost; in addition, when one of the first switch module 40 and the second switch module 50 is turned on, the other switch module is also turned on, so that the two switch modules are continuously turned on, and the first end of the third switch module 60 is continuously grounded GND, thereby improving the safety and reliability of the protection circuit 100 during operation.

In some embodiments, referring to fig. 2, the protection circuit further includes a first resistor R1; a first terminal of the first resistor R1 is connected to the first power terminal VCC, and a second terminal of the first resistor R1 is connected to a first terminal of the third switching module 60. By arranging the first resistor R1, when no leakage or over-temperature occurs, the first power source terminal VCC may output a first level signal to the first terminal of the third switching module 60 through the first resistor R1, so that the third switching module 60 may conduct the connection between the ac power supply 200 and the heater 300 according to the first level signal, so that the heater 300 may normally operate.

In some embodiments, referring to fig. 2, the protection circuit further includes a first diode D1, the first diode D1 includes a first diode D1 and a second diode D2; the cathode of the first diode d1 is connected to the output end of the first temperature detecting module 20, the cathode of the second diode d2 is connected to the output end of the second temperature detecting module 30, the third end of the first switch module 40 and the first end of the second switch module 50, respectively, and the anode of the first diode d1 and the anode of the second diode d2 are both connected to the first end of the third switch module 60. In the protection circuit, the first diode D1 is used as an isolation module, so that the first temperature detection module 20, the second temperature detection module 30, the first switch module 40 and the second switch module 50 can be electrically isolated from the first power supply terminal VCC, and the reliability of the protection circuit is improved.

In some embodiments, referring to fig. 2, the protection circuit further includes a voltage divider module 70; a first end of the voltage divider module 70 is used for connecting to the first power supply terminal VCC, a second end of the voltage divider module 70 is connected to a second end of the second switch module 50, and a third end of the voltage divider module 70 is respectively connected to a cathode of the second diode d2, a third end of the first switch module 40, and an output end of the second temperature detection module 30. Specifically, please refer to fig. 2, the voltage divider module 70 includes a resistor R2 and a resistor R3, a first end of the resistor R2 is used for connecting to the first power source VCC, a second end of the resistor R2 is respectively connected to a first end of the resistor R3 and a second end of the second switch module 50, and a second end of the resistor R3 is respectively connected to a cathode of the second diode d2, a third end of the first switch module 40, and an output end of the second temperature detecting module 30.

By providing the voltage dividing module 70, on one hand, when the circuit does not generate leakage or over-temperature, the first power source terminal VCC may output the first level signal to the first terminal of the third switching module 60 through the voltage dividing module 70, so that the third switching module 60 may conduct the connection between the ac power supply 200 and the heater 300 according to the first level signal, so as to enable the heater 300 to normally operate. On the other hand, when the second switch module 50 is turned on, the voltage of the first end of the first switch module 40 outputted by the first power terminal VCC is prevented from being too large by the voltage division between the resistor R2 and the resistor R3, wherein the resistor R2 can also achieve the function of limiting the current. In addition, in the protection circuit, when the signal at the first end of the second switch module 50 is unstable, the first power end VCC outputs a high level signal to the first end of the second switch module 50 through the resistor R2 and the resistor R3, so as to prevent the second switch module 50 from being turned on by mistake, thereby preventing the third switch module 60 from being turned off by mistake, and improving the reliability of the operation of the protection circuit. In practical applications, the number and the resistance of the resistors of the voltage dividing module 70 may be set according to actual needs, and are not limited herein.

In some embodiments, referring to fig. 2, the voltage dividing module 70 further includes a capacitor C1, where the capacitor C1 is connected in parallel with the resistor R3, and by setting the capacitor C1, signals can be filtered, so as to improve the anti-interference capability of the circuit.

In some embodiments, referring to fig. 2, the first switch module 40 includes a first switch Q1; the first end of the first switch tube Q1 is connected to the output end of the leakage detecting module 10 and the third end of the second switch module 50, respectively, the second end of the first switch tube Q1 is grounded GND, and the third end of the first switch tube Q1 is connected to the output end of the second temperature detecting module 30, the first end of the second switch module 50 and the first end of the third switch module 60, respectively.

Specifically, referring to fig. 2, the first switch Q1 is a first NPN transistor, a base of the first NPN transistor is connected to the output end of the leakage detecting module 10 and the third end of the second switch module 50, respectively, an emitter of the first NPN transistor is grounded to GND, and a collector of the first NPN transistor is connected to the output end of the second temperature detecting module 30, the first end of the second switch module 50, and the cathode of the second diode d2, respectively. In this way, when the leakage occurs, the leakage detecting module 10 outputs a high level signal to the first NPN transistor, and the first NPN transistor is turned on to ground the first end of the second switch module 50 and the cathode of the second diode d2 to GND, so that the second switch module 50 is turned on, and the first end of the third switch module 60 is also at a low level due to the action of the second diode d2, and at this time, the third switch module 60 is turned off. When no leakage occurs, the leakage detection module 10 outputs a low level signal to the base of the first NPN transistor, and the first NPN transistor is turned off without triggering a protection action. In practical applications, the first switch Q1 may also be a MOS transistor, a relay, or any other suitable switching device.

In some embodiments, referring to fig. 2, the second switch module 50 further includes a resistor R4, a first end of the resistor R4 is connected to the base of the first NPN transistor and the third end of the second switch module 50, and a second end of the resistor R4 is connected to the output end of the leakage detecting module 10. By arranging the resistor R4, the magnitude of a base signal output to the first NPN triode by the electric leakage detection module 10 can be limited, so that the first NPN triode is protected, and the safety of the protection circuit is improved.

In some embodiments, referring to fig. 2, the second switch module 50 further includes a resistor R5, a first end of the resistor R5 is connected to the base of the first NPN transistor, the third end of the second switch module 50, and the first end of the resistor R4, respectively, and a second end of the resistor R5 is grounded GND. Through setting up resistance R5, can prevent that first NPN triode from receiving the influence of noise signal and producing the malfunction, make the NPN triode cut off more reliably, for example when the base signal of first NPN triode is uncertain, through this resistance R5, can let the base of first NPN triode effectively ground connection GND, make first NPN triode break off to prevent the circuit misconnection, improve the reliability of protection circuit.

In some embodiments, referring to fig. 2, the second switch module 50 includes a second switch Q2; the first end of the second switch tube Q2 is connected to the third end of the first switch module 40, the output end of the second temperature detection module 30 and the first end of the third switch module 60, respectively, the second end of the second switch tube Q2 is used for connecting the first power end VCC, and the third end of the second switch tube Q2 is connected to the first end of the first switch module 40 and the output end of the leakage detection module 10, respectively.

Specifically, referring to fig. 2, the second switching tube Q2 is a PNP triode, a base of the PNP triode is connected to a collector of the first NPN triode, an output end of the second temperature detection module 30, and a cathode of the second diode d2, a second end of the PNP triode is connected to a first end of the resistor R2, and a third end of the PNP triode is connected to a base of the first NPN triode and an output end of the leakage detection module 10. In the protection circuit, when the second temperature detection module 30 outputs a low level signal and/or outputs a low level signal to the PNP triode when the first NPN triode is turned on, the PNP triode is turned on, and the first power supply terminal VCC outputs a high level signal to the first NPN triode through the resistor R2, so that the first NPN triode is turned on, and the first NPN triode and the PNP triode are maintained in self-locking conduction. When the second temperature detecting module 30 does not output the low level signal to the PNP transistor and the first NPN transistor is turned off, the first power terminal VCC outputs the high level signal to the PNP transistor through the resistor R2 and the resistor R3, so that the PNP transistor is turned off. In practical applications, the second switch Q2 may also be a MOS transistor, a relay, or any other suitable switch device.

In some embodiments, referring to fig. 2, the third switch module 60 includes a third switch Q3 and a relay RLY. The first end of the third switching tube Q3 is connected to the output end of the first temperature detection module 20, the output end of the second temperature detection module 30, the third end of the first switching module 40 and the first end of the second switching module 50, the second end of the third switching tube Q3 is grounded GND, the third end of the third switching tube Q3 is connected to the first end of the relay RLY, the second end of the relay RLY is used for connecting the first VCC, the third end of the relay RLY is used for connecting the first end of the ac power supply, and the fourth end of the relay RLY is used for connecting the heater.

Specifically, referring to fig. 2, the third switching tube Q3 is a second NPN transistor, a base of the second NPN transistor is connected to an anode of the first diode d1, an anode of the second diode d2, and a second end of the resistor R1, respectively, an emitter of the second NPN transistor is grounded GND, and a collector of the second NPN transistor is connected to the first end of the relay RLY. And in the embodiment shown in fig. 2, ACL1 represents a power supply input side which is normally connected to a first end of an ac power supply, and ACL2 represents a power supply output side which is connected to a heater. In the protection circuit, when no leakage occurs and no over-temperature condition occurs, the first power supply terminal VCC outputs a high level signal to the base of the second NPN transistor through the first resistor R1, the second NPN transistor is turned on, the second end of the relay RLY is grounded to GND, the relay RLY operates to establish connection between the third end of the relay RLY and the fourth end of the relay RLY, so that the heater 300 is powered by the ac power supply 200. When electric leakage occurs, the first switch module 40 is turned on, so that the anode of the second diode d2 is a low level signal, that is, the base of the second NPN triode is a low level signal, the second NPN triode is turned off, and the relay RLY does not work, thereby disconnecting the connection between the third terminal of the relay RLY and the fourth terminal of the relay RLY, so that the heater 300 cannot be powered by the ac power supply 200, and the heater 300 stops working, thereby realizing electric leakage protection. Or, when the first temperature detecting module 20 detects that the water temperature is over-temperature, the first temperature detecting module outputs a low level signal to the cathode of the first diode d1, and similarly, the base of the second NPN transistor is a low level signal, the second NPN transistor is turned off, and the relay RLY does not work, so that the heater 300 cannot be supplied with power from the ac power supply 200, and the heater 300 stops working, thereby implementing over-temperature protection. Or, when the second temperature detecting module 30 detects the container over-temperature, it outputs a low level signal to the cathode of the second diode d2, and in the same way, the heater 300 may finally stop working, thereby implementing the over-temperature protection.

In summary, by providing the third switching tube Q3 and the relay RLY, when a current leakage or an excessive temperature occurs in the circuit, the connection between the ac power supply 200 and the heater 300 can be cut off, and the heater 300 can be stopped. In practical applications, the switching devices and the number inside the third switching module 60 may be set according to actual needs, and may include at least one switching device of a triode, a MOS transistor, and a relay.

In some embodiments, referring to fig. 2, the third switching module 60 further includes a resistor R6, a first end of the resistor R6 is connected to the second end of the first resistor R1, the anode of the first diode d1, and the anode of the second diode d2, respectively, and a second end of the resistor R6 is connected to the base of the second NPN transistor. By arranging the resistor R6, the current input to the base electrode of the second NPN triode can be limited, so that the second NPN triode is protected, and the safety and the reliability of the protection circuit are improved.

In some embodiments, referring to fig. 2, the third switching module 60 further includes a resistor R7, a first end of the resistor R7 is connected to the base of the second NPN transistor and a second end of the resistor R6, respectively, and a second end of the resistor R7 is grounded to GND. By arranging the resistor R7, the second NPN triode can be prevented from generating misoperation under the influence of a noise signal, so that the cut-off of the NPN triode is more reliable, for example, when a base signal of the second NPN triode is uncertain, the base of the second NPN triode can be effectively grounded GND through the resistor R7, so that the second NPN triode is cut off, the circuit is prevented from being conducted by mistake, and the reliability of the protection circuit is improved.

In some embodiments, referring to fig. 2, the leakage detecting module 10 includes a current transformer T1, an anti-aliasing unit 11, and a leakage detecting chip U1. The current transformer T1 is respectively buckled at the first end of the alternating current power supply 200 and the second end of the alternating current power supply 200, the output end of the current transformer T1 is connected with the input end of the anti-aliasing unit 11, the output end of the anti-aliasing unit 11 is connected with the input end of the electric leakage detection chip U1, and the output end of the electric leakage detection chip U1 is connected with the first end of the first switch module 40.

Referring to fig. 2, the anti-aliasing unit 11 includes a resistor R8, a resistor R9, a resistor R10, a third diode pair D3, a capacitor C2, a capacitor C3, and a capacitor C4, the third diode pair D3 includes a diode D3 and a diode D4, and the leakage detection chip U1 may adopt leakage detection chips such as XM2147 and D54123. Specifically, the current transformer T1 may be connected to the live wire and the zero line through the interface CN3, so that the live wire and the zero line pass through the coil, one end of the coil of the current transformer T1 is connected to the first end of the resistor R8, the first end of the resistor R9, the cathode of the diode d3, and the anode of the diode d4, the other end of the coil of the current transformer T1 is connected to the second end of the resistor R8, the anode of the diode d3, the cathode of the diode d4, and the first end of the resistor R10, the second end of the resistor R9 is connected to the first end of the capacitor C2, the first end of the capacitor C3, and the first input end of the leakage detection chip U1, the second end of the resistor R10 is connected to the second end of the capacitor C2, the first end of the capacitor C4, and the second input end of the leakage detection chip U1, both the second end of the capacitor C3 and the second end of the capacitor C4 are grounded, and the output end of the leakage detection chip U1 is connected to the base of the NPN transistor.

In the protection circuit, when a current difference exists between a live wire and a zero line, due to an electromagnetic induction phenomenon, a coil of the current transformer T1 generates a current, the current flows through the resistor R8, a voltage difference is generated at two ends of the resistor R8, and the voltage difference is transmitted to the electric leakage detection chip U1 after being filtered. When the leakage phenomenon exists, and the current difference between the live line and the zero line is overlarge, the voltage difference between two ends of the resistor R8 exceeds the comparison threshold, and the leakage detection chip U1 outputs a high-level signal to the first NPN triode. When the leakage does not exist, and the voltage difference does not exceed the comparison threshold, that is, the leakage detection chip U1 outputs a low level signal to the first NPN triode. In practical applications, the leakage detecting module 10 can refer to any suitable leakage detecting circuit in the prior art, and is not limited to the limitation in this embodiment.

In some embodiments, referring to fig. 2, the first temperature detecting module 20 includes a first temperature detecting unit 21, a first voltage dividing unit 22, a first comparator U2, and a fourth switch Q4. The output end of the first temperature detection unit 21 is connected to the first input end of the first comparator U2, the output end of the first voltage division unit 22 is connected to the second input end of the first comparator U2, the output end of the first comparator U2 is connected to the first end of the fourth switch tube Q4, the second end of the fourth switch tube Q4 is grounded GND, and the third end of the fourth switch tube Q4 is connected to the first end of the third switch module 60. In the embodiment shown in fig. 2, the first input terminal of the first comparator U2 is the inverting input terminal of the first comparator U2, and the second input terminal of the first comparator U2 is the non-inverting input terminal of the first comparator U2. In the protection circuit, the first temperature detection unit 21 is used for detecting the water temperature in the container and outputting a corresponding first voltage signal to the first comparator U2. The first voltage dividing unit 22 is configured to output a first reference voltage signal to the first comparator U2. The first comparator U2 is configured to output a high level signal to the fourth switching tube Q4 when the water temperature is greater than or equal to the first temperature, that is, the first voltage signal is less than or equal to the first reference voltage signal, and output a low level signal to the fourth switching tube Q4 when the water temperature is less than the first temperature, that is, the first voltage signal is greater than the first reference voltage signal. The fourth switching tube Q4 is configured to be turned on according to the high level signal, output a low level signal to the third switching module 60, and be turned off according to the low level signal.

Optionally, referring to fig. 2, the first Temperature detecting unit 21 includes an interface CN1, a resistor R12, a resistor R13, and a capacitor C8, wherein a first end of the interface CN1 is configured to connect to a first Negative Temperature Coefficient (NTC) thermistor, a second end of the interface CN1 is configured to connect to a second end of the first NTC thermistor, a first end of the resistor R12 is connected to a first power source VCC, a second end of the resistor R12 is respectively connected to the first end of the interface CN1, the first end of the capacitor C8, and the first end of the resistor R13, the second end of the interface CN1 and the second end of the capacitor C8 are both grounded to GND, and a second end of the resistor R13 is connected to an inverted input end of the first comparator U2. The first NTC thermistor serves to detect the temperature of water in the container, and the resistance value is smaller as the temperature of water is higher, so that the first voltage signal output from the first temperature detecting unit 21 to the first comparator U2 is smaller. In the protection circuit, the capacitor C8 can filter the first voltage signal, so that the anti-interference capability of the circuit is improved, and the resistor R13 can be used for outputting the current to the first comparator U2 from the first temperature detection unit 21, so that the first comparator U2 is protected, and the safety and reliability of the circuit operation are improved.

Optionally, referring to fig. 2, the first voltage dividing unit 22 includes a resistor R14 and a resistor R15, a first end of the resistor R14 is used for connecting to the first power terminal VCC, a second end of the resistor R14 is respectively connected to the first end of the resistor R15 and the non-inverting input terminal of the first comparator U2, and a second end of the resistor R15 is grounded GND. By selecting the type of the resistor R14 and the resistor R15, the first voltage dividing unit 22 can output a first reference voltage signal corresponding to a first temperature.

Optionally, referring to fig. 2, the fourth switching tube Q4 may be a third NPN transistor, a base of the third NPN transistor is connected to the output end of the first comparator U2, a collector of the third NPN transistor is connected to the cathode of the first diode d1, and an emitter of the third NPN transistor is grounded to GND, where in the protection circuit, when the first comparator U2 outputs a high-level signal, the third NPN transistor is turned on and outputs a low-level signal to the third switching module 60; when the first comparator U2 outputs a low level signal, the third NPN transistor is turned off.

In practical applications, the internal circuit structure of the first temperature detecting module 20 may be any suitable temperature detecting circuit in the prior art, and is not limited to the limitation in this embodiment.

In some embodiments, the first temperature detection module 20 further includes a resistor R16, a first end of the resistor R16 is connected to a second end of the resistor R14 and a first end of the resistor R15, respectively, a second end of the resistor R16 is connected to a non-inverting input end of the first comparator U2, and by setting the resistor R16, the magnitude of the current output by the first voltage dividing unit 22 to the first comparator U2 can be limited, so as to protect the first comparator U2.

In some embodiments, the first temperature detecting module 20 further includes a resistor R17, the resistor R17 is connected between the non-inverting input terminal of the first comparator U2 and the output terminal of the first comparator U2, and by setting the resistor R17, the first comparator U2 can form a hysteresis comparator, so that when the water temperature decreases from high, the voltage value output to the first comparator U2 by the second voltage dividing unit can be increased, and when the first comparator U2 switches from high level to low level, since the voltage value of the first reference voltage signal output by the first voltage dividing unit 22 becomes high, the corresponding switching temperature should be lower than the first temperature. The switching value of the first comparator U2 can be changed in the above way, and the protection circuit is prevented from jittering at the switching point.

In some embodiments, the first temperature detection module 20 further includes a resistor R19 and a resistor R20. The output end of the first comparator U2 is connected to the first end of the resistor R19, the second end of the resistor R19 is connected to the first end of the resistor R20 and the base of the third NPN transistor, respectively, and the second end of the resistor R20 is grounded GND. The resistor R19 can be used for limiting the current output from the first comparator U2 to the third NPN triode and protecting the third NPN triode; the resistor R20 can effectively ground the base electrode of the first NPN triode to GND and disconnect the third NPN triode, so that the circuit is prevented from being conducted by mistake, and the reliability of the protection circuit is improved.

In some embodiments, the second temperature detection module 30 includes a second temperature detection unit 31, a second voltage division unit 32, and a second comparator U3. The output end of the second voltage division unit 32 is connected to the first input end of the second comparator U3, the output end of the second temperature detection unit 31 is connected to the second input end of the second comparator U3, and the output end of the second comparator U3 is respectively connected to the third end of the first switch module 40, the first end of the second switch module 50, and the first end of the third switch module 60. In the embodiment shown in fig. 2, the first input terminal of the second comparator U3 is an inverting input terminal of the second comparator U3, the second input terminal of the second comparator U3 is a non-inverting input terminal of the second comparator U3, and the output terminal of the second comparator U3 is connected to the cathode of the second diode d2, the collector of the first NPN transistor, and the base of the PNP transistor, respectively. In the protection circuit, the second temperature detection unit 31 is configured to detect a temperature of the container and output a corresponding second voltage signal to the second comparator U3. The second voltage dividing unit 32 is configured to output a second reference voltage signal to the second comparator U3. The second comparator U3 is configured to output a low level signal to the third switch module 60 when the temperature of the tank is greater than or equal to the second temperature, that is, the second voltage signal is less than or equal to the second reference voltage signal, and output a high level signal when the temperature of the water is less than the first temperature, that is, the first voltage signal is greater than the first reference voltage signal.

Optionally, referring to fig. 2, the first Temperature detecting unit 21 includes an interface CN2, a resistor R21, a resistor R22, and a capacitor C9, wherein a first end of the interface CN2 is configured to connect to a second Negative Temperature Coefficient (NTC) thermistor, a second end of the interface CN2 is configured to connect to a second end of the second NTC thermistor, the first end of the resistor R21 is connected to a first power source VCC, a second end of the resistor R21 is respectively connected to the first end of the interface CN2, the first end of the capacitor C9, and the first end of the resistor R22, the second end of the interface CN2 and the second end of the capacitor C9 are both grounded to GND, and the second end of the resistor R22 is connected to the non-inverting input end of the second comparator U3. The second NTC thermistor is used to detect the temperature of the container, and the resistance value is smaller as the temperature is higher, so that the voltage of the second voltage output to the second comparator U3 by the second temperature detecting unit 31 is smaller. In the protection circuit, the capacitor C9 can filter the second voltage signal, so that the anti-interference capability of the circuit is improved, and the resistor R22 can be used for outputting the current to the first comparator U2 from the second temperature detection unit 31, so that the second comparator U3 is protected, and the safety and reliability of the circuit operation are improved.

Optionally, referring to fig. 2, the first voltage dividing unit 22 includes a resistor R23 and a resistor R24, a first end of the resistor R23 is used for connecting to the first power terminal VCC, a second end of the resistor R23 is respectively connected to a first end of the resistor R24 and an inverting input terminal of the second comparator U3, and a second end of the resistor R24 is grounded GND. By selecting the type of the resistor R23 and the resistor R24, the second voltage dividing unit 32 can output a second reference voltage signal corresponding to a second temperature.

In some embodiments, the first voltage dividing unit 22 further includes a capacitor C10, the capacitor C10 is connected between the inverting input terminal of the second comparator U3 and the ground GND, and the capacitor C10 is provided to filter the second reference voltage signal, so as to improve the anti-interference capability of the circuit.

In some embodiments, the second temperature detecting module 30 further includes a resistor R25, a first end of the resistor R25 is connected to the first power supply terminal VCC, a second end of the resistor R25 is respectively connected to the output terminal of the second comparator U3, the cathode of the second diode d2, the collector of the first NPN transistor, and the base of the PNP transistor, and by setting the resistor R25, when the output signal of the second comparator U3 is unstable, the high-level output of the second temperature detecting module 30 can be ensured, thereby avoiding the false turn-off phenomenon of the circuit, and improving the reliability of the circuit.

In some embodiments, the second temperature detecting module 30 further includes a resistor R26, a first end of the resistor R26 is connected to the output end of the second comparator U3 and a second end of the resistor R25, a second end of the resistor R26 is connected to the cathode of the second diode d2, the collector of the first NPN transistor, and the base of the PNP transistor, and by setting the resistor R26, the current output by the second temperature detecting module 30 can be limited, so as to protect the circuit.

In some embodiments, referring to fig. 2, the protection circuit further includes a control module 80; the control module 80 is connected to a first end of the third switch module 60. Specifically, the control module 80 is connected to the cathode of the second diode d2, the collector of the first NPN transistor, and the base of the PNP transistor, and by setting the control module 80, a high level signal or a low level signal can be output to the third switch module 60 through the control module 80, so that the third switch module 60 is controlled by software, and the application scenario of the protection circuit is further improved. The control module can adopt series of micro-processing controllers such as STM8, STM16 and the like.

The working process of the protection circuit provided by the embodiment of the present invention is described in detail below with reference to the embodiment shown in fig. 2.

In the protection circuit, when leakage occurs after the household electrical equipment is powered on and the current difference between the live wire and the zero wire is not 0, the leakage detection chip U1 outputs a high-level signal to a first NPN triode in the first switch module 40; then, the first NPN transistor is turned on, so that the cathode of the second diode d2 and the base of the PNP transistor in the second switch module 50 are both grounded to GND. At this time, the base of the second NPN transistor in the third switching module 60 receives the low level signal, and the second NPN transistor is turned off, so that the connection between the first end of the ac power supply and the heater is disconnected, and the heater is not powered, stops working, and implements leakage protection. And because the PNP triode is grounded GND, the PNP triode is conducted, the first power supply end VCC outputs a high-level signal to the first NPN triode through the PNP triode, so that the first NPN triode is continuously conducted, the PNP triode and the second NPN triode continuously receive a low-level signal, the PNP triode is continuously conducted, the second NPN triode is continuously disconnected, the protection circuit maintains self-locking, and can reset only after being electrified again, and the reliability of the leakage protection function is improved.

When the heater heats the water in the container, the water temperature starts to rise, when the water temperature in the container exceeds a first temperature, the voltage signal output by the first temperature detection unit 21 is smaller than the voltage signal output by the first voltage division unit 22, at this time, the first comparator U2 outputs a high level signal to the base of the third NPN triode, the third NPN triode is conducted, the cathode of the first diode d1 is grounded, the base of the second NPN triode receives a low level signal, the second NPN triode is disconnected, the connection between the first end of the alternating current power supply and the heater is disconnected, the heater cannot be powered, the operation is stopped, and the over-temperature protection is realized. When the heater is powered off, the water in the container is slowly cooled, when the water temperature in the container is lower than the switching temperature, the voltage signal output by the first temperature detection unit 21 is greater than the voltage signal output by the first voltage division unit 22, at this time, the first comparator U2 outputs a low level signal to the base of the third NPN triode, the third NPN triode is disconnected, the base of the second NPN triode receives the high level signal again through the first resistor R1, the second NPN triode is conducted, the connection between the first end of the alternating current power supply and the heater is reestablished, the heater is powered again, and the water in the container is heated again.

If the temperature of the container is too high, such as exceeding the second temperature, at this time, the voltage signal output by the second temperature detecting unit 22 is less than the voltage signal output by the second voltage dividing unit 32, and at this time, the second comparator U3 outputs a low level signal to the base of the PNP transistor and the cathode of the second diode d 2. At the moment, the base electrode of the second NPN triode receives the low-level signal, the second NPN triode is disconnected, the connection between the first end of the alternating current power supply and the heater is disconnected, the heater cannot be powered, the heater stops working, and the over-temperature protection is achieved. And because the PNP triode is conducted, the first power supply end VCC outputs a high-level signal to the first NPN triode through the PNP triode, so that the first NPN triode is continuously conducted, the PNP triode and the second NPN triode continuously receive a low-level signal, the PNP triode is continuously conducted, the second NPN triode is continuously disconnected, the protection circuit maintains self-locking, and can reset only after being electrified again, and the reliability of the over-temperature protection function is improved.

If no electric leakage occurs after the household electrical appliance is powered on, namely the electric leakage detection module 10 outputs a low level signal to the first NPN triode, the first NPN triode is turned off, and when the temperature of the water in the container of the heating device does not exceed the first temperature, namely the third NPN triode is turned off, and when the temperature of the container does not exceed the second temperature, the second comparator U3 outputs a high level signal, the protection circuit does not trigger the protection action.

In addition, a low level signal can be output to the third switching module 60 through the control module 80, so that the base of the second NPN transistor receives the low level signal, the second NPN transistor is disconnected, the connection between the first end of the ac power supply and the heater is disconnected, the heater cannot be powered, and the operation is stopped.

In summary, in the circuit, when the alternating current power supply leaks electricity, the connection between the alternating current power supply and the heater can be disconnected, so that the circuit has an electric leakage protection function; when the water temperature exceeds the first temperature and/or the temperature of the container exceeds the second temperature, the connection between the alternating current power supply and the heater can be disconnected, and the over-temperature protection function is realized. Therefore, the protection circuit combines the leakage protection circuit and the over-temperature protection circuit into a whole, thereby simplifying the circuit structure and reducing the circuit cost.

In addition, when one of the first switch module 40 and the second switch module 50 is turned on, the other switch module is also turned on, so that the two switch modules are continuously turned on, and the first end of the third switch module 60 is continuously grounded GND, thereby improving the safety and reliability of the protection circuit 100 during operation. Moreover, the protection circuit can trigger protection through the control module 80, and subsequently, programmed control can be realized.

In a second aspect, an embodiment of the present invention further provides a household electrical appliance, which includes a heating device and a protection circuit as in any one of the first aspect. The heating device comprises a heater and a container, and the heater is used for heating water in the container. The household appliance can be an intelligent coordinate device, an ironing machine and other household appliances. In this embodiment, the protection circuit has the structure and the function as described in any one of the embodiments of the first aspect, and details are not described herein.

It should be noted that the above-described embodiments of the apparatus are merely illustrative, where the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit it; within the idea of the invention, also technical features in the above embodiments or in different embodiments can be combined, steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications or substitutions do not depart from the scope of the invention in its corresponding aspects.

Claims (12)

1. A protection circuit for a heating device, the heating device including a heater and a container, the protection circuit comprising: the device comprises an electric leakage detection module, a first temperature detection module, a second temperature detection module, a first switch module, a second switch module and a third switch module;

the first input end of the leakage detection module is used for being connected with the first end of an alternating current power supply, the second input end of the leakage detection module is used for being connected with the second end of the alternating current power supply, the output end of the leakage detection module is connected with the first end of the first switch module, and the leakage detection module is used for outputting a first level signal to the first switch module according to the current difference between the first end and the second end of the alternating current power supply;

the second end of the first switch module is grounded, the third end of the first switch module is respectively connected with the first end of the second switch module, the first end of the third switch module, the output end of the first temperature detection module and the output end of the second temperature detection module, and the first switch module is used for being conducted according to the first level signal and outputting a second level signal to the first end of the second switch module and the first end of the third switch module; the first temperature detection module is used for outputting a second level signal to the first end of the third switch module when the water temperature in the container exceeds a first temperature; the second temperature detection module is used for outputting a second level signal to the first end of the third switch module and the first end of the second switch module when the temperature of the container exceeds a second temperature;

the second terminal of the second switch module is used for connecting a first power terminal, the third terminal of the second switch module is connected to the first terminal of the first switch module, and the second switch module is used for conducting according to the second level signal, so that the first power terminal outputs a first level signal to the first terminal of the first switch module through the second switch module, and the first switch module is conducted;

the second end of the third switch module is used for being connected with the first end of the alternating current power supply, the third end of the third switch module is used for being connected with the heater, and the third switch module is used for disconnecting the alternating current power supply from the heater according to the second level signal.

2. The protection circuit of claim 1, further comprising a first resistor;

the first end of the first resistor is used for being connected with the first power supply end, and the second end of the first resistor is connected with the first end of the third switch module.

3. The protection circuit of claim 2, further comprising a first diode pair comprising a first diode and a second diode;

the cathode of the first diode is connected with the output end of the first temperature detection module, the cathode of the second diode is respectively connected with the output end of the second temperature detection module, the third end of the first switch module and the first end of the second switch module, and the anode of the first diode and the anode of the second diode are both connected with the first end of the third switch module.

4. The protection circuit of claim 3, further comprising a voltage divider module;

the first end of the voltage division module is used for being connected with the first power end, the second end of the voltage division module is connected with the second end of the second switch module, and the third end of the voltage division module is respectively connected with the cathode of the second diode, the third end of the first switch module and the output end of the first temperature detection module.

5. The protection circuit according to any one of claims 1 to 4, wherein the first switching module comprises a first switching tube;

the first end of the first switch tube is connected with the output end of the electric leakage detection module and the third end of the second switch module respectively, the second end of the first switch tube is grounded, and the third end of the first switch tube is connected with the output end of the second temperature detection module, the first end of the second switch module and the first end of the third switch module respectively.

6. The protection circuit according to any one of claims 1-4, wherein the second switching module comprises a second switching tube;

the first end of the second switch tube is connected with the third end of the first switch module, the output end of the second temperature detection module and the first end of the third switch module respectively, the second end of the second switch tube is used for being connected with the first power supply end, and the third end of the second switch tube is connected with the first end of the first switch module and the output end of the electric leakage detection module respectively.

7. The protection circuit according to any one of claims 1 to 4, wherein the third switching module comprises a third switching tube and a relay;

the first end of third switch tube is connected respectively the output of first temperature detect module, the output of second temperature detect module the third terminal of first switch module with the first end of second switch module, the second end ground connection of third switch tube, the third terminal of third switch tube is connected the first end of relay, the second end of relay is used for connecting first power end, the third terminal of relay is used for connecting alternating current power supply's first end, the fourth end of relay is used for connecting the heater.

8. The protection circuit according to any one of claims 1-4, wherein the leakage detection module comprises a current transformer, an anti-aliasing unit and a leakage detection chip;

the current transformer is buckled at alternating current power supply's first end with alternating current power supply's second end respectively, current transformer's output is connected the input of anti-aliasing unit, the output of anti-aliasing unit is connected the input of electric leakage detection chip, the output of electric leakage detection chip is connected the first end of first switch module.

9. The protection circuit according to any one of claims 1-4, wherein the first temperature detection module comprises a first temperature detection unit, a first voltage division unit, a first comparator and a fourth switch tube;

the output end of the first temperature detection unit is connected with the first input end of the first comparator, the output end of the first voltage division unit is connected with the second input end of the first comparator, the output end of the first comparator is connected with the first end of the fourth switch tube, the second end of the fourth switch tube is grounded, and the third end of the fourth switch tube is connected with the first end of the third switch module.

10. The protection circuit according to any one of claims 1 to 4, wherein the second temperature detection module comprises a second temperature detection unit, a second voltage division unit and a second comparator;

the output end of the second voltage division unit is connected with the first input end of the second comparator, the output end of the second temperature detection unit is connected with the second input end of the second comparator, and the output end of the second comparator is respectively connected with the third end of the first switch module, the first end of the second switch module and the first end of the third switch module.

11. The protection circuit according to any one of claims 1 to 4, wherein the protection circuit further comprises a control module;

the control module is connected with the first end of the third switch module.

12. A household appliance comprising a heating device and a protection circuit according to any one of claims 1 to 11;

the heating device comprises a heater and a container, wherein the heater is used for heating water in the container.

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