Current sampling device, drive assembly and electric tool

Abstract

The present disclosure relates to a current sampling device, a drive component and an electric tool, the device comprising: a three-phase motor; a three-phase full-bridge inverter; a first current sampling module for current sampling using the transistor internal resistance of the fourth transistor, the transistor internal resistance of the fifth transistor and the transistor internal resistance of the sixth transistor; a second current sampling module for current sampling through the bus; a sampling selection module for: in a control cycle, according to the first duration when the fourth transistor, the fifth transistor and the sixth transistor are all disconnected, determining whether to use the first current sampling module or the second current sampling module for current sampling. Through the above devices, the current sampling device of the embodiment of the present disclosure has the characteristics of diversified current sampling methods, and can avoid the problem of sampling blind spots, can perform all-round current sampling, improve the real-time and comprehensiveness of current sampling, and improve the accuracy of motor control.

Description

Technical Field

[0001] The present disclosure relates to the technical field of motor control, and in particular to a current sampling device, a drive component and an electric tool. Background Art

[0002] DC motors are widely used in high-performance speed regulation systems because of their good speed regulation performance, wide speed regulation range and simple speed regulation method. However, the commutator of brushed motors inevitably has shortcomings such as commutation sparks, mechanical noise, and poor maintainability. In order to make up for these shortcomings of brushed DC motors, brushless DC motors (BLDC for short) came into being. Brushless DC motors not only make up for the shortcomings of brushed DC motors, but also have comparable performance to brushed DC motors, so they are increasingly used in high-performance servos and home appliances.

[0003] When controlling a brushless DC motor, it is necessary to sample the current of each phase of the electrode for feedback control. However, when performing current sampling in related technologies, the current sampling method is single and cannot solve the existing sampling blind area problem. Summary of the invention

[0004] In view of this, the present disclosure proposes a current sampling device, a drive component and an electric tool to achieve current sampling when the motor is driven.

[0005] According to one aspect of the present disclosure, a current sampling device is provided, the device comprising:

[0006] Three-phase motor;

[0007] A three-phase full-bridge inverter, comprising a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, and a sixth transistor, wherein the first transistor and the fourth transistor form a first bridge arm, and the fourth transistor is a lower half bridge, the second transistor and the fifth transistor form a second bridge arm, and the fifth transistor is a lower half bridge, the third transistor and the sixth transistor form a third bridge arm, and the sixth transistor is a lower half bridge, wherein the first ends of the windings of the three-phase motor are connected, and the second ends of the windings are respectively connected between the first transistor and the fourth transistor, between the second transistor and the fifth transistor, and between the third transistor and the sixth transistor;

[0008] A first current sampling module, connected to the second end of each winding, for performing current sampling using the transistor internal resistance of the fourth transistor, the transistor internal resistance of the fifth transistor, and the transistor internal resistance of the sixth transistor;

[0009] A second current sampling module, connected to the bus of the three-phase motor, for sampling current through the bus;

[0010] A sampling selection module is connected to the first current sampling module and the second current sampling module, and is used to: in a control cycle, determine whether to use the first current sampling module or the second current sampling module for current sampling according to a first duration when the fourth transistor, the fifth transistor, and the sixth transistor are all disconnected.

[0011] In a possible implementation, the sampling selection module includes:

[0012] The first selection submodule is configured to: when the first time duration is greater than a first preset time duration, control the first current sampling module to perform current sampling to obtain phase currents of at least two phases.

[0013] In a possible implementation, the sampling selection module includes:

[0014] The second selection submodule is used to: when the first time length is less than a first preset time length, control the second current sampling module to perform current sampling to obtain a phase current of at least one phase.

[0015] In a possible implementation, the second selection submodule includes:

[0016] The first selection unit is used to: in a control cycle, when the duration of each control stage in which any one of the fourth transistor, the fifth transistor, and the sixth transistor is turned on is greater than a second preset duration, control the second current sampling module to perform current sampling in each control stage to obtain phase currents of at least two phases,

[0017] The second preset duration is shorter than the first preset duration.

[0018] In a possible implementation manner, the device further includes:

[0019] A phase shift module, used for phase shifting the control signal;

[0020] Wherein, the second selection submodule includes:

[0021] The second selection unit is used to: in a control cycle, when the second duration of the control stage in which any one of the fourth transistor, the fifth transistor, and the sixth transistor is turned on is less than the second preset duration, control the phase shift module to shift the phase of the control signal of the control stage in which the second duration is less than the second preset duration, and control the second current sampling module to perform current sampling in each control stage to obtain the phase current of at least one phase.

[0022] In a possible implementation manner, the second selection unit includes:

[0023] The first selection subunit is used to: when the minimum duty cycle of the control signal is greater than the minimum phase shift sampling time, or the difference between the period value of the control period and the maximum duty cycle of the control signal is greater than the minimum phase shift sampling time, control the phase shift module to phase shift the control signal of the control stage whose second duration is less than the second preset duration, and control the second current sampling module to perform current sampling in each control stage to obtain phase currents of at least two phases.

[0024] In a possible implementation manner, the second selection unit includes:

[0025] A second selection subunit is used to: when the minimum duty cycle of the control signal is less than the minimum phase shift sampling time, or the difference between the period value of the control period and the maximum duty cycle of the control signal is less than the minimum phase shift sampling time, control the phase shift module to phase shift one of the control signals in the control stage whose second duration is less than the second preset duration, and control the second current sampling module to perform current sampling in the control stage corresponding to the phase shift control signal to obtain a phase current of one phase in the control stage;

[0026] The phase current acquisition module is used to obtain the phase currents of other phases in the previous control cycle.

[0027] In a possible implementation, the device includes:

[0028] The storage module is used to store the phase current sampled during the control period.

[0029] In a possible implementation manner, the device further includes:

[0030] The resistance determination module is used to determine the transistor resistance of the lower half-bridge transistor of each bridge arm according to the transistor voltages at both ends of the lower half-bridge transistor of each bridge arm of the three-phase full-bridge inverter and the bus voltage on the bus.

[0031] In a possible implementation, the resistance determination module includes:

[0032] a difference calculation unit, used to determine a voltage difference between the bus voltage and the transistor voltage;

[0033] The resistance determination unit is connected to the difference calculation unit and is used to determine the transistor resistance according to the voltage difference and the bus current on the bus.

[0034] In a possible implementation manner, the device further includes:

[0035] The voltage adjustment module is connected to the resistance determination module and is used to determine the adjusted transistor voltage according to the transistor resistance and preset parameters.

[0036] According to one aspect of the present disclosure, a driving component is provided, and the driving component includes the current sampling device.

[0037] According to one aspect of the present disclosure, an electric tool is provided, comprising the driving assembly.

[0038] Through the above device, the embodiment of the present disclosure can choose to use the internal resistance of the transistor for current sampling or use the bus for current sampling according to the first time length when the fourth transistor, the fifth transistor, and the sixth transistor serving as the lower half bridge are all disconnected in the motor control stage. Compared with the single current sampling method in the related art, the current sampling device of the embodiment of the present disclosure has the characteristics of diversified current sampling methods, and determines the corresponding current sampling method according to the first time length when each transistor of the lower half bridge is disconnected, which can avoid the problem of sampling blind spots, and can perform all-round current sampling, thereby improving the real-time and comprehensiveness of current sampling and improving the accuracy of motor control.

[0039] Further features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure.

[0041] Figure 1 A schematic diagram of a current sampling device according to an embodiment of the present disclosure is shown.

[0042] Figure 2 A schematic diagram of a current sampling device according to an embodiment of the present disclosure is shown.

[0043] Figure 3 A schematic diagram of motor control according to an embodiment of the present disclosure is shown.

[0044] Figure 4 A schematic diagram of control signal generation according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0045] Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0046] In the description of the present disclosure, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present disclosure.

[0047] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present disclosure, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0048] In the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0049] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0050] In addition, in order to better illustrate the present disclosure, numerous specific details are given in the following specific embodiments. It should be understood by those skilled in the art that the present disclosure can also be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present disclosure.

[0051] See also Figure 1 , Figure 1 A schematic diagram of a current sampling device according to an embodiment of the present disclosure is shown.

[0052] like Figure 1 As shown, the device comprises:

[0053] Three-phase motor 10;

[0054] A three-phase full-bridge inverter 20 includes a first transistor Q1, a second transistor Q2, a third transistor Q3, a fourth transistor Q4, a fifth transistor Q5, and a sixth transistor Q6, wherein the first transistor Q1 and the fourth transistor Q4 form a first bridge arm, and the fourth transistor Q4 is a lower half bridge, the second transistor Q2 and the fifth transistor Q5 form a second bridge arm, and the fifth transistor Q5 is a lower half bridge, the third transistor Q3 and the sixth transistor Q6 form a third bridge arm, and the sixth transistor Q6 is a lower half bridge, wherein one end of each winding of the three-phase motor 10 is electrically connected, and the other end of each winding is electrically connected between the first transistor Q1 and the fourth transistor Q4, between the second transistor Q2 and the fifth transistor Q5, and between the third transistor Q3 and the sixth transistor Q6;

[0055] A first current sampling module 40 is connected to the second end of each winding, and is used to perform current sampling using the transistor internal resistance of the fourth transistor Q4, the transistor internal resistance of the fifth transistor Q5, and the transistor internal resistance of the sixth transistor Q6; a second current sampling module 50 is connected to the bus of the three-phase motor 10, and is used to perform current sampling through the bus;

[0056] The sampling selection module 60 is connected to the first current sampling module 40 and the second current sampling module 50, and is used to: in a control cycle, determine whether to use the first current sampling module 40 or the second current sampling module 50 for current sampling according to the first time length when the fourth transistor Q4, the fifth transistor Q5, and the sixth transistor Q6 are all disconnected.

[0057] Through the above device, the embodiment of the present disclosure can choose to use the internal resistance of the transistor for current sampling or use the bus for current sampling according to the first time length when the fourth transistor, the fifth transistor, and the sixth transistor serving as the lower half bridge are all disconnected in the motor control stage. Compared with the single current sampling method in the related art, the current sampling device of the embodiment of the present disclosure has the characteristics of diversified current sampling methods, and determines the corresponding current sampling method according to the first time length when each transistor of the lower half bridge is disconnected, which can avoid the problem of sampling blind spots, and can perform all-round current sampling, thereby improving the real-time and comprehensiveness of current sampling and improving the accuracy of motor control.

[0058] It should be noted that each module and unit of the embodiment of the present disclosure may be implemented by a hardware circuit, or by using a general hardware circuit in combination with relevant existing logic.

[0059] The embodiment of the present disclosure does not limit the specific implementation of the first current sampling module 40 and the second current sampling module 50. For example, the first current sampling module 40 can collect the transistor voltages at both ends of the fourth transistor Q4, the fifth transistor Q5, and the sixth transistor Q6, and determine the sampling current according to the internal resistance of the fourth transistor Q4, the fifth transistor Q5, and the sixth transistor Q6; for example, the second current sampling module 50 may include a bus resistance unit provided on the bus. The bus resistance unit may be a single resistor or a plurality of resistors connected in parallel. The specific implementation of the bus resistance unit may be determined according to parameters such as power. The embodiment of the present disclosure may obtain the bus voltage at both ends of the bus resistance unit, and determine the bus current in combination with the resistance of the bus resistance unit.

[0060] In one example, the bus mentioned in the embodiment of the present disclosure may be a bus of a controller of a motor.

[0061] In a possible implementation, the first transistor Q1, the second transistor Q2, the third transistor Q3, the fourth transistor Q4, the fifth transistor Q5, and the sixth transistor Q6 may be metal-oxide-semiconductor field-effect transistors (MOSFET) and insulated gate bipolar transistors (IGBT), wherein the transistors may be implemented based on silicon carbide SiC and gallium nitride GaN to improve performance.

[0062] In one possible implementation, Figure 1 As shown, the three-phase full-bridge inverter 20 may further include multiple first input resistors, multiple second input resistors, and multiple input capacitors to filter the input signal, and the windings of the stator include a first winding A, a second winding B, and a third winding C, wherein the gate of each transistor of the three-phase full-bridge inverter 20 is electrically connected to the second end of the first input resistor, the first end of the second input resistor, and the first end of the input capacitor, the source of each transistor of the three-phase full-bridge inverter 20 is electrically connected to the second end of the input capacitor and the second end of the second input resistor, and the first end of the first input resistor is used to input a control signal,

[0063] The drain of the first transistor Q1, the drain of the second transistor Q2, and the drain of the third transistor Q3 are electrically connected, and the source of the fourth transistor Q4, the source of the fifth transistor Q5, and the source of the sixth transistor Q6 are electrically connected.

[0064] The source of the first transistor Q1 is electrically connected to the drain of the fourth transistor Q4 and the first end of the first winding, the source of the second transistor Q2 is electrically connected to the drain of the fifth transistor Q5 and the first end of the second winding, and the source of the third transistor Q3 is electrically connected to the drain of the sixth transistor Q6 and the first end of the third winding.

[0065] A second end of the first winding A, a second end of the second winding B, and a second end of the third winding C are grounded.

[0066] In one example, if Figure 1 As shown, the first input resistor may include a first resistor R1, a third resistor R3, a fifth resistor R5, a seventh resistor R7, a ninth resistor R9, and an eleventh resistor R11; the second input resistor may include a second resistor R2, a fourth resistor R4, a sixth resistor R6, an eighth resistor R8, a tenth resistor R10, and a twelfth resistor R12; and the input capacitor may include a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, and a sixth capacitor C6.

[0067] In one example, the three-phase full-bridge inverter 20 may further include a plurality of freewheeling diodes disposed between the source and the drain of each transistor, for providing a freewheeling path when the transistor is turned off to prevent the transistor from being damaged.

[0068] In a possible implementation, the three-phase motor may be a three-phase brushless DC motor.

[0069] In one example, the embodiment of the present disclosure realizes a Y connection (or star connection) of a three-phase motor by electrically connecting one end of each winding of the stator, and the other end of each winding is electrically connected between the first transistor Q1 and the fourth transistor Q4, between the second transistor Q2 and the fifth transistor Q5, and between the third transistor Q3 and the sixth transistor Q6.

[0070] In one example, if Figure 1 As shown, the three-phase motor may include a first winding A, a second winding B and a third winding C, one end of the first winding A is electrically connected between the first transistor Q1 and the fourth transistor Q4, one end of the second winding B is electrically connected between the second transistor Q2 and the fifth transistor Q5, and one end of the third winding C is electrically connected between the third transistor Q3 and the sixth transistor Q6.

[0071] The following is an exemplary introduction to possible implementations of each module.

[0072] See also Figure 2 , Figure 2A schematic diagram of a current sampling device according to an embodiment of the present disclosure is shown.

[0073] In one possible implementation, Figure 2 As shown, the device may include a driving module 30 for outputting a control signal to control the conduction state of each transistor.

[0074] See also Figure 3 , Figure 3 A schematic diagram of motor control according to an embodiment of the present disclosure is shown.

[0075] In a possible implementation, Figure 3 As shown, the embodiment of the present disclosure adopts SVPWM (Space Vector Pulse Width Modulation) to control the rotation of the motor.

[0076] In one example, when the six switching devices, the first transistor Q1 to the sixth transistor Q6, are combined (the signals of the upper and lower half bridges of the same bridge arm are opposite), there are 8 safe switching states, of which U0 (000) and U7 (111) will not generate effective current in the motor drive, so they can be called zero vectors. The other 6 switching states are six effective vectors. They divide the 360-degree voltage space into 60-degree sectors, a total of six sectors. Using these six basic effective vectors and two zero quantities, any vector within 360 degrees can be synthesized.

[0077] In one example, SVPWM uses the volt-second balance principle to first determine the sector where the modulation vector voltage is located, and then use the two adjacent vectors in the sector where the vector voltage is located to synthesize the required vector voltage to make the stator flux linkage a circular rotating modulation method (such as Figure 3 As shown, the vector voltage U out In the first sector, the adjacent vectors are U1 and U2). Figure 3 As shown, the circled numbers represent the sectors where the synthetic vector voltage is located, and the six modulation vectors are (100, 110, 010, 011, 001, 101), for example, lower bridge modulation is adopted (when the modulation signal A is at a high level, the corresponding lower half-bridge transistor of phase A is turned on, and when the modulation signal A is at a low level, the corresponding upper half-bridge transistor of phase A is turned on; the same applies to BC).

[0078] In one example, when generating a control signal, the driving module generally adopts a triangular counting timer operation mode.

[0079] See also Figure 4 , Figure 4 A schematic diagram of control signal generation according to an embodiment of the present disclosure is shown.

[0080] like Figure 4 As shown, the current sampling analysis is performed by taking the case where the required vector voltage falls on the first sector as an example. At this time, the vector voltage needs to be synthesized by vectors U1 (100) and U2 (110). The ABC three-phase modulation signal is as follows: Figure 4 As shown, the modulation time of vector U1 is T1, the modulation time of vector U2 is T2, T0 is the zero vector when all the three-phase upper tubes are disconnected, and T7 is the zero vector when all the three-phase lower tubes are disconnected.

[0081] In one example, since the first sampling module uses a current sampling method that collects transistor internal resistance, the sampling can only be accurate within the T7 time period, since the fourth transistor Q4, the fifth transistor Q5, and the sixth transistor Q6 are all in the disconnected state within the T7 time period. However, sampling requires a certain amount of time, and when the T7 time period is insufficient, the voltage of the transistor internal resistance cannot be collected, resulting in a sampling blind area. In this case, the disclosed embodiment uses the bus resistance for current sampling, which makes up for the defect of the sampling blind area that exists in sampling through the transistor internal resistance.

[0082] In a possible implementation, Figure 2 As shown, the sampling selection module includes:

[0083] The first selection submodule 610 is configured to: when the first time duration is greater than a first preset time duration, control the first current sampling module 40 to perform current sampling to obtain phase currents of at least two phases.

[0084] In one example, if Figure 4 As shown, if the first duration is greater than the first preset duration, in the T7 time period, the embodiment of the present disclosure can perform current sampling through the first current sampling module 40 .

[0085] In one example, let the dead time of transistor switching be T D , the noise time of the switch rising or falling is T N , an ADC sampling time is T samp Since at least two phase currents are required for vector change, each sampling time is at least two ADCs, that is, 2*T samp Therefore, in order to accurately sample the two-phase current at time T7, T7 needs to satisfy: T7>(T D +T N +2*T samp ), wherein the first preset duration may be the sum of the dead time of transistor switching, the noise time of switch switching rise or fall, and twice the ADC sampling time.

[0086] When T7 is less than the first preset time length, the embodiment of the present disclosure may utilize the second current sampling module to perform current sampling.

[0087] It should be noted that the embodiments of the present disclosure do not limit the specific implementation method of calculating the time of T7, and those skilled in the art can implement it according to relevant technologies.

[0088] In one possible implementation, Figure 2 As shown, the sampling selection module 60 may further include:

[0089] The second selection submodule 620 is used to: when the first time length is less than a first preset time length, control the second current sampling module to perform current sampling to obtain a phase current of at least one phase.

[0090] If the first time length is less than the first preset time length, there is a sampling blind spot in the method of current sampling using the internal resistance of the transistor, and an accurate current sampling result cannot be obtained. Therefore, in order to solve this problem, in this case, the embodiment of the present disclosure samples the bus current through the second current sampling module to perform current sampling.

[0091] In one example, as shown in Table 1, when the first time length is less than the first preset time length, in different switching states, the phase current of each phase can be obtained by sampling through the second current sampling module.

[0092] Table 1 shows the mode of current sampling by the states of the various transistor switches.

[0093] Switch Status AH BH CH Measurement 0 0 0 0 NA 1 1 0 0 Ia 2 1 1 0 -Ic 3 0 1 0 Ib 4 0 1 1 -Ia 5 0 0 1 Ic 6 1 0 1 -Ib 7 1 1 1 NA

[0094] Among them, AH represents the upper bridge of phase A, AH=1 represents that the upper bridge is turned on and the lower bridge is turned off, and AH=0 represents that the upper bridge is turned off.

[0095] Among them, Ia represents the A-phase current (corresponding to the first winding A), Ib represents the B-phase current (corresponding to the first winding B), and Ic represents the C-phase current (corresponding to the first winding C).

[0096] In one possible implementation, Figure 2 As shown, the second selection submodule 620 may include:

[0097] The first selection unit 6210 is used to: in a control cycle, when the duration of each control stage in which any one of the fourth transistor Q4, the fifth transistor Q5, and the sixth transistor Q6 is turned on is greater than a second preset duration, control the second current sampling module to perform current sampling in each control stage to obtain phase currents of at least two phases, wherein the second preset duration is less than the first preset duration.

[0098] In an example, the second preset time length may be the sum of the dead time of transistor switching, the noise time of the switch switching rise or fall, and the ADC sampling time (T D+T N +T samp ).

[0099] In one example, if Figure 4 As shown, for the first sector, each control stage in which any one of the fourth transistor Q4, the fifth transistor Q5, and the sixth transistor Q6 is turned on is, for example, the time periods T1 and T2 in which the control signals 100 and 110 act.

[0100] In a possible implementation, the device may further include:

[0101] A phase shift module, used for phase shifting the control signal;

[0102] like Figure 2 As shown, the second selection submodule 620 may include:

[0103] The second selection unit 6220 is used for: in a control cycle, when the second duration of the control phase in which any one of the fourth transistor Q4, the fifth transistor Q5, and the sixth transistor Q6 is turned on is less than the second preset duration, controlling the phase shifting module to phase-shift the control signal of the control phase in which the second duration is less than the second preset duration, and controlling the second current sampling module to perform current sampling in each control phase to obtain the phase current of at least one phase.

[0104] The embodiments of the present disclosure do not limit the specific implementation of the phase shift module. In one example, the phase shift module may include a phase shifter.

[0105] The embodiments of the present disclosure do not limit the parameters (such as the phase of the phase shift) when the phase shift module performs phase shifting, and those skilled in the art can set them as needed.

[0106] For different conditions satisfied by the duty cycle of the control signal, the embodiments of the present disclosure may have a variety of corresponding phase shifting methods and current sampling methods, which are described below with examples.

[0107] In one possible implementation, Figure 2 As shown, the second selection unit 6220 includes:

[0108] The first selection subunit 6221 is used to: when the minimum duty cycle of the control signal is greater than the minimum phase shift sampling time, or the difference between the period value of the control period and the maximum duty cycle of the control signal is greater than the minimum phase shift sampling time, control the phase shift module to phase shift the control signal of the control stage whose second duration is less than the second preset duration, and control the second current sampling module to perform current sampling in each control stage to obtain phase currents of at least two phases.

[0109] When the minimum duty cycle of the control signal is greater than the minimum phase shift sampling time, or the difference between the period value of the control period and the maximum duty cycle of the control signal is greater than the minimum phase shift sampling time, the control signals of each control stage meet the phase shift conditions. Therefore, the embodiment of the present disclosure can control the phase shift module to phase shift the control signal of the control stage whose second duration is less than the second preset duration, and control the second current sampling module to perform current sampling in each control stage to obtain phase currents of at least two phases.

[0110] In one example, if Figure 4 As shown, if the minimum duty cycle of the control signal of the control stage corresponding to T1 and T2 is greater than the minimum time of phase shift sampling, or the difference between the period value of the control period and the maximum duty cycle of the control signal is greater than the minimum time of phase shift sampling, then the embodiment of the present disclosure can phase-shift the control signal of the control stage corresponding to T1 and T2, so that the control signal after phase shift satisfies the condition that the second time length is greater than the second preset time length, so as to realize the current sampling of the bus.

[0111] In one possible implementation, Figure 2 As shown, the second selection unit 6220 includes:

[0112] The second selection subunit 6222 is used to: when the minimum duty cycle of the control signal is less than the minimum phase shift sampling time, or the difference between the period value of the control period and the maximum duty cycle of the control signal is less than the minimum phase shift sampling time, control the phase shift module to phase shift one of the control signals in the control stage whose second duration is less than the second preset duration, and control the second current sampling module to perform current sampling in the control stage corresponding to the phase shift control signal to obtain the phase current of one phase in the control stage;

[0113] The phase current acquisition module is used to obtain the phase currents of other phases in the previous control cycle.

[0114] In one example, if the minimum duty cycle of the control signal is less than the minimum phase shift sampling time, or the difference between the period value of the control cycle and the maximum duty cycle of the control signal is less than the minimum phase shift sampling time, the control signals of multiple control stages cannot be phase shifted at the same time to meet the condition that the second duration is greater than the second preset duration. Therefore, the embodiment of the present disclosure can phase shift one of the control signals so that it meets the condition that the second duration is greater than the second preset duration. In this case, the embodiment of the present disclosure can use the second current sampling module to perform current sampling to obtain the phase current of the phase. Taking the vector voltage of the first quadrant as an example, if T1 and T2 corresponding to the control signals 100 and 110 cannot meet the phase shift condition, that is, when the minimum duty cycle of the control signal is less than the minimum phase shift sampling time, or the difference between the period value of the control cycle and the maximum duty cycle of the control signal is less than the minimum phase shift sampling time, then the embodiment of the present disclosure phase shifts the control signal 100 (or 110). In this case, the phase current of phase A can be obtained.

[0115] When the minimum duty cycle of the control signal is less than the minimum phase shift sampling time, or the difference between the period value of the control cycle and the maximum duty cycle of the control signal is less than the minimum phase shift sampling time, since the phase currents of the two phases cannot be obtained by phase shifting, the embodiment of the present disclosure can use the phase current of another phase sampled in the previous control cycle (PWM cycle), such as the phase current of phase B, combined with the phase current obtained by sampling the bus current after phase shifting to perform vector transformation.

[0116] In a possible implementation, the device may include:

[0117] The storage module is used to store the phase current sampled during the control period.

[0118] In one example, the storage module can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk.

[0119] The embodiment of the present disclosure can utilize a storage module to store all phase currents sampled in each control period, and can call them when needed.

[0120] It should be noted that the embodiments of the present disclosure do not limit the specific implementation of how to obtain the stored phase current data from the storage module, and those skilled in the art can implement it according to relevant technologies.

[0121] In a possible implementation, the device may further include:

[0122] The resistance determination module is used to determine the transistor resistance of the lower half-bridge transistor of each bridge arm according to the transistor voltages at both ends of the lower half-bridge transistor of each bridge arm of the three-phase full-bridge inverter and the bus voltage on the bus.

[0123] The transistor of a power device will generate serious heat with continuous switching, and the resistance of the transistor will also change greatly with temperature. Therefore, when the temperature of the transistor rises, the sampling value will deviate seriously. The embodiment of the present disclosure can determine the size of the internal resistance of the transistor in real time when sampling the current, so as to overcome the method of using a fixed resistance for current sampling calculation in the related art. In addition, there is no need to add a temperature sensor, which saves the circuit area of ​​the device and the cost. The current temperature of the transistor can be determined based on the current transistor resistance and the relationship between resistance and temperature, so as to achieve precise control of the transistor temperature.

[0124] The resistance determination module can be implemented by a hardware circuit, and those skilled in the art will not limit the specific implementation of the resistance determination module.

[0125] The following is an exemplary introduction to possible implementations of the resistance determination module.

[0126] In a possible implementation, the resistance determination module may include:

[0127] a difference calculation unit, used to determine a voltage difference between the bus voltage and the transistor voltage;

[0128] The resistance determination unit is connected to the difference calculation unit and is used to determine the transistor resistance according to the voltage difference and the bus current on the bus.

[0129] In one example, the difference calculation unit may include an adder, and the bus voltage and the transistor voltage may be subtracted from each other by the adder to obtain a voltage difference between the bus voltage and the transistor voltage.

[0130] In one example, the resistance determination unit may include a filter to achieve smoothing of the voltage difference, and may also include a resistance calculation unit (eg, which may be implemented using a divider) for calculating the voltage difference and the bus current to obtain the transistor resistance.

[0131] The embodiments of the present disclosure do not limit the specific implementation of the resistance determination unit, and those skilled in the art can select a suitable method to determine the resistance as needed.

[0132] In a possible implementation, the device may further include:

[0133] The voltage adjustment module is connected to the resistance determination module and is used to determine the adjusted transistor voltage according to the transistor resistance and preset parameters.

[0134] In one example, the preset parameter may be a current instruction determined according to the loop. The embodiment of the present disclosure does not limit the specific size of the preset parameter, and those skilled in the art may set it according to needs or actual conditions.

[0135] The embodiments of the present disclosure do not limit the specific implementation of the voltage adjustment module. In some examples, the voltage adjustment module may include a multiplier or other hardware circuits, and those skilled in the art may set them as needed.

[0136] The embodiment of the present disclosure obtains the voltage across the transistor as feedback, and uses the bus resistance set on the bus to collect the bus voltage to adjust the voltage across the transistor. During the adjustment process, the real resistance of the transistor in the current state can be determined. Through such a setting, the embodiment of the present disclosure can obtain accurate current sampling results.

[0137] The disclosed embodiment addresses the problems existing in MOS internal resistance current sampling and bus resistance sampling, and uses a sampling method that combines bus current sampling and MOS internal resistance sampling. It determines which current sampling method to sample based on the first time length when each lower half-bridge transistor is disconnected, thereby achieving sampling without blind spots, and adding a filtering link to the correction link to increase anti-interference capability. At the same time, it also solves the problem of sampling blind spots existing in the use of MOS internal resistance sampling and single resistor current sampling technology.

[0138] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A current sampling device, characterized in that: The device comprises: Three-phase motor; A three-phase full-bridge inverter, comprising a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, and a sixth transistor, wherein the first transistor and the fourth transistor form a first bridge arm, and the fourth transistor is a lower half bridge, the second transistor and the fifth transistor form a second bridge arm, and the fifth transistor is a lower half bridge, the third transistor and the sixth transistor form a third bridge arm, and the sixth transistor is a lower half bridge, wherein the first ends of the windings of the three-phase motor are connected, and the second ends of the windings are respectively connected between the first transistor and the fourth transistor, between the second transistor and the fifth transistor, and between the third transistor and the sixth transistor; A first current sampling module, connected to the second end of each winding, for performing current sampling using the transistor internal resistance of the fourth transistor, the transistor internal resistance of the fifth transistor, and the transistor internal resistance of the sixth transistor; A second current sampling module, connected to the bus of the three-phase motor, for sampling current through the bus; A sampling selection module, connected to the first current sampling module and the second current sampling module, for: in a control cycle, according to the first duration when the fourth transistor, the fifth transistor, and the sixth transistor are all disconnected, determining whether to use the first current sampling module or the second current sampling module for current sampling, the sampling selection module comprising: a second selection submodule, for: when the first duration is less than a first preset duration, controlling the second current sampling module to perform current sampling to obtain a phase current of at least one phase, the second selection submodule comprising: a first selection unit, for: in a control cycle, when the duration of each control stage when any one of the fourth transistor, the fifth transistor, and the sixth transistor is turned on is greater than a second preset duration, controlling the second current sampling module to perform current sampling in each control stage to obtain a phase current of at least two phases, wherein the second preset duration is less than the first preset duration, The device also includes: a resistance determination module, which is used to determine the transistor resistance of the lower half-bridge transistor of each bridge arm according to the transistor voltages at both ends of the lower half-bridge transistor of each bridge arm of the three-phase full-bridge inverter and the bus voltage on the bus.

2. The device according to claim 1, characterized in that The sampling selection module comprises: The first selection submodule is configured to: when the first time duration is greater than a first preset time duration, control the first current sampling module to perform current sampling to obtain phase currents of at least two phases.

3. The device according to claim 1, characterized in that The device also includes: A phase shift module, used for phase shifting the control signal; Wherein, the second selection submodule includes: The second selection unit is used to: in a control cycle, when the second duration of the control stage in which any one of the fourth transistor, the fifth transistor, and the sixth transistor is turned on is less than the second preset duration, control the phase shift module to shift the phase of the control signal of the control stage in which the second duration is less than the second preset duration, and control the second current sampling module to perform current sampling in each control stage to obtain the phase current of at least one phase.

4. The device according to claim 3, characterized in that The second selection unit comprises: The first selection subunit is used to: when the minimum duty cycle of the control signal is greater than the minimum phase shift sampling time, or the difference between the period value of the control period and the maximum duty cycle of the control signal is greater than the minimum phase shift sampling time, control the phase shift module to phase shift the control signal of the control stage whose second duration is less than the second preset duration, and control the second current sampling module to perform current sampling in each control stage to obtain phase currents of at least two phases.

5. The device according to claim 3, characterized in that The second selection unit comprises: A second selection subunit is used to: when the minimum duty cycle of the control signal is less than the minimum phase shift sampling time, or the difference between the period value of the control period and the maximum duty cycle of the control signal is less than the minimum phase shift sampling time, control the phase shift module to phase shift one of the control signals in the control stage whose second duration is less than the second preset duration, and control the second current sampling module to perform current sampling in the control stage corresponding to the phase shift control signal to obtain a phase current of one phase in the control stage; The phase current acquisition module is used to obtain the phase currents of other phases in the previous control cycle.

6. The device according to any one of claims 2 to 5, characterized in that: The device comprises: The storage module is used to store the phase current sampled during the control period.

7. The device according to claim 1, characterized in that The resistance determination module comprises: a difference calculation unit, used to determine a voltage difference between the bus voltage and the transistor voltage; The resistance determination unit is connected to the difference calculation unit and is used to determine the transistor resistance according to the voltage difference and the bus current on the bus.

8. The device according to claim 1, characterized in that The device also includes: The voltage adjustment module is connected to the resistance determination module and is used to determine the adjusted transistor voltage according to the transistor resistance and preset parameters.

9. A drive assembly, characterized in that: The driving component comprises a current sampling device as described in any one of claims 1-8.

10. An electric tool, characterized in that: The electric tool comprises the drive assembly according to claim 9.

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