Patent Publication Number: US-2010109578-A1

Title: Motor control device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Application No. 097219391, filed on Oct. 30, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a control device, more particularly to a motor control device for a ceiling fan. 
     2. Description of the Related Art 
     A conventional ceiling fan uses a motor control device to control a rotation speed of a motor in accordance with a received input signal. The motor rotates vanes such that wind can be generated. In order to improve rotation efficiency, a brushless DC (direct current) motor is now commonly utilized. 
     The conventional motor control device for a brushless DC motor receives a grid power, and then steps down, rectifies, and filters the grid power to generate a first DC power for driving the brushless DC motor. Then, the motor control device steps down the first DC power to generate a second DC power for supply to a signal processing unit. 
     However, the task of stepping down the grid power needs to be implemented by a step-down transformer. During the process of stepping down the grid power using the step-down transformer, power is consumed, which increases the overall power consumption of the motor control device. Moreover, use of the step-down transformer results in an increase in the cost for the motor control device. 
     SUMMARY OF THE INVENTION 
     Therefore, the object of the present invention is to provide a motor control device for a ceiling fan, which can reduce power consumption and cost. 
     Accordingly, a motor control device of the present invention is adapted for controlling rotation of a brushless DC motor of a ceiling fan. The motor control device comprises a receiver unit, a magnetic sensor unit, a processing unit, a motor drive unit, an AC to DC converter unit, and a DC to DC converter unit. The receiver unit receives an input signal and outputs a command signal in accordance with the input signal. The magnetic sensor unit is adapted for detecting a magnetic pole variation of the brushless DC motor so as to generate a position signal. The processing unit is electrically connected to the receiver unit and the magnetic sensor unit, and generates a control signal in accordance with the command and position signals. The motor drive unit is electrically connected to the processing unit and the brushless DC motor, and generates a drive signal for driving the brushless DC motor in accordance with the control signal. The AC to DC converter unit includes a rectifier and a filter. The rectifier receives and rectifies a grid power, and generates a rectified power from the grid power. The filter is electrically connected to the rectifier and the motor drive unit, and filters the rectified power to generate a first DC power for supply to the motor drive unit. The DC to DC converter unit is electrically connected to the receiver unit, the magnetic sensor unit, the processing unit, the motor drive unit, and the AC to DC converter unit, and steps down the first DC power to generate a second DC power for supply to the receiver unit, the magnetic sensor unit, the processing unit, and the motor drive unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is a schematic view to illustrate a motor control device according to a preferred embodiment of the present invention in a state disposed in a ceiling fan; 
         FIG. 2  is a schematic circuit block diagram of the preferred embodiment of the motor control device according to the present invention; 
         FIG. 3  is a schematic diagram, illustrating the layout of the motor control device of the preferred embodiment on a first surface of a circuit board; and 
         FIG. 4  is a schematic diagram, illustrating the layout of the motor control device of the preferred embodiment on a second surface of the circuit board. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1 and 2 , a preferred embodiment of a motor control device  1  of the present invention is adapted for controlling rotation of a brushless DC motor  21  of a ceiling fan  2 . The motor control device  1  includes a receiver unit  11 , a magnetic sensor unit  12 , a processing unit  13 , a motor drive unit  14 , an AC to DC converter unit  15 , a DC to DC converter unit  16 , and a lamp control unit  17 . The ceiling fan  2  includes a brushless DC motor  21 , a plurality of vanes  22 , and a lamp  23 . 
     The receiver unit  11  receives an input signal and outputs a command signal in accordance with the input signal, and includes a wireless receiver  111 , a decoder  112  electrically connected to the wireless receiver  111 , and a microprocessor  113  electrically connected to the decoder  112 . The wireless receiver  111  receives the input signal wirelessly from a remote control  3 . The decoder  112  decodes the input signal received by the wireless receiver  111  to generate a decoded signal. The microprocessor  113  generates the command signal and a lamp control signal in accordance with the decoded signal, and adjusts a voltage of the command signal and a frequency of the lamp control signal in accordance with the decoded signal. 
     The magnetic sensor unit  12  is adapted for detecting a magnetic pole variation of the brushless DC motor  21  so as to generate a position signal, and includes a plurality of Hall elements  121  for detecting the magnetic pole variation of the brushless DC motor  21  so as to generate the position signal. In this embodiment, the magnetic sensor unit  12  includes three Hall elements  121 . As an example, the Hall element(s) may be a Hall effect sensor. 
     The processing unit  13  is electrically connected to the receiver unit  11  and the magnetic sensor unit  12 , and generates a control signal in accordance with the command and position signals. The processing unit  13  generates the control signal utilizing pulse-width modulation techniques. 
     The motor drive unit  14  is electrically connected to the processing unit  13  and the brushless DC motor  21 , and generates a drive signal for driving the brushless DC motor  21  in accordance with the control signal. The motor drive unit  14  utilizes the drive signal to control rotation of the brushless DC motor  21  so as to initiate and maintain a rotation speed of the brushless DC motor  21  corresponding to the command signal. 
     The AC to DC converter unit  15  includes a rectifier  151  and a filter  152 . The rectifier  151  receives and rectifies a grid power, and generates a rectified power from the grid power. The filter  152  is electrically connected to the rectifier  151  and the motor drive unit  14 , and filters the rectified power to generate a first DC power for supply to the motor drive unit  14 . In this embodiment, the rectifier  151  includes a full-wave bridge rectifier, and the filter  151  includes a capacitor. 
     The DC to DC converter unit  16  is electrically connected to the receiver unit  11 , the magnetic sensor unit  12 , the processing unit  13 , the motor drive unit  14 , and the AC to DC converter unit  15 , and steps down the first DC power to generate a second DC power for supply to the receiver unit  11 , the magnetic sensor unit  12 , the processing unit  13 , and the motor drive unit  14 . In this embodiment, the DC to DC converter unit  16  includes a switching-mode power supply. 
     The lamp control unit  17  is electrically connected to the receiver unit  11  and the lamp  23 , receives the grid power, and determines whether to supply the grid power to the lamp  23 . If the lamp control unit  17  determines to supply the grid power to the lamp  23 , the lamp control unit  17  further determines to supply an amount of the grid power to the lamp  23  in accordance with the lamp control signal to thereby control the brightness of the lamp  23 . In this embodiment, the lamp control unit  17  includes a phototriac. 
     Referring to  FIGS. 2 ,  3 , and  4 , the circuit board  18  includes a first surface  181  and a second surface  182  opposite to the first surface  181 . In this embodiment, the receiver unit  11 , the processing unit  13 , the motor driver unit  14 , the AC to DC converter unit  15 , the DC to DC converter unit  16 , and the lamp control unit  17  are disposed on the first surface  181 . The Hall elements  121  of the magnetic sensor unit  12  are disposed on the second surface  182 , which are angularly spaced apart from each other about a point that is roughly positioned in the center of the circuit board  18 . 
     In this embodiment, the received grid power is rectified and filtered to generate the first DC power for supply to the brushless DC motor  21 . During this process, the grid power is not stepped down so a step-down transformer is not required, which can reduce power consumption and cost. 
     While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.