As many automotive functions evolve from purely mechanical to electrically-driven, the use of efficient brushless DC motors is becoming prevalent. This paper discusses the design of a BLDC motor controller, including the technical tradeoffs, hardware implementation, and testing results. This design example examines the specific requirements for a compact solution for driving a water pump, but the design methodology and tradeoffs also apply to other motor control applications where efficient control of motor speed is needed. Practical details such as component parameters are discussed to guide designers in identifying the link between critical performance requirements and component selection. The paper includes discussion of circuits which mitigate EMC issues inherent in switching supplies and power stages. Attention is also paid to ancillary design topics such as reverse battery protection, overvoltage due to load dump, thermal issues, and other fault-tolerant considerations. Compared to previous papers, the intent is to discuss the application with a holistic view, considering the practical interrelations between the various circuits and functions. The final design hardware is discussed, with test results showing comparison to expected performance. Lessons learned provide guidance for similar designs, with variations for increased power applications, or alternate loads, such as direct-drive or gear-driven positioning systems.
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