Abstract:
There are provided a motor controlling circuit, a motor driving device, and a motor controlling method. The motor controlling circuit includes: a frequency detecting unit detecting a frequency of an internal clock signal of a motor driving circuit; a sampling unit sampling an input pulse width modulation (PWM) signal using the frequency of the internal clock signal; and a calculating unit sensing a change in a speed of the internal clock signal from a sampling result of the sampling unit and calculating a revolution per minute (RPM) of a motor from the sensed change in the speed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of Korean Patent Application No. 10-2011-0134252 filed on Dec. 14, 2011, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a motor controlling circuit, a motor driving device, and a motor controlling method capable of accurately detecting a revolution per minute (RPM), a rotation speed, or the like, of a motor, regardless of a change in an internal temperature, or the like, thereof. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, the speed of a motor, such as a brushless direct current (BLDC) motor, whose speed is capable of being controlled, may be controlled through adjusting a duty value of a pulse width modulation (PWM) signal. The duty value of the PWM signal may be determined according to a section between a turn-on time, in which the signal has a high value in one period thereof, and a turn-off time, in which the signal has a low value in one period thereof, and the rotation speed of the motor may be in proportion to the duty value of the PWM signal. 
         [0006]    Motor speed controlling schemes may be largely divided into an open loop control scheme and a closed loop control scheme. The open loop control scheme does not require a feedback circuit, such that it may be implemented using a simple structure; however, it may not compensate for an error generated due to an external factor such as electrical noise, a temperature change, or the like. On the other hand, in the case of the closed loop control scheme, a feedback circuit is included, such that a current RPM, a speed, a surrounding operational environment, and the like, of a motor, are detected and an input signal is controlled with reference to the detection results, whereby an error generated in an operation of the motor may be controlled. 
         [0007]    As a result, in the case of the closed loop control scheme, a circuit for detecting current RPM, a speed, and the like, of the motor, is required, and a temperature detecting circuit, a voltage detecting circuit, and the like, may also be added. Therefore, complicity of the circuit increases, and an effect due to a surrounding operational environment may not accurately reflected in detecting the RPM and speed of the motor in the case in which the temperature detecting circuit, the voltage detecting circuit, and the like, are excluded from a circuit configuration. 
       SUMMARY OF THE INVENTION 
       [0008]    An aspect of the present invention provides a motor controlling circuit, a motor driving device, and a motor controlling method in which an input pulse width modulation signal is sampled using a frequency of an internal clock signal of a motor driving circuit and a change in a speed of the internal clock signal is sensed from the sampled result to control a speed of a motor, such that an operation of the motor may be accurately controlled through a reflection of a surrounding environment effect without a separate temperature or voltage detection circuit. 
         [0009]    According to an aspect of the present invention, there is provided a motor controlling circuit including: a frequency detecting unit detecting a frequency of an internal clock signal of a motor driving circuit; a sampling unit sampling an input pulse width modulation (PWM) signal using the frequency of the internal clock signal; and a calculating unit sensing a change in a speed of the internal clock signal from a sampling result of the sampling unit and calculating a revolution per minute (RPM) of a motor from the sensed change in the speed. 
         [0010]    The sampling unit may calculate a sampling number of the input PWM signal during one period using the frequency of the internal clock signal. 
         [0011]    The calculating unit may determine that the speed of the internal clock signal has decreased when the sampling number of the input PWM signal during one period decreases, while determining that the speed of the internal clock signal has increased when the sampling number of the input PWM signal during one period increases 
         [0012]    The motor controlling circuit may further include a speed controlling unit controlling a rotation speed of the motor from the RPM of the motor, calculated by the calculating unit. 
         [0013]    According to another aspect of the present invention, there is provided a motor driving device including: a frequency detecting unit detecting a frequency of an input PWM signal; a comparing unit detecting a driving RPM of a motor and comparing the detected driving RPM of the motor with an RPM according to a duty value of the input PWM signal; and a signal generating unit generating a driving signal for the motor, based on a comparison result of the comparing unit, wherein the comparing unit detects the driving RPM of the motor using the frequency of the input PWM signal. 
         [0014]    The comparing unit may detect the driving RPM of the motor by sampling one period of a clock signal for driving the motor using the frequency of the input PWM signal. 
         [0015]    According to another aspect of the present invention, there is provided a motor controlling method including: detecting a frequency of an internal clock signal of a motor driving circuit; sampling an input PWM signal using the frequency of the internal clock signal; sensing a change in a speed of the internal clock signal from a sampling result for the input PWM signal; and calculating an RPM of a motor from the sensed change in the speed. 
         [0016]    In the sampling of the input PWM signal, a sampling number of the input PWM signal during one period may be counted based on the frequency of the internal clock signal. 
         [0017]    In the sensing of the change in the speed, it may be determined that the speed of the internal clock signal has decreased when a sampling number of the input PWM signal during one period decreases, while it may be determined that the speed of the internal clock signal has increased when the sampling number of the input PWM signal during one period increases. 
         [0018]    The motor controlling method may further include controlling a rotation speed of the motor from the sensed change in the speed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0020]      FIG. 1  is a block diagram schematically showing a motor controlling circuit according to an embodiment of the present invention; 
           [0021]      FIGS. 2 and 3  are block diagrams schematically showing a motor driving device according to the embodiment of the present invention; 
           [0022]      FIG. 4  is a graph provided in order to describe a motor driving method according to the embodiment of the present invention; and 
           [0023]      FIGS. 5 and 6  are flow charts provided in order to describe a motor driving method according to the embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Embodiments of the present invention will be described in detail with reference to the accompanying drawings These embodiments will be described in detail for those skilled in the art in order to practice the present invention. It should be appreciated that various embodiments of the present invention are different but do not have to be exclusive. For example, specific shapes, configurations, and characteristics described in an embodiment of the present invention may be implemented in another embodiment without departing from the spirit and the scope of the present invention. In addition, it should be understood that position and arrangement of individual components in each disclosed embodiment may be changed without departing from the spirit and the scope of the present invention. Therefore, a detailed description described below should not be construed as being restrictive. In addition, the scope of the present invention is defined only by the accompanying claims and their equivalents if appropriate. Similar reference numerals will be used to describe the same or similar functions throughout the accompanying drawing. 
         [0025]    Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily practice the present invention. 
         [0026]      FIG. 1  is a block diagram schematically showing a motor controlling circuit according to an embodiment of the present invention. Referring to  FIG. 1 , a motor controlling circuit  100  according to the embodiment of the present invention may include a frequency detecting unit  110 , a sampling unit  120 , a calculating unit  130 , and a speed controlling unit  140 . An operation of a motor may be controlled according to a signal output from the speed controlling unit  140 . For example, the controlling unit  140  may control a rotation speed, or the like, of the motor by adjusting a duty value of a pulse width modulation (PWM) signal. 
         [0027]    The frequency detecting unit  110  and the sampling part  120  may be connected to the speed controlling unit  140  and the calculating unit  130 , respectively, to thereby configure a feedback circuit. The frequency detecting unit  110  receives a driving signal S D  output from the speed controlling unit  140  to the motor or a parameter used to generate the driving signal S D  to thereby detect a frequency f D  of the driving signal S D  output to the motor. Since the detected frequency f D  is the frequency f D  of the driving signal S D  for driving the motor, it may be changed due to a change in an external environment such as a temperature change, or the like. As described below, a driving speed of the motor may be accurately detected from the frequency f D  of the driving signal S D  changed according to the change in the external environment. For example, the frequency f D  may be detected from the driving signal S D  provided in the form of a clock signal. 
         [0028]    The sampling unit  120  may sample an input pulse width modulation signal I PWM  using the frequency f D  of the driving signal S D  detected by the frequency detecting unit  110 . The input pulse width modulation signal I PWM  may be a signal generated and input from the outside of the motor controlling circuit  100 . Therefore, the input pulse width modulation signal I PWM  is generated independently of a driving environment of the motor, such that it is not affected by the change in the external environment such as the temperature change, or the like. Therefore, when it is assumed that the input pulse width modulation signal I PWM  has a predetermined period and duty value, the sampling result output from the sampling unit  120  to the calculating unit  130  may be determined based on the frequency f D  detected by the frequency detecting unit  110 . 
         [0029]    For example, assumed that a sampling number of the input pulse width modulation signal I PWM  when the input pulse width modulation signal I PWM  is sampled by the frequency f D  is 10 in a predetermined time section t 1  in which the motor is driven and the sampling number of the input pulse width modulation signal I PWM  when the input pulse width modulation signal I PWM  is sampled by the frequency f D  decreases to 7 in another time section t 2 , the frequency D is relatively decreased in the time section t 2  as compared to in the time section t 1 , which means that an internal clock speed decreases. Therefore, if the sampling number of the input pulse width modulation signal I PWM  when the input pulse width modulation signal I PWM  is sampled by the frequency f D  decreases, it may be recognized that the internal clock speed decreases. If the sampling number of the input pulse width modulation signal I PWM  when the input pulse width modulation signal I PWM  is sampled by the frequency f D  increases, it may be recognized that the internal clock speed increases. 
         [0030]    A change in the internal clock speed sensed by the above-mentioned scheme may be reflected to accurately sense a speed of the motor. That is, when it is recognized that the internal clock speed decreases by 10%, an actual speed of the motor may be detected by decreasing a motor speed detected by a speed detecting unit (not shown) detecting the motor speed from the RPM of the motor by 10%. Conversely, when it is recognized that the internal clock speed increases by 10%, the actual speed of the motor may be detected by increasing the motor speed detected from the RPM of the motor by 10%. 
         [0031]      FIG. 2  is a block diagram schematically showing a motor driving device according to the embodiment of the present invention. Referring to  FIG. 2 , the motor driving device  200  according to the embodiment may include a frequency detecting unit  210 , a comparing unit  220 , a signal generating unit  240 , and a motor  250 . The frequency detecting unit  210  and the comparing unit  220  may configure a feedback circuit, and the motor  250  receiving the driving signal S D  from the signal generating unit  240  to perform an operation may be a brushless direct current (BLDC) motor. 
         [0032]    Similar to  FIG. 1 , the comparing unit  220  receives the input pulse width modulation signal I PWM  and the frequency f D  detected by the frequency detecting unit  210  from the signal generating unit  240  and samples the input pulse width modulation signal I PWM  using the detected frequency f D . The frequency detecting unit  210  may detect the frequency f D  from a parameter internally adjusted in order to determine the driving signal S D  transferred to the motor  250  by the signal generating unit  240  or detect the frequency f D  directly from the driving signal S D  output from the signal generating unit  240 . That is, since the frequency f D  detected by the frequency detecting unit  210  is determined by the driving signal S D  of the motor  250 , it may be changed according to a driving environment of the motor  250 . 
         [0033]    The comparing unit  220  may sample the input pulse width modulation signal I PWM  using the frequency f D  detected by the frequency detecting unit  210 . The input pulse width modulation signal I PWM , a signal generated and supplied from the outside of the motor driving device  200 , independently from the driving environment of the motor  250 , has a predetermined period and duty value. Therefore, the sampling result generated and output by the comparing unit  220  may be determined based on the frequency f D  detected by the frequency detecting unit  210 . Therefore, it can be seen that a variation in the sampling result output by the comparing unit  220  may correspond to a variation in the frequency f D  detected by the frequency detecting unit  210  from the signal generating unit  240 . The signal generating unit  240  may sense a change in a speed of the driving signal S D  supplied to the motor  250  from the variation in sampling result. 
         [0034]      FIG. 3  is a block diagram schematically showing a motor driving device according to the embodiment of the present invention. Referring to  FIG. 3 , a motor driving device  300  according to the embodiment may include a speed detecting unit  310  detecting a speed of a motor  350 , a comparing unit  320 , an input pulse width modulation signal I PWM  frequency detecting unit  330 , a signal generating unit  340 , and the like. As described above with reference to  FIGS. 1 and 2 , the input pulse width modulation signal I PWM , which is a signal generated from the outside, independently from the motor driving device  300 , may have a predetermined period, a predetermined duty value, and the like, independently from a driving environment of the motor  350 . In addition, the motor  350  may be a BLDC motor. 
         [0035]    The speed detecting unit  310  may detect a driving speed of the motor  350  from an RPM of the motor  350 . Since the driving speed of the motor  350  needs to be maintained as a value designated by a user, the overall operation of the motor driving device  300  may be performed such that the driving speed of the motor  350  is detected and the driving speed of the motor  350  is decreased by adjusting the driving signal S D  output from the signal generating unit  340  to the motor  350  when the detected driving speed is higher than the value designated by the user, while the driving speed of the motor  350  is increased when the detected driving speed is lower than the value designated by the user. 
         [0036]    The speed detecting unit  310  may use the input pulse width modulation signal I PWM  in order to detect the driving speed of the motor  350 . That is, the driving signal S D  for operating the motor  350  may be sampled using a frequency detected by the input pulse width modulation signal I PWM  frequency detecting unit  330 , and the driving speed of the motor  350  may be detected from the sampling result. The sampling method and speed detecting method as described with reference to  FIGS. 1 and 2  may be used. 
         [0037]    Apart from the input pulse width modulation signal I PWM  supplied from the outside, the driving signal S D  supplied from the signal generating unit  340  to the motor  350  may also be generated in the form of a pulse width modulation signal. In this case, the driving speed of the motor  350  may be determined by a duty value of the driving signal S D . That is, when the duty value of the driving signal S D  increases, the driving speed of the motor  350  increases, while when the duty value of the driving signal S D  decreases, the driving speed of the motor  350  decreases. 
         [0038]    In the case in which the driving signal S D  supplied to the motor  350  is in the form of the pulse width modulation signal, a method of detecting the driving speed of the motor  350 , performed by the speed detecting unit  310  may also be based on the duty value of the driving signal S D . That is, since the duty value is determined by a ratio of an interval between a timing in which the driving signal S D  is turned and has a high value and a timing in which the driving signal S D  is turned off and has a low value, the driving speed of the driving signal S D  may be detected by calculating the duty value of the driving signal S D  using a period of the driving signal S D  and the timing in which the driving signal S D  has the high value and converting the duty value into a driving RPM of the motor  350 . 
         [0039]    The comparing unit  320  may include a duty value calculator  322 , an RPM generator  324 , and a comparator  326 . Similar to the cases of  FIGS. 1 and 2 , the comparing unit  320  may receive the input pulse width modulation signal I PWM  and calculate a duty value of the input pulse width modulation signal I PWM  in the duty value calculator  322 . The duty value calculator  322  may calculate the duty value of the input pulse width modulation signal I PWM  from a period of the input pulse width modulation signal I PWM  and a timing in which the input pulse width modulation signal I PWM  has a high value, similar to the speed detecting unit  310 . 
         [0040]    The RPM generator  324  may generate the RPM of the motor  350  corresponding to the duty value of the input pulse width modulation signal I PWM . The RPM generator  324  may read the RPM of the motor  350  corresponding to the duty value of the input pulse width modulation signal I PWM  with reference to a relationship between the duty value of the input pulse width modulation signal I PWM  previously prepared as data or the like, and the RPM of the motor  350 , or may generate the RPM of the motor  350  according to the duty value of the input pulse width modulation signal I PWM  by directly performing calculation according to a specific formula. 
         [0041]    The comparator  326  may compare the RPM of the motor  350  generated by the RPM generator  324  with the RPM of the motor  350  directly detected by the speed detecting unit  310  and transmit the comparison result to the signal generating unit  340 . When both of the speed detecting unit  310  and the RPM generator  324  transfer data in an RPM format of the motor  350 , the comparator  326  may compare data and transfer information on whether the RPM of the motor  350  detected by the speed detecting unit  310  is greater than the RPM of the motor  350  generated by the RPM generator  324 , to the signal generating unit  340 . The signal generating unit  340  may determine whether to increase or decrease the speed of the motor  350  from the comparison result of the comparator  326 , thereby adjusting the driving signal S D . 
         [0042]      FIG. 4  is a graph provided in order to describe a motor driving method according to the embodiment of the present invention. In  FIG. 4 , first and second waveforms  410  and  420  are provided in order to describe a process of sampling the input pulse width modulation signal I PWM  having the same period and duty value through using different frequencies. 
         [0043]    Referring to the first waveform  410 , the input pulse width modulation signal I PWM  is sampled using a first frequency. More specifically, the input pulse width modulation signal I PWM  is sampled total seven times using the first frequency during a turn-on time thereof. On the other hand, in the case of the second waveform  420 , the input pulse width modulation signal I PWM  is sampled using a second frequency. More specifically, the input pulse width modulation signal I PWM  is sampled total five times using the second frequency during the turn-on time thereof. 
         [0044]    As described above, in the motor controlling circuit  100  or the motor driving devices  200  and  300  according to the embodiment of the present invention, the input pulse width modulation signal I PWM  may be a signal determined regardless of the driving environments of the motors  250  and  350 . Therefore, even in the case in which the driving environments of the motor  250  and  350  are changed, the input pulse width modulation signal I PWM  may have a predetermined period and duty value regardless of the driving environments of the motors  250  and  350 . On the other hand, since the frequency f D  used to sample the input pulse width modulation signal I PWM  may be detected from the signal generating units  240  and  340  generating the driving signal S D  for the motors  250  and  350 , it may be changed according to the driving environments of the motors  250  and  350 . 
         [0045]    As a result, the input pulse width modulation signal I PWM  having a predetermined period and duty value is sampled using the frequency f D  determined according to the driving environments of the motors  250  and  350 , whereby the RPM and the speed of the motors  250  and  350  may be accurately detected. As shown in  FIG. 4 , when the sampling number of the input pulse width modulation signal I PWM  decreases, it is determined that the RPM of the motors  250  and  350  has increased than an actual instruction speed due to an environmental factor, or the like, while when the sampling number increases, it is determined that the RPM of the motors  250  and  350  has increased than an actual instruction speed. 
         [0046]      FIGS. 5 and 6  are flow charts provided in order to describe a motor driving method according to the embodiment of the present invention. Hereinafter, the flow chart of  FIG. 5  will be described with reference to the embodiment of  FIG. 1 . However, the flow chart of  FIG. 5  may also be applied to embodiments other than that of  FIG. 1 . 
         [0047]    Referring to  FIG. 5 , in the motor driving method according to the embodiment of the present invention, first, a frequency of an internal clock signal may be detected (S 500 ). The internal clock signal may be the driving signal S D  supplied from the speed controlling unit  140  in order to drive the motor, and the frequency f D  of the driving signal S D  may be detected in the frequency detecting unit  110 . 
         [0048]    After the frequency f D  of the internal clock signal is detected, the input pulse width modulation signal I PWM  may be sampled (S 510 ). For example, the sampling unit  120  may receive the input pulse width modulation signal I PWM  and sample the input pulse width modulation signal I PWM  using the frequency f D  of the internal clock signal detected by the frequency detecting unit  110 . 
         [0049]    From the sampling result of operation S 510 , a change in a speed of the internal clock signal for driving the motor may be sensed (S 520 ). The calculating unit  130  determines that the driving speed of the motor was increased when the sampling number of the input pulse width modulation signal I PWM  during the turn-on time thereof increases, while determining that the driving speed of the motor was decreased when the sampling number of the input pulse width modulation signal I PWM  during the turn-off time thereof decreases, using the sampling result. 
         [0050]    From the change in the speed sensed in operation S 520 , the RPM of the motor is sensed (S 530 ). As described above, when it is recognized that the sampling number decreases by 5%, the actual RPM of the motor may be sensed by decreasing a theoretical RPM calculated from the driving signal S D  actually supplied to the motor by 5%. To the contrary, when it is recognized that the sampling number increases by 5%, the actual RPM of the motor may be sensed by increasing a theoretical RPM calculated from the driving signal S D  actually supplied to the motor by 5%. The actual RPM of the motor sensed as described above may be used to generate the driving signal S D  in order that the motor is actually operated according to an operation condition of the motor designated by the user. 
         [0051]      FIG. 6  is a flow chart provided in order to describe a motor driving method according to the embodiment of the present invention. Hereinafter, the flow chart of  FIG. 6  will be described with reference to the embodiment of  FIG. 2 . However, the flow chart of  FIG. 6  may also be applied to embodiments other than that of  FIG. 2 . 
         [0052]    Referring to  FIG. 6 , in the motor driving method according to the embodiment of the embodiment, first, a frequency of an internal clock signal may be detected (S 600 ). Similar to the case of  FIG. 5 , the internal clock signal may be the driving signal S D  supplied from the signal generating unit  240  in order to drive the motor, and the frequency f D  of the driving signal S D  may be detected in the frequency detecting unit  210  of the feedback circuit  230 . 
         [0053]    After the frequency f D  is detected, the sampling number of the input pulse width modulation signal I PWM  during one period thereof is counted (S 610 ). As shown in the graph of  FIG. 4 , the comparing unit  220  may sample the input pulse width modulation signal I PWM  using the frequency f D  during the time in which the input pulse width modulation signal I PWM  is turned on and may count the sampling number of the input pulse width modulation signal I PWM . After the sampling and the counting of the sampling number are completed, it is determined that whether the counted sampling number is increased (S 620 ). Operation S 620  of determining whether the sampling number is increased may be performed by comparing a previous period and a current period to determine whether the sampling number is increased in the current period as compared to in the previous period. 
         [0054]    When it is determined that the sampling number was increased as a result of the determination of operation S 620 , the signal generating unit  240  receives the determination result from the comparing unit  220  to sense that the internal clock speed, that is, the speed of the driving signal S D  was increased (S 630 ). To the contrary, when it is determined that the sampling number was decreased, the signal generating unit  240  senses that the internal clock speed was increased (S 640 ). 
         [0055]    In the signal generating unit  240 , a change in the internal clock speed, that is, the speed of the driving signal S D  sensed in operation S 630  or S 640  may be reflected in sensing the RPM of the motor  250  (S 650 ) and the driving of the motor  250  may be controlled from the sensed RPM of the motor (S 660 ). Since the change in the speed of the driving signal S D  may be directly associated with a change in the RPM of the motor  250 , the signal generating unit  240  may recognize that the RPM of the motor  250  was increased or decreased by a ratio by which the speed of the driving signal S D  is increased or decreased and control the driving signal S D  output to the motor  250 , whereby a method of controlling the motor  250  in consideration of a change in an external environment such as a temperature change may be implemented. 
         [0056]    As set forth above, according to the embodiments of the present invention, the pulse width modulation signal transferred from the outside is sampled using the frequency of the internal clock signal of the motor driving circuit, the speed of the motor is controlled based on the sampling result. Therefore, the change in the speed according to the driving environment of the motor is detected without separate temperature and voltage detecting circuits, whereby the speed of the motor can be efficiently and accurately controlled. 
         [0057]    While the present invention has been shown and described in connection with the embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.