Hbridge

An H-bridge is a four-switch arrangement that enables current to flow through a DC motor or other load in either direction. The switches are arranged in an “H” shape with the load forming the crossbar. When one diagonal pair conducts, the current flows through the load in one direction; when the opposite diagonal pair conducts, it flows in the opposite direction. Each switch is typically a transistor (MOSFET, IGBT, or BJT) and is equipped with a flyback diode to handle inductive kick. Pulse-width modulation is commonly used to control motor speed, while reversing direction is achieved by swapping which switches are on. Braking can be accomplished by shorting the motor terminals or applying a braking state to the switches.

Implementation often uses high-side and low-side switches. Using N-channel MOSFETs on both sides requires a gate drive that can exceed the supply to turn on the high side, or alternatively P-channel devices or dedicated high-side drivers. Control logic should include deadtime to prevent shoot-through. Protection features frequently employed include flyback diodes, overcurrent and overtemperature protection, current sensing, and fault reporting. H-bridges can be built from discrete components or implemented as integrated motor driver ICs that provide PWM, braking, and fault handling.

Applications and considerations: H-bridges are widely used for bidirectional control of DC motors in robotics, automation, and consumer electronics, as well as in some stepper motor systems. They offer straightforward wiring and fast switching, but high-current applications require adequate cooling and protective circuitry to manage switching losses and inductive transients.