Patent ID: 8890450

Claim:
A motor control device comprising: an inverter circuit including a plurality of switching elements which is connected into a three-phase bridge configuration, the switching elements being on/off controlled according to a predetermined PWM signal pattern so that direct current is converted to three-phase alternating current, which is supplied to drive an electric motor; a current detecting element connected to a direct current side of the inverter circuit to generate a signal corresponding to a current value; a current detection unit which detects a phase current of the motor based on the signal generated by the current detecting element and the PWM signal pattern; a PWM signal generation unit which generates a three-phase PWM signal pattern so that the current detection unit is capable of detecting two-phase currents twice in synchronization with four time-points within a carrier wave period of the PWM signal respectively and so that the current detection unit follows a magnetic pole position of the motor; a current differential unit which supplies, as current differential values, differences between twice detected current values regarding the two phases respectively; and a magnetic pole position estimation unit which estimates the magnetic pole position of the motor based on the current differential values, wherein: the PWM signal generation unit increases/decreases a duty cycle in both directions of phase lag and phase lead with an arbitrary phase within the carrier wave period serving as a reference regarding one phase of the three-phase PWM signal; the PWM signal generation unit increases/decreases the duty cycle in one of both directions of phase lag and phase lead with an arbitrary phase within the carrier wave period serving as a reference regarding another phase of the three-phase PWM signal; and the PWM signal generation unit increases/decreases the duty cycle in a direction opposed to said one of both directions of phase lag and phase lead with an arbitrary phase within the carrier wave period serving as a reference regarding the remaining phase of the three-phase PWM signal.