Patent ID: 7714624

Claim:
A method for controlling a vertical type MOSFET in a bridge circuit, the bridge circuit including an external diode which is connected in inverse-parallel with and is external with respect to the vertical type MOSFET, the bridge circuit being configured so that a gate voltage of the vertical type MOSFET controls a forward voltage of a built-in diode of the vertical type MOSFET, the method comprising: controlling the forward voltage of the built-in diode to be a first forward voltage by setting the gate voltage of the vertical MOSFET to a first gate voltage, so that the vertical type MOSFET is switched into a first off mode, which is one of modes in an off state of the vertical type MOSFET, wherein, in the first off mode, a current flowing through the built-in diode is larger than a current flowing through the external diode; and controlling the forward voltage of the built-in diode to be a second forward voltage by setting the gate voltage of the vertical MOSFET to a second gate voltage, so that the vertical type MOSFET is switched into a second off mode, which is another one of modes in the off state of the vertical type MOSFET, wherein, in the second off mode, the current flowing through the built-in diode is smaller than the current flowing through the external diode, wherein: in the controlling the forward voltage of the built-in diode to be the first forward voltage and the controlling the forward voltage of the built-in diode to be the second forward voltage, a relation Vfd<Vf 1 <Vf 2 or a relation Vf 1 <Vfd<Vf 2 is satisfied, where Vf 1 , Vf 2 , and Vfd are defined as the first forward voltage of the built-in diode, the second forward voltage of the built-in diode, and a forward voltage of the external diode, respectively.