Patent ID: 8912763

Claim:
A charger device, to convert alternating current power supplied by an alternating current power supply into suitable direct current power to charge a battery, the charger device comprising: a switch having a first end connected to the alternating current power supply; a voltage converter connected to a second end of the switch, the voltage converter converting the alternating current power into first direct current power, the voltage converter comprising an output; a constant current circuit, connected between the output of the voltage converter and a positive pole of the battery, the constant current circuit supplying constant charging current power to the battery; and an automatic disconnecting circuit, connected to the switch, the battery, the voltage converter and the constant current circuit, the automatically disconnecting circuit automatically disconnecting the voltage converter from the alternating current power supply when the battery is fully charged, the automatic disconnecting circuit comprising; a first resistor having a first end connected to the positive pole of the battery; a voltage follower, with a non-inverting input connected to a second end of the first resistor and an inverting input connected to an output of the voltage follower; a second resistor having a first end connected to the output of the voltage converter; a first zenor diode, comprising a cathode connected to a second end of the second resistor and an anode grounded; a variable resistor, comprising a first terminal connected to the cathode of the first zenor diode, a second terminal grounded, and a slider; a comparator, comprising a non-inverting input connected to the slider of the variable resistor, and an inverting input connected to the output of the voltage follower, and an output; a third resistor having a first end connected to the output of the comparator; a first switch element, comprising a first pole connected to the output of the voltage converter, a control pole connected to a second end of the third resistor, and a second pole; a diode, comprising a cathode connected to the second pole of the first switch element and an anode grounded; and a relay, comprising a coil connected between the second pole of the first switch element and the ground, and a normally-open switch connected between the alternating current power supply and the voltage converter, wherein the normally-open switch turns on or off according to the first switch element to control a connection between the charger device and the alternating current power supply.