Simplifying BLDC Commutation and Feedback System - White Paper

In a Brushless DC (BLDC) motor system, an electronic mechanism is required to commutate the system. Unlike a Brush DC motor system, the permanent magnet is located at the Rotor and the windings are located at the Stator. As a result of this setup arrangement, the windings are required to energize in sequence, to enable smooth commutation. For the electronic system to determine which windings to energize, Hall sensor feedback is used to get the current location of the windings with respect to the Rotor magnet. When using the Hall sensor, the manufacturer is required to add an additional printed circuit board and magnet that will increase cost. Furthermore, an additional 2- or 3-channel positional encoder is required for servo application that will further increase the complexity of the BLDC motor system. This problem can be resolved by using Avago Technologies' 6-channel optical encoder where the positional encoder and commutation feedback are combined into one module. In addition, the module is effective in simplifying the motor alignment processes and improving switching accuracy. As a result, the use of Avago Technologies' modular solution will greatly reduce the motor package complexity and cost.