Brushless DC motors are three-phase motors that are driven through electrical commutation. Voltage applied to the stator coils generate magnetic field which interacts with the rotor magnetic field. Interaction between these two fields causes the rotor to spin. The inputs for the commutation come from the controller and are scaled through a power stage to send power to the motor phases. The power stage for driving the motor consists of turning on or off the MOSFET half-bridges per phase. A motor driver is a power converter that switches the MOSFET based on several PWM modulation techniques. Modulated PWM voltage is applied to the BLDC motor to control speed, torque and position of the motor
The leading implementation of motor drivers in the market, can be split into two categories based on architecture for the purposes of this technical report.
This application note includes the key differences and pros and cons for each architecture. Three-phase architecture offers advantages with more half bridge integration making final implementation more straight forward with one package but faces challenges in signal integrity. Whereas using three half bridges require more local passives but offer flexibility in MOSFET placement, thereby, improving signal integrity and reducing effects of trace inductance.
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A three-phase BLDC driver can commutate three half-bridges (six MOSFETs) and a single Half-Bridge driver as the name implies drives one half-bridge (two MOSFETs).
There are unique advantages to both systems which makes them desirable for their intended applications. Knowing the system level benefits can make the decision easier for which method can be beneficial for your application.
TI’s current Brushless DC (BLDC) motor drivers’ portfolio contains predominantly three-phase BLDC drivers serving as a one unit package to spin a brushless motor. However, with the addition of drivers such as DRV8161 and DRV8162 we are expanding our portfolio to include single half-bridge drivers (Figure 1-1). These single half-bridge drivers offer key advantages in reducing driver to power stage distance. This results in greatly improving efficiency and decreasing the effects of parasitic.