Abstract:
An exemplary power source system includes a power source, controller, and a voltage fine adjusting unit. The power source includes a number of cells and a number of switches configured for connecting the cells in series or in parallel. The controller is configured for coarsely controlling an output of the power source by selectively turning on and off the switches. The voltage fine adjusting unit is configured for further and finely adjusting the output of the power source on condition that the coarsely controlled output of the power source is outside a predetermined acceptable range of output.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is related to a copending U.S. patent application Ser. No. 12/558,223 filed Sep. 11, 2009 (Attorney Docket No. US26177) and entitled “VARIABLE POWER SOURCE AND RELATED POWER SUPPLY METHOD,” and which has the same assignees as the present application. The disclosure of the above-identified application is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to power sources and, particularly, to a power source system capable of continuously adjusting an output thereof to meet the requirements of a variable load. 
         [0004]    2. Description of Related Art 
         [0005]    Current electric systems typically include a power source, a driving circuit, and a load. The load may consume different amounts of power at different times. In such case, the driving circuit is configured for altering an output of the power source to meet the requirements of the load. For example, the driving circuit may include an inverter for converting a direct current flowing out from the power source into an alternate current, and/or a transformer for adjusting an output voltage of the power source. In such an electric system, a great amount of power may be lost in the driving circuit itself when the driving circuit provides power for the load. Thus, the voltage provided to the load may be reduced, and accordingly the adjustment of the power provided to the load may not be precise. 
         [0006]    Therefore, it is desirable to provide a power source system which can overcome the above-mentioned problems. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a block diagram of a power source system of an exemplary embodiment of the present disclosure, together with a load. 
           [0008]      FIG. 2  is a schematic view of a power source of the power source system of  FIG. 1 , together with the load. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Referring to  FIG. 1 , a power source system  100 , according to an exemplary embodiment, is shown. The power source system  100  is configured for supplying power for a load  300 . The power source system  100  includes a power source  20 , a voltage fine adjusting unit  22 , and a controller  24 . The load  300  has a resistance R. The rated voltage and rated flow of electrical current of the load  300  are represented as V and I respectively. 
         [0010]    The power source  20  is configured for storing electric energy and providing electric energy to the load  300 . In particular, the power source  20  includes a number of cells  200 , a number of positive switches  202   b,  a number of negative switches  204   b,  a number of serializing switches  206   b,  a positive output  202   a,  and a negative output  204   a.  In this embodiment, the number of cells  200  is N, the number of positive switches  202   b  is N, the number of negative switches  204   b  is N, and the number of serializing switches  206   b  is N, wherein N is a natural number. 
         [0011]    The cells  200  can be dry batteries, rechargeable batteries or solar batteries. Each of the cells  200  includes a positive electrode  200   a  and a negative electrode  200   b.  An electromotive force ε of the cells  200  is typically fixed. 
         [0012]    The positive switches  202   b,  the negative switches  204   b,  and the serializing switches  206   b  can be, among other types, push-button switches, thin film switches, toggle switches, mercury tilt switches, lever switches, micro switches, or travel switches. In this embodiment, all the positive switches  202   b,  the negative switches  204   b,  and the serializing switches  206   b  are integrated into a grammed switch. 
         [0013]    In assembly, the cells  200  are arranged in parallel. Each of the positive switches  202   b  connects a positive electrode  200   a  of a corresponding cell  200  to the positive output  202   a.  Each of the negative switches  204   b  connects a negative electrode  200   b  of a corresponding cell  200  to the negative output  204   a.  Each of the serializing switches  206   b  connects a negative electrode  200   b  of a corresponding cell  200  to a positive electrode  200   a  of an adjacent cell  200 . 
         [0014]    The controller  24  is configured for controlling the output of the power source  20  by selectively turning on and turning off the positive switches  202   b,  the negative switches  204   b,  and the serializing switches  206   b.  The controller  24  includes a setting unit  240 , a detecting unit  242 , and an adjusting unit  244 . 
         [0015]    The setting unit  240  is configured for selectively turning on and turning off the positive switches  202   b,  the negative switches  204   b,  and the serializing switches  206   b  to control an output voltage of the power source  20  before starting supplying power to the load  300 . In particular, a serializing number N 1  and a parallelizing number N 2  are calculated by the setting unit  240  using, for example, the following two formulas: (1): N 1 =[V/ε]; and (2): N 2 =[IR/ε−N]; wherein [V/ε] represents rounding off V/ε, and [IR/ε−N] represents rounding off (IR/ε−N). In the present embodiment, unless the context indicates otherwise, rounding off means simplifying a number with a decimal point to the nearest integer. In more detail, the setting unit  240  stores the electromotive force ε and the total number N of the cells  200 . As such, once the resistance R, the rated voltage V, and the rated flow of electrical current I of the load  300  are inputted to the setting unit  240 , the serializing number N 1  and the parallelizing number N 2  can be determined by the setting unit  240 . Furthermore, the setting unit  240  can control the positive switches  202   b,  the negative switches  204   b,  and the serializing switches  206   b  by controlling the grammed switch to connect N 1 +1 of the cells  200  in series between the positive output  202   a  and the negative output  204   a  by switching on N 1  of the serializing switches  206   b,  and, except for the N+1 serialized cells  200 , by controlling the grammed switch to connect N 2  of the cells  200  in parallel between the positive output  202   a  and the negative output  204   a  by switching on N 2  of the positive switches  202   b  and N 2  of the negative switches  204   b  of the N 2  cells. 
         [0016]    It should be understood that (N 1 +N 2 +1) should be less than N. Otherwise, the power source  20  cannot supply power for the load  300 . Based upon the formula (1), it can be determined that a theoretical output voltage V OT  of the power source  2000  is about (N 1 +1)ε, which is, in theory, equal to or slightly higher than the rated voltage V of the load  300 . Based upon both the formulas (1) and (2), it can be inferred that a theoretical flow of electrical current I OT  through the load  300  is about (N 1 +N 2 +1)ε/R , which is, in theory, equal to or slightly higher than the rated flow of electrical current I of the load  300 . Thus the setting unit  240  is able to control the grammed switch such that both the rated voltage V and the rated flow of electrical current I of the load  300  can be satisfied. However, due to incremental exhausting of electric power of the cells  200  and incremental increasing of internal resistances of the cells  200 , a real output voltage V OR  and a real flow of electrical current I OR  tend to deviate from the theoretical output voltage V OT  and the theoretical flow of electrical current I OR , respectively. Therefore, the detecting unit  242  and the adjusting unit  244  are employed to reduce or eliminate any such deviation. 
         [0017]    The detecting unit  242  is configured for continuously measuring differences between the real output voltage V OR  and the rated voltage V of the load  300 , and differences between the real flow of electrical current I OR  and the rated flow of electrical current I of the load  300 . 
         [0018]    The adjusting unit  244  is configured for continuously adjusting the output voltage V OR  and the real flow of electrical current I OR  by adjusting on/off states of the positive switches  202   b,  the negative switches  204   b,  and the serializing switches  206   b,  based upon the differences measured by the detecting unit  242 . 
         [0019]    As such, the real output voltage V OR  can be coarsely maintained around the rated voltage V of the load  300 . The real flow of electrical current I OR  can be coarsely maintained around the rated flow of electrical current I of the load  300 . This is because each of the real output voltage V OR  and the real flow of electrical current I OR  can only be adjusted incrementally (each increment is ε and ε/R, respectively). Therefore, the real output voltage V OR  and the real flow of electrical current I OR  may need further fine adjustments to exactly meet the requirements of the load  300 . 
         [0020]    The voltage fine adjusting unit  22  is configured for precisely adjusting the real output voltage V OR  and the real flow of electrical current I OR . In particular, the voltage fine adjusting unit  22  includes a judging sub-unit  220  and a precise transformer  222 . The judging sub-unit  220  judges whether differences between the real output voltage V OR  and the rated voltage of the load  300  are within acceptable levels, and whether differences between the real flow of electrical current I OR  and the rated flow of electrical current of the load  300  are within acceptable levels. If the determination is “yes” for both judgments (i.e., both within acceptable levels), the judging unit  220  directly passes the output of the power source  20  to the load  300 . If the determination is “no” for either or both judgments (i.e., either or both not within acceptable levels), the judging unit  220  passes the output of the power source  20  to the precise transformer  222  for precise voltage adjustment, so that the output of the precise transformer  222  exactly meets the requirements of the load  300 . 
         [0021]    While various exemplary and preferred embodiments have been described, it is to be understood that the disclosure is not limited thereto. To the contrary, various modifications and similar arrangements (as would be apparent to those skilled in the art) are intended to also be covered. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.