Brushed-DC motor control is very simple: a voltage applied across the motor terminals changes the magnetic field on the rotor and create a continuous spinning motion. Despite having drawbacks such as heat dissipation, high rotor inertia, and electromagnetic interference, Brushed DC motors do not require current feedback and are easy to control, making them a simple low-cost design for many applications as shown in Figure 3-1.

Typically, Brushed-DC motors require high current at startup to overcome inertia then only small current to maintain steady state operation. To accomplish this, PWM duty cycle control is utilized to modulate the control waveforms so N-type MOSFETs (which control the switching current) are on for a portion of the PWM period rather than 100% of the time. Additionally, an H-bridge inverter is used to control the motor direction and decay modes for optimum motor braking and recirculation currents.

Figure 3-1 H-Bridge Motor Control for Brushed-DC Motors

In systems that require current feedback to the microcontroller for advanced commutations such as ripple counting or torque control, a current shunt resistor can be placed at the low-side of the H-bridge or inline to the motor phase.

H-bridge drivers can have various types of power and analog control integration to reduce the system form factor. The MCU provides the control algorithm, and the analog integration can be integrated into the MCU or the driver.