power brick

A power brick is an external power supply unit, typically weighing between 0.5 and 2 kg, that converts mains AC voltage to regulated DC voltage for a portable device. It consists of a transformer, rectifier circuit, and filtering components housed in a plastic enclosure roughly the size of a standard brick. Two cords extend from it: one plugs into the wall outlet, the other terminates in a proprietary connector that feeds power into the device, whether a laptop, monitor, gaming console, or external hard drive.

The bulk of a power brick's weight comes from its transformer and large electrolytic capacitors. Unlike compact wall-mount adapters, the brick design allows for heavier gauge wiring and better heat dissipation. Typical output ranges from 19V to 24V DC for laptops, up to 48V or higher for industrial equipment. The brick sits between the wall and the device because it would be impractical to fit a transformer of sufficient capacity directly into the connector or the device itself without generating dangerous heat.

Failures are common at the cord entry points, where repeated flexing cracks the insulation or breaks internal wires. The connector pins corrode or loosen over time. Heat buildup inside a brick that has accumulated dust will eventually degrade capacitor life, causing the output voltage to sag or ripple. Many users attempt to use a mismatched brick with a similar voltage rating, which can damage the device or cause the brick's protection circuitry to fail.

The term "power brick" is purely descriptive slang, referring to the literal brick-like appearance and heft of the unit. In technical specs, manufacturers call them external power adapters, AC-DC converters, or simply chargers. The design dominated consumer electronics throughout the 1990s and 2000s before USB-C power delivery and integrated regulators began reducing their necessity, though they remain standard for high-power devices like gaming laptops and studio monitors.

Quality varies significantly. Cheap bricks often skimp on input filtering and surge protection, putting downstream electronics at risk during mains transients. Better units incorporate ferrite chokes, thermal fuses, and crowbar circuits to protect against output faults. Industrial-grade power bricks designed for factory equipment are often potted in epoxy, sealed against moisture, and rated for wider temperature ranges than consumer variants.

Users should treat a brick's connector as a wear item. If the output cord becomes loose or intermittent, the brick is typically not worth repairing due to labor costs. Matched replacements from the original equipment manufacturer are preferred over third-party alternatives, as a voltage or current mismatch can shorten device life or trigger failure in ways that are difficult to diagnose.