JP2013143905A - Power supply control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply control device capable of surely blocking a power supply path from a battery to an electric load when a semiconductor switch is short-circuited.SOLUTION: A control unit 19 turns on an FET13 and a switch 14 when receiving a driving signal which instructs driving of an electric load 3. A differential amplifier composed of a resistor 15, a resistor 16, and an operational amplifier 17 applies a voltage higher than or equal to a prescribed voltage to a relay coil 81 to turn on a relay contact 82 and supplies power to a heating element 12 from a battery 2 when detecting a short-circuit between a drain and a source of the FET13 from a voltage between the drain and source. The heating element 12 supplied with power produces heat to heat a breaking element 11. The heat produced by the FET13 and the heating element 12 is applied to the breaking element 11. The breaking element 11 blocks a power supply path from the battery 2 to an electric load 3 when heated beyond a prescribed temperature.

Description

  The present invention relates to a power supply control device that is preferably mounted on a vehicle and controls power supply from a battery to a vehicle-mounted load by turning on / off a semiconductor switch such as a field effect transistor (FET) or a bipolar transistor.

  Currently, electric loads such as lamps, wipers, air conditioners, electric brakes, electric power steering, and car navigation systems are mounted on vehicles. Many electric loads mounted on a vehicle are supplied with power from a battery via a semiconductor switch, and power supply from the battery is controlled by turning on / off the semiconductor switch.

  In the power supply control device that controls the power supply to the electric load by turning on / off the semiconductor switch, when the semiconductor switch fails due to static electricity, surge voltage, overcurrent, etc., for example, the FET drain and source are short-circuited. In such a case, the electric load continues to operate, and there is a possibility that the operation does not follow the driver's intention.

  Therefore, Patent Document 1 discloses a power supply control device that prevents power supply from a battery to an electric load in a state where a semiconductor switch is short-circuited.

  In the power supply control device described in Patent Document 1, a MOSFET (Metal-Oxide Semiconductor Field Effect Transistor) is used as a semiconductor switch, and the MOSFET is turned on / off by applying a voltage to the gate of the MOSFET via a resistor. When detecting the state of the MOSFET immediately before short-circuiting from the voltage between both terminals of the resistor connected to the gate, the power supply control device stops applying the voltage to the gate and turns off the MOSFET.

JP 2007-174756 A

  By the way, as a power supply control device that prevents the power supply from the battery to continue to be continued when the semiconductor switch is short-circuited due to a failure, the power supply path from the battery to the electrical load is interrupted when heated above a predetermined temperature. There has been proposed a power supply control device using a blocking element.

  When the semiconductor switch is short-circuited due to a failure, the on-resistance of the semiconductor switch increases. This increases the amount of heat generated from the semiconductor switch when a current flows through the semiconductor switch. Furthermore, since the semiconductor switch is short-circuited, current continues to flow from the battery to the semiconductor switch, and high heat is generated.

  In the power supply control device using the shut-off element, when the shut-off element is arranged near the semiconductor switch and the semiconductor switch is short-circuited, the shut-off element is heated to a predetermined temperature or more by the heat generated by the semiconductor switch, and the shut-off element is removed from the battery. Cut off the power supply path to the electrical load. Thereby, it is prevented that the power supply from the battery to the electric load is continued in a state where the semiconductor switch is short-circuited.

  However, since it is difficult to place the shut-off element at a position where heat generated from the semiconductor switch is sufficiently applied, the power supply path from the battery to the electric load is shut off by the shut-off element even though the semiconductor switch is short-circuited due to a failure. There is a risk that power supply to the electrical load may be continued.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a power supply control device capable of reliably blocking a power supply path from a battery to an electric load when a semiconductor switch is short-circuited. It is to provide.

  The power supply control device according to the present invention includes a shut-off element that shuts off a power feed path from a battery to an electrical load when heated to a predetermined temperature or more, and that adds heat generated by energization to the shut-off element. In a power supply control device including a semiconductor switch, when a power is supplied and generates heat, a heating element that heats the shut-off element, a detection unit that detects a short circuit of the semiconductor switch, and the detection unit detects the short circuit And a power supply means for supplying power from the battery to the heating element.

  In this invention, a detection means detects the short circuit of the semiconductor switch provided in the electric power feeding path | route from a battery to an electrical load. When the detection means detects a short circuit, the power supply means supplies power from the battery to the heating element. The heating element is supplied with electric power from the electric power supply means and generates heat to heat the interruption element. The shut-off element shuts off the power supply path from the battery to the electric load when the temperature of the shut-off semiconductor switch exceeds a predetermined temperature due to heat generated by the short-circuited semiconductor switch and heat applied by the heating element.

  Thus, when the semiconductor switch is short-circuited due to a failure, the interrupting element is heated by the semiconductor switch and the heating element, so that the power supply path from the battery to the electric load is reliably interrupted.

  The power supply control device according to the present invention is characterized in that the detection means is configured to detect the short circuit based on a voltage between both terminals of the semiconductor switch that is turned on.

  In the present invention, the detection means detects a short circuit due to a failure of the semiconductor switch based on the voltage between both terminals of the semiconductor switch that is turned on.

  When the semiconductor switch is short-circuited, the on-resistance of the semiconductor switch changes, and the voltage between both terminals of the semiconductor switch changes. The detecting means reliably detects a short circuit of the semiconductor switch from this voltage change.

  ADVANTAGE OF THE INVENTION According to this invention, when a semiconductor switch short-circuits, the electric power feeding control apparatus which can interrupt | block the electric power feeding path | route from a battery to an electrical load reliably is realizable.

It is a circuit diagram which shows the principal part structure of embodiment of the electric power feeding control apparatus which concerns on this invention.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a circuit diagram showing a main configuration of an embodiment of a power supply control device according to the present invention. The power supply control device 1 is preferably mounted on a vehicle and connected between the positive terminal of the battery 2 and one terminal of the electric load 3. The negative terminal of the battery 2 and the other terminal of the electric load 3 are grounded.

The power supply control device 1 supplies power from the battery 2 to the electric load 3 when receiving a drive signal for instructing driving of the electric load 3 from the outside.
The electric load 3 is a lamp. The electric load 3 is not limited to a lamp, and may be a vehicle load such as a wiper, an air conditioner, an electric brake, an electric power steering, and a car navigation.

  The power supply control device 1 includes a cutoff element 11, a heating element 12, an N-channel FET 13, a switch 14, resistors 15 and 16, an operational amplifier 17, a relay 18, and a control unit 19. The relay 18 has a relay coil 81 and a relay contact 82 (a contact).

  The positive terminal of the battery 2 is connected to one terminal of each of the blocking element 11 and the heating element 12. In the FET 13, the drain is connected to the other terminal of the blocking element 11 and one terminal of the switch 14, the source is connected to one terminal of each of the electric load 3 and the resistor 15, and the gate is connected to the control unit 19.

  In the operational amplifier 17, the non-inverting input terminal is the other terminal of the switch 14, the inverting input terminal is the other terminal of the resistor 15, one terminal of the resistor 16, the output terminal is the other terminal of the resistor 16, and The relay coil 81 is connected to one terminal. The other terminal of the heating element 12 is connected to one terminal of the relay contact 82, and the other terminal of each of the relay coil 81 and the relay contact 82 is grounded.

  The interruption | blocking element 11 is arrange | positioned in the vicinity of the heating element 12 and FET13, and the heat emitted from the heating element 12 and the heat emitted from FET13 by electricity supply are added. The interruption element 11 interrupts the power supply path from the battery 2 to the electrical load 3 when heated to a predetermined temperature or higher by the heating element 12 and the FET 13.

  The heating element 12 is, for example, a heating resistor, and generates heat when power from the battery 2 is supplied. The heating element 12 is supplied with electric power from the battery 2 when the relay contact 82 is turned on, generates heat, and heats the interruption element 11.

  The FET 13 functions as a semiconductor switch. The FET 13 is turned on when a voltage equal to or higher than the first voltage is applied to the gate by the control unit 19 and turned off when no voltage is applied to the gate.

  Assuming that the voltage between the drain and source of the FET 13 is Ei, the voltage Ei is represented by the product of “amount of current flowing through the electrical load 3” and “resistance value between the drain and source”.

  The on-resistance value between the drain and the source is several mΩ when the FET 13 is on, and several hundred mΩ or more when the FET 13 fails due to static electricity, surge voltage or overcurrent, and the drain and source are short-circuited. is there. For this reason, the voltage Ei when the FET 13 operates normally and is on is lower than the voltage Ei when the drain and source of the FET 13 are short-circuited.

  A voltage between the voltage Ei when the FET 13 operates normally and is on and the voltage Ei when the drain and source of the FET 13 are short-circuited is set as a reference voltage. When the control unit 19 turns on the FET 13 and the voltage Ei is equal to or higher than the reference voltage, a short circuit between the drain and the source of the FET 13 is detected.

Thus, a short circuit between the drain and source of the FET 13 can be reliably detected from the change in the voltage Ei.
The drain and source of the FET 13 correspond to both terminals in the claims.

The switch 14 is turned on / off by the control unit 19.
The resistors 15 and 16 and the operational amplifier 17 function as a differential amplifier. Assuming that the voltage output from the output terminal of the operational amplifier 17 is Eout and the resistance values of the resistors 15 and 16 are R15 and R16, Eout when the switch 14 is on is expressed by the following equation (1).
Eout = (1+ (R16 / R15)) Ein (1)
When the switch 14 is off, no voltage is output from the output terminal of the operational amplifier 17.

  Eout output from the output terminal of the operational amplifier 17 is applied to the relay coil 81. The relay coil 81 turns on the relay contact 82 when Eout is equal to or higher than the second voltage, and turns off the relay contact 82 when Eout is lower than the second voltage.

  When the relay contact 82 is on, the heating element 12 is supplied with electric power from the battery 2 and generates heat. When the relay contact 82 is off, the heating element 12 is not supplied with electric power and does not generate heat.

  The resistance values R15 and R16 are set such that Eout is less than the second voltage when the voltage Ei is less than the reference voltage, and Eout is greater than or equal to the second voltage when the voltage Ei is greater than or equal to the reference voltage. .

  When receiving the drive signal, the control unit 19 applies a voltage equal to or higher than the first voltage to the gate of the FET 13 to turn on the FET 13, and further turns on the switch 14. When the control unit 19 has not received a drive signal, the control unit 19 turns off the FET 13 without applying a voltage to the gate of the FET 13 and turns off the switch 14.

  Next, the operation | movement which each structure part of the electric power feeding control apparatus 1 performs is demonstrated. When the control unit 19 receives the drive signal and turns on the FET 13 and the switch 14, power is supplied from the battery 2 to the electric load 3 through the cutoff element 11 and the FET 13.

  When the FET 13 operates normally and is on, the voltage Ei is less than the reference voltage. Therefore, a short circuit between the drain and the source of the FET 13 due to failure is not detected, and the voltage Eout output from the operational amplifier 17 is less than the second voltage. It becomes. As a result, the relay contact 82 remains off, and power is not supplied to the heating element 12. Therefore, since the interruption | blocking element 11 is not heated more than predetermined temperature, the electric power feeding path | route from the battery 2 to the electric load 3 is not interrupted | blocked.

  When the drain and the source of the FET 13 are short-circuited due to a failure, the voltage Ei is equal to or higher than the reference voltage. Therefore, the short-circuit between the drain and source is detected, and the voltage Eout output from the operational amplifier 17 is equal to or higher than the second voltage. As a result, the relay contact 82 is turned on, power is supplied to the heating element 12, and the heating element 12 heats the interrupting element 11.

  Furthermore, since the resistance between the drain and the source becomes several tens of mΩ to several hundreds of mΩ or more, the FET 13 generates high heat and heats the blocking element 11.

  Therefore, when the drain and the source of the FET 13 are short-circuited, the cutoff element 11 is heated to a predetermined temperature or higher by the heating element 12 and the FET 13 and interrupts the power feeding path from the battery 2 to the electric load 3.

  As described above, when the drain and the source of the FET 13 are short-circuited due to a failure, the interruption element 11 is heated not only by the FET 13 but also by the heating element 12, so that the power supply path from the battery 2 to the electric load 3 is reliably interrupted. can do.

  The method for detecting a short circuit between the drain and the source of the FET 13 is not limited to a method for detecting a short circuit based on the voltage Ei between the drain and the source.

  Further, the semiconductor switch in which a short circuit is detected is not limited to an N-channel FET, and may be a P-channel FET. Furthermore, the semiconductor switch in which the short circuit is detected is not limited to the FET, and may be a bipolar transistor. In this case, a short circuit between the collector and emitter of the bipolar transistor is detected.

  The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Electric power feeding control apparatus 11 Interrupting element 12 Heating element 13 FET
14 switch 15, 16 resistor 17 operational amplifier 18 relay 2 battery 3 electric load 81 relay coil 82 relay switch

Claims (2)

In a power supply control device comprising: a cutoff element that cuts off a power supply path from a battery to an electrical load when heated to a predetermined temperature; and a semiconductor switch that is provided in the power supply path and applies heat generated by energization to the cutoff element ,
A heating element that generates electric power and generates heat and heats the blocking element;
Detecting means for detecting a short circuit of the semiconductor switch;
A power supply control device comprising: power supply means for supplying power from the battery to the heating element when the detection means detects the short circuit. The power supply control device according to claim 1, wherein the detection unit is configured to detect the short circuit based on a voltage between both terminals of the semiconductor switch that is turned on.

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