Abstract:
A power control system includes a voltage control circuit and a plurality of balance circuits. The voltage control circuit controls a voltage level at an output of the power control system according to a reference voltage. Each of the plurality of balancing circuits outputs a current, whose magnitude is a specific ratio to an output current outputted from the voltage control circuit. The power control system is capable of balancing output currents of the voltage control circuit and the plurality of balance circuits in order to share output load of the power control system.

Description:
BACKGROUND OF THE INVENTION  
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a power control system, and more particularly, to a power control system capable of balancing output currents. 
         [0003]    2. Description of the Prior Art 
         [0004]    Among electronic products, magnitudes of input voltages required for circuits and blocks are not entirely the same. Therefore, a circuit system of an electronic product has to include a power circuit capable of modulating output voltage. In prior art, power circuits utilized for modulating output voltages are roughly classified into two types including switching circuits and linear power circuits, the linear power circuits are also denoted as linear voltage step-down circuits. 
         [0005]    High transformation efficiency is a benefit of switching circuits, however, high design complexity and high costs are also drawbacks to switching circuits. The circuit design of a linear power circuit is simple, but has the drawback of low efficiency. The low efficiency of linear power circuits results from the fact that elements of linear power circuits consume redundant power in the form of heat. While the linear power circuits output higher power, the elements of linear power circuits may break down because of being overheated. Moreover, equipping the elements of linear power circuits with radiators not only increases costs, but also occupies additional space in the electronic products. 
         [0006]    For overcoming the defect that the elements of linear power circuits become overheated, a solution is provided in the prior art. The solution includes parallel connecting or serially connecting multiple elements in linear power circuits for sharing output power respectively and lowering quantities of heat generated from each element. The multiple elements may be power resistors and power diodes. However, there may be slight differences between the multiple elements, causing it to be difficult to precisely control the power shared by each element. 
       SUMMARY OF THE INVENTION  
       [0007]    The claimed invention provides a power control system capable of balancing output currents. The power control system comprises a first voltage control circuit and a second voltage control circuit. 
         [0008]    The first voltage control circuit comprises a first current control switch, a first current sensing unit, and a first comparison circuit. The first current control switch is coupled to a predetermined voltage source for outputting a first loading current according to the predetermined voltage source. The first current sensing unit is coupled to an output of the power control system and to the first current control switch for sensing a magnitude of the first loading current. The first comparison circuit has a first input for receiving a reference voltage, and a second input coupled to the output of the power control system. The first comparison circuit is utilized for comparing the reference voltage and voltage outputted at the output of the power control system for controlling the magnitude of the first loading current. 
         [0009]    The second voltage control circuit comprises a second current control switch, a second current sensing unit, and a second comparison circuit. The second current control switch is coupled to the predetermined voltage source for outputting a second loading current according to the predetermined voltage source. The second current sensing unit is coupled to the output of the power control system and to the second current control switch for sensing a magnitude of the second loading current. The second comparison circuit has a first input coupled to the first current sensing unit, and a second input coupled to the second current sensing unit. The second comparison circuit is utilized for controlling the magnitude of the second loading current according to the magnitudes of the first loading current and the second loading current. 
         [0010]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0011]      FIG. 1  is a block diagram of a power control system of the present invention. 
           [0012]      FIG. 2  is a diagram of a preferred embodiment of the power control system shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION  
       [0013]    Please refer to  FIG. 1 , which is a block diagram of a power control system  100  according to an embodiment of the present invention. The power control system  100  comprises a voltage control circuit  110  and a plurality of balancing circuits  120 . The voltage control circuit  110  comprises a current control switch  112 , a current sensing unit  114 , and a comparison circuit  116 . A first input “a” of the comparison circuit  116  is utilized for receiving a reference voltage V ref , and a second input “b” of the comparison circuit  116  is coupled to an output “out” of the power control system  100 . 
         [0014]    The comparison circuit  116  is utilized for comparing the reference voltage V ref  with voltage V out  outputted at an output “out” of the power control system  100  and for outputting a control voltage V c1  according to result of the comparison. The current control switch  112  is coupled to a predetermined voltage source V s  for outputting a loading current i 1 . The magnitude of the loading current i 1  outputted by the current control switch  112  depends on the control voltage V c1  outputted by the comparison circuit  116 . The current sensing unit  114  is coupled to the output “out” of the power control system  100  and to the current control switch  112  for sensing the magnitude of the loading current i 1  outputted by the current control switch  112 . 
         [0015]    Each balancing circuit  120  comprises a current control switch  122 , a current sensing unit  124 , and a comparison circuit  126 . The current control switches  122  are coupled to the predetermined voltage source V s  for respectively outputting loading currents i 2  and i 3 . The magnitudes of the loading currents i 2  and i 3  outputted by the current control switches  122  depend on control voltages V c2  and V c3  outputted by the comparison circuits  126 . The current sensing units  124  are coupled to the output “out” of the power control system  100  and to the current control switches  122  for sensing the magnitudes of the loading currents i 2  and i 3  outputted by the current control switches  122 . The first inputs “a” of the comparison circuits  126  are coupled to the current sensing unit  114  of the voltage control circuit  110 , and the second inputs “b” of the comparison circuits  126  are coupled to the current sensing units  124 . Therefore, the comparison circuit  126  of each balancing circuit  120  is utilized for outputting a control voltage, which is respectively the control voltage V c2  or V c3  as shown in  FIG. 1 , according to the comparison result of comparing the loading current i 1  sensed by the current sensing unit  114  of the voltage control circuit  110  with the loading current, which is the loading current i 2  or i 3  as shown in  FIG. 1 , sensed by the current sensing unit  124  of the corresponding balancing circuit  120 . 
         [0016]    In other words, the voltage control circuit  110  is utilized for controlling the magnitude of the voltage V out  outputted at the output “out” of the power control system  100  according to the reference voltage V ref . Each balancing circuit  120  is utilized for outputting a predetermined current having a specific scale, for example currents having equivalent magnitudes, from the plurality of balancing circuits  120 , according to the magnitude of the loading current i 1  outputted by the voltage control circuit  110 . Therefore, the power control system  100  is capable of outputting substantially equal currents for balancing the power shared by the voltage control circuit  110  and the plurality of balancing circuits  120 . 
         [0017]    Please refer to  FIG. 2  in addition to  FIG. 1 .  FIG. 2  is a diagram of a preferred embodiment of the power control system  100  shown in  FIG. 1 , i.e., a power control system  200 . In  FIG. 2 , the power control system  200  comprises current control switches  112  and  122 , current sensing units  114  and  124 , and comparison circuits  116  and  126 . The current control switches  112  and  122  may be metal-oxide semiconductor field effect transistors. The current sensing units  114  and  124  may be resistors. The comparison circuits  116  and  126  may be operational amplifiers. However, the elements of the power control system  200  mentioned above may be replaced with other elements or other circuits having the same functions. 
         [0018]    For example, the current sensing units  114  and  124  may also be conductors having higher resistances. The comparison circuits  116  and  126  may also be integrated circuits of other types. The comparison circuit  116 , which is an operational amplifier as shown in  FIG. 2 , is utilized for outputting the control voltage V c1  after comparing the reference voltage V ref  and the voltage V out  outputted at the output “out” of the power control system  100 . When the voltage V out  does not equal the reference voltage V ref , the control voltage V c1  outputted by the operation amplifier implementing the comparison circuit  116  continuously modulates the loading current i 1  outputted by the metal-oxide semiconductor field effect transistor implementing the current control switch  112  until the voltage V out  equals the reference voltage V ref . Since the magnitude of the voltage V out  and the resistances of the resistors implementing the current sensing units  114  and  124  are known, the magnitudes of the loading currents i 1 , i 2 , i 3  outputted by the metal-oxide semiconductor field effect transistors implementing the current control switches  112  and  122  can be generated by merely measuring the voltages at a first terminal “A” of the resistors implementing the current sensing units  114  and  124  as shown in  FIG. 2 . 
         [0019]    The operation amplifiers implementing the comparison circuits  126  of balancing circuits  120  output the control voltages V c2  and V c3  after the magnitude of the voltage at the first terminal “A” of the resistor implementing the current sensing unit  114  is compared with the magnitude of the voltage at the first terminal “A” of the resistor implementing the current sensing unit  124 , i.e., after comparing the magnitudes of the loading currents i 1 , i 2 , and i 3  as shown in  FIG. 2 . When the voltage at the first terminal “A” of the resistor implementing the current sensing unit  124  does not equal the voltage at the first terminal “A” of the resistor implementing the current sensing unit  114 , the control voltages V c2  and V c3  continuously modulate the magnitudes of the loading currents i 2  and i 3  outputted by the metal-oxide semiconductor field effect transistors implementing the current control switches  122  until the voltage at the first terminal “A” of the resistor implementing the current sensing unit  1324  equals the voltage at the first terminal “A” of the resistor implementing the current sensing unit  114 . 
         [0020]    In other words, when the resistance of the resistor implementing the current sensing unit  114  of the voltage control circuit  110  equals the resistance of the resistors implementing the current sensing units  124  of the balancing circuits  120 , the operational amplifiers implementing the comparison circuits  126  of the balancing circuits  120  control the metal-oxide semiconductor field effect transistors implementing the current control switches  122  so that the loading currents i 2  and i 3  outputted by the balancing circuits  120  are equal to the loading current i 1  outputted by the voltage control circuit  110 . However, the resistances of the resistors implementing the current sensing units  114  and  124  may also be modified so that the loading currents i 2  and i 3  are equal to a predetermined percentage of the loading current i 1  outputted by the voltage control circuit  110 . 
         [0021]    In summary, the embodiment of the present invention provides a power control system  100  for precisely controlling the power shared by the voltage control circuit  110  and the balancing circuits  120 . Therefore, the power control system  100  can output with a higher power while outputting a predetermined output voltage. Additionally, although two power balancing circuits  120  are shown in  FIG. 1  and  FIG. 2 , the embodiment of the present invention may be practiced using any number of power balancing circuits  120  without departing from the spirit of the invention. 
         [0022]    Compared with the prior arts, the power control system  100  of the embodiment of present invention has simpler circuits and lower costs. Moreover, the power control system of the present invention can precisely control the magnitudes of the loading circuits outputted by the voltage control circuit and the balancing circuits for balancing the power shared by the voltage control circuit and the balancing circuits, and for solving the prior art defect that the elements are overheated because of a higher power. 
         [0023]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.