Motor current sampling method, motor assembly and household appliance

Abstract

The application discloses a motor current sampling method, a motor assembly and household electrical appliances. The motor current sampling method comprises the following steps: acquiring actual gain ratios of each current sampling circuit and current sampling signals output by each current sampling circuit; determining end voltages of sampling resistors in each current sampling circuit according to the actual gain ratios of each current sampling circuit and the current sampling signals output by each current sampling circuit; acquiring actual resistance values of the sampling resistors in each current sampling circuit; and determining three-phase currents of the motor according to the end voltages of the sampling resistors in each current sampling circuit and the actual resistance values of the sampling resistors in the corresponding current sampling circuit. The technical scheme can reduce the distortion of output signals of the current sampling circuit.

Description

Technical Field

[0001] This invention relates to the field of motor current sampling technology, and in particular to a method for sampling motor current, a motor assembly, and a household appliance. Background Technology

[0002] In existing motor drives, current sampling circuits are typically used to sample the motor current for closed-loop control. However, existing current sampling circuits are affected by the accuracy of the components in the circuit, which can lead to output signal distortion and thus affect the subsequent control accuracy of the motor. Summary of the Invention

[0003] The main objective of this invention is to provide a method for sampling motor current, which aims to solve the problem of poor motor control accuracy caused by distortion of the output signal of the current sampling circuit.

[0004] To achieve the above objectives, the present invention proposes a method for sampling motor current, the method comprising:

[0005] Obtain the actual gain ratio and the current sampling signal output by each current sampling circuit. Based on the actual gain ratio and the current sampling signal output by each current sampling circuit, determine the terminal voltage of the sampling resistor in each current sampling circuit; and,

[0006] Obtain the actual resistance value of the sampling resistor in each current sampling circuit, and determine the three-phase current of the motor based on the terminal voltage of the sampling resistor in each current sampling circuit and the actual resistance value of the sampling resistor in the corresponding current sampling circuit.

[0007] Optionally, before obtaining the actual gain ratio of each current sampling circuit, the motor current sampling method further includes:

[0008] Inject an AC current with preset parameters into the motor and obtain the current sampling signal waveform output by each current sampling circuit after injection.

[0009] Obtain the preset parameters of the AC current and the actual resistance value of the sampling resistor in each current sampling circuit. Based on the actual resistance value of the sampling resistor in each current sampling circuit, the current sampling signal waveform output by each current sampling circuit, and the preset parameters of the AC current, determine the actual gain ratio of each current sampling circuit.

[0010] Optionally, the alternating current is a sinusoidal current.

[0011] Optionally, the preset parameter is the effective current value of the alternating current.

[0012] Optionally, the actual gain ratio of each current sampling circuit is determined based on the actual resistance value of the sampling resistor in each current sampling circuit, the current sampling signal waveform output by each current sampling circuit, and the preset parameters of the AC current. Specifically:

[0013] The difference between the maximum and minimum signal values ​​in each current sampling signal waveform is compared with the product of the effective current value of the AC current and the actual resistance value of each sampling resistor. The result of the ratio calculation is used as the actual gain ratio of the corresponding current sampling circuit.

[0014] Optionally, based on the actual gain ratio of each current sampling circuit and the current sampling signal output by each current sampling circuit, the terminal voltage of the sampling resistor in each current sampling circuit is determined, specifically as follows:

[0015] The ratio of the current sampling signal output by each current sampling circuit to the actual gain ratio of that current sampling circuit is used as the terminal voltage of the sampling resistor in that current sampling circuit.

[0016] Optionally, the three-phase current of the motor is determined based on the terminal voltage of the sampling resistor in each current sampling circuit and the actual resistance value of the sampling resistor in the corresponding current sampling circuit, specifically as follows:

[0017] The ratio of the terminal voltage of each sampling resistor to the actual resistance value of that sampling resistor is used as one phase current of the motor.

[0018] The present invention also proposes a motor assembly, the motor assembly comprising:

[0019] Electric motor;

[0020] The inverter module has a three-phase bridge arm circuit, and the output terminal of each phase bridge arm circuit is connected to one phase input terminal of the motor.

[0021] At least two current sampling circuits, each current sampling circuit having a sampling resistor, each sampling resistor being connected to one phase of the bridge arm circuit, each current sampling circuit being used to sample the current on the connected bridge arm circuit and output a corresponding current sampling signal;

[0022] The main control unit is connected to multiple controlled terminals of the inverter module and the output terminal of each current sampling circuit.

[0023] Optionally, each of the current sampling circuits further includes:

[0024] An operational amplifier circuit is provided, wherein the first input terminal and the second input terminal of the operational amplifier circuit are respectively connected to the two ends of the sampling resistor, and the output terminal of the operational amplifier circuit is connected to the main control unit.

[0025] Optionally, the operational amplifier circuit includes:

[0026] The system comprises a first resistor, a second resistor, a third resistor, a fourth resistor, and a first operational amplifier. The first end of the first resistor and the first end of the second resistor are respectively connected to the two ends of the sampling resistor in the current sampling circuit. The second ends of the first resistor and the second resistor are respectively connected to the non-inverting and inverting inputs of the first operational amplifier. The second end of the first resistor is also connected to a preset bias voltage via the third resistor. The output terminal of the first operational amplifier is connected to the inverting input via the fourth resistor. The output terminal of the first operational amplifier is the output terminal of the current sampling circuit.

[0027] The present invention also proposes a household appliance, which includes a motor assembly as described above.

[0028] Optionally, the household appliance is an air conditioner.

[0029] The present invention provides a method for sampling motor current by acquiring the actual gain ratio and the current sampling signal output by each current sampling circuit. Based on these parameters, the terminal voltage of the sampling resistor in each current sampling circuit is determined. Furthermore, the actual resistance value of the sampling resistor in each current sampling circuit is acquired, and the three-phase current of the motor is determined based on the terminal voltage and the actual resistance value of the sampling resistor in the corresponding current sampling circuit. This invention significantly reduces output signal distortion caused by parameter errors and fluctuations in each current sampling circuit by using the actual gain ratio and actual resistance value of each sampling resistor to determine the three-phase current of the motor. It also eliminates the influence of different errors in each current sampling circuit on the accuracy of determining the three-phase current, thereby improving the accuracy of the three-phase current determination and subsequent motor control. This solves the problem of poor motor control accuracy caused by distortion in the output signal of the current sampling circuit. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0031] Figure 1 This is a flowchart illustrating an embodiment of the motor current sampling method of the present invention;

[0032] Figure 2This is a flowchart illustrating another embodiment of the motor current sampling method of the present invention;

[0033] Figure 3 This is a schematic diagram of a module of an embodiment of the motor assembly of the present invention;

[0034] Figure 4 This is a schematic diagram of the hardware operating environment of the main control unit in one embodiment of the motor assembly of the present invention;

[0035] Figure 5 This is a circuit diagram of an embodiment of the motor assembly of the present invention;

[0036] Figure 6 This is a schematic diagram of the waveform of the current sampling signal in the motor current sampling method of the present invention.

[0037] Explanation of icon numbers:

[0038]

[0039] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0042] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0044] This invention proposes a method for sampling motor current, which can be applied to household appliances with motors such as air conditioners and refrigerators.

[0045] Currently, motor control schemes typically employ at least two current sampling circuits to sample the three-phase AC current output from the inverter module to the motor. This allows the main control unit to determine the real-time three-phase current connected to the motor based on the current sampling signals from the voltage signals output by each current sampling circuit. This enables subsequent estimation of the motor rotor or current loop control of the motor. Current sampling circuits are typically constructed using operational amplifiers and resistors, and require a DC bias voltage to maintain their operation. Those skilled in the art can directly calculate the gain ratio (ideal gain ratio) of the operational amplifier circuit in the current sampling circuit based on its circuit structure, the calibration parameters of each electronic component, and the stable value of the DC bias voltage. This ideal gain ratio is then directly configured as the gain ratio of the operational amplifier circuit in each current sampling circuit to reconstruct the three-phase current during motor operation. However, in reality, there are parameter errors between the actual parameters and the calibrated parameters of each electronic device, and there are fluctuation errors in the DC bias voltage value. Furthermore, the parameter errors and fluctuation errors in each current sampling circuit are not the same. Therefore, the three-phase current value calculated using the same ideal gain ratio has an error with the actual three-phase current value, which is not conducive to the subsequent control of the motor.

[0046] In response to this issue, refer to Figure 1 In one embodiment of the present invention, the method for sampling motor current includes:

[0047] Step S100: Obtain the actual gain ratio of each current sampling circuit and the current sampling signal output by each current sampling circuit. Based on the actual gain ratio of each current sampling circuit and the current sampling signal output by each current sampling circuit, determine the terminal voltage of the sampling resistor in each current sampling circuit.

[0048] The motor current sampling method of this invention can be a main control unit in the motor assembly. The main control unit can call up pre-stored or pre-calculated actual gain ratios of each current sampling circuit, and can input multiple current sampling signals output by each current sampling circuit after sampling the three-phase current during motor operation. The main control unit can also convert each current sampling signal into a digital signal, and obtain the corresponding voltage value (i.e., the output voltage of each current sampling circuit) by analyzing and calculating the digital signal. Furthermore, it can calculate the voltage value corresponding to each current sampling signal and the actual gain ratio of the output current sampling circuit to determine the terminal voltage across the sampling resistor in each current sampling circuit.

[0049] It should be noted that the actual gain ratio of each current sampling circuit can be obtained in advance and stored in the main control unit during the motor's factory testing phase, or it can be pre-calculated during the parameter tuning phase before the motor is in normal operation.

[0050] Specifically, during the factory testing or parameter tuning phase, a precise standard current is injected into the motor to obtain the terminal voltage generated across the sampling resistor in each current sampling circuit and the output voltage of each current sampling circuit at this time. The ratio of the output voltage of each current sampling circuit to the terminal voltage of its sampling resistor can be used as the actual gain ratio of that current sampling circuit. During the factory testing phase, each calculated actual gain ratio can be associated with the corresponding current sampling circuit and stored in the main control unit for retrieval when the main control unit executes step S100 during normal motor operation. During the parameter tuning phase, each actual gain ratio can be directly configured as the actual gain ratio of the corresponding current sampling circuit, so that the main control unit can retrieve it when the motor executes step S100 during normal motor operation. It should be further noted that the actual gain ratios pre-calculated during the parameter tuning phase are more timely than those pre-obtained during the factory testing phase. This effectively reduces the impact of electronic component aging and circuit aging on the actual gain ratios of each current sampling circuit, and helps to further improve the accuracy of the motor's three-phase current determination.

[0051] Step S200: Obtain the actual resistance value of the sampling resistor in each current sampling circuit, and determine the three-phase current of the motor based on the terminal voltage of the sampling resistor in each current sampling circuit and the actual resistance value of the sampling resistor in the corresponding current sampling circuit.

[0052] The main control unit can also call up or retrieve the actual resistance values ​​of the sampling resistors in each current sampling circuit, which are pre-stored or pre-calculated. The ratio of the terminal voltage of each sampling resistor to its actual resistance value can be used as the current value flowing through that sampling resistor, i.e., the real-time current value of one phase of the motor's AC current. It can be understood that when there are three current sampling circuits, the current values ​​flowing through each sampling resistor in the three current sampling circuits can be used as the real-time current values ​​of the three phases of the motor, thus determining the three-phase current of the motor. When there are two current sampling circuits, since the sum of the current values ​​of the three-phase AC current at any given time is 0, the main control unit can first sum the current values ​​flowing through the two sampling resistors, then calculate the difference between the sum and 0, and use the difference as the real-time current value of the third phase of the AC current. The current values ​​flowing through the two sampling resistors can then be used as the real-time current values ​​of the other two phases of the AC current, thus determining the three-phase current of the motor.

[0053] It should be noted that the actual resistance value of each sampling resistor can also be pre-acquired and stored in the main control unit during the factory testing phase, or pre-calculated during the parameter tuning phase. Specifically, during the factory testing or parameter tuning phase, a standard current with precise current parameters can be injected into the motor to obtain the terminal voltage generated across each sampling resistor and the current value flowing through it. The actual resistance value of the sampling resistor can be obtained by taking the ratio of the terminal voltage of each sampling resistor to the current value flowing through it. During the factory testing phase, the calculated actual resistance value of each sampling resistor can be associated with the corresponding current sampling circuit and stored in the main control unit for retrieval when the main control unit executes step S200 during normal motor operation. During the parameter tuning phase, the actual resistance value of each sampling resistor can be directly configured to the actual resistance value of the corresponding sampling resistor so that the main control unit can retrieve it when the main control unit executes step S200 during normal motor operation. It should be further explained that the actual resistance values ​​of the sampling resistors are calculated in advance during the parameter tuning stage. Compared with the values ​​obtained in advance during the factory testing stage, the actual resistance values ​​of each sampling resistor are more timely. This can effectively reduce the impact of aging of the sampling resistors on their actual resistance values ​​and help to further improve the accuracy of the determination of the three-phase current of the motor.

[0054] This invention determines the three-phase current of the motor by using the actual gain ratio of each current sampling circuit and the actual resistance value of each sampling resistor. This significantly reduces output signal distortion caused by parameter errors and fluctuations in each current sampling circuit, and also eliminates the impact of different errors in each current sampling circuit on the accuracy of three-phase current determination. This improves the accuracy of three-phase current determination and subsequent motor control, thus solving the problem of poor motor control accuracy caused by current sampling circuit output signal distortion. Furthermore, for open-winding motor control algorithms with even higher requirements for current sampling signal distortion, this invention effectively improves the control accuracy of open-winding motors, thus benefiting their application in household appliances, especially air conditioners.

[0055] Reference Figure 2 In one embodiment of the present invention, before step S100, the method for sampling the motor current further includes:

[0056] Step 300: Inject an AC current with preset parameters into the motor, and obtain the current sampling signal waveform output by each current sampling circuit after injection;

[0057] In this embodiment, step 300 can be performed during the motor's factory testing phase to avoid the problem of excessively lengthy parameter tuning stages when applied to home appliances, especially air conditioners. This would result in slow startup of functions such as cooling, air deflector control, or fan operation, thus affecting the user experience. The present invention injects an AC current with preset parameters into the motor, ensuring that the current flowing through the sampling resistor is also AC. Compared to injecting DC current, this more effectively simulates the actual current flow through the sampling resistor, improving the accuracy of each current sampling signal waveform.

[0058] Optionally, the injected alternating current is a sinusoidal current.

[0059] The expression for a sinusoidal current can be given by: i = I m sin(ωt+φ), where I m ω is the current amplitude, also known as the maximum current value, ω is the angular frequency, and φ is the initial phase. In this embodiment, φ can be 0.

[0060] Furthermore, the preset parameter is the effective current value of the alternating current.

[0061] The effective current value of an alternating current is its maximum current value. The ratio is approximately 0.707I. mSince the accuracy of the actual gain ratio is affected by the standardity of the injected sinusoidal current—that is, the more standard the signal waveform of the sinusoidal current and the more stable its effective value—the more accurate the actual gain ratio will be. Furthermore, AC power generation circuits or devices that can generate and stably output standard sinusoidal current are relatively mature, thus effectively reducing the difficulty of achieving high accuracy in the actual gain ratio.

[0062] Step 400: Obtain the actual resistance value of the sampling resistor in each current sampling circuit and the preset parameters of the AC current, and determine the actual gain ratio of each current sampling circuit based on the preset parameters of the AC current, the actual resistance value of the sampling resistor in each current sampling circuit, and the current sampling signal waveform output by each current sampling circuit.

[0063] In this embodiment, the main control unit can obtain preset parameters of the output AC current by communicating with the AC power generation circuit or device. The method for obtaining the actual resistance value of each sampling resistor can refer to the above embodiment, and will not be repeated here. It is understood that, referring to... Figure 6 Since the injected current is sinusoidal, the waveform of each current sampling signal also exhibits a sinusoidal pattern that changes with time, but is affected by the DC bias voltage V in the operational amplifier circuit. offset Due to the influence of this, the instantaneous value of the current sampling signal waveform at T=0 is not 0V, but rather V. offset The expression for the current sampling signal waveform can be: V out =V m sin(ωt+φ)+V offset V m The voltage amplitude, also known as V offset =(V peak+ +V peak -) / 2,V peak+ V is the maximum signal value of the current sampling signal waveform. peak- This represents the minimum signal value of the current sampling signal waveform. Since the current sampling signal is a voltage signal, therefore V... peak+ and V peak- These are also the maximum and minimum voltage values ​​of the current sampling signal waveform, respectively.

[0064] Based on the working principle of operational amplifier circuits, the gain ratio calculation formula for current sampling circuits is: G = (V peak+ -V peak- ) / V s V s =I s *R s V s I is the terminal voltage of the sampling resistor in the current sampling circuit. s R is the effective current value of the injected alternating current. sLet G be the actual resistance value of the sampling resistor in the current sampling circuit. Therefore, the expression for the actual gain ratio of the current sampling circuit can be simplified to: G = (V peak+ -V peak- ) / (I s *R w ).

[0065] Therefore, step 400 can specifically be as follows: based on the waveforms of each current sampling signal, determine the maximum and minimum signal values ​​of each current sampling signal waveform, and perform a difference operation on the maximum and minimum signal values ​​of each current sampling signal waveform to obtain the corresponding difference operation results; and also perform a product operation on the effective current value of the AC current and the actual resistance value of the sampling resistor in each current sampling circuit to obtain the corresponding product operation results; finally, perform a ratio operation on each difference operation result and the corresponding product operation result, so that after obtaining each ratio operation result, the corresponding ratio operation result is used as the actual gain ratio of the current sampling circuit where the sampling resistor is located, thereby realizing the determination of the actual gain ratio of each current sampling circuit.

[0066] Reference Figure 1 In one embodiment of the present invention, in step S100: based on the actual gain ratio of each current sampling circuit and the current sampling signal output by each current sampling circuit, the terminal voltage of the sampling resistor in each current sampling circuit is determined, specifically as follows:

[0067] The ratio of the current sampling signal output by each current sampling circuit to the actual gain ratio of that current sampling circuit is used as the terminal voltage of the sampling resistor in that current sampling circuit.

[0068] The main control unit converts each current sampling signal into a digital signal and then analyzes and processes the digital signal to obtain the voltage value corresponding to each current sampling signal, i.e., the output voltage of each current sampling circuit. As the operational amplifier circuit works, the product of the terminal voltage of each current sampling circuit and the actual gain ratio of that current sampling circuit is the output voltage of that current sampling circuit. Therefore, the main control unit can perform a ratio calculation between the voltage value corresponding to each current sampling signal and the actual gain ratio of the output current sampling circuit to reconstruct the terminal voltage of the sampling resistor in that current sampling circuit, thereby determining the terminal voltage of the sampling resistor in each current sampling circuit.

[0069] This invention also proposes a motor assembly that can be applied in household appliances and used to implement the aforementioned motor current sampling method. The specific steps of this motor current sampling method are as described in the above embodiments. Since this motor assembly adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be elaborated upon here.

[0070] Reference Figure 3 In one embodiment of the present invention, the motor assembly includes

[0071] Electric motor;

[0072] Inverter module 10 has a three-phase bridge arm circuit, and the output terminal of each phase bridge arm circuit is connected to one phase input terminal of the motor;

[0073] At least two current sampling circuits 20, each current sampling circuit 20 having a current sampling resistor (Ru, Rw, Rv), each sampling resistor (Ru, Rw, Rv) being connected to a phase bridge arm circuit, each current sampling circuit 20 being used to sample the current on the connected bridge arm circuit and output a corresponding current sampling signal;

[0074] The main control unit 30 is connected to multiple controlled terminals of the inverter module 10 and the output terminal of each current sampling circuit 20. The main control unit 30 is used to acquire the actual gain ratio of each current sampling circuit 20 and the current sampling signal output by each current sampling circuit 20; based on the actual gain ratio and the current sampling signal output by each current sampling circuit 20, it determines the terminal voltage of the sampling resistors (Ru, Rw, Rv) in each current sampling circuit 20; and acquires the actual resistance value of the sampling resistors (Ru, Rw, Rv) in each current sampling circuit 20, and determines the three-phase current of the motor based on the terminal voltage (Ru, Rw, Rv) of the sampling resistors in each current sampling circuit 20 and the actual resistance value of the sampling resistors (Ru, Rw, Rv) in the corresponding current sampling circuit 20.

[0075] In this embodiment, the motor can be a permanent magnet synchronous motor (PMSM), specifically an open-winding motor.

[0076] One end of the three-phase bridge arm circuit can be connected to the positive DC bus, and the other end can be connected to the negative DC bus, respectively, for receiving the DC voltage Udc transmitted from the positive and negative DC buses. Each three-phase bridge arm can have at least one switching transistor (U+, V+, W+, U-, V-, W-). The controlled terminals of each switching transistor (U+, V+, W+, U-, V-, W-) are the multiple controlled terminals of the inverter module 10. Each switching transistor (U+, V+, W+, U-, V-, W-) can be turned on / off according to a preset timing sequence under the control of the main control unit 30, thereby converting the DC voltage Udc received by the inverter module 10 into a three-phase AC voltage and outputting it to the three-phase input terminals of the motor, forming a three-phase AC current under the action of the three-phase winding load in the motor. In other words, at any operating moment of the motor, the three-phase winding load of the motor can form three current loops with the three-phase bridge arm circuit. Figure 5 In the embodiment shown, the inverter module 10 is a three-phase full-bridge inverter circuit.

[0077] The number of current sampling circuits 20 is at least two. The sampling resistors (Ru, Rw, Rv) in each current sampling circuit 20 can be located between a phase bridge arm circuit and the positive or negative DC bus. When the phase bridge arm circuit forms a current loop with the motor, the resistors generate corresponding terminal voltages across themselves based on the flowing current, which serve as the input voltage of their respective current sampling circuits 20. Each current sampling circuit 20 can amplify the input voltage and output it as a current sampling signal to the main control unit 30, allowing the main control unit 30 to determine the three-phase current of the motor based on the multiple current sampling signals received.

[0078] The main control unit 30 can be a microprocessor such as an MCU, DSP, or FPGA; alternatively, it can be a dedicated main control chip, which is not limited here. The main control unit 30 can determine the three-phase current of the motor based on the input multi-channel current sampling signals and can run a pre-integrated motor control algorithm to generate and output multiple corresponding switching transistor drive signals to the inverter module 10 based on the determined three-phase motor current. This allows for negative feedback control of the motor by controlling the three-phase AC voltage output from the inverter module 10 to the motor. When there are three current sampling circuits, the current values ​​flowing through the sampling resistors in each of the three current sampling circuits can be used as the real-time current values ​​of the three-phase motor current, thereby determining the three-phase current of the motor. When the current sampling circuit has two channels, since the sum of the current values ​​of the three-phase AC at any given moment is 0, the main control unit can first sum the current values ​​flowing through the two sampling resistors, then perform a difference operation between the sum operation result and the 0 value, and use the difference operation result as the real-time current value of the third phase AC. The current values ​​flowing through the two sampling resistors can then be used as the real-time current values ​​of the other two phase AC, thus realizing the determination of the three-phase current of the motor.

[0079] Reference Figure 4 The main control unit 30 may include a memory 101, a processor 102, and a motor current sampling program stored in the memory 101 and executable on the processor 102. When the processor 102 executes the motor current sampling program, it implements the motor current sampling method described above. The memory 101 may be a high-speed RAM or a stable, non-volatile memory, such as a disk drive. Optionally, the memory 101 may also be a storage device independent of the main control unit 30. The processor 102 may be a CPU. The memory 101 and the processor 102 are connected via a communication bus 103, which may be a UART bus or an I2C bus. It is understood that the main control unit 30 may also be implemented using the main control section of the device in which it is located. In this case, the main control unit 30 may also contain other related programs to drive other functional modules in the device.

[0080] In another embodiment, the motor is an open-winding motor. In the open-winding motor, both ends of the three-phase stator windings are open-circuited and connected one-to-one with the three-phase output terminals of two inverter modules 10. The two inverter modules 10 can be connected to the main control unit 30 respectively. In this case, the current sampling circuit 20 has at least four channels, with at least two channels used to detect the three-phase current output from one inverter module 10 to the motor, and at least two other channels used to detect the three-phase current output from the other inverter module 10 to the motor. Since the motor control algorithm for open-winding motors has higher requirements for the distortion of the current sampling signal, the technical solution of this invention can effectively improve the control accuracy of open-winding motors, thereby facilitating their application in household appliances.

[0081] Reference Figure 5 In one embodiment of the present invention, each current sampling circuit 20 further includes:

[0082] Operational amplifier circuit 21 has its first input terminal connected to one end of the sampling resistor (Ru, Rw, Rv), its second input terminal connected to the other end of the sampling resistor (Ru, Rw, Rv), and its output terminal connected to the main control unit 30.

[0083] The voltage across the sampling resistors (Ru, Rw, Rv) is the input voltage of the current sampling circuit 20, and the voltage across the sampling resistors (Ru, Rw, Rv) is a differential signal. The operational amplifier circuit 21 amplifies the input differential signal and outputs it to the main control unit 30. This prevents the main control unit 30 from being unable to receive and identify current sampling signals with small amplitudes, thus improving control accuracy during motor start-up. It can be understood that the gain ratio of the operational amplifier circuit 21 is the same as the gain ratio of the current sampling circuit 20.

[0084] Optionally, the operational amplifier circuit 21 includes: a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a first operational amplifier A1. The output terminal of the first operational amplifier A1 is the output terminal of the current sampling circuit 20. The output terminal of the first operational amplifier A1 is connected to the inverting input via the fourth resistor R4. The non-inverting input of the first operational amplifier A1 is connected to one end of the sampling resistors (Ru, Rw, Rv) in the current sampling circuit 20 via the first resistor. The inverting input of the first operational amplifier A1 is connected to the other end of the sampling resistors (Ru, Rw, Rv) in the current sampling circuit 20 via the second resistor. The non-inverting input of the first operational amplifier is also connected to a preset bias voltage Voffset via the third resistor R3.

[0085] The first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, and the first operational amplifier A1 form a differential amplifier circuit. This allows the first operational amplifier circuit 21 to amplify the input differential signal and output a single-ended current sampling signal to the main control unit 30. The fourth resistor R4 forms a negative feedback loop for the first operational amplifier A1, feeding its output signal back to its inverting input. This allows the first operational amplifier A1 to adjust its output signal using the feedback signal at the inverting input, improving the stability of the current sampling signal.

[0086] This section uses the current sampling circuit 20 connected to the W-phase bridge arm circuit as an example to explain the distortion of the output signal of the current sampling circuit 20. For details, please refer to the appendix. Figure 5 As can be seen from the working principle of the current sampling circuit 20, the output signal V out With sampling resistor R w Terminal voltage U w The relationship is: V out =(U w *R2 / R1)+V offset The main control unit 30 can, based on the collected V out Combined with the pre-stored DC bias voltage VoffsetV offset Calculate U w =(V out -V offset This is calculated as R1 / R2, thus enabling the sampling resistor R to be sampled. w Voltage U at both ends w The calculation can be performed using formula I. w =U w / R w The phase current I of phase W was calculated. w When there are parameter errors in the components, for example, if a change in one of the resistors R1 causes an imbalance in the current sampling circuit 20, the expression for the output voltage is: It can be seen that the actual gain ratio and the preset bias voltage Voffset of the current sampling circuit 20 deviate from the ideal preset value. Furthermore, since the parameter error is unknown, the W-phase current calculated by the main control unit 30 based on the preset gain ratio and the preset bias voltage Voffset has a large error compared with the actual value, which in turn affects the control accuracy of the motor.

[0087] This invention also proposes a household appliance that includes a motor assembly. The specific structure of the motor assembly is as described in the above embodiments. Since this household appliance adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated upon here. The household appliance can be an air conditioner, refrigerator, fan, air cooler, or other device with a motor, and is not limited thereto.

[0088] The above are merely optional embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for sampling motor current, characterized in that, The method for sampling the motor current includes: Obtain the actual gain ratio and the current sampling signal output by each current sampling circuit. Based on the actual gain ratio and the current sampling signal output by each current sampling circuit, determine the terminal voltage of the sampling resistor in each current sampling circuit; and, Obtain the actual resistance value of the sampling resistor in each current sampling circuit, and determine the three-phase current of the motor based on the terminal voltage of the sampling resistor in each current sampling circuit and the actual resistance value of the sampling resistor in the corresponding current sampling circuit. The method for sampling the motor current, before obtaining the actual gain ratio of each current sampling circuit, further includes: Inject an AC current with preset parameters into the motor and obtain the current sampling signal waveform output by each current sampling circuit after injection. Obtain the preset parameters of the AC current and the actual resistance value of the sampling resistor in each current sampling circuit. Based on the actual resistance value of the sampling resistor in each current sampling circuit, the current sampling signal waveform output by each current sampling circuit, and the preset parameters of the AC current, determine the actual gain ratio of each current sampling circuit.

2. The method for sampling motor current as described in claim 1, characterized in that, The alternating current is a sinusoidal current.

3. The method for sampling motor current as described in claim 2, characterized in that, The preset parameter is the effective current value of the alternating current.

4. The method for sampling motor current as described in claim 1, characterized in that, Based on the actual resistance value of the sampling resistor in each current sampling circuit, the current sampling signal waveform output by each current sampling circuit, and the preset parameters of the AC current, the actual gain ratio of each current sampling circuit is determined as follows: The difference between the maximum and minimum signal values ​​in each current sampling signal waveform is compared with the product of the effective current value of the AC current and the actual resistance value of each sampling resistor. The result of the ratio calculation is used as the actual gain ratio of the corresponding current sampling circuit.

5. The method for sampling motor current as described in claim 1, characterized in that, Based on the actual gain ratio of each current sampling circuit and the current sampling signal output by each current sampling circuit, the terminal voltage of the sampling resistor in each current sampling circuit is determined as follows: The ratio of the current sampling signal output by each current sampling circuit to the actual gain ratio of that current sampling circuit is used as the terminal voltage of the sampling resistor in that current sampling circuit.

6. The method for sampling motor current as described in claim 1, characterized in that, The three-phase current of the motor is determined based on the terminal voltage of the sampling resistor in each current sampling circuit and the actual resistance value of the sampling resistor in the corresponding current sampling circuit, specifically as follows: The ratio of the terminal voltage of each sampling resistor to the actual resistance value of that sampling resistor is used as one phase current of the motor.

7. A motor assembly, characterized in that, The motor assembly includes: Electric motor; The inverter module has a three-phase bridge arm circuit, and the output terminal of each phase bridge arm circuit is connected to one phase input terminal of the motor. At least two current sampling circuits, each current sampling circuit having a sampling resistor, each sampling resistor being connected to one phase of the bridge arm circuit, each current sampling circuit being used to sample the current on the connected bridge arm circuit and output a corresponding current sampling signal; The main control unit is connected to multiple controlled terminals of the inverter module and the output terminal of each current sampling circuit, and the main control unit is used to implement the motor current sampling method as described in any one of claims 1 to 6.

8. The motor assembly as claimed in claim 7, characterized in that, Each of the aforementioned current sampling circuits further includes: An operational amplifier circuit is provided, wherein the first input terminal and the second input terminal of the operational amplifier circuit are respectively connected to the two ends of the sampling resistor, and the output terminal of the operational amplifier circuit is connected to the main control unit.

9. The motor assembly as claimed in claim 8, characterized in that, The operational amplifier circuit includes: The system comprises a first resistor, a second resistor, a third resistor, a fourth resistor, and a first operational amplifier. The first end of the first resistor and the first end of the second resistor are respectively connected to the two ends of the sampling resistor in the current sampling circuit. The second ends of the first resistor and the second resistor are respectively connected to the non-inverting and inverting inputs of the first operational amplifier. The second end of the first resistor is also connected to a preset bias voltage via the third resistor. The output terminal of the first operational amplifier is connected to the inverting input via the fourth resistor. The output terminal of the first operational amplifier is the output terminal of the current sampling circuit.

10. A household appliance, characterized in that, The home appliance includes the motor assembly as described in claim 9.

11. The household appliance as described in claim 10, characterized in that, The household appliance in question is an air conditioner.

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