Motor controller

Abstract

The present invention discloses a motor controller comprising a switching circuit and a control unit. The switching circuit is coupled to a motor to drive the motor. The control unit is configured to generate a control signal to control the switching circuit. The motor controller is configured to generate a current signal and a voltage signal. When a current phase of the current signal is at a predetermined crossover phase, the motor controller calculates a difference between the current phase of the current signal and a voltage phase of the voltage signal, wherein the motor controller is configured to control the difference. The motor controller can adjust the difference to stabilize the motor and prevent noise. The motor controller can adjust the difference so that the difference equals a predetermined phase difference.

Description

Technical Field

[0001] The present invention relates to a motor controller, and more particularly to a motor controller applicable to a sensorless three-phase motor. Background Art

[0002] Traditionally, motor drive methods can be categorized into two types. One uses Hall effect sensors to switch phases and drive the motor. The other drives the motor without Hall effect sensors. Because Hall effect sensors are easily affected by the external environment, resulting in reduced sensing accuracy, and the inclusion of Hall effect sensors increases system size and cost, sensorless drive methods have been proposed to address these issues.

[0003] In sensorless drive methods, a motor controller compares the voltage of a floating phase with a reference voltage to detect the back electromotive force (BEMF) of the floating phase and switches phases. However, when the motor controller turns on the floating phase to detect the switching point, it causes discontinuities in the output voltage, generating noise.

[0004] Another existing technique uses the equation: V = i × Rm + L × di / dt + BEMF to estimate back EMF, where Rm is the motor resistance and L is the coil inductance. However, this existing technique requires a complex calculation circuit to estimate back EMF. Therefore, a new technique is needed that can drive a motor with a simple calculation circuit while avoiding noise. Summary of the Invention

[0005] In view of the aforementioned problems, an object of the present invention is to provide a motor controller that can utilize a simple computing circuit to drive a motor and avoid noise.

[0006] According to the present invention, a motor controller is provided. The motor controller is used to drive the motor, wherein the motor can be a three-phase motor. The motor controller has a switching circuit, a control unit, a current detection unit, a waveform processing unit, and a phase difference processing unit. The switching circuit can have a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a first terminal, a second terminal, and a third terminal, wherein the switching circuit is coupled to the motor to drive the motor. The first terminal has a current signal Iu and a voltage signal Vu to drive the motor. The first transistor, the third transistor, and the fifth transistor are each an upper switch. The second transistor, the fourth transistor, and the sixth transistor are each a lower switch. The control unit generates a control signal to control the switching circuit.

[0007] The current detection unit is coupled to the switch circuit and the control unit to detect a current phase. The current detection unit is coupled to the first terminal, the second terminal, and the third terminal. The current detection unit has a first comparator, a second comparator, a multiplexer, a first switch, a second switch, a third switch, and a resistor. The current detection unit can have three detection methods. For example, the first detection method can detect the current signal Iu to obtain the current phase. The designer can also obtain the current phase by detecting the current flowing from the second terminal to the motor or the current flowing from the third terminal to the motor. The second detection method can detect the current flowing through the resistor to obtain the current phase. The first switch is coupled to the first terminal, the first comparator, and the second comparator. The first comparator is coupled to a terminal of the first transistor and the first switch to detect the voltage difference between the source and drain of the first transistor to obtain the current phase. The second comparator is coupled to a terminal of the second transistor and the first switch to detect a voltage difference between the source and drain of the second transistor to obtain the current phase. The second switch is coupled to the second terminal, the first comparator, and the second comparator. The first comparator is coupled to a terminal of the third transistor and the second switch to detect a voltage difference between the source and drain of the third transistor to obtain the current phase. The second comparator is coupled to a terminal of the fourth transistor and the second switch to detect a voltage difference between the source and drain of the fourth transistor to obtain the current phase. The third switch is coupled to the third terminal, the first comparator, and the second comparator. The first comparator is coupled to a terminal of the fifth transistor and the third switch to detect a voltage difference between the source and drain of the fifth transistor to obtain the current phase. The second comparator is coupled to a terminal of the sixth transistor and the third switch to detect a voltage difference between the source and drain of the sixth transistor to obtain the current phase. The multiplexer is coupled to an output terminal of the first comparator and an output terminal of the second comparator to generate a detection signal. The multiplexer can output phase information of the upper switch or the lower switch according to a selection signal to implement a third detection method. In addition, the current detection unit is coupled to the switching circuit to generate a phase signal to the phase difference processing unit, where the phase signal represents a current phase.

[0008] The waveform processing unit can operate the motor controller in a trapezoidal wave drive mode or a sine wave drive mode. The waveform processing unit can determine whether the motor controller is in the trapezoidal wave drive mode or the sine wave drive mode based on rotational speed information. Furthermore, the waveform processing unit generates a pulse width modulation signal to the control unit, wherein the pulse width modulation signal has a duty cycle. The motor controller can adjust the motor speed based on the duty cycle.

[0009] The current signal Iu and the voltage signal Vu can each be a sinusoidal signal. When the current phase of the current signal Iu is at a predetermined crossover phase, the motor controller calculates a difference D between the current phase of the current signal Iu and the voltage phase of the voltage signal Vu, wherein the motor controller is configured to control the difference D. Specifically, the motor controller can stabilize the motor and avoid noise by modulating the difference D. For example, when the difference D is greater than a predetermined phase difference, the motor controller gradually decreases the difference D so that the difference D equals the predetermined phase difference. When the difference D is less than the predetermined phase difference, the motor controller gradually increases the difference D so that the difference D equals the predetermined phase difference. When the difference D equals the predetermined phase difference, the motor is in a stable state. The difference D can be controlled by a phase-locked loop controller, a digital phase-locked loop controller, a proportional-integral controller, a proportional-differential controller, or a proportional-integral-differential controller. For example, the motor controller can use the current phase of the current signal Iu to modulate the voltage phase of the voltage signal Vu. The motor controller can adjust the electrical period of the voltage signal Vu to modulate the difference D. When the difference D is greater than the predetermined phase difference, the motor controller decreases the electrical period of the voltage signal Vu. When the difference D is less than the predetermined phase difference, the motor controller increases the electrical period of the voltage signal Vu. Therefore, the motor controller can determine when to switch phases by modulating the electrical period of the voltage signal Vu. In other words, the motor controller can achieve a commutation function without detecting a commutation point.

[0010] According to one embodiment of the present invention, the motor controller can execute steps S41-S44 of a flowchart to smoothly operate the motor. First, the motor controller detects the current phase of the current signal Iu (step S41). Next, the motor controller checks whether the current phase of the current signal Iu is at a predetermined crossover phase (step S42). The predetermined crossover phase can be 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, or 300 degrees. The designer can decide to select 6 predetermined crossover phases, 3 predetermined crossover phases, 2 predetermined crossover phases, or 1 predetermined crossover phase based on the required bandwidth. In other words, the motor controller can use multiple predetermined crossover phases to drive the motor. For example, when the designer selects 6 predetermined crossover phases, the bandwidth is maximized, and the motor controller can quickly stabilize the motor. When the designer selects only 1 predetermined crossover phase, the bandwidth is minimized, and the motor controller takes a longer time to stabilize the motor. When the current phase of the current signal Iu is at the predetermined crossover phase, the motor controller calculates the difference D between the current phase of the current signal Iu and the voltage phase of the voltage signal Vu (step S43). When the current phase of the current signal Iu is not at the predetermined crossover phase, the motor controller continues to detect the current phase of the current signal Iu (step S41). The phase difference processing unit can be used to calculate the difference D between the current phase of the current signal Iu and the voltage phase of the voltage signal Vu. The motor controller then makes the difference D equal to a predetermined phase difference (step S44). Finally, the motor controller continues to detect the current phase of the current signal Iu (step S41). The phase difference processing unit can be used to adjust the difference D so that the difference D is equal to the predetermined phase difference. The phase difference processing unit receives the phase signal and generates a time signal to the waveform processing unit, wherein the time signal can represent an electrical cycle time. Based on the information in the time signal, the waveform processing unit can adjust the electrical cycle of the voltage signal Vu to know when to switch phases. Therefore, the motor controller does not need to open a floating phase to detect a commutation point, thereby avoiding noise. In addition, the motor controller can utilize a simple calculation circuit to drive the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 FIG. 1 is a schematic diagram of a motor controller according to an embodiment of the present invention.

[0012] Figure 2 FIG. 1 is a schematic diagram of a switch circuit and a current detection unit according to an embodiment of the present invention.

[0013] Figure 3 FIG. 1 is a timing diagram of an embodiment of the present invention.

[0014] Figure 4 FIG. 1 is a flow chart of an embodiment of the present invention.

[0015] Explanation of the accompanying symbols: 10-motor controller; 100-switch circuit; 110-control unit; 120-current detection unit; 130-waveform processing unit; 140-phase difference processing unit; Vc-control signal; Vpu-pulse width modulation signal; Vt-time signal; Vph-phase signal; U-first terminal; V-second terminal; W-third terminal; VCC-fourth terminal; GND-fifth terminal; 101-first transistor; 102-second transistor; 103-third transistor; 104-fourth transistor; 105-fifth transistor; 106-sixth transistor; 121-first comparator; 122-second comparator; 123-multiplexer; S1-first switch; S2-second switch; S3-third switch; R-resistor; M-motor; Vs-selection signal; Vd-detection signal; Iu-current signal; Vu-voltage signal; D-difference; S41, S42, S43, S44-steps. DETAILED DESCRIPTION

[0016] The following description will make the purpose, features and advantages of the present invention more apparent.Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0017] Figure 1 Figure 1 is a schematic diagram of a motor controller 10 according to an embodiment of the present invention. The motor controller 10 is used to drive a motor M, which may be a three-phase motor. The motor controller 10 includes a switching circuit 100, a control unit 110, a current detection unit 120, a waveform processing unit 130, and a phase difference processing unit 140. Figure 2 FIG. 1 is a schematic diagram of a switch circuit 100 and a current detection unit 120 according to an embodiment of the present invention. Figure 2As shown, the switching circuit 100 may include a first transistor 101, a second transistor 102, a third transistor 103, a fourth transistor 104, a fifth transistor 105, a sixth transistor 106, a first terminal U, a second terminal V, and a third terminal W. The switching circuit 100 is coupled to a motor M to drive the motor M. The first terminal U has a current signal Iu and a voltage signal Vu to drive the motor M. The first transistor 101 is coupled to a fourth terminal VCC and the first terminal U, while the second transistor 102 is coupled to the first terminal U and a resistor R. The third transistor 103 is coupled to the fourth terminal VCC and the second terminal V, while the fourth transistor 104 is coupled to the second terminal V and the resistor R. The fifth transistor 105 is coupled to the fourth terminal VCC and the third terminal W, while the sixth transistor 106 is coupled to the third terminal W and the resistor R. One terminal of the resistor R is coupled to the second transistor 102, the fourth transistor 104, and the sixth transistor 106. The other terminal of the resistor R is coupled to a fifth terminal GND. The first transistor 101, the third transistor 103, and the fifth transistor 105 can each be a P-type metal oxide semiconductor transistor. The second transistor 102, the fourth transistor 104, and the sixth transistor 106 can each be an N-type metal oxide semiconductor transistor. Furthermore, the first transistor 101, the third transistor 103, and the fifth transistor 105 are each a top-side switch. The second transistor 102, the fourth transistor 104, and the sixth transistor 106 are each a bottom-side switch. The control unit 110 generates a control signal Vc to control the switch circuit 100. In other words, the control unit 110 can be used to control the conduction status of the first transistor 101, the second transistor 102, the third transistor 103, the fourth transistor 104, the fifth transistor 105, and the sixth transistor 106, respectively.

[0018] The current detection unit 120 is coupled to the switch circuit 100 and the control unit 110 to detect a current phase. Figure 1 or Figure 2As shown, the current detection unit 120 is coupled to a first terminal U, a second terminal V, and a third terminal W. The current detection unit 120 includes a first comparator 121, a second comparator 122, a multiplexer 123, a first switch S1, a second switch S2, a third switch S3, and a resistor R. The current detection unit 120 can have three detection methods. For example, the first detection method can detect the current signal Iu to obtain the current phase. Designers can also obtain the current phase by detecting the current flowing from the second terminal V to the motor M or the current flowing from the third terminal W to the motor M. The second detection method can detect the current flowing through the resistor R to obtain the current phase. The first switch S1 is coupled to the first terminal U, the first comparator 121, and the second comparator 122. The first comparator 121 is coupled to a terminal of the first transistor 101 and the first switch S1 to detect the voltage difference between the source and drain of the first transistor 101 to obtain the current phase. The second comparator 122 is coupled to a terminal of the second transistor 102 and the first switch S1 to detect the voltage difference between the source and drain of the second transistor 102 to obtain the current phase. The second switch S2 is coupled to the second terminal V, the first comparator 121, and the second comparator 122. The first comparator 121 is coupled to a terminal of the third transistor 103 and the second switch S2 to detect the voltage difference between the source and drain of the third transistor 103 to obtain the current phase. The second comparator 122 is coupled to a terminal of the fourth transistor 104 and the second switch S2 to detect the voltage difference between the source and drain of the fourth transistor 104 to obtain the current phase. The third switch S3 is coupled to the third terminal W, the first comparator 121, and the second comparator 122. The first comparator 121 is coupled to a terminal of the fifth transistor 105 and the third switch S3 to detect the voltage difference between the source and drain of the fifth transistor 105 to obtain the current phase. The second comparator 122 is coupled to an end of the sixth transistor 106 and the third switch S3 to detect the voltage difference between the source and drain of the sixth transistor 106 to obtain the current phase. The multiplexer 123 is coupled to an output end of the first comparator 121 and an output end of the second comparator 122 to generate a detection signal Vd. The multiplexer 123 can output phase information of the upper switch or the lower switch based on a selection signal Vs to implement a third detection method. Designers can implement three detection methods, two of the three detection methods, or one of the three detection methods based on actual needs. In addition, the current detection unit 120 is coupled to the switching circuit 100 to generate a phase signal Vph to the phase difference processing unit 140, where the phase signal Vph represents a current phase.

[0019] The waveform processing unit 130 can operate the motor controller 10 in either a trapezoidal wave drive mode or a sine wave drive mode. The waveform processing unit 130 can determine whether the motor controller 10 is in the trapezoidal wave drive mode or the sine wave drive mode based on speed information. Furthermore, the waveform processing unit 130 generates a pulse-width modulation signal Vpu to the control unit 110. The pulse-width modulation signal Vpu has a duty cycle. The motor controller 10 can adjust the speed of the motor M based on the duty cycle.

[0020] Figure 3This is a timing diagram of an embodiment of the present invention, in which the current signal Iu and the voltage signal Vu are each a sinusoidal signal. When the current phase of the current signal Iu is at a predetermined crossover phase, the motor controller 10 calculates the difference D between the current phase of the current signal Iu and the voltage phase of the voltage signal Vu, wherein the motor controller 10 is configured to control the difference D. Specifically, the motor controller 10 can stabilize the motor M and prevent noise by adjusting the difference D. For example, when the difference D is greater than a predetermined phase difference, the motor controller 10 gradually decreases the difference D until the difference D equals the predetermined phase difference. When the difference D is less than the predetermined phase difference, the motor controller 10 gradually increases the difference D until the difference D equals the predetermined phase difference. When the difference D equals the predetermined phase difference, the motor M is in a stable state. The difference D can be controlled by a phase-locked loop (PLL) controller, a digital phase-locked loop (DPLL) controller, a proportional-integral controller, a proportional-derivative controller, or a proportional-integral-derivative controller. Designers can use any of these controllers to adjust the difference D. For example, the motor controller 10 can use the current phase of the current signal Iu to modulate the voltage phase of the voltage signal Vu. The motor controller 10 can adjust the difference D by adjusting the electrical period of the voltage signal Vu. Designers can also adjust other parameters to adjust the difference D. When the difference D is greater than a predetermined phase difference, the motor controller 10 decreases the electrical period of the voltage signal Vu. When the difference D is less than the predetermined phase difference, the motor controller 10 increases the electrical period of the voltage signal Vu. Therefore, the motor controller 10 can determine when to switch phases by modulating the electrical period of the voltage signal Vu. That is to say, the motor controller 10 can achieve a phase switching function without detecting the phase switching point. In addition, the predetermined phase difference is related to the rotational speed of the motor. Generally speaking, the greater the rotational speed of the motor, the smaller the predetermined phase difference. The motor controller 10 can use a look-up table to store the relationship between the predetermined phase difference and the rotational speed of the motor. In summary, the motor controller 10 does not need to turn on the floating phase, thereby avoiding noise. In other words, the motor controller 10 does not need to detect a back electromotive force and the voltage signal Vu may be independent of the back electromotive force, so the technology of the present invention may be independent of the back electromotive force. The motor controller 10 can use a simple operation circuit to drive the motor M.

[0021] Figure 4This is a flowchart of an embodiment of the present invention. First, the motor controller 10 detects the current phase of the current signal Iu (step S41). Then, the motor controller 10 checks whether the current phase of the current signal Iu is in a predetermined crossover phase (step S42). The predetermined crossover phase may be 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, or 300 degrees. The designer may decide to select 6 predetermined crossover phases, 3 predetermined crossover phases, 2 predetermined crossover phases, or 1 predetermined crossover phase based on the required bandwidth. In other words, the motor controller 10 may utilize multiple predetermined crossover phases to drive the motor M. For example, when the designer selects 6 predetermined crossover phases, the bandwidth is maximized and thus the motor controller 10 can quickly stabilize the motor M. When the designer selects only 1 predetermined crossover phase, the bandwidth is minimized and thus the motor controller 10 requires a longer time to stabilize the motor M. When the current phase of the current signal Iu is at a predetermined crossover phase, the motor controller 10 calculates the difference D between the current phase of the current signal Iu and the voltage phase of the voltage signal Vu (step S43). When the current phase of the current signal Iu is not at the predetermined crossover phase, the motor controller 10 continues to detect the current phase of the current signal Iu (step S41). The phase difference processing unit 140 can be used to calculate the difference D between the current phase of the current signal Iu and the voltage phase of the voltage signal Vu. The motor controller 10 then sets the difference D to a predetermined phase difference (step S44). Finally, the motor controller 10 continues to detect the current phase of the current signal Iu (step S41). The phase difference processing unit 140 can be used to adjust the difference D so that the difference D is equal to the predetermined phase difference. In other words, the phase difference processing unit 140 can include a phase-locked loop controller, a digital phase-locked loop controller, a proportional-integral controller, a proportional-derivative controller, or a proportional-integral-derivative controller to control the difference D. Furthermore, the phase difference processing unit 140 can also include a lookup table to store the relationship between the predetermined phase difference and the motor speed. The phase difference processing unit 140 receives the phase signal Vph and generates a time signal Vt for the waveform processing unit 130. The time signal Vt represents an electrical cycle. Using the information in the time signal Vt, the waveform processing unit 130 can adjust the electrical cycle of the voltage signal Vu to determine when to switch phases. Specifically, when the speed of the motor M changes, the motor controller 10 re-executes steps S41-S44 of the flowchart to ensure smooth operation of the motor M.

[0022] According to one embodiment of the present invention, the motor controller 10 can be applied to a sensorless motor. Furthermore, the motor controller 10 can also be applied to a single-phase motor, a polyphase motor, a brushless motor, or a DC motor. In summary, when the current phase of the current signal Iu is at a predetermined crossover phase, the motor controller 10 calculates the difference D between the current phase of the current signal Iu and the voltage phase of the voltage signal Vu. The motor controller 10 modulates the difference D so that the difference D equals a predetermined phase difference. The motor controller 10 can achieve a commutation function without turning on a floating phase. The motor controller 10 can achieve a commutation function without detecting a back electromotive force. Therefore, the motor controller 10 can utilize a simple computational circuit to drive the motor M and avoid noise.

[0023] While the present invention has been described with reference to preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments. On the contrary, the invention is intended to cover various modifications and similar arrangements that are apparent to those skilled in the art. Therefore, the present invention should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

[0024] The above descriptions are merely preferred embodiments of the present invention. All equivalent changes and modifications made within the scope of the present invention should fall within the scope of the present invention.

Claims

1. A motor controller, characterized in that: Include: a switching circuit coupled to a motor for driving the motor; and a control unit configured to generate a control signal to control the switching circuit, wherein the motor controller is configured to generate a current signal and a voltage signal. When a current phase of the current signal is at a predetermined crossover phase, the motor controller calculates a difference between the current phase of the current signal and a voltage phase of the voltage signal, and controls the difference. The motor controller modulates the difference so that the difference equals a predetermined phase difference, wherein the predetermined phase difference is related to a rotational speed of the motor, and the predetermined phase difference decreases as the rotational speed of the motor increases. The motor controller does not need to start a floating phase to achieve a phase switching function, and the motor controller does not need to detect a back electromotive force to achieve a phase switching function.

2. The motor controller according to claim 1, wherein: The difference is controlled by a phase-locked loop controller.

3. The motor controller according to claim 1, wherein: The motor controller modulates the difference by adjusting an electrical cycle of the voltage signal.

4. The motor controller according to claim 3, wherein: When the difference is greater than a predetermined phase difference, the motor controller reduces the electrical period of the voltage signal.

5. The motor controller according to claim 3, wherein: When the difference is less than a predetermined phase difference, the motor controller increases the electrical cycle of the voltage signal.

6. The motor controller according to claim 1, wherein: The predetermined crossover phase is 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, or 300 degrees.

7. The motor controller according to claim 1, wherein: The motor controller stabilizes the motor by adjusting the difference.

8. The motor controller according to claim 1, wherein: The motor controller adjusts the difference to avoid noise.

9. The motor controller according to claim 1, wherein: The motor controller further includes a current detection unit. The current detection unit includes a resistor coupled to the switch circuit.

10. The motor controller according to claim 1, wherein: The motor controller further includes a current detection unit. The current detection unit includes a first switch coupled to the switch circuit.

11. The motor controller according to claim 10, wherein: The current detection unit further includes a first comparator coupled to the first switch.

12. The motor controller according to claim 10, wherein: The current detection unit further includes a second switch coupled to the switch circuit.

13. The motor controller according to claim 1, wherein: The motor controller also includes: a phase difference processing unit; and A current detection unit is coupled to the switch circuit and is used to generate a phase signal to the phase difference processing unit.

14. The motor controller according to claim 13, wherein: The phase difference processing unit includes a phase-locked loop controller to control the difference.

15. The motor controller according to claim 13, wherein: The motor controller further includes a waveform processing unit. The phase difference processing unit receives the phase signal and generates a time signal to the waveform processing unit.

16. The motor controller according to claim 15, wherein: The waveform processing unit enables the motor controller to be in a trapezoidal wave driving mode or a sine wave driving mode.

17. The motor controller according to claim 16, wherein: The waveform processing unit determines whether the motor controller is in the trapezoidal wave driving mode or the sine wave driving mode according to rotation speed information.

18. The motor controller according to claim 15, wherein: The waveform processing unit generates a pulse width modulation signal to the control unit. The pulse width modulation signal has a duty cycle. The motor controller adjusts a rotation speed of the motor according to the duty cycle.

19. The motor controller according to claim 1, wherein: This voltage signal is independent of a back electromotive force.

20. The motor controller according to claim 1, wherein The motor controller utilizes a plurality of predetermined crossover phases to drive the motor.

21. The motor controller according to claim 1, wherein The motor controller is applied to a sensorless motor.

22. The motor controller according to claim 1, wherein: The motor controller is applied to a single-phase motor, a multi-phase motor, a brushless motor or a DC motor.

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