AC/DC adapters accept AC input voltage directly from a wall outlet, and output DC voltage. The primary configurations are wall-mount, where the adapter unit plugs directly into a wall and the DC lead then goes to the DC device, and desk mount, where the adapter unit is in-line between the AC plug and the DC output. Many DC devices use this type of adapter or power supply such as household items, printers, low-voltage DC boards, etc.
Nominal AC Input Choices
Nominal AC input choices for AC/DC adapters include 115 VAC, 230 VAC, 115/230 VAC selectable, 115/230, VAC wide-ranging or auto-select, 220 VAC European, and 100 VAC Japan. Common DC output choices for AD/DC adapters include +3.3V, +5V, -5V, +12V, -12V, +15V, -15V, +24V, -24V, +48V, and –48V. AC/DC adapters may be capable of more than one output. Many AC/DC adapters have a rating of the nominal total DC power supplied. Input plug styles, or AC pin (blade) type for AC/DC adapters can be two conductors or three conductors. Two conductor types include two round pin style, American flat pins, German round pin, etc. Three conductor types include three-pin UK style, American flat pin / grounded, three round pins, etc. The international pin or blade style for two and three conductor plug types. The shape, size and configuration vary. Output connectors can be DIN plug type, Mini DIN type, bayonet nut coupling (BNC), and thread nut coupling connectors (TNC). DIN 41612 is widely accepted as a standard for interconnect applications in the telecommunications and data markets worldwide. Mini DIN types include three, four, five, six, seven and eight pin Mini-DIN styles. A Bayonet Nut Coupling is a connector with bayonet-style couplings used for jacks on instrument front panels. A Threaded Nut Coupling Connector is an input / output electronic interconnect device similar to a BNC connector but with threaded couplings.
Common features for AC/DC adapters include overvoltage protection, overcurrent protection, and short circuit protection. Overvoltage protection is internal circuitry that limits or shuts down the voltage output in an overvoltage condition. When present, it is most usually found on the primary output. Overcurrent protection is internal circuitry that limits or shuts down the current output in an overcurrent condition. Short circuit protection includes techniques to protect the power supply in the event of a short circuit on the load may include electronic current limiting and thermal resets with automatic recovery. An important environmental parameter to consider when specifying AC/DC adapters includes operating temperature.