CN116545331A - Brushless motor current sampling method and electronic device - Google Patents

Abstract

The application provides a current sampling method of a brushless motor and electronic equipment. The current sampling method comprises the following steps: the duty ratio of each phase of the corresponding three-phase inverter circuit in the current modulation period is obtained; adjusting the duty ratio of each phase to output SVPWM waves according to the adjusted duty ratio of each phase; the duty ratio of each phase after adjustment is different, and the relation between the duty ratio D of each phase after adjustment and a preset set R satisfies D epsilon R (D=100%) (D=0%) (k 1 is less than or equal to D is less than or equal to k 2), the product of k1 and the modulation period is greater than the minimum current sampling period, and the product of (100% -k 2) and the modulation period is greater than the minimum current sampling period; at the midpoint of the modulation period, reversing the polarity of two of the three-phase SVPWM waves; and sampling twice according to the three-phase SVPWM wave to obtain three-phase current flowing through the brushless motor, wherein the sampling time of at least one of the two times of sampling is the midpoint of the modulation period.

Description

Brushless motor current sampling method and electronic device

Technical Field

The present disclosure relates to the field of motor control, and in particular, to a current sampling method and an electronic device for a brushless motor.

Background

The Field-Oriented Control (FOC) method based on current sampling is a high-efficiency drive Control method of a brushless motor. In order to save the motor control cost, a single-resistance current sampling method is generally adopted to control the motor. For example, seven-segment SVPWM modulation methods are currently often employed to achieve single resistance current sampling. When each state is switched, only one phase current changes, so that according to kirchhoff's law, only two phase currents are required to be collected at the same time, and three-phase current can be sampled. However, by adopting the sampling method, the 3 paths of currents can be more accurately restored after 4 times of sampling and averaging are carried out in one PWM period, and the sampling frequency is higher; and the sampling time is required to be adjusted for multiple times, so that the algorithm complexity is high.

Disclosure of Invention

In view of this, the present application provides a current sampling method and an electronic device for a brushless motor, which can reduce the sampling times and have lower algorithm complexity.

The first aspect of the present application provides a current sampling method of a brushless motor, where the brushless motor is electrically connected to a three-phase inverter circuit, and sampling resistors are connected in series on bus bars of the three-phase inverter circuit, and the sampling resistors are used for sampling to obtain a current flowing through the brushless motor. The current sampling method comprises the following steps: the duty ratio of each phase of the corresponding three-phase inverter circuit in the current modulation period is obtained; adjusting the duty ratio of each phase to output SVPWM waves according to the adjusted duty ratio of each phase; the duty ratio of each phase after adjustment is different, and the relation between the duty ratio D of each phase after adjustment and a preset set R satisfies D epsilon R (D=100%) (D=0%) (k 1 is less than or equal to D is less than or equal to k 2), the product of k1 and the modulation period is greater than the minimum current sampling period, and the product of (100% -k 2) and the modulation period is greater than the minimum current sampling period; at the midpoint of the modulation period, reversing the polarity of two of the three-phase SVPWM waves; and sampling twice according to the three-phase SVPWM wave to obtain three-phase current flowing through the brushless motor, wherein the sampling time of at least one of the two times of sampling is the midpoint of the modulation period.

In one embodiment, adjusting the duty cycle of each phase to output the SVPWM wave according to the adjusted duty cycle of each phase comprises: when the duty ratio D of each phase meets k 1-D-k 2, taking the duty ratio of any one phase in the three-phase inverter circuit as a first duty ratio, wherein the first duty ratio is 100% or 0%, and taking the duty ratios of the other two phases as a second duty ratio and a third duty ratio respectively; outputting a three-phase SVPWM wave according to the first duty cycle, the second duty cycle and the third duty cycle; or when the duty ratio of each phase is 0% or 100% and the duty ratio of the other two phases meets k 1-D-k 2, taking the duty ratio of 0% or 100 in the duty ratio of each phase as a first duty ratio, and taking the duty ratio of the other two phases as a second duty ratio and a third duty ratio respectively; and outputting the three-phase SVPWM waves according to the first duty cycle, the second duty cycle and the third duty cycle.

In one embodiment, the duty ratio of each phase of the corresponding three-phase inverter circuit includes a first initial duty ratio D1, a second initial duty ratio D2, and a third initial duty ratio D3, and adjusting the duty ratio of each phase to output the SVPWM wave according to the adjusted duty ratio of each phase includes: when the first initial duty ratio D1 satisfies that k1 is less than or equal to D1 and less than or equal to k2, and the second initial duty ratio D2 and the third initial duty ratio D3 are both less than k1, the first initial duty ratio D1 is adjusted to be 100 percent and is used as a first duty ratio D4, and the second initial duty ratio D2 and the third initial duty ratio D3 are respectively adjusted to be a second duty ratio D5 and a third duty ratio D6; and the second duty cycle D5 satisfies: d5 =d2+ (100-D1); the third duty cycle D6 satisfies: d6 =d3+ (100-D1).

In one embodiment, sampling twice from a three-phase SVPWM wave to obtain three-phase current flowing through a brushless motor comprises: performing an inverting operation on one phase of the two-phase SVPWM waves output according to the second and third duty ratios; sampling is carried out according to the three-phase SVPWM wave after the inversion operation is carried out, and the sampling time of the other sampling is the starting point of the modulation period.

In one embodiment, adjusting the duty cycle of each phase to output the SVPWM wave according to the adjusted duty cycle of each phase comprises: when the duty ratio of each phase is smaller than k1, comparing the duty ratios of each phase to obtain a first initial duty ratio D1, a second initial duty ratio D2 and a third initial duty ratio D3, wherein the first initial duty ratio D1 is the minimum value in the duty ratios of each phase, the first initial duty ratio D1 is adjusted to be a first duty ratio D4, and the value of the first duty ratio D4 meets that k1 is less than or equal to D4 is less than or equal to k2; the second initial duty ratio D2 and the third initial duty ratio D3 are adjusted to be a second duty ratio D5 and a third duty ratio D6 respectively, wherein the second duty ratio D5 meets the following conditions: d5 =d2+ (D4-D1); the third duty cycle D6 satisfies: d6 =d3+ (D4-D1), and k1+.d5+.k2, k1+.d6+.k2; and outputting the three-phase SVPWM waves according to the first duty ratio D4, the second duty ratio D5 and the third duty ratio D6.

In one embodiment, sampling twice from the three-phase SVPWM wave to obtain three-phase current flowing through the brushless motor comprises: selecting any one phase of the three-phase SVPWM waves for inverting operation to generate a first group of SVPWM waves; performing first sampling according to the first group of SVPWM waves, wherein the sampling moment of the first sampling is the midpoint of the modulation period of the corresponding first group of SVPWM waves; selecting another phase of the first set of SVPWM waves to perform an inversion operation again to generate a second set of SVPWM waves; and performing second sampling according to the second set of SVPWM waves, wherein the sampling moment of the second sampling is the midpoint of the modulation period of the corresponding second set of SVPWM waves.

In one embodiment, the duty cycle of each phase of the corresponding three-phase inverter circuit includes a first initial duty cycle, a second initial duty cycle, and a third initial duty cycle, and adjusting the duty cycle of each phase to output the SVPWM wave according to the adjusted duty cycle of each phase includes: when a first initial duty ratio smaller than k1 and a second initial duty ratio larger than k2 exist in the duty ratios of the phases, the first initial duty ratio is adjusted to be the first duty ratio, and the first duty ratio is 0%; adjusting the second initial duty cycle to be a second duty cycle, wherein the second duty cycle is 100%; adjusting the third initial duty cycle to be a third duty cycle, wherein the third duty cycle is greater than k1 and less than k2; and outputting the three-phase SVPWM waves according to the first duty cycle, the second duty cycle and the third duty cycle.

In one embodiment, sampling twice from the three-phase SVPWM wave to obtain three-phase current flowing through the brushless motor comprises: performing twice sampling according to the three-phase SVPWM wave, wherein one sampling time in the twice sampling is the starting point of a modulation period; the other of the two samples is at the midpoint of the modulation period.

A second aspect of the present application provides an electronic device comprising a processor and a brushless motor. The processor is electrically connected to the brushless motor, and the processor is used for executing the current sampling method according to any one of the above, and controlling the working state of the brushless motor according to the current sampling result.

According to the current sampling method of the brushless motor, the obtained three-phase duty ratio is adjusted, so that the adjusted three-phase duty ratio meets the preset relation, and when the duty ratio is not 100% or 0%, the sampling interval is larger than or equal to the minimum current sampling period, and the probability of sampling errors is reduced; the current sampling method also generates three-phase SVPWM waves according to the adjusted three-phase duty ratio, and at the midpoint of the modulation period, the polarities of two phases in the three-phase SVPWM waves are opposite to each other so as to primarily exclude some states in which current cannot be detected, thereby increasing the sampling success rate; thus, when the three-phase SVPWM wave is sampled twice to reconstruct the three-phase current, the three-phase SVPWM wave can be directly sampled at the midpoint of the modulation period, the sampling times are small, complex calculation on sampling time is not needed, and the probability of interference sampling due to the close duty ratio of the two-phase current is reduced. In summary, compared with the existing single-resistance current sampling method, the current sampling method provided by the application has the advantages of less sampling times, no need of adjusting sampling time for multiple times, lower algorithm complexity, less consumption of chip resources and capability of effectively improving current sampling efficiency and current sampling accuracy.

Drawings

Fig. 1 is a functional block diagram of a motor driving system according to an embodiment of the present application.

Fig. 2 is a schematic connection diagram of a three-phase inverter circuit and a brushless motor according to an embodiment of the present application.

Fig. 3 is a schematic diagram of a 7-segment SVPWM wave generated by the related art.

Fig. 4 is a flow chart of a current sampling method of a brushless motor according to an embodiment of the present application.

Fig. 5 is a schematic diagram of a SVPWM wave generated in the related art.

Fig. 6 is a flowchart illustrating a first sub-step of step S430 according to an embodiment of the present application.

Fig. 7A is a three-phase SVPWM wave generated according to the duty ratio of each phase of the corresponding three-phase inverter circuit in the current modulation period in an embodiment of the present application.

Fig. 7B is a three-phase SVPWM wave generated after modulating the one-phase duty cycle of fig. 7A to 100%.

Fig. 7C shows a three-phase SVPWM wave output after the duty ratio of each phase is adjusted.

Fig. 8 is a sector switching diagram in the motor control process in the related art.

Fig. 9 is a schematic diagram showing a change of duty cycle during a sector switching process in the related art.

Fig. 10 is a flowchart illustrating a first sub-step of step S420 according to an embodiment of the present application.

Fig. 11 is a flowchart illustrating a second sub-step of step S430 according to an embodiment of the present application.

FIG. 12 is a schematic diagram of two sets of SVPWM waves generated in an embodiment of the present application.

Fig. 13 is a flowchart illustrating a second sub-step of step S420 according to an embodiment of the present application.

Fig. 14 is a functional block diagram of an electronic device according to an embodiment of the present application.

Fig. 15 is a block diagram of a current sampling apparatus according to an embodiment of the present application.

Detailed Description

The following description of the technical solutions in the embodiments of the present application will be made with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments.

It is noted that when one component is considered to be "connected" to another component, it may be directly connected to the other component or intervening components may also be present. When an element is referred to as being "disposed" on another element, it can be directly on the other element or intervening elements may also be present. The terms "top," "bottom," "upper," "lower," "left," "right," "front," "rear," and the like are used herein for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

Some embodiments will be described below with reference to the accompanying drawings. The following embodiments and features of the embodiments may be combined with each other without conflict.

Referring to fig. 1, the motor driving system 10 includes a processor 110, a pre-driver module 120, a three-phase inverter circuit 130, a brushless motor 140, an angle measurement module 150, and a current sampling module 160.

Specifically, the angle measurement module 150 is electrically connected between the brushless motor 140 and the processor 110, and is configured to measure the angular position information of the rotor in the brushless motor 140 in real time, and output the angular position information to the processor 110.

The current sampling module 160 is connected to the three-phase inverter circuit 130 and the processor 110, respectively, and is configured to sample three-phase currents of the brushless motor 140 through the three-phase inverter circuit 130, and amplify and output the three-phase currents to the processor 110.

The processor 110 is connected to a pre-driver module 120, and the pre-driver module 120 is electrically connected to a three-phase inverter circuit 130. The processor 110 adjusts waveforms of three space vector pulse width modulation (Space Vector Pulse Width Modulation, SVPWM) waves in real time according to the angular position information and the three phase currents, and outputs the adjusted waveforms of three SVPWM waves to the pre-driver module 120. The pre-driver module 120 receives waveforms of three paths of SVPWM waves from the processor 110, and generates corresponding three paths of waveforms to drive the on and off of the MOS transistors in the three-phase inverter circuit 130. The three-phase inverter circuit 130 is connected to the brushless motor 140, and the three-phase inverter circuit 130 outputs three ac voltage signals, thereby driving the brushless motor 140 to operate.

It should be understood that fig. 1 is only a schematic diagram of a motor driving system according to an embodiment of the present application, and in other embodiments, the motor driving system may not include an angle measurement module, so as to estimate a position of a rotor of the brushless motor 140 according to a current sampling result, thereby driving the brushless motor 140.

With continued reference to fig. 2, specifically, the three-phase inverter circuit 130 includes an a-phase bridge arm, a B-phase bridge arm, and a C-phase bridge arm, where the a-phase bridge arm includes an upper pipe VT1 and a lower pipe VT4, the B-phase bridge arm includes an upper pipe VT3 and a lower pipe VT6, and the C-phase bridge arm includes an upper pipe VT5 and a lower pipe VT2. The first end of the upper tube VT1 is connected with a positive direct current bus U+, the first end of the lower tube VT4 is connected with the second end of the upper tube VT1, and the second end of the lower tube VT4 is connected with a negative direct current bus U-; the first end of the upper tube VT3 is connected with a positive direct current bus U+, the first end of the lower tube VT6 is connected with the second end of the upper tube VT3, and the second end of the lower tube VT6 is connected with a negative direct current bus U-; the first end of the upper tube VT5 is connected with a positive direct current bus U+, the first end of the lower tube VT2 is connected with the second end of the upper tube VT5, and the second end of the lower tube VT2 is connected with a negative direct current bus U-; the control end CR1 of the upper tube VT1, the control end CR2 of the lower tube VT4, the control end CR3 of the upper tube VT3, the control end CR4 of the lower tube VT6, the control end CR5 of the upper tube VT5, and the control end CR6 of the lower tube VT2 are respectively connected with the pre-driver module 120, and the pre-driver module 120 controls the on or off of the six switching tubes by outputting corresponding waveforms, and only one of the upper tube or the lower tube in the same phase bridge arm is conducted in the same control period, so that the direct current on the direct current bus is inverted into the alternating current, and the alternating current is provided for the brushless motor 140 to drive the brushless motor 140 to work. The source of the direct current on the direct current bus may be a battery or may be obtained by rectifying alternating current, which is not limited herein, and a direct current bus capacitor (not shown) is disposed between the positive direct current bus and the negative direct current bus for storing energy and stabilizing voltage. In the present application, the upper pipe on and lower pipe off are defined as state 1, and the upper pipe off and lower pipe on are defined as state 0.

In this application, referring to fig. 2, the current sampling module 160 includes a sampling resistor R0 and an operational amplifier OP. A sampling resistor R0 is connected in series to a bus of the three-phase inverter circuit 130 to sample by the sampling resistor R0 to obtain a current flowing through the brushless motor 140. The two input terminals of the operational amplifier OP are electrically connected to two ends of the sampling resistor R0, respectively, and are used for amplifying the current sampled by the sampling resistor R0 to output to the processor 110. It is understood that the processor 110 may perform analog-digital conversion processing, filtering processing, etc. on the received current data to facilitate the next operation.

Further, a Field-Oriented Control (FOC) method based on current sampling is an efficient drive Control method of a brushless motor. To save motor control costs, the motor is typically sampled using a single resistance current sampling method as shown in fig. 2, and seven segments of SVPWM waves as shown in fig. 3 are generated to achieve current sampling. In fig. 3, PHASE a represents the SVPWM wave corresponding to a, PHASE B represents the SVPWM wave corresponding to B, and PHASE C represents the SVPWM wave corresponding to C. In fig. 3, only one phase current changes when each state is switched, so that according to kirchhoff's law, only two phase currents need to be collected at the same time, and sampling of three phase currents can be achieved. However, by adopting the sampling method, the 3 paths of currents can be more accurately restored after 4 times of sampling and averaging are carried out in one PWM period, and the sampling frequency is higher; and the sampling time is required to be adjusted for multiple times, so that the algorithm complexity is high.

Based on the above, the current sampling method of the brushless motor is provided, the sampling time is less, the algorithm complexity is lower, and the current sampling efficiency can be improved.

Referring to fig. 4, fig. 4 is a flow chart of a current sampling method of a brushless motor according to an embodiment of the disclosure. It will be appreciated that the sampling method may be performed by the processor 110 shown in fig. 1. Specifically, the sampling method comprises the following steps:

step S410: and acquiring the duty ratio of each phase of the corresponding three-phase inverter circuit in the current modulation period.

In step S410, the modulation period refers to a space vector pulse width modulation period.

It is understood that the three SVPWM waves output by the processor 110 correspond to each phase leg (a phase, B phase, and C phase) in the three-phase inverter circuit. And the duty cycle of each phase refers to the ratio of the pulse width of each phase SVPWM wave to the modulation period. For example, when the duty ratio of the SVPWM wave corresponding to the a-phase bridge arm is 100%, the pulse width of the SVPWM wave is equal to the duration of the modulation period, and the upper switching tube on the a-phase bridge arm is kept in a state of being always turned on in the modulation period (delay error is ignored).

As can be appreciated, the processor 110 adjusts the duty ratio of the SVPWM wave corresponding to each phase leg in each modulation period, so as to control the on time corresponding to the switching tube on each leg of the three-phase inverter circuit 130, thereby controlling the moment, the rotation speed, the position, and the like of the brushless motor 140.

Specifically, the duty cycle may be calculated by the processor 110 according to a preset rule; or the duty cycle may be a preset duty cycle, and the processor 110 selects a corresponding preset duty cycle according to a preset trigger rule. In this manner, step S410 may be implemented by acquiring the duty cycle of each phase in the corresponding three-phase inverter circuit 130 in the current modulation period stored in the register or the memory.

Step S420: adjusting the duty ratio of each phase to output SVPWM waves according to the adjusted duty ratio of each phase; the relation between the duty ratio D of each phase after adjustment and the preset set R satisfies D e R, (D=100%). U.S. (D=0%) (k 1 is less than or equal to D is less than or equal to k 2), the product of k1 and the modulation period is greater than the minimum current sampling period, and the product of (100% -k 2) and the modulation period is greater than the minimum current sampling period.

Understandably, with space vector pulse width modulation techniques, the amplitude of each pulse is equal. Thus, in step S420, the change of the duty ratio does not affect the magnitude of the current sampled at each sampling instant. Moreover, since the switching tubes in the three-phase inverter circuit 130 have only two states of on (conducting) and off (disconnecting), in the actual control process, the time of each modulation period is short, and the processor 110 keeps the duty ratio of each phase leg of the corresponding three-phase circuit unchanged in a plurality of continuous modulation periods, and the switching tubes in the three-phase inverter circuit 130 are controlled to be conducted or disconnected at a high frequency according to a preset duty ratio, so that stable control of the brushless motor 140 is realized. In this way, step S420 is actually to change the duty ratio of several modulation periods among a plurality of identical modulation periods, without affecting the overall control of the brushless motor 140.

Specifically, in step S420, the relation between the duty ratio D of each phase after adjustment and the preset set R satisfies dΣr, (d=100%) u (d=0%) u (k1+.dΣ2). That is, the duty ratio D of each phase after adjustment may be 100%, or 0%, or the duty ratio D may satisfy k1.ltoreq.D.ltoreq.k2.

In this embodiment, step S420 is a center alignment mode for the SVPWM wave output by the duty cycle adjustment, that is, the midpoint of the pulse width in the SVPWM wave overlaps with the midpoint of the modulation period. In the embodiment of the present application, in order to reduce the computational complexity of the sampling time, a specific point may be selected as the sampling time point, for example, a position near the start point, the end point, or the middle point of the modulation period. It is understood that the product of the duty cycle and the modulation period is the pulse width. Due to delay caused by a circuit, a certain sampling time is needed when the current is sampled. There is thus a minimum current sampling period, wherein sampling may not be achieved when the pulse width is less than the minimum current sampling period or when the pulse width is too large.

For example, referring to FIG. 5, in FIG. 5, PHASE A represents the corresponding SVPWM wave of A, PHASE B represents the corresponding SVPWM wave of B, and PHASE C represents the corresponding SVPWM wave of C. In fig. 5, the duty ratio of the B phase is relatively large, and the corresponding pulse width is relatively large, so when sampling is performed at the start of the modulation period, since the pulse width of the B phase is too large, a sampling interval formed between the start of the modulation period and the rising edge of the B phase is smaller than the minimum sampling time, and accurate sampling may not be possible. The duty cycle of phase C in fig. 5 is smaller and the corresponding pulse width is smaller, so that when sampling is performed at the midpoint of the modulation period, when the pulse width is smaller than the minimum sampling time, accurate sampling will not be caused.

Therefore, in the embodiment of the application, the product of k1 and the modulation period is limited to be larger than the minimum current sampling period, and the product of (100% -k 2) and the modulation period is limited to be larger than the minimum current sampling period, so that the pulse width of each phase of bridge arm after adjustment is not too small or too large, and further the sampling interval of each phase of bridge arm can meet the minimum current sampling period, thereby reducing the probability of sampling errors. It is appreciated that k1 and k2 may be adjusted based on the duration of the minimum current sampling period.

In summary, by executing step S420, the duty ratio of each phase is adjusted on one hand, and the adjusted duty ratio of each phase meets the preset relationship, so as to primarily reduce the probability of sampling error.

Step S430: at the midpoint of the modulation period, reversing the polarity of two of the three-phase SVPWM waves; and sampling twice according to the three-phase SVPWM wave to obtain three-phase current flowing through the brushless motor, wherein the sampling time of at least one of the two times of sampling is the midpoint of the modulation period.

In step 430, the three-phase SVPWM waves output according to the adjusted duty ratio are modulated such that polarities of two of the three-phase SVPWM waves are opposite at a midpoint of the modulation period. Thus, when sampling is performed at the midpoint of the modulation period, the average value does not need to be calculated through two times of sampling, and the probability of interference sampling due to the close duty ratio of the two-phase current can be reduced.

It is to be understood that in step S430, two sampling is performed by using the sampling resistor R0 according to the three-phase SVPWM wave to sample two phase currents in the three-phase currents of the brushless motor 140, respectively, and the third phase current is calculated based on the single-resistance current reconstruction technique, i.e. calculated according to the formula ia+ib+ic=0, where IA is the a-phase current of the motor, IB is the B-phase current of the motor, and IC is the C-phase current of the motor.

For example, referring to fig. 7A and 7C, fig. 7A is a three-phase SVPWM wave generated according to the duty ratio of each phase of the corresponding three-phase inverter circuit in the current modulation period. Fig. 7C shows three-phase SVPWM waves output after the duty ratios of the phases are adjusted according to step S420, and the polarities of two of the three-phase SVPWM waves are reversed at the midpoint of the modulation period. In fig. 7C, the three-phase SVPWM wave is sampled twice, where the first sampling instant is the start of the modulation period and the second sampling instant is at the midpoint of the modulation period. It should be understood that the first sampling time and the second sampling time herein do not indicate the order in which the sampling times occur, and the first sampling time and the second sampling time are only used to indicate different sampling times.

The state of each phase in the three-phase inverter circuit 130 obtained by sampling at the first sampling time is 011, that is, at the first sampling time, the upper tube VT1 is turned off corresponding to the a-phase bridge arm; corresponding to the B-phase bridge arm, the upper pipe VT3 is conducted; corresponding to phase C, the upper tube VT5 is conducted. Thus, according to the current reconstruction formula, the first sampling time is sampled to obtain-IA.

The state of each phase in the three-phase inverter circuit 130 obtained by sampling at the second sampling time is 101, that is, at the second sampling time, the upper tube VT1 is turned on corresponding to the a-phase bridge arm; corresponding to the B-phase bridge arm, the upper pipe VT3 is turned off; corresponding to phase C, the upper tube VT5 is conducted. Thus, according to the current reconstruction formula, the second sampling time can be sampled to obtain-IB. And then according to the current reconstruction formula, the current IC can be calculated.

It will be appreciated that, through the processing of step S420, at the midpoint of the modulation period, the polarities of the two phase SVPWM waves in the three phase SVPWM waves are opposite, so that the switching tube states including at least 1 and 0 at the midpoint of the modulation period can exclude the states that the three bridge arms are 000 (three lower tubes are conducting) or 111 (three upper tubes are conducting) and the current is not sampled. Thus, in step S430, sampling at the midpoint of the modulation period may sample a phase current without requiring complex computation of the sampling instant. In addition, compared with the existing 7-segment SVPWM sampling method, the sampling frequency which is set more by taking an average value can be reduced by directly sampling at the midpoint of the modulation period.

As can be appreciated, in step S430, the processor 110 controls the current sampling module 160 to sample the voltages at two ends of the sampling resistor R0 according to two preset sampling moments while outputting the three-phase SVPWM wave according to the adjusted duty ratio, so as to calculate the magnitudes of the currents of the two phase legs in the three-phase inverter circuit 130 by combining the waveforms of the three-phase SVPWM wave. Further, the processor 110 further calculates the current of the last phase leg in the three-phase inverter circuit 130 according to the current reconstruction technique.

In summary, according to the current sampling method of the brushless motor provided by the application, the obtained three-phase duty ratio is adjusted, so that when the adjusted three-phase duty ratio is not 100% or 0%, the sampling interval is greater than or equal to the minimum current sampling period, and the probability of sampling errors is reduced; the current sampling method also generates three-phase SVPWM waves according to the adjusted three-phase duty ratio, and at the midpoint of the modulation period, the polarities of two phases in the three-phase SVPWM waves are opposite to each other so as to primarily exclude some states in which current cannot be detected, thereby increasing the sampling success rate; thus, when the three-phase SVPWM wave is sampled twice to reconstruct the three-phase current, the three-phase SVPWM wave can be directly sampled at the midpoint of the modulation period, the sampling times are small, complex calculation on sampling time is not needed, and the probability of interference sampling due to the close duty ratio of the two-phase current is reduced. In summary, compared with the existing single-resistance current sampling method, the current sampling method provided by the application has the advantages of less sampling times, no need of adjusting sampling time for multiple times, lower algorithm complexity, less consumption of chip resources and capability of effectively improving current sampling efficiency and current sampling accuracy.

With continued reference to the following, in some embodiments, the present application further performs corresponding steps S420 and S430 according to the different duty ratios obtained in step S410.

Embodiment one:

in some embodiments, adjusting the duty cycle of each phase to output the SVPWM wave according to the adjusted duty cycle of each phase comprises:

when the duty ratio D of each phase meets k 1-D-k 2, taking the duty ratio of any one phase in the three-phase inverter circuit as a first duty ratio, wherein the first duty ratio is 100% or 0%, and taking the duty ratios of the other two phases as a second duty ratio and a third duty ratio respectively; and outputting the three-phase SVPWM waves according to the first duty cycle, the second duty cycle and the third duty cycle.

The duty cycle of each phase is understood to be the duty cycle of the three-phase legs (including a-phase leg, B-phase leg, and C-phase leg) in the three-phase inverter circuit 130.

For example, please refer again to fig. 7A-7C. In an embodiment, the duty ratios of the a-phase bridge arm, the B-phase bridge arm, and the C-phase bridge arm in the three-phase inverter circuit 130 are D1, D2, and D3, respectively, and D1, D2, and D3 each satisfy the interval defined by k1 and k 2. Fig. 7A is an initial SVPWM wave generated from the acquired duty cycle of the three-phase legs.

Then, the duty ratio D3 corresponding to the C-phase arm is selected as the first duty ratio, and adjusted to 100%.

The duty ratios D1 and D2 corresponding to the a-phase arm and the B-phase arm are respectively set as the second duty ratio and the third duty ratio.

And outputting the corresponding three-phase SVPWM waves according to the first duty ratio, the second duty ratio and the third duty ratio, so as to generate a three-phase SVPWM wave schematic diagram shown in FIG. 7B.

Further, referring to fig. 6, in some embodiments, sampling twice from the three-phase SVPWM wave to obtain three-phase currents flowing through the brushless motor 140 includes:

step S610: performing an inverting operation on one phase of the two-phase SVPWM waves output according to the second and third duty ratios;

step S620: sampling is carried out according to the three-phase SVPWM wave obtained after the inversion operation is carried out, and the sampling time of the other sampling is the starting point of the modulation period.

It is understood that in this application, the inversion operation is the SVPWM wave generated by delaying the phase of the corresponding SVPWM wave by 180 degrees.

For example, in one embodiment, an inversion operation is performed on the second phase SVPWM wave corresponding to the B phase leg to obtain the second phase SVPWM wave in fig. 7C. Thus, in the three-phase SVPWM wave illustrated in fig. 7C, the second-phase SVPWM wave is inverted from the first-phase SVPWM wave at the midpoint of the modulation period. Further, the three-phase SVPWM wave shown in fig. 7C is sampled. The first sampling time is the start point of the modulation period, and the state of the three-phase inverter circuit 130 corresponding to the first sampling time is 011 (i.e., at the first sampling time, the upper tube VT1 is turned off, the upper tube VT3 is turned on, and the upper tube VT5 is turned on), so that the first sampling time can be sampled to obtain-IA. The second sampling time is the midpoint of the modulation period, and the state of the three-phase inverter circuit 130 corresponding to the second sampling time is 101 (i.e. at the second sampling time, the upper tube VT1 is turned on, the upper tube VT3 is turned off and the upper tube VT5 is turned on), so that the second sampling time can be sampled to obtain-IB.

It will be appreciated that in some embodiments, the first sampling instant may be virtually any instant in the interval from the start of the modulation period to the rising edge (or falling edge) of any one of the three-phase SVPWM waves, and similarly, the second sampling instant may also be any instant in the interval formed by the two rising edges (or two falling edges) nearest the midpoint of the modulation period, due to circuit delays or errors in the motor drive system 10, etc.

Thus, by executing the steps, when the duty ratio D of three phases meets k1 and is less than or equal to D and is less than or equal to k2, the sampling current can be obtained quickly and conveniently without calculating the sampling moment through a complex algorithm.

Embodiment two:

in another embodiment, adjusting the duty cycle of each phase to output the SVPWM wave according to the adjusted duty cycle of each phase comprises:

when the duty ratio of one phase is 0% or 100% and the duty ratio of the other two phases meets k 1-D-k 2, taking the duty ratio of 0% or 100 of the duty ratios of the phases as a first duty ratio, and taking the duty ratios of the other two phases as a second duty ratio and a third duty ratio respectively; and outputting the three-phase SVPWM waves according to the first duty cycle, the second duty cycle and the third duty cycle.

It can be understood that, in this embodiment, after the duty ratio of 0% or 100% is determined as the first duty ratio, the three-phase SVPWM wave obtained after the inversion operation is performed is sampled twice according to step S610 and step S620 to obtain the sampling current, and details are not described herein again, but please refer to step S610 and step S620.

Thus, in the second embodiment, through the above steps, when one phase duty ratio is 0% or 100% in the three-phase duty ratios and the two phase duty ratios satisfy k1 and D and k2, the sampling current is obtained rapidly, the error is small, and the sampling time is obtained without calculating through a complex algorithm.

It can be understood that the duty ratios D of the respective phases corresponding to the three-phase inverter circuits 130 in the first and second embodiments satisfy the preset set dεR, (d=100%). U.S. (d=0%). U.s.k1.ltoreq.dΣ2. When there is a duty ratio that does not satisfy the preset set in the duty ratio of each phase, that is, when the pulse width of the SVPWM wave corresponding to the duty ratio that is not 0% or 100% in the duty ratio of each phase is too small or too large, the duty ratio needs to be adjusted to sample. Such duty cycles do not meet the predetermined set, and are particularly likely to occur at high modulation ratios, low modulation ratios, and sector switching. In the technical solution provided in the following embodiments of the present application, current sampling can still be implemented at the time of high modulation ratio (for example, region 2 in fig. 8), low modulation ratio (for example, region 1 in fig. 8) and sector switching (refer to the region circled by the square frame in fig. 9), and compared with the existing brushless motor current sampling solution, no complex calculation is required for the sampling time.

Specifically, please continue to refer to the following examples.

Embodiment III:

referring to fig. 9, during sector switching, there are cases where the duty ratio of one phase leg is high and the duty ratio of the other two phases leg is low. At this time, current sampling may be performed by performing the following method.

In some embodiments, the duty cycle of each phase of the corresponding three-phase inverter circuit includes a first initial duty cycle D1, a second initial duty cycle D2, and a third initial duty cycle D3. Adjusting the three-phase duty cycle to output the SVPWM wave according to the adjusted duty cycle of each phase includes:

when the first initial duty ratio D1 satisfies that k1 is less than or equal to D1 and less than or equal to k2, and the second initial duty ratio D2 and the third initial duty ratio D3 are both less than k1, the first initial duty ratio D1 is adjusted to be 100 percent and is used as a first duty ratio D4, and the second initial duty ratio D2 and the third initial duty ratio D3 are respectively adjusted to be a second duty ratio D5 and a third duty ratio D6;

and the second duty cycle D5 satisfies: d5 =d2+ (100-D1);

the third duty cycle D6 satisfies: d6 =d3+ (100-D1).

That is, the same duty cycle is added to the first, second and third initial duty cycles D1, D2 and D3, respectively, so that the adjusted first, second and third duty cycles satisfy the preset set D e R: (d=100%) U (d=0%) U (k1.ltoreq.dΣ2). Thus, according to the operation in the first embodiment, the current flowing through the corresponding bridge arm can be obtained by sampling at the first sampling time and the second sampling time.

For convenience of explanation of the technical solutions of the present application, in the following examples, k1 is 10% and k2 is 90% are exemplified to explain each technical solution related to the present application. For example, when the first initial duty ratio D1 is 30%, and the second initial duty ratio D2 and the third initial duty ratio D3 are both 0%, the first duty ratio D4 is 100%, and the second duty ratio D5 and the third duty ratio are both 70% after the operation according to the above rule. And then, according to step S610 and step S620, current sampling is performed twice, so as to obtain a sampled current. The specific process is shown in the first embodiment, and will not be described herein.

It can be appreciated that in some embodiments, when the first initial duty cycle D1 is greater than k2, the second initial duty cycle D2 and the third initial duty cycle D3 are both smaller than k1, the first initial duty cycle D1 is adjusted to 100%, and the second initial duty cycle D2 and the third initial duty cycle D3 are increased by the same value L (0% < L < 100%) to obtain the second duty cycle D5 and the third duty cycle D6, respectively, and k1 is equal to or less than d2+l is equal to or less than k2; k1 is less than or equal to D3+L is less than or equal to k2.

Embodiment four:

at low modulation ratios, the duty cycle of each phase in the three-phase inverter circuit 130 is low. At this time, current sampling may be performed by performing the following method.

Referring to fig. 10, in some embodiments, adjusting the duty cycle of each phase to output the SVPWM wave according to the adjusted duty cycle of each phase further includes:

step S101: when the duty ratio of each phase is smaller than k1, comparing the duty ratios of each phase to obtain a first initial duty ratio D1, a second initial duty ratio D2 and a third initial duty ratio D3, wherein the first initial duty ratio D1 is the minimum value in the duty ratios of each phase.

Step S102: the first initial duty ratio D1 is adjusted to be a first duty ratio D4, and the value of the first duty ratio D4 meets the condition that k1 is less than or equal to D4 is less than or equal to k2.

Step S103: the second initial duty cycle D2 and the third initial duty cycle D3 are respectively adjusted to be the second duty cycle D5 and the third duty cycle D6, wherein,

the second duty cycle D5 satisfies: d5 =d2+ (D4-D1);

the third duty cycle D6 satisfies: d6 =d3+ (D4-D1), and k1+.d5+.k2, k1+.d6+.k2;

step S104: and outputting the three-phase SVPWM waves according to the first duty ratio D4, the second duty ratio D5 and the third duty ratio D6.

Understandably, in the above-described embodiment, the first initial duty ratio D1 with the smallest duty ratio is adjusted to the first duty ratio D4, and k1.ltoreq.d4.ltoreq.k2. In this way, the second initial duty ratio D2 and the third initial duty ratio D3 that are larger than the first initial duty ratio D1 are increased by the same value, and the duty ratio value can be adjusted to be within the preset set.

Fifth embodiment:

it can be understood that, in the fourth embodiment, since the first initial duty ratio D1, the second initial duty ratio D2 and the third initial duty ratio D3 are all smaller than k1, and the first duty ratio D4, the second duty ratio D5 and the third duty ratio D6 are respectively obtained by adding the first initial duty ratio D1, the second initial duty ratio D2 and the third initial duty ratio D3 to the same value, the value between the largest duty ratio and the smallest duty ratio of the first duty ratio D4, the second duty ratio D5 and the third duty ratio D6 is smaller than k1. Because the value of k1 is smaller, the values of the adjusted first duty ratio D4, the second duty ratio D5 and the third duty ratio D6 may be relatively close, and if sampling is performed according to the sampling method provided in the first embodiment, a larger sampling error may be generated. Thus, in some embodiments, step S430 may include the following sub-steps to achieve current sampling.

Referring to fig. 11, in a fourth embodiment, in some embodiments, sampling twice according to the three-phase SVPWM wave to obtain three-phase current flowing through the brushless motor includes:

step S111: any one of the three phases of SVPWM waves is selected for inverting operation to generate a first set of SVPWM waves.

Step S112: and performing first sampling according to the first group of SVPWM waves, wherein the sampling moment of the first sampling is the midpoint of the modulation period of the corresponding first group of SVPWM waves.

Step S113: the other phase of the first set of SVPWM waves is selected for inverting operation again to generate a second set of SVPWM waves.

Step S114: and performing second sampling according to the second set of SVPWM waves, wherein the sampling moment of the second sampling is the midpoint of the modulation period of the corresponding second set of SVPWM waves.

It is understood that by executing steps S111-S114, two sets of three-phase SVPWM waves are output, and at least two SVPWM waves with opposite polarities exist at the midpoint of the modulation period of each set of SVPWM waves, and further, by sampling at the midpoint of the modulation period of the two sets of SVPWM waves, respectively, two different currents can be obtained by sampling.

Referring to fig. 12, for example, after steps 101 to 104 are performed to generate three-PHASE SVPWM waves, the SVPWM wave corresponding to the C-PHASE bridge arm, that is, PHASE C1 is selected to perform an inversion operation to generate a first set of SVPWM waves (including PHASE A1, PHASE B1, PHASE C1). Sampling is performed at the midpoint of the modulation period of the first set of SVPWM waves to obtain-IC.

Then, the opposite PHASE operation is performed on the SVPWM wave corresponding to the B PHASE bridge arm in the first group of SVPWM waves, namely the PHASE B1, so as to obtain a second group of SVPWM waves (comprising the PHASE A2, the PHASE B2 and the PHASE C2). Sampling is performed at the midpoint of the modulation period of the second set of SVPWM waves to obtain IA. Thus, IB can be obtained according to the current reconstruction formula. Thereby completing the current sampling.

Example six:

in the case of a high modulation ratio, the duty ratio of one phase arm may be high and the duty ratio of the other phase arm may be low in the three-phase inverter circuit 130. At this time, current sampling may be performed by performing the following method.

Referring to fig. 13, in some embodiments, the duty cycle of each phase of the corresponding three-phase inverter circuit includes a first initial duty cycle, a second initial duty cycle, and a third initial duty cycle, and adjusting the duty cycle of each phase to output the SVPWM wave according to the adjusted duty cycle of each phase includes:

step S131: when a first initial duty ratio smaller than k1 and a second initial duty ratio larger than k2 exist in the duty ratios of the phases, the first initial duty ratio is adjusted to be the first duty ratio, and the first duty ratio is 0%;

step S132: adjusting the second initial duty cycle to be a second duty cycle, wherein the second duty cycle is 100%;

step S133: adjusting the third initial duty cycle to be a third duty cycle, wherein the third duty cycle is greater than k1 and less than k2;

step S134: and outputting the three-phase SVPWM waves according to the first duty cycle, the second duty cycle and the third duty cycle.

It will be appreciated that when there is a first initial duty cycle of less than k1 and a second duty cycle of greater than k2 in the three phase duty cycles, then if the first, second and third initial duty cycles are increased by the same value as in the method of the above embodiment, this will result in the value of the second initial duty cycle possibly exceeding 100% and the value of the first initial duty cycle again possibly being less than k1. Thus, in the present embodiment, the first initial duty ratio is adjusted to be the first duty ratio, and the first duty ratio is 0%; adjusting the second initial duty cycle to be a second duty cycle, wherein the second duty cycle is 100%; the step of intermediate calculation of how to determine the increment value is omitted. Further, by directly adjusting the third initial duty ratio to be the third duty ratio, where the third duty ratio is greater than k1 and less than k2, the possible sampling interval in the embodiment is greater than or equal to the minimum current sampling period, thereby meeting the sampling requirement.

Embodiment seven:

in some embodiments, the sampling twice to obtain three-phase currents flowing through the brushless motor according to the three-phase SVPWM wave includes:

performing twice sampling according to the three-phase SVPWM wave, wherein one sampling time in the twice sampling is the starting point of a modulation period; the other of the two samples is at the midpoint of the modulation period.

It will be appreciated that since in embodiment six, one of the three duty cycles has been adjusted to 100% and one to 0%. That is, through the operation of the sixth embodiment, two SVPWM waves having opposite phases can be already generated. Thus, the two sampling processes can be directly performed without performing the inversion operation.

In some embodiments, the minimum current sampling period referred to herein may be the sum of the current oscillation time and the sampling time. Therefore, errors caused by current oscillation and time delay in the sampling process can be reduced, and the probability of successful sampling is improved.

With continued reference to fig. 14, an embodiment of the present application further provides an electronic device 200. The electronic device 200 includes a processor 110 and a brushless motor 140. A processor 110 is electrically connected to the brushless motor, and the processor is configured to perform the current sampling method as set forth in any one of the above, and control the operation state of the brushless motor 140 according to the current sampling result. It is understood that the electronic device 200 includes, but is not limited to, a self-moving robot, an air conditioner, or other electronic apparatus including a brushless motor, and the present application is not limited to the type of electronic device 200.

Referring to fig. 15, the present application further provides a current sampling apparatus 300, which includes an obtaining module 310, an adjusting module 320, and a sampling module 330.

The obtaining module 310 is configured to obtain the duty ratio of each phase of the corresponding three-phase inverter circuit in the current modulation period.

The adjusting module 320 is configured to adjust the duty ratio of each phase, so as to output the SVPWM wave according to the adjusted duty ratio of each phase, where the adjusted duty ratio of each phase is different, and the relationship between the adjusted duty ratio D of each phase and the preset set R satisfies D e R: (D=100%). U.S. (D=0%). U.S. (k1.ltoreq.D.ltoreq.k2), the product of k1 and the modulation period is larger than the minimum current sampling period, and the product of (100% -k 2) and the modulation period is larger than the minimum current sampling period.

The sampling module 330 is configured to perform sampling twice according to the three-phase SVPWM wave to obtain a three-phase current flowing through the brushless motor, where a sampling time of at least one of the two samplings is a midpoint of the modulation period, and at the midpoint of the modulation period, polarities of two of the three-phase SVPWM waves are opposite.

Specific details of the current sampling method for implementing the current sampling device for the brushless motor provided in the embodiment of the current sampling method for the brushless motor have been described in detail in the embodiment of the corresponding current sampling method for the brushless motor, and are not described herein again.

The embodiments of the present application also provide a computer readable medium having stored thereon a computer program which, when executed by a processor, implements a method for sampling a current of a brushless motor as in the above technical solutions. The computer readable medium may take the form of a portable compact disc read only memory (CD-ROM) and include program code that can be run on a terminal device, such as a personal computer. However, the program product of the present invention is not limited thereto, and in this document, a readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

The program product described above may take the form of any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. The readable storage medium can be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a combination of any of the foregoing. More specific examples (a non-exhaustive list) of the readable storage medium would include the following: an electrical connection having one or more wires, a portable disk, a hard disk, random Access Memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

The computer readable signal medium may include a data signal propagated in baseband or as part of a carrier wave with readable program code embodied therein. Such a propagated data signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination of the foregoing. A readable signal medium may also be any readable medium that is not a readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Program code embodied on a readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Program code for carrying out operations of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device, partly on a remote computing device, or entirely on the remote computing device or server. In the case of remote computing devices, the remote computing device may be connected to the user computing device through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computing device (e.g., connected via the Internet using an Internet service provider).

Furthermore, the above-described drawings are only schematic illustrations of processes included in the method according to the exemplary embodiment of the present invention, and are not intended to be limiting. It will be readily appreciated that the processes shown in the above figures do not indicate or limit the temporal order of these processes. In addition, it is also readily understood that these processes may be performed synchronously or asynchronously, for example, among a plurality of modules.

In addition, those of ordinary skill in the art will recognize that the above embodiments are presented for purposes of illustration only and are not intended to be limiting, and that suitable modifications and variations of the above embodiments are within the scope of the disclosure of the present application.

Claims (10)

1. A current sampling method of a brushless motor, the brushless motor being electrically connected to a three-phase inverter circuit, and sampling resistors being connected in series to bus bars of the three-phase inverter circuit, for sampling by the sampling resistors to obtain a current flowing through the brushless motor, the current sampling method comprising:

the duty ratio of each phase of the three-phase inverter circuit corresponding to the current modulation period is obtained;

adjusting the duty ratio of each phase to output SVPWM waves according to the adjusted duty ratio of each phase; the relation between the duty ratio D of each phase after adjustment and a preset set R satisfies D epsilon R (D=100%) (D=0%) (k 1 is less than or equal to D is less than or equal to k 2), the product of k1 and the modulation period is greater than the minimum current sampling period, and the product of (100% -k 2) and the modulation period is greater than the minimum current sampling period;

At the midpoint of the modulation period, reversing the polarity of two of the three-phase SVPWM waves; and sampling twice according to the three-phase SVPWM wave to obtain three-phase current flowing through the brushless motor, wherein the sampling time of at least one of the two times of sampling is the midpoint of the modulation period.

2. The sampling method of claim 1, wherein adjusting the duty cycle of each phase to output the SVPWM wave according to the adjusted duty cycle of each phase comprises:

when the duty ratio D of each phase meets k 1-D-k 2, taking the duty ratio of any one phase in the three-phase inverter circuit as a first duty ratio, wherein the first duty ratio is 100% or 0%, and taking the duty ratios of the other two phases as a second duty ratio and a third duty ratio respectively; outputting the three-phase SVPWM waves according to the first duty cycle, the second duty cycle and the third duty cycle; or (b)

When the duty ratio of each phase is 0% or 100% and the duty ratio of the other two phases satisfies k 1-D-k 2, taking the duty ratio of 0% or 100 of the duty ratios of each phase as the first duty ratio and taking the duty ratio of the other two phases as the second duty ratio and the third duty ratio respectively; and outputting the three-phase SVPWM waves according to the first duty ratio, the second duty ratio and the third duty ratio.

3. The sampling method according to claim 1, wherein the duty ratios corresponding to the respective phases of the three-phase inverter circuit include a first initial duty ratio D1, a second initial duty ratio D2, and a third initial duty ratio D3, and the adjusting the duty ratio of the respective phases to output the SVPWM wave according to the adjusted duty ratio of the respective phases includes:

when the first initial duty ratio D1 satisfies that k1 is less than or equal to D1 and less than or equal to k2, and the second initial duty ratio D2 and the third initial duty ratio D3 are both less than k1, adjusting the first initial duty ratio D1 to be 100%, and as a first duty ratio D4, adjusting the second initial duty ratio D2 and the third initial duty ratio D3 to be a second duty ratio D5 and a third duty ratio D6 respectively;

and the second duty cycle D5 satisfies: d5 =d2+ (100-D1);

the third duty cycle D6 satisfies: d6 =d3+ (100-D1).

4. A sampling method according to claim 2 or 3, wherein said twice sampling from said three-phase SVPWM wave to obtain three-phase currents flowing through said brushless motor comprises:

performing an inverting operation on one of the two phases of the SVPWM wave output according to the second and third duty ratios;

sampling is carried out according to the three-phase SVPWM wave after the reverse phase operation is carried out, and the sampling time of the other sampling is the starting point of the modulation period.

5. The sampling method of claim 1, wherein adjusting the duty cycle of each phase to output the SVPWM wave according to the adjusted duty cycle of each phase comprises:

when the duty ratio of each phase is smaller than k1, comparing the duty ratios of each phase to obtain a first initial duty ratio D1, a second initial duty ratio D2 and a third initial duty ratio D3, wherein the first initial duty ratio D1 is the minimum value in the duty ratios of each phase,

the first initial duty ratio D1 is adjusted to be a first duty ratio D4, and the value of the first duty ratio D4 meets the condition that k1 is more than or equal to D4 and less than or equal to k2;

the second initial duty ratio D2 and the third initial duty ratio D3 are adjusted to be a second duty ratio D5 and a third duty ratio D6 respectively, wherein,

the second duty ratio D5 satisfies: d5 =d2+ (D4-D1);

the third duty cycle D6 satisfies: d6 =d3+ (D4-D1), and k1+.d5+.k2, k1+.d6+.k2;

and outputting the three-phase SVPWM waves according to the first duty ratio D4, the second duty ratio D5 and the third duty ratio D6.

6. The sampling method of claim 5, wherein said twice sampling from said three-phase SVPWM wave to obtain three-phase currents flowing through said brushless motor comprises:

Selecting any one phase of the three-phase SVPWM waves to perform reverse phase operation so as to generate a first group of SVPWM waves;

performing first sampling according to the first group of SVPWM waves, wherein the sampling moment of the first sampling is the midpoint of the modulation period corresponding to the first group of SVPWM waves;

selecting another phase of the first set of SVPWM waves to perform the inverting operation again to generate a second set of SVPWM waves;

and performing second sampling according to the second set of SVPWM waves, wherein the sampling time of the second sampling is the midpoint of the modulation period corresponding to the second set of SVPWM waves.

7. The sampling method according to claim 1, wherein the duty cycle corresponding to each phase of the three-phase inverter circuit includes a first initial duty cycle, a second initial duty cycle, and a third initial duty cycle, and wherein the adjusting the duty cycle of each phase to output the SVPWM wave according to the adjusted duty cycle of each phase includes:

when a first initial duty cycle smaller than k1 and a second initial duty cycle larger than k2 exist in the duty cycles of the phases, adjusting the first initial duty cycle to be the first duty cycle, wherein the first duty cycle is 0%;

adjusting the second initial duty cycle to a second duty cycle, and the second duty cycle is 100%;

Adjusting the third initial duty cycle to be a third duty cycle, wherein the third duty cycle is greater than k1 and less than k2;

and outputting the three-phase SVPWM waves according to the first duty ratio, the second duty ratio and the third duty ratio.

8. The sampling method of claim 7, wherein the twice sampling from the three-phase SVPWM wave to obtain three-phase currents flowing through the brushless motor comprises:

performing twice sampling according to the three-phase SVPWM wave, wherein one sampling time in the twice sampling is the starting point of the modulation period; the other sampling instant of the two samplings is the midpoint of the modulation period.

9. The sampling method of claim 1, wherein the minimum current sampling period is a sum of a current oscillation time and a sampling time.

10. An electronic device comprising a processor and a brushless motor, the processor being electrically connected to the brushless motor, the processor being configured to perform the method of sampling current of the brushless motor according to any one of claims 1 to 9, and to control an operation state of the brushless motor according to a result of the current sampling.