Abstract:
A charge circuit for charging a battery includes a converter and a timer. The converter converts alternating current (AC) of an AC power supply into direct current (DC) and outputs a DC voltage to the battery through a first resistor. The timer is used to set a period of time and stop charging the battery after the set period of time.

Description:
FIELD 
       [0001]    The present disclosure relates to a charge circuit. 
       BACKGROUND 
       [0002]    Typically, a charge circuit will continue charging a battery even when the battery is full. That can damage the battery. 
         [0003]    Therefore, there is room for improvement in the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0004]    Many aspects of the present disclosure can be better understood with reference to the following drawing. The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawing, like reference numerals designate corresponding parts throughout the several views. 
           [0005]    The FIGURE is a circuit diagram of an embodiment of a charge circuit of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0006]    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.” The reference “a plurality of” means “at least two.” 
         [0007]    The FIGURE shows an embodiment of a charge circuit  10  of the present disclosure. 
         [0008]    The charge circuit  10  comprises a converter  20  and a timer  30 . 
         [0009]    The converter  20  comprises a voltage transformer T 1 , a bridge rectification circuit Z 1 , resistors R 1 -R 3 , a capacitor C 1 , a diode D 1 , and a light emitting diode (LED) D 2 . The converter  20  is connected with an alternating current (AC) power supply and converts AC into direct current (DC) for an electronic device, such as a battery B 1 . A first input terminal of the voltage transformer T 1  is connected to a fire terminal L of a live wire of the AC power supply. A second input terminal of the voltage transformer T 1  is connected to a zero terminal N of a neutral wire of the AC power supply. The bridge rectification circuit Z 1  comprises diodes D 4 -D 7 . A cathode of the diode D 4  is connected to an anode of the diode D 5 . A node between the cathode of the diode D 4  and the anode of the diode D 5  is connected to a first output terminal of the voltage transformer T 1 . An anode of the diode D 4  is connected to an anode of the diode D 6 . A node between the anode of the diode D 4  and the anode of the diode D 6  is grounded. A cathode of the diode D 5  is connected to a cathode of the diode D 7 . A node between the cathode of the diode D 5  and the cathode of the diode D 7  is grounded through the capacitor C 1 . A cathode of the diode D 6  is connected to an anode of the diode D 7 . A node between the cathode of the diode D 6  and the anode of the diode D 7  is connected to a second output terminal of the voltage transformer T 1 . The node between the cathode of the diode D 5  and the cathode of the diode D 7  is connected to an anode of the diode D 1  through the resistor R 1 . A cathode of the diode D 1  is connected to an anode of the battery B 1 . A cathode of the battery B 1  is grounded through the resistor R 3 . The LED D 2  and the resistor R 3  are connected in parallel. An anode of the LED D 2  is connected to the cathode of the battery B 1 . A cathode of the LED D 2  is grounded. 
         [0010]    The timer  30  comprises an operational amplifier U 1 , electronic switches Q 1 -Q 3 , switches S 1 -S 3 , resistors R 4 -R 9 , a capacitor C 2 , a diode D 3 , and a relay. The relay comprises a coil L 1  and a dynamic type break contact K 1 . The dynamic type break contact K 1  is connected between the fire terminal of the AC power supply and the first terminal of the voltage transformer T 1 . A non-inverting input of the operational amplifier U 1  is connected to the cathode of the diode D 1 . An inverting input of the operational amplifier U 1  is connected to the anode of the battery B 1 . An output of the operational amplifier U 1  is connected to a first terminal of the electronic switch Q 1 . A second terminal of the electronic switch Q 1  is connected to a first terminal of the electronic switch Q 2  through the resistor R 5 . The second terminal of the electronic switch Q 1  is connected to the node between the cathode of the diode D 5  and the cathode of the diode D 7  through the resistor R 4 . A second terminal of the electronic switch Q 2  is connected to the node between the cathode of the diode D 5  and the cathode of the diode D 7 . A third terminal of the electronic switch Q 2  is connected to first terminals of the switches S 1 -S 3 . Second terminals of the switches S 1 -S 3  are connected to a first terminal of the capacitor C 2  through the resistors R 6 -R 8 , respectively. A second terminal of the capacitor C 2  is grounded. The first terminal of the capacitor C 2  is connected to a first terminal of the electronic switch Q 3  through the resistor R 9 . A second terminal of the electronic switch Q 3  is connected to the node between the cathode of the diode D 5  and the cathode of the diode D 7  through the coil L 1 . The coil L 1  and the diode D 3  are connected in parallel. An anode of the diode D 3  is connected to the second terminal of the electronic switch Q 3 . A cathode of the diode D 3  is connected to the node between the cathode of the diode D 5  and the cathode of the diode D 7 . A third terminal of the electronic switch Q 3  is grounded. 
         [0011]    The bridge rectification circuit Z 1  outputs a DC voltage through the node between the cathode of the diode D 5  and the cathode of the diode D 7 . The DC voltage charges the battery B 1 . The operational amplifier U 1  amplifies a voltage across the resistor R 2  and outputs a voltage of high level to the first terminal of the electronic switch Q 1 . The electronic switch Q 1  is turned on. Thus, the first terminal of the electronic switch Q 2  is at low level. The electronic switch Q 2  is turned on, turning on at least one of the switches S 1 -S 3 , and the DC voltage charges the capacitor C 2 . When a voltage of the first terminal of the capacitor C 2  increases to a value enough to turn on the electronic switch Q 3 , a voltage is across the coil L 1  and the dynamic type break contact K 1  is off, the first terminal of the voltage transformer T 1  is disconnected from the fire terminal of the AC power supply, the charge circuit stops charging the battery B 1 . In the embodiment, resistances of the resistors R 6 -R 8  are different from each other. Thus, the time required for the voltage of the first terminal of the capacitor C 2  to increase to a value high enough to turn on the electronic switch Q 3  are different from each other when selectively turning on one of the switches S 1 -S 3 . 
         [0012]    In the embodiment shown in the FIGURE, the electronic switch Q 1  and Q 3  are npn Bipolar Junction Transistors (BJTs). The electronic switch Q 2  is a pnp BJT. The first terminals of the electronic switches Q 1 -Q 3  are bases of the BJTs. The second terminals of the electronic switches Q 1 -Q 3  are collectors of the BJTs. The third terminals of the electronic switches Q 1 -Q 3  are emitters of the BJTs. 
         [0013]    While the disclosure has been described by way of example and in terms of preferred embodiment, it is to be understood that the disclosure is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the appended claims should be construed to encompass all such modifications and similar arrangements.