Battery protective circuit
A battery protective circuit includes a battery controller, a charging control transistor, and a protection circuit. The battery controller controls charging of a battery according to a charging control voltage output through a charging control terminal. The a charging control transistor electrically connects the battery to a charger or to electrically disconnect the battery from the charger. The protection circuit includes a voltage sensing terminal electrically connected to a load, an input terminal electrically connected to the charging control terminal, and an output terminal electrically connected to a gate terminal of the charging control transistor. The protection circuit outputs a signal through the output terminal to turn off the charging control transistor, regardless of the charging control voltage of the input terminal, when a voltage equal to or greater than a threshold voltage is sensed at the voltage sensing terminal.
1. A battery protective circuit, comprising:
a battery controller including a charging control terminal, the battery controller to control charging of a battery according to a charging control voltage output through the charging control terminal;
a charging control transistor to electrically connect the battery to a charger or to electrically disconnect the battery from the charger;
a switch between the battery and a load, wherein the battery is electrically connected to the load when the switch is turned on and the battery is electrically disconnected from the load when the switch is turned off; and
a short circuit preventing circuit including a voltage sensing terminal electrically connected to the load, an input terminal electrically connected to the charging control terminal, and an output terminal electrically connected to a gate terminal of the charging control transistor, the short circuit preventing circuit to output a signal through the output terminal to turn off the charging control transistor when the switch is turned on.
2. The circuit as claimed in claim 1 , further comprising:
a discharging control transistor to electrically connect the battery to the load or to electrically disconnect the battery from the load, wherein the discharging control transistor includes a gate terminal electrically connected to a discharging control terminal of the battery controller, a first end electrically connected to the battery, and a second end electrically connected to a first end of the charging control transistor and the load.
3. The circuit as claimed in claim 2 , wherein the short circuit preventing circuit includes:
a first transistor including a first end electrically connected to the input terminal and a second end electrically connected to the output terminal;
a second transistor including a first end electrically connected to the input terminal and a second end electrically connected to a gate terminal of the first transistor; and
a third transistor including a first end electrically connected to a gate terminal of the second transistor, a second end electrically connected to a reference voltage, and a gate terminal electrically connected to the voltage sensing terminal.
4. The circuit as claimed in claim 2 , wherein:
a positive terminal of the battery, a first end of the switch, and a positive terminal of the charger are electrically connected to each other,
a second end of the switch, a positive terminal of the load, and the voltage sensing terminal are electrically connected to each other,
a negative terminal of the battery and a first end of the discharging control transistor are electrically connected to each other,
a second end of the discharging control transistor, a first end of the charging control transistor, and a negative terminal of the load are electrically connected to each other, and
a second end of the charging control transistor and a negative terminal of the charger are electrically connected to each other.
5. The circuit as claimed in claim 4 , wherein the charging control transistor is to be turned off when the charging control voltage is at a low-level.
6. The circuit as claimed in claim 3 , wherein:
the first and second transistors are of a first conductivity type, and
the third transistor is of a second conductivity type different from the first conductivity type.
7. The circuit as claimed in claim 6 , wherein:
the first transistor is a PMOS transistor,
the second transistor is a PMOS transistor, and
the third transistor is an NMOS transistor.
8. The circuit as claimed in claim 6 , wherein the short circuit preventing circuit includes a zener diode including a cathode electrically connected to the input terminal and an anode electrically connected to the reference voltage.
9. The circuit as claimed in claim 3 , wherein the short circuit preventing circuit includes a zener diode including a cathode electrically connected to the input terminal and an anode electrically connected to the reference voltage.
10. An apparatus, comprising:
a circuit;
a first terminal;
a second terminal; and
a third terminal to be connected to a load,
wherein the circuit is to output a signal through the second terminal to turn off a charging control transistor for a battery when the third terminal is connected to the load, and
wherein the circuit includes:
a first transistor electrically connected to the first and second terminals;
a second transistor electrically connected to the first terminal and a gate terminal of the first transistor; and
a third transistor electrically connected to the second transistor and the third terminal.
11. The apparatus as claimed in claim 10 , wherein:
a gate of the first transistor is connected to the second transistor,
a gate of the second transistor is connected to the third transistor, and
a gate of the third transistor is connected to the third terminal.
12. The apparatus as claimed in claim 11 , wherein:
the first and second transistors are of a first conductivity type, and
the third transistor is of a second conductivity type different from the first conductivity type.
13. The apparatus as claimed in claim 11 , further comprising:
a zener diode electrically connected to the first terminal and a reference voltage, wherein the third transistor is connected to the reference voltage.
14. An apparatus, comprising:
a circuit;
a first terminal;
a second terminal; and
a third terminal to be connected to a load,
wherein the circuit is to output a signal through the second terminal to turn off a charging control transistor for a battery, the circuit including
a first transistor electrically connected to the first and second terminals;
a second transistor electrically connected to the first terminal and a gate terminal of the first transistor; and
a third transistor electrically connected to the second transistor and the third terminal, wherein:
a gate of the first transistor is connected to the second transistor,
a gate of the second transistor is connected to the third transistor,
a gate of the third transistor is connected to the third terminal,
the first and second transistors are of a first conductivity type, and
the third transistor is of a second conductivity type different from the first conductivity type.