Switch box and overcurrent preventing method

1. A switch box comprising:

a circuit substrate that comprises a conductor pattern;

a switching element that is mounted on the circuit substrate;

a bus bar that comprises a current input and output portion formed at one end thereof and a mounting portion formed at the other end thereof, the mounting portion being connected to the conductor pattern of the circuit substrate so as to be electrically conducted to the switching element through the conductor pattern; and

a magnetic sensor that is mounted on the circuit substrate to detect a magnetic field generated due to a current flowing into the bus bar,

wherein the magnetic sensor is disposed in a gap formed between the circuit substrate and the bus bar,

wherein the mounting portion of the bus bar comprises a plurality of branch connection portions which are electrically conducted to the switching element through the conductor pattern, and

wherein the magnetic sensor is disposed so as to be closer to the current input and output portion than the branch connection portions.

2. The switch box according to claim 1 , wherein the bus bar comprises a bent portion which is provided between the current input and output portion and the mounting portion and bent perpendicularly to a direction parallel to the current input and output portion and the mounting portion; and

wherein the magnetic sensor is disposed in a vicinity of the bent portion.

3. The switch box according to claim 1 , further comprising:

a plurality of shield plates that are comprised of a magnetic material and that cover the magnetic sensor, the bus bar and the circuit substrate.

4. The switch box according to claim 1 , wherein the bus bar and other bus bar are mounted on the circuit substrate so as to be disposed in parallel with one another; and

wherein at least one of the bus bar and the other bus bar has a side extension portion which extends in a direction perpendicular to an extension direction of the at least one of the bus bar and the other bus bar and an end portion of the side extension portion is the current input and output portion.

5. An overcurrent preventing method in a switch box comprising:

a circuit substrate that comprises a conductor pattern;

a switching element that is mounted on the circuit substrate;

a bus bar that comprises a current input and output portion formed at one end thereof and a mounting portion formed at the other end thereof, the mounting portion being connected to the conductor pattern of the circuit substrate so as to be electrically conducted to the switching element through the conductor pattern; and

a magnetic sensor that is mounted on the circuit substrate to detect a magnetic field generated due to a current flowing into the bus bar,

wherein the mounting portion of the bus bar comprises a plurality of branch connection portions which are electrically conducted to the switching element through the conductor pattern, and

wherein the magnetic sensor is disposed so as to be closer to the current input and output portion than the branch connection portions,

the overcurrent preventing method comprising:

blocking a current from flowing into the switching element, when the current having a current value equal to or greater than a predetermined value flows into the bus bar for at least a predetermined time based on a detection result output from the magnetic sensor.

6. The switch box according to claim 1 , wherein each of the plurality of branch connection portions has a plurality of terminals.