Drive apparatus of synchronous motor and method for driving synchronous motor

A drive apparatus of a synchronous motor comprising:

• a power converter that drives the synchronous motor by sequentially applying positive and negative voltages to phases of the synchronous motor;
• a current detecting unit that detects a phase current flowing to the synchronous motor;
• and
• a magnetic pole position estimating unit that estimates a magnetic pole position of a rotor of the synchronous motor, based on the phase current detected by the current detecting unit, wherein
• the magnetic pole position estimating unit includes
• a first peak-to-peak detector that detects a first peak-to-peak value representing a difference between a maximum value and a minimum value of the phase current,
• a quadrature component detector that detects a quadrature component of the phase current, and
• a second peak-to-peak detector that detects a second peak-to-peak value representing a difference between a maximum value and a minimum value of the quadrature component, wherein
• the magnetic pole position estimating unit calculates a first magnetic pole position, based on the first peak-to-peak value detected by the first peak-to-peak detector and the second peak-to-peak value detected by the second peak-to-peak detector while the synchronous motor is stopped, and wherein
• the magnetic pole position estimating unit estimates an initial magnetic pole position of the rotor, based on the first magnetic pole position.