Abstract:
A motor energy recycling device is connected to a motor, a voltage regulating power capacitor, and a switch unit, for storing energy released by the motor. The motor energy recycling device include a switching device having first to third ends for being switched to connect the third end with the first end or second end; a first diode unit; a first capacitor connected to the motor and the first diode unit for using energy released by the motor to charge the first capacitor; a first inductor; a second capacitor; a second diode unit; and a second inductor connected between the second end and the second diode and between the voltage regulating power capacitor and the second capacitor for charging the voltage regulating power capacitor via the second inductor to accomplish an energy recycling.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefits of the Taiwan Patent Application Serial Number 099142605, filed on Dec. 7, 2010, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an energy recycling device and, more particularly, to a motor energy recycling device, which is capable of recycling the not-used energy released from magnetic field changes when the motor controlled by pulse width modulation. 
     2. Description of Related Art 
     With reference to  FIGS. 1A and 1B ,  FIG. 1A  illustrates the control circuit for a typical DC motor, and  FIG. 1B  illustrates the control circuit for a typical three phase AC motor. As shown in  FIG. 1A , the control circuit includes a voltage regulating power capacitor  10 , a switch unit  11 , and a diode  12 . The voltage regulating power capacitor  10  supplies power to a DC motor  91 . The switch unit  11  controls power supply to the DC motor  91 . The diode  12  is preferably a flywheel diode. When the switch unit  11  is off, the control circuit maintains a current loop of the DC motor  91  so as to convert the energy stored in a magnetic field of the DC motor  91  into electric power. Further, the electric power passed through the diode  12  and is changed into a thermal energy to dissipate. As shown in  FIG. 1B , the three phase AC motor has a first phase  921 , a second phase  922 , and a third phase  923  with a phase difference of 120-degree therebetween. The control circuit includes a voltage regulating power capacitor  10 , a switch unit  11 , and six diodes  12 . The voltage regulating power capacitor  10  supplies power required for the first phase  921 , the second phase  922 , and the third phase  923  respectively. The switch unit  11  includes six switches  111  to control the first phase  921 , the second phase  922 , and the third phase  923  to be in or out, respectively, in order to configure the three phase AC motor into a one-in/two-out or two-in/one-out mode to thereby form a loop for running the three phase AC motor. The diodes  12  each is preferably a flywheel diode. 
     Typically, in a pulse width modulation (PWM) operation, a pulse signal is used as an input current to control the power of the motor. As shown in  FIGS. 1A and 1B , the control circuit of the pulse width modulation can turn on/off the switches  11  continuously based on an appropriate operating frequency. By adjusting the ratio of on-time and off-time of the switch unit  11 , it is able to adjust the input energy of the DC motor  91  or the three phase AC motor. 
     When the motors are controlled in such a way, the motors are kept in a cycle of increasing and decreasing of magnetic fields. When the magnetic field is decreased, the energy released by the motor is consumed by the diodes  12  in a form of heat. In this case, in every cycle of on/off of the switch unit  11 , the energy released by the motor is wasted. 
     To overcome this, a capacitor is typically added over the diodes to thereby store the energy released by the motor, and the energy stored in the capacitor can reversely charge the power capacitor immediately. Thus, when the capacitor performs a reverse energy charging, the voltage of the power capacitor instantaneously increases, and the rotating speed of the motor is increased sharply, which may cause vibration of the motor and result in a security problem or a difficulty in control of the motor. In addition, the energy stored in the capacitor can be expressed as ½CV 2 , where C is the capacitance of the capacitor and V is the voltage of the capacitor. If the voltage of the capacitor cannot be accumulated to a certain high value, a relative large amount of energy may be consumed by the recycling circuit during the energy recycling process, resulting in severely reducing the recycling performance. 
     Therefore, it is desirable to provide an improved motor energy recycling device to mitigate and/or obviate the aforementioned problems. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a motor energy recycling device, which can safely recycle the energy released by a motor and evenly deliver the recycled energy to a power capacitor. 
     To achieve the object, there is provided a motor energy recycling device to store energy released by a motor, which is connected to the motor, a voltage regulating power capacitor for providing power required for the motor, and a switch unit to control the motor. The motor energy recycling device comprises: a switching device having a first end, a second end and a third end, wherein the switching device is switched to connect the third end with the first end or the second end; a first diode unit; a first capacitor connected to the motor; the first diode unit makes energy released by the motor to charge the first capacitor; a second capacitor connected to the third end; one end of a first inductor connected to the first end and the other end of the first inductor connected between the first capacitor and the first diode; and a second end of the switching device connected between one end of the second capacitor and one end of the second diode; and the other end of a second diode connected one end of voltage regulating power capacitor; the other end of the second inductor connected the other end of voltage regulating power capacitor; and the second diode makes the second inductor to charge the voltage regulating power capacitor thereby accomplishing an energy recycling. 
     Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates the control circuit for a typical DC motor; 
         FIG. 1B  illustrates the control circuit for a typical three phase AC motor; 
         FIG. 2  is a circuit diagram of a motor energy recycling device according to a preferred embodiment of the invention; 
         FIG. 3A  is a schematic diagram illustrating an operation of the motor energy recycling device used in a DC motor control circuit; 
         FIG. 3B  is a schematic diagram illustrating another operation of a motor energy recycling device used in a DC motor control circuit; 
         FIG. 3C  is a schematic diagram illustrating a further operation of a motor energy recycling device used in a DC motor control circuit; 
         FIG. 3D  is a schematic diagram illustrating another further operation of a motor energy recycling device used in a DC motor control circuit; 
         FIG. 4A  is a circuit diagram of a motor energy recycling device used in a DC motor control circuit according to another preferred embodiment of the invention; 
         FIG. 4B  is a circuit diagram of a motor energy recycling device used in a three phase AC motor controller according to a further preferred embodiment of the invention; and 
         FIG. 4C  is a circuit diagram of a motor energy recycling device used in a three phase AC motor control circuit according to another further preferred embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 2  is a circuit diagram of a motor energy recycling device  2  according to a preferred embodiment of the invention. As shown in  FIG. 2 , the motor energy recycling device  2  is connected to a DC motor  91 , a voltage regulating power capacitor  10 , and a switch unit  11 . The motor energy recycling device  2  includes a first diode unit  21 , a first capacitor  22 , a first inductor  23 , a switching device  24 , a second capacitor  25 , a second diode unit  26 , and a second inductor  27 . The switching device  24  has a first end ‘a’, a second end ‘b’, and a third end ‘c’. 
     The voltage regulating power capacitor  10  provides a power required for the DC motor  91 . The switch unit  11  is provided to control the DC motor  91 , so that, when the switch unit  11  is open-circuited, the energy released by the DC motor  91  in running is used to continuously charge the first capacitor  22  for energy storage. The first capacitor  22  is connected to the DC motor  91  and the first diode unit  21 . Further, the first capacitor  22  is connected between the first inductor  23  and the second capacitor  25 . The first inductor  23  is connected to the first end ‘a’. The second capacitor  25  is connected to the third end ‘c’. The switching device  24  can be switched to make the third end ‘c’ connected with the first end ‘a’, or the third end ‘c’ connected with the second end ‘b’. The second end ‘b’ of the switching device  24  is connected between the second inductor  27  and the second diode  26 . The other end of the second inductor  27  is connected between the second capacitor  25  and the voltage regulating power capacitor  10 . The second diode unit  26  makes the second inductor  27  to charge the voltage regulating power capacitor  10  to thereby accomplish energy recycling. 
       FIGS. 3A to 3D  are schematic diagrams illustrating operations of the motor energy recycling device  2  used in a DC motor control circuit according to a preferred embodiment of the invention. As shown in  FIG. 3A , the DC motor  91  releases the excessive energy to thereby generate a current I 1  which charges the first capacitor  22 . The motor energy recycling device  2  preferably uses a control unit  28  to control the switching device  24 . The control unit  28  is connected to the first capacitor  22  and the switching device  24  in order to control the switching device  24  based on the voltage of the first capacitor  22 . When the voltage of the first capacitor  22  is over a predetermined voltage, the switching device  24  is switched at a switching frequency to alternately make a connection between the third end ‘c’ and the first end ‘a’ or between the third end ‘c’ and the second end ‘b’. In this case, the predetermined voltage can be, for example, 100V. Namely, when the first capacitor  22  has a voltage accumulated over 100V, the switching device  24  starts to work. 
     As shown in  FIG. 3B , when the third end ‘c’ is connected with the first end ‘a’, a second current I 2  is generated. Namely, the first capacitor  22  charges the second capacitor  25  through the first inductor  23  for energy storage. As shown in  FIG. 3C , when the third end ‘c’ is connected with the second end ‘b’, the energy stored in the second capacitor  25  generates a third current I 3  which charges the second inductor  27  for energy storage. As shown in  FIG. 3D , when the second inductor  27  is stored with energy, a fourth current I 4  is generated to charge the voltage regulating power capacitor  10  so as to accomplish energy recycling. 
     In this embodiment, for each switching the higher the switching frequency of the switching device  24 , the smaller the energy delivered from the first capacitor  22  to the second inductor  27 , so that the energy continuously recycled to the voltage regulating power capacitor  10  becomes more even, and thus the motor can be controlled more steadily. In addition, when the predetermined voltage is set to a high voltage, it causes the switching device  24  to start working at the high voltage, so as to achieve a higher recycling efficiency since the recycled energy consumed by the first diode  21  and the second diode  26  is reduced. 
       FIG. 4A  is a circuit diagram of a motor energy recycling device  2  used in a DC motor control circuit according to another preferred embodiment of the invention. This embodiment is symmetric with the previous embodiment. As shown in  FIG. 4A , similarly, the energy released by the DC motor  91  is stored in the first capacitor  22 , and the switching unit  24  is switched to make a connection between the third end ‘c’ and the first end ‘a’ or between the third end ‘c’ and the second end ‘b’ alternately. Thus, the energy is delivered through the second capacitor  25  from the first capacitor  22  to the second inductor  27 , and then the second inductor  27  charges the voltage-regulating power capacitor  10  to accomplish the energy recycling. 
     With reference to  FIGS. 4B and 4C ,  FIG. 4B  is a circuit diagram of the motor energy recycling device  2  used in a three phase AC motor control circuit, and  FIG. 4C  is a circuit diagram of the motor energy recycling device  2  used in a three phase AC motor control circuit. The circuit of  FIG. 4B  is symmetric with that of  FIG. 4C . As shown, the three phase AC motor has a first phase  921 , a second phase  922 , and a third phase  923 . The motor energy recycling device  2  is connected to the three phase AC motor, the voltage regulating power capacitor  10 , and a switch unit  11 . The switch unit  11  has six switches  111  respectively corresponding to current in/out of the first phase  921 , the second phase  922 , and the third phase  923 . The switch unit  11  configures the three phase AC motor into one-in/two-out mode or two-in/one-out mode to thereby form a loop of running the three phase AC motor. The first diode unit  21  of the recycling device  2  has six first diodes  211 . Each of the first phase  921 , second phase  922 , and third phase  923  of the three phase AC motor is connected to corresponding two switches  111  and two first diodes  211  to thereby control the running mode of the three phase AC motor. 
     In this embodiment, the energy released by the first phase  921 , second phase  922 , and third phase  923  of the three phase AC motor is stored in the first capacitor  22  through the corresponding first diodes  211 , respectively. Similar to the previous embodiments, the switching unit  24  is switched to make a connection between the third end ‘c’ and the first end ‘a’ or between the third end ‘c’ and the second end ‘b’ alternately. Thus, the energy is delivered through the second capacitor  25  from the first capacitor  22  to the second inductor  27 , and the second inductor  27  charges the voltage regulating power capacitor  10  to thereby accomplish the energy recycling. Therefore, the invention can effectively achieve the effect of recycling the energy released by the motor. 
     As cited, the motor energy recycling device is connected to the motor and the control circuit, such that the energy released by the motor can be stored in a first capacitor and energy transfer starts when the voltage of the first capacitor is accumulated to reach a predetermined voltage, for example, a voltage of 100V, which can be configured by the user. The larger the predetermined voltage value, the higher the recycling efficiency. 
     In addition, the motor energy recycling device makes use of an alternately switching unit at a frequency to thereby transfer the energy. The energy of the first capacitor is transferred first to the second capacitor and then to the second inductor, and finally the voltage regulating power capacitor is charged via the second inductor to thereby accomplish the energy recycling. The motor energy recycling device recycles the energy at a number of transfers each with a small amount of fixed energy, which only causes a small voltage change every time charging the voltage regulating power capacitor. Therefore, the operation and rotating speed of the motor are not affected, and the high safety is achieved. 
     Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.