Halbbrücke

Halbbrücke, or half-bridge, is a circuit topology used in power electronics. It comprises two switching devices connected in series across a DC supply, with the node between them serving as the half-bridge output. In many designs the DC bus is split by two capacitors to create a quasi-midpoint reference, allowing the switches to control the output relative to this reference.

Operation typically involves complementary switching of the two devices so that only one device conducts at a time, preventing shoot-through. The output at the midpoint can be driven to swing between the supply rails, enabling an AC-like waveform across the load when used in single-ended mode (load connected from the midpoint to a reference rail) or in differential configurations. The half-bridge is a common building block in various power-electronic stages, including DC-DC converters, motor drives, and audio amplifiers.

Design and control considerations include the method for driving the high-side device, which often requires a gate-drive technique that can exceed the bus voltage, such as bootstrap circuits or isolated drivers. The mid-point capacitor must be carefully balanced to avoid DC offset and voltage drift, since imbalances can shift the operating point over time. Dead-time control is important to prevent simultaneous conduction of the two switches.

Variations and applications: two half-bridges can be combined to form a full-bridge (H-bridge) for bidirectional current flow. Advantages of the half-bridge are a reduced number of switches and potentially lower device ratings, while disadvantages include the need for a split DC bus, midpoint balancing, and more complex gate-drive circuitry.

See also: H-bridge, full-bridge, PWM, power electronics.