TWI463787B - Brushless dc motor control device and method - Google Patents

Description

Brushless DC motor control device and method

The present invention relates to a motor control device and method, and more particularly to a brushless DC motor control device and method, which is in a digitally modulated manner, by a time difference or magnetic field of a magnetic field generated during a change of a magnetic field of a motor. The drop time difference is divided into multiple time divisions, each of which has its corresponding duty cycle, and then drives the brushless DC motor to make the motor commutation current linearly smooth, thereby reducing the vibration generated by the brushless DC motor and The problem of noise is to enable the brushless DC motor control apparatus and method of the present invention to achieve good output performance and better system stability.

Due to the continuous advancement of technology, electronic products are becoming more and more popular. In these electronic products, such as communication devices, notebook computers and home appliances, etc., small-sized and high-efficiency brushless DC motors are widely used, which are commonly used in computer CPUs. CD player and hard disk, etc.

Generally speaking, when driving the brushless DC motor to rotate, it is necessary to detect the position of the rotor and perform phase conversion through the switching of the commutation switch; however, when the motor is driven, the current is unstable due to the switching process, causing the motor to resonate. This can cause disturbing noise, which in turn affects the comfort of use.

Therefore, the present invention provides a brushless DC motor control apparatus and method for dividing a time difference of a magnetic field rise time or a time difference of a magnetic field drop generated during a change of a magnetic field of a motor into a plurality of time divisions in a digitally modulated manner, each time being equally divided. It has its corresponding working cycle, which in turn drives the brushless DC motor to rotate, so that the motor commutation current is linear and smooth, which can reduce the vibration and noise generated by the brushless DC motor.

In order to solve the above problems concerning the vibration and noise generated by the motor, one main object of the present invention is to provide a brushless DC motor control device that transmits a PWM duty cycle modulation circuit in a digitally modulated manner to drive a motor in current phase conversion. The current curve is controlled to make it linearly smooth, thereby reducing the vibration and noise of the brushless DC motor and achieving better system stability.

Another main object of the present invention is to provide a brushless DC motor control method, which can linearly smooth the output current curve and achieve better system stability by the brushless DC motor control method.

According to the above items, the present invention provides a device for connecting to a brushless DC motor, comprising: a magnetic field detecting circuit for detecting a rotor position of a brushless DC motor; a Hall element, coupling The magnetic field detecting circuit is configured to sense a magnetic pole change of the rotor position and correspondingly generate a magnetic field change curve, wherein the magnetic field change curve includes a maximum magnetic flux density (B _max ) and a positive hysteresis magnetic flux density (B _H+ ). a zero magnetic flux density (B ₀ ), a negative hysteresis magnetic flux density (B _H- ), and a minimum magnetic flux density (B _min ); a counter having a rise time counter and a fall time counter, and a magnetic field Detecting a circuit connection, calculating a magnetic field rise time difference or a magnetic field fall time difference generated by the brushless DC motor via the magnetic field detecting circuit according to the magnetic field change curve, wherein the magnetic field rise time difference is from the minimum magnetic flux density (B _min ) to the during the maximum magnetic flux density (B _max), the calculated field at the magnetic flux density of the negative hysteresis (B _H-) hysteresis increment to the positive magnetic flux density (B _{H +)} of the interval, the rise time counter via the During the time difference from the maximum magnetic flux density lines (B _max) to the minimum magnetic flux density (B _min), the positive hysteresis is calculated magnetic flux density (B _{H +)} down to the negative hysteresis magnetic flux density through the fall time counter ( B _H- ) interval; a PWM duty cycle modulation circuit, one end of which is connected to the counter, is used to divide the time difference of the magnetic field rise time or the time difference of the magnetic field fall into N segments of time (N is an integer), each time, etc. The sub-port has its corresponding duty cycle (Duty cycle), and the other end outputs a first modulation signal (Dr_O1) and a second modulation signal (Dr_O2); and a load driving circuit, the input end receives a first a modulation signal (Dr_O1) and a second modulation signal (Dr_O2), thereby generating a first output voltage (V_O1) and a second output voltage (V_O2) and an output current ( I _load ) for driving the Brushless DC motor.

The invention provides a method comprising: providing a brushless DC motor; detecting a rotor position of a brushless DC motor, detecting a rotor position of a brushless DC motor by using a magnetic field detecting circuit, and detecting the magnetic field according to coupling Measuring a Hall element in the circuit, inducing a change in the magnetic pole position of the rotor position and correspondingly generating a magnetic field change curve, wherein the magnetic field change curve includes a maximum magnetic flux density (B _max ), a positive hysteresis magnetic flux density (B _H+ ), a zero magnetic flux density (B ₀ ), a negative hysteresis magnetic flux density (B _H- ), and a minimum magnetic flux density (B _min ); calculating a magnetic field rise time difference or a magnetic field fall time difference, using a rise time counter or a drop The time counter calculates a magnetic field rise time difference or a magnetic field fall time difference generated by the brushless DC motor via the magnetic field detecting circuit according to the magnetic field change curve, wherein the magnetic field rise time difference is from the minimum magnetic flux density (B _min ) to the maximum during the magnetic flux density (B _max), the calculated magnetic flux density of the negative hysteresis (B _H-) hysteresis increment to the positive magnetic flux density (B _{H +)} through the interval of the rise time counter The difference between the fall time and the magnetic field lines from the maximum magnetic flux density (B _max) to a minimum during which the magnetic flux density (B _min), is calculated via the fall time of the positive hysteresis counter magnetic flux density (B _{H +)} down to the negative hysteresis The interval of magnetic flux density (B _H- ); the output modulation signal is generated by using the PWM duty cycle modulation circuit to divide the magnetic field rise time difference or the magnetic field fall time difference into N segments of time (N is an integer), each segment The time division has its corresponding duty cycle (Duty cycle), and outputs a first modulation signal (Dr_O1) and a second modulation signal (Dr_O2); and driving the brushless DC motor, using a load drive The circuit receives the first modulation signal (Dr_O1) and the second modulation signal (Dr_O2), and generates a first output voltage (V_O1) and a second output voltage (V_O2) and an output current ( I _load ) for Drive the brushless DC motor.

Through the brushless DC motor control device and method provided by the present invention, the commutation current of the motor is controlled by the duty cycle generated by the PWM duty cycle modulation circuit by digital modulation, so that the output current curve can be linearly smoothed. It can reduce the vibration and noise generated by the brushless DC motor, so as to achieve better system stability and good output performance.

The present invention mainly discloses a brushless DC motor control device and method for transmitting a PWM duty cycle modulation circuit in a digitally modulated manner, and the drive motor controls the current curve to make it linearly smooth during current phase conversion. It can reduce the vibration and noise of brushless DC motor. Wherein, the brushless DC motor control device of the present invention is connected to a brushless DC motor to control the brushless DC motor; however, the basic principle and function of the brushless DC motor have been known to those skilled in the relevant art. It is to be understood that, in the following description, only the features of the brushless DC motor control apparatus and method of the present invention will be described in detail. In addition, the drawings in the following texts are not completely drawn in accordance with actual relevant dimensions, and their function is only to show a schematic diagram relating to the features of the present invention.

First, please refer to FIG. 1, which is a block diagram of a brushless DC motor control device of the present invention. As shown in FIG. 1 , the brushless DC motor control device includes: a magnetic field detecting circuit 10 for detecting a rotor position of the brushless DC motor 12; a Hall element 14 coupled to the magnetic field detecting circuit 10, The magnetic pole change is used to sense the position of the rotor and correspondingly generate a magnetic field change curve; a counter 16 is connected to the magnetic field detecting circuit 10, and the magnetic field rise of the brushless DC motor 12 generated by the magnetic field detecting circuit 10 is calculated according to the magnetic field change curve. The time difference (TR) and a magnetic field fall time difference (TF), wherein the counter 16 further includes a rise time counter 161 and a fall time counter 162, and the rise time counter 161 can be used to calculate the magnetic field rise time difference generated by the magnetic field detecting circuit (TR). Or using the fall time counter 162 to calculate the magnetic field fall time difference (TF) generated by the magnetic field detecting circuit; a PWM duty cycle modulation circuit 18, one end of which is connected to the counter 16, further including a register 181, The temporary magnetic field rise time difference (TR) or the magnetic field fall time difference (TF), and the magnetic field rise time difference (TR) or the magnetic field fall time difference (TF) is divided into N The time is equally divided (N is an integer), each time aliquot has its corresponding duty cycle (Duty cycle), and the other end of the output is a first modulation signal (Dr_O1) and a second modulation signal ( Dr_O2), wherein the PWM duty cycle modulation circuit 18 will feedback a rising signal (TR_S) to the rising time counter 161 or feedback a falling signal (TF_S) to the falling time counter 162 to notify the rising time counter 161 or the falling time counter. 162: calculating a magnetic field rise time difference (TR) or a magnetic field fall time difference (TF) generated by the magnetic field detecting circuit; and a load driving circuit 20, wherein the input end receives the first modulation signal (Dr_O1) and the second modulation signal (Dr_O2) a first output voltage (V_O1) and a second output voltage (V_O2) and an output current ( I _load ) for driving the brushless DC motor 12, wherein the brushless DC motor 12 is a single-phase brushless DC motor.

When the brushless DC motor 12 is activated, the magnetic field detecting circuit 10 continuously detects the rotor position of the brushless DC motor 12, and detects the magnetic pole of the rotor position according to a Hall element 14 coupled to the magnetic field detecting circuit 10. Changing, and generating a magnetic field change curve; then, using the counter 16 to calculate the magnetic field rise time difference (TR) and the magnetic field fall time difference (TF) during the change of the magnetic field of the brushless DC motor 12 by using the counter 16, wherein the counter 16 further includes a rise The time counter 161 and a fall time counter 162, the data calculated by the rise time counter 161 or the fall time counter 162 is transferred to the PWM duty cycle modulation circuit 18, after which the PWM duty cycle modulation circuit is based on the rise time counter. Or the magnetic field rise time difference (TR) or the magnetic field fall time difference (TF) generated by the fall time counter, temporarily store the magnetic field rise time difference (TR) or the magnetic field fall time difference (TF) in the register 181, and increase the magnetic field rise time difference ( TR) or magnetic field fall time difference (TF) is divided into N segments of time (N is the whole Number), and each time aliquot (TR/N or TF/N) has its corresponding duty cycle (Duty cycle), and the output produces a modulation signal (Dr_O1/Dr_O2), and the PWM duty cycle is modulated. The circuit also continuously feedbacks a rising signal (TR_S) or a falling signal (TF_S) to the rising time counter 161 or the falling time counter 162, and notifies the rising time counter 161 or the falling time counter 162 to calculate the magnetic field generated by the magnetic field detecting circuit. The rise time difference (TR) or the magnetic field fall time difference (TF); then, the load drive circuit 20 receives the modulation signal (Dr_O1/Dr_O2) output by the PWM duty cycle modulation circuit 18, thereby driving the brushless DC motor 12, thereby enabling The output commutating current curve is linearly smooth and reduces the vibration and noise generated by the brushless DC motor 12.

Next, please refer to FIG. 2 , which is a graph of the magnetic field variation of the present invention. As shown in FIG. 2, the magnetic field change curve is generated by detecting a magnetic pole change of the rotor position by a Hall element 14 coupled to the magnetic field detecting circuit 10, and the magnitude of the magnetic field change curve will vary with the magnetic pole position of the rotor position. Differently, it includes a maximum magnetic flux density (B _max ), a positive hysteresis magnetic flux density (B _H+ ), a zero magnetic flux density (B ₀ ), a negative hysteresis magnetic flux density (B _H- ), and a Minimum flux density (B _min ). The magnetic field rise time difference (TR1/TR2/TR3...) or the magnetic field fall time difference (TF1/TF2/TF3...) can be calculated from the magnetic field change curve, wherein the magnetic field rise time difference (TR1/TR2/TR3...) During the period from the minimum magnetic flux density (B _min ) to the maximum magnetic flux density (B _max ), the interval of the negative hysteresis magnetic flux density (B _H− ) to the positive hysteresis magnetic flux density (B _H+ ) is calculated via the rise time counter 161. And the magnetic field fall time difference (TF1/TF2/TF3...) is calculated from the maximum magnetic flux density (B _max ) to the minimum magnetic flux density (B _min ), and the positive hysteresis magnetic flux density is calculated via the fall time counter 162 (B) _H+ ) is decremented to the interval of negative hysteresis flux density (B _H- ).

Next, please refer to FIG. 3 , which is a schematic diagram of the operation of the PWM duty cycle modulation circuit of the present invention. As shown in FIG. 3, when the counter 16 calculates the magnetic field rise time difference (TR1/TR2/TR3...) or the magnetic field fall time difference (TF1/TF2/TF3...) during the change of the magnetic field of the brushless DC motor 12, The magnetic field rise time difference (TR1/TR2/TR3...) or the magnetic field fall time difference (TF1/TF2/TF3...) after the counter 16 is calculated is temporarily stored in the register 181 in the PWM duty cycle modulation circuit 18. The data temporarily stored in the temporary register 181 is delayed for one timing cycle to be read. For example, the first magnetic field rise time difference (TR1) is temporarily stored in the temporary register 181 in the PWM duty cycle modulation circuit 18. After the magnetic field phase is switched, one timing cycle is delayed, so when the counter calculates the next magnetic field rise time difference (TR2), the PWM duty cycle modulation circuit 18 starts to read the first magnetic field rise time difference (TR1). After that, the difference between the magnetic field rise time difference or the magnetic field fall time difference is divided into N segments of time (N is an integer), and each time aliquot has its corresponding duty cycle; due to magnetic field detection The Hall element 14 in the circuit 10 continuously detects the magnetic pole change of the rotor position due to The corresponding magnetic field change curve will be a continuously changing curve, so a plurality of magnetic field rise time differences or magnetic field fall time differences will be generated, and each time difference interval can be divided into N segments of time (N is an integer). Here, the first magnetic field rise time difference (TR1) read by the PWM duty cycle modulation circuit 18 is enlarged to be divided into 8 segments of time, and each time interval has its corresponding duty cycle. (duty cycle); Therefore, when the phase of the magnetic field is switched, the output modulation signal (Dr_O1/Dr_O2) is controlled according to the generated duty cycle. However, since the motor has two input terminals respectively controlling the transition of the magnetic poles of the motor coil, the output voltage can be generated by driving the load driving circuit 20 through the generated first modulation signal (Dr_O1) and the second modulation signal (Dr_O2) (V_O1/ V_O2) and the output current ( I _load ), which in turn controls the commutation current of the motor 12. When the duty cycle is gradually lowered from high to low, the motor drive current can be controlled to gradually change from zero to zero, and when the duty cycle is gradually lowered from low to low, the motor drive current can be controlled from zero. Increasingly large, thereby avoiding the noise or resonance problem caused by the abnormality of the commutation current due to the excessive or too low rotation speed of the motor 12; here, although the embodiment takes N=8 as an example, It is not limited to N using 8.

Next, please continue to refer to FIG. 4 and cooperate with FIG. 3. FIG. 4 is a diagram showing the relationship between the output voltage and the output current of the present invention. As shown in FIG. 4, the first modulation signal (Dr_O1) and the second modulation signal (Dr_O2) of the control output drive the load driving circuit 20 according to a duty cycle generated in different time difference intervals, thereby generating a An output voltage (V_O1) and a second output voltage (V_O2) and an output current ( I _load ). Observing the interval amplified by the first magnetic field rise time difference (TR1) read by the PWM duty cycle modulation circuit 18 in FIG. 3, it is known that the commutation current of the motor can be further controlled according to the change of the duty cycle. Therefore, the modulation signal (Dr_O1/Dr_O2) controlled by the duty cycle affects the changes of the first output voltage (V_O1) and the second output voltage (V_O2) and the output current (Iload). Since the change of the duty cycle is proportional to the motor speed, the modulation signal (Dr_O1/Dr_O2) is proportional to the first output voltage (V_O1) and the second output voltage (V_O2), so that the output can be made The current ( I _load ) curve is linearly smooth.

Finally, please refer to FIG. 5, which is a flow chart of the brushless DC motor control method of the present invention. As shown in FIG. 5, the brushless DC motor control method includes the following steps:

Step 500: providing a brushless DC motor;

Step 501: Detecting a rotor position of the brushless DC motor; detecting a rotor position of the brushless DC motor by using a magnetic field detecting circuit, and sensing the position of the rotor according to a Hall element coupled to the magnetic field detecting circuit The magnetic pole changes and correspondingly produces a magnetic field change curve, and then proceeds to step 502.

Step 502: Calculate a time difference of the rising time of the magnetic field or a time difference of the falling time of the magnetic field; calculate a magnetic field rise time difference or a magnetic field fall time difference generated by the brushless DC motor according to the magnetic field change curve by using a rising time counter or a falling time counter according to the magnetic field change curve, Then proceed to step 503.

Step 503: Generate an output modulation signal; use a PWM duty cycle modulation circuit to divide the magnetic field rise time difference or the magnetic field fall time difference into N segments of time (N is a whole The number of times each time has its corresponding duty cycle (Duty cycle), and outputs a first modulation signal (Dr_O1) and a second modulation signal (Dr_O2), and finally proceeds to step 504.

Step 504: Driving a brushless DC motor; receiving a first modulation signal (Dr_O1) and a second modulation signal (Dr_O2) by using a load driving circuit, and generating a first output voltage (V_O1) and a second output voltage ( V_O2) and an output current ( I _load ) for driving the brushless DC motor.

While the present invention has been described above in terms of the preferred embodiments thereof, it is not intended to limit the invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. The patent protection scope of the invention is subject to the definition of the scope of the patent application attached to the specification.

10‧‧‧Magnetic field detection circuit

12‧‧‧Brushless DC Motor

14‧‧‧ Hall element

16‧‧‧ counter

18‧‧‧PWM duty cycle modulation circuit

20‧‧‧Load drive circuit

161‧‧‧Rise time counter

162‧‧‧Drop time counter

181‧‧‧ register

500, 501, 502, 503, 504 ‧ ‧ steps

1 is a block diagram of a brushless DC motor control device of the present invention; FIG. 2 is a magnetic field change graph of the present invention; FIG. 3 is a schematic diagram of the operation of the PWM duty cycle modulation circuit of the present invention; The relationship between the output voltage and the output current of the invention; FIG. 5 is a flow chart of the control method of the brushless DC motor of the present invention.

10‧‧‧Magnetic field detection circuit

12‧‧‧Brushless DC Motor

14‧‧‧ Hall element

16‧‧‧ counter

18‧‧‧PWM duty cycle modulation circuit

20‧‧‧Load drive circuit

161‧‧‧Rise time counter

162‧‧‧Drop time counter

181‧‧‧ register

Claims (6)

A brushless DC motor control device is connected to a brushless DC motor, comprising: a magnetic field detecting circuit for detecting a rotor position of the brushless DC motor; and a Hall element coupled to the magnetic field detecting The measuring circuit is configured to sense a magnetic pole change of the rotor position and correspondingly generate a magnetic field change curve, wherein the magnetic field change curve includes a maximum magnetic flux density (B _max ), a positive hysteresis magnetic flux density (B _H+ ), and a a zero magnetic flux density (B ₀ ), a negative hysteresis magnetic flux density (B _H- ), and a minimum magnetic flux density (B _min ); a counter coupled to the magnetic field detecting circuit, having a rise time counter and a a falling time counter, wherein the magnetic field rise time difference and a magnetic field fall time difference generated by the brushless DC motor are calculated according to the magnetic field change curve, wherein the magnetic field rise time difference is from the minimum magnetic flux density (B _min ) during this magnetic flux density to a maximum (B _max), the rise time counter calculated by the retardation of the negative magnetic flux density (B _H-) hysteresis increment to the positive magnetic flux density (B _{H +)} of the section, and in this field During the time difference from the maximum magnetic flux density lines (B _max) to the minimum magnetic flux density (B _min), the positive hysteresis is calculated magnetic flux density (B _{H +)} down to the negative hysteresis magnetic flux density through the fall time counter ( a section of B _H- ); a PWM duty cycle modulation circuit, one end of which is connected to the counter, is used to divide the magnetic field rise time difference or the magnetic field fall time difference into N segments of time (N is an integer), each One time aliquot has its corresponding duty cycle, the other end outputs a first modulation signal and a second modulation signal; and a load driving circuit, the input end of which receives the first modulation signal and the The second modulation signal generates a first output voltage and a second output voltage and an output current for driving the brushless DC motor. The brushless DC motor control device according to claim 1, wherein the PWM duty cycle modulation circuit returns a rising signal or a falling signal to the counter to notify the counter to calculate the magnetic field detecting circuit. The difference in the rise time of the magnetic field or the time difference in the fall of the magnetic field. The brushless DC motor control device of claim 1, wherein the PWM duty cycle modulation circuit further comprises a register for temporarily storing the magnetic field rise time difference or the magnetic field fall time difference. A brushless DC motor control method includes: providing a brushless DC motor; detecting a rotor position of the brushless DC motor, detecting a position of the rotor of the brushless DC motor by using a magnetic field detecting circuit, and a Hall element coupled to the magnetic field detecting circuit, sensing a magnetic pole change of the rotor position and correspondingly generating a magnetic field change curve, wherein the magnetic field change curve includes a maximum magnetic flux density (B _max ) and a positive hysteresis magnetic flux Density (B _H+ ), a zero flux density (B ₀ ), a negative hysteresis flux density (B _H- ), and a minimum flux density (B _min ); calculating the time difference of the magnetic field rise or the time difference of the magnetic field drop, using a The rise time counter or a fall time counter calculates the magnetic field rise time difference or the magnetic field fall time difference generated by the brushless DC motor via the magnetic field change curve, wherein the magnetic field rise time difference is from the minimum magnetic flux density (B _min) to maximum magnetic flux density during the (B _max), the rise time is calculated via the hysteresis counter the negative magnetic flux density (B _H-) to the positive hysteresis increment Flux density (B _{H +)} of the section, and the magnetic field lines fall time difference from the maximum magnetic flux density (B _max) to a minimum during which the magnetic flux density (B _min), is calculated via the fall time of the positive hysteresis counter magnetic flux density (B _H+ ) is decremented to the interval of the negative hysteresis magnetic flux density (B _H- ); the output modulation signal is generated by using the PWM duty cycle modulation circuit to divide the magnetic field rise time difference or the magnetic field fall time difference into N segments Time equalization (N is an integer), each time period has its corresponding duty cycle, and outputs a first modulation signal and a second modulation signal; and driving the brushless DC motor, using one The load driving circuit receives the first modulation signal and the second modulation signal, and generates a first output voltage and a second output voltage and an output current for driving the brushless DC motor. A brushless DC motor control method according to claim 11, wherein the PWM The duty cycle modulation circuit feedbacks a rising signal or a falling signal to the counter, and notifies the counter to calculate the magnetic field rise time difference generated by the magnetic field detecting circuit or the magnetic field falling time difference. The brushless DC motor control method according to claim 11, wherein the PWM duty cycle modulation circuit further comprises a register for temporarily storing the magnetic field rise time difference or the magnetic field fall time difference.