Brushless DC motor and DC motor has the same working principle and application characteristics, and its composition is not the same as. In addition to the motor itself, the former is a reversing circuit, a motor and a reversing circuit together. Many small power motor reversing circuit itself is associated with a synthetic one, look from the exterior of Brushless DC motor and DC motor exactly the same. Brushless DC motor itself is the electromechanical energy conversion part, which in addition to the motor armature, permanent magnet excitation two part, but also with sensor. The motor itself is a brushless DC motor core, it is not only related to the performance of vibration, noise, reliability and service life, but also relates to the manufacturing costs and the cost of the product. Due to the adoption of the permanent magnetic field, the brushless DC motor from the general DC motor of traditional design and structure, to meet a variety of applications to market requirements, and to save copper material, simple manufacture direction. Permanent magnetic field of permanent magnetic materials development and application is closely related to, the third generation permanent magnet material application, prompting a brushless DC motor to high efficiency, miniaturization, energy saving direction. In order to realize electronic commutation must have a position signal to control circuit. Early use of electrical position sensor to obtain the position signal, is now gradually electronic position sensor or other method to get the position signal, the most convenient way is to use the armature windings of the electric potential signal as the position signal. To achieve motor speed control must have speed signal. Used to obtain a position signal similar method to obtain velocity signal, the most simple velocity sensor is measuring frequency tachometer generator and electronic circuit combination. DC brushless motor commutation circuit is composed of drive and control of two parts, the two part is not easy to separate, especially low power circuits often will both integrated into a single application specific integrated circuit.