Power supply control apparatus including highly-reliable overcurrent detecting circuit

• US 20050013079A1
• Filed: 07/07/2004
• Published: 01/20/2005
• Est. Priority Date: 07/16/2003
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Mitsuda, Tsuyoshi
• Granted Patent: US 7,626,792 B2
• Time in Patent Office: Days
• US Class Current: 361/100
• CPC Class Codes: H02H 3/087 for dc applications

Abstract

In a power supply control apparatus for controlling supplying of power from a battery to a load including a battery terminal connectable to the battery, an output terminal connectable to the load, and a ground terminal, a transistor is connected between the battery terminal and the output terminal to turn ON and OFF a connection between the battery and the load. An overcurrent detecting circuit is connected between the battery terminal and the output terminal to detect whether or not an overcurrent has flown through the transistor. A control circuit is connected between the battery terminal and the ground terminal to activate the transistor and the overcurrent detecting circuit.

Claims

1. A power supply control apparatus for controlling supplying of power from a battery to a load, comprising:

a battery terminal connectable to said battery;

an output terminal connectable to said load;

a ground terminal;

a first transistor, connected between said battery terminal and said output terminal, for turning ON and OFF a connection between said battery and said load;

an overcurrent detecting circuit, connected between said battery terminal and said output terminal, for detecting whether or not an overcurrent has flown through said first transistor; and

a control circuit, connected between said battery terminal and said ground terminal, for activating said first transistor and said overcurrent detecting circuit.

2. The power supply control apparatus as set forth in claim 1, wherein said overcurrent detecting circuit comprises:

a second transistor having a first end connected to said battery terminal and a second end and activated by said control circuit, said second transistor being analogeous to said first transistor;

a reference resistor having a first end connected to the second end of said second transistor and a second end connected to said output terminal;

a first constant current source having a first end connected to said battery terminal and a second end;

a second constant current source having a first end connected to said battery terminal and a second end;

a third transistor having a first end connected to the second end of said first constant current source and a second end connected to the first end of said reference resistor; and

a fourth transistor having a first end connected to the second end of said second constant current source and a second end connected to said output terminal,

said third and fourth transistors being analogeous to each other and being controlled by a voltage at the first end of said third transistor,

the first end of said fourth transistor generating an overcurrent detecting signal and transmitting it to said control circuit.

3. The power supply control apparatus as set forth in claim 1, wherein said overcurrent detecting circuit comprises:

a second transistor having a first end connected to said battery terminal and a second end and activated by said control circuit, said second transistor being analogeous to said first transistor;

a reference resistor having a first end connected to the second end of said second transistor and a second end connected to said output terminal;

a constant current source having a first end connected to said battery terminal and a second end; and

a third transistor having a first end connected to the second end of said constant current source and a second end connected to said output terminal, and being controlled by a voltage at the first end of said reference resistor,

the first end of said third transistor generating an overcurrent detecting signal and transmitting it to said control circuit.

4. The power supply control apparatus as set forth in claim 1, wherein said overcurrent detecting circuit comprises:

a second transistor having a first end connected to said battery terminal and a second end and activated by said control circuit, said second transistor being analogeous to said first transistor;

a reference resistor having a first end connected to the second end of said second transistor and a second end connected to said output terminal;

a first resistor having a first end connected to said battery terminal and a second end;

a second resistor having a first end connected to said battery terminal and a second end;

a third transistor having a first end connected to the second end of said first resistor and a second end connected to the first end of said reference resistor;

a fourth transistor having a first end connected to the second end of said second resistor and a second end connected to said output terminal, said third and fourth transistors being analogeous to each other and being controlled by a voltage at the first end of said third transistor; and

a comparator, connected to the first end of said fourth transistor, for comparing a voltage at the first end of said fourth transistor with a reference voltage to generate an overcurrent detecting signal and transmit it to said control circuit.

5. The power supply control apparatus as set forth in claim 1, wherein said overcurrent detecting circuit comprises:

a second transistor having a first end connected to said battery terminal and a second end and activated by said control circuit, said second transistor being analogeous to said first transistor;

a reference resistor having a first end connected to the second end of said second transistor and a second end connected to said output terminal;

a resistor having a first end connected to said battery terminal and a second end;

a third transistor having a first end connected to said resistor and a second end connected to said output terminal and being controlled by a voltage at the first end of said reference resistor; and

a comparator, connected to the first end of said third transistor, for comparing a voltage at the first end of said third transistor with a reference voltage to generate an overcurrent detecting signal and transmit it to said control circuit.

6. The power supply control apparatus as set forth in claim 1, wherein said control circuit comprises:

a logic circuit for generating a clock signal;

a charge pump circuit, connected to said logic circuit, for receiving said clock signal to activate said first transistor and said overcurrent detecting circuit.

7. An overcurrent detecting circuit device comprising:

a battery terminal connectable to a battery;

an output terminal connectable to a load;

a first transistor, having a first end connected to said battery terminal and a second end, for detecting whether or not an overcurrent has flown to said output terminal;

a reference resistor having a first end connected to the second end of said first transistor and a second end of said output terminal;

a first constant current source having a first end connected to said battery terminal and a second end;

a second constant current source having a first end connected to said battery terminal and a second end;

a second transistor having a first end connected to said first constant current source and having a second end connected to the first end of said reference resistor; and

a third transistor having a first end connected to said second constant current source and a second end connected to said output terminal,

said second and third transistors being analogeous to each other and being controlled by a voltage at the first end of said second transistor,

the first end of said third transistor generating an overcurrent detecting signal.

8. An overcurrent detecting circuit device comprising:

a battery terminal connectable to a battery;

an output terminal connectable to a load;

a first transistor, having a first end connected to said battery terminal and a second end, for detecting whether or not an overcurrent has flown to said output terminal;

a reference resistor having a first end connected to the second end of said first transistor and a second end connected to said output terminal;

a constant current source having a first end connected to said battery terminal and a second end; and

a second transistor having a first end connected to said constant current source and a second end connected to said output terminal, and being controlled by a voltage at the first end of said reference resistor,

the first end of said second transistor generating an overcurrent detecting signal.

9. An overcurrent detecting circuit device comprising:

a battery terminal connectable to a battery;

an output terminal connectable to a load;

a first transistor, having a first end connected to said battery terminal and a second end, for detecting whether or not an overcurrent has flown to said output terminal;

a reference resistor having a first end connected to the second end of said first transistor and a second end connected to said output terminal;

a first resistor having a first end connected to said battery terminal and a second end;

a second resistor having a first end connected to said battery terminal and a second end;

a second transistor having a first end connected to the second end of said first resistor and a second end connected to the first end of said reference resistor;

a third transistor having a first end connected to the second end of said second resistor and a second end connected to said output terminal, said second and third transistors being analogeous to each other and being controlled by a voltage at the first end of said second transistor; and

a comparator, connected to the first end of said third transistor, for comparing a voltage at the first end of said third transistor with a reference voltage to generate an overcurrent detecting signal.

10. An overcurrent detecting circuit device comprising:

a battery terminal connectable to a battery;

an output terminal connectable to a load;

a first transistor, having a first end connected to said battery terminal and a second end, for detecting whether or not an overcurrent has flown to said output terminal;

a reference resistor having a first end connected to the second end of said first transistor and a second end connected to said output terminal;

a resistor having a first end connected to said battery terminal and a second end;

a second transistor having a first end connected to the second end of said resistor and a second end connected to said output terminal and being controlled by a voltage at the first end of said reference resistor; and

a comparator, connected to the first end of said second transistor, for comparing a voltage at the first end of said second transistor with a reference voltage to generate an overcurrent detecting signal.