Abstract:
An electrical device is provided. The electrical device of this invention includes a voltage control circuit that couples with an AC-DC adapter and a charger. The voltage control circuit uses the charger to determine the condition of the battery and controls the AC-DC adapter to generate different output voltages by the conditions of the system loading and the battery. The electrical device can be used for portable equipment.

Description:
RELATED APPLICATIONS  
       [0001]     The present application is based on, and claims priority from, Taiwan Application Serial Number 94124405, filed Jul. 19, 2005, the disclosure of which is hereby incorporated by reference herein in its entirety.  
       BACKGROUND  
       [0002]     1. Field of Invention  
         [0003]     The present invention relates to an electric device. More particularly, the present invention relates to an electric device that can adjust the output voltage according to the loading conditions.  
         [0004]     2. Description of Related Art  
         [0005]     Portable devices, such as the digital camera, notebook computer, personal digital assistant (PDA), and cellular phone, have been developed so abundantly that they have become the dominant trend of electric products,. The battery, power adapter and DC-DC converter are the essential parts of these portable devices.  
         [0006]     The Buck DC-DC converter is 80% more efficient than the traditional linear converter. However, the DC-DC converter has lower efficiency under higher input voltage and has higher efficiency under lower input voltage.  
         [0007]      FIG. 1  is a functional block diagram of a traditional power supply system. The adapter  105  generates a fixed voltage for charging the circuit (charger)  130  to charge the battery  110 , and this fixed voltage also supplies the power for the system  115  via a first switch (SW 1 )  120  and couples of DC-DC converters. When the system  115  is not coupled with the adapter  105 , the second switch (SW 2 )  125  is conductive and the battery  110  supplies the power for the system  115 .  
         [0008]     Because the supply voltage has to be higher than the whole voltage of the battery set, the adapter  105  needs to output higher voltage when charging. However, if the adapter  105  always outputs higher and fixed voltage whether charging or not, it causes the adapter to be less efficient. Moreover, the charging time is just a fraction of the whole operation time for a notebook computer; thus the efficiency of adapter  105  is made even less efficient by outputting high voltage continuously.  
       SUMMARY  
       [0009]     It is therefore an objective of the present invention to provide an electric device for adjusting the voltage.  
         [0010]     It is therefore another objective of the present invention to provide an electric device for portable devices, such as notebook computers.  
         [0011]     It is therefore still another objective of the present invention to provide an electric device for outputting different voltages according to whether the system needs charging or not.  
         [0012]     It is still another objective of the present invention to provide an electric device of better efficiency without higher and fixed output voltage.  
         [0013]     In accordance with the foregoing and other objectives above, the present invention offers an electric device that includes a charging circuit, a voltage control circuit and an adapter. The charging circuit generates a signal according to the situation of DC-DC converters and the batteries. And the voltage control circuit transforms the signal from the charging circuit for inducing the adapter to adjust the output voltage. Therefore, the efficiency loss will thereby be reduced. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The invention can be more fully understood by reading the following detailed description of the preferred embodiments with reference made to the accompanying drawings as follows:  
         [0015]      FIG. 1  is a functional block diagram of a traditional power supply system;  
         [0016]      FIG. 2A  is a functional block diagram of the control circuit built on a motherboard according to one preferred embodiment of this invention;  
         [0017]      FIG. 2B  is a functional block diagram of the control circuit built in the adapter according to one preferred embodiment of this invention; and  
         [0018]      FIG. 3  is a circuit diagram of the control circuit according to one preferred embodiment of this invention; and  
         [0019]      FIG. 4  is a flow chart of the output voltage produced by the power supply system according to one preferred embodiment of this invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.  
         [0021]     The present invention is an electric device that includes a charging circuit, a voltage control circuit and an adapter.  FIG. 2A  is a functional block diagram of the control circuit built on a motherboard according to one preferred embodiment of this invention. This embodiment comprises a voltage control circuit  235 , an adapter  205  of this invention and a charging circuit  230 , wherein the voltage control circuit  235  is built on the motherboard  200 . The adapter  205  of this invention couples with the charging circuit  230 , and the charging circuit  230  couples with a battery  210 . Otherwise, the adapter  205  of this invention couples with the system  215  via the first switch  220  and the DC-DC converters  212 . The voltage control circuit  235  couples with the charging circuit  230  via the first signal line  231 , and the voltage control circuit  235  couples with the adapter  205  of this invention via voltage output line  206  and second signal line  207 .  
         [0022]     One function of the charging circuit  230  is to offer required electric power to the battery  210  during charging process. Another function of the charging circuit  230  is to generate the first signal through the first signal line  231  to the voltage control circuit  235  according to whether the battery  210  is charged or not. The function of the voltage control circuit  235  is to receive the first signal from the first signal line  231  and the charging circuit  230 . And the voltage control circuit  235  generates the second signal to the second signal line  207  and the adapter  205  of this invention. The function of the adapter  205  of this invention is to transform the AC input voltage to be DC input voltage and adjust the DC output voltage to be a first voltage (original voltage) or a second voltage according to the second signal of second signal line  207  from the voltage control circuit  235 .  
         [0023]     When the charging circuit  230  detects that the battery  210  does not need to be charged, the first switch  220  is conductive. Therefore, the adapter  205  of this invention supplies the power for the DC-DC converters  212  via the first switch  220 . When the charging circuit  230  detects that the battery  210  needs to be charged, the adapter  205  of this invention supplies the power for the battery  210  via the charging circuit  230 , and the adapter  205  of this invention supplies the power for the DC-DC converters  212  via the first switch  220 . Furthermore, when the DC-DC converters  212  do not couple with the power (the adapter  205  of this invention), the battery  210  supplies the power for the DC-DC converters  212  via the second switch  225 .  
         [0024]      FIG. 2B  is a functional block diagram of the control circuit built in the adapter according to one preferred embodiment of this invention. The only difference between  FIG. 2B  and  FIG. 2A  is that the voltage control circuit  235  is built in the adapter  205  of this invention; the other parts are the same.  
         [0025]      FIG. 3  is a circuit diagram of the control circuit according to one preferred embodiment of this invention. Please also refer to  FIG. 2A  and  FIG. 2B  simultaneously, in both of which the control circuit  235  appears. In this embodiment, the charging circuit  230  generates the first signal to the first signal line  231  to control the third switch  335 , and the third switch  335  couples with the voltage output line  206  of the adapter  205  of this invention. The second signal of the second signal line  207  feeds back to the adapter  205  of this invention, and the second signal of the second signal line  207  couples with an adjustable shunt regulator  330  via a diode  325 . The first capacitor  320  and the third resistor  315  are serially connected to be a compensation circuit.  
         [0026]     The combination of the first resistor  305 , the second resistor  310  and the adjustable shunt regulator  330  can be used to adjust the second signal of the second signal line  207  and further change the output voltage of the adapter  205  of this invention. The adjustable shunt regulator  330  is a control module, and the adjustable shunt regulator  330  can influence the output voltages of the adapter  205  of this invention by these following formulas:
 
 V   out=   V   ref ×[1+( R 1/ R 2)]
 
         [0027]     where  
         [0028]     V out  is the output voltage (second voltage) of the adapter  205  of this invention,  
         [0029]     V ref  is the individual parameter of the adjustable shunt regulator  330 ,  
         [0030]     R 1  is the resistance value of the first resistor  305 , and  
         [0031]     R 2  is the resistance value of the second resistor  310 .  
         [0032]     By the formulas described above, when the battery  210  needs to be charged, the charging circuit  230  does not generate the first signal of the first signal line  231 , and the third switch  335  is not conductive as in the original situation; thus the adapter  205  of this invention generates the first voltage (original voltage). When the battery  210  does not need to be charged, the charging circuit  230  generates the first signal of the first signal line  231 , and the third switch  335  is conductive. Therefore, the control circuit  235  generates the second signal of the second signal line  207  for the adapter  205  of this invention. Thus the adapter  205  of this invention generates the second voltage. And the second voltage can be adjusted by the resistance value of the first resistor  305  and the second resistor  310 .  
         [0033]      FIG. 4  is the flow chart of the output voltage produced by the power supply system according to one preferred embodiment of this invention (please refer to  FIG. 2  simultaneously). After starting (step  405 ), the charging circuit  230  ascertains whether the battery  210  is fully charged or not (step  410 ). If the battery  210  is fully charged, then the voltage control circuit  235  is initiated (step  415 ), and the adapter  205  of this invention outputs the second voltage (step  420 ). If the battery  210  is not fully charged, then the voltage control circuit  235  is terminated (step  425 ), and the adapter  205  of this invention outputs the first voltage (step  420 ). The charging circuit  230  always ascertains whether the battery  210  is fully charged or not during the step  410  to initiate or terminate the voltage control circuit  235 .  
         [0034]     The flowchart described above can reduce the voltage supplied for DC-DC converters when the battery does not need to be charged. By this method, the system efficiency is enhanced and the heat induced by the efficiency loss is reduced simultaneously.  
         [0035]     The combination of the control circuit  235  can be implemented by using any suitable and available technology, such as an OP comparator, a resistor voltage divider circuit, a voltage feedback circuit or a single-chip.  
         [0036]     Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiments contained herein.  
         [0037]     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.