Integrated control BLDC drivers

To compare the various types of commutation methods for three-phase BLDC motor, there are many system level considerations including motor constuction, application type, performance needs, design complexity, and many more. Check out this video and the following tabs to learn more about the BLDC control methods and their advantages and tradeoffs.

Trapezoidal commutation is popular because of its simplicity, low cost, and reliability. It's the easiest commutation technique to implement compared to sinusoidal and field-oriented control. Its simplicity reduces design time and cost, especially in terms of processing power used for the control algorithms.

Characteristics:

• Low cost
• Simple to implement
• Less processing power
• Good for high speed applications
• High electric and acoustic noise
• Large torque ripple

In sinusoidal BLDC motors, windings for each phase produce a sinusoidal back EMF voltage. You can find sinusoidal control in speed applications since they require low noise, smooth, and efficient motor performance.

Characteristics:

• Ultra-quiet
• Highly efficient
• Small torque ripple
• No direct BEMF measurements due to no zero crossing window
• More switching losses compared to Trapezoidal
• Increased complexity

With FOC, we can achieve the lowest audible noise, the highest motor efficiency, and high motor speed using real-time calculations involving the motor phase currents and rotor position to apply maximum torque at all rotor postions. 

Characteristics:

• Highest torque and motor efficiency
• Lowest audible noise and torque ripple
• High motor speed +field weakening
• High switching loses
• Complex control and real-time calculations needed from an MCU

In sensorless control applications, sensors are used to determine the actual location of the rotor relative to the stator. Sensors can be used in torque, speed, or position control applications. The main advantage to using sensors is that it is a low-complexity easy-to-implement solution that gives immediate motor position, even at slow speeds or rest.

Characteristics:

• Low complexity
• Position is known immediately
• Typically low resolution
• Takes up board or motor space

Sensorless control can potentially remove the need for external sensors by measuring the back EMF zero crossings, or calculating the back EMF generated during commutation. Typically, sensorless control is used for speed applications since the motor will generate enough back EMF when it is spinning at a constant speed.

Characteristics:

• Saves board space by eliminating sensors
• Eliminates risk of failures from the sensors
• Additional signal chain and calculations required