CN112117938A - Brushless motor current sampling method and brushless motor control mechanism - Google Patents
Brushless motor current sampling method and brushless motor control mechanism Download PDFInfo
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- CN112117938A CN112117938A CN201911324912.3A CN201911324912A CN112117938A CN 112117938 A CN112117938 A CN 112117938A CN 201911324912 A CN201911324912 A CN 201911324912A CN 112117938 A CN112117938 A CN 112117938A
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- 238000005070 sampling Methods 0.000 title claims abstract description 31
- 238000000034 method Methods 0.000 title claims abstract description 18
- 238000001514 detection method Methods 0.000 claims description 6
- 238000004804 winding Methods 0.000 description 32
- 238000010586 diagram Methods 0.000 description 8
- 230000003111 delayed effect Effects 0.000 description 7
- 230000001939 inductive effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
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- 230000001934 delay Effects 0.000 description 1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
- H02P6/16—Circuit arrangements for detecting position
- H02P6/18—Circuit arrangements for detecting position without separate position detecting elements
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/20—Arrangements for starting
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/20—Arrangements for starting
- H02P6/21—Open loop start
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/20—Arrangements for starting
- H02P6/22—Arrangements for starting in a selected direction of rotation
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Abstract
The invention discloses a brushless motor current sampling method and a brushless motor control mechanism. The control mechanism comprises an inverter circuit and a control circuit, wherein the inverter circuit comprises at least two bridge arms, the bridge arms are a first bridge arm and a second bridge arm, the control circuit controls upper switch tubes and lower switch tubes of the first bridge arm and the second bridge arm to be conducted in at least one state, different bus current values are adopted, the initial position of a rotor is determined according to the current values, the upper switch tubes of the first bridge arm and the lower switch tubes of the second bridge arm are controlled to be conducted for a first preset time at the same time, the first current values can be collected, the upper switch tubes of the first bridge arm are turned off, the lower switch tubes of the second bridge arm are continuously conducted at the same time, the lower switch tubes of the second bridge arm are turned off after the upper switch tubes of the first bridge arm and the lower switch tubes. The invention realizes current sampling and motor positioning in a simple form, and reduces peak voltage, thereby reducing voltage applied to two ends of a switch tube, reducing requirements of the switch tube and reducing cost.
Description
[ technical field ]
The invention relates to the technical field of brushless motor control, in particular to a brushless motor current sampling method and a brushless motor control mechanism.
[ background art ]
In order to achieve the start-up of the brushless motor, it is necessary to determine the initial position of the rotor. The permanent magnet motor detects the position of the rotor through the Hall sensor, but the position sensor has high cost, so the brushless sensorless motor is widely applied, the sensorless control mode does not adopt the position sensor, the mode of detecting the bus current can be adopted, different combination switching is carried out on the switch tube of the inverter circuit, positive and negative voltages are led into any two phase windings, the bus current is respectively adopted, the initial position of the rotor is determined according to the relation between the currents, when the switch tube is disconnected for switching, the current cannot suddenly change because the motor winding is inductive, a follow current process can be generated, as shown in a known follow current flow schematic diagram shown in figure 6, if the UV phase is firstly conducted (Q1Q5 is conducted), when the UV phase is switched, the current flowing through the UV phase winding cannot suddenly change because the motor is inductive load, and the current passes through the diode D4 and the U-phase winding, The V-phase winding and the diode D2 freewheel, at this time, the voltage to ground of the V-phase is Vcc + Vds (reverse voltage drop of the switching tube), the winding generates a peak voltage, as shown in fig. 7, the peak voltage value of the V-phase is represented at the line a, and reaches 31V at this time, so that the voltage applied to both ends of the switching tube is too high, and therefore, the peak voltage easily causes insulation damage of the motor winding, and meanwhile, the requirement for the switching tube needs to be increased for normal operation of the circuit, and at this time, the switching tube with a withstand voltage of 40V needs to be adopted, which is high in cost.
Please refer to chinese patent application publication No. CN103618485B, published on 2016, 01, 13, which discloses a method for detecting an initial position of a brushless dc motor without a position sensor, wherein switching tubes are turned on two by two in six three phases, six times of bus current are collected, primary positioning is realized according to a relationship between currents, a critical position of a rotor is determined, and then switching tubes are turned on three by three, secondary positioning is realized, and an accurate position of the rotor is determined.
Therefore, it is necessary to design a new brushless motor positioning system to solve the technical problems in the prior art.
[ summary of the invention ]
In view of the deficiencies of the prior art, the present invention provides a brushless motor current sampling method and a brushless motor control mechanism capable of suppressing spike voltage.
The invention solves the problems of the prior art by adopting the following technical scheme: a brushless motor current sampling method, comprising: the inverter circuit comprises a positive direct current bus, a negative direct current bus and at least two bridge arms, the bridge arms are a first bridge arm and a second bridge arm, the first bridge arm and the second bridge arm are connected between the positive direct current bus and the negative direct current bus, the first bridge arm and the second bridge arm are respectively provided with an upper switch tube and a lower switch tube, the upper switch tube is connected with the positive direct current bus, the lower switch tube is connected with the negative direct current bus, each lower switch tube is respectively connected with a diode in parallel in a reverse direction, the control circuit controls the upper switch tube and the lower switch tube to be conducted in at least one conducting state and adopts direct current bus current values in different states, the control circuit controls the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm to be conducted simultaneously for a first preset time, can collect a first current value and turn off the upper switch tube of the first bridge arm, and simultaneously continue to conduct the lower switch tube of the second bridge arm, and the lower switch tube of the second bridge arm and the diode connected in parallel with the lower switch tube of the first bridge arm form a follow current loop, and the lower switch tube of the second bridge arm is turned off after the second preset time is conducted.
The further improvement scheme is as follows: the control circuit controls the upper switch tube of the second bridge arm and the lower switch tube of the first bridge arm to be simultaneously conducted for a first preset time, then a second current value can be acquired, the upper switch tube of the second bridge arm is turned off, the lower switch tube of the first bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switch tube of the second bridge arm and the lower switch tube of the first bridge arm form a follow current loop, and the lower switch tube of the first bridge arm is turned off after the second preset time is conducted.
The further improvement scheme is as follows: the bridge arms comprise a third bridge arm, an upper switch tube and a lower switch tube are arranged on the third bridge arm, the upper switch tube is connected with a positive direct-current bus, the lower switch tube is connected with a negative direct-current bus, a control circuit controls the upper switch tube of the first bridge arm and the lower switch tube of the third bridge arm to be simultaneously conducted for a first preset time, a third current value can be collected, the upper switch tube of the first bridge arm is turned off, the lower switch tube of the third bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switch tube of the first bridge arm and the lower switch tube of the third bridge arm form a follow current loop, and the lower switch tube of the third bridge arm is turned off after the second preset time is conducted; and the control circuit controls the upper switching tube of the third bridge arm and the lower switching tube of the first bridge arm to be simultaneously conducted for a first preset time, then a fourth current value can be acquired, the upper switching tube of the third bridge arm is turned off, the lower switching tube of the first bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the third bridge arm and the lower switching tube of the first bridge arm form a follow current loop, and the lower switching tube of the first bridge arm is turned off after the upper switching tube of the third bridge arm and the lower switching tube of the first bridge arm are conducted for a second.
The further improvement scheme is as follows: the control circuit controls the upper switching tube of the second bridge arm and the lower switching tube of the third bridge arm to be simultaneously conducted for first preset time, then a fifth current value can be acquired, the upper switching tube of the second bridge arm is turned off, the lower switching tube of the third bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the second bridge arm and the lower switching tube of the third bridge arm form a follow current loop, and the lower switching tube of the third bridge arm is turned off after the second preset time is conducted; and the control circuit controls the upper switching tube of the third bridge arm and the lower switching tube of the second bridge arm to be simultaneously conducted for a first preset time, then a sixth current value can be acquired, the upper switching tube of the third bridge arm is turned off, the lower switching tube of the second bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the third bridge arm and the lower switching tube of the second bridge arm form a follow current loop, and the lower switching tube of the second bridge arm is turned off after the second preset time is conducted.
The invention can also adopt the following technical scheme for solving the problems in the prior art: a brushless motor control mechanism comprising: the inverter circuit comprises a positive direct current bus, a negative direct current bus and at least two bridge arms, the bridge arms are a first bridge arm and a second bridge arm, the first bridge arm and the second bridge arm are connected between the positive direct current bus and the negative direct current bus, the first bridge arm and the second bridge arm are respectively provided with an upper switch tube and a lower switch tube, the upper switch tube is connected with the positive direct current bus, the lower switch tube is connected with the negative direct current bus, each lower switch tube is respectively connected with a diode in parallel in a reverse direction, the control circuit controls the upper switch tube and the lower switch tube of the first bridge arm to be conducted in at least one conducting state, the direct current bus current values in different states are adopted, the initial position of the rotor is determined according to the current values, the control circuit controls the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm to be conducted simultaneously for a first preset time, a first current value can be collected, and the upper switch tube of the first bridge arm is, and meanwhile, continuously conducting the lower switching tube of the second bridge arm, forming a follow current loop by the lower switching tube of the second bridge arm and the diode connected in parallel with the lower switching tube of the first bridge arm, and switching off the lower switching tube of the second bridge arm after conducting for a second preset time.
The further improvement scheme is as follows: the control circuit comprises a microprocessor MCU, an MOS drive module and a current sampling circuit.
The further improvement scheme is as follows: the current sampling circuit comprises a sampling resistor and a current detection circuit, and the sampling resistor is arranged on a negative direct current bus of the inverter circuit.
The further improvement scheme is as follows: the microprocessor MCU is connected with an MOS driving module, and the MOS driving module respectively controls the conduction of the switch tubes according to the information of the microprocessor MCU.
The further improvement scheme is as follows: the microprocessor MCU is provided with a storage unit, the current detection circuit is used for detecting the voltage at two ends of the sampling resistor so as to obtain the bus current value, the bus current value is amplified and transmitted to the microprocessor MCU, and the microprocessor stores the bus current values in different conduction states.
The further improvement scheme is as follows: the first predetermined time range is 40us to 200 us.
The further improvement scheme is as follows: the second predetermined time is not less than 160 us.
The further improvement scheme is as follows: the control circuit controls the upper switching tube of the second bridge arm and the lower switching tube of the first bridge arm to be simultaneously conducted for a first preset time, then a second current value can be acquired, the upper switching tube of the second bridge arm is turned off, the lower switching tube of the first bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the second bridge arm and the lower switching tube of the first bridge arm form a follow current loop, and the lower switching tube of the first bridge arm is turned off after the second preset time is conducted.
The further improvement scheme is as follows: the bridge arms comprise a third bridge arm, an upper switch tube and a lower switch tube are arranged on the third bridge arm, the upper switch tube is connected with a positive direct-current bus, the lower switch tube is connected with a negative direct-current bus, a control circuit controls the upper switch tube of the first bridge arm and the lower switch tube of the third bridge arm to be simultaneously conducted for a first preset time, a third current value can be acquired, the upper switch tube of the first bridge arm is turned off, the lower switch tube of the third bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switch tube of the first bridge arm and the lower switch tube of the third bridge arm form a follow current loop, and the lower switch tube of the third bridge arm is turned off after the second preset time is conducted; and the control circuit controls the upper switching tube of the third bridge arm and the lower switching tube of the first bridge arm to be simultaneously conducted for a first preset time, then a fourth current value can be acquired, the upper switching tube of the third bridge arm is turned off, the lower switching tube of the first bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the third bridge arm and the lower switching tube of the first bridge arm form a follow current loop, and the lower switching tube of the first bridge arm is turned off after the upper switching tube of the third bridge arm and the lower switching tube of the first bridge arm are conducted for a second preset.
The further improvement scheme is as follows: the control circuit controls the upper switching tube of the second bridge arm and the lower switching tube of the third bridge arm to be simultaneously conducted for first preset time, then a fifth current value can be acquired, the upper switching tube of the second bridge arm is turned off, meanwhile, the lower switching tube of the third bridge arm is continuously conducted, a diode connected in parallel with the lower switching tube of the second bridge arm and the lower switching tube of the third bridge arm form a follow current loop, and the lower switching tube of the third bridge arm is turned off after the second preset time is conducted; and the control circuit controls the upper switching tube of the third bridge arm and the lower switching tube of the second bridge arm to be simultaneously conducted for a first preset time, then a sixth current value can be acquired, the upper switching tube of the third bridge arm is turned off, the lower switching tube of the second bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the third bridge arm and the lower switching tube of the second bridge arm form a follow current loop, and the lower switching tube of the second bridge arm is turned off after the second preset time is conducted.
Compared with the prior art, the invention has the following beneficial effects: the invention comprises an inverter circuit and a control circuit, wherein the inverter circuit comprises a positive direct current bus, a negative direct current bus and at least two bridge arms, the bridge arms are a first bridge arm and a second bridge arm, the control circuit controls upper and lower switch tubes of the first bridge arm and the second bridge arm to be conducted in at least one conduction state and adopts direct current bus current values in different states, the control circuit controls the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm to be conducted simultaneously for a first preset time, the first current value can be collected, the upper switch tube of the first bridge arm is turned off, the lower switch tube of the second bridge arm is continuously conducted simultaneously, the lower switch tube of the second bridge arm and a diode connected in parallel with the lower switch tube of the first bridge arm form a follow current loop, the lower switch tube of the second bridge arm is turned off after the second preset time is conducted, the follow current direction is changed, peak voltage can be reduced, and the voltage applied to two ends of the switch tubes is, the selection requirement of the switching tube can be reduced, and the cost is reduced.
[ description of the drawings ]
The following detailed description of embodiments of the invention is provided in conjunction with the appended drawings:
FIG. 1 is a schematic diagram of the control mechanism of the brushless motor of the present invention;
FIG. 2 is a schematic view of the stator winding and rotor position of the brushless motor of the present invention;
FIG. 3 is a schematic diagram illustrating the flow of current when the UV phase of the brushless motor of the present invention is turned on;
FIG. 4 is a schematic current flow diagram of a brushless motor freewheel of the present invention;
FIG. 5 is a voltage waveform of freewheeling in accordance with the present invention;
FIG. 6 is a current flow diagram of a prior art freewheel;
fig. 7 is a voltage waveform of a prior art freewheel.
[ detailed description of the invention ]
The present invention will be described in further detail with reference to the accompanying drawings and embodiments.
Fig. 1 is a schematic diagram of a three-phase brushless motor control mechanism according to the present invention, wherein the brushless motor control mechanism includes a dc power supply, a brushless motor, a three-phase full-bridge inverter circuit, and a control circuit. The brushless motors are in star connection, and can be in triangular connection; the three-phase full-bridge inverter circuit inverts direct current provided by the direct current power supply into alternating current to supply power to a three-phase winding of the brushless motor; the control circuit comprises a microprocessor MCU, an MOS drive module and a current sampling circuit, wherein the MOS drive module responds to a control signal received from the microprocessor MCU to drive the switching tube of the three-phase full-bridge inverter circuit to be switched on and off.
The inverter circuit control of the two arms is explained as follows: the control mechanism of the brushless motor comprises an inverter circuit and a control circuit, wherein the inverter circuit comprises a positive direct current bus, a negative direct current bus, a first bridge arm and a second bridge arm, the first bridge arm and the second bridge arm are connected between the positive direct current bus and the negative direct current bus, an upper switching tube and a lower switching tube are respectively arranged on the first bridge arm and the second bridge arm, the upper switching tube is connected with the positive direct current bus, the lower switching tube is connected with the negative direct current bus, each upper switching tube and each lower switching tube are respectively connected with a diode in parallel in a reverse direction, in some structures, the diodes are parasitic diodes of MOS (metal oxide semiconductor) tubes or other transistors, in other structures, the diodes can be connected with other switching tubes in parallel, the control circuit controls the upper switching tube and the lower switching tube to be conducted in at least one conducting state and adopt direct current bus current values in different states, the control circuit controls the upper switching tube of the first bridge arm and the lower switching tube of the second bridge arm, the first current value can be collected, the upper switch tube of the first bridge arm is turned off, the lower switch tube of the second bridge arm is continuously conducted, the lower switch tube of the second bridge arm and the diode connected in parallel with the lower switch tube of the first bridge arm form a follow current loop, and the lower switch tube of the second bridge arm is turned off after the second preset time is conducted.
Referring to fig. 1, in the present embodiment, the inverter circuit includes three bridge arms, including a positive and negative dc bus, a first bridge arm, a second bridge arm, and a third bridge arm, where each bridge arm is connected between the positive and negative dc buses, and the first bridge arm includes a first switching tube Q1 (also called an upper switch) and a fourth switching tube Q4 (also called a lower switch) connected in series; the second bridge arm consists of a second switching tube Q2 (also called an upper switch) and a fifth switching tube Q5 (also called a lower switch) which are connected in series; the third bridge arm consists of a third switch tube Q3 (also called an upper switch) and a sixth switch tube Q6 (also called a lower switch) which are connected in series, and each upper switch tube and each lower switch tube are respectively connected with diodes D1-D6 in parallel in the reverse direction; the brushless motor comprises a first phase U, a second phase V and a third phase W, wherein one end of the three-phase winding is connected with one point, the other end of the first phase U is connected with the midpoint of the first bridge arm, the other end of the second phase V is connected with the midpoint of the second bridge arm, and the other end of the third phase W is connected with the midpoint of the third bridge arm.
The control circuit comprises a microprocessor MCU, an MOS drive module and a current sampling circuit, wherein the sampling circuit comprises a sampling resistor R1 arranged on a negative direct current bus and a current detection circuit connected to two ends of a sampling resistor R1, and the voltage at two ends of the sampling resistor R1 is detected, so that the current flowing through the bus is obtained, and the bus current is amplified and transmitted to the microprocessor MCU. The microprocessor MCU adopts a three-phase six-state two-to-two conduction mode, each state is that an upper switch tube of one bridge arm and a lower switch tube of any other bridge arm are two-to-two conducted, and an upper switch tube and a lower switch tube of the same bridge arm can not be conducted simultaneously, so that the inverter circuit can control the switch tubes to be conducted in the following six states respectively: turning on Q1Q5, turning on Q1Q6, turning on Q2Q4, turning on Q2Q6, turning on Q3Q4 and turning on Q3Q5, and switching the six states to realize phase change of the motor, please refer to FIG. 2, which is a schematic diagram of a stator winding structure and a rotor position of the motor, wherein the stator winding structure forms 6 sectors, each sector corresponds to a position area where the rotor is located, and each position area corresponds to the conduction of every two switching tubes. In the initial positioning, the microprocessor MCU controls the MOS driving module to conduct two UV phases (Q1 and Q5), samples a bus current once, sequentially conducts two VU phases (Q2 and Q4 are conducted), two UW phases (Q1 and Q6 are conducted), two WU phases (Q3 and Q4 are conducted), two VW phases (Q2 and Q6 are conducted), and two WV phases (Q3 and Q5 are conducted), samples bus current values Iuv, Ivu, Iuw, Iwu, Ivw and Iwu, respectively, calculates positive and negative current differences I1 | (Iuv-Ivu |, I2 | -Iuw-Iwu |, and I3 | -Ivw-Iwv |, compares the six bus current values and the three positive and negative current differences with a relationship between a current stored in a memory inside the microprocessor MCU and an initial position of the rotor (refer to a table), after the position is obtained, referring to a working switching tube (refer to table two) which needs to be opened and corresponds to the initial position of the rotor stored in the microprocessor MCU, as shown in fig. 2, if the initial position of the rotor is position 1, the microprocessor MCU controls the MOS driving module to open the switching tube Q1Q5 first, and then to be circularly turned on in sequence according to the sequence of Q1Q5, Q1Q6, Q2Q6, Q2Q4, Q3Q4, and Q3Q5, so that the rotor rotates counterclockwise, and if the rotor rotates clockwise, the switching tube is circularly turned on in the reverse sequence; if the initial position of the rotor is position 2, the microprocessor MCU controls the MOS drive module to open the switching tube Q1Q6, and then circularly conducts in the sequence of Q1Q6, Q2Q6, Q2Q4, Q3Q4, Q3Q5 and Q1Q5, so that the rotor rotates anticlockwise, and circularly conducts in the reverse sequence if the rotor rotates clockwise; and (3) detecting different initial positions of the rotor, firstly opening the switching tubes corresponding to the positions of the rotor according to the second meter, conducting according to the circulation sequence, detecting the zero crossing point of the back electromotive force through a back electromotive force detection circuit in the rotation process, determining the position of the rotor, and controlling the phase change of the rotor.
And the first table shows the position relation between each bus current and the rotor.
And the second table is a working switching tube which is corresponding to the position of each rotor and needs to be opened.
| Initial position of rotor | Working |
| Position | |
| 1 | Q1、Q5 |
| |
Q1、 |
| Position | |
| 3 | Q2、 |
| Position | |
| 4 | Q2、Q4 |
| Position 5 | Q3、 |
| Position | |
| 6 | Q3、Q5 |
When sampling current, switching tubes Q1Q5, Q2Q4, Q1Q6, Q3Q4, Q2Q6 and Q3Q5 need to be sequentially switched on, as shown in fig. 3, for a schematic diagram of current flow when the UV phase of the brushless motor is switched on, the switching tube Q1Q5 is switched on, current flows into the ground through a power supply anode BAT +, the switching tube Q1, a U-phase winding, a V-phase winding and the switching tube Q5, after the switching tube Q1Q5 is switched on for a period of time, the microprocessor MCU can sample the bus current Iuv, the current is sampled, the switching tube Q1Q5 needs to be switched off, the switching tube Q2Q4 is switched on, and the bus current Ivu is sampled. As shown in fig. 4, for the current flow direction of the freewheeling current in this embodiment, after the microprocessor MCU controls Q1Q5 to be turned on for 180us for the first predetermined time, the upper switch Q1 is turned off first, and the lower switch Q5 is turned on for 180us with a delay, at this time, because the current of the UV phase winding cannot suddenly change, the current forms a loop through the diode D4, the U phase winding, the V phase winding, and the switch Q5 to implement freewheeling, and after the current is consumed, the switch Q5 is turned off, at this time, the peak voltage value of the V phase is reduced to 26.6V as shown at line a of fig. 5. Then, according to the follow current mode, the switching tubes Q2Q4, Q1Q6, Q3Q4, Q2Q6 and Q3Q5 are continuously conducted, namely peak voltage can be reduced while six bus currents are sampled, voltage drop applied to two ends of the switching tubes is 26.6V, the switching tubes with withstand voltage of 30V can be selected, normal operation of the circuit can be guaranteed, and cost is saved.
When the two switching tubes in each state are conducted and switched, the control mechanism firstly disconnects the upper switching tube and simultaneously delays to conduct the lower switching tube, so that the diode which is connected in parallel with the lower switching tube of the bridge arm and corresponds to the upper switching tube in the state, the corresponding winding and the lower switching tube in the state form a follow current loop, the peak voltage is reduced, the terminal voltage of the switching tubes is pulled down, and according to the difference of circuits, the structure can reduce the peak voltage more, so that the requirement of the switching tubes can be reduced, the switching tube with lower withstand voltage is selected, and the cost is saved.
The invention also provides a brushless motor current sampling method, wherein the microprocessor MCU controls the MOS drive module to conduct UV two-phase (Q1 and Q5 conduction), VU two-phase (Q2 and Q4 conduction), UW two-phase (Q1 and Q6 conduction), WU two-phase (Q3 and Q4 conduction), VW two-phase (Q2 and Q6 conduction) and WV two-phase (Q3 and Q5 conduction), and bus current values Iuv, Ivu, Iiw, Ivw and Iwv are respectively sampled. The microprocessor controls the switch tube Q1Q5 to be conducted, when the switch tube Q1Q5 is conducted for 180us within the first preset time, the bus current Iuv is sampled, after the current Iuv is sampled, the upper switch tube Q1 is turned off firstly, the lower switch tube Q5 is kept to be conducted for 180us in a delayed mode, at the moment, because the current of the UV phase winding cannot be suddenly changed, the current forms a loop through the diode D4, the U phase winding, the V phase winding and the switch tube Q5, follow current is achieved, and after the current is consumed, the switch tube Q5 is turned off; the microprocessor controls the switch tube Q2Q4 to be conducted, when the switch tube Q2Q4 is conducted for 180us within the first preset time, the bus current Ivu is sampled, after the current Ivu is sampled, the upper switch tube Q2 is turned off firstly, the lower switch tube Q4 is kept to be conducted for 180us in a delayed mode, at the moment, the current forms a loop through the diode D5, the V-phase winding, the U-phase winding and the switch tube Q4, follow current is achieved, and after the current is consumed, the switch tube Q4 is turned off; the microprocessor controls the switch tube Q1Q6 to be conducted, when the switch tube Q1Q6 is conducted for 180us within the first preset time, the bus current Iuw is sampled, after the current Iuw is sampled, the upper switch tube Q1 is turned off firstly, the lower switch tube Q6 is kept to be conducted for 180us in a delayed mode, at the moment, the current forms a loop through the diode D4, the U-phase winding, the W-phase winding and the switch tube Q6, follow current is achieved, and after the current is consumed, the switch tube Q6 is turned off; the microprocessor controls the switch tube Q3Q4 to be conducted, when the switch tube Q3Q4 is conducted for 180us within the first preset time, the bus current Iwu is sampled, after the current Iwu is sampled, the upper switch tube Q3 is turned off firstly, the lower switch tube Q4 is kept to be conducted for 180us in a delayed mode, at the moment, the current forms a loop through a diode D6, a W-phase winding, a U-phase winding and the switch tube Q4, follow current is achieved, and after the current is consumed, the switch tube Q4 is turned off; the microprocessor controls the switch tube Q2Q6 to be conducted, when the switch tube Q2Q6 is conducted for 180us within the first preset time, the bus current Ivw is sampled, after the current Ivw is sampled, the upper switch tube Q2 is turned off firstly, the lower switch tube Q6 is kept to be conducted for 180us in a delayed mode, at the moment, the current forms a loop through the diode D5, the V-phase winding, the W-phase winding and the switch tube Q6, follow current is achieved, and after the current is consumed, the switch tube Q6 is turned off; the microprocessor controls the switch tube Q3Q5 to be conducted, when the switch tube Q3Q5 is conducted for 180us in the first preset time, the bus current Iwv is sampled, after the current Iwv is sampled, the upper switch tube Q3 is turned off firstly, the lower switch tube Q5 is kept to be conducted for 180us in a delayed mode, at the moment, the current forms a loop through the diode D6, the W-phase winding, the V-phase winding and the switch tube Q5, follow current is achieved, after the current is consumed, the switch tube Q5 is turned off, and 6 bus current values of the brushless motor can be sampled. The peak voltage is reduced, the terminal voltage of the switch tube is reduced, and the safety of the circuit is improved.
The invention relates to a brushless motor current sampling method, when two switch tubes in each state are conducted and switched, an upper switch tube is firstly disconnected, and a lower switch tube is conducted in a delayed manner, so that a diode which is connected in parallel with the lower switch tube of a bridge arm and corresponds to the upper switch tube in the state, a corresponding winding and the lower switch tube in the state form a follow current loop, peak voltage is reduced, and terminal voltage of the switch tubes is reduced.
The present invention is not limited to the above-described embodiments. It will be readily appreciated by those skilled in the art that many other alternatives to the brushless motor current sampling method and control mechanism of the present invention can be made without departing from the spirit and scope of the invention. The protection scope of the present invention is subject to the content of the claims.
Claims (14)
1. A brushless motor current sampling method, comprising: the inverter circuit comprises a positive direct current bus, a negative direct current bus and at least two bridge arms, the bridge arms are a first bridge arm and a second bridge arm, the first bridge arm and the second bridge arm are connected between the positive direct current bus and the negative direct current bus, an upper switch tube and a lower switch tube are respectively arranged on the first bridge arm and the second bridge arm, the upper switch tube is connected with the positive direct current bus, the lower switch tube is connected with the negative direct current bus, each lower switch tube is respectively connected with a diode in parallel in a reverse direction, and the control circuit controls the upper switch tube and the lower switch tube to be conducted in at least one conduction state and adopt direct current bus current values in different states; the method is characterized in that: the control circuit controls the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm to be simultaneously conducted for a first preset time, then a first current value can be acquired, the upper switch tube of the first bridge arm is turned off, the lower switch tube of the second bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switch tube of the first bridge arm and the lower switch tube of the second bridge arm form a follow current loop, and the lower switch tube of the second bridge arm is turned off after the second preset time is conducted.
2. The brushless motor current sampling method of claim 1, wherein: the control circuit controls the upper switch tube of the second bridge arm and the lower switch tube of the first bridge arm to be simultaneously conducted for a first preset time, then a second current value can be acquired, the upper switch tube of the second bridge arm is turned off, the lower switch tube of the first bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switch tube of the second bridge arm and the lower switch tube of the first bridge arm form a follow current loop, and the lower switch tube of the first bridge arm is turned off after the second preset time is conducted.
3. The brushless motor current sampling method of claim 1, wherein: the bridge arms comprise a third bridge arm, an upper switch tube and a lower switch tube are arranged on the third bridge arm, the upper switch tube is connected with a positive direct-current bus, the lower switch tube is connected with a negative direct-current bus, a control circuit controls the upper switch tube of the first bridge arm and the lower switch tube of the third bridge arm to be simultaneously conducted for a first preset time, a third current value can be collected, the upper switch tube of the first bridge arm is turned off, the lower switch tube of the third bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switch tube of the first bridge arm and the lower switch tube of the third bridge arm form a follow current loop, and the lower switch tube of the third bridge arm is turned off after the second preset time is conducted; and the control circuit controls the upper switching tube of the third bridge arm and the lower switching tube of the first bridge arm to be simultaneously conducted for a first preset time, then a fourth current value can be acquired, the upper switching tube of the third bridge arm is turned off, the lower switching tube of the first bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the third bridge arm and the lower switching tube of the first bridge arm form a follow current loop, and the lower switching tube of the first bridge arm is turned off after the upper switching tube of the third bridge arm and the lower switching tube of the first bridge arm are conducted for a second.
4. The brushless motor current sampling method of claim 3, wherein: the control circuit controls the upper switching tube of the second bridge arm and the lower switching tube of the third bridge arm to be simultaneously conducted for first preset time, then a fifth current value can be acquired, the upper switching tube of the second bridge arm is turned off, the lower switching tube of the third bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the second bridge arm and the lower switching tube of the third bridge arm form a follow current loop, and the lower switching tube of the third bridge arm is turned off after the second preset time is conducted; and the control circuit controls the upper switching tube of the third bridge arm and the lower switching tube of the second bridge arm to be simultaneously conducted for a first preset time, then a sixth current value can be acquired, the upper switching tube of the third bridge arm is turned off, the lower switching tube of the second bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the third bridge arm and the lower switching tube of the second bridge arm form a follow current loop, and the lower switching tube of the second bridge arm is turned off after the second preset time is conducted.
5. A brushless motor control mechanism comprising: the control circuit controls the upper and lower switch tubes to be conducted in at least one conduction state, adopts direct current bus current values in different states, and determines the initial position of the rotor according to the current values; the method is characterized in that: the control circuit controls the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm to be simultaneously conducted for a first preset time, then a first current value can be acquired, the upper switch tube of the first bridge arm is turned off, the lower switch tube of the second bridge arm is continuously conducted at the same time, the lower switch tube of the second bridge arm and the diode connected in parallel with the lower switch tube of the first bridge arm form a follow current loop, and the lower switch tube of the second bridge arm is turned off after the second preset time is conducted.
6. The brushless motor control mechanism of claim 5, wherein: the control circuit comprises a microprocessor MCU, an MOS drive module and a current sampling circuit.
7. The brushless motor control mechanism of claim 6, wherein: the current sampling circuit comprises a sampling resistor and a current detection circuit, and the sampling resistor is arranged on a negative direct current bus of the inverter circuit.
8. The brushless motor control mechanism of claim 5, wherein: the microprocessor MCU is connected with an MOS driving module, and the MOS driving module respectively controls the conduction of the switch tubes according to the information of the microprocessor MCU.
9. The brushless motor control mechanism of claim 7 or 8, wherein: the microprocessor MCU is provided with a storage unit, the current detection circuit is used for detecting the voltage at two ends of the sampling resistor so as to obtain the bus current value, the bus current value is amplified and transmitted to the microprocessor MCU, and the microprocessor stores the bus current values in different conduction states.
10. The brushless motor control mechanism of claim 5, wherein: the first predetermined time range is 40us to 200 us.
11. The brushless motor control mechanism of claim 5, wherein: the second predetermined time is not less than 160 us.
12. The brushless motor control mechanism of claim 5, wherein: the control circuit controls the upper switching tube of the second bridge arm and the lower switching tube of the first bridge arm to be simultaneously conducted for a first preset time, then a second current value can be acquired, the upper switching tube of the second bridge arm is turned off, the lower switching tube of the first bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the second bridge arm and the lower switching tube of the first bridge arm form a follow current loop, and the lower switching tube of the first bridge arm is turned off after the second preset time is conducted.
13. The brushless motor control mechanism of claim 5, wherein: the bridge arms comprise a third bridge arm, an upper switch tube and a lower switch tube are arranged on the third bridge arm, the upper switch tube is connected with a positive direct-current bus, the lower switch tube is connected with a negative direct-current bus, a control circuit controls the upper switch tube of the first bridge arm and the lower switch tube of the third bridge arm to be simultaneously conducted for a first preset time, a third current value can be acquired, the upper switch tube of the first bridge arm is turned off, the lower switch tube of the third bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switch tube of the first bridge arm and the lower switch tube of the third bridge arm form a follow current loop, and the lower switch tube of the third bridge arm is turned off after the second preset time is conducted; and the control circuit controls the upper switching tube of the third bridge arm and the lower switching tube of the first bridge arm to be simultaneously conducted for a first preset time, then a fourth current value can be acquired, the upper switching tube of the third bridge arm is turned off, the lower switching tube of the first bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the third bridge arm and the lower switching tube of the first bridge arm form a follow current loop, and the lower switching tube of the first bridge arm is turned off after the upper switching tube of the third bridge arm and the lower switching tube of the first bridge arm are conducted for a second preset.
14. The brushless motor control mechanism of claim 5 or 13, wherein: the control circuit controls the upper switching tube of the second bridge arm and the lower switching tube of the third bridge arm to be simultaneously conducted for first preset time, then a fifth current value can be acquired, the upper switching tube of the second bridge arm is turned off, meanwhile, the lower switching tube of the third bridge arm is continuously conducted, a diode connected in parallel with the lower switching tube of the second bridge arm and the lower switching tube of the third bridge arm form a follow current loop, and the lower switching tube of the third bridge arm is turned off after the second preset time is conducted; and the control circuit controls the upper switching tube of the third bridge arm and the lower switching tube of the second bridge arm to be simultaneously conducted for a first preset time, then a sixth current value can be acquired, the upper switching tube of the third bridge arm is turned off, the lower switching tube of the second bridge arm is continuously conducted at the same time, a diode connected in parallel with the lower switching tube of the third bridge arm and the lower switching tube of the second bridge arm form a follow current loop, and the lower switching tube of the second bridge arm is turned off after the second preset time is conducted.
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