Patent ID: 7138778

Claim:
A PWM inverter having three phases of arms, connected in parallel to a DC power source, each phase consisting of an upper arm and a lower arm which function in pairs so as to control alternating current, and current sensors disposed at either all of the upper arms or the lower arms of said three phases, wherein said current sensor consists of a power MOSFET, connected between an electric load and a power source, for controlling current that flows through said electric load, a mirror MOSFET, connected in parallel to said power MOSFET, wherein a portion of the current that flows through said power MOSFET flows, a current detection resistor connected between a source electrode of said power MOSFET and a source electrode of said mirror MOSFET, and a converting means for converting positive and negative voltages generated across said current detection resistor into a positive or negative voltage; and said PWM inverter further having a driving device for detecting current of each phase based on the current detection signal outputted from said current sensor of each phase when all of the arms located on the opposite side of the arms where said current sensors are disposed are turned OFF within the PWM switching period, thereby controlling alternating current.