A pulse width modulation (PWM) module is configured to adjust the input PWM control signal and the motor can be implemented in different rotation speed to enhance the flexibility of the implementation of the motor when the PWM control signals are the same. In addition, the PWM modulation block in the present invention includes a PWM direction control circuit, a PWM vector transfer circuit and a PWM signal generation circuit. Apparently, the PWM modulation block of the present invention is connected to a PWM control signal inputted by an external system and an external adjustment apparatus; by setting up the adjustment apparatus, the vector and the modulation direction of the PWM control signal can be adjusted, and the duty cycle of the PWM control signal can also be adjusted.