TW200830694A - Method and apparatus of controlling DC brushless motor - Google Patents

Abstract

The present invention relates to a method of controlling a DC brushless motor. A Hall element is used to detect the position of a magnetic pole of the motor rotor and generates a Hall signal accordingly. A driving unit is used to generate a PWM signal according to an external control signal. A switch circuit is controlled according to the PWM signal and the Hall signal; therefore the current phase outputted to the coils of the motor stator is switched to drive the rotor to rotate. The level of the external control signal is manipulated to increase or decrease gradually in accordance with the level change of the Hall signal in response to the level transition of the Hall signal. The duty cycle of the PWM signal is controlled to change from zero to a predetermined value or from the predetermined value to zero, corresponding to the increasing and decreasing of the external signal, respectively. Thus, the current surge and noise generated during the motor switching can be eliminated.

Description

200830694 IX. Description of the invention: The invention relates to a control method of a brushless DC motor, in particular to a control method and device for a brushless DC motor with pulse width modulation (PWM) control . [Prior Art] Since the brushless DC motor replaces the commutating brush of the conventional DC motor with a Hall sensor, it is more suitable for use in a micro cooling fan system than a conventional DC motor, and is widely used in, for example, a computer fan and a photocopier. Low-voltage products such as laser printers. A single-phase DC brushless motor commonly used in computer fans, as shown in Fig. 1, includes a stationary stator U around which coil windings 10 are disposed, and a four-pole rotor 12 that drives the rotation of the fan blades. Referring to FIG. 2 and FIG. 3 and referring to FIG. 3, there is a conventional control device 2 for driving a single-phase brushless DC motor 1, which senses a motor rotor 利用2 by using a Hall sensor ((4) sensor)21. The magnetic pole position is correspondingly generated by a Hall signal sHA (which is an analog differential signal Vhp and Vhn), and the Hall signal is input into a comparator 22 to be converted into a digitized Hall signal Shd, and then sent to: the driver, twenty three. a PWM generator, 24 according to an external control signal

Sc (voltage signal) generates a pWM signal and sends it to the driver 23. The driver 23 according to the Hall signal S rib and the PWM signal, corresponding to the rotor 12 magnetic pole position in turn, the first pwM signal Sp and the second request as shown in FIG. The motor rotor 12 is driven to rotate by a signal SPWM2 to alternately switch the phase of the output current W outputted to the motor die coil 10 as shown in FIG. 3 by a switching circuit 25 at the rear end. 200830694 However, due to the instantaneous change of the level generated when the PWM signal Spw(4) and the second pwM signal SPWM2 are switched, the output current IDUt is at this Ip', which causes mechanical resonance and noise when the motor is rotated. SUMMARY OF THE INVENTION Therefore, the object of the present invention is to provide a control method and apparatus for a DC brushless motor capable of eliminating output current surges.

Therefore, the control method of the brushless DC motor of the present invention, wherein the motor has a stator around which the coil is wound and a rotor that rotates around the stator, the control method uses the - Hall element to detect the magnetic pole position of the rotor to correspondingly generate a The driving signal generates a PWM signal according to an external control signal, and controls a switching circuit to switch the current phase of the outputting the i-stator coil according to the pWM signal and the Hall signal to drive the rotor to rotate: in particular, The control method further comprises: (4) when preparing the Hall signal to be level-converted 4, so that the level of the external control signal is incremented or decremented corresponding to the Hall signal = bit under-reduction; when the external control signal is at the level Increment = ': the duty cycle of the pWM signal generated by the driving unit is increased from zero to eight pre-processing cycles, and (C) when the level of the external control signal is decremented, the PWM signal generated by the Wei-single is generated by the The predetermined guard cycle is decremented to zero to thereby eliminate the output current surge of the switching circuit. Wherein, the Hall element is a Hall sensor, and the Hall signal is a moving 4 ratio Λ遽, which is converted into a digital signal by a comparator and then input to the I affliction area Ip* and the external The control signal is generated by a PWM duty cycle control. / working hour 200830694 as described above, in step (4), when the PWM duty cycle controller measures the differential voltage of the Hall signal to decrease to less than - the reference value, the external control signal is lowered by the reference value The period to zero is decremented from the high level to the low level, and the external control signal is incremented from the low level to the high level during the period when the differential voltage rises from zero to the reference value. Wherein, the Hall element is a Hall integrated circuit, the Hall signal is a digital signal, and the external control signal is generated by a PWM duty cycle controller.

As described above, in the step (A), the PWM duty cycle controller sets a reference value close to the count value according to the count value of the waveform before the Hall signal, and counts the current waveform of the Hall signal to the reference value. When the external control number is counted from the predetermined value to the current waveform level conversion period, 'the high level is decremented to the low level, and after the Hall signal level is converted, the external control signal is made The low level is incremented to a high level. Furthermore, the present invention provides a control device for a DC brushless motor of the above method, wherein the motor has a stator around which a coil is wound and a rotor that rotates around the stator, the control device including a Hall element, a PWM duty cycle controller , a drive unit and a switch circuit. The Hall element detects the magnetic pole position of the rotor and correspondingly generates a Hall signal. The PWM duty cycle controller receives the Hall signal and an external control signal, and when detecting that the Hall signal is about to be level-shifted, the level of the external control signal is incremented corresponding to the Hall signal level change or Decrement. The driving unit generates a PWM signal according to the external control signal, and increases the duty cycle of the output PWM signal from zero to a predetermined operation when the level of the external control signal is incremented.

And the period ′ when the level of the external control signal is decremented, the output PWM signal is decremented to zero by the predetermined duty cycle, and a driving signal is generated according to the pwM signal and the Hall signal. The switch circuit is controlled by the drive signal to switch the phase of the current output to the stator coil to drive the motor rotor to rotate. Thereby, the output current surge of the switching circuit is eliminated. Wherein, the DC brushless motor is a single-phase or two-phase DC brushless motor, the driving unit includes a PWM generator and a driver, and the pWM generator generates the PWM signal according to the external control signal, and When the level of the external control signal is incremented, the duty cycle of the output PWM signal is incremented from zero to a predetermined duty cycle, and when the level of the external control signal is decremented, the output PWM signal is decremented by the predetermined duty cycle. Up to zero; the driver generates the driving signal according to the PWM signal and the Hall signal. Where the DC brushless motor is a three-phase DC brushless motor, the driving unit is a PWM generator. As described above, the control device further includes a comparator, and the Hall element is a Hall sensor, and the Hall signal is a differential analog signal, which is converted into a digital signal by the comparator and input. Drive unit. As described above, when the PWM duty cycle controller detects that the differential voltage of the Hall signal is reduced to less than the reference value, the external control signal is caused to be lowered during the period from the reference value to zero. The level is decremented to a low level, and the external control signal is incremented from a low level to a high level during a period in which the differential voltage rises from zero to the reference value. Wherein, the Hall element is a -Horth integrated circuit, the Hall signal is a digital signal, and the PWM guard cycle controller sets a value close to the count value according to a count value of a waveform before 200830694 of the Hall signal. The reference value, and when counting the target waveform of the δ δ hole number to the reference value, the external control signal is decremented from the high level to the low level during the period from the predetermined value to the current waveform level conversion Bit, and after the conversion of the Hall signal level, the external control signal is incremented from the low level to the high level. [Embodiment] The foregoing and other technical contents, features, and effects of the present invention will be apparently described in the following detailed description of the four preferred embodiments of the tea. Referring to FIG. 1, FIG. 4 and FIG. 5, it is a first preferred embodiment of the control device for the brushless DC motor of the present invention. The DC brushless motor is a single-phase DC brush motor, and its structure is as shown in FIG. The illustration includes a stator 11 around which a coil winding 10 is disposed and a quadrupole rotor 12 that rotates around the stator. The control device 3 of this embodiment includes a Hall sensor 31, a PWM duty cycle controller 32, a driving unit 30, and a switching circuit 35. The drive unit 3 further includes a PWM generator 33 and a driver 34, and the switch circuit 35 is an H_bridge (H-bridge) circuit composed of four transistors. The Muir sensing 31 is disposed adjacent to the motor rotor 12 to sense the magnetic pole position of the motor rotor 12 and correspondingly generate a Hall signal center as shown in FIG. 5, which is a type of differential signal vHP and vHN), the Hall signal Sha is converted into a digital signal Shd via a comparator 36 and input to the driver 34. The PWM duty cycle controller 32 receives an external control signal Sc and a Hall signal Sha as shown in FIG. 5, and the external control signal heart is a DC voltage 200830694 signal, which is used to control the PWM generator 33 and change it. The voltage level of the PWM signal output by the voltage level modulation PWM generator 33 (ie, the duty cycle), for example, when the voltage level is 5 V, the duty cycle of the PWM signal is 50%, and the voltage level is 2.5 V, the PWM signal is The work cycle is 25%. In this embodiment, in order to eliminate the output current lout of the switching circuit 35, the PWM duty cycle controller 32 sets a reference value (ie, reference voltage) Vref, and detects the differential voltage VD of the Hall signal SHA (absolutely Whether the value is reduced to be less than the reference value Vref, and if so, the period during which the external control signal Sc is lowered from the reference value Vref to zero (zero crossing point) is reduced from a high level (for example, 5V) to The low level (for example, 0V), and the period T2 when the differential voltage VD (absolute value) rises from zero (zero crossing point) to the reference value Vref, causes the external control signal Sc to be incremented from the low level (0V) to the high level. The level (5V) is output to the PWM generator 33 via an edge-adjusted external control signal Sc' as shown in FIG. Therefore, when the PWM generator 33 receives the external control signal Sc', it modulates the pulse width (duty cycle) of the PWM signal output according to the voltage level of the external control signal Sc', and generates as shown in FIG. The PWM signal SPWM' is input to the driver 34. The PWM signal Spwm 'corresponds to the high-level waveform of the external control signal Sc' to generate a uniform pulse width (for example, 50%), but the incremental edge and the decreasing edge portion corresponding to the external control signal Sc' are adjusted according to the voltage increment or decrement. The pulse width is such that the pulse width corresponds to the decreasing and increasing 〇 driver 34 alternately outputs the first according to the PWM signal position of the rotor 12 corresponding to the PWM signal S PWM and the Hall signal Shd. ^^^1 Signal 81^1^' and 10 200830694 The second PWM signal Spwm2' turns the control switch circuit 35. Therefore, when the switching circuit 35 is alternately controlled by the first PWM signal S PWM1 ' and the second PWM signal S PWM2' to output the current lout, when switching between the first PWM signal Spwmi' and the second P signal Spwm2'PWM , instead of switching instantaneously, as shown in FIG. 6, after the pulse width of the first PWM signal SPWM1 ' is gradually decreased to zero by a predetermined duty cycle (50%), the pulse width of the second PWM signal SPWM2' is gradually increased. It is incremented to a predetermined duty cycle (50%), so that the switching circuit 35 does not generate an instantaneous surge on the output current Iout due to the instantaneous switching of the PWM signal, thereby eliminating the output current surge. Referring to FIG. 7 again, it is a second preferred embodiment of the control device for the brushless DC motor of the present invention. The only difference from the first embodiment is that the present embodiment is a Hall integrated circuit (ie, Huo The IC) 31' replaces the Hall sensor 31 of the first embodiment, and because the Hall IC3 直接 directly outputs a digital signal SHd as shown in FIG. 5 corresponding to the sensed rotor magnetic pole position. Therefore, the present embodiment does not require the comparator 36 of the first embodiment. • However, since the output of the Hall 1C 31' is a digital signal SHD instead of an analog signal, in this embodiment, in order to know the level transition point of the Hall signal SHD, the level of the external control signal is adjusted correspondingly. In the present embodiment, the PWM period controller 32 uses a counter to count the period of the Hall signal SHD to obtain a high-level waveform (N) and a low-level waveform. The count value of (S), and the next waveform (i.e., the current waveform) is estimated based on the count value CP of the previous waveform, and a reference value Cref is set, and the reference value Cref is close to but smaller than the count value CP. 11 200830694 Therefore, when the PWM period controller 32 counts the count value of the current waveform to reach the kite value cref, the reference value Cref is counted to the period h before the current waveform level conversion, so that the external control signal Sc is from the high level. Decrease to the low level, and after the Hall signal SHd level conversion, the external control signal Sc is incremented from the low level to the high level, and the edge-adjusted external control signal Sc as shown in FIG. 5 is output to the PWM. Generator 33. Therefore, as in the first embodiment, the PWM generator 33 modulates the pulse width according to the voltage level of the external control signal Sc, thereby generating the PWM signal sPWM as shown in FIG. Referring to FIG. 8 again, it is a third preferred embodiment of the control device for the brushless DC motor of the present invention. This embodiment is for controlling a two-phase DC brushless motor, and since the stator of the two-phase DC brushless motor has The two coil windings are separately controlled. Therefore, the present embodiment is mainly a switch circuit 35 for controlling the stator coil 1 of the motor, which is different from the second embodiment. Referring to FIG. 9, which is a fourth preferred embodiment of the control device for the brushless DC motor of the present invention, the present embodiment is for controlling a three-phase DC brushless motor, which is different from the foregoing embodiment. DC brushless motor: There are two coil windings Lu, Lv, Lw to be separately controlled, so this embodiment uses three Hall sensing ICs 31 to sense the magnetic pole position of the motor rotor, respectively, and three-phase DC The brush motor is generally controlled by a two-phase modulation method, that is, only one phase of the stator three-phase coil is controlled to be turned on and the other y phase is maintained in a floating state, so the switch circuit 35 of the embodiment has Three parallel bridge arms, each having two switching elements, namely upper arm elements Q3, Q5 and lower arm elements Q2, Q4, Q6. Therefore, as shown in FIG. 1A, 12 200830694 three Hall sensing ICs 3i respectively generate sensing signals such as Hv, Hw, and output to the PWM duty cycle controller 32, and the driving unit 3A, and the embodiment The drive unit 3G is a -pwm generator. According to the foregoing first embodiment, the PWM duty cycle controller 32 generates an external control signal S1, ~V through the edge (4) according to the sensing signal, the office, the Hw and the external control signals Si~S6. The unit (PWM generator) 3〇 causes the driving unit (JWM to generate |§) 3Q to generate the edge pulse width increasing or decreasing signal sPWM1 according to the sensing signal shame, Ην, η, and the external control signal S!~S6~ The sPWM2 output controls the switching elements Q1 to Q6 of the switching circuit 35" to drive the motor rotor to rotate, and the switching circuit 35" does not instantaneously switch the output current due to the instantaneous switching of the PWM signal, thus eliminating the The motor produces a noise output current surge. As can be seen from the above description, the present invention prepares the drive signal by relatively increasing or decreasing the pulse width of the corresponding PWM signal by adjusting the voltage level of the external control signal Sc during the period. The output current W generated by the PWM signal control/off circuit 35 does not cause a surge due to the instantaneous switching of the PWM signal by the driver 34, thereby reducing the mechanical resonance and noise generated by the motor due to the current surge. However, the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the scope of the invention and the scope of the invention. Modifications are within the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic structural view of a conventional DC brushless motor; 13 200830694 FIG. 2 is a circuit block diagram of a conventional DC brushless motor control device; FIG. 3 is an output signal of the control device of FIG. FIG. 4 is a circuit block diagram of a first preferred embodiment of a DC brushless motor control device according to the present invention, illustrating a control mode of a single-phase DC brushless motor; FIG. 5 is an output signal waveform of the control device of FIG. Figure 6 is a partial enlarged view of the first pwm signal of the DC brushless motor of the present invention; Figure 7 is a circuit block diagram of a second preferred embodiment of the control device for the brushless DC motor of the present invention, illustrating another type of single-phase DC brushless motor Figure 8 is a circuit block diagram of a third preferred embodiment of the control device for the brushless DC motor of the present invention, illustrating the control mode of the two-phase DC brushless motor; and Figure 9 is a control of the DC brushless motor of the present invention. A book block diagram of a fourth preferred embodiment of the device, illustrating a control mode of the three-phase DC brushless motor; and FIG. 1A is a schematic diagram of an output signal waveform of the control device of the fourth embodiment 14200830694 [mainly reference numerals DESCRIPTION

3 control device 30 drive unit 3 1 Hall sensor 31 'Hall 1C 32, 32' PWM duty cycle controller 33 PWM generator 34 driver 35, 35', 35" switch circuit 36 comparator 10, 10", Lu, Lv, Lw coil 11 stator

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Claims (1)

200830694 X. Patent application scope: 1. A control method for a DC brushless motor, the motor has a stator around which a coil is wound and a rotor that rotates around the stator, and the method uses a Hall element _ the magnetic pole position of the rotor Corresponding generation of the Hall signal, the driving unit generates a PWM signal i according to an external control signal, and according to the 4 PWM signal and the Hall signal, a switching circuit is controlled, and the current phase of the output is output to the stator coil. Driving the rotor to rotate; Spring is characterized by the method further comprising: (A) when detecting that the Hall signal is about to be level-shifted, the external control A 5 tiger's level is incremented corresponding to the Hall signal level change or (B) when the level of the external control signal is incremented, the duty cycle of the PWM signal generated by the driving unit is incremented from zero to a predetermined duty cycle; and (C) when the level of the external control signal is decremented The PWM signal generated by the driving unit is decremented to zero by the predetermined duty cycle. _ 2· The invention relates to a method for controlling a DC brushless motor according to the scope of the patent, wherein the Hall element is a Hall sensor, and the Hall signal is a differential analog signal, which is passed through a comparator. After the digital signal is converted into the driving unit, the external control signal is generated by a PWM duty cycle. 'Work, 3. According to the control method of the DC brushless motor according to the second item of the patent application scope, in the step (A), when the PWM duty cycle controller detects that the differential voltage of the Hall number is reduced to less than When a reference value is obtained, the period of the differential signal is reduced from the reference value to zero by a period of time; the value of the differential voltage is reduced to a low level, and the differential voltage is raised from zero to the reference value. During the period, the external control signal is incremented from a low level to a high level. 4. The control method of the DC brushless motor according to Item 1 of the patent application scope, wherein the Hall element is a Hall integrated circuit, the Hall signal is a digital signal, and the external control signal is a PWM The duty cycle controller is generated. 5 . According to the control method of the DC brushless motor according to Item 4_ of the patent application scope, in step (A), the PWM duty cycle controller sets a value close to the count value according to the count value of a waveform before the Hall signal. The reference value is used to count the current waveform of the Hall signal to the reference value, and the external control signal is decremented from the high level to the low level during the period from the predetermined value to the current waveform level conversion. After the conversion of the Hall signal level, the external control signal is incremented from a low level to a high level. 6. A DC brushless motor control device, the motor having a stator winding a coil and a rotor rotating around the stator, the control device comprising: a Hall element detecting the magnetic pole position of the rotor and correspondingly generating a Hall signal; PWM duty cycle controller, accepting the Hall signal and an external control signal' and detecting the Hall signal to be level-shifted, making the external control number correspond to the Hall signal The bit change is incremented or decremented; the , , , and the dynamic unit generates a pwM signal according to the external control signal, and when the level of the external control signal is incremented, the duty cycle of the output PWM signal is incremented from zero to _ predetermined During the duty cycle, when the level of the control signal is decremented, the output PWM signal is decremented from zero to zero, and the drive signal is generated based on the pWM signal and the Hall signal; The turtle path is controlled by the drive signal to switch the phase of the current output to the stator coil to drive the motor rotor to rotate. A control device for a DC brushless motor according to Item 6 of the patent scope, wherein the DC brushless motor is a single-phase or two-phase DC brushless motor, and the moving unit comprises a PWM generator and a driver, the pwM The generating wood generates the pWM signal according to the external control signal, and when the external=control signal is incremented, the working week of the output pwM signal is 'delivered to the pre-working period, and externally When the level of the control signal is decremented, the output pWM signal is decremented to zero by the predetermined duty cycle; the driver generates the driving signal according to the PWM signal and the Hall signal. 8. The control device of the DC brushless motor according to the scope of Patent Application 帛6, wherein the DC brushless motor is a three-phase DC brushless motor, and the driving unit is a PWM generator. 9. The control device of the brushless DC motor according to the seventh or eighth aspect of the patent scope includes a comparator, and the Hall element is a _ Hall sensor, and the X 雈 λ 疋 differential analog signal It is converted into a digital signal by the comparator and then input to the driving unit. 10. The control device of the DC brushless motor according to claim 9 of the patent application scope, wherein when the PWM duty cycle controller detects that the differential voltage of the Hall signal decreases to less than a reference value, the external control signal is During the period when the differential voltage is reduced to zero by the reference value, the high voltage is decremented to a low level and the external control signal is raised from zero to the reference value during the period from the low level to the reference value. Increase to the high level. U. The control device for a DC brushless motor according to the application of the invention, wherein the Hall element is a Hall integrated circuit, the Hall signal is a bit signal, and the PWM duty cycle controller Setting a reference value close to the count value according to the count value of the first waveform of the Hall signal, and counting the current waveform of the Hall signal to the reference value, so that the external control signal is counted from the predetermined value to the current During the period before the waveform level conversion, the high level is decremented to the low level, and after the Hall signal level is converted, the external control signal is incremented from the low level to the high level. 19