Abstract:
The present invention discloses a charger circuit. The charger circuit comprises a control circuit and at least two charging paths. The control circuit determines to activate or inactivate each charging path according to a battery feedback signal representing the charging status. Accordingly, the battery is charged by input power in an optimal way so that the charging efficiency is improved and the overheating problem is solved.

Description:
CROSS REFERENCE 
     The present invention claims priority to TW 099221755, filed on Nov. 10, 2010. 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to a charger circuit, in particular to such charger circuit which includes at least two charging paths. 
     2. Description of Related Art 
       FIG. 1  shows a schematic diagram of a prior art charger circuit. As shown in  FIG. 1 , input power supplies a battery with a charging current, charging the battery through the charging path  11  of a charger circuit  10 . A control circuit  12  obtains a battery feedback signal related to a battery charging status from the battery, and controls the charging path  11  accordingly such that when the battery charging status reaches a predetermined threshold, the charging path  11  is inactivated to finish the charging operation. 
     This conventional charger circuit charges the battery only by one charging path  11 . In many applications, the charging path  11 , the control circuit  12 , and other circuits are integrated into an integrated circuit. Such conventional charger circuit is limited by the over temperature protection mechanism of the circuit; that is, the battery cannot be charged with a large current. Therefore, the charging time is long, and the charging efficiency is poor. Furthermore, due to heat dissipation issue of the charging path  11 , the efficiency of the charging circuit  10  is further degraded. 
     In view of above, the present invention overcomes the foregoing defects by putting forth a charger circuit including at least two charging paths. The charger circuit can optimally select and adjust the charging paths according to the charging status and the environment temperature so as to improve the efficiency of the charger circuit and the issue of the over temperature protection, while it does not need a complicated the current design. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a charger circuit. 
     To achieve the foregoing objective, the present invention provides a charger circuit, comprising: a first charging path receiving input power, the first charging path being controlled by a first control signal to charge a battery with a first charging current; at least one second charging path receiving the input power, the second charging path being controlled by a second control signal to charge the battery with a second charging current; and a control circuit coupled to the first charging path and the second charging path, the control circuit receiving a battery feedback signal and outputting the first control signal and the second control signal according to the battery feedback signal. 
     In the foregoing charger circuit, the first path and the control circuit are preferably integrated into an integrated circuit, and the second charging path is outside the integrated circuit. 
     In one embodiment, the battery feedback signal is related to a charging status of the battery, and when the battery feedback signal reaches a predetermined value, the control circuit stops generating the second control signal so that the second charging path stops charging the battery. 
     In one embodiment, the foregoing charger circuit further comprises a temperature detection circuit coupled to the control circuit, the temperature detection circuit generating an over temperature detection signal as an input to the control circuit when an environment temperature detected by the temperature detection circuit is over a predetermined temperature threshold, wherein the control circuit determines whether or not to generate the first control signal and the second control signal according to the over temperature detection signal. 
     The objectives, technical details, features, and effects of the present invention will be better understood with regard to the detailed description of the embodiments below, with reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic diagram of a prior art charger circuit. 
         FIG. 2  shows an embodiment of the present invention. 
         FIG. 3  shows another embodiment of the present invention. 
         FIG. 4  shows another embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 2 , it shows an embodiment of the present invention. The object to be charged is not limited to the DC battery as shown for example, but may be various other electrical energy storage devices. As shown in this figure, input power supplies a battery with a charging current for charging the battery through the first charging path  21  and the second charging path  22  of a charger circuit  20 . A control circuit  23  obtains a battery feedback signal (which may be, for example but not limited to, the voltage or the divided voltage of the battery) related to a battery charging status from the battery, and controls the first charging path  21  and the second charging path  22  accordingly. In one embodiment, the charging paths are controlled as thus. When the battery voltage is below a first predetermined threshold, the control circuit  23  generates a first control signal and a second control signal, activating both the first charging path  21  and the second charging path  22  to charge the battery with a large current. When the battery voltage is above the first predetermined threshold, the control circuit  23  stops generating the second control signal, inactivating the second charging path  22  so that only the first charging path  21  charges the battery. When the battery voltage is above a second predetermined threshold which is higher than the first predetermined threshold, the control circuit  23  stops generating the first control signal, inactivating the first charging path  21 , and the charging operation is finished. 
     The above arrangement has the advantages that: first, the charging time is shortened because the battery is charged by a large current at an early stage; second, the battery charging status can be finely controlled because it is charged by a small current at a later stage. Furthermore, the second charging path  22  can be disposed outside the integrated circuit for better heat dissipation. When the battery is charged with a large current, because of the better heat dissipation conditions, the charging operation is less limited by the overheat protection in the circuit. Accordingly, the charging efficiency is further upgraded. 
     The control circuit  23  not only can activate or inactivate each charging path, but also can control the current amount of each path so that the charging operation can be more precisely controlled. 
     Referring to  FIG. 3 , it shows another embodiment of the present invention. As shown in this figure, the charger circuit  20  further comprises a temperature detection circuit  24  coupled to the control circuit  23 . When the temperature detection circuit  24  detects that the environment temperature is above a predetermined temperature threshold, it generates an over temperature detection signal as the input of the control circuit  23 . The control circuit  23  determines whether or not to generate the foregoing first control signal and the foregoing second control signal according to the over temperature detection signal. 
     Referring to  FIG. 4 , it shows another embodiment of the present invention. As shown in this figure, the charger circuit  20  comprises a plurality of second charging paths  22  to provide the control circuit  23  with more selectable and controllable paths. For example, when the battery voltage is low, the control circuit  23  can activate all of the charging paths so that the charging time is shortened. Or, according to the battery charging status, the environment temperature, the over temperature setting and so on, the control circuit  23  can inactivate some of the paths and adjusts the currents on the activated charging paths. The above can be achieved by, for example, controlling a controlled terminal of a power transistor (not shown) on the charging paths. 
     The present invention has been described in considerable detail with reference to certain preferred embodiments thereof. It should be understood that the description is for illustrative purpose, not for limiting the scope of the present invention. Those skilled in this art can readily conceive variations and modifications within the spirit of the present invention. For example, in all of the embodiments, a device or circuit which does not affect the major functions of the signals, such as a switch, etc., can be added between two circuits illustrated to be directly connected with each other. For another example, the second charging path  22  can be disposed inside the integrated circuit. Thus, the present invention should cover all such and other modifications and variations, which should be interpreted to fall within the scope of the following claims and their equivalents.