Abstract:
A battery charging device suitable for a portable electronic device includes a rechargeable battery, a controlling chip, an adjusting transistor, a feedback circuit and a charger with adjustable output. The charger has an external alternating-current power source and provides a changeable voltage to the rechargeable battery of the portable electronic device. The feedback circuit captures a signal of electric quantities of the rechargeable battery and feeds back to the charger to adjust its output voltage and then the charger is controlled to charge the rechargeable battery. The adjustable transistor is used to control the charging of the rechargeable battery to reduce the number of parts of the battery charging device and waste of circuit traces.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a battery charging device, and more specifically, to a battery charging device, which controls a charger to charge a battery as the voltage of the battery changes. 
     2. Description of the Related Art 
     By the progress of electronic technology and widespread of electronic communication devices, portable electronic devices, such as notebook computer, PDA(Personal Digital Assistant) and digital cameras, etc., are commonly used. For easy to carry, these electronic devices are developed to become light, thin, short and small. Besides, lightweight and portable, easy to carry, and long time power supply are the requirements for users to choose which to buy. Because the power consumption of the portable electronic devices is pretty high, the battery needs to be charged so as to achieve a long time power supply. Recently, lithium-ion batteries are commonly used. Although light weight and large capacity, lithium-ion batteries do not have a memorizing characteristic. Lithium-ion batteries are continuously charged with a constant voltage. 
     Please refer to  FIG. 4 , showing a block diagram of a battery charging device of a conventional portable electronic device. The conventional charging device comprises a portable electronic device. The portable electronic device has a battery  30 , a charging unit (Charge IC)  31 , a programmable chip  32 , and a charger  4 . The charger  4  has an external alternating-current power source. 
     Please keep on referring to  FIG. 4 . The charging unit  31  is a switching direct-current to direct-current buck unit to supply charging current to the battery  30 . However, the programmable chip  32  records data and conditions required for charging the battery  30 . The data and conditions are all pre-set. For example, how much voltage and current are needed to charge, which conditions should be met then the battery  30  can be charged, and which power source should be cut off after the battery  30  is full-charged, etc. 
     When detecting the battery  30  is needed to charge, the programmable chip  32  will send signals to notify the charging unit  31  to charge the battery  30 . After that, the programmable chip  32  notifies the charging unit  31  to switch off the charging power source to stop charging. 
     Although the conventional battery charging device can use the method of detection and determination to control charging of the battery  30 , the conventional charging unit  31  cannot work independently, and therefore has to cooperate with the programmable chip  32  to operate such that the constitution components thereof are limited. This kind of assembly needs more components and thus does not have economic effects. Because the voltages between the initial and final stages of charging the battery  30  significantly differ, and the output voltage of the existing external charger is constant and unchangeable, the waste of circuit traces increases to cause instability of the devices and shorten the life. 
     SUMMARY OF THE INVENTION 
     The objective of the present invention is to provide a battery charging device, which captures signals of electric quantities of a battery by a feedback circuit and feedbacks to a charger to control the charger charging the battery. 
     The battery charging device for achieving above-mentioned objective comprises a rechargeable battery, a controlling chip, an adjusting transistor, a feedback circuit, and a charger with adjustable output. The controlling chip detects electric quantities of the rechargeable battery and feedbacks signals of the electric quantities by the feedback circuit to the charger with adjustable output to adjust its output voltage. The controlling chip controls the adjusting transistor to adjust the output voltage to charge the rechargeable battery. 
     The battery charging device is suitable for a portable electronic device. 
     The controlling chip is a programmable chip. 
     The adjusting transistor is a transistor or a field effect transistor. 
     The charger with adjustable output has an external alternating-current power source capable of modulating output voltage and output current of the charger. 
     The rechargeable battery, controlling chip, adjusting transistor, and feedback circuit can be packed to a battery packet type. 
     The output voltage is a little higher than a terminal voltage of the charging battery. 
     The charger with adjustable output responds to the signals of the electric quantities to modulate its output voltage. 
     Another objective of the present invention is to provide a charging method, which captures the signals of the electric quantities of a battery to feedback to a charger to control the charger charging the battery. 
     The charging method for achieving the above objectives comprises the following steps: 
     Using a controlling chip to detect the electric quantities of a rechargeable battery and determine whether the battery is needed to be charged; 
     Controlling a charger with adjustable output by the controlling chip through a feedback circuit; and 
     Providing an adjusted output by the charger with adjustable output according to the signals of the feedback circuit as a charging source of the rechargeable battery. 
     The controlling chip controls an adjusting transistor to adjust the output voltage of the charger to charge the charging battery. 
     The controlling chip controls the charger with adjustable output through the feedback circuit to directly charge the rechargeable battery with a constant voltage. 
     The controlling chip controls the charger with adjustable output through the feedback circuit to directly charge the rechargeable battery with a constant current. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a battery charging device in accordance with one embodiment of the present invention. 
         FIG. 2  is a block diagram of a battery charging device in accordance with another embodiment of the present invention. 
         FIG. 3  is a flow chart of a charging method of the present invention. 
         FIG. 4  is a block diagram of a conventional battery charging device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Please refer to  FIG. 1 , showing a block diagram of a battery charging device in accordance with one embodiment of the present invention. The battery charging device  100  of the present invention comprises a rechargeable battery  10 , a controlling chip  11 , an adjusting transistor  12 , a feedback circuit  13 , and a charger with adjustable output  2 , wherein the rechargeable battery  10 , controlling chip  11 , adjusting transistor  12 , and feedback circuit  13  are embodied in a portable electronic device  1 . 
     Please keep on referring to  FIG. 1 . The controlling chip  11  is a programmable chip. The controlling chip  11  is used to detect electric quantities of the rechargeable battery  10  and determine a status of the rechargeable battery  10 . The feedback circuit  13  transmits signals of the electric quantities detected by the controlling chip  11  to the charger with adjustable output  2 . The charger with adjustable output  2  has an external alternating-current power source, and the charger with adjustable output  2  provides an electric quantity to the rechargeable battery  10  of the portable electronic device  1 . The charger with adjustable output  2  adjusts its output voltage according to the signals of the electric quantities transmitted by the feedback circuit  13  to charge the rechargeable battery  10 . Besides, the adjusting transistor  12  is used to control the charger with adjustable output  2  to charge the rechargeable battery  10 , or switching off the adjusting transistor  12  to stop charging the rechargeable battery  10 . 
     The adjusting transistor  12  can be a transistor or a field effect transistor to control the charging voltage and current of the rechargeable battery  10 . 
     To charge the rechargeable battery  10  of the portable electronic device  1 , first the controlling chip  11  detects the electric quantities of the rechargeable battery  10  and determines whether the electric quantities of the rechargeable battery  10  are insufficient and needed to charge. The information of detection and determination is transferred to signals of electric quantities, and the feedback circuit  13  transmits the signals of the electric quantities to the charger with adjustable output  2 . The charger with adjustable output  2  adjusts its output voltage according to the signals of the electric quantities, meanwhile the controlling chip  11  controls the adjusting transistor  12  to adjust the output voltage so that the output voltage of the charger with adjustable output  2  is a little higher than the terminal voltage of the rechargeable battery  10 , i.e. about 0.3˜1V. At this time, the adjusting transistor  12  is in a state of conductance to control the charger with adjustable output for charging the rechargeable battery  10 . When the controlling chip  11  detects the electric quantities of the rechargeable battery  10  and determines the electric quantities of the rechargeable battery  10  is full-charged, the controlling chip  11  is used to control the adjusting transistor  12  in a state of un-conductance to stop the charger with adjustable output  2  from charging the rechargeable battery  10 . 
     The preferred embodiment of the present invention is embodied in a portable electronic device  1 . The rechargeable battery  10 , controlling chip  11 , adjusting transistor  12 , and feedback circuit  13  can be packed to a battery packet type and then assembled into the portable electronic device  1 , instead of building-in the portable electronic device  1  so that it can be mass-produced and suitable for any electronic devices. 
     Please refer to  FIG. 2 , showing a block diagram of the battery charging device of another embodiment of the present invention. The battery charging device  100  of the present invention comprises a rechargeable battery  10 , a controlling chip  14  with a constant voltage and current, a feedback circuit  13 , and a charger with adjustable output  2 , wherein the rechargeable battery  10 , controlling chip  14  with a constant voltage and current, and the feedback circuit  13  are embodied in a portable electronic device  1 . 
     Please keep on referring to  FIG. 2 . The controlling chip  14  with a constant voltage and current is used to detect the electric quantities needed by the rechargeable battery  10  and determine the status of the rechargeable battery  10 . The feedback circuit  13  converts the detected electric quantities and the status of the rechargeable battery  10  determined by the controlling chip  14  to signals that are transferred to the charger with adjustable output  2  by a signal transmission line. The charger with adjustable output  2  has an external alternating-current power source. The charger with adjustable output  2  provides an electric quantity to the rechargeable battery  10  of the portable electronic device  1 . The charger with adjustable output  2  adjusts the output voltage according to the signals of the electric quantities received to directly charge the rechargeable battery  10  with a constant voltage or current. 
     To charge the rechargeable battery  10  of the portable electronic device  1 , first the controlling chip  14  with a constant voltage and current is used to detect the electric quantities of the rechargeable battery  10  and determine whether the electric quantities of the rechargeable battery  10  are insufficient and needed to charge. The information of detection and determination is converted to signals, and the feedback circuit  13  is used to transmit the signals of the electric quantities to the charger with adjustable output  2 . The charger with adjustable output  2  adjusts its output voltage according to the signals of the electric quantities received to directly charge the rechargeable battery  10  with a constant voltage or current. When the controlling chip  14  with a constant voltage and current detects the electric quantities of the rechargeable battery  10  is full-charged, the controlling chip  14  with a constant voltage and current controls the charger with adjustable output  2  to stop charging the rechargeable battery  10 . 
     The preferred embodiment of the present invention is embodied in a portable electronic device  1 . The rechargeable battery  10 , controlling chip  14  with a constant voltage and current, and feedback circuit  13  can be packed to a battery packet type and then assembled into the portable electronic device  1 , instead of building-in the portable electronic device  1  so that it can be mass-produced and suitable for any electronic devices. 
     Please refer to  FIG. 3  accompanying with  FIG. 1 .  FIG. 3  shows a flow chart of the charging method of the present invention. The charging method of the present invention comprises the following steps: 
     a. detecting  200 : 
     The controlling chip  11  is used to detect the electric quantities of the rechargeable battery  10 . 
     b. determining  201 : 
     Meanwhile, the controlling chip  11  is used to determine whether the rechargeable battery  10  needs to be charged or is in a status of full-charged. 
     c. feedback  202 : 
     The feedback circuit  13  is used to transmit the signals of the electric quantities of the rechargeable battery  10  detected by the controlling chip  11  to the charger with adjustable output  2 . 
     d. controlling  203 : 
     The charger with adjustable output  2  adjusts the output voltage according to the signals of the electric quantities received. Meanwhile the controlling chip  11  controls the adjusting transistor  12  to adjust the output voltage so that the output voltage of the charger with adjustable output  2  is a little higher than the terminal voltage of the rechargeable battery  10 . 
     e. charging  204 : 
     According to the received feedback signals, the output voltage of the charger with adjustable output  2  is adjusted to charge the rechargeable battery  10 . 
     f. stop charging  205 : 
     According to the received feedback signals, the switch transistor  12  is switched off to stop charging the rechargeable battery  10 . 
     In this embodiment, the controlling chip  11  controls the charger with adjustable output  2  through the feedback circuit  13  to directly charge the rechargeable battery  10  with a constant voltage or current. 
     These embodiments are only used to illustrate the present invention, and are not intended to limit the scope thereof. Many modifications of the embodiments can be made without departing from the spirit of the present invention.