Abstract:
A power supply device disposed in an electronic device having a main power supply includes a voltage converting unit for converting the voltage from the main power supply, a power controlling unit for controlling the current from the converting unit, and a USB interface unit for providing the electric power from the main power supply to peripheral units.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a power supply device that supplies electric power to peripheral units of an electronic device while the main power is switched off.  
       BACKGROUND OF THE INVENTION  
       [0002]     A conventional electronic device, especially for those having multiple functions in one unit generally includes a main power supply that provides electric power to the parts so as to maintain functional operation of these parts. Once the main power supply is shut down, all the power for the interfaces is shout down. This does not meet the requirement for some device that needs power supplied to the peripheral units while the main power is switched off.  
         [0003]     Therefore, it is desired to have a power supply device that provides power to the peripheral units while the main power is shut down.  
       SUMMARY OF THE INVENTION  
       [0004]     In accordance with an aspect of the present invention, there is provided a power supply device connected to an electronic device having a main power supply. The power supply device comprises a voltage-converting unit for converting a voltage output from the main power supply of the electronic device according to a converting command so as to generate a voltage status. A power-controlling unit controls an output from the voltage-converting unit to be a status of power supply by a control command when the electronic device is shut down. A USB (Universal Serial Bus) interface unit is connected to a peripheral unit and outputs electric power from the main power supply to the peripheral unit based on the status of the power supply.  
         [0005]     The present invention will become more obvious from the following description when taken in connection with the accompanying drawings, which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  shows an arrangement of a power supply device, a main power supply and peripheral units in accordance with the present invention;  
         [0007]      FIG. 2  shows a block diagram of the power supply device of the present invention;  
         [0008]      FIG. 3  shows another embodiment of the power supply device of the present invention; and  
         [0009]      FIG. 4  shows the display on a liquid crystal display panel of the power supply device of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0010]     Referring to  FIG. 1 , a power supply device  16  of the present invention is used for an electronic device  10 , such as a personal computer and a laptop computer. When the electronic device  10  is in a shutdown status, the power supply device  14  provides electric power to peripheral units  12  such as mobile phones, PDAs (Personal Digital Assistants), or CD player, from the main power supply  16 . The main power supply device  16  can be an AC/DC converter, an AC battery or both.  
         [0011]     Referring to  FIG. 2 , the power supply device  14  comprises a voltage-converting unit  20 , a power-controlling unit  22 , a UBS (Universal Serial Bus) interfaces unit  24 , a voltage converter  30 , a switch  29 , and a power output indicator  26 . The voltage-converting unit  20  converts the voltage from the main power supply  16  of the electronic device  10  according to a converting command so as to generate a voltage status that is output from the power supply device  14 . The power controlling unit  22  controls the output from the voltage-converting unit  20  to be a status of power supply by a control command when the electronic device  10  is shut down. The USB interface unit  24  is connected to a peripheral unit  12  and outputs the electric power from the main power supply  16  to the peripheral unit  12  based on the status of the power supply as mentioned above. The voltage converter  30  gives a command to the voltage-converting unit  20  and affects the voltage status. The command from the voltage converter  30  is designed for the user to decide the voltage that is converted from the power received by the electronic device  10  via the voltage converter  30 . The switch  29  is used to submit commands to the power-controlling unit  22 . The power output indicator  26  indicates the status of the power via the USB interface unit  24  based on the status of supply and the voltage status.  
         [0012]     The power controlling unit  22  makes the electronic device  10  supplied the electric power from the main power supply  16  by diodes, power MOS or transistors. Nevertheless, if the user submits the control command to let the function of the power controlling unit  22  fail by operating the switch  29 , no power is supplied from the main power supply  16  after the electronic device  10  is shut down. Therefore, the switch  29  provides an option for the user to decide whether or not the power is output from the USB interface unit when the electronic device  10  is shut down.  
         [0013]     The power supply device of the present invention allows the user to optionally get electric power from the main power supply  16  while the electronic device  10  is shut down.  
         [0014]     In order to inform the user whether or not the power-controlling unit  22  is in function by operating the switch  29 , the light-emitting diode (LED)  28  on the power output indicator  26  shows the status. When the LED  28  of the power output indicator  26  lights up, it means that the peripheral units  12  are supplied with power via the USB interface unit  24  while the electronic device  10  is shut down. On the other hand, if the LED  28  of the power output indicator  26  does not light up, it means that the peripheral units  12  are not supplied with power via the USB interface unit  24  while the electronic device  10  is shut down.  
         [0015]     Referring to  FIG. 3 , which shows another embodiment of the present invention, wherein the a liquid crystal display (LCD) panel  32  is replaced with the LED  28  as shown in  FIG. 2 .  
         [0016]      FIG. 4  shows the LCD panel that displays words that are the proper way to show the status of supply and voltage. In  FIG. 4 , “POWER ON” shows the status of supply and the voltage status is shown by “5V”.  
         [0017]     While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.