I. Introduction
A high-speed brushless dc (BLDC) motor as a core component of the high-speed magnetic levitation (maglev) blower can be directly connected to the high-speed mechanical equipment and it effectively improves the system efficiency [1], [2]. The back-electromotive-force (EMF) technique as a sensorless strategy with profound applications has become a research focus recently, which is a scheme to estimate the rotor position indirectly by using the zero-crossing point detection from the terminal voltage [3], [4]. It has been used for wide-speed-range control of a BLDC motor [5].