Abstract:
A charging circuit includes a DC (Direct Current) power source, a rechargeable battery, and a switch circuit. The DC power source includes positive and negative output terminals, and the switch circuit is connected to and located between the DC power source and the rechargeable battery. The switch circuit comprises an arrangement of transistors and other components which permits the connection of the battery in any manner, and the normal charging or recharging of the battery notwithstanding the polarity of the battery terminals.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a charging circuit capable of safely charging a rechargeable battery. 
         [0003]    2. Description of Related Art 
         [0004]    A typical charging circuit includes a power charger and a rechargeable battery. The power charger includes an alternative current (AC) power plug and a direct current (DC) output port having positive and negative terminals. The AC power plug is used to electrically connect to an AC power source for receiving the AC power. 
         [0005]    The power charger can convert the AC power to DC power which is output from the output port to the chargeable battery. The positive terminal of the rechargeable battery is connected to the positive terminal of the power charger. The negative terminal of the rechargeable battery is connected to the negative terminal of the power charger. Then the chargeable battery can be charged by the power charger. However, if the positive and negative terminals of the rechargeable battery are incorrectly connected, the power charger can not charge the rechargeable battery and may even damage the rechargeable battery. 
         [0006]    Therefore, there is room for improvement within the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  is a block diagram of a charging circuit according to an embodiment. 
           [0009]      FIG. 2  is a detailed circuit of the charging circuit of  FIG. 1 , showing a rechargeable battery connected to a DC power source in a first manner. 
           [0010]      FIG. 3  is similar to  FIG. 2 , but showing the rechargeable battery connected to the power charger in a second manner. 
           [0011]      FIG. 4  is a block diagram of a power charger according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The disclosure is illustrated by way of example and not by way of limitation. In the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
         [0013]    Referring to  FIG. 1 , an embodiment of a charging circuit includes a power converter  10  and a switch circuit  20  connected to the power converter  10 . The charging circuit can recharge a rechargeable battery  30 . The power converter  10  comprises a positive output terminal and a negative output terminal. The switch circuit  20  comprises a first input terminal A connected to the negative output terminal and a second input terminal B connected to the positive output terminal. The switch circuit  20  comprises a first output terminal C and a second output terminal D. The rechargeable battery  30  comprises a positive input terminal and a negative input terminal. The first output terminal C is connected to one of the positive and negative input terminals. The second output terminal D is connected to the other one of the positive and negative input terminals. In one embodiment, the power converter  10  connects to an AC power source and converts the AC power source to DC power source which is supplied to the rechargeable battery  30  via the positive and negative output terminals. 
         [0014]    Referring to  FIG. 2 , the switch circuit  20  includes a first transistor Q 1 , a second transistor Q 2 , a third transistor Q 3 , a fourth transistor Q 4 , and resistors R 1 ˜R 4 . The first transistor Q 1  and the third transistor Q 3  are both NPN type bipolar transistors. The second transistor Q 2  and the fourth transistor Q 4  are both PNP type bipolar transistors. The first transistor Q 1  comprises a first base terminal, a first collector terminal, and a first emitting terminal. The first base terminal is connected to the first output terminal C via the resistor R 1 . The first collector terminal is connected to the second output terminal D. The first emitter terminal is connected to the negative output terminal. The second transistor Q 2  comprises a second base terminal, a second collector terminal, and a second emitting terminal. The second base terminal is connected to the second output terminal D via the resistor R 2 . The second collector terminal is connected to the first output terminal C. The second emitter terminal is connected to the positive output terminal. The third transistor Q 3  comprises a third base terminal, a third collector terminal, and a third emitting terminal. The third base terminal is connected to the second output terminal D via the resistor R 3 . The third collector terminal is connected to the first output terminal C. The third emitter terminal is connected to the negative output terminal. The fourth transistor Q 4  comprises a fourth base terminal, a fourth collector terminal, and a fourth emitting terminal. The fourth base terminal is connected to the first output terminal C via the resistor R 4 . The fourth collector terminal is connected to the second output terminal D. The fourth emitter terminal is connected to the positive output terminal. 
         [0015]    When the rechargeable battery  30  are connected to the output terminals C and D in a first manner as shown in  FIG. 2 , the first base terminal is at a high level, thereby rendering the first transistor Q 1  conductive. The second base terminal is at a low level, thereby rendering the second transistor Q 2  conductive. The third base terminal is at a low level, thereby rendering the third transistor Q 3  non-conductive. The fourth base terminal is at a high level, thereby rendering the fourth transistor Q 4  non-conductive. The positive input terminal is connected to the positive output terminal via the conductive second transistor Q 2 . The negative input terminal is connected to the negative output terminal via the conductive first transistor Q 1 . Thus current from the positive output terminal can flow to the positive input terminal, and return to the negative output terminal via the negative input terminal. In such a manner, the rechargeable battery  30  can be recharged normally. 
         [0016]    Referring to  FIG. 3 , when the rechargeable battery  30  are connected to the output terminals D and C in a second manner as shown in  FIG. 3 , the third base terminal is at a high level, thereby rendering the third transistor Q 3  conductive. The fourth base terminal is at low level, thereby rendering the fourth transistor Q 4  conductive. The first base terminal is at a low level, thereby rendering the first transistor Q 1  non-conductive. The second base terminal is at high level, thereby rendering the second transistor Q 2  non-conductive. The positive input terminal is connected to the positive output terminal via the conductive fourth transistor Q 4 . The negative input terminal is connected to the negative output terminal via the conductive third transistor Q 3 . The rechargeable battery  30  can also be normally recharged when the rechargeable battery  30  is connected to the power converter  10  in the second manner. Thus, the rechargeable battery  30  will be recharged notwithstanding a disorientation of the terminals of the battery  30 . 
         [0017]    In one embodiment, the first transistor Q 1  and the second transistor Q 2  belong to a first group of switches. The third transistor Q 3  and the fourth transistor Q 4  belong to a second group of switches. When the rechargeable battery  30  is connected to the DC power source  10  in the first manner, the first group of switches is switched on to connect the rechargeable battery  30  correctly to the power converter  10 . When the rechargeable battery  30  is connected to the DC power source  10  in the second manner (the disoriented manner), the second group of switches switches on to connect the rechargeable battery  30  correctly to the power converter  10 . Therefore, the rechargeable battery  30  can be charged safely in either manner. 
         [0018]    In one embodiment, the power converter  10  and the switch circuit  20  are contained in a power charger  40 . The power charger  40  includes an AC power plug  42  for receiving power from the AC power source. Such a power charger  40  can charge the rechargeable battery  30  normally notwithstanding the manner of connection of the terminals of the rechargeable battery  30  to the DC power source&#39;s output terminals. 
         [0019]    While the present disclosure has been illustrated by the description of preferred embodiments thereof, and while the preferred embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such details. Additional advantages and modifications within the spirit and scope of the present disclosure will readily appear to those skilled in the art. Therefore, the present disclosure is not limited to the specific details and illustrative examples shown and described.