halfbridge

A half-bridge is a power-electronic topology consisting of two controlled switches connected in series across a DC supply. The junction of the two switches, known as the switching node, serves as the output to the load. In many implementations, the DC link is split by two capacitors in series, creating a midpoint near one-half of the supply voltage. This split allows each switch to switch between roughly 0 and the full supply while the output seen by the load is the average voltage at the switching node.

Operation typically uses PWM signals applied to the two switches with complementary timing and a defined dead time to prevent shoot-through. When the top switch conducts, the switching node goes toward the positive rail; when the bottom switch conducts, it goes toward the negative rail (or ground). The average voltage at the switching node is controlled to regulate the load, and in transformer-coupled designs the primary may be connected between the switching node and the opposite rail, producing an alternating output.

Key considerations include the need for proper gate-drive hardware, especially for the high-side switch, which often requires a bootstrap or isolated driver. Midpoint balancing between the two DC-link capacitors is important to prevent drift that can unbalance the half-bridge and affect performance. The topology is easy to implement and minimizes voltage stress on each device, but adds requirements for capacitor balance, dead-time control, and EMI management.

Applications of half-bridge circuits include DC-DC converters, motor-drive inverters, and power supplies, where compactness and efficient switching are advantageous. It forms the basic building block of more complex topologies such as full-bridge inverters and multi-level converters.