EMI noise current counteracting circuit and air conditioning system

Abstract

The embodiment of the utility model discloses an EMI noise current counteracting circuit and an air conditioning system, and relates to the field of noise reduction circuits. The circuit comprises a current detection module, a passive filtering module, a noise module and a current offset module. The three-phase input end of the current detection module is connected with the three-phase output end of a power grid, the three-phase output end of the current detection module is connected with the three-phase input end of the passive filtering module, the detection end of the current offset module is connected with the detection end of the current detection module, and the current offset module detects the current value of noise current through the current detection module. The offset currents are the same in output current value and opposite to the noise current in direction; the neutral end of the current counteracting module is connected with the neutral end of the power grid, the grounding protection end of the current counteracting module is connected with the grounding protection end of the power grid, and the current counteracting module inputs counteracting current into the EMI noise current counteracting circuit to counteract noise current.

Description

TECHNICAL FIELD

[0001] The present application relates to a noise reduction circuit, in particular to an EMI noise current cancellation circuit and an air conditioning system. BACKGROUND

[0002] In an air conditioning system, due to the use of PWM pulse width modulation in motor control, the parasitic capacitance between the motor winding and the shell can form a current path at high frequency, so that high-frequency noise is coupled to the ground system through the parasitic capacitance, generating a conductive electromagnetic interference mainly in the form of common-mode current. Electromagnetic interference (EMI) is mainly concentrated in the low frequency band (such as tens of kilohertz to hundreds of kilohertz). In order to meet the relevant requirements, an EMI filter needs to be used to reduce the EMI interference current flowing from the air conditioning equipment to the power supply.

[0003] Traditional EMI filters rely on common-mode inductors and capacitive elements to achieve filtering functions. The common-mode inductor is mainly composed of a magnetic core and a winding. In order to achieve the EMI filtering effect, especially in the low frequency band, a common-mode inductor with high inductance is required, so the number of turns of the inductor winding will be more and the magnetic core will be larger, which will result in a larger volume and weight of the common-mode inductor and a higher cost. At the same time, in a high-power air conditioning system, the common-mode inductor with large inductance will generate a lot of heat during operation, which requires effective heat dissipation measures. This further increases the complexity and volume of the air conditioning system. UTILITY MODEL CONTENT

[0004] The EMI noise current cancellation circuit and the air conditioning system provided by the embodiments of the present application can solve the above problems. The technical solutions are as follows:

[0005] In a first aspect, the embodiments of the present application provide an EMI noise current cancellation circuit, which comprises:

[0006] a current detection module, a passive filter module, a noise module, and a current cancellation module;

[0007] The three-phase input terminals of the current detection module are connected to the three-phase output terminals of the power grid, the three-phase output terminals of the current detection module are connected to the three-phase input terminals of the passive filter module, and the three-phase output terminals of the passive filter module are connected to the three-phase input terminals of the noise module. The noise module is used to work according to the working voltage provided by the power grid;

[0008] The passive filter module filters and processes the noise current to be processed generated when the noise module works, and obtains a noise current;

[0009] The detection end of the current offset module is connected with the detection end of the current detection module, the current offset module detects the current value of the noise current through the current detection module, and outputs an offset current with the same current value and opposite direction to the noise current;

[0010] The neutral end of the current offset module is connected with the neutral end of the power grid, the grounding protection end of the current offset module is connected with the grounding protection end of the power grid, and the current offset module inputs the offset current into the EMI noise current offset circuit to offset the noise current.

[0011] In a second aspect, the embodiments of the present application provide an air conditioning system, which comprises the EMI noise current offset circuit according to the first aspect.

[0012] The technical solutions provided by some embodiments of the present application have at least the following beneficial effects:

[0013] The EMI noise current offset circuit provided by the present application comprises a current detection module, a passive filtering module, a noise module and a current offset module. The passive filtering module performs filtering processing on the noise current to be processed generated by the noise module during operation to obtain a noise current, the current offset module detects the current value of the noise current through the current detection module, and outputs an offset current with the same current value and opposite direction to the noise current, and further inputs the offset current into the EMI noise current offset circuit to offset the noise current. In other words, the current offset module and the current detection module comprising a low inductance common mode inductor are used to eliminate the EMI noise current, and the suppression of the noise current is no longer dependent on a large inductance common mode inductor, so that the volume, weight, heat and cost of the common mode inductor in the current offset module and the current detection module for realizing the EMI filtering and noise reduction function can be reduced. The noise reduction effect of the EMI circuit is good through the preliminary filtering processing by the passive filtering module and the further noise reduction processing by the current offset module. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0015] Figure 1 is a structural schematic diagram of an EMI noise current offset circuit provided by an embodiment of the present application;

[0016] Figure 2Fig. 6 is a structural schematic diagram of an EMI noise current cancellation circuit according to an embodiment of the present application;

[0017] Figure 3 Fig. 7 is a structural schematic diagram of an EMI noise current cancellation circuit according to an embodiment of the present application;

[0018] Figure 4 Fig. 8 is a structural schematic diagram of an EMI noise current cancellation circuit according to an embodiment of the present application;

[0019] Figure 5 Fig. 9 is a structural schematic diagram of an EMI noise current cancellation circuit according to an embodiment of the present application;

[0020] Figure 6 Fig. 10 is a structural schematic diagram of an EMI noise current cancellation circuit according to an embodiment of the present application;

[0021] Figure 7 Fig. 11 is a structural schematic diagram of an EMI noise current cancellation circuit according to an embodiment of the present application;

[0022] Figure 8 Fig. 12 is a structural schematic diagram of an EMI noise current cancellation circuit according to an embodiment of the present application;

[0023] Figure 9A 、 Figure 9B 、 Figure 9C Fig. 13 is a structural schematic diagram of an EMI noise current cancellation circuit according to an embodiment of the present application;

[0024] Figure 10A 、 10B Fig. 14 is a structural schematic diagram of an EMI noise current cancellation circuit according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0026] In the description of the present application, it needs to be understood that the terms "first", "second" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance. In the description of the present application, it needs to be explained that, unless otherwise explicitly specified and limited, "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, the process, method, system, product or equipment including a series of steps or units is not limited to the listed steps or units, but optionally also includes the steps or units not listed, or optionally also includes other steps or units inherent to these processes, methods, products or equipment. The specific meaning of the above terms in the present application can be understood by the person skilled in the art according to the specific circumstances. In addition, in the description of the present application, "multiple" means two or more than two, unless otherwise specified. The association relationship of the associated objects is described, which means that there can be three relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0027] The present application will be described in detail below in conjunction with specific embodiments.

[0028] It should be noted that the information (including but not limited to user device information, user personal information, etc.), data (including but not limited to data for analysis, stored data, displayed data, etc.) and signals involved in the embodiments of the present application are all authorized by the user or fully authorized by all parties, and the collection, use and processing of related data need to comply with relevant laws, regulations and standards of relevant countries and regions. For example, the features, information and data involved in the present specification are obtained under sufficient authorization.

[0029] In an air conditioning system, because the motor control adopts PWM pulse width modulation, the parasitic capacitance between the motor winding and the shell can form a current path at high frequency, so that high-frequency noise is coupled to the grounding system through the parasitic capacitance, generating a conductive electromagnetic interference mainly in the form of common-mode current. Electromagnetic interference (EMI) is mainly concentrated in the low frequency band (such as tens of kilohertz to hundreds of kilohertz). In order to meet the relevant requirements, an EMI filter needs to be used to reduce the EMI interference current flowing from the air conditioning equipment to the power supply.

[0030] Traditional EMI filter relies on common mode inductance and capacitance elements to achieve filtering function. Common mode inductance is mainly composed of magnetic core and winding. In order to achieve EMI filtering effect, especially in low frequency band, common mode inductance with high inductance is needed, so the number of turns of the inductance winding will be more and the magnetic core will be larger, which will result in larger volume and weight of the common mode inductance, and higher cost. At the same time, in the large power air conditioning system, the common mode inductance with large inductance will generate more heat in the working process, which needs effective heat dissipation measures. This further increases the complexity and volume of the air conditioning system.

[0031] Based on the above problems, the present application provides an EMI noise current cancellation circuit to solve. In one embodiment, as shown in Figure 1 Figure 1 is a schematic diagram of an EMI noise current cancellation circuit provided by an embodiment of the present application. The circuit includes a current detection module 101, a passive filter module 102, a noise module 103, and a current cancellation module 104.

[0032] The three-phase input terminals of the current detection module 101 are connected to the three-phase output terminals of the power grid 100, the three-phase output terminals of the current detection module 101 are connected to the three-phase input terminals of the passive filter module 102, and the three-phase output terminals of the passive filter module 102 are connected to the three-phase input terminals of the noise module 103.

[0033] Specifically, in this embodiment, the three-phase output terminals of the power grid 100 include L1, L2 and L3, the three-phase input terminals of the noise module 103 include L1', L2' and L3', and the three-phase output terminals of the power grid 100 and the three-phase input terminals of the noise module 103 include L1', L2' and L3' are electrically connected.

[0034] The noise module 103 is used to work according to the working voltage provided by the power grid 100. The noise module 103 can be any kind of electronic device that works with working voltage, such as air conditioning equipment, refrigerator equipment, freezer equipment, etc.

[0035] The passive filter module 102 filters the noise current generated by the noise module 103 when it works to obtain the noise current. The passive filter module 102 is composed of passive elements (such as resistance, capacitance, inductance, etc.), and does not rely on external power supply to work, and its main function is to filter the noise current. In this embodiment, the passive filter module 102 first attenuates the noise current to be processed in the EMI noise current cancellation circuit, reducing the current amplitude of the noise current to be processed by the current cancellation module 104.

[0036] The detection end of the current offsetting module 104 is connected with the detection end of the current detecting module 101, the current offsetting module 104 detects the current value of the noise current through the current detecting module 101, and outputs the offsetting current with the same current value and opposite direction to the noise current.

[0037] The method that the current offsetting module 104 detects the current value of the noise current through the current detecting module 101 can be any one of the shunt resistance method, the Hall effect sensor method, the current transformer method or the current sensor, and when the current value of the noise current is acquired based on each method, the current offsetting module 104 through the current detecting module 101 contains the required components.

[0038] The neutral end N of the current offsetting module 104 is connected with the neutral end N of the power grid, the grounding protection end PE of the current offsetting module 104 is connected with the grounding protection end PE of the power grid, and the current offsetting module 104 inputs the offsetting current into the EMI noise current offsetting circuit to offset the noise current. The neutral end (Neutral) of the power grid 100 is an important reference point in the power system, which is usually connected with the grounding protection end, used to provide the path of current return, balance the three-phase load, and ensure the safe and stable operation of the power system.

[0039] For example, the direction of the noise current is from the L2' end of the noise module 103 to the L2 end of the power grid 100, and the direction of the offsetting current output by the current offsetting module 104 is sequentially from the neutral end N of the current offsetting module 104, through the neutral end N (or the grounding protection end PE) of the power grid 100, sequentially through the current detecting module 101 and the passive filtering module 102, to offset the noise current in the circuit.

[0040] For another example, the direction of the noise current is from the L2 end of the power grid 100 to the L2' end of the noise module 103, and the direction of the offsetting current output by the current offsetting module 104 is sequentially from the L2 end of the power grid 100 and the neutral end N of the power grid 100 to the neutral end N of the current offsetting module 104, and from the detection end of the current offsetting module 104 to the output circuit, to offset the noise current in the circuit.

[0041] The EMI noise current cancellation circuit provided in the application comprises a current detection module, a passive filtering module, a noise module and a current cancellation module. The passive filtering module filters the noise current to be processed generated by the noise module during operation to obtain a noise current. The current cancellation module detects the current value of the noise current through the current detection module and outputs a cancellation current with the same current value and opposite direction to the noise current. The cancellation current is further input into the EMI noise current cancellation circuit to cancel the noise current. In other words, the current cancellation module and the current detection module comprising a common-mode inductor with low inductance are used to eliminate the EMI noise current, and the noise current suppression is no longer dependent on the large inductance common-mode inductor, so that the volume, weight, heat and cost of the common-mode inductor in the current cancellation module and the current detection module for realizing the EMI filtering and noise reduction function can be reduced. The noise reduction effect of the EMI circuit is good through the preliminary filtering processing by the passive filtering module and the further noise reduction processing by the current cancellation module.

[0042] As shown in Figure 2 , Figure 2 is a structural schematic diagram of an EMI noise current cancellation circuit provided in the application. The circuit comprises a current detection module 201, a passive filtering module 202, a noise module 203 and a current cancellation module (not shown in the figure). The connection structure of the above modules is shown in Figure 1 , which will not be described here.

[0043] In the embodiment, the current cancellation module comprises an amplification push-pull unit 2041, a resistance adjustment unit 2042, a direct current isolation unit 2044, an auxiliary power supply 2045 and a suppression unit 2043.

[0044] The power supply end of the amplification push-pull unit 2041 is connected with the output end of the auxiliary power supply 2045, and the amplification push-pull unit 2041 works based on the working voltage output by the auxiliary power supply 2045. For example, the auxiliary power supply 2045 provides a working voltage of 12V to the amplification push-pull unit 2041.

[0045] The detection end of the amplification push-pull unit 2041 is connected with the detection end of the current detection module 201, and the amplification end of the amplification push-pull unit 2041 is connected with the first end of the resistance adjustment unit 2042. The amplification push-pull unit 2041 outputs an amplification voltage to the resistance adjustment unit 2042 based on the noise current detected by the current detection module 201. The voltage value of the amplification voltage is obtained according to the current value of the noise current and the resistance value of the amplification push-pull unit 2041.

[0046] The second end of the resistance adjusting unit 2042 is connected with the ground protection end of the power grid 200, and the resistance adjusting unit 2042 outputs a counter current to the ground protection end of the power grid 200 based on the amplified voltage. The resistance value of the resistance adjusting unit 2042 is adjusted as required, so that the current value of the counter current obtained according to the voltage value of the amplified voltage and the resistance value of the resistance adjusting unit 2042 is the same as the current value of the noise current. For example, Ic = V0 / R0 = I0, where Ic is the current value of the counter current, V0 is the voltage value of the amplified voltage, R0 is the resistance value of the resistance adjusting unit 2042, and I0 is the current value of the noise current.

[0047] The three-phase input ends of the suppression unit 2043 are connected with the three-phase input ends of the current detection module 201 and the three-phase output ends of the power grid 200 respectively, the three-phase output ends of the suppression unit 2043 are connected with the first ends of the direct-current blocking unit 2044 respectively, the second end of the direct-current blocking unit 20442 is connected with the input end of the amplification push-pull unit 2041, and the suppression unit 2043 and the direct-current blocking unit 2044 input the counter current into the EMI noise current cancellation circuit. The suppression unit 2043 functions to pass through and block the counter current, provides a low-impedance path between the EMI noise current cancellation circuit and the three-phase output ends of the power grid 200, and is also used to eliminate differential mode noise in the noise current. The direct-current blocking unit 2044 is used to pass through and block the counter current.

[0048] The current cancellation module and the current detection module including a common-mode inductance with a low inductance value are used to eliminate the EMI noise current in the application, and the suppression of the noise current is no longer dependent on a large inductance common-mode inductance. The volume, weight, heat generation and cost of the common-mode inductance in the current cancellation module and the current detection module for realizing the EMI filtering and noise reduction function can be reduced. The noise reduction effect of the EMI circuit is good through the preliminary filtering processing of the passive filtering module and the further noise reduction processing of the current cancellation module.

[0049] Based on Figure 2 The embodiments shown in the drawings are provided Figure 3 , Figure 3 is a structural schematic diagram of an EMI noise current cancellation circuit provided by the embodiments of the application. In the embodiment, the current cancellation module further includes a feedback unit 2046.

[0050] The input end of the feedback unit 2046 is connected with the output end of the resistance adjusting unit 2042, the output end of the feedback unit 2046 is connected with the input end of the auxiliary power supply 2045, and the feedback unit 2046 inputs the low-frequency component of the counter current into the auxiliary power supply.

[0051] In the embodiment, the noise current to be processed generated by the EMI noise current cancellation circuit has a large low frequency component, and the EMI standard of the load system only limits the EMI noise above a certain frequency band, for example, the air conditioning system only limits the EMI noise above 150 kHz. Therefore, the low frequency component of the noise current to be processed does not need to be cancelled. The application feeds back the low frequency component of the cancellation current to the auxiliary power supply through the feedback unit, so that the cancellation current mainly includes the high frequency common mode current component above 150 kHz, thereby reducing the power consumption of the auxiliary power supply.

[0052] Based on Figure 2 The embodiments shown in the drawings are provided Figure 4 , Figure 4 is a structural schematic diagram of an EMI noise current cancellation circuit provided by the embodiment of the application.

[0053] In the embodiment, the suppression unit 2043 includes a first capacitor C1, a second capacitor C2, and a third capacitor C3.

[0054] The first end of the first capacitor C1, the first end of the second capacitor C2, and the first end of the third capacitor C3 are connected to the three-phase input end of the current detection module 201, and the second end of the first capacitor C1, the second end of the second capacitor C2, and the second end of the third capacitor C3 are respectively connected to the neutral end of the power grid 200.

[0055] The amplification push-pull unit 2041 includes an operational amplifier OP1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a fourth capacitor C4, a first diode D1, a second diode D2, a first transistor Q1, and a second transistor Q2.

[0056] The fourth capacitor C4 and the first end are respectively connected to the first end of the first resistor R1, the first detection end of the current detection module 201, and the second end of the resistance adjustment unit 2042, and the second end of the fourth capacitor C4 is respectively connected to the second end of the first resistor R1, the second detection end of the current detection module, and the non-inverting input end of the operational amplifier OP1. In the embodiment, the first end of the fourth capacitor C4 is connected to the first end of the eighth resistor R8.

[0057] The first end of the second resistor R2 is respectively connected to the collector of the first transistor Q1, the positive electrode of the auxiliary power supply 2045, and the positive end of the operational amplifier OP1, and the second end of the second resistor R2 is respectively connected to the base of the first transistor Q1 and the anode of the first diode D1. The cathode of the first diode D1 is respectively connected to the first end of the third resistor R3.

[0058] The first end of the fourth resistor R4 is connected with the second end of the third resistor R3 and the output end of the operational amplifier OP1 respectively, the second end of the fourth resistor R4 is connected with the anode of the second diode D2, the anode of the second diode D2 is connected with the first end of the fifth resistor R5 and the base of the second triode Q2 respectively, the second end of the fifth resistor R5 is connected with the collector of the second triode Q2, the negative end of the operational amplifier OP1 and the negative electrode of the auxiliary power supply 2045 respectively;

[0059] The first end of the sixth resistor R6 is connected with the emitter of the first triode Q1, the first end of the resistor adjusting unit 2042, the inverting input end of the operational amplifier OP1 and the first end of the seventh resistor R7 respectively, the second end of the seventh resistor R7 is connected with the emitter of the second triode Q2.

[0060] The direct-current blocking unit 2044 comprises the fifth capacitor C5, the sixth capacitor C6 and the seventh capacitor C7.

[0061] The first end of the fifth capacitor C5 is connected with the three-phase output end of the suppression unit 2043, the second end of the fifth capacitor C5 is connected with the first end of the sixth capacitor C6 and the first end of the seventh capacitor C7 respectively, the second end of the sixth capacitor C6 is connected with the input end of the push-pull amplification unit 2041, and the second end of the seventh capacitor C7 is connected with the input end of the push-pull amplification unit 2041.

[0062] In the embodiment, the first end of the fifth capacitor C5 is connected with the second end of the first capacitor C1, the second end of the second capacitor C2 and the second end of the third capacitor C3 respectively.

[0063] The resistor adjusting unit 2042 comprises the eighth resistor R8 and the eighth capacitor C8.

[0064] The first end of the eighth resistor R8 is connected with the amplification end of the push-pull amplification unit 2041, the second end of the eighth resistor R8 is connected with the eighth capacitor C8, and the second end of the eighth capacitor C8 is connected with the ground protection end of the power grid 200.

[0065] The feedback unit 2046 comprises the ninth resistor R9.

[0066] The first end of the ninth resistor R9 is connected with the output end of the resistor adjusting unit 2042, and the output end of the ninth resistor R9 is connected with the input end of the auxiliary power supply 2045.

[0067] In the embodiment, the first end of the ninth resistor R9 is connected with the first end of the eighth resistor R8.

[0068] Based on the structural diagram provided in this embodiment, taking the case where the EMI noise current flows from the L2 terminal of the noise module 203 out of the L2 line to the L2 terminal of the power grid 200 as an example (the cases of L1' and L3' are the same and will not be described again). The noise current IL2' to be processed is first partially filtered out by the passive filter 201 to obtain the noise current Ict flowing through the current detection module 201. Since the turns ratio of the current detection module 201 is n:n:n:1, the induced current Ir1 = n*Ict received by the current transformer is amplified. The function of the fourth capacitor C4 is to absorb a portion of the high-frequency interference current, so that the detection current flowing through the first resistor R1 is not easily affected by external interference.

[0069] The second end of the first resistor R1 is connected to the non-inverting input of the operational amplifier OP1. Taking the second end of the first resistor R1 as the zero potential reference point, then VA = 0V and VB = Ir1*R1 (the resistance value of the first resistor R1).

[0070] The power amplification unit is used for power amplification. The inverting input of op-amp OP1 is connected to the second terminal of the eighth resistor R8, and the first terminal of the first resistor R1 is connected to the first terminal of the eighth resistor R8. Due to the virtual short characteristic of the op-amp, the inverting input terminal, i.e., the second terminal of the eighth resistor R8, has VC = VA = 0V. Since the voltage VB at the right end of R9 is Ir1 * R1, the offset current flowing to the grounding protection terminal PE can be calculated as Ic15 = VB / R8 = n * Ict * R1 / R8.

[0071] The cancelling current flows into the power grid through the second capacitor C2 in the suppression unit 2043, the fifth capacitor C5 and the sixth capacitor C6 in the DC blocking unit 2044, the first transistor Q1 (acting as a push-pull transistor), the sixth resistor R6 and the ninth resistor R9 (acting as current-limiting resistors), and the eighth capacitor C8 (acting as a DC blocking capacitor), via the protective ground. The direction of the cancelling current is opposite to that of the noise current.

[0072] Furthermore, in the EMI noise current cancellation circuit, the numerical relationship between multiple components is set as n*R1 / R8 = 1, which yields Ic15 = VB / R8 = n*Ict*R1 / R8 = Ict, meaning the cancellation current value and the noise current value are the same. The turns ratio of the current detection module 201 is n:n:n:1, R1 is the resistance value of the first resistor R1 in the push-pull amplification unit, and R8 is the resistance value of the eighth resistor R8 in the resistance adjustment unit.

[0073] like Figure 5 As shown, Figure 5 This is a third schematic diagram of an EMI noise current cancellation circuit provided in this application embodiment. The circuit includes: a current detection module 301, a passive filter module 302, a noise module 303, and a current cancellation module 304. The connection structure of the above modules is shown in [reference needed]. Figure 1As shown, details are not described here.

[0074] In this embodiment, the current detection module 301 comprises a current transformer CT1.

[0075] The first end of the current transformer CT1 is connected with the three-phase output end of the power grid 200, the second end of the current transformer CT1 is connected with the three-phase input end of the passive filter module 302, and the third end of the current transformer CT1 is connected with the detection end of the current cancellation unit 304. The current transformer CT is an electromagnetic device that can convert a large current into a small current output proportional to it, thereby facilitating measurement. The current cancellation module can obtain the current value of the noise current in the EMI noise current cancellation circuit by measuring the small current output by the current transformer or the voltage signal thereof.

[0076] The current cancellation module and the current detection module comprising a low inductance common mode inductor used in the present application eliminate EMI noise current, no longer rely on large inductance common mode inductor to achieve noise current suppression, can reduce the volume, weight, heat and cost of the common mode inductor in the current cancellation module and the current detection module for realizing EMI filter noise reduction function, through the preliminary filtering processing of the passive filter module, and further through the noise reduction processing of the current cancellation module, the noise reduction effect of the EMI circuit is better.

[0077] As shown in Figure 6 , the structure of the EMI noise current cancellation circuit provided by the embodiment of the present application is shown in Figure 6 , which comprises a current detection module 401, a passive filter module 402, a noise module 403, and a current cancellation module 404. The connection structure of the above-mentioned multiple modules is shown in Figure 1 , details are not described here.

[0078] The current detection module 402 comprises a first filter unit 4021, a second filter unit 4042, and a third filter unit 4023.

[0079] The three-phase input end of the third filter unit 4023 is connected with the three-phase output end of the current detection module 401.

[0080] The three-phase output end of the third filter unit is respectively connected with the three-phase input end of the noise module, the three-phase input end of the first filter unit, and the three-phase input end of the second filter unit.

[0081] The three-phase output end of the first filter unit 4041 is respectively connected with the three-phase output end of the second filter unit 4042 and the ground protection line of the power grid 400.

[0082] The first filter unit 4041 filters the differential mode noise in the noise current to be processed, and the third filter unit 4043 and the second filter unit 4022 filter the common mode noise in the noise current to be processed, to obtain the noise current. Taking the case that the EMI noise current flows out of the L2 line from the L2 end of the noise module 403 to the L2 end of the power grid 200 as an example, the noise current to be processed is filtered by the first filter unit 4041 to filter out the differential mode noise, and is filtered by the third filter unit 4043 and the second filter unit 4022 to filter out the common mode noise.

[0083] The current cancellation module and the current detection module including the common mode inductance with a low inductance value are used to eliminate the EMI noise current in the application, and the noise current suppression is no longer dependent on the large inductance common mode inductance, so that the volume, weight, heat, and cost of the common mode inductance in the current cancellation module and the current detection module for realizing the EMI filtering and noise reduction function can be reduced. The preliminary filtering processing is performed by the passive filtering module, and further noise reduction processing is performed by the current cancellation module, so that the noise reduction effect of the EMI circuit is better.

[0084] Based on Figure 6 Please see Figure 7 as shown in the drawings, Figure 7 is a structural schematic diagram of an EMI noise current cancellation circuit provided by an embodiment of the application.

[0085] The third filter unit 4023 includes a common mode choke Lcm.

[0086] The three-phase input end of the common mode choke Lcm is connected with the three-phase output end of the current detection module 401, and the three-phase output end of the common mode choke Lcm is connected with the three-phase input end of the noise module 403. The common mode choke is an electronic element used for suppressing common mode interference. It is mainly composed of a winding and a magnetic core, and is used to reduce the common mode noise in the circuit without affecting the differential mode signal.

[0087] The first filter unit 4021 includes a ninth capacitor C9, a tenth capacitor C10, an eleventh capacitor C11, and a twelfth capacitor C12.

[0088] The three-phase input end of the noise module 403 is connected with the first end of the ninth capacitor C9, the first end of the tenth capacitor C10, and the first end of the twelfth capacitor C12 respectively, the second end of the ninth capacitor C9, the second end of the tenth capacitor C10, and the second end of the twelfth capacitor C12 are connected with the eleventh capacitor C11 respectively, and the second end of the eleventh capacitor C11 is connected with the ground protection end of the power grid.

[0089] The second filter unit 4022 includes a thirteenth capacitor C13, a fourteenth capacitor C14, and a fifteenth capacitor C15.

[0090] The first end of the thirteenth capacitor C13, the first end of the fourteenth capacitor C14, and the first end of the fifteenth capacitor C15 are connected to the three-phase input end of the noise module 403, and the second end of the thirteenth capacitor C13, the second end of the fourteenth capacitor C14, and the negative electrode of the fifteenth capacitor C15 are connected to the ground protection line of the power grid 400.

[0091] Specifically, the noise current to be processed in the EMI noise current cancellation circuit is filtered out by the first filter unit composed of Lcm and the thirteenth capacitor C13, the fourteenth capacitor C14, and the fifteenth capacitor C15, and the current cancellation module 304, and the differential mode noise is filtered out by the passive elements ninth capacitor C9, tenth capacitor C10, eleventh capacitor C11, and twelfth capacitor C12.

[0092] Taking the case that the EMI noise current flows out of the L2 end of the noise module 403 to the L2 end of the power grid 200 through the L2 line as an example, the common mode current IL2' is first filtered out by the common mode choke Lcm and the thirteenth capacitor C13, and the passive filtered current Ic13 flows through the thirteenth capacitor C13, and the current Ict that is not passively filtered flows through the current detection module 401.

[0093] Based on Figure 7 the embodiment shown in the accompanying drawings, please refer to Figure 8 the embodiment shown in the accompanying drawings, Figure 8 is a structural schematic diagram of an EMI noise current cancellation circuit provided by an embodiment of the present application. The components included in the current cancellation module 404 and the connection structure between the plurality of components are described with reference to Figure 4 the embodiment shown in the accompanying drawings, the components included in the current detection module 301 and the connection structure between the plurality of components are described with reference to Figure 5 the embodiment shown in the accompanying drawings.

[0094] In the embodiment, the first end of the first capacitor C1, the first end of the second capacitor C2, and the first end of the third capacitor C3 are connected to the first end of the mutual inductor CT1. The third end of the mutual inductor CT1 is connected to the first end and the second end of the fourth capacitor C1 and the first end and the second end of the first resistor R1. The second end of the mutual inductor CT1 is connected to the three-phase input end of the common mode choke Lcm.

[0095] In the embodiment, the common-mode noise of the noise current to be processed generated by the noise module 403 is filtered by the passive filter composed of the mutual inductor Lcm and the thirteenth capacitor C13, the fourteenth capacitor C14, the fifteenth capacitor C15, and the current cancellation module 401, and the differential-mode noise of the noise current to be processed is filtered by the passive elements, i.e., the first capacitor C1, the second capacitor C2, the third capacitor C3, the ninth capacitor C9, the tenth capacitor C10, the eleventh capacitor C11, and the twelfth capacitor C12. The first capacitor C1, the second capacitor C2, and the third capacitor C3 also function as a common-mode choke, and provide a low-impedance path between the L line of the power grid 400 and the current cancellation module 401.

[0096] The common-mode noise is the main component of the EMI noise current, and the noise current flows between the three-phase power grid and the EMI noise source (the noise module). As can be known from the definition of the common-mode current, the common-mode noise of the noise current flowing through each phase line is the same.

[0097] Taking the case that the EMI noise current flows out of the L2 line from the L2 end of the noise module 403 to the L2 end of the power grid 400 as an example, the common-mode current IL2' is first filtered by the common-mode choke Lcm and the thirteenth capacitor C13, and the filtered current Ic13 flows through the thirteenth capacitor C13. The noise current Ict that is not filtered flows through the current transformer CT1.

[0098] The turns ratio of the current transformer CT1 is n:n:n:1, and the induced current Ir1=n*Ict is generated on the detection coil of the transformer. The fourth capacitor C4 functions to absorb a part of the interference current with a very high frequency, so that the detection current flowing through the first resistor R1 is not easily affected by external interference.

[0099] The second end of the first resistor R1 is connected to the non-inverting input terminal of the operational amplifier OP1, and the second end of the first resistor R1 is taken as the zero potential reference point. Therefore, VA=0V, and VB=Ir1*R1 (R1 is the resistance value of the first resistor R1). The second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the first triode Q1, the seventh resistor R7, and the second triode Q2 constitute a push-pull unit for power amplification.

[0100] The eighth resistor R8 is a current control resistor, the inverting input terminal of the operational amplifier OP1 is connected to the second end of the eighth resistor R8, and VB is connected to the first end of the eighth resistor R8. As can be known from the virtual short characteristic of the operational amplifier, the voltage VC at the inverting input terminal, i.e., the second end of the eighth resistor R8, is VA=0V. Since the voltage VB at the first end of the eighth resistor R8 is Ir1*R1, the cancellation current Ic15 flowing to the protective earth PE through the blocking capacitor C8 can be calculated as Ic15=VB / R8=n*Ict*R1 / R8.

[0101] The cancellation current Ic15 flows into the power grid 400 through the second capacitor C2, the DC blocking capacitor C5, the DC blocking capacitor C6, the push-pull transistor Q1, the current limiting resistor R6, the current control resistor R8, the DC blocking capacitor C8 in turn and flows out from the L2 end of the three-phase output end in the power grid to cancel the noise current Ict. The circuit is set to have a numerical relationship n*R1 / R8=1, and Ic15=Ict can be controlled. Since the CT1 and the Lcm have high impedance relative to the power grid, the cancellation current Ic15 flows into the power grid completely.

[0102] Taking the EMI noise current flowing from the L2 end of the power grid 400 to the L2 end of the noise module 403 as an example, the turns ratio of the current transformer CT1 is n:n:n:1, and the induced current Ir1' on the detection coil of the current transformer is n*Ict'. Taking the first end of the first resistor R1 as a zero potential reference point, then VA=Ir1'*R1 and VB=0V. According to the virtual short characteristic of the operational amplifier, the voltage VC at the eighth resistor R8 is 0V. Since the second end voltage of the eighth resistor R8 is VA=Ir1'*R1, the cancellation current Ic15' flowing to the protective earth PE through the DC blocking capacitor C8 can be calculated as Ic15'=VA / R8=n*Ict*R1 / R8.

[0103] The cancellation current Ic15 flows into the power grid 400 through the second capacitor C2, the DC blocking capacitor C5, the DC blocking capacitor C6, the push-pull transistor Q1, the current limiting resistor R6, the current control resistor R8, the DC blocking capacitor C8 in turn and flows out from the L2 end of the three-phase output end in the power grid to cancel the noise current Ict. The circuit is set to have a numerical relationship n*R1 / R8=1, and Ic15=Ict can be controlled. Since the CT1 and the Lcm have high impedance relative to the power grid, the cancellation current Ic15 flows into the power grid completely.

[0104] The EMI noise current cancellation circuit provided in the application comprises a current detection module, a passive filtering module, a noise module and a current cancellation module. The passive filtering module performs filtering processing on the noise current generated when the noise module works to obtain a noise current, the current cancellation module detects the current value of the noise current through the current detection module, and outputs a cancellation current with the same current value and opposite direction to the noise current, and further inputs the cancellation current into the EMI noise current cancellation circuit to cancel the noise current. In other words, the current cancellation module and the current detection module comprising a common-mode inductor with low inductance are used to eliminate the EMI noise current, and the noise current suppression is no longer dependent on the large inductance common-mode inductor, so that the volume, weight, heat and cost of the common-mode inductor in the current cancellation module and the current detection module for realizing the EMI filtering and noise reduction function can be reduced. The noise reduction effect of the EMI circuit is good through the preliminary filtering processing by the passive filtering module and the further noise reduction processing by the current cancellation module.

[0105] When the neutral (N) line and one of the live (L) lines of the three-phase output are reversed in an EMI noise current cancellation circuit, a high voltage of 220V (or other high voltage values) will exist between the live (L) line of the three-phase output and the protective ground. This high voltage generates a large leakage current through the DC blocking capacitor, potentially leading to an electric shock hazard. To avoid this risk, this application proposes an EMI noise current cancellation circuit that can detect and protect against reversed neutral (N) line and live (L) line connections.

[0106] In one embodiment, the EMI noise current cancellation circuit provided in this application includes a current detection module, a passive filter module, a noise module, a current cancellation module, and also includes a voltage detection module and a fault disconnection module.

[0107] The detection terminal of the voltage detection module is connected to the three-phase output terminal of the power grid, or to the neutral terminal of the power grid.

[0108] The control terminal of the voltage detection module is connected to the control terminal of the fault disconnection module, the first terminal of the fault separation module is connected to the current cancellation module, and the second terminal of the fault separation module is connected to the neutral terminal of the power grid.

[0109] When the voltage detection module detects that the target voltage value meets the preset conditions, the EMI noise current cancellation circuit is separated from the current cancellation module based on the fault disconnection module.

[0110] The target voltage is the voltage on the N line of the neutral terminal of the power grid, or it can be the voltage on one of the L lines of the three-phase output terminals of the power grid. The preset condition can be understood as indicating that when the target voltage exceeds the voltage threshold, it means that the N line of the neutral terminal and the L line of the three-phase output terminals are reversed.

[0111] The voltage detection module detects that the target voltage value meets the preset conditions. Based on the fault disconnection module, the current cancellation module is separated from the EMI noise current cancellation circuit. The separation method is to stop the operation of the DC blocking capacitor in the control current cancellation module.

[0112] Based on this embodiment, the EMI noise current cancellation circuit also has the function of detecting and protecting the reverse connection of the N line of the neutral terminal and the L line of the three-phase output terminal. When the reverse connection of the N line of the neutral terminal and the L line of the three-phase output terminal is detected, the DC blocking capacitor in the current cancellation module is separated in time, so as not to generate leakage current that may endanger human safety, thereby improving the working reliability of the EMI noise current cancellation circuit.

[0113] like Figure 9A As shown, Figure 9A This is a schematic diagram of an EMI noise current cancellation circuit provided in an embodiment of this application, comprising a current detection module 501, a passive filter module 502, a noise module 503, and a current cancellation module 504. The connection structure of these modules is shown in [reference needed].Figure 1 As shown, details are not described here

[0114] The first detection end of the voltage detection module 5051 is connected with the neutral line of the power grid, and the second detection end of the voltage detection module 5051 is connected with the grounding protection line of the power grid 500.

[0115] When the voltage detection module 5051 detects that the voltage value of the voltage between the neutral end N and the grounding protection end PE of the power grid 500 meets the first preset condition, the current offset module 504 is separated from the EMI noise current offset circuit based on the fault breaking module 506.

[0116] The principle is to detect the voltage between the neutral end N and the grounding protection end PE through the voltage detection module 5051. When the N line is not connected in error, the N-PE voltage is zero, and when N and L are connected in reverse, the N-PE voltage is 220V. The first preset condition is that the voltage value of the voltage between the neutral end N and the grounding protection end PE exceeds the preset safety voltage threshold. When the voltage detection module 5051 detects that the voltage value of the voltage between the neutral end N and the grounding protection end PE of the power grid 500 meets the above-mentioned first preset condition, the current offset module 504 is separated from the EMI noise current offset circuit based on the fault breaking module 506.

[0117] As shown, Figure 9B As shown, Figure 9A is a structural schematic diagram of an EMI noise current offset circuit provided by the embodiment of the present application. In the embodiment, the first detection end, the second detection end, and the third detection end of the voltage detection module 5051 are respectively connected with the three-phase output end of the power grid 500, and the fourth detection end of the voltage detection module 5051 is connected with the grounding protection line PE of the power grid 500.

[0118] When the voltage detection module 5052 detects that the voltage value of the voltage between the target output end and the neutral end N of the three-phase output end of the power grid 500 meets the second preset condition, the current offset module 504 is separated from the EMI noise current offset circuit based on the fault breaking module 506. The preset condition includes the second preset condition.

[0119] The voltage detection module 5052 respectively detects whether the L1-N voltage, the L2-N voltage, and the L3-N voltage meet the second preset condition. For example, when it is detected that the voltage value of the L1-N voltage exceeds the preset safety voltage value, it is determined that the three-phase output end L1 and the neutral end N are connected in reverse. Therefore, the voltage detection module 5052 separates the current offset module 504 from the EMI noise current offset circuit based on the fault breaking module 506.

[0120] As shown, Figure 9C As shown, Figure 9CFigure 1 is a structural schematic diagram of an EMI noise current cancellation circuit provided by an embodiment of the present application. In the embodiment, the first detection end, the second detection end, and the third detection end of the voltage detection module 501 are connected to the three-phase output end of the power grid 500.

[0121] When the voltage detection module 5053 detects that the voltage value of the voltage between the first target output end and the second target output end of the three-phase output end of the power grid 500 satisfies the third preset condition, the current cancellation module 504 is separated from the EMI noise current cancellation circuit based on the fault breaking module 500. The preset condition includes the third preset condition.

[0122] The voltage detection module 5052 respectively detects whether the L1-L2 voltage, the L2-L3 voltage, and the L1-L3 voltage satisfy the third preset condition. For example, when it is detected that the voltage value of the L1-L2 voltage is obviously lower than the preset phase voltage value, it is determined that the three-phase output end L1 and the neutral end N are connected in reverse, or the three-phase output end L2 and the neutral end N are connected in reverse. Therefore, the current cancellation module 504 is separated from the EMI noise current cancellation circuit based on the fault breaking module 506.

[0123] In one embodiment, as shown in Figure 6, Figure 10A , Figure 10A Figure 6 is a structural schematic diagram of an EMI noise current cancellation circuit provided by an embodiment of the present application. The current cancellation module includes the DC blocking unit 6044 and the suppression unit 6043. The components and connection structure of the current cancellation module are described in Figure 5, which will not be repeated here. Figure 2

[0124] The first end of the fault breaking module 6061 is connected to the output end of the suppression unit 6043, the three-phase input end of the suppression unit 6043 is connected to the three-phase output end of the power grid 600, and the second end of the fault breaking module 6061 is connected to the input end of the DC blocking unit 6044. The suppression unit 6043 and the DC blocking unit 6044 input the cancellation current into the EMI noise current cancellation circuit.

[0125] When the voltage detection module 605 detects that the voltage value of the target voltage satisfies the preset condition, the DC blocking unit 6044 is separated from the EMI noise current cancellation circuit based on the fault breaking module 6061.

[0126] In one embodiment, as shown in Figure 6, Figure 10B , Figure 10B Figure 6 is a structural schematic diagram of an EMI noise current cancellation circuit provided by an embodiment of the present application. The current cancellation module 6062 includes the DC blocking unit 6044 and the push-pull amplification unit 6041. The components and connection structure of the current cancellation module are described in Figure 5, which will not be repeated here. Figure 2

[0127] ​​The first end of the fault breaking module 6062 is connected with the output end of the direct current isolation unit 6044, and the first end of the fault breaking module 6062 is connected with the input end of the amplification and pushover unit 6041.

[0128] The current offset module obtains an offset current based on the amplification and pushover unit 6041, and inputs the offset current into the EMI noise current offset circuit based on the direct current isolation unit 6044,

[0129] When the voltage detection module 605 detects that the voltage value of the target voltage meets the preset condition, the fault breaking module 6062 is used to separate the isolation unit from the EMI noise current offset circuit.

[0130] Based on the embodiment, the EMI noise current offset circuit further has the function of detecting that the N line of the neutral end and the L line of the three-phase output end are connected in reverse and providing protection, and when it is detected that the N line of the neutral end and the L line of the three-phase output end are connected in reverse, the direct current isolation capacitor in the current offset module is separated in time, so that the leakage current that may endanger human safety is not generated, and the working reliability of the EMI noise current offset circuit is improved.

[0131] In one embodiment, the application also provides an air conditioning system, which comprises the EMI noise current offset circuit according to any one of Figures 1 to 10B In the air conditioning system provided in the embodiment, the current offset module and the current detection module including the common-mode inductance with a low inductance are used to eliminate the EMI noise current, and the noise current suppression is no longer dependent on the large inductance common-mode inductance, so that the volume, weight, heat generation and cost of the common-mode inductance in the current offset module and the current detection module for realizing the EMI filtering and noise reduction function can be reduced, the preliminary filtering processing is performed through the passive filtering module, and further noise reduction processing is performed through the current offset module, so that the noise reduction effect of the EMI circuit is better.

[0132] It should be noted that the EMI noise current offset circuit provided in the above embodiments includes a plurality of modules, which are only exemplified by the division of the above functional modules, and in actual application, the above functions can be completed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above, which is not limited here.

[0133] The above-mentioned embodiment serial numbers are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0134] The technical features of the above-described embodiments can be combined arbitrarily, and in order to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the description.

[0135] The above descriptions are only the preferred embodiment of the application, of course, cannot be used to limit the scope of the application, thus the equivalent variations made according to the claims of the application, still belongs to the scope covered by the application.

Claims

1. An EMI noise current cancellation circuit, characterized in that, The circuit includes: Current detection module, passive filter module, noise module, current cancellation module; The three-phase input terminals of the current detection module are respectively connected to the three-phase output terminals of the power grid. The three-phase output terminals of the current detection module are connected to the three-phase input terminals of the passive filter module. The three-phase output terminals of the passive filter module are connected to the three-phase input terminals of the noise module. The noise module is used to operate according to the working voltage provided by the power grid. The passive filtering module filters the noise current generated by the noise module during operation to obtain the noise current. The detection terminal of the current cancellation module is connected to the detection terminal of the current detection module. The current cancellation module detects the current value of the noise current through the current detection module, and outputs a cancellation current with the same current value but opposite direction to the noise current. The neutral terminal of the current cancellation module is connected to the neutral terminal of the power grid, and the ground protection terminal of the current cancellation module is connected to the ground protection terminal of the power grid. The current cancellation module inputs the cancellation current into the EMI noise current cancellation circuit to cancel the noise current.

2. The EMI noise current cancellation circuit according to claim 1, characterized in that, The current cancellation module includes: an amplification push-pull unit, a resistance adjustment unit, a DC blocking unit, an auxiliary power supply, and a suppression unit; The power supply terminal of the amplification push-pull unit is connected to the output terminal of the auxiliary power supply, and the amplification push-pull unit operates based on the working voltage output by the auxiliary power supply. The detection terminal of the amplification push-pull unit is connected to the detection terminal of the current detection module, and the amplification terminal of the amplification push-pull unit is connected to the first terminal of the resistance adjustment unit. The amplification push-pull unit outputs an amplified voltage to the resistance adjustment unit based on the noise current detected by the current detection module. The second end of the resistor adjustment unit is connected to the grounding protection terminal of the power grid, and the resistor adjustment unit outputs the offset current to the grounding protection terminal of the power grid based on the amplified voltage; The three-phase input terminals of the suppression unit are connected to the three-phase input terminals of the current detection module and the three-phase output terminals of the power grid, respectively. The three-phase output terminals of the suppression unit are connected to the first terminal of the DC blocking unit, and the second terminal of the DC blocking unit is connected to the input terminal of the amplification push-pull unit. The suppression unit and the DC blocking unit input the cancellation current to the EMI noise current cancellation circuit.

3. The EMI noise current cancellation circuit according to claim 2, characterized in that, The current cancellation module further includes: a feedback unit; The input terminal of the feedback unit is connected to the output terminal of the resistor adjustment unit, and the output terminal of the feedback unit is connected to the input terminal of the auxiliary power supply. The feedback unit inputs the low-frequency component of the offset current to the auxiliary power supply.

4. The EMI noise current cancellation circuit according to claim 2, characterized in that, The suppression unit includes a first capacitor, a second capacitor, and a third capacitor; The first terminal of the first capacitor, the first terminal of the second capacitor, and the first terminal of the third capacitor are connected to the three-phase input terminal of the current detection module, and the second terminals of the first capacitor, the second capacitor, and the third capacitor are respectively connected to the neutral terminal of the power grid.

5. The EMI noise current cancellation circuit according to claim 2, characterized in that, The amplification push-pull unit includes: an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a fourth capacitor, a first diode, a second diode, a first transistor, and a second transistor; The fourth capacitor and its first terminal are respectively connected to the first terminal of the first resistor, the first detection terminal of the current detection module, and the second terminal of the resistor adjustment unit. The second terminal of the fourth capacitor is respectively connected to the second terminal of the first resistor, the second detection terminal of the current detection module, and the non-inverting input terminal of the operational amplifier. The first end of the second resistor is connected to the collector of the first transistor, the positive terminal of the auxiliary power supply, and the positive terminal of the operational amplifier, respectively. The second end of the second resistor is connected to the base of the first transistor and the positive terminal of the first diode, respectively. The negative terminal of the first diode is connected to the first end of the third resistor. The first end of the fourth resistor is connected to the second end of the third resistor and the output end of the operational amplifier. The second end of the fourth resistor is connected to the anode of the second diode. The anode of the second diode is connected to the first end of the fifth resistor and the base of the second transistor. The second end of the fifth resistor is connected to the collector of the second transistor, the negative terminal of the operational amplifier, and the negative terminal of the auxiliary power supply. The first end of the sixth resistor is connected to the emitter of the first transistor, the first end of the resistor adjustment unit, the inverting input of the operational amplifier, and the first end of the seventh resistor, respectively. The second end of the seventh resistor is connected to the emitter of the second transistor.

6. The EMI noise current cancellation circuit according to claim 2, characterized in that, The DC blocking unit includes: a fifth capacitor, a sixth capacitor, and a seventh capacitor; The first terminal of the fifth capacitor is connected to the three-phase output terminal of the suppression unit. The second terminal of the fifth capacitor is connected to the first terminal of the sixth capacitor and the first terminal of the seventh capacitor. The second terminal of the sixth capacitor is connected to the input terminal of the push-pull amplifier unit. The second terminal of the seventh capacitor is connected to the input terminal of the push-pull amplifier unit.

7. The EMI noise current cancellation circuit according to claim 2, characterized in that, The resistance adjustment unit includes: an eighth resistor and an eighth capacitor; The first end of the eighth resistor is connected to the amplification end of the push-pull amplification unit, the second end of the eighth resistor is connected to the eighth capacitor, and the second end of the eighth capacitor is connected to the grounding protection end of the power grid.

8. The EMI noise current cancellation circuit according to claim 3, characterized in that, The feedback unit includes: a ninth resistor; The first end of the ninth resistor is connected to the output end of the resistor adjustment unit, and the output end of the ninth resistor is connected to the input end of the auxiliary power supply.

9. The EMI noise current cancellation circuit according to claim 1, characterized in that, The current detection module includes: a current transformer; The first end of the current transformer is connected to the three-phase output terminal of the power grid, the second end of the current transformer is connected to the three-phase input terminal of the passive filter module, and the third end of the current transformer is connected to the detection terminal of the current cancellation unit.

10. The EMI noise current cancellation circuit according to claim 1, characterized in that, The current detection module includes: a first filtering unit, a second filtering unit, and a third filtering unit; The three-phase input terminal of the third filtering unit is connected to the three-phase output terminal of the current detection module; The three-phase output terminals of the third filter unit are respectively connected to the three-phase input terminals of the noise module, the three-phase input terminals of the first filter unit, and the three-phase input terminals of the second filter unit; The three-phase output terminals of the first filter unit are respectively connected to the three-phase output terminals of the second filter unit and the grounding protection line of the power grid; The first filtering unit filters the differential-mode noise in the noise current to be processed, and the third filtering unit and the second filtering unit filter the common-mode noise in the noise current to be processed, to obtain the noise current.

11. The EMI noise current cancellation circuit according to claim 10, characterized in that, The third filtering unit includes: a common-mode choke; The three-phase input terminal of the common-mode choke is connected to the three-phase output terminal of the current detection module, and the three-phase output terminal of the common-mode choke is connected to the three-phase input terminal of the noise module.

12. The EMI noise current cancellation circuit according to claim 10, characterized in that, The first filtering unit includes: a ninth capacitor, a tenth capacitor, an eleventh capacitor, and a twelfth capacitor; The three-phase input terminals of the noise module are respectively connected to the first terminal of the ninth capacitor, the first terminal of the tenth capacitor, and the first terminal of the twelfth capacitor. The second terminals of the ninth capacitor, the tenth capacitor, and the twelfth capacitor are respectively connected to the eleventh capacitor. The second terminal of the eleventh capacitor is connected to the grounding protection terminal of the power grid.

13. The EMI noise current cancellation circuit according to claim 10, characterized in that, The second filter unit includes: a thirteenth capacitor, a fourteenth capacitor, and a fifteenth capacitor; The first terminal of the thirteenth capacitor, the first terminal of the fourteenth capacitor, and the first terminal of the fifteenth capacitor are respectively connected to the three-phase input terminal of the noise module, and the second terminal of the thirteenth capacitor, the second terminal of the fourteenth capacitor, and the negative terminal of the fifteenth capacitor are connected to the grounding protection line of the power grid.

14. The EMI noise current cancellation circuit according to claim 1, characterized in that, The circuit also includes a voltage detection module and a fault disconnection module; The detection terminal of the voltage detection module is connected to the three-phase output terminal of the power grid, or to the neutral terminal of the power grid. The control terminal of the voltage detection module is connected to the control terminal of the fault disconnection module, the first terminal of the fault separation module is connected to the current cancellation module, and the second terminal of the fault separation module is connected to the neutral terminal of the power grid. When the voltage detection module detects that the target voltage value meets the preset conditions, the fault disconnection module separates the EMI noise current cancellation circuit from the current cancellation module.

15. The EMI noise current cancellation circuit according to claim 14, characterized in that, The first detection terminal of the voltage detection module is connected to the neutral terminal of the power grid, and the second detection terminal of the voltage detection module is connected to the grounding protection line of the power grid. When the voltage detection module detects that the voltage value between the neutral terminal and the grounding protection terminal of the power grid meets the first preset condition, the fault disconnection module separates the EMI noise current cancellation circuit from the current cancellation module. The preset conditions include the first preset conditions.

16. The noise current cancellation circuit according to claim 14, characterized in that, The first detection terminal, the second detection terminal, and the third detection terminal of the voltage detection module are respectively connected to the three-phase output terminals of the power grid, and the fourth detection terminal of the voltage detection module is connected to the grounding protection line of the power grid. When the voltage detection module detects that the voltage value between the target output terminal and the neutral terminal in the three-phase output terminal of the power grid meets the second preset condition, the fault disconnection module separates the EMI noise current cancellation circuit from the current cancellation module. The preset conditions include the second preset conditions.

17. The noise current cancellation circuit according to claim 14, characterized in that, The first detection terminal, the second detection terminal, and the third detection terminal of the voltage detection module are respectively connected to the three-phase output terminals of the power grid; When the voltage detection module detects that the voltage value between the first target output terminal and the second target output terminal in the three-phase output terminals of the power grid meets the third preset condition, the fault disconnection module separates the EMI noise current cancellation circuit from the current cancellation module. The preset conditions include the third preset condition.

18. The EMI noise current cancellation circuit according to claim 14, characterized in that, The current cancellation module includes: a DC blocking unit and a suppression unit; The first end of the fault disconnection module is connected to the output end of the suppression unit, the three-phase input end of the suppression unit is connected to the three-phase output end of the power grid, and the second end of the fault disconnection module is connected to the input end of the DC blocking unit. The suppression unit and the DC blocking unit input the cancellation current to the EMI noise current cancellation circuit; When the voltage detection module detects that the voltage value of the target voltage meets the preset condition, the fault disconnection module separates the DC blocking unit from the EMI noise current cancellation circuit.

19. The EMI noise current cancellation circuit according to claim 14, characterized in that, The current cancellation module includes: a DC blocking unit and an amplification push-pull unit; The first end of the fault isolation module is connected to the output end of the DC blocking unit, and the first end of the fault isolation module is connected to the input end of the amplification and exemption unit. The current cancellation module obtains the cancellation current based on the amplification and exemption unit, and inputs the cancellation current into the EMI noise current cancellation circuit based on the DC blocking unit; When the voltage detection module detects that the voltage value of the target voltage meets the preset condition, the EMI noise current cancellation circuit is separated from the isolation unit based on the fault disconnection module.

20. An air conditioning system, characterized in that, The air conditioning system includes an EMI noise current cancellation circuit as described in any one of claims 1 to 19.

Images