This paper describes position-sensorless control method by modified Pulse Width Modulation (PWM). Sensorless control for low speed including zero-speed utilizes the magnetic saliency from the current variation. High frequency voltage injection type methods require high amplitude and high frequency voltage to improve control performance. The voltage injection results in the increase of audible sound pressure level resulting in the unpleasant sound. To obtain higher control performance without increasing the sound pressure level, proposed method utilizes the output voltage vector variation to obtain the current variation. In this method, the vector pattern of PWM is modified to extract current variation easily. The modified PWM utilizes 4 efficient voltage vectors to amplify the current variation. The current is detected multiple times in a carrier period to derive current variation. Experimental results show the estimation accuracy and the control performance of the proposed method.