In this paper,a new rotor position detecting method for the sensorless control of brushless DC motor ( BLDCM) is introduced. It obtains the phase back EMF signal from the motor terminal voltage by properly choosing the PWM and sensing strategy directly and needn't the motor neutral point voltage information. The paper analyzes both the steady-state of PWM on the high side modulator mode which doesn't consider the parasitic capacitance Coes in the switches and the transient-state of PWM on the high side modulator mode which considers the parasitic capacitance Coes in the switches in detail. The experimental results verify that the proposed method is not sensitive to switching noise,no filtering is required,and good motor performance is achieved within a wide speed range.
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