A DC connector (or DC plug, for one common type) is an electrical connector that supplies direct current (DC) power. Compared to domestic AC power plugs and sockets, DC connectors have many more standard types that are not interchangeable. The dimensions and arrangement of DC connectors can be chosen to prevent accidental interconnection of incompatible sources and loads. Types vary from small coaxial connectors used to power portable electronic devices from AC adapters to connectors used for automotive accessories and for battery packs in portable equipment.
Extra-low voltage (under 120 VDC) These extra-low voltage connectors are rated at or below 120 VDC.
Cylindrical connectors
Small cylindrical connectors come in various sizes. They may be known as "coaxial power connectors," "barrel connectors," "concentric barrel connectors," or "tip connectors." These plugs are intended for use on the cable connected to an external AC adapter (power supply). The matching jack or socket is permanently fitted to power the equipment. Some of these jacks contain a normally closed contact, which can be used to disconnect internal batteries whenever the power supply is connected, avoiding the risk of battery leakage or explosion posed by incorrect battery recharging. Cylindrical plugs usually have an insulated tip constructed to accept the insertion of a pin. The outer body of the plug is one contact, most often but not always the negative side of the supply. Inverted polarity plugs can and do damage circuitry when plugged in, even if the voltage is correct; not all equipment is equipped with protection. A pin mounted in the socket makes contact with a second internal contact. The outer plug contact is often called the barrel, sleeve, or ring, while the inner is called the tip. There are a wide variety of sizes and designs for these power connectors, and many appear pretty similar to each other yet are not quite mechanically or electrically compatible. In addition to many generic designs (whose original designer is unknown), there are at least two national standards—EIAJ in Japan and DIN in Germany, plus the JSBP connector used on some laptop computers. The Japanese EIAJ standard includes five sizes, each supporting a specified range of voltages. However, most other coaxial DC power connectors have no specified voltage association. Generic plugs are often named for the pin diameter they are designed to take. Many non-proprietary co-axial power plugs are 5.5 mm (0.22 in) in outside diameter (OD) and 9.5 mm (0.37 in) in length. Two pin sizes are standard in the jacks for this size plug body, 2.1 mm (0.083 in) and 2.5 mm (0.098 in), and the plugs should match. If the size is not known, it is difficult to distinguish by eye or measurement between the 2.1mm and 2.5mm ID plugs; some suppliers suggest simple methods. Maximum current ratings commonly vary from unspecified up to 5 A (11 A for unique high-power versions from some companies), with 1 A, 2 A, and 5 A being common values. The smaller types usually have lower ratings, both for current and voltage. The 'tip' (i.e., the inner conductor) usually carries the positive (+) pole, but some devices and their power supplies use the negative tip. The connector size does not usually indicate the voltage. It is not possible, except for some proprietary connectors, to reliably infer any information on power parameters (current, voltage, polarity, even whether AC or DC) by examining the connector.
Snap and lock DC power connectors
Snap and lock DC power connectors look similar to Mini-DIN connectors but have either 3 or 4 thicker pins and a slightly larger mating shell. Because of this, they do not mate with any of the standardized Mini-DIN connectors. Some devices, however, use a proper 4-pin Mini-DIN connector for power instead, presenting the possibility of mating such a connector with the wrong port (such as an S-Video output).
Known as Kycon 3-pin and 4-pin DC power plugs. Erroneously also known as "Power DIN", although different from any standardized Mini-DIN or DIN connector type. The male plug's mating shell outer diameter is 10 mm (0.39 in), and the pins are 1.5 mm (0.059 in) diameter Standard may include a limit of 20 V at 7.5 amperes Sometimes, there's a knurled retaining ring surrounding the male plug which allows fastening the plug to the chassis receiving the power. Some connectors have a right-angle connector, as seen in the picture. For aesthetics, some Dell laptop chargers have a glowing ring at the connector tip.
Molex connector
Molex connectors were frequently used as DC power connectors in personal computers, for floppy, hard disk, and CD drives. These connectors have four pins, +5 V (red), 2 common ground (black), and +12 V (yellow). SATA peripherals use a different style of connector. Locking Molex connectors are available in 3, 4, and 6 terminal configurations.
XT connectors Solder cup terminals are primarily designed for the in-line solder termination of conductors. This style of terminal is principally designed as a precision-machined pin for insertion into connector bodies.
IEC 60906-3:1994 The International Electrotechnical Commission (IEC) has produced a standard for a system of 2-pin plugs and socket-outlets for household and similar purposes in fixed and portable applications, either indoors or outdoors. Safety extra-low voltage (SELV) plugs and socket-outlets carry up to 16 amperes, and have eight keying possibilities, to indicate 6, 12, 24, or 48 volts, AC or DC. The connector is circular, with the male connector having two pins placed symmetrically inside a circular shield, and the female connector having two receptacles surrounded by a circular groove to accept the male shield, in turn surrounded by a second circular shield which projects 6 mm (0.24 in) past the mating surface and encloses the male connector. (It somewhat resembles a smaller IEC 60309 connector.) The dimensions are as follows:
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