WO2024007551A1 - 一种电机控制电路及控制方法 - Google Patents

一种电机控制电路及控制方法 Download PDF

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WO2024007551A1
WO2024007551A1 PCT/CN2022/141907 CN2022141907W WO2024007551A1 WO 2024007551 A1 WO2024007551 A1 WO 2024007551A1 CN 2022141907 W CN2022141907 W CN 2022141907W WO 2024007551 A1 WO2024007551 A1 WO 2024007551A1
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Prior art keywords
electromotive force
pwm signal
back electromotive
signal frequency
controller
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PCT/CN2022/141907
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English (en)
French (fr)
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王浩东
黄佳楠
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江苏东成工具科技有限公司
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Priority to DE112022001860.7T priority Critical patent/DE112022001860T5/de
Priority to US18/522,309 priority patent/US20240097596A1/en
Publication of WO2024007551A1 publication Critical patent/WO2024007551A1/zh

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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
    • H02P6/182—Circuit arrangements for detecting position without separate position detecting elements using back-emf in windings
    • 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
    • H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
    • H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
    • H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
    • H02P27/085—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency
    • 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
    • H02P6/08—Arrangements for controlling the speed or torque of a single motor
    • H02P6/085—Arrangements for controlling the speed or torque of a single motor in a bridge configuration

Definitions

  • the present invention relates to the technical field of motor control, and in particular to a control circuit and control method for motor PWM signals.
  • the PWM frequency In order to enable the motor to operate normally, the PWM frequency needs to be increased to 20KHz, that is, the speed exceeds 20KHz. High, the higher the PWM frequency. But for tools that implement constant speed control, when the speed is high and the torque is high, if a higher PWM frequency is still used and the PWM frequency does not reach the full duty cycle, the power device driving the brushless motor will If the switching frequency is fast, the loss will be very large and the temperature rise will be very high, affecting the life of the power device.
  • the purpose of the present invention is to provide a motor control circuit and control method with high accuracy and low power consumption.
  • a motor control circuit including: positive and negative power terminals, a drive circuit, a PWM signal generating circuit, a controller and a back electromotive force detection circuit.
  • the positive and negative terminals pass through
  • the drive circuit is connected to the motor.
  • the drive circuit is connected to the controller through a PWM signal generating circuit.
  • the controller controls the drive circuit by changing the frequency of the PWM signal.
  • the controller is connected to the controller through a back electromotive force detection circuit.
  • the motor is used to obtain back electromotive force parameters.
  • the controller stores the corresponding relationship between the back electromotive force parameters and the PWM signal frequency.
  • the controller receives the back electromotive force parameters and sends the corresponding PWM signal frequency to the drive circuit to drive the motor. .
  • a further improvement plan is: the motor includes three-phase windings, the controller controls the conduction of two-phase windings, the counter-electromotive force detection circuit detects the counter-electromotive force of the suspended phase winding, and the counter-electromotive force parameters include the amount of counter-electromotive force voltage change,
  • the change amount of the back electromotive force voltage is the difference between the back electromotive force voltages collected at every two adjacent commutation times.
  • a further improvement plan is: the corresponding relationship between the back electromotive force parameter and the PWM signal frequency includes multiple voltage change thresholds stored by the controller and the PWM signal frequencies corresponding to the multiple voltage change thresholds.
  • the multiple voltage change thresholds The threshold includes a first voltage change threshold and a second voltage change threshold, a first PWM signal frequency corresponding to the first voltage change threshold, and a second PWM signal frequency corresponding to the second voltage change threshold,
  • the first voltage change threshold is greater than the second voltage change threshold
  • the first PWM signal frequency is less than the second PWM signal frequency
  • the controller outputs the first PWM signal frequency to the drive circuit
  • the controller outputs the second PWM signal frequency to the drive circuit.
  • a further improvement plan is: the corresponding relationship between the back electromotive force parameter and the PWM signal frequency includes the corresponding functional relationship between the back electromotive force voltage change amount and the PWM signal frequency.
  • a further improvement plan is: the corresponding relationship between the back electromotive force parameters and the PWM signal frequency includes the corresponding relationship between the set speed, the back electromotive force voltage change amount and the PWM signal frequency.
  • a further improvement plan is: the motor includes three-phase windings, the controller controls the conduction of two-phase windings, the back electromotive force detection circuit detects the back electromotive force of the suspended phase winding, and the back electromotive force parameters include the back electromotive force freewheeling time,
  • the back electromotive force freewheeling time is the freewheeling time generated during each phase commutation.
  • a further improvement plan is: the corresponding relationship between the back electromotive force parameters and the PWM signal frequency includes multiple freewheeling time thresholds stored in the controller and the PWM signal frequencies corresponding to the multiple freewheeling time thresholds, and the multiple freewheeling time
  • the threshold includes a first freewheeling time threshold and a second freewheeling time threshold, a first PWM signal frequency corresponding to the first freewheeling time threshold, and a second PWM signal frequency corresponding to the second freewheeling time threshold,
  • the first freewheeling time threshold is less than the second freewheeling time threshold
  • the first PWM signal frequency is greater than the second PWM signal frequency
  • the The controller outputs a first PWM signal frequency to the drive circuit; when the freewheeling time is greater than the second freewheeling time threshold, the controller outputs a second PWM signal frequency to the drive circuit.
  • a further improvement plan is: the corresponding relationship between the back electromotive force parameter and the PWM signal frequency includes the corresponding functional relationship between the freewheeling time and the PWM signal frequency.
  • a further improvement plan is: the corresponding relationship between the back electromotive force parameters and the PWM signal frequency includes the corresponding relationship between the set speed, freewheeling time and the PWM signal frequency.
  • a motor control method includes: step 1, select the set speed of the tool; step 2, the controller obtains the back electromotive force parameters through the back electromotive force detection circuit ; Step 3, the controller compares the back electromotive force parameter with the corresponding relationship between the internally stored back electromotive force parameter and the PWM signal frequency to select the corresponding PWM signal frequency to the drive circuit to drive the motor.
  • the controller is connected to the motor through a back electromotive force detection circuit to obtain the back electromotive force parameters, the controller stores the corresponding relationship between the back electromotive force parameters and the frequency of the PWM signal, and the controller receives the back electromotive force Parameters and sends the corresponding PWM signal to the drive circuit to drive the motor, directly obtains the motor parameters to change the signal of the drive motor, and can meet the normal operation of the motor at high speed and heavy load, with high accuracy and low power consumption.
  • Figure 1 is a circuit diagram of the motor control circuit of the present invention
  • Figure 2 is a waveform diagram of the back electromotive force and bus current of the motor of the present invention
  • Figure 3 is a control flow chart of the first embodiment of the present invention.
  • Figure 4 is a control flow chart of the second embodiment of the present invention.
  • the motor control circuit includes positive and negative terminals of a power supply.
  • the positive and negative terminals are connected to the motor 2 through a drive circuit 1.
  • the drive circuit 1 The PWM signal generating circuit 3 is connected to the controller 4.
  • the rotation speed setting module 5 is connected to the controller 4 for the user to select the appropriate motor gear.
  • the controller 4 is connected to the controller 4 through the back electromotive force detection circuit 6.
  • the motor 2 obtains the counter electromotive force parameters.
  • the controller 4 stores the corresponding relationship between the counter electromotive force parameters and the frequency of the PWM signal.
  • the controller 4 receives the counter electromotive force parameters and sends the corresponding PWM signal to the drive circuit 1 to drive the Described motor 2.
  • the motor 2 is a brushless motor.
  • the drive circuit 1 includes a first bridge arm, a second bridge arm, and a third bridge arm. Each bridge arm is connected to Between the positive and negative terminals of the power supply, the first bridge arm is composed of the first switch Q1 (also called the upper switch) and the fourth switch Q4 (also called the lower switch) connected in series; the second bridge arm is composed of the series connected The second switch tube Q2 (also called the upper switch) and the fifth switch tube Q5 (also called the lower switch) are composed of; the third bridge arm is composed of the third switch tube Q3 (also called the upper switch) and the sixth switch tube Q6 connected in series.
  • the first switching tube Q1 to the sixth switching tube Q6 are respectively connected in parallel with diodes for freewheeling, and the three-phase windings U, V, and W of the motor 2 are connected to each bridge arm respectively.
  • the drive circuit 1 can control the switch tube conduction in the following six states.
  • Q1Q5 is on, Q1Q6 is on, Q2Q4 is on, Q2Q6 is on, Q3Q4 is on, Q3Q5 is on, and the corresponding windings UV, UW, VU, VW, WU, and WV are energized in sequence, which is achieved by switching between six states.
  • the commutation of the motor 2 causes current to flow through each coil in a sequential manner.
  • the magnetic field generated by the current flow through the coil interacts with the permanent magnets of the rotor, and the magnetic poles of the permanent magnet rotor change to cause rotation.
  • the back electromotive force detection circuit 6 detects the back electromotive force of the floating phase winding.
  • the PWM signal includes an ON phase and an OFF phase.
  • the duration of one ON phase and one OFF phase is the PWM signal cycle, and the reciprocal of the cycle is the frequency.
  • the controller 4 changes the frequency of the PWM signal through the back electromotive force parameter.
  • FIGS. 2 and Figure 3 they are the back electromotive force and bus current waveform diagram of the C-phase winding of the motor and the control flow chart of the first embodiment.
  • the back electromotive force parameter includes the change amount of the back electromotive force voltage.
  • the change amount of the back electromotive force voltage is the difference between the back electromotive force voltages collected at every two adjacent commutation times.
  • the corresponding relationship between the back electromotive force parameter and the frequency of the PWM signal includes The controller 4 stores multiple voltage change thresholds and corresponding PWM signal frequencies.
  • the multiple voltage change thresholds include a first voltage change threshold and a second voltage change threshold, and the first voltage change threshold.
  • the first PWM signal frequency corresponding to the threshold value, the second PWM signal frequency corresponding to the second voltage change amount threshold, the first voltage change amount threshold value is greater than the second voltage change amount threshold value, the first PWM signal The frequency is less than the second PWM signal frequency, and when the back electromotive force voltage change is greater than the first voltage change threshold, the controller 4 outputs the first PWM signal frequency to the drive circuit 1; when the back electromotive force When the voltage variation is greater than the second back electromotive force threshold, the controller 4 outputs a second PWM signal frequency to the drive circuit 1 .
  • the specific control process includes: Step 1, set the speed through the speed setting module 5, and the motor starts with the initial PWM signal; Step 2, enter the PWM adjustment entrance to adjust the PWM signal frequency; Step 3, determine whether the sampling time has been reached, If so, proceed to step 4 to collect the back electromotive force voltage change, such as the back electromotive force voltage difference between commutation time a and commutation time b; step 5, gradually compare the back electromotive force voltage change with the voltage change threshold, If the change amount of the back electromotive force voltage is greater than the first voltage change threshold ⁇ V1, such as 3V, it is judged whether it meets the current constraint conditions.
  • Fpwm is the PWM frequency
  • Tpwm is the PWM period
  • Duty is the PWM duty cycle
  • N is the current mechanical speed of the motor
  • p is the number of motor pole pairs
  • Tm is the current sector time of the motor; if it matches, set the corresponding PWM signal frequency PWM1, such as 12500Hz, to the drive circuit 1, then return to step 2, enter the PWM adjustment entrance to continue collecting, if it does not meet the current constraints, Directly return to step 2; if the back electromotive force voltage change ⁇ V is not greater than the first voltage change threshold ⁇ V1, then determine whether it is greater than the second voltage change threshold ⁇ V2, such as 2V. If it is greater than the second voltage change threshold ⁇ V2, then determine whether Meets the current constraints.
  • the corresponding relationship between the back electromotive force parameter and the PWM signal frequency may include the corresponding functional relationship between the back electromotive force voltage change amount and the PWM signal frequency.
  • the corresponding relationship between the back electromotive force parameters and the PWM signal frequency includes the corresponding table relationship between the set speed, the back electromotive force voltage change amount, and the PWM signal frequency. That is, at the set speed, through different back electromotive force voltage changes The amount can correspond to the selected PWM signal frequency.
  • the values in the table can be more detailed. If the back electromotive force voltage change is less than the minimum voltage change threshold, it is set as the initial PWM signal.
  • the table is as follows:
  • the back electromotive force parameters include the controller 4 storing multiple A freewheeling time threshold and a corresponding PWM signal frequency
  • the plurality of freewheeling time thresholds include a first freewheeling time threshold and a second freewheeling time threshold, and a first PWM signal corresponding to the first freewheeling time threshold frequency
  • the second PWM signal frequency corresponding to the second freewheeling time threshold is greater than the second freewheeling time threshold
  • the first PWM signal frequency is less than the second PWM Signal frequency
  • the controller 4 outputs the first PWM signal frequency to the drive circuit 1; when the freewheeling time is greater than the second freewheeling time threshold , the controller 4 outputs the second PWM signal frequency to the drive circuit 1 .
  • the specific control process includes: Step 1, set the speed through the speed setting module 5, and the motor 2 starts with the initial PWM; Step 2, enter the PWM adjustment entrance to adjust the PWM signal frequency; Step 3, determine whether the sampling time has been reached, If so, enter step 4 to collect the freewheeling time; step 5, gradually compare the freewheeling time ⁇ t with the freewheeling time threshold. If the freewheeling time ⁇ t is greater than the first freewheeling time threshold ⁇ t1, such as 40us, determine whether it meets the current
  • Fpwm is the PWM frequency
  • Tpwm is the PWM period
  • Duty is the PWM duty cycle
  • N is the current mechanical speed of the motor
  • p is the number of motor pole pairs
  • Tm is the current sector time of the motor; if it matches, set the corresponding PWM signal frequency PWM1, such as 12500Hz, to the drive circuit 1, then return to step 2, enter the PWM adjustment entrance to continue collecting, if it does not meet the current constraints, Directly return to step 2; if the freewheeling time ⁇ t is not greater than the first freewheeling time threshold ⁇ t1, then determine whether it is greater than the second freewheeling time threshold ⁇ t2, such as 35us.
  • the second freewheeling time threshold ⁇ t2 determines whether it meets the current If the constraints are met, set the corresponding PWM signal frequency PWM2, such as 16000Hz, and then return to step 2; if it is not greater than the second freewheeling time threshold ⁇ t2, continue to determine whether it is greater than the third freewheeling time threshold ⁇ t3, and so on, If the conditions are not met, that is, when the freewheeling time is less than the minimum freewheeling time threshold, it is set as the initial PWM signal.
  • the corresponding relationship between the back electromotive force parameters and the PWM signal frequency includes the corresponding table relationship between the set speed, freewheeling time and PWM signal frequency. That is, under the set speed, the corresponding freewheeling time can be selected according to the set speed. PWM signal frequency, the values in the table can be more detailed. If the freewheeling time is less than the minimum freewheeling time threshold, it is set to the initial PWM signal.
  • the table is as follows:
  • the controller of the present invention is connected to the motor through a back electromotive force detection circuit to obtain the back electromotive force parameters.
  • the controller stores the corresponding relationship between the back electromotive force parameters and the frequency of the PWM signal.
  • the controller receives the back electromotive force parameters and sends the corresponding PWM signal to the drive circuit for driving.
  • Motor directly obtains the parameters of the motor to change the signal driving the motor, and can meet the normal operation of the motor at high speed and heavy load, with high accuracy and low power consumption.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
  • Control Of Ac Motors In General (AREA)

Abstract

本发明公开了一种电机控制电路及控制方法，包括：电源、驱动电路、PWM信号产生电路、控制器及反电动势检测电路，电源通过驱动电路连接于电机，驱动电路通过PWM信号产生电路连接于控制器，控制器通过改变PWM信号频率以对驱动电路进行控制，控制器通过反电动势检测电路连接于电机以获取反电动势参数，控制器存储有反电动势参数与PWM信号频率的对应关系，控制器接收反电动势参数并发出对应的PWM信号给驱动电路以驱动电机。本发明通过直接获取电机的参数以改变驱动电机的信号，且能满足电机在高速重载时的正常运行，精准度高且功耗低。

Description

一种电机控制电路及控制方法 【技术领域】
本发明涉及一种电机控制的技术领域，特别涉及一种电机PWM信号的控制电路及控制方法。
【背景技术】
现有的无刷电机一般都使用PWM驱动，当电机转速比较低时，使用较低的PWM频率，而转速升高时，使用较高的PWM频率，这是因为，在一些无刷电机的无感控制时，对PWM的启动的最小有效脉宽以及最小的启动占空比有要求，例如：启动占空比不能超过10％，最小脉宽时间是10us，则启动时的PWM频率需要为10KHz，但是如果上述电机正常运行时，转速非常高，例如超过了200000RPM，则10KHz的频率是无法满足运行要求的，为了使电机能够正常运行，此时需要把PWM的频率提高到20KHz，即转速越高，PWM频率越高。但对于实现恒速控制的工具来说，当转速较高，扭矩也较高时，如果仍然使用较高的PWM频率，并且PWM频率没有到满占空比，此时驱动无刷电机的功率器件开关频率快，损耗会非常大，温升会很高，影响功率器件的寿命。
请参阅于2022年05月10日公告的中国发明专利第CN111657787B号，其揭示了控制单元在由电流检测单元检测出的电动机功率(电流值)相对较大时，将PWM频率设定得相对较小，在检测到的电动机功率(电流值)相对较小时，将PWM频率设定得相对较大，根据与该功率阈值(电流阈值)的大小的比较结果来设定PWM频率的大小，能够抑制开关元件SW1的开关损耗。但获取电机的功率属于间接性地反映电机的工况，不能精准的反映电机的实际工况，精准度不高。
因此，有必要设计一种精准度高且功耗低的电机控制电路及控制方法，以解决上述问题。
【发明内容】
针对现有技术的不足，本发明的目的在于提供一种精准度高且功耗低的电机控制电路及控制方法。
本发明解决现有技术问题可采用如下技术方案：一种电机控制电路，包括：电源正、负极端子、驱动电路、PWM信号产生电路、控制器及反电动势检测电路，所述正、负极端子通过驱动电路连接于电机，所述驱动电路通过PWM信号产生电路连接于控制器，所述控制器通过改变PWM信号频率以对所述驱动电路进行控制，所述控制器通过反电动势检测电路连接于所述电机以获取反电动势参数，所述控制器存储有反电动势参数与PWM信号频率的对应关系，所述控制器接收反电动势参数并发出对应的PWM信号频率给所述驱动电路以驱动所述电机。
进一步改进方案为：所述电机包括三相绕组，所述控制器控制两相绕组导通，所述反电动势检测电路检测悬空相绕组的反电动势，所述反电动势参数包括反电动势电压变化量，所述反电动势电压变化量为每相邻两个换相时间采集的反动势电压之间的差值。
进一步改进方案为：反电动势参数与PWM信号频率的对应关系包括所述控制器存储的多个电压变化量阈值及所述多个电压变化量阈值对应的PWM信号频率，所述多个电压变化量阈值包括第一电压变化量阈值及第二电压变化量阈值，与所述第一电压变化量阈值对应的第一PWM信号频率，与所述第二电压变化量阈值对应的第二PWM信号频率，所述第一电压变化量阈值大于所述第二电压变化量阈值，所述第一PWM信号频率小于所述第二PWM信号频率，当反电 动势电压变化量大于所述第一电压变化量阈值时，所述控制器输出第一PWM信号频率给所述驱动电路；当所述反电动势电压变化量大于所述第二反电动势阈值时，所述控制器输出第二PWM信号频率给所述驱动电路。
进一步改进方案为：反电动势参数与PWM信号频率的对应关系包括反电动势电压变化量与PWM信号频率的对应函数关系，所述函数关系为Fpwm＝f(ΔV)，所述PWM信号频率与所述反电动势电压变化量呈反比关系。
进一步改进方案为：反电动势参数与PWM信号频率的对应关系包括设定转速、反电动势电压变化量及PWM信号频率的对应关系。
进一步改进方案为：所述电机包括三相绕组，所述控制器控制两相绕组导通，所述反电动势检测电路检测悬空相绕组的反电动势，所述反电动势参数包括反电动势续流时间，所述反电动势续流时间为每次换相时产生的续流时间。
进一步改进方案为：反电动势参数与PWM信号频率的对应关系包括所述控制器存储的多个续流时间阈值及所述多个续流时间阈值对应的PWM信号频率，所述多个续流时间阈值包括第一续流时间阈值及第二续流时间阈值，与所述第一续流时间阈值对应的第一PWM信号频率，与所述第二续流时间阈值对应的第二PWM信号频率，所述第一续流时间阈值小于所述第二续流时间阈值，所述第一PWM信号频率大于所述第二PWM信号频率，当续流时间大于所述第一续流时间阈值时，所述控制器输出第一PWM信号频率给所述驱动电路；当续流时间大于所述第二续流时间阈值时，所述控制器输出第二PWM信号频率给所述驱动电路。
进一步改进方案为：反电动势参数与PWM信号频率的对应关系包括续流时间与PWM信号频率的对应函数关系，所述函数关系为Fpwm＝f(Δt)，所述PWM信号频率与所述续流时间呈反比关系。
进一步改进方案为：反电动势参数与PWM信号频率的对应关系包括设定转速、续流时间及PWM信号频率的对应关系。
本发明解决现有技术问题还可采用如下技术方案：一种电机控制方法，所述控制方法包括：步骤1，选择工具的设定转速；步骤2，控制器通过反电动势检测电路获取反电动势参数；步骤3，控制器将反电动势参数与内部存储的反电动势参数与PWM信号频率的对应关系进行比较，以选择对应的PWM信号频率给所述驱动电路以驱动所述电机。
与现有技术相比，本发明具有如下有益效果：控制器通过反电动势检测电路连接于电机以获取反电动势参数，控制器存储有反电动势参数与PWM信号频率的对应关系，控制器接收反电动势参数并发出对应的PWM信号给驱动电路以驱动电机，直接获取电机的参数以改变驱动电机的信号，且能满足电机在高速重载时的正常运行，精准度高且功耗低。
【附图说明】
下面结合附图对本发明的具体实施方式做进一步详细的说明:
图1是本发明电机控制电路的电路图；
图2是本发明电机的反电动势及母线电流波形图；
图3是本发明第一实施例的控制流程图；
图4是本发明第二实施例的控制流程图。
图中附图标记的含义：
1、驱动电路2、电机3、PWM信号产生电路4、控制器5、转速设
定模块6、反电动势检测电路
【具体实施方式】
下面结合附图和实施方式对本发明作进一步详细说明。
请参阅图1所示，为本发明涉及的一种电机控制电路，所述电机控制电路包括电源正、负极端子，所述正、负极端子通过驱动电路1连接于电机2，所述驱动电路1通过PWM信号产生电路3连接于控制器4，转速设定模块5连接于所述控制器4，以供用户选择合适的电机档位，所述控制器4通过反电动势检测电路6连接于所述电机2以获取反电动势参数，所述控制器4存储有反电动势参数与PWM信号频率的对应关系，所述控制器4接收反电动势参数并发出对应的PWM信号给所述驱动电路1以驱动所述电机2。
所述电机2为无刷电机，本实施方式中，以三相绕组星形连接为例，所述驱动电路1包括第一桥臂、第二桥臂、第三桥臂，每个桥臂连接于电源正、负极端子之间，第一桥臂由串联连接的第一开关管Q1(也称上开关)和第四开关管Q4(也称下开关)组成；第二桥臂由串联连接的第二开关管Q2(也称上开关)和第五开关管Q5(也称下开关)组成；第三桥臂由串联连接的第三开关管Q3(也称上开关)和第六开关管Q6(也称下开关)组成，所述第一开关管Q1至所述第六开关管Q6分别并联有二极管以进行续流，电机2的三相绕组U、V、W分别连接于每个桥臂的中点，所述控制器4发送PWM信号至所述PWM信号产生电路3，所述PWM信号产生电路3控制所述驱动电路1的其中一个桥臂的上开关管以及其他任一桥臂的下开关管两两导通，同一桥臂的上下两个开关管不可同时导通，以控制每次两相绕组导通，因此，该驱动电路1可以分别以以下六种状态控制开关管导通：Q1Q5导通、Q1Q6导通、Q2Q4导通、Q2Q6导通、Q3Q4导通、Q3Q5导通，对应的绕组UV、UW、VU、VW、WU、WV依次得电，通过六种状态的切换实现所述电机2的换相，使电流以顺序的方式流过每个线圈，通过线圈的电流流动产生的磁场与转子的永磁体相互作用，永磁体转子的磁极改变从而发生转动。所述反电动势检测电路6检测悬空相绕组的反电动势。由于换 相时，绕组上存在能量，因此需通过对应的二极管进行续流，以消耗该能量，根据不同的负载状况，续流时间不同。PWM信号包括ON阶段及OFF阶段，一个所述ON阶段及一个所述OFF阶段的持续时间为PWM信号周期，周期的倒数为频率，所述控制器4通过反电动势参数来改变PWM信号的频率。
如图2及图3所示，为电机C相绕组的反电动势及母线电流波形图以及第一实施例的控制流程图，本实施方式中，由于负载增大，瞬时电流会增大，流过开关管的压降就越大，即反动势电压会有变化。所述反电动势参数包括反电动势电压变化量，所述反电动势电压变化量为每相邻两个换相时间采集的反动势电压之间的差值，反电动势参数与PWM信号频率的对应关系包括所述控制器4存储多个电压变化量阈值及对应的PWM信号频率，所述多个电压变化量阈值包括第一电压变化量阈值及第二电压变化量阈值，与所述第一电压变化量阈值对应的第一PWM信号频率，与所述第二电压变化量阈值对应的第二PWM信号频率，所述第一电压变化量阈值大于所述第二电压变化量阈值，所述第一PWM信号频率小于所述第二PWM信号频率，当反电动势电压变化量大于所述第一电压变化量阈值时，所述控制器4输出第一PWM信号频率给所述驱动电路1；当所述反电动势电压变化量大于所述第二反电动势阈值时，所述控制器4输出第二PWM信号频率给所述驱动电路1。其具体的控制流程包括：步骤1，通过转速设定模块5设定转速，电机以初始PWM信号启动；步骤2，进入PWM调整入口，进行PWM信号频率调节；步骤3，判断是否到达采样时间，是则进入步骤4，采集反电动势电压变化量，如换相时间a及换相时间b两点之间的反电动势电压差；步骤5，将反电动势电压变化量逐步与电压变化量阈值比较，若反电动势电压变化量大于第一电压变化量阈值ΔV1，如3V时，则判断是否符合当前约束条件，该约束条件为：(1)1/Fpwm＝Tpwm；
(2)(60/(N*p))/6＝Tm；
(3)Tpwm≤Tm*duty；
其中：
Fpwm为PWM频率
Tpwm为PWM周期
Duty为PWM占空比
N为电机当前机械转速
p为电机极对数
Tm为电机当前的扇区时间；若符合，则设置对应的PWM信号频率PWM1，如12500Hz，给所述驱动电路1，然后返回步骤2，进入PWM调整入口继续采集，若不符合当前约束条件，直接返回步骤2；若反电动势电压变化量ΔV不大于第一电压变化量阈值ΔV1，则判断是否大于第二电压变化量阈值ΔV2，如2V，若大于第二电压变化量阈值ΔV2，则判断是否符合当前约束条件，若符合，则设置对应的PWM信号频率PWM2，如16000Hz，然后返回步骤2；若不大于第二电压变化量阈值ΔV2，则继续判断是否大于第三电压变化量阈值ΔV3，以此类推，若均不满足条件，即反电动势电压变化量ΔV小于最小电压变化量阈值时，则设为初始PWM信号。
另一种方式中，反电动势参数与PWM信号频率的对应关系可包括反电动势电压变化量与PWM信号频率的对应函数关系，通过测试或仿真的方法确定所述函数关系为Fpwm＝f(ΔV)，所述PWM信号频率与所述反电动势电压变化量呈反比关系，即所述反电动势电压变化量越大，所述PWM信号频率越小。
另一种方式中，反电动势参数与PWM信号频率的对应关系包括设定转速、反电动势电压变化量及PWM信号频率的对应建表关系，即在设定转速下，通过 不同的反电动势电压变化量可对应选择PWM信号频率，当然，所述表格的数值可以更细化，若反电动势电压变化量小于最小电压变化量阈值时，则设为初始PWM信号，表格如下所示：
  ΔV1＝3V ΔV2＝2V ΔV3＝1V ......
80000RPM 12500Hz 16000Hz 20000Hz ......
67500RPM 11500Hz 14500Hz 17500Hz ......
55000RPM 10000Hz 12500Hz 16000Hz ......
如图2及图4所示，为电机C相绕组的反电动势及母线电流波形图以及第二实施例的控制流程图，本实施方式中，所述反电动势参数包括所述控制器4存储多个续流时间阈值及对应的PWM信号频率，所述多个续流时间阈值包括第一续流时间阈值及第二续流时间阈值，与所述第一续流时间阈值对应的第一PWM信号频率，与所述第二续流时间阈值对应的第二PWM信号频率，所述第一续流时间阈值大于所述第二续流时间阈值，所述第一PWM信号频率小于所述第二PWM信号频率，当续流时间大于所述第一续流时间阈值时，所述控制器4输出第一PWM信号频率给所述驱动电路1；当续流时间大于所述第二续流时间阈值时，所述控制器4输出第二PWM信号频率给所述驱动电路1。其具体的控制流程包括：步骤1，通过转速设定模块5设定转速，电机2以初始PWM启动；步骤2，进入PWM调整入口，进行PWM信号频率调节；步骤3，判断是否到达采样时间，是则进入步骤4，采集续流时间；步骤5，将续流时间Δt逐步与续流时间阈值比较，若续流时间Δt大于第一续流时间阈值Δt1，如40us时，则判断是否符合当前约束条件，该约束条件为：(1)1/Fpwm＝Tpwm；
(2)(60/(N*p))/6＝Tm；
(3)Tpwm≤Tm*duty；
其中：
Fpwm为PWM频率
Tpwm为PWM周期
Duty为PWM占空比
N为电机当前机械转速
p为电机极对数
Tm为电机当前的扇区时间；若符合，则设置对应的PWM信号频率PWM1，如12500Hz，给所述驱动电路1，然后返回步骤2，进入PWM调整入口继续采集，若不符合当前约束条件，直接返回步骤2；若续流时间Δt不大于第一续流时间阈值Δt1，则判断是否大于第二续流时间阈值Δt2，如35us，若大于第二续流时间阈值Δt2，则判断是否符合当前约束条件，若符合，则设置对应的PWM信号频率PWM2，如16000Hz然后返回步骤2；若不大于第二续流时间阈值Δt2，则继续判断是否大于第三续流时间阈值Δt3，以此类推，若均不满足条件，即续流时间小于最小续流时间阈值时，则设为初始PWM信号。
另一种方式中，反电动势参数与PWM信号频率的对应关系可包括续流时间与PWM信号频率的对应函数关系，通过测试或仿真的方法确定所述函数关系为Fpwm＝f(Δt)，所述PWM信号频率与所述续流时间呈反比关系，即所述续流时间越大，所述PWM信号频率越小。
另一种方式中，反电动势参数与PWM信号频率的对应关系包括设定转速、续流时间及PWM信号频率的对应建表关系，即在设定转速下，通过不同的续流时间可对应选择PWM信号频率，所述表格的数值可以更细化，若续流时间小于最小续流时间阈值时，则设为初始PWM信号，表格如下所示：
  Δt1＝40us Δt2＝35us Δt3＝30us ......
80000RPM 12500Hz 16000Hz 20000Hz ......
67500RPM 11500Hz 14500Hz 17500Hz ......
55000RPM 10000Hz 12500Hz 16000Hz ......
本发明控制器通过反电动势检测电路连接于电机以获取反电动势参数，控制器存储有反电动势参数与PWM信号频率的对应关系，控制器接收反电动势参数并发出对应的PWM信号给驱动电路以驱动电机，直接获取电机的参数以改变驱动电机的信号，且能满足电机在高速重载时的正常运行，精准度高且功耗低。
本发明不局限于上述具体实施方式。本领域普通技术人员可以很容易地理解到，在不脱离本发明原理和范畴的前提下，本发明的电机控制电路及控制方法还有其他很多的替代方案。本发明的保护范围以权利要求书的内容为准。

Claims (10)

  1. 一种电机控制电路，包括：电源正、负极端子、驱动电路、PWM信号产生电路、控制器及反电动势检测电路，所述正、负极端子通过驱动电路连接于电机，所述驱动电路通过PWM信号产生电路连接于控制器，所述控制器通过改变PWM信号频率以对所述驱动电路进行控制；其特征在于：所述控制器通过反电动势检测电路连接于所述电机以获取反电动势参数，所述控制器存储有反电动势参数与PWM信号频率的对应关系，所述控制器接收反电动势参数并发出对应的PWM信号频率给所述驱动电路以驱动所述电机。
  2. 根据权利要求1所述的电机控制电路，其特征在于：所述电机包括三相绕组，所述控制器控制两相绕组导通，所述反电动势检测电路检测悬空相绕组的反电动势，所述反电动势参数包括反电动势电压变化量，所述反电动势电压变化量为每相邻两个换相时间采集的反动势电压之间的差值。
  3. 根据权利要求2所述的电机控制电路，其特征在于：反电动势参数与PWM信号频率的对应关系包括所述控制器存储的多个电压变化量阈值及所述多个电压变化量阈值对应的PWM信号频率，所述多个电压变化量阈值包括第一电压变化量阈值及第二电压变化量阈值，与所述第一电压变化量阈值对应的第一PWM信号频率，与所述第二电压变化量阈值对应的第二PWM信号频率，所述第一电压变化量阈值大于所述第二电压变化量阈值，所述第一PWM信号频率小于所述第二PWM信号频率，当反电动势电压变化量大于所述第一电压变化量阈值时，所述控制器输出第一PWM信号频率给所述驱动电路；当所述反电动势电压变化量大于所述第二反电动势阈值时，所述控制器输出第二PWM信号频率给所述驱动电路。
  4. 根据权利要求2所述的电机控制电路，其特征在于：反电动势参数与PWM信号频率的对应关系包括反电动势电压变化量与PWM信号频率的对应函数关系，所述函数关系为Fpwm＝f(ΔV)，所述PWM信号频率与所述反电动势电压变化量呈反比关系。
  5. 根据权利要求2所述的电机控制电路，其特征在于：反电动势参数与PWM信号频率的对应关系包括设定转速、反电动势电压变化量及PWM信号频率的对应关系。
  6. 根据权利要求1所述的电机控制电路，其特征在于：所述电机包括三相绕组，所述控制器控制两相绕组导通，所述反电动势检测电路检测悬空相绕组的反电动势，所述反电动势参数包括反电动势续流时间，所述反电动势续流时间为每次换相时产生的续流时间。
  7. 根据权利要求6所述的电机控制电路，其特征在于：反电动势参数与PWM信号频率的对应关系包括所述控制器存储的多个续流时间阈值及所述多个续流时间阈值对应的PWM信号频率，所述多个续流时间阈值包括第一续流时间阈值及第二续流时间阈值，与所述第一续流时间阈值对应的第一PWM信号频率，与所述第二续流时间阈值对应的第二PWM信号频率，所述第一续流时间阈值大于所述第二续流时间阈值，所述第一PWM信号频率小于所述第二PWM信号频率，当续流时间大于所述第一续流时间阈值时，所述控制器输出第一PWM信号频率给所述驱动电路；当续流时间大于所述第二续流时间阈值时，所述控制器输出第二PWM信号频率给所述驱动电路。
  8. 根据权利要求6所述的电机控制电路，其特征在于：反电动势参数与PWM 信号频率的对应关系包括续流时间与PWM信号频率的对应函数关系，所述函数关系为Fpwm＝f(Δt)，所述PWM信号频率与所述续流时间呈反比关系。
  9. 根据权利要求6所述的电机控制电路，其特征在于：反电动势参数与PWM信号频率的对应关系包括设定转速、续流时间及PWM信号频率的对应关系。
  10. 一种电机控制方法，其特征在于，所述控制方法包括：
    步骤1，选择工具的设定转速；
    步骤2，控制器通过反电动势检测电路获取反电动势参数；
    步骤3，控制器将反电动势参数与内部存储的反电动势参数与PWM信号频率的对应关系进行比较，以选择对应的PWM信号频率给所述驱动电路以驱动所述电机。
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