Noise suppression circuit and air conditioning equipment

Abstract

The invention provides a noise suppression circuit and air conditioning equipment, and the noise suppression circuit comprises a first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module; the first noise module is used for working according to the input voltage; the first voltage sampling module is used for detecting a first sampling voltage signal of the first noise module and sending the first sampling voltage signal to the current compensation module through a signal end of the first voltage sampling module; the first equivalent impedance module is used for providing a first resistance signal equivalent to the resistance value of the first noise module for the current compensation module; the current compensation module is used for determining the current value of a first compensation current signal according to the voltage value of the first sampling voltage signal and the resistance value of the first resistance signal, and sending the first compensation current signal to the first noise module. According to the embodiment provided by the scheme, the noise generated when the first noise module works can be reduced.

Description

Technical Field

[0001] The present application relates to the field of circuits, and in particular to a noise suppression circuit and air conditioning equipment. Background Art

[0002] The variable frequency drive system is a system that controls the speed and torque of a motor by adjusting the frequency and voltage of the motor power supply. It is widely used in industrial automation, building air conditioning, water pumps and other applications.

[0003] In related technologies, in order to reduce the electromagnetic interference caused by the switching action of the inverter in the variable frequency drive system, it is necessary to suppress the electromagnetic interference noise generated by the power conversion device, such as using an electromagnetic interference filter to suppress the noise. However, with the increasing demand for high frequency, miniaturization and cost reduction of variable frequency drive systems, the disadvantages of the filter, such as large size, heavy weight, high cost, and high frequency bandwidth being greatly affected by magnetic sensors, have gradually become prominent. Summary of the invention

[0004] The embodiment of the present application provides a noise suppression circuit and an air conditioning device, which can reduce the noise generated by the noise source and reduce the volume, complexity and cost of the noise suppression circuit. The above technical solution is as follows:

[0005] In a first aspect, an embodiment of the present application provides a noise suppression circuit, the circuit comprising:

[0006] A first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module;

[0007] The input end of the first noise module is connected to the input end of the first voltage sampling module, the output end of the first noise module is connected to the output end of the first voltage sampling module, the input end of the first voltage sampling module is used to receive the input voltage, the output end of the first voltage sampling module is connected to the input end of the first equivalent impedance module, the output end of the first equivalent impedance module is connected to the input end of the current compensation module, the output end of the current compensation module is connected to the input end of the first noise module, and the signal end of the current compensation module is connected to the signal end of the first voltage sampling module;

[0008] The first noise module is used to work according to the input voltage;

[0009] The first voltage sampling module is used to detect the first sampled voltage signal of the first noise module, and send the first sampled voltage signal to the current compensation module through the signal terminal of the first voltage sampling module;

[0010] The first equivalent impedance module is used to provide the current compensation module with a first resistance signal equivalent to the resistance value of the first noise module;

[0011] The current compensation module is used to determine the current value of the first compensation current signal according to the voltage value of the first sampling voltage signal and the resistance value of the first resistance signal, and send the first compensation current signal to the first noise module to reduce the noise generated when the first noise module is working. The current compensation module includes a voltage source, which is used to provide a driving voltage for the current compensation module.

[0012] In a second aspect, an embodiment of the present application provides an air-conditioning device, the air-conditioning device comprising a noise suppression circuit provided by the first aspect of the embodiment of the present application or any possible implementation of the first aspect.

[0013] The noise suppression circuit provided by the embodiment of the present application includes a first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module; wherein the noise voltage generated by the first noise module is captured by the first voltage sampling module to generate a first sampled voltage signal; the first equivalent impedance module provides an equivalent impedance signal according to the working characteristics of the first noise module; then the first sampled voltage signal and the first resistance signal are transmitted to the current compensation module, and the current compensation module obtains a first compensation current signal according to the two signals, and its magnitude and direction are precisely adjusted, and can be opposite to the direction of the noise current. By injecting a current opposite to the direction of the noise current into the first noise module, the corresponding current compensation can be performed before or at the beginning of the noise generation, effectively reducing the noise generated by the first noise module. In an ideal case, the first compensation current signal and the noise current are equal in magnitude and opposite in direction, and the effects of the two can be offset to completely eliminate the noise current. Thus, the noise generated when the first noise module is working can be effectively reduced or eliminated. In addition, compared with the traditional noise suppression method that relies on current transformers for current sampling, the noise suppression circuit provided in the present application directly calculates the current value of the corresponding current compensation signal through voltage sampling and analysis of the sampled voltage signal, effectively avoiding the volume and complexity problems brought by traditional current transformers, and reducing the volume and design cost of the noise suppression circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 A first structural schematic diagram of a noise suppression circuit provided by an exemplary embodiment of the present application;

[0016] Figure 2A schematic diagram of the structure of an equivalent circuit of a noise suppression circuit provided by an exemplary embodiment of the present application;

[0017] Figure 3 A second structural schematic diagram of a noise suppression circuit provided by an exemplary embodiment of the present application;

[0018] Figure 4 A third structural schematic diagram of a noise suppression circuit provided by an exemplary embodiment of the present application;

[0019] Figure 5 A structural schematic diagram of a test circuit provided by an exemplary embodiment of the present application;

[0020] Figure 6 A structural schematic diagram of another test circuit provided by an exemplary embodiment of the present application;

[0021] Figure 7 A schematic diagram of common mode impedance characteristics provided by an exemplary embodiment of the present application;

[0022] Figure 8 A structural schematic diagram of a fitting circuit provided by an exemplary embodiment of the present application;

[0023] Fig. 9 A schematic diagram of a simplified fitting circuit provided by an exemplary embodiment of the present application;

[0024] Fig.10 A schematic diagram of a noise suppression circuit for multiple noise sources provided by an exemplary embodiment of the present application;

[0025] Fig.11 A schematic diagram of the structure of an air conditioning system provided by an exemplary embodiment of the present application;

[0026] Fig.12 A schematic diagram of a first simulation result provided for an exemplary embodiment of the present application;

[0027] Fig.13 A schematic diagram of a second simulation result provided for an exemplary embodiment of the present application;

[0028] Fig.14 A schematic diagram of a third simulation result provided for an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0030] The terms "first", "second", "third", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0031] The variable frequency drive system is a system that controls the speed and torque of a motor by adjusting the frequency and voltage of the motor power supply. It is widely used in industrial automation, building air conditioning, water pumps and other applications.

[0032] In the related art, in order to reduce the electromagnetic interference (EMI) caused by the switching action of the inverter in the variable frequency drive system, it is necessary to suppress it from both the noise source and the propagation path. In terms of the noise source, it is usually necessary to change the control strategy and modulation algorithm of the inverter to adjust the output voltage and current waveforms to reduce the intensity of EMI noise. However, changes in the control and modulation algorithms may affect the operating efficiency and stability of the power converter. Therefore, in addition to adjusting the control strategy, adding an EMI filter is also a common means of noise suppression, especially reducing noise propagation through EMI filters.

[0033] At present, EMI filters are mainly divided into three categories: passive, active and hybrid. Passive EMI filters are usually large in size, heavy in weight, high in cost and have large losses. Therefore, in the context of the increasing demand for high frequency, miniaturization and cost reduction of variable frequency drive systems, their shortcomings are gradually emerging. This has also prompted the research and application of active filters or a combination of passive and active filters to adapt to the development trend of the system. The design method of active filters usually uses current transformers (CT) or voltage transformers, but the bandwidth of CT is limited by factors such as the nonlinear characteristics of magnetic components, high-frequency parasitic capacitance, leakage inductance and equivalent series resistance. In addition, CT needs to carry normal operating current to avoid saturation, so it is large in size and high in cost. In addition, voltage transformers are also affected by magnetic characteristics and parasitic parameters, and the system bandwidth is also limited. Under high-power applications, the secondary winding of the voltage transformer needs to withstand large currents, resulting in system gain limitations. Therefore, the design of active filters needs to balance noise suppression effects, system stability, cost and volume to meet the requirements of variable frequency drive systems for high frequency, miniaturization and cost optimization.

[0034] In order to solve the above technical problems, the present application proposes a noise suppression circuit. Figure 1 , which exemplarily shows a first structural diagram of a noise suppression circuit provided in an embodiment of the present application. Figure 1 As shown, the noise suppression circuit includes:

[0035] A first noise module 11 , a first voltage sampling module 12 , a first equivalent impedance module 13 and a current compensation module 14 .

[0036] The input end of the first noise module 11 is connected to the input end of the first voltage sampling module 12, the output end of the first noise module 11 is connected to the output end of the first voltage sampling module 12, the input end of the first voltage sampling module 12 is used to receive an input voltage, the output end of the first voltage sampling module 12 is connected to the input end of the first equivalent impedance module 13, the output end of the first equivalent impedance module 13 is connected to the input end of the current compensation module 14, the output end of the current compensation module 14 is connected to the input end of the first noise module 11, and the signal end of the current compensation module 14 is connected to the signal end of the first voltage sampling module 12.

[0037] The first noise module 11 is used to work according to the input voltage.

[0038] The first voltage sampling module 12 is used to detect the first sampled voltage signal of the first noise module 11 , and send the first sampled voltage signal to the current compensation module 14 through the signal terminal of the first voltage sampling module 12 .

[0039] The first equivalent impedance module 13 is used to provide the current compensation module 14 with a first resistance signal equivalent to the resistance value of the first noise module 11 .

[0040] The current compensation module 14 includes a voltage source (not shown in the figure), which is used to provide a driving voltage for the current compensation module. The current compensation module 14 is used to determine the current value of the first compensation current signal according to the voltage value of the first sampled voltage signal and the resistance value of the first resistance signal, and send the first compensation current signal to the first noise module 11 to reduce the noise generated when the first noise module 11 is working.

[0041] In some embodiments, the first noise module 11 operates based on the input voltage, and may generate noise during operation due to electromagnetic interference, radio frequency interference, switching noise, current fluctuations, nonlinear effects, and other characteristics. This noise manifests as high-frequency voltage or current fluctuations.

[0042] In some embodiments, the first voltage sampling module 12 collects the first sampled voltage signal generated by the first noise module 11. For example, the first voltage sampling module 12 uses a specific voltage sampling circuit to sample the input voltage to obtain a first sampled voltage signal, and then the first voltage sampling module 12 sends the first sampled voltage signal to the current compensation module 14 through a signal terminal connected to the current compensation module 14.

[0043] In some embodiments, the first equivalent impedance module 13 is used to provide the resistance characteristics of the first noise module 11 to the current compensation module 14. When the first noise module 11 is working, it will produce a certain impedance characteristic. The first equivalent impedance module 13 provides an equivalent impedance signal, i.e., a first resistance signal, according to the working characteristics of the first noise module (i.e., the impedance generated by the noise), which simulates the resistance characteristics of the noise source, and transmits the first resistance signal to the current compensation module 14.

[0044] In some embodiments, the current compensation module 14 calculates the current value of the first compensation current signal based on the voltage value of the first sampled voltage signal and the resistance value of the first resistance signal, and sends the first compensation current signal to the first noise module 11 to compensate or offset the noise signal by introducing a current in the opposite direction to the current in the first noise module 11.

[0045] Next, combine Figure 2 The noise suppression circuit provided by the present application is described. Figure 2 A schematic diagram of an equivalent circuit of a noise suppression circuit provided by an exemplary embodiment of the present application is shown in FIG. Figure 2 , the noise voltage generated by the common-mode noise source is V x , when the noise suppression circuit provided by the present application is not added, due to the noise voltage V x The influence of common mode current I X The common mode current flows to the ground through the load unit in the first noise module 11. The expression of the common mode current is: Among them, Z motor is the common mode impedance between the load unit and the ground in the first noise module 11, Z p It is the equivalent parasitic impedance of the midpoint of the three-phase bridge arm in the inverter unit to the ground in the first noise module 11. These common mode currents flow through the noise detection module LISN and are detected, which may cause noise problems.

[0046] In order to suppress noise, the present application provides a noise suppression circuit, including a compensation network Z s , namely the first equivalent impedance module 13, the noise suppression circuit injects a first compensation current signal I comp To offset the common mode current I x The first compensation current signal I compThe magnitude of the noise voltage V x is proportional to, and its formula is: After the first compensation current signal is injected, it will be combined with the original common mode current I x Ideally, when I x =I comp When the current flowing through the LISN is LISN That is to say, by injecting a compensation current that is equal to and opposite to the common-mode current, the noise current can be effectively offset, thereby suppressing the common-mode noise of the system.

[0047] The noise suppression circuit provided by the embodiment of the present application includes a first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module; wherein the noise voltage generated by the first noise module is captured by the first voltage sampling module to generate a first sampled voltage signal; the first equivalent impedance module provides an equivalent impedance signal according to the working characteristics of the first noise module; then the first sampled voltage signal and the first resistance signal are transmitted to the current compensation module, and the current compensation module obtains a first compensation current signal according to the two signals, and its magnitude and direction are precisely adjusted, and can be opposite to the direction of the noise current. By injecting a current opposite to the direction of the noise current into the first noise module, the corresponding current compensation can be performed before or at the beginning of the noise generation, effectively reducing the noise generated by the first noise module. In an ideal case, the first compensation current signal and the noise current are equal in magnitude and opposite in direction, and the effects of the two can be offset to completely eliminate the noise current. Thus, the noise generated when the first noise module is working can be effectively reduced or eliminated. In addition, compared with the traditional noise suppression method that relies on current transformers for current sampling, the noise suppression circuit provided in the present application directly calculates the current value of the corresponding current compensation signal through voltage sampling and analysis of the sampled voltage signal, effectively avoiding the volume and complexity problems brought by traditional current transformers, and reducing the volume and design cost of the noise suppression circuit.

[0048] Figure 3 A second structural diagram of a noise suppression circuit provided by an exemplary embodiment of the present application is shown in FIG. Figure 3 As shown, the noise suppression circuit includes: a first noise module 31, a first voltage sampling module 32, a first equivalent impedance module 33 and a current compensation module 34. The connection relationship between each module is the same as above. Figure 1 The same, no further elaboration here.

[0049] In this embodiment, the current compensation module 34 includes: an operational amplifier unit 341 , a push-pull unit 342 , an adjustment resistor 343 and an output resistor 344 .

[0050] The inverting input terminal of the operational amplifier unit 341 is connected to the output terminal of the first equivalent impedance module 33, the inverting input terminal of the operational amplifier unit 341 is connected to the ground line, the output terminal of the operational amplifier unit 341 is connected to the input terminal of the push-pull unit 342, the output terminal of the push-pull unit 342 is connected to the first terminal of the output resistor 344, the first terminal of the adjustment resistor 343 is connected to the inverting input terminal of the operational amplifier unit 341, the second terminal of the adjustment resistor 343 is connected to the first terminal of the output resistor 344, the first pin of the operational amplifier unit 341 is connected to the positive electrode (+Vcc) of the voltage source (Volt current condenser, Vcc), and the second pin of the operational amplifier unit 341 is connected to the negative electrode (-Vcc) of the voltage source. The operational amplifier unit 341 controls the gain of the input signal (first sampling voltage signal) by reverse inputting the signal and combining the adjustment resistor 343, thereby realizing the inverting amplification of the first sampling voltage signal.

[0051] The voltage source provides a driving voltage for the operational amplifier unit 341 , and the operational amplifier unit 341 and the regulating resistor 343 invert and amplify the first sampling voltage signal based on the first resistance signal to obtain an output voltage signal.

[0052] The above-mentioned regulating resistor 343 is used to adjust the proportional relationship between the first sampling voltage signal as the input signal and the output voltage signal. In the current compensation module 34, the regulating resistor 343 is connected to the inverting input terminal of the operational amplifier unit 341 and is connected to the output resistor 344 to form a feedback circuit, which is used to adjust the accuracy of current compensation, so that the current compensation module 34 can accurately calculate the current value of the first compensation current signal, so as to effectively suppress noise through the first compensation current signal.

[0053] The push-pull unit 342 enhances the initial compensation current signal obtained based on the output voltage signal and the output resistor 344 to obtain a first compensation current signal whose current value meets the preset condition. Specifically, the push-pull unit 342 provides the required compensation current signal by controlling the output resistor 344 according to the output voltage signal of the operational amplifier unit 341. This process enhances the compensation current to make it large enough to effectively compensate for the noise signal, thereby meeting the preset condition. Optionally, the preset condition may be that the current value of the first compensation current signal is greater than a preset threshold.

[0054] The output resistor 344 sends the first compensation current signal to the first noise module 31 through the output end of the current compensation module 34. The output resistor 344 is the final output part of the current compensation module 34, which transmits the current compensation signal (i.e., the first compensation current signal) to the first noise module 31. Its function is to provide a load between the current compensation module 34 and the first noise module 31, and control the characteristics of the final output current signal, so that the first compensation current signal can effectively be opposite to the noise signal, thereby suppressing the noise.

[0055] In the embodiment of the present application, by using the feedforward control technology, current compensation is performed before or in the early stage of noise generation, which can significantly reduce the noise generated by the first noise module 31 when it is working. The current compensation module 34 can dynamically adjust the compensation current according to the sampling signal and respond to noise changes in real time, thereby achieving more accurate and more efficient noise suppression. Moreover, the current compensation module 34 directly performs current compensation through voltage sampling and signal processing, without the need for traditional current transformers, reducing the complexity and volume of hardware, thereby reducing the difficulty and cost of circuit design.

[0056] In some embodiments, Figure 3 , the current compensation module 34 also includes a direct current isolation unit 345, a first end of the direct current isolation unit 345 is connected to the second end of the output resistor 344, and a second end of the direct current isolation unit 345 is connected to the input end of the first noise module 31. Optionally, the direct current isolation unit 345 can be a direct current isolation capacitor. The direct current isolation unit 345 can effectively isolate the direct current component in the circuit and only allow the alternating current signal to pass. Since the direct current signal may have an adverse effect on the normal operation of the circuit, the direct current isolation unit can prevent the direct current component from affecting the operation of the noise module, so that the first compensation current signal is effective only within the required frequency range, which effectively improves the effectiveness and accuracy of the first compensation current signal.

[0057] Figure 4 A third structural diagram of a noise suppression circuit provided by an exemplary embodiment of the present application is shown in FIG. Figure 4 As shown, the noise suppression circuit includes: a first noise module 41, a first voltage sampling module 42, a first equivalent impedance module 43 and a current compensation module 44. The current compensation module 44 includes: an operational amplifier unit 441, a push-pull unit 442, an adjustment resistor 443, an output resistor 444 and a direct current isolation unit 445; the first end of the direct current isolation unit 445 is connected to the second end of the output resistor 444, and the second end of the direct current isolation unit 445 is connected to the input end of the first noise module 41.

[0058] The connection relationship between each module is the same as above Figure 3 The same, no further elaboration here.

[0059] In some embodiments, the noise suppression circuit also includes a first protection module 45; the output end of the first noise module 41 is connected to the input end of the first equivalent impedance module 43 through the first protection module 45; the first protection module 45 is used to follow the first sampling voltage signal output by the first voltage sampling module to obtain a first following voltage signal whose voltage value is equal to the voltage value of the first sampling voltage signal to protect the first voltage sampling module 42.

[0060] In the embodiment of the present application, by generating a first follow-up voltage signal equal to the voltage value of the first sampling voltage signal, the first protection module 45 can effectively limit excessive voltage fluctuations. Under high voltage or abnormal voltage conditions, the first voltage sampling module 42 can continue to work normally and will not fail due to instantaneous overvoltage or fluctuations, thereby improving the stability and reliability of the entire noise suppression circuit.

[0061] In some embodiments, the push-pull unit 442 includes: a first diode D1, a second diode D2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first transistor Q1, and a second transistor Q2. The output end of the operational amplifier unit 441 is connected to the cathode of the first diode D1, the anode of the first diode D1 is connected to the first end of the first resistor R1, the second end of the first resistor R1 is connected to the anode of the voltage source, the anode of the first diode D1 is connected to the base of the first transistor Q1, the collector of the first transistor Q1 is connected to the anode of the voltage source, the emitter of the first transistor Q1 is connected to the first end of the second resistor R2, and the second end of the second resistor R2 is connected to the first end of the output resistor. The output end of the operational amplifier unit 241 is connected to the positive electrode of the second diode D2, the negative electrode of the second diode D2 is connected to the first end of the third resistor R3, the second end of the third resistor R3 is connected to the negative electrode of the voltage source, the negative electrode of the second diode D2 is connected to the base of the second transistor Q2, the emitter of the second transistor Q2 is connected to the negative electrode of the voltage source, the collector of the second transistor Q2 is connected to the first end of the fourth resistor R4, and the second end of the fourth resistor R4 is connected to the first end of the output resistor 444.

[0062] In the embodiment of the present application, the push-pull unit 442 uses two triodes (Q1 and Q2) and diodes (D1 and D2) to construct a push-pull amplification structure, and realizes current enhancement through reasonable current path distribution. In this way, the amplitude of the first compensation current signal can be large enough to meet the requirements of the noise suppression circuit for compensation current. And the push-pull unit 442 effectively improves the power conversion efficiency of the circuit by combining two sets of symmetrical triode working modes. Compared with the working mode of a single triode, the push-pull unit 442 can make the current output more linear and reduce power loss, thereby optimizing the performance of the overall circuit.

[0063] In some embodiments, the first noise module 41 includes an inverter unit 411 and a load unit 412, wherein the inverter unit 411 includes a three-phase bridge arm, and the load unit 412 includes a three-phase winding; the three output ends of the three-phase bridge arm are respectively connected to the three-phase winding; the inverter unit is used to drive the load unit to operate. The load unit 412 may include a motor and related cables, etc.

[0064] In the embodiment of the present application, the inverter unit 411 converts the DC power supply into three-phase AC power through a three-phase bridge arm, and then drives the three-phase load unit 412. The high efficiency of the three-phase system can provide balanced current and lower harmonic distortion, making the operation of the load unit 412 more stable and efficient.

[0065] In some embodiments, the first voltage sampling module 42 includes a first sampling resistor SR1, a second sampling resistor SR2, a third sampling resistor SR3, a fourth sampling resistor SR4 and a fifth sampling resistor SR5; the three-phase winding is respectively connected to the first end of the first sampling resistor SR1, the first end of the second sampling resistor SR2 and the first end of the third sampling resistor SR3; the second end of the first sampling resistor SR1, the second end of the second sampling resistor SR2 and the second end of the third sampling resistor SR3 are all connected to the first end of the fourth sampling resistor SR4, the second end of the fourth sampling resistor SR4 is connected to the first end of the fifth sampling resistor SR5, and the second end of the fifth sampling resistor SR5 is connected to the ground line.

[0066] In the embodiment of the present application, by configuring multiple sampling resistors in series and in parallel, the voltage of the three-phase winding can be sampled with high precision. The sampling resistor combination forms a voltage divider circuit, which can effectively filter out some high-frequency noise or fluctuations and reduce the impact of external interference, thereby improving the stability and reliability of the voltage signal.

[0067] In some embodiments, the first equivalent impedance module 43 includes a first common-mode resistor 431 equivalent to the impedance of the load unit 412, and a first common-mode capacitor 432 equivalent to the impedance of the inverter unit 411; the input end of the first common-mode resistor 431 is connected to the input end of the first common-mode capacitor 432, and the output end of the first common-mode resistor 431 is connected to the output end of the first common-mode capacitor 432.

[0068] In the embodiment of the present application, the first equivalent impedance module 43 realizes impedance matching between the load unit 412 and the inverter unit 411. By adjusting the values ​​of the first common mode resistor 431 and the first common mode capacitor 432, the circuit can transfer energy more efficiently during operation, thereby optimizing power output, and impedance matching can reduce power loss and ensure that the system operates in a stable state.

[0069] Above Figure 4 The noise suppression circuit provided adopts a common-mode voltage sampling and compensation mechanism to suppress the common-mode current (EMI noise) generated by the load unit 412 and the inverter unit 411, and suppresses or offsets the common-mode current by injecting a reverse first compensation current signal. Figure 4 The entire compensation mechanism is described.

[0070] In the above Figure 4In the DC bus, the DC bus (Direct Current Busbar, DC Bus) includes a positive pole (Bus+) and a negative pole (Bus-), which are used to provide a stable DC input voltage. bus ) is connected in parallel to the DC bus to filter out ripples in the DC bus voltage and maintain the stability of the DC bus voltage. The inverter unit 411 generates an AC voltage according to the filtered DC input voltage to drive the load unit 412 to operate.

[0071] Optionally, the inverter unit 411 may be composed of six switching devices, two switching devices per phase, and U, V, and W are three-phase output terminals. The voltage value of the noise voltage generated by the first noise module 41 can be expressed as Among them, U U , U V and U w represents the three-phase voltage of the first noise module 41, that is, the noise voltage V cm The magnitude is the average value of the three-phase voltage. In order to facilitate subsequent processing, the noise voltage of the first noise module 41 is sampled through a resistor voltage divider network (first voltage sampling module 42). The voltage value of the output voltage of the first voltage sampling module 42 can be expressed as V sen , and has the following proportional relationship with the noise voltage: V sen = k·V cm Wherein, k is the voltage division coefficient, and the value of k is determined by the resistance value of the first voltage sampling module 42. By selecting an appropriate resistance voltage division ratio, the sampled common mode voltage, that is, the voltage value V of the first sampled voltage signal can be ensured. sen Avoid overvoltage or undervoltage within the input voltage range of the op amp. The voltage division factor k can be expressed as: Wherein, R1, R2, R3, R4 and R5 are the resistance values ​​of the first sampling resistor SR1, the second sampling resistor SR2, the third sampling resistor SR3, the fourth sampling resistor SR4 and the fifth sampling resistor SR5 respectively. Optionally, the resistance values ​​of the first sampling resistor SR1, the second sampling resistor SR2 and the third sampling resistor SR3 can be equal, and the voltage division coefficient k can be adjusted by appropriately selecting the resistors to control the output first voltage signal to be within the normal working range of the operational amplifier unit 441.

[0072] Optionally, the first protection module 45 includes a first operational amplifier U 1B , the first operational amplifier U 1B As a voltage follower (buffer), a low impedance output is provided to prevent the subsequent circuit from causing a load effect on the first voltage sampling module 42. In other words, the first protection module 45 ensures that the voltage value V senThe voltage value V of the first follower voltage signal output by the first protection module 45 will not change due to the influence of the load, thereby improving the stability of the active EMI filter. in The voltage value V of the first sampling voltage signal sen Likewise, the first follower voltage signal is transmitted to the subsequent circuit.

[0073] Optionally, the operational amplifier unit 441 includes a second operational amplifier U 1A , the second operational amplifier U 1A The first equivalent impedance module 43 formed with it forms a voltage inverter. The function of the voltage inverter is to convert the common mode voltage into a reverse common mode current. Therefore, the artificially fitted impedance network (i.e., the first equivalent impedance module 43) includes a first common mode resistor 431 equivalent to the impedance of the load unit 412, and the resistance value is Z motor , and a first common mode capacitor 432 equivalent to the impedance of the inverter unit 411, with a resistance value of Z Cp The impedance signal provided by the artificially fitted impedance network, that is, the resistance value of the first resistance signal, can be expressed as Z a =Z motor / / Z Cp

[0074] The first sampled voltage signal after the scaling is applied is transmitted to the first equivalent impedance module 43, and the current compensation module 44 can calculate the voltage value V of the first sampled voltage signal according to the voltage value V sen (or V in ) and the resistance value Z of the first resistance signal a Calculate the current value I of the first compensation current signal inj Specifically, according to the virtual short principle of the operational amplifier, the current I flowing through the first equivalent impedance module 43 is in With the noise voltage V cm There are the following relationships between them:

[0075] I in = k·V cm Z a

[0076] Through the operational amplifier U 1A The inverting amplification effect of the output voltage signal is: Vo = -R f ·V cm ·Z a Among them, R f is the resistance value of the regulating resistor 443. inj It can be calculated by the following formula:

[0077]

[0078] Among them, Z LISN is the resistance value of the noise detection module (not shown in the figure), which may include a line impedance stabilization network (LISN) for testing and measuring electromagnetic interference (EMI) generated by devices on the power line. a is the magnitude of the first resistance signal provided by the first equivalent impedance module 43, Z inj is the resistance value of the output resistor 444. The DC isolation unit 445 mentioned above mainly plays a role of DC isolation. Within the frequency band of EMI noise, the impedance of the DC isolation unit 445 can be approximately ignored.

[0079] Then, Z inj >>Z LISN ∥Z a , then the magnitude of the first compensation current signal can be approximately expressed as:

[0080]

[0081] In actual use, by selecting appropriate parameters, the first compensation current can be effectively combined with the common mode current I cm Specifically, the size R of the appropriate adjustment resistor 443 can be set f and the resistance value Z of the output resistor 444 inj , to achieve the common mode current I cm The first compensation current injected is equal to the common mode current in magnitude and opposite in direction, thereby achieving the purpose of common mode current compensation and reducing EMI noise. The specific compensation relationship can be expressed as: I inj =-I cm .

[0082] The following describes the test and fitting process of the common mode impedance of the earth by the load unit 412 and the inverter unit 411 respectively.

[0083] Figure 5 A structural diagram of a test circuit provided by an exemplary embodiment of the present application is shown in FIG. Figure 5 As shown, the output cable at the midpoint (V) of the three-phase bridge arm (U, V, W) can be short-circuited directly, and the common-mode impedance between the load unit 412 and the ground can be tested using an impedance analyzer to obtain a curve of the common-mode impedance between the load unit 412 and the ground changing with frequency. Then, by using RLC components (i.e., a combination of resistors, inductors, and capacitors), an impedance curve similar to the actual test result can be fitted. Thus, the common-mode impedance between the load unit 412 and the ground can be simulated more accurately, and the design of the noise suppression circuit can be further optimized.

[0084] Figure 6 This is a schematic diagram of another test circuit provided by an exemplary embodiment of the present application. When measuring the common mode impedance of the midpoint of the three-phase bridge arm of the inverter unit 411 and the printed circuit board (PCB) wiring to the ground, the following can be used: Figure 6 The circuit configuration shown in the figure is used for accurate testing. The specific method is to first remove the capacitor between BUS+ and BUS- on the PCB to ensure that no additional capacitor interferes with the measurement results. Next, short-circuit the three terminals of the inverter output to eliminate any possible interference signals and ensure that the measured common-mode impedance only reflects the electrical characteristics between the bridge arm output and the casing. In this way, the common-mode impedance of the inverter unit 411 to the earth (casing) can be measured. In the actual test process, the common-mode impedance obtained usually changes with the change of frequency, and capacitors can be used to fit these test results to generate a similar impedance curve.

[0085] Figure 7 A schematic diagram of common mode impedance characteristics provided for an exemplary embodiment of the present application. According to the operating frequency range of the active EMI (electromagnetic interference) filter (AEF), the effective frequency band is usually 150kHz to 5MHz. In this frequency band, the impedance characteristics of the motor and the cable to the ground show different frequency responses. Figure 7 As shown, the impedance characteristics obtained by the test show the law of change of the impedance of the load unit 412 to the ground with the frequency. In the low frequency band (C), the impedance of the load unit 412 to the ground presents a capacitive characteristic, which means that the impedance increases as the frequency decreases. At a certain frequency, the impedance of the load unit 412 at the first resonance point (LC series resonance) exhibits an inductive characteristic, and at this time the interaction between the inductance and the capacitance forms an LC series resonance point (fr1). Near this frequency point, the impedance of the circuit reaches a minimum value. Next, at the second resonance point (fr2), the impedance curve exhibits the characteristics of a parallel circuit, which means that the impedance of the load unit 412 to the ground reaches a maximum value near this frequency point and has the characteristics of a parallel LC resonance. When the frequency exceeds the second resonance point (f>fr2), the impedance curve again exhibits a capacitive characteristic, that is, the dominant effect of the capacitor on the impedance increases. Finally, at the third resonance point (f>fr3), the impedance curve again exhibits an inductive characteristic, indicating that the impedance of the load unit 412 is again dominated by the inductance. According to the above characteristics, the following can be used Figure 8 The circuit model shown fits the common mode impedance of the load unit 412 to the ground. The circuit includes a plurality of RLC elements (inductor L1, inductor L2, resistor R a1 , resistor R a2 , resistor R a1 , resistor R b2, capacitor C1, capacitor C2 and capacitor C3), which can simulate the impedance characteristics of the motor and cable. In addition, Fig. 9 The simplified circuit shown (including the inductor L s1 、Inductance L s2 , capacitor C s1 , capacitor C s2 , resistor R s1 and resistor R s2 ) can also be used to simulate the common mode impedance of the load unit 412 to the ground. The simplified circuit can effectively reflect the impedance characteristics between the load unit 412 and the ground by reducing the number of components, and is suitable for simplified electromagnetic compatibility analysis and design.

[0086] Fig.10 The structure diagram of a noise suppression circuit for multiple noise sources provided by an exemplary embodiment of the present application is shown in FIG. Fig.10 As shown, the noise suppression circuit includes: a first noise module 101, a first voltage sampling module 102, a first equivalent impedance module 103, a current compensation module 104, a first protection module 105, a second noise module 106, a second voltage sampling module 107, a second equivalent impedance module 108 and a second protection module 109.

[0087] Among them, the input end of the second noise module 106 is connected to the input end of the second voltage sampling module 107, the output end of the second noise module 106 is connected to the output end of the second voltage sampling module 107, the input end of the second voltage sampling module 107 is used to receive the input voltage, the output end of the second voltage sampling module 107 is connected to the input end of the second equivalent impedance module 108, the output end of the second equivalent impedance module 108 is connected to the input end of the current compensation module 104, and the signal end of the current compensation module is connected to the signal end of the second voltage sampling module 107. The connection relationship of other modules is the same as above Figure 4 The same, no further elaboration here.

[0088] In the embodiment of the present application, in the noise suppression circuit of multiple noise sources, a corresponding voltage sampling module, a protection module and an equivalent impedance module are added for each noise source. Since each noise source (such as the first noise module and the second noise module) has an independent voltage sampling module and an equivalent impedance module, they can provide compensation signals for different noise sources respectively to avoid the compensation of one noise source affecting another noise source. As a result, the noise suppression circuit can more accurately suppress the interference of each noise source.

[0089] In some embodiments, the second noise module 106 is configured to operate according to an input voltage;

[0090] The second voltage sampling module 107 is used to detect the second sampled voltage signal of the second noise module 106 , and send the second sampled voltage signal to the current compensation module 104 through the signal terminal of the second voltage sampling module 107 .

[0091] The second equivalent impedance module 108 is used to provide the current compensation module 104 with a second resistance signal equivalent to the resistance value of the second noise module 106 .

[0092] The current compensation module 104 is used to determine the current value of the second compensation current signal according to the voltage value of the first sampled voltage signal, the voltage value of the second sampled voltage signal, the resistance value of the first resistance signal and the resistance value of the second resistance signal, and send the second compensation current signal to the first noise module 101 and the second noise module 106 to reduce the noise generated when the first noise module 101 and the second noise module 106 are working.

[0093] In the noise suppression circuit of multiple noise sources, the second noise module 106 has the same structure and function as the first noise module 101, the second voltage sampling module 107 has the same structure and function as the first voltage sampling module 102, the second protection module 109 has the same structure and function as the first protection module 105, and the second equivalent impedance module 108 has the same structure and function as the first equivalent impedance module 103, which will not be described in detail here.

[0094] Above Fig.10 The invention relates to a noise suppression circuit for multiple noise sources. In a system including multiple noise sources (such as fans, compressors, etc.), a voltage sampling module for each noise source (such as a first noise module 101 and a second noise module 106) is added to collect the noise voltage corresponding to each noise source, and a corresponding fitting resistor network (a first equivalent impedance module 103 and a second equivalent impedance module 108) is used to match the characteristic impedance of each noise source. Through fine adjustment, the common-mode noise generated by different noise sources can be effectively suppressed, so as to improve the noise suppression capability of the multi-noise source system without significantly increasing the system cost.

[0095] In some embodiments, the noise suppression circuit provided by the present application can be applied to household appliances (such as air conditioners, refrigerators, etc.), communication equipment, and industrial automation equipment. Next, the application of the noise suppression circuit is described by taking an air conditioner as an example.

[0096] Fig.11 The structural diagram of an air conditioning system provided by an exemplary embodiment of the present application is shown in FIG. Fig.11As shown, the air conditioning system includes a first noise module 111, a first voltage sampling module 112, a first equivalent impedance module 113, a current compensation module 114, an input module 115, a line impedance stabilization module 116, a passive filtering module 117 and a rectifier module 118. The output end of the input module 115 is connected to the input end of the line impedance stabilization module 116, the output end of the line impedance stabilization module 116 is connected to the input end of the passive filtering module 117, the output end of the passive filtering module 117 is connected to the input end of the rectifier module 118, and the output end of the rectifier module 118 is connected to the input end of the first voltage sampling module.

[0097] The input module 115 is used to provide AC voltage for the entire air conditioning system to ensure the power supply of the system. The line impedance stabilization module 116 is used to balance the impedance of the power line to stabilize the current flow in the power system and reduce power loss. The passive filtering module 117 is used to filter out high-frequency noise and harmonics in the input module 115 to improve the power quality. The rectifier module 118 is used to convert the AC power supply into a DC power supply to provide a stable DC voltage for the subsequent first noise module 111 and the first voltage sampling module. These modules work together to enable the air conditioning system to operate stably and efficiently, reduce power supply interference, and improve the overall performance and reliability of the air conditioning system.

[0098] Furthermore, based on the above Fig.11 The structure diagram of the air conditioning system including the noise suppression circuit provided is used to construct a simulation diagram. Optionally, the power supply can use ±12V (volts) as an auxiliary power supply to provide a stable operating voltage for the operational amplifier and the push-pull output stage. Based on the above simulation diagram, simulation results can be obtained and analyzed. Fig.12 A schematic diagram of a first simulation result provided by an exemplary embodiment of the present application, Fig.12 The common-mode current signal (I cm ), the first compensation current signal (I inj ) and the noise detection module detects the detection noise current signal (I LISN ) Dynamic waveform under the action of active filter. From the waveform comparison, it can be seen that under the action of active filter, the amplitude and high-frequency component of the noise current signal detected by the noise detection module are significantly reduced. Fig.13 A schematic diagram of a second simulation result provided by an exemplary embodiment of the present application, Fig.13 It can be seen that the common-mode current signal (I cm ) and the first compensation current signal (I inj ) have an obvious cancellation relationship in the time domain. The noise current signal detected by the noise detection module is close to zero after the filter acts, indicating that the active filter effectively suppresses most of the high-frequency components. Fig.14A schematic diagram of a third simulation result provided by an exemplary embodiment of the present application, Fig.14 The active filter's suppression effect on common-mode noise signals is demonstrated, and its noise attenuation performance is verified in the frequency domain. Specifically, within the frequency range of 150kHz-5MHz, the first sampled voltage signal (V cm ) is compared to the common-mode noise voltage signal (V LISN ) curve has a significant decrease, which means that the noise suppression circuit has a significant attenuation effect on the common mode noise in this frequency band.

[0099] Above Fig.12 , Fig.13 and Fig.14 The simulation results in show that the active filter including the noise suppression circuit provided in the present application can effectively compensate for the high-frequency common-mode noise current generated by the noise source, thereby significantly reducing the conducted noise of EMI.

[0100] The noise suppression circuit provided in the embodiment of the present application includes a first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module; the current compensation module adjusts the compensation current according to the first sampled voltage signal and the first resistance signal, and injects the compensation current into the first voltage sampling module, so as to perform corresponding current compensation before or at the early stage of noise generation through feedforward control technology, thereby effectively reducing the noise generated by the first noise module when it is working. Moreover, current compensation is performed directly through voltage sampling and signal processing, without the need for a traditional current transformer, thereby reducing the volume, complexity and cost of the noise suppression circuit.

[0101] The embodiment of the present application also provides an air conditioning device, comprising: the noise suppression circuit described in the embodiment of the present application. The noise suppression circuit is used to reduce the noise generated by the motor, compressor, fan, etc. in the air conditioning device when they are working.

[0102] The above-mentioned embodiments are merely preferred embodiments of the present application and are not intended to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements made to the technical solutions of the present application by ordinary technicians in this field should fall within the protection scope determined by the claims of the present application.

Claims

1. A noise suppression circuit, characterized in that: The noise suppression circuit comprises: A first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module; The input end of the first noise module is connected to the input end of the first voltage sampling module, the output end of the first noise module is connected to the output end of the first voltage sampling module, the input end of the first voltage sampling module is used to receive an input voltage, the output end of the first voltage sampling module is connected to the input end of the first equivalent impedance module, the output end of the first equivalent impedance module is connected to the input end of the current compensation module, the output end of the current compensation module is connected to the input end of the first noise module, and the signal end of the current compensation module is connected to the signal end of the first voltage sampling module; The first noise module is used to operate according to the input voltage; The first voltage sampling module is used to detect a first sampled voltage signal of the first noise module, and send the first sampled voltage signal to the current compensation module through a signal terminal of the first voltage sampling module; The first equivalent impedance module is used to provide the current compensation module with a first resistance signal equivalent to the resistance value of the first noise module; The current compensation module is used to determine the current value of a first compensation current signal according to the voltage value of the first sampling voltage signal and the resistance value of the first resistance signal, and send the first compensation current signal to the first noise module to reduce the noise generated when the first noise module is working. The current compensation module includes a voltage source, and the voltage source is used to provide a driving voltage for the current compensation module.

2. The noise suppression circuit according to claim 1, characterized in that: The current compensation module includes: an operational amplifier unit, a push-pull unit, an adjustment resistor and an output resistor; The inverting input terminal of the operational amplifier unit is connected to the output terminal of the first equivalent impedance module, the non-inverting input terminal of the operational amplifier unit is connected to the ground wire, the output terminal of the operational amplifier unit is connected to the input terminal of the push-pull unit, the output terminal of the push-pull unit is connected to the first terminal of the output resistor, the first terminal of the regulating resistor is connected to the inverting input terminal of the operational amplifier unit, the second terminal of the regulating resistor is connected to the first terminal of the output resistor, the first pin of the operational amplifier unit is connected to the positive electrode of the voltage source, and the second pin of the operational amplifier unit is connected to the negative electrode of the voltage source; The voltage source provides a driving voltage for the operational amplifier unit, and the operational amplifier unit and the regulating resistor invert and amplify the first sampling voltage signal based on the first resistance signal to obtain an output voltage signal; The push-pull unit enhances the initial compensation current signal obtained based on the output voltage signal and the output resistance to obtain the first compensation current signal whose current value meets a preset condition; The output resistor sends the first compensation current signal to the first noise module through the output terminal of the current compensation module.

3. The noise suppression circuit according to claim 2, characterized in that: The current compensation module also includes a DC isolation unit; The first end of the DC isolation unit is connected to the second end of the output resistor, and the second end of the DC isolation unit is connected to the input end of the first noise module.

4. The noise suppression circuit according to claim 2, characterized in that: The push-pull unit includes: a first diode, a second diode, a first resistor, a second resistor, a third resistor, a fourth resistor, a first triode and a second triode; The output end of the operational amplifier unit is connected to the cathode of the first diode, the anode of the first diode is connected to the first end of the first resistor, the second end of the first resistor is connected to the anode of the voltage source, the anode of the first diode is connected to the base of the first transistor, the collector of the first transistor is connected to the anode of the voltage source, the emitter of the first transistor is connected to the first end of the second resistor, and the second end of the second resistor is connected to the first end of the output resistor; The output end of the operational amplifier unit is connected to the anode of the second diode, the cathode of the second diode is connected to the first end of the third resistor, the second end of the third resistor is connected to the negative electrode of the voltage source, the cathode of the second diode is connected to the base of the second transistor, the emitter of the second transistor is connected to the negative electrode of the voltage source, the collector of the second transistor is connected to the first end of the fourth resistor, and the second end of the fourth resistor is connected to the first end of the output resistor.

5. The noise suppression circuit according to claim 2, characterized in that: The noise suppression circuit also includes a first protection module; The output end of the first noise module is connected to the input end of the first equivalent impedance module through the first protection module; The first protection module is used to follow the first sampling voltage signal output by the first voltage sampling module to obtain a first following voltage signal whose voltage value is equal to the voltage value of the first sampling voltage signal, so as to protect the first voltage sampling module.

6. The noise suppression circuit according to claim 1, wherein: The first noise module includes an inverter unit and a load unit, the inverter unit includes a three-phase bridge arm, and the load unit includes a three-phase winding; The three output ends of the three-phase bridge arm are respectively connected to the three-phase windings; The inverter unit is used to drive the load unit to operate.

7. The noise suppression circuit according to claim 6, characterized in that: The first voltage sampling module includes a first sampling resistor, a second sampling resistor, a third sampling resistor, a fourth sampling resistor and a fifth sampling resistor; The three-phase winding is respectively connected to the first end of the first sampling resistor, the first end of the second sampling resistor and the first end of the third sampling resistor; The second end of the first sampling resistor, the second end of the second sampling resistor and the second end of the third sampling resistor are all connected to the first end of the fourth sampling resistor, the second end of the fourth sampling resistor is connected to the first end of the fifth sampling resistor, and the second end of the fifth sampling resistor is connected to the ground line.

8. The noise suppression circuit according to claim 6, characterized in that: The first equivalent impedance module includes a first common-mode resistor equivalent to the impedance of the load unit, and a first common-mode capacitor equivalent to the impedance of the inverter unit; An input end of the first common-mode resistor is connected to an input end of the first common-mode capacitor, and an output end of the first common-mode resistor is connected to an output end of the first common-mode capacitor.

9. The noise suppression circuit according to claim 2, characterized in that: The noise suppression circuit also includes a second noise module, a second voltage sampling module and a second equivalent impedance module; The input end of the second noise module is connected to the input end of the second voltage sampling module, the output end of the second noise module is connected to the output end of the second voltage sampling module, the input end of the second voltage sampling module is used to receive an input voltage, the output end of the second voltage sampling module is connected to the input end of the second equivalent impedance module, the output end of the second equivalent impedance module is connected to the input end of the current compensation module, and the signal end of the current compensation module is connected to the signal end of the second voltage sampling module; The second noise module is used to operate according to the input voltage; The second voltage sampling module is used to detect the second sampled voltage signal of the second noise module, and send the second sampled voltage signal to the current compensation module through the signal terminal of the second voltage sampling module; The second equivalent impedance module is used to provide the current compensation module with a second resistance signal equivalent to the resistance value of the second noise module; The current compensation module is used to determine the current value of the second compensation current signal according to the voltage value of the first sampled voltage signal, the voltage value of the second sampled voltage signal, the resistance value of the first resistance signal, and the resistance value of the second resistance signal, and send the second compensation current signal to the first noise module and the second noise module to reduce the noise generated when the first noise module and the second noise module are working.

10. An air conditioning device, characterized in that: Comprising the noise suppression circuit as claimed in any one of claims 1 to 9.

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