Charger control circuit with automatic polarity selection
An exemplary charger control circuit includes an input port having a positive terminal and a negative terminal, an electrode control circuit, and an output port having a positive terminal and a negative terminal. The input port is connected to a source of power. The output port is connected to a load. The electrode switching circuit detects the electrode polarity of the input port and the output port for selectively coupling the positive terminals and the negative terminals of the two ports, and protecting the electrical equipment.
1. 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.
2. The charger control circuit as claimed in claim 1 , further comprising a diode, an anode of the diode is connected to the third switch lead, a cathode of the diode is connected to said one terminal of the output port.
3. The charger control circuit as claimed in claim 1 , wherein the first and second transistors are NPN transistors.
4. A charger control circuit comprising:
an input port with two terminals connected to a DC power supply;
an output port with a positive terminal and a negative terminal connected to corresponding terminals of an input port of a battery charger for providing direct current; and
a polarity detecting circuit coupled between the input port and the output port for detecting the polarity of the terminals of the input port to transmit direct current from the input port to the output port in a proper polarity, 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 two terminals of the input port, the third switch lead is connected to the positive terminal of the output port, the fourth switch lead is connected to the negative 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 the first switch lead of the switch element of the relay-switch and the corresponding terminal of the input port, and an emitter of the second transistor is grounded.
5. The charger control circuit as claimed in claim 4 , further comprising a diode, an anode of the diode is connected to the third switch lead, a cathode of the diode is connected to the positive terminal of the output port.
6. The charger control circuit as claimed in claim 4 , wherein the first and second transistors are NPN transistors.
7. A charger control circuit comprising:
an input port having a positive terminal and a negative terminal;
an output port having a positive terminal and a negative terminal; and
a polarity detecting circuit coupled between the input port and the output port, the polarity detecting circuit comprising first and second input terminals respectively connected to the positive and negative terminals of the input port, first and second output terminals respectively connected to the positive and negative terminals of the output port, and a control circuit connected to one of the input port and the output port to detect the polarity of the terminals of the one of the input port and the output port to control the first and second input terminals respectively connecting with the first and second output terminals in a proper polarity;
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 one of the positive terminals of the input and output ports, and an emitter of the second transistor is grounded.
8. The charger control circuit as claimed in claim 7 , wherein the first and second transistors are NPN transistors.