SoCs boost motor efficiency

Demand for brushless dc (BLDC) motors is growing as designers look for improved efficiencies and quieter, cleaner operation in applications such as fans, industrial pumps and home appliances. However, accurate control of BLDC motors has required complex hardware and software designs. This complexity can now be reduced using advanced controller and inverter semiconductor platforms, leaving engineers with more time to concentrate on the product’s competitive advantage. The key elements needed to control and drive a BLDC motor are: the logic and software needed to provide high level control (for instance, start up sequencing and fault state handling); the power blocks, a rectifier and a power MOSFET or IGBT based inverter stage; and the MOSFET/IGBT gate drivers. Designs also need a mechanism to sense rotor position and allow the controller to calculate the necessary stator waveform; only then can the electronics commutate the outputs at the correct time to produce the desired speed and direction of motion. This feedback mechanism can be sensor based – normally using Hall sensors – or sensorless, in which case the circuit measures the back EMF from the stator coils and employs the necessary algorithms to determine the rotor position. Whether sensor based or sensorless, the underlying technology for the motor drive circuit will be pulse width modulation (PWM). However, the designer also has to decide how complex the PWM circuit to be used will be.