H-bridge

An H-bridge is an electronic circuit that enables a voltage to be applied across a load in either direction. It is commonly used in robotics and other applications to control the direction of a DC motor's rotation. The "H" refers to the typical graphical representation of the circuit, with the load in the middle and four switching elements forming the arms of the "H".

The basic H-bridge consists of four switches (usually transistors) arranged in a specific configuration. Two switches are on the "high" side of the bridge, connected to the positive voltage supply, and two are on the "low" side, connected to the ground or negative voltage supply. The load, such as a DC motor, is connected between the two midpoints of the bridge.

By selectively closing and opening pairs of switches, the direction of the current flowing through the load can be controlled. To rotate the motor in one direction, one pair of diagonally opposed switches is closed (e.g., the top-left and bottom-right switches). To reverse the motor's direction, the opposite pair of diagonal switches is closed (e.g., the top-right and bottom-left switches).

It is crucial to avoid closing both switches on the same side of the bridge simultaneously, as this creates a short circuit between the power supply and ground, potentially damaging the transistors and the power supply. This condition is often referred to as "shoot-through" or "crowbar". Logic circuitry or dedicated driver chips are typically used to prevent this condition from occurring.

H-bridges are not limited to controlling DC motors. They can also be used to drive other types of loads, such as solenoids, speakers, and thermoelectric coolers, where bidirectional voltage control is required.

Several parameters are important when selecting an H-bridge for a particular application, including the maximum voltage and current the H-bridge can handle, the switching speed, and the on-resistance of the transistors. These parameters determine the H-bridge's efficiency and its suitability for different loads and operating conditions.