Motor driver (H-bridge)

Microcontrollers can't power motors directly. A motor driver uses power transistors (MOSFETs, or IGBTs at higher power) to switch supply current into the motor windings according to PWM signals. An H-bridge, four switches arranged around the motor, drives a brushed DC motor in both directions; a three-phase bridge drives brushless motors; stepper drivers regulate current in the two phases of a stepper.

Integrated driver chips cover low to moderate power; larger motors use separate gate drivers and power transistors. Current sensing, over-current and over-temperature protection, stall detection and controlled braking are part of the job.

Where it bites: heat in the driver, fast switching edges that cause EMI, voltage spikes from motor inductance, and regenerative braking that pushes the supply voltage up and can damage parts.