Control devices and methods

This application claims the benefit of Taiwan application Serial No. 97103677 filed Jan. 31, 2008, the subject matter of which is incorporated herein by reference.

1. Field of the Invention

The invention relates to a control device and method, and more particularly to a control device and method for a motor.

2. Description of the Related Art

For conventional control methods for brushless motors, a pulse width modulation (PWM) signal is used to control a driving circuit which further provides current to a stator of a motor, so that polarities are generated in the stator. The motor rotates by the influence of a rotor with a permanent magnet and the stator with the polarities. When the motor rotates to a predetermined angle, the polarities of the stator are changed, and the motor continuously rotates. By providing the PWM signal to the driving circuit and continuously changing the polarities of the stator, the motor can unceasingly rotate. However, because a PWM is continuously provided to the driving circuit, power consumption of the driving circuit is increased. Additionally, when the polarities of the stator are changed, surge current is generated due to the switch operation of the driving circuit, degrading efficiency of the driving circuit.

It is desired to provide a control device and method for a motor, which can improve efficiency and save power of a driving circuit by controlling the switching of a PWM signal.

Control devices are provided. An exemplary embodiment of a control device is used for driving a motor which comprises a rotor and a stator. The control device comprises a Hall detector and driving circuit. The Hall detector detects magnetic flux variation when the rotor rotates and generates a first detection signal and a second detection signal. The first and second detection signals represent current rotation location when the rotor rotates. The driving circuit generates a driving signal to drive the stator. The driving circuit turns on or off the driving signal according to a control signal and the relationship between the first and second detection signals.

Control methods are provided. An exemplary embodiment of a control method used for driving a motor is provided, which comprises a rotor and a stator. The control method comprises: providing a driving signal; turning on the driving signal to drive the stator when a first terminal of the rotor is at a base point; and turning off the driving signal when the first terminal of the rotor is at a first specific point by moving from the base point. In some embodiments, the control method further comprises: turning on the driving signal when the first terminal of the rotor is at a divided point; and turning off the driving signal when the first terminal of the rotor is at a second specific point by moving from the divided point.

A detailed description is given in the following embodiments with reference to the accompanying drawings.

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1 shows an exemplary embodiment of a control device;

FIG. 2 depicts an exemplary embodiment of the driving circuit;

FIG. 3 shows a difference signal H+-H− between the first detection signal H+ and the second detection signal H− and the determination signal S 20 ;

FIG. 4 shows the determination signal S 20 , the clock signal CLK 2 , and the switch signal SSW; and

FIGS. 5 a - 5 d show the rotation states of the rotor of the motor 20 .

The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.

Control devices and methods are provided. In an exemplary embodiment of a control device shown in FIG. 1 , a control device 11 is used to drive a motor 10 and comprises a Hall detector 110 and a driving circuit 111 . One of ordinary skill in the art should know that a motor comprises a rotor and a stator. The Hall detector 110 detects magnetic flux variation when the rotor of the motor 10 rotates and generates a first detection signal H+ and a second detection signal H− according to the detected magnetic flux variation. The first detection signal H+ and the second detection signal H− are differential signals and represent a rotation angle range of the rotator. For example, according to a base point, the rotation angle of the rotator is between 0 and 180 degrees or between 180 and 360 degrees. The driving circuit 111 receives the first detection signal H+ and the second detection signal H− and a control signal CS and generates a driving signal S 11 to drive the motor 10 . The driving circuit 111 turns on or off the driving signal S 11 according the control signal CS and the relationship between the first detection signal H+ and the second detection signal H−. The detailed operation of turning on and off the driving signal S 11 by the control device 11 is described in following.

FIG. 2 depicts an exemplary embodiment of the driving circuit. Referring to FIG. 2 , the driving circuit 111 comprises a comparing unit 20 , a counting unit 21 , a register unit 22 , first and second programmable counting units 23 and 24 , and a driving unit 25 . The comparing unit 20 receives and compares the first and second detection signals H+ and H−. The comparing unit 20 generates a determination signal S 20 according to the compared result. FIG. 3 shows a difference signal H+-H− between the first detection signal H+ and the second detection signal H− and the determination signal S 20 . A base point is defined. Referring to FIG. 3 , when the rotation angle of the rotator is between 0 and 180 degrees, the first detection signal H+ is larger than the second detection signal H−. A difference signal H+-H− which is obtained by subtracting the second detection signal H− from the first detection signal H+ is positive, and the determination signal S 20 has a high level. When the rotation angle of the rotator is between 180 and 360 degrees, the first detection signal H+ is less than the second detection signal H−. The difference signal H+ -H− is negative, and the determination signal S 20 has a low level.

The counting unit 21 receives a clock signal CLK 1 and the determination signal S 20 and is reset (RESET) according to the transition of the determination signal S 20 , that is according to the rising or falling edge of the determination signal S 20 . The counting unit 21 counts by the clock signal CLK 1 and performs a division operation to the counted result and a coefficient to generate a counting signal S 21 . In other words, the counting unit 21 calculates required time periods when the rotation angle of the rotator is between 0 and 180 degrees and between 180 and 360 degrees, and then the duty cycle of the determination signal S 20 is obtained. In this embodiment, after obtaining the counting signal S 21 , the counting unit 21 is reset (RESET) according to the transition of the determination signal S 20 , delayed by one work clock.

When the determination signal S 20 is transited (that is when the rising or falling edge of the determination signal S 20 appears), the register unit 22 latches and stores the counting signal S 21 . The first programmable counting unit 23 receives a stored counting signal S 22 from the register unit 22 and counts by the clock signal CLK 1 to generate a clocks signal CLK 2 . The period of the clock signal CLK 2 is equal to S 22 *T CLK1 , wherein T CLK1 represents the period of the clock signal CLK 1 . The first programmable counting unit 23 is reset (RESET) according to the transition of the determination signal S 20 or the clock signal CLK 2 . The second programmable counting unit 24 receives the control signal CS and counts the control signal CS by the clock signal CLK 2 to generate a switch signal SSW. The second programmable counting unit 24 is reset according to the transition of the detection signal S 29 . The switch signal SSW is at a low level when the second programmable counting unit 24 is reset and then changes to at a high level when over-flow occurs in the second programmable counting unit 24 . The driving unit 25 triggers a pulse width modulation signal PWM to generate the driving signal S 11 according to the switch signal SSW. When the switch signal SSW is at a low level, the PWM signal is provided to the driving unit 25 ; and when the switch signal SSW is at a high level, the PWM signal is not provided to the driving unit 25 .

In some embodiments, there is a power element (not shown in FIG. 2 ) between the motor 10 and the driving circuit 11 . The power element generates driving current to the motor 10 according to the driving signal S 11 , thereby controlling the polarities of the stator of the motor 10 . In other embodiments, the power element is implemented by a power MOS transistor.

FIG. 4 shows the determination signal S 20 , the clock signal CLK 2 , and the switch signal SSW. Referring to FIG. 4 , it is assumed that the counting unit 21 counts the determination signal S 20 according to the clock signal CLK 1 to obtain whether the high or low level of the determination signal S 20 has 1000 clock signal CLK 1 , that is the counted result is equal to 1000. The counting unit 21 divides the counted result by a coefficient N to obtain the counting signal S 21 . In this embodiment, the coefficient N is set as 10, thus the value represented by the counting signal S 21 is 100 (1000/10=100). The counting signal S 21 is temporarily stored in the register unit 22 and then output to serve as the counting signal S 22 . The first programmable counting unit 23 receives the counting signal S 22 stored in the register unit 22 and counts the counting signal S 22 by the clock signal CLK 1 . When the first programmable counting unit 23 counts to 100, the first programmable counting unit 23 outputs a signal with a high level to serve as the clock signal CLK 2 . Before the determination signal S 20 is transited again, the first programmable counting unit 23 is reset according to the feedback clock signal CLK 2 for starting a new count. In other words, the first programmable counting unit 23 starts a new count when over-flow occurs in the clock signal CLK 2 or the first programmable counting unit 23 counts to over 100. The second programmable counting unit 24 counts the control signal CS by the clock signal CLK 2 . The value represented by the control signal CS is between 0 and N−1, in this embodiment, it is assumed that the value represented by the control signal CS is 6. The second programmable counting unit 24 generates the switch signal SSW with a low level in the beginning. When the second programmable counting unit 24 counts to over 6, the switch signal SSW is changed to a high level. The driving unit 25 receives the switch signal SSW and triggers the PWM signal to generate the driving signal S 11 according to the switch signal SSW. The driving unit 25 generates the driving signal S 11 according to the switch signal SSW with the low level (“ON” state) and stops generating the driving signal S 11 according to the switch signal SSW with the high level (“OFF” state). Wherein, when the driving unit 25 strops generating the driving signal S 11 is determined by the control signal CS, and the control signal CS is determined according to system requirements.

FIGS. 5 a - 5 d show the rotation states of the rotor of the motor 20 . The operation of turning on and off the driving signal S 11 is described by using the rotation angle of a rotator 50 of the motor 10 . The rotation order of the rotor is from FIG. 5 a to FIG. 5 d . A base point is defined as 0 degrees, and a divided point is defined as 180 degrees. The rotator 50 is a permanent magnet and has a positive terminal (P) and a negative terminal (N). During the positive terminal (P) of the rotator 50 moves from the base point to the divided point, that is when the rotation angle of a rotator 50 is between 0 to 180 degrees, the first detection signal H+ is larger than the second detection signal H−, and the determination signal S 20 has a high level. Moreover, the stator of the motor 10 generates a positive polarity (P) at the base point and a negative polarity (N) at the divided point. When the determination signal S 20 is at the high level, by the above operations of the counting unit 21 , the register unit 22 , and the first and second programmable counting unit 23 and 24 , the second programmable counting unit 24 generates the switch signal SSW according to the control signal CS. When the positive terminal (P) of the rotator 50 is at the base point, the driving unit 25 generates the driving signal S 11 according to the switch signal SSW with a low level. When the positive terminal (P) of the rotator 50 moves to a specific point SP 1 , the driving unit 25 stops generating the driving signal S 1 according to the switch signal SSW with a high level. In this embodiment, when the positive terminal (P) of the rotator 50 moves from the base point to the specific point SP 1 , the rotator 50 rotates about 120-135 degrees. In some embodiments, the specific point SP 1 can be in a range between 90 and 180 degrees according to different applications. The specific point SP 1 between 120 and 135 degrees in this embodiment is given as an example, without limitation. When the driving unit 25 stops generating the driving signal S 11 , the rotator 50 can rotate continuously by the inertia between the positive terminal (P) of the rotor 50 and the negative polarity (N) of the stator at the divided point.

When the positive terminal (P) of the rotator 50 moves from the divided point back to the base point, that is when the rotation angle of the rotator 50 is between 180 to 360 degrees, the first detection signal H+ is less than the second detection signal H−, and the determination signal S 20 has a low level. Moreover, the stator of the motor 10 generates a negative polarity (N) at the base point and a positive polarity (P) at the divided point. When the determination signal S 20 is at the low level, by the above operations of the counting unit 21 , the register unit 22 , and the first and second programmable counting unit 23 and 24 , the second programmable counting unit 24 generates the switch signal SSW according to the control signal CS. When the positive terminal (P) of the rotator 50 is at the divided point, the driving unit 25 generates the driving signal S 11 according to the switch signal SSW with the low level. When the positive terminal (P) of the rotator 50 moves to a specific point SP 2 , the driving unit 25 stops generating the driving signal S 11 according to the switch signal SSW with the high level. In this embodiment, when the positive terminal (P) of the rotator 50 moves from the base point to the specific point SP 2 , the rotator 50 rotates about 300-315 degrees. In some embodiments, the specific point SP 2 can be in a range between 270 and 360 degrees according to different applications. The specific point SP 2 between 300 and 315 degrees in this embodiment is given as an example, without limitation. When the driving unit 25 strops generating the driving signal S 11 , the rotator 50 can rotate continuously by the inertia between the positive terminal (P) of the rotor 50 and the negative polarity (N) of the stator at the base point.

According the above description, the control signal CS determines when the driving unit 25 turns off the driving signal S 11 . In other words, the control signal CS determines the positions of the specific points SP 1 and SP 2 . Thus, the timing when the driving unit 25 turns off the driving signal S 11 can be determined by adjusting the value represented by the control signal CS.

In the embodiments of the invention, the driving unit 25 turns on the driving signal S 11 first and then turns off the driving signal S 11 when the rotor of the motor 10 rotates by a predetermined angle. The rotor rotates continuously by the rotation inertia. When the rotation inertia disappears, the driving unit 25 turns on the driving signal S 11 again. Thus, the driving unit 25 does not provide a continuous driving signal S 11 , and saves power. Moreover, the PWM signal is turned off before the polarities of the stator are changed, reducing current surge generated during switch operation of a driving circuit, thus improving efficiency of the driving circuit.

While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.