Protection circuit of electrical equipment and electrical equipment

Abstract

The utility model provides a protection circuit for electrical equipment and the electrical equipment, and the protection circuit comprises a filtering rectification module which is used for converting the alternating current inputted from the alternating current input end of the filtering rectification module into the direct current outputted from the direct current output end of the filtering rectification module; the first end of the protection module is electrically connected with the direct current output end so as to receive power supplied by an electrolytic capacitor in the filtering and rectifying module; the second end of the protection module is provided with an optocoupler unit, and the optocoupler unit is electrically connected to the two ends of the thermosensitive unit through a connecting circuit. The protection module further comprises a control unit and a detection unit. The detection unit is used for detecting the voltage value of the electrolytic capacitor. The utility model solves the technical problems that the relay is easy to generate electric sparks in the process of executing the closing action, novel environment-friendly refrigerants R290, R600a and the like are applied to an air-conditioning system, but have certain flammability, so that the refrigerants are easy to ignite in the process of executing the action of the relay after being leaked, and the risk of explosion is caused.

Description

Technical Field

[0001] The utility model relates to the technical field of air conditioners, in particular to a protection circuit of electrical equipment and the electrical equipment. Background Art

[0002] Air conditioning equipment is being used more and more widely in people's daily lives, but the safety issues it brings are also becoming increasingly prominent.

[0003] In order to ensure the normal operation of the air conditioner, a conversion circuit is often provided inside the air conditioner to convert the alternating current input from the mains into direct current, which is used to power various electronic components inside the air conditioner.

[0004] Specifically, the conversion circuit includes a thermistor and an electrolytic capacitor for storing electrical energy. At the moment of starting the air conditioner, the voltage difference between the electrolytic capacitor and the input end of the conversion circuit is large, which can easily cause the electrolytic capacitor to burn out. Therefore, the thermistor plays the main role of voltage division. However, as the power-on time increases, the temperature of the thermistor increases, causing its resistance value to increase, which in turn hinders the power supply to the electrolytic capacitor. In order to ensure continuous power supply to the electrolytic capacitor, relays are often added at both ends of the thermistor. By controlling the relay to close to short-circuit the thermistor, the purpose of continuous power supply to the electrolytic capacitor is achieved.

[0005] However, the relay is prone to generate sparks during the closing action. Combined with the refrigerant leakage in the air conditioner, since new environmentally friendly refrigerants such as R290 and R600a have been used in the air conditioning system, they are flammable. After leakage, they are easily ignited during the relay action, resulting in the risk of explosion. Therefore, it is urgent to propose an effective flame retardant and explosion-proof method to improve the safety of air conditioners during use. Utility Model Content

[0006] The technical problem solved by the utility model is that electric sparks are easily generated in the process of the relay executing the closing action. Since new environmentally friendly refrigerants such as R290 and R600a have been used in air-conditioning systems, they are flammable to a certain extent. After leakage, they are easily ignited in the process of the relay executing the action, resulting in the risk of explosion.

[0007] In order to solve the above problems, the utility model provides a protection circuit for electrical equipment, including: a filter and rectifier module, the filter and rectifier module is used to convert the alternating current input from its AC input end into direct current output from its DC output end; a protection module, the first end of the protection module is electrically connected to the DC output end to receive power from the electrolytic capacitor in the filter and rectifier module; the second end of the protection module is provided with an optical coupling unit, the optical coupling unit is electrically connected to the two ends of the thermistor unit through a connecting circuit, and the thermistor unit is electrically connected between the AC input end and the electrolytic capacitor; the protection module also includes a control unit and a detection unit, the detection unit is used to detect the voltage value of the electrolytic capacitor; wherein, when the voltage value is greater than a preset voltage value, the control unit controls the optical coupling unit to be in a first state so that the connecting circuit short-circuits the thermistor unit; when the voltage value is less than or equal to the preset voltage value, the control unit controls the optical coupling unit to be in a second state so that the connecting circuit is open.

[0008] Compared with the prior art, the technical effect achieved by adopting the technical solution is as follows: Specifically, by replacing the relay with the optocoupler unit, the situation in which the relay generates electric sparks when the optocoupler unit switches between the first state and the second state is avoided, so that even if the air conditioner accidentally leaks refrigerant, the risk of ignition and explosion is avoided, thereby improving the safety of the air conditioner operation process. For example, the optocoupler unit is an optocoupler resistor, which is formed by packaging a light-emitting diode and a light-emitting transistor.

[0009] In one example of the utility model, the optocoupler unit includes a receiving end and a transmitting end, the transmitting end is electrically connected to the protection module, and the receiving end is electrically connected to the connecting circuit; wherein the receiving end is used to receive the optical signal formed by the transmitting end to enable the optocoupler unit to enter the first state.

[0010] Compared with the prior art, the technical effect achieved by adopting this technical solution is as follows: specifically, when the transmitting end generates an optical signal, it indicates that the voltage value in the electrolytic capacitor has reached a preset voltage value at this time. Correspondingly, the resistance value of the thermistor is relatively large. In order to ensure continuous and stable power supply to the electrolytic capacitor, the thermistor needs to be short-circuited. Therefore, the optical signal is smoothly received by the receiving end to enable the connection circuit to be realized through the optical coupling unit, thereby completing the short circuit of the thermistor, so that the AC power input from the AC input end no longer passes through the thermistor, but passes through the connection circuit instead. At the same time, the transmission of the optical signal is used as a means to conduct the connection circuit, which effectively avoids the accidental situation of generating electric sparks and then detonating the leakage of refrigerant, thereby improving the safety of the air conditioner operation.

[0011] In one example of the utility model, the protection module includes a first circuit and a second circuit; the first end of the first circuit is electrically connected to the DC output end, the control unit, the detection unit and the transmitting end are electrically connected to the first circuit, and the first circuit is also electrically connected to a first resistor, a second resistor and a first transistor; one end of the first resistor is electrically connected to the first positive pin of the transmitting end, and the other end is electrically connected to the second end of the second circuit; the second negative pin of the transmitting end is electrically connected to the collector of the first transistor, the emitter of the first transistor is grounded, the base of the first transistor is electrically connected to one end of the second resistor, and the other end of the second resistor is electrically connected to the first end of the control unit; the first end of the second circuit is electrically connected to the DC output end, and the second circuit is provided with a power supply module, the power supply module receives the DC power input by the DC output end, and the power supply module is electrically connected to the second end of the control unit for powering the control unit.

[0012] Compared with the prior art, the technical effect achieved by adopting the technical solution is as follows: specifically, the inspection and detection unit detects the voltage value in the electrolytic capacitor, and sends the electrical signal corresponding to the voltage value to the control unit, and the control unit determines whether to turn on the first transistor according to the electrical signal, so that the transmitting end forms an optical signal. For example, when the corresponding information in the electrical signal is that the voltage value in the electrolytic capacitor is greater than the preset voltage value, the control unit controls the first transistor to be turned on, so that the transmitting end forms an optical signal, and then the receiving end receives the optical signal to short-circuit the thermistor unit in the connecting circuit; otherwise, the control unit controls the first transistor not to be turned on, so that the transmitting end cannot form an optical signal, and then the connecting circuit is in an open circuit; in addition, by setting the first resistor and the second resistor, the circuit is protected.

[0013] In one example of the utility model, the filtering and rectifying module also includes a rectifier bridge, a first common mode filtering unit and a second differential mode filtering unit; one end of the first common mode filtering unit is electrically connected to the AC input end, and the other end is electrically connected to one end of the thermistor unit and the rectifier input end of the rectifier bridge, and the other end of the thermistor unit is electrically connected to the rectifier input end of the rectifier bridge; one end of the second differential mode filtering unit is electrically connected to the rectifier input end, and the other end is electrically connected to the rectifier output end; wherein the current output from the rectifier output end first passes through the second differential mode filtering unit and then enters the electrolytic capacitor.

[0014] Compared with the prior art, the technical effect achieved by adopting this technical solution is as follows: common-mode interference to current is achieved through the first common-mode filtering unit, and correspondingly, differential-mode interference to current is achieved through the second differential-mode filtering unit.

[0015] In one example of the utility model, the first common-mode filtering unit includes a common-mode inductor composed of a first winding and a second winding, one end of the first winding is electrically connected to the live wire AC-L of the AC input end, and the other end is electrically connected to the input end of the connection circuit and the thermistor unit respectively; one end of the second winding is electrically connected to the neutral wire AC-N of the AC input end, and the other end is electrically connected to the rectifier input end of the rectifier bridge.

[0016] In an example of the present utility model, the filter rectifier module further includes a fuse, which is electrically connected to the live wire AC-L.

[0017] In one example of the utility model, the positive terminal of the rectifier bridge and the input terminal of the electrolytic capacitor are electrically connected to the third circuit, and the negative terminal of the rectifier bridge and the output terminal of the electrolytic capacitor are electrically connected to the fourth circuit; the second differential mode filtering unit includes a varistor, a film capacitor, a differential mode inductor and a third diode; one end of the varistor is electrically connected to the third circuit, and the other end is electrically connected to the fourth circuit, one end of the film capacitor is electrically connected to the third circuit, and the other end is electrically connected to the fourth circuit; the differential mode inductor is electrically connected to the third circuit; the third diode is electrically connected to the third circuit, so that the current of the third circuit enters the input terminal of the electrolytic capacitor.

[0018] On the other hand, the utility model further provides an electrical device, including: a protection circuit as in any of the above examples.

[0019] Compared with the prior art, the technical effect achieved by adopting this technical solution is: it can achieve the technical effect corresponding to any of the above-mentioned technical solutions, which will not be repeated here.

[0020] In an example of the present invention, the electrical device is an air conditioner.

[0021] Compared with the prior art, the technical effect achieved by adopting this technical solution is as follows: in the case of refrigerant leakage in the air conditioner, the explosion caused by ignition of the refrigerant by the relay due to the refrigerant leakage is effectively avoided, thereby improving the safety of the air conditioner operation.

[0022] After adopting the technical solution of the utility model, the following technical effects can be achieved:

[0023] (1) By replacing the relay with the optocoupler unit, the situation in which the relay generates electric sparks when the optocoupler unit switches between the first state and the second state is avoided, so that even if the air conditioner accidentally leaks refrigerant, the risk of ignition and explosion is avoided, thereby improving the safety of the air conditioner operation process;

[0024] (2) Specifically, the inspection and detection unit detects the voltage value in the electrolytic capacitor and sends an electrical signal corresponding to the voltage value to the control unit, and the control unit determines whether to turn on the first transistor according to the electrical signal, so that the transmitting end forms an optical signal. For example, when the corresponding information in the electrical signal is that the voltage value in the electrolytic capacitor is greater than the preset voltage value, the control unit controls the first transistor to turn on, so that the transmitting end forms an optical signal, so that the receiving end receives the optical signal to short-circuit the thermistor unit in the connecting circuit; otherwise, the control unit controls the first transistor not to turn on, so that the transmitting end cannot form an optical signal, so that the connecting circuit is in an open circuit; in addition, by setting the first resistor and the second resistor, the circuit is protected. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a schematic diagram of a circuit connection of an electrical device having a relay in the prior art.

[0026] Figure 2 A circuit connection diagram of a protection circuit of an electrical device provided in an embodiment of the utility model.

[0027] Description of reference numerals:

[0028] 100, protection circuit; 10, electrolytic capacitor; 20, optical coupling unit; 21, transmitting end; 22, receiving end; 31, connecting circuit; 32, first circuit; 33, second circuit; 34, third circuit; 35, fourth circuit; 41, thermal sensing unit; 42, first common mode filtering unit; 43, rectifier bridge; 44, varistor; 45, film capacitor; 46, differential mode inductor; 47, third diode; 48, first triode; 51, control unit; 52, detection unit; 53, first resistor; 54, second resistor; 55, power module;

[0029] 200. Relay. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] See also Figure 1 , which is a circuit connection diagram of an electrical device with a relay 200 in the prior art. Figure 2, which is a circuit connection diagram of a protection circuit 100 of an electrical device provided by an embodiment of the utility model. Specifically, the protection circuit 100 specifically includes a filter rectifier module and a protection module; the filter rectifier module is used to convert the AC power input from its AC input end into the DC power output from its DC output end; the first end of the protection module is electrically connected to the DC output end to receive the power supply from the electrolytic capacitor 10 in the filter rectifier module; the second end of the protection module is provided with an optical coupling unit 20, and the optical coupling unit 20 is electrically connected to the two ends of the thermistor unit 41 through the connecting circuit 31, and the thermistor unit 41 is electrically connected between the AC input end and the electrolytic capacitor 10.

[0032] Specifically, by replacing the relay 200 with the optocoupler unit 20, the optocoupler unit 20 avoids the situation where the relay 200 generates electric sparks when performing an action during the conversion between the first state and the second state, so that even if the air conditioner accidentally leaks refrigerant, the risk of ignition and explosion is avoided, thereby improving the safety of the air conditioner operation process. For example, the optocoupler unit 20 is an optocoupler resistor, which is formed by packaging a light emitting diode and a light emitting transistor.

[0033] Furthermore, the protection module also includes a control unit 51 and a detection unit 52, the detection unit 52 is used to detect the voltage value of the electrolytic capacitor 10; wherein, when the voltage value is greater than a preset voltage value, the control unit 51 controls the optocoupler unit 20 to be in a first state so that the connection circuit 31 short-circuits the thermistor unit 41; when the voltage value is less than or equal to the preset voltage value, the control unit 51 controls the optocoupler unit 20 to be in a second state so that the connection circuit 31 is open.

[0034] Specifically, when the transmitting end 21 generates an optical signal, it means that the voltage value in the electrolytic capacitor 10 has reached the preset voltage value. Correspondingly, the resistance value of the thermistor 41 is relatively large. In order to ensure continuous and stable power supply to the electrolytic capacitor 10, the thermistor 41 needs to be short-circuited. Therefore, the optical signal is smoothly received by the receiving end 22, so that the connection circuit 31 is turned on through the optical coupling unit 20, and then the short circuit of the thermistor is completed, so that the AC power input from the AC input end no longer passes through the thermistor, but passes through the connection circuit 31 instead. At the same time, the transmission of the optical signal is used as a means to turn on the connection circuit 31, which effectively avoids the accidental situation of generating electric sparks and then detonating the leakage of refrigerant, thereby improving the safety of the air conditioner operation.

[0035] In contrast, when the voltage value is less than or equal to the preset voltage value, it indicates that the potential of the electrolytic capacitor 10 is too small, and the thermal sensing unit 41 is still required to play a voltage dividing role to protect the electrolytic capacitor 10. Therefore, in this case, the control unit 51 is used to control the emitter to be non-conductive, that is, it cannot form an optical signal, thereby ensuring that the connecting circuit 31 remains open, that is, disconnected.

[0036] Preferably, the optical coupling unit 20 includes a receiving end 22 and a transmitting end 21, the transmitting end 21 is electrically connected to the protection module, and the receiving end 22 is electrically connected to the connecting circuit 31; wherein the receiving end 22 is used to receive the optical signal formed by the transmitting end 21 to enable the optical coupling unit 20 to enter the first state.

[0037] Preferably, the protection module includes a first circuit 32 and a second circuit 33; a first end of the first circuit 32 is electrically connected to the DC output end, a control unit 51, a detection unit 52 and a transmitter 21 are electrically connected to the first circuit 32, and the first circuit 32 is also electrically connected to a first resistor 53, a second resistor 54 and a first transistor 48; one end of the first resistor 53 is electrically connected to a first positive pin of the transmitter 21, and the other end is electrically connected to a second end of the second circuit 33; the second negative pin of the transmitter 21 is electrically connected to the collector of the first transistor 48, the emitter of the first transistor 48 is grounded, the base of the first transistor 48 is electrically connected to one end of the second resistor 54, and the other end of the second resistor 54 is electrically connected to a first end of the control unit 51; a first end of the second circuit 33 is electrically connected to the DC output end, and the second circuit 33 is provided with a power module 55, the power module 55 receives the DC power input by the DC output end, and the power module 55 is electrically connected to the second end of the control unit 51 for powering the control unit 51.

[0038] Specifically, the inspection and detection unit 52 detects the voltage value in the electrolytic capacitor 10, and sends the electrical signal corresponding to the voltage value to the control unit 51, and the control unit 51 determines whether to turn on the first transistor 48 according to the electrical signal, so that the transmitting end 21 forms an optical signal. For example, when the corresponding information in the electrical signal is that the voltage value in the electrolytic capacitor 10 is greater than the preset voltage value, the control unit 51 controls the first transistor 48 to be turned on, so that the transmitting end 21 forms an optical signal, so that the receiving end 22 receives the optical signal to make the connection circuit 31 short-circuit the thermistor unit 41; otherwise, the control unit 51 controls the first transistor 48 not to be turned on, so that the transmitting end 21 cannot form an optical signal, so that the connection circuit 31 is in an open circuit; in addition, by setting the first resistor 53 and the second resistor 54, the circuit is protected.

[0039] Preferably, the filter and rectifier module further includes a rectifier bridge 43, a first common mode filtering unit 42 and a second differential mode filtering unit; one end of the first common mode filtering unit 42 is electrically connected to the AC input terminal, and the other end is electrically connected to one end of the thermistor unit 41 and the rectifier input terminal of the rectifier bridge 43, and the other end of the thermistor unit 41 is electrically connected to the rectifier input terminal of the rectifier bridge 43; one end of the second differential mode filtering unit is electrically connected to the rectifier input terminal, and the other end is electrically connected to the rectifier output terminal; wherein the current output from the rectifier output terminal first passes through the second differential mode filtering unit and then enters the electrolytic capacitor 10. Common mode interference of current is achieved through the first common mode filtering unit 42, and correspondingly, differential mode interference of current is achieved through the second differential mode filtering unit.

[0040] Preferably, the first common-mode filtering unit 42 includes a common-mode inductor composed of a first winding and a second winding, one end of the first winding is electrically connected to the live wire AC-L of the AC input end, and the other end is electrically connected to the input end of the connection circuit 31 and the thermistor unit 41 respectively; one end of the second winding is electrically connected to the neutral wire AC-N of the AC input end, and the other end is electrically connected to the rectifier input end of the rectifier bridge 43.

[0041] Preferably, the filter and rectifier module further comprises a fuse, which is electrically connected to the live wire AC-L.

[0042] Preferably, the positive terminal of the rectifier bridge 43 and the input terminal of the electrolytic capacitor 10 are electrically connected to the third circuit 34, and the negative terminal of the rectifier bridge 43 and the output terminal of the electrolytic capacitor 10 are electrically connected to the fourth circuit 35; the second differential mode filtering unit includes a varistor 44, a film capacitor 45, a differential mode inductor 46 and a third diode 47; one end of the varistor 44 is electrically connected to the third circuit 34, and the other end is electrically connected to the fourth circuit 35, one end of the film capacitor 45 is electrically connected to the third circuit 34, and the other end is electrically connected to the fourth circuit 35; the differential mode inductor 46 is electrically connected to the third circuit 34; the third diode 47 is electrically connected to the third circuit 34, so that the current of the third circuit 34 enters the input terminal of the electrolytic capacitor 10.

[0043] Combination Figure 1 and Figure 2 In a specific example, for ease of understanding, the fuse is represented by FUSE1, the thermistor 41 is represented by PTC1, the relay 200 is represented by RY1, the rectifier bridge 43 is represented by BG1, the optocoupler unit 20 is represented by U6, the varistor 44 is represented by RV2, the film capacitor 45 is represented by C9, the differential mode inductor 46 is represented by L1, the third diode 47 is represented by D, the electrolytic capacitor 10 is represented by E1, the first resistor 53 is represented by R90, the second resistor 54 is represented by R96, the first transistor 48 is represented by Q4, and the control unit 51 is represented by MCU.

[0044] On the other hand, the embodiment of the utility model further provides an electrical device, specifically, the electrical device includes the protection circuit 100 in the above embodiment. Correspondingly, this embodiment can achieve the technical effect corresponding to any technical solution in the above embodiment.

[0045] Furthermore, the electrical equipment is, for example, an air conditioner.

[0046] Although the utility model is disclosed as above, the utility model is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the utility model. Therefore, the protection scope of the utility model shall be subject to the scope defined by the claims.

Claims

1. A protection circuit for an electrical device, characterized in that: include: A filter and rectifier module, the filter and rectifier module is used to convert the alternating current input from its alternating current input terminal into direct current output from its direct current output terminal; A protection module, wherein a first end of the protection module is electrically connected to the DC output end so as to receive power from the electrolytic capacitor (10) in the filter rectifier module; a second end of the protection module is provided with an optical coupling unit (20), the optical coupling unit (20) is electrically connected to two ends of a thermal sensing unit (41) through a connecting circuit (31), and the thermal sensing unit (41) is electrically connected between the AC input end and the electrolytic capacitor (10); The protection module further comprises a control unit (51) and a detection unit (52), wherein the detection unit (52) is used to detect the voltage value of the electrolytic capacitor (10); Wherein, when the voltage value is greater than a preset voltage value, the control unit (51) controls the optical coupling unit (20) to be in a first state so that the connection circuit (31) short-circuits the thermal sensitive unit (41); When the voltage value is less than or equal to the preset voltage value, the control unit (51) controls the optical coupling unit (20) to be in a second state, so that the connection circuit (31) is open.

2. The protection circuit according to claim 1, characterized in that: The optical coupling unit (20) comprises a receiving end (22) and a transmitting end (21), the transmitting end (21) is electrically connected to the protection module, and the receiving end (22) is electrically connected to the connection circuit (31); The receiving end (22) is used to receive the optical signal generated by the transmitting end (21), so as to enable the optical coupling unit (20) to enter the first state.

3. The protection circuit according to claim 2, characterized in that: The protection module comprises a first circuit (32) and a second circuit (33); The first end of the first circuit (32) is electrically connected to the DC output end, the control unit (51), the detection unit (52) and the transmitting end (21) are electrically connected to the first circuit (32), and the first circuit (32) is also electrically connected to a first resistor (53), a second resistor (54) and a first triode (48); One end of the first resistor (53) is electrically connected to the first positive pin of the transmitting end (21), and the other end is electrically connected to the second end of the second circuit (33); the second negative pin of the transmitting end (21) is electrically connected to the collector of the first triode (48), the emitter of the first triode (48) is grounded, the base of the first triode (48) is electrically connected to one end of the second resistor (54), and the other end of the second resistor (54) is electrically connected to the first end of the control unit (51); The first end of the second circuit (33) is electrically connected to the DC output end, and the second circuit (33) is provided with a power module (55), the power module (55) receives the DC power input from the DC output end, and the power module (55) is electrically connected to the second end of the control unit (51) for supplying power to the control unit (51).

4. The protection circuit according to claim 1, characterized in that: The filtering and rectifying module further comprises a rectifying bridge (43), a first common-mode filtering unit (42) and a second differential-mode filtering unit; One end of the first common-mode filtering unit (42) is electrically connected to the AC input end, and the other end is electrically connected to one end of the thermal sensing unit (41) and the rectifier input end of the rectifier bridge (43); the other end of the thermal sensing unit (41) is electrically connected to the rectifier input end of the rectifier bridge (43); One end of the second differential mode filtering unit is electrically connected to the rectifier input end, and the other end is electrically connected to the rectifier output end; The current outputted from the rectifier output terminal first passes through the second differential mode filtering unit and then enters the electrolytic capacitor (10).

5. The protection circuit according to claim 4, characterized in that: The first common mode filtering unit (42) comprises a common mode inductor composed of a first winding and a second winding, one end of the first winding is electrically connected to the live wire AC-L of the AC input end, and the other end is electrically connected to the input end of the connection circuit (31) and the thermal sensitive unit (41) respectively; One end of the second winding is electrically connected to the neutral line AC-N of the AC input end, and the other end is electrically connected to the rectifier input end of the rectifier bridge (43).

6. The protection circuit according to claim 5, characterized in that: The filtering and rectifying module further comprises a fuse, and the fuse is electrically connected to the live wire AC-L.

7. The protection circuit according to claim 4 or 5, characterized in that: The positive terminal of the rectifier bridge (43) and the input terminal of the electrolytic capacitor (10) are electrically connected to a third circuit (34), and the negative terminal of the rectifier bridge (43) and the output terminal of the electrolytic capacitor (10) are electrically connected to a fourth circuit (35); The second differential mode filtering unit comprises a varistor (44), a film capacitor (45), a differential mode inductor (46) and a third diode (47); One end of the varistor (44) is electrically connected to the third circuit (34), and the other end is electrically connected to the fourth circuit (35); one end of the film capacitor (45) is electrically connected to the third circuit (34), and the other end is electrically connected to the fourth circuit (35); The differential mode inductor (46) is electrically connected to the third circuit (34); The third diode (47) is electrically connected to the third circuit (34) so ​​that the current of the third circuit (34) enters the input end of the electrolytic capacitor (10).

8. An electrical device, characterized in that: include: A protection circuit as claimed in any one of claims 1 to 7.

9. The electrical device according to claim 8, characterized in that: The electrical equipment is an air conditioner.

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