Abstract:
In a pulse width modulation (PWM) control device and driving method, the PWM control device includes a PWM device, for providing a plurality of PWM signals; and a controller electrically connected to the PWM device and a plurality of driving circuits, for controlling PWM signals to arbitrarily enable or disable the plurality of driving circuits according to load capacity; wherein when driving circuits are damaged, the controller disables the damaged driving circuits and replaces the damaged driving circuits with the other driving circuits.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to a control device and, more particularly, to a pulse width modulation (PWM) control device. 
         [0003]    2. Description of the Related Art 
         [0004]      FIG. 1  shows a structure of a conventional PWM control circuit. The PWM control circuit comprises a PWM device  110 , driving circuits  132  and  134 . Generally speaking, when changing the total output phase number, the PWM device  110  (or PWM integrated circuit) will increase or decrease the total output phase number gradually. In addition, the PWM device  110  will select some of the phases as output phases according to a fixed sequence. When the load capacity is heavy, most of the driving circuits will output current to the load  160 ; when the load capacity is light, only some of the driving circuits will be selected to output current, and the selected driving circuits is predetermined. Thus, those predetermined driving circuits will always output current to the load  160 . For example, when outputting PWM signals of four phases, the control device  110  only can change to output PWM signals of three phases and then change to output PWM signals of two phases; when outputting PWM signals of two phases, the control device  110  only can change to output PWM signals of three phases and then change to output PWM signals of four phases. When the control device  110  determines to output PWM signals of two phases, the phases  1  and  2  will be selected as the output phases; when the control device  110  determines to output PWM signals of three phases, the phase  1  through phase  3  will be selected as the output phases. In addition, when the control device  110  determines to output PWM signals of four phases, the phase  1  through phase  4  will be selected as the output phases. Thus, no matter the load capacity is heavy or light, the phases  1  and  2  will always be utilized. In other words, the driving circuits  132  and  134  corresponding to the phases  1  and  2  will always output current to the load  160 . Thus, the failure rate of the driving circuits  132  and  134  will be higher than that of the driving circuits corresponding to the phases  3  and  4  (not shown). Further, when one of the driving circuits is damaged, the PWM device  110  only can enable the driving circuits which precede the damaged driving circuit. For example, when the driving circuit corresponding to the phase  3  or the driving circuit corresponding to the phase  4  is damaged, the PWM device  110  only can enable the driving circuits corresponding to the phases  1  through  2  or the driving circuits corresponding to the phases  1  through  3 . Thus, the failure rate of the enabled driving circuits will also be increased. 
         [0005]    Therefore, a PWM control device which can change the selecting sequence of the output phases is needed. 
       BRIEF SUMMARY 
       [0006]    The present invention relates to a PWM control device. The PWM control device comprises a PWM device for providing a plurality of PWM signals; and a controller electrically connected to the PWM device and a plurality of driving circuits, for controlling PWM signals to arbitrarily enable or disable the plurality of driving circuits according to the load capacity. When one of the driving circuits is damaged, the control device disables the damaged driving circuit and replaces the damaged driving circuit with another driving circuit selected at random. 
         [0007]    The present invention relates to a driving method for a PWM control device. The driving method comprises: determining a maximum number of the utilized driving circuits; determining a utilized number of the driving circuits according to the maximum number and a load current; and enabling or disabling a predetermined number of the driving circuits according to the utilized number. 
         [0008]    From the aforementioned PWM control device and the driving method thereof, it can be understood that the total output phase number will be properly selected according to the load capacity, and the output phases will be selected at random so that the utilization rate of each driving circuit will approach to each other. Therefore, the utilization rate of the driving circuits will be equalized, and the service life of the driving circuits will also be prolonged. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
           [0010]      FIG. 1  shows a structure of a conventional PWM control circuit. 
           [0011]      FIG. 2  shows a structure of a PWM control device in accordance with an embodiment of the present invention. 
           [0012]      FIG. 3  shows a structure of a PWM control device in accordance with another embodiment of the present invention. 
           [0013]      FIG. 4  is a flow chart of a driving method for a PWM control device in accordance with an embodiment of the present invention. 
           [0014]      FIG. 5  shows the relationship between the PWM phase number and the load current. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Reference will now be made to the drawings to describe exemplary embodiments of the present invention, in detail. The following description is given by way of example, and not limitation. 
         [0016]      FIG. 2  shows a structure of a PWM control device in accordance with an embodiment of the present invention. The PWM control device comprises a PWM device  210  and a controller  220 . 
         [0017]    The PWM device  210  may be a chip, an integrated circuit (IC) or a microprocessor for providing multi-phase PWM signals. The controller  220  is electrically connected to the PWM device  210  and a plurality of driving circuits for receiving PWM signals from the PWM device  210 . After operating and processing the received PWM signals, the controller  220  respectively transmits the processed PWM signals to the first driving circuit  232 , the second driving circuit  234  and the third driving circuit  236 , etc. Thus, the control intention of the present invention is achieved. The controller  220  may also be a chip, an integrated circuit or a microprocessor. 
         [0018]    In this embodiment, the controller  220  can select the driving circuits at random, and can arbitrarily enable or disable the selected driving circuits. Assuming that the PWM control device shown in the  FIG. 2  has six phases, when the load capacity is heavy so that four driving circuits need to be enabled to output current to the load  260 , the PWM device  210  will output the PWM signals of the phases  1  through  4  to the controller  220 , and the controller  220  may arbitrarily enable the driving circuits corresponding to the phases  1  through  4  or phases  3  through  6  after operating and processing the received PWM signals. On the contrary, when the load capacity is light, the PWM device  210  will select two of the phases as the output phases according to the load current and a maximum phase number, i.e. 6. In other words, only two driving circuits will be enabled when the load capacity is light. At the same time, the controller  220  may arbitrarily enable the driving circuits corresponding to the phases  1  through  2  or phases  3  and  6 . Although the controller  220  enables the driving circuits arbitrarily, the spirit of that is to enable all driving circuits equally, so that none of the driving circuits will always output current. 
         [0019]    In addition, when one of the enabled driving circuits is damaged, the controller  220  will disable the damaged driving circuit and replace the damaged driving circuit with another driving circuit selected at random. Furthermore, when one of the enabled driving circuits is damaged, the controller  220  will not enable the damaged driving circuit again. For example, assuming that the driving circuits corresponding to the phases  1 ,  2  and  5  are enabled, the controller  220  will disable the driving circuit corresponding to the phase  5  when it is damaged, and the controller  220  may enable the driving circuit corresponding to the phase  6  or phase  3  to substitute for the damaged driving circuit. 
         [0020]      FIG. 3  shows a structure of a PWM control device in accordance with another embodiment of the present invention. In this embodiment, the controller  312  is integrated into the PWM device  310 . The function and the operation of the PWM control device shown in the  FIG. 3  are similar to that of the PWM control device shown in the  FIG. 2 . Therefore, no more description is needed. 
         [0021]      FIG. 4  is a flow chart of a driving method for a PWM control device in accordance with an embodiment of the present invention. In the step  402 , a maximum phase number is determined. The user could select a PWM device according to real needs, so as to determine the maximum phase number. For example, the user could select a PWM chip having 6 phases or a PWM chip having 4 phases. The phase number of the selected PWM chip represents the maximum number which the driving circuits can be enabled by the selected PWM chip. In the step  404 , a utilized phase number is determined. The CPU will control the output phase number of the PWM device according to the load current. As shown in the table of the  FIG. 5 , assuming that the PWM control device has 6 phases, the output phase number will be changed from 5 to 6 or from 6 to 5 when the load current achieves 56-64 A; the output phase number will be changed form 4 to 5 or from 5 to 4 when the load current is about 36-44A. Therefore, the number of the PWM signals transmitted to the controller and the number of the enabled driving circuits will be changed correspondingly. In the step  406 , the driving circuits are enabled arbitrarily according to the utilized phase number. For example, when the utilized phase number is 4, the controller will receive the PWM signals of four phases. After operating and processing the received PWM signals, the controller will arbitrarily enable four driving circuits. Afterward, in the step  408 , the controller detects the enabled driving circuits and determines whether there exists any damaged driving circuit. If the result is negative, the PWM control device returns to the step  404 ; if the result is positive, the PWM control device performs the steps  410  and  412 . When one of the enabled driving circuits is damaged, the controller will disable the damaged driving circuit and replace the damaged driving circuit with another driving circuit selected at random, so as to keep the output power to enable the load works normally. 
         [0022]    The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including configurations ways of the recessed portions and materials and/or designs of the attaching structures. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.