AC adapter

An external power supply that converts mains alternating current into the voltage and current required by an electronic device. It may use a transformer or electronic switching circuitry.

Switched-mode power supply: A power supply that regulates output by rapidly switching semiconductor devices and filtering the resulting electrical waveforms. Most compact adapters use high-frequency switching to reduce transformer size and regulate output.
Alternating current: Electric current that periodically reverses direction. The adapter’s input comes from mains power, which is supplied as alternating current.
USB Power Delivery: A USB charging standard that negotiates power levels between compatible sources and devices. It lets some adapters provide several negotiated voltages through a USB-C connection.
Internal power supply: A power-conversion circuit housed inside the electronic equipment it powers. It performs a similar conversion inside the device rather than in a separate enclosure.
Standby power: Electrical power consumed by equipment while it is not performing its primary function. An adapter left plugged in may draw power even when its device is switched off or disconnected.
Linear power supply: A power supply that regulates voltage by dissipating excess energy in a series-pass component. It is a simpler alternative to switching circuitry, but usually wastes more energy and weighs more.
Direct current: Electric current that flows in one direction, though its magnitude may vary. Many devices require direct current even though household mains supplies alternating current.
USB-C: A reversible USB connector system used for data, power, and audiovisual connections. USB-C has become a common output connector for adapters and device chargers.
Power supply unit: A device or circuit that supplies electrical power with characteristics suited to a load. An AC adapter is one external form of the broader power-supply category.
E-waste: Discarded electrical and electronic equipment and its components. Proprietary or incompatible adapters can become electronic waste when devices are replaced.

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Switch-mode power supplyRelated: Many modern adapters use switch-mode conversion to stay compact and efficient.