Glossary · Motion control and drives
H-bridge
Also known as: Full bridge, H-bridge circuit
German: H-Brücke
In power electronics, an H-bridge is a circuit of four switches, usually MOSFETs, arranged around a load so that the voltage across it can be applied in either polarity; drivers use one H-bridge per motor phase to reverse and regulate the winding current.
- Motion control
In one sentence
An H-bridge is a four-switch circuit that applies voltage to a load in either polarity; stepper drivers use one per phase.
Example
A two-phase stepper driver IC contains two H-bridges, one for each winding, that reverse the current direction for every full step.
How it applies
- Engineering: Two diagonal switches conduct at a time; switching both switches of one side at once short-circuits the supply (shoot-through), which the driver prevents with dead time. Three-phase motors use three half bridges instead.
- Commissioning: Bridge current limits and the supply voltage rating must cover the motor and its back EMF.
- Operation: Short circuits in the motor cable load the bridge; drivers monitor it with Overcurrent protection.
- Documentation: Tell installers not to connect or disconnect the motor while the driver is powered: the inductive voltage spike can destroy the bridge. State this as a notice about equipment damage, not as a personal safety warning.