This paper presents a method for the sensorless control in full speed range for an interior permanent-magnet synchronous motor (IPM). At standstill and very low speed region, high frequency (HF) injection technique is used to detect the rotor initial position. A hybrid observer is applied to realize a smooth transition from low to high speed. When the rotor speed goes up to a certain value where back EMF can provide adequate information, a back EMF observer will dominate. The hybrid observer is verified through simulation and experimental results using a three-phase 1-kW IPM motor drive.