Patent ID: 7592781

Claim:
A charger control circuit comprising: an input port having a positive terminal and a negative terminal connected to corresponding terminals of an output port of a battery charger for receiving direct current; the output port having two terminals connected to a rechargeable battery; and a polarity detecting circuit coupled between the input port and the output port of the charger control circuit for detecting the polarity of the terminals of the output port of the charger control circuit to provide direct current of the proper polarity to the output port of the charger control circuit, wherein the polarity detecting circuit comprises a relay-switch with a switch element having a first switch lead and a second switch lead defined on one side thereof, and a third switch lead and a fourth switch lead defined on another side thereof for selectively connecting to the first and the second switch leads, and a relay element having two relay leads, and a control circuit connected to the relay leads to thereby selectively short the switch leads of the relay-switch for providing direct current to the rechargeable battery, wherein the first and second switch leads are respectively connected to the positive terminal and negative terminal of the input port, the third switch lead is connected to one terminal of the output port, the fourth switch lead is connected to another terminal of the output port; wherein the control circuit comprises a first transistor, a second transistor, and a photocoupler with a luminous element and an optical receiving block, and wherein an anode of the optical receiving block is coupled to a power source via the relay element of the relay-switch, and a cathode of the optical receiving block is grounded, an anode of the luminous element is coupled to an emitter of the first transistor, a cathode of the luminous element is grounded, a collector of the first transistor is connected to the power source, a base of the first transistor is connected to a collector of the second transistor, a collector of the second transistor is connected to the power source, a base of the second transistor is coupled to a node between a diode and the corresponding terminal of the output port, and an emitter of the second transistor is grounded.