AC Adapter

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AC adapter

A "wall wart" type AC adapter for a household game console

The AC adapter, AC/DC adapter orAC/DC converter is a type of external power supply,often enclosed in a case similar to an AC plug. Other names include plug pack, plug-inadapter, adapter block, domestic mains adapter, line power adapter, wall wart, orpower adapter; adapters for battery-powered equipment may be described as chargers. ACadapters are used with electrical devices that require power but do not contain internal

components to derive the required voltage and power from mains power. The internalcircuitry of an external power supply is very similar to the design that would be used for abuilt-in or internal supply.

External power supplies are used both with equipment with no other source of power andwith battery-powered equipment, where the supply, when plugged in, can sometimes chargethe battery in addition to powering the equipment.

Use of an external power supply allows portability of equipment powered either by mains orbattery without the added bulk of internal power components, and makes it unnecessary toproduce equipment for use only with a specified power source; the same device can be

powered from 120Vac or 230Vac mains, vehicle or aircraft battery by using a differentadapter.

Modes of operation

An AC adapter disassembled to reveal a simple, unregulated linear DC supply circuit.

Originally, most AC/DC adapters were linear power supplies, containing a transformer toconvert the mains electricity voltage to a lower voltage, a rectifier to convert it topulsatingDC, and a filter to smooth the pulsating waveform to DC, with residual ripple variationssmall enough to leave the powered device unaffected. Size and weight of the device waslargely determined by the transformer, which in turn was determined by the power output and

mains frequency. Ratings over a few watts made the devices too large and heavy to bephysically supported by a wall outlet. The output voltage of these adapters varied with load;
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for equipment requiring a more stable voltage, linearvoltage regulatorcircuitry was added.Losses in the transformer and the linear regulator were considerable; efficiency was relativelylow, and significant power dissipated as heat even when not driving a load.

In the early twenty-first century, switched-mode power supplies (SMPSs) became almost

ubiquitous for this purpose. Mains voltage is rectified to a high direct voltage driving aswitching circuit, which contains a transformer operating at a high frequency and outputsdirect current at the desired voltage. The high-frequency ripple is more easily filtered out thanmains-frequency. The high frequency allows the transformer to be small, which reduces itslosses; and the switching regulator can be much more efficient than a linear regulator. Theresult is a much more efficient, smaller, and lighter device. Safety is ensured, as in the olderlinear circuit, because there is still a transformer which electrically isolates the output fromthe mains.

A linear circuit must be designed for a specific, narrow range of input voltages (e.g., 220240VAC) and must use a transformer appropriate for the frequency (usually 50 or 60 Hz), but

a switched-mode supply can work efficiently over a very wide range of voltages andfrequencies; a single 100240VAC unit will handle almost any mains supply in the world.

However, unless very carefully designed and using suitable components, switching adaptersare more likely to fail than the older type, due in part to complex circuitry and the use ofsemiconductors. Unless designed well, these adapters may be easily damaged by overloads,even transient ones, which can come from lightning, brief mains overvoltage (sometimescaused by an incandescent light on the same power circuit failing), component degradation,etc. A very common mode of failure is due to the use of electrolytic capacitors whoseequivalent series resistance (ESR) increases with age; switching regulators are very sensitiveto high ESR (the older linear circuit also used electrolytic capacitors, but the effect ofdegradation is much less dramatic). Well-designed circuits pay attention to the ESR, ripplecurrent rating, pulse operation, and temperature rating of capacitors.[2]

Advantages

External AC adapters are widely used to power small or portable electronic devices. Theadvantages include:

Safety External power adapters can free product designers from worrying aboutsome safety issues. Much of this style of equipment uses only voltages low enough

not to be a safety hazard internally, although the power supply must out of necessityuse dangerous mains voltage. If an external power supply is used (usually via a powerconnector, often of coaxial type), the equipment need not be designed with concernfor hazardous voltages inside the enclosure. This is particularly relevant forequipment with lightweight cases which may break and expose internal electrical

parts.

Heat reduction Heat reduces reliability and longevity of electronic components,and can cause sensitive circuits to become inaccurate or malfunction. A separate

power supply removes a source of heat from the apparatus.

Electrical noise reductionBecause radiated electrical noise falls off with the squareof the distance, it is to the manufacturer's advantage to convert potentially noisy AC
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line power or automotive power to "clean", filtered DC in an external adapter, at asafe distance from noise-sensitive circuitry.

Weight and size reductionRemoving power components and the mains connectionplug from equipment powered by rechargeable batteries reduces the weight and size

which must be carried.

Ease of replacementPower supplies are more prone to failure than other circuitrydue to their exposure to power spikes and their internal generation of waste heat.External power supplies can be replaced quickly by a user without the need to havethe powered device repaired.

Configuration versatilityExternally powered electronic products can be used withdifferent power sources as needed (e.g. 120VAC, 240VAC, 12VDC, or external

battery pack), for convenient use in the field, or when traveling.

Simplified product inventory, distribution, and certification An electronic productthat is sold and used internationally must be powered from a wide range of powersources, and must meet product safety regulations in many jurisdictions, usuallyrequiring expensive certification by national or regional safety agencies such asUnderwriters Laboratories orTechnischer berwachungsverein. A single version of adevice may be used in many markets, with the different power requirements met bydifferent external power supplies, so that only one version of the device need bemanufactured, stocked, and tested. If the design of the device is modified over time (afrequent occurrence), the power supply design itself need not be retested (and viceversa).

Problems

"Power brick" in-line configuration, with detachable AC cord

While useful for many purposes, some external AC adapters have attracted criticism.Problems with this type of power supply include, but are not limited to:

SizePower supplies which plug into the mains directly without using a plug on acable (true wall warts) are bulkier than bare plugs; sometimes they are too large to

plug into power sockets with restricted space, or into adjacent sockets on power strips. Weight Some AC adapters can be heavy, exerting excess weight on the power

socket (this depends on the socket design of the country in question). Some externalpower supplies are "power bricks" (also known as "line lumps") having a short ACcord so they can lie on the floor, thus relieving strain, at the expense of clutter. Otherwall-hanging types are made long and thin, minimizing the leverage of their weight
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vector that pulls the plug out, at the expense of exacerbating the size problem. Theweight for equipment that must be carried (e.g., for traveling) is not a disadvantage ofexternal supplies, as the alternative is an equally heavy internal supply; in many casesa single universal supply can replace several proprietary ones.

InefficiencySome idling power is wasted as the power supply is left running whenthe equipment power switch is off or the equipment is disconnected from the powersupply. In recent years it has become common for equipment with internal supplies toshare this problem due to the use of a "soft" power switch.

Confusion External power supplies are often generic and not clearly marked toidentify the equipment they are designed to power. It is very easy to separate powersupply and equipment, and can be difficult to re-match the many devices with their

power supplies. Compatibility problems There is no standardization of connectors; the same

connector is often used for different voltages, and for both DC supplies and AC-to-AC transformers. Incompatible voltage or polarity may be present on physicallyinterchangeable connectors. This easily leads to using the wrong power supply, which

can destroy equipment.

A survey of consumers showed widespread dissatisfaction with the cost, inconvenience, andwastefulness of the profusion of power adapters used by electronic devices.[3] Science fictionauthor and satirist Douglas Adams wrote an essay bemoaning the profusion and confusion of

power adapters, and calling for more standardization.[4]

Dangerous and unreliable adapters

Manufacturers of equipment supplied with AC adapters often supply replacements at highprices; this has encouraged the manufacture of compatible third-party aftermarketreplacements. These may be of satisfactory quality and performance at significantly lower

prices; but adapters are available, usually at very low prices and sometimes with unknownbrands, sometimes fraudulently marked with the name of a reputable manufacturer, whichhave various issues which can cause inadequate performance (e.g. poor regulation and ripple,maximum power capacity lower than specified, hot running), unreliability (e.g. overheatingto temperatures exceeding component ratings) and electrical and fire danger to users (e.g.insulation which frays with wear, lack of fuse).[5][6] Spurious marks of conformity tostandards may be present; in one case it was reported that "Chinese manufacturers weresubmitting well-engineered electrical products to obtain conformity testing reports, but thenremoving non-essential components in production to reduce costs".[5]A test of 27 chargers

found that all the eight legitimately branded with a reputable name met safety standards, butnone of those unbranded or with minor names did, despite bearing the mark ofconformity.[5]
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Efficiency[edit]

Millions of still-usable AC power adapters are thrown out annually, because of poor or

unknown compatibility with new equipment.

The issue of inefficiency of some power supplies has become well known, with US presidentGeorge W. Bush referring in 2001 to such devices as "Energy Vampires".[7] Legislation is

being enacted in the EU and a number of U.S. states, to reduce the level of energy wasted bysome of these devices. Such initiatives include standby powerand the One Watt Initiative.

But others have argued that these inefficient devices are low powered, e.g., devices that areused for small battery chargers, so even if they have a low efficiency, the amount of energythey waste is less than 1% of household consumption of electric energy.[citation needed]

Considering the total efficiency of power supplies for small electronic equipment, the oldermains-frequency linear transformer-based power supply was found in a 2002 report to haveefficiencies from 2075%, and have considerable energy loss even when powered up but notsupplying power. Switched-mode power supplies (SMPSs) are much more efficient; a gooddesign can be 8090% efficient, and is also much smaller and lighter. In 2002 most external

plug-in "wall wart" power adapters commonly used for low-power consumer electronicsdevices were of linear design, as well as supplies built into some equipment.

External supplies are usually left plugged in even when not in use, and consume from a fewwatts to 35 watts of power in that state. The report concluded that about 32 billion kilowatt-

hours (kWh) per year, about 1% of total electrical energy consumption, could be saved in theUnited States by replacing all linear power supplies (average efficiency 4050%) withadvanced switching designs (efficiency 8090%), by replacing older switching supplies(efficiencies of less than 70%) with advanced designs (efficiency of at least 80%), and byreducing standby consumption of supplies to not more than 1 watt.[8]

Since the report was published, SMPSs have indeed replaced linear supplies to a great extent,even in wall warts. The 2002 report estimated that 6% of electrical energy used in the US"flows through" power supplies (not counting only the wall warts). The website where thereport was published said in 2010 that despite the spread of SMPSs, "today's power suppliesconsume at least 2% of all U.S. electricity production. More efficient power supply designs

could cut that usage in half".[9]
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Since wasted electrical energy is released as heat, an inefficient power supply is hot to thetouch, as is one that wastes power without an electrical load. This waste heat is itself a

problem in warm weather, since it may require additional air conditioning to preventoverheating, and even to remove the unwanted heat from large supplies.

Reuse[edit]

"Universal" DC power adapter, with a cigarette lighter power plug for obtaining power froman automobile.

AC adapters are often reused on other appliances, but there are 5 parameters which all mustsuit the appliance:

Voltage Current capacity Polarity (not relevant with AC) Voltage regulation (or stabilization) Connector type

"Universal" adapters are available[10]on which the user can adjust these parameters, exceptfor voltage regulation (which is a fixed characteristic of a given power supply design).

Universal power adapters[edit]
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A six-way connector on a "universal" DC power supply, consisting of a 4-way X connectorand two separate individual connectors (one is the nine-volt battery connector). The X-connector here provides 3.5 and 2.5 mm phone plugs and two sizes of coaxial powerconnector

External power adapters can fail, and can become separated from the product they areintended to power. Consequently there is a market for replacement adapters. The replacementmust match input and output voltages, match or exceed current capability, and be fitted with amatching connector. Many electrical products are poorly labeled with information concerningthe power supply they require, so it is prudent to record the specifications of the original

power supply in advance, to ease replacement if the original is later lost. Careful labeling ofpower adapters can also reduce the likelihood of a mixup which could cause equipmentdamage.

Some "universal" replacement power supplies allow output voltage and polarity to be

switched to match a range of equipment.[11] With the advent of switch-mode supplies,adapters which can work with any voltage from 110Vac to 240Vac became widely available;

previously either 100-120Vac or 200-240Vac versions were used. Adaptors which can alsobe used with motor vehicle and aircraft power input arae available.[12]

Four-way X connectors or six-way star connectors, also known as spider connectors, withmultiple plug sizes and types are common on generic power supplies. Other replacement

power supplies have arrangements for changing the power connector, with four to ninedifferent alternatives available when purchased in a set. RadioShack sells universal ACadapters of various capacities, branded as "Enercell Adaptaplug", and fitted with 2-pin femalesockets compatible with their Adaptaplug connector lineup. This allows many differentconfigurations of AC adapters to be put together, without requiring soldering. Philmore andother competing brands offer similar AC adapters with interchangeable connectors.

The label on a power supply may not be a reliable guide to the actual voltage it suppliesunder varying conditions. Many low-cost power supplies are "unregulated", in that theirvoltage can change considerably with load. If they are lightly loaded, they may put out muchmore than the nominal "name plate" voltage, which could damage the load. If they areheavily loaded, the output voltage may droop appreciably, in some cases well below thenominal label voltage even within the nominal rated current, causing the equipment beingsupplied to malfunction or be damaged. Supplies with linear (as against switched) regulators

are heavy, bulky, and expensive.

Modern switched-mode power supplies (SMPSs) are smaller, lighter, and more efficient.They put out a much more constant voltage than unregulated supplies as the input voltage andthe load current vary. When introduced, their prices were high, but by the early twentyfirstcentury the prices of switch-mode components had dropped to a degree which allowed evencheap supplies to use this technology, saving the cost of a larger and heavier mains-frequencytransformer.

Auto-sensing adapters

Some universal adapters, for example those by iGo,[13]

automatically set their output voltageand maximum current according to which of a range of interchangeable tips is fitted; tips are
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available to fit and supply appropriate power to many notebook computers and mobiledevices. Different tips may use the same connector, but automatically supply different power;it is essential to use the right tip for the apparatus being powered, but no switch needs to beset correctly by the user. The advent of switch-mode power supplies has allowed adapters towork from any AC mains supply from 100 to 240V with an appropriate plug; operation from

standard 12V DC vehicle and aircraft supplies can also be supported. With the appropriateadapter, accessories, and tips, a variety of equipment can be powered from almost any sourceof power.

A "Green Plug" system has been proposed, based on USB technology, by which theconsuming device would tell the external power supply what kind of power is needed.[14]

Use of USB[edit]

AC adapters capable of powering USB devices. Automotive 12 V DC models are also

available (not shown).

The USB connector (and voltage) has emerged as a de facto standard in low-power ACadapters for many portable devices. In addition to serial digital data exchange, the USBstandard also provides 5V DC power, up to 500 mA (900 mA over USB 3.0). Numerousaccessory gadgets ("USB decorations") were designed to connect to USB only for DC powerand not for data interchange. The USB Implementers Forum in March, 2007 released theUSB Battery Charging Specification which defines, "...limits as well as detection, control andreporting mechanisms to permit devices to draw current in excess of the USB 2.0specification for charging ..."[15] Electric fans, lamps, alarms, coffee warmers, batterychargers, and even toys have been designed to tap power from a USB connector. Plug-in

adapters equipped with USB receptacles are widely available to convert 120 V AC or 240 VAC power or 12 V DC automotive power to 5 V DC USB power (see photo at right).

Portable USB battery packs deliver USB power from an internal battery, and is also chargedby a powered USB port when not in use. Most of these devices are sized to rechargesmartphones multiple times on its single charge, and even support higher current demands forfaster charging. USB battery packs is a viable alternative to spare batteries forsmartphones,which requires a complete shutdown of the device. The trend started with iPhones that made

batteries inaccessible to the user without special screw drivers.

There is a DIY Open Hardware battery-powered USB charger which can be built from akit.[16]
https://en.wikipedia.org/wiki/Universal_Serial_Bushttps://en.wikipedia.org/wiki/AC_adapter#cite_note-14https://en.wikipedia.org/wiki/AC_adapter#cite_note-14https://en.wikipedia.org/wiki/AC_adapter#cite_note-14https://en.wikipedia.org/w/index.php?title=AC_adapter&action=edit&section=9https://en.wikipedia.org/wiki/Universal_Serial_Bushttps://en.wikipedia.org/wiki/Digital_datahttps://en.wikipedia.org/wiki/USB_decorationhttps://en.wikipedia.org/wiki/USB_Implementers_Forumhttps://en.wikipedia.org/wiki/AC_adapter#cite_note-15https://en.wikipedia.org/wiki/AC_adapter#cite_note-15https://en.wikipedia.org/wiki/AC_adapter#cite_note-15https://en.wikipedia.org/wiki/Smartphoneshttps://en.wikipedia.org/wiki/Smartphoneshttps://en.wikipedia.org/wiki/IPhonehttps://en.wikipedia.org/wiki/Do_it_yourselfhttps://en.wikipedia.org/wiki/Open_Hardwarehttps://en.wikipedia.org/wiki/AC_adapter#cite_note-FriedmanMinty-16https://en.wikipedia.org/wiki/AC_adapter#cite_note-FriedmanMinty-16https://en.wikipedia.org/wiki/AC_adapter#cite_note-FriedmanMinty-16https://en.wikipedia.org/wiki/File:AC_USB_adapters_jeh.JPGhttps://en.wikipedia.org/wiki/AC_adapter#cite_note-FriedmanMinty-16https://en.wikipedia.org/wiki/Open_Hardwarehttps://en.wikipedia.org/wiki/Do_it_yourselfhttps://en.wikipedia.org/wiki/IPhonehttps://en.wikipedia.org/wiki/Smartphoneshttps://en.wikipedia.org/wiki/Smartphoneshttps://en.wikipedia.org/wiki/AC_adapter#cite_note-15https://en.wikipedia.org/wiki/USB_Implementers_Forumhttps://en.wikipedia.org/wiki/USB_decorationhttps://en.wikipedia.org/wiki/Digital_datahttps://en.wikipedia.org/wiki/Universal_Serial_Bushttps://en.wikipedia.org/w/index.php?title=AC_adapter&action=edit&section=9https://en.wikipedia.org/wiki/AC_adapter#cite_note-14https://en.wikipedia.org/wiki/Universal_Serial_Bus


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Standards

The trend towards more-compact electronic devices has driven a shift towards the micro-USBand mini-USB connectors, which are electrically compatible in function to the original USBconnector but physically smaller. In 2009, the International Telecommunication Union (ITU)

announced support of the Open Mobile Terminal Platform's (OMTP) "Common Chargingand Local Data Connectivity" standard which specifies the use of micro-USB receptacles onmobile phones and standard USB receptacles on (common / interchangeable) chargers.[17]The hope is to markedly reduce the profusion of non-interchangeable power adapters neededfor each year's new output of mobile phone models.

The European Union defined a Common External Power Supply for "hand-held data-enabledmobile phones" (smartphones) sold from 2010, intended to replace the many incompatible

proprietary power supplies and eliminate waste by reducing the total number of suppliesmanufactured. Conformant supplies deliver 5V via a micro-USB connector, with preferredinput voltage handled ranging from 90 to 264 V.

Larry Page, a founder of Google, proposed a 12 V and up to 15 A standard for almost allequipment requiring an external converter, with new buildings fitted with 12V DC wiring,making external AC-to-DC adapter circuitry unnecessary.[18][19]

How an AC Adapter Works

AC vs. DC

o To understand how an AC adapter works, first understand the two main electricalcurrents people use. Alternating Current (AC) is an electrical current generated from amain source that flows two ways; it flows back and forth along an electrical line orwire. Direct Current (DC) flows only one way at a time and the energy typically losesstrength after it moves. To safely contain or direct energy to use in a householdappliance, for example, people need to have the AC turned into DC.

Current Electricity "101"

o Naturally occurring forces in the universe can cause particles to move. One of theseforces is "electromagnetism." This phenomenon is the reason why charged particlescan also make electric current, such as lightning, but people cannot use lightning as it

is too unpredictable. To make man-made electricity, one need only have a powersupply to redirect nature's electromagnetic field to generate either alternating or directcurrent. Some experts regard electricity as "temperamental," so you need a device tomaintain this energy interflow safely.

oElectrical Gadgets

o To make an electrical gadget work, you have to direct electricity into it, and keep itthere until you do not want to use it anymore. Power stations generally send

alternating current through power lines. It is the easiest way to send energy to a home,apartment or office building. Most devices utilize direct current. A transformer is
https://en.wikipedia.org/wiki/Micro-USBhttps://en.wikipedia.org/wiki/Mini-USBhttps://en.wikipedia.org/wiki/International_Telecommunication_Unionhttps://en.wikipedia.org/wiki/Open_Mobile_Terminal_Platformhttps://en.wikipedia.org/wiki/AC_adapter#cite_note-17https://en.wikipedia.org/wiki/AC_adapter#cite_note-17https://en.wikipedia.org/wiki/AC_adapter#cite_note-17https://en.wikipedia.org/wiki/European_Unionhttps://en.wikipedia.org/wiki/Common_External_Power_Supplyhttps://en.wikipedia.org/wiki/Smartphoneshttps://en.wikipedia.org/wiki/Larry_Pagehttps://en.wikipedia.org/wiki/Googlehttps://en.wikipedia.org/wiki/AC_adapter#cite_note-GooglePower-18https://en.wikipedia.org/wiki/AC_adapter#cite_note-GooglePower-18https://en.wikipedia.org/wiki/AC_adapter#cite_note-GooglePower-18https://en.wikipedia.org/wiki/AC_adapter#cite_note-GooglePower-18https://en.wikipedia.org/wiki/AC_adapter#cite_note-GooglePower-18https://en.wikipedia.org/wiki/Googlehttps://en.wikipedia.org/wiki/Larry_Pagehttps://en.wikipedia.org/wiki/Smartphoneshttps://en.wikipedia.org/wiki/Common_External_Power_Supplyhttps://en.wikipedia.org/wiki/European_Unionhttps://en.wikipedia.org/wiki/AC_adapter#cite_note-17https://en.wikipedia.org/wiki/Open_Mobile_Terminal_Platformhttps://en.wikipedia.org/wiki/International_Telecommunication_Unionhttps://en.wikipedia.org/wiki/Mini-USBhttps://en.wikipedia.org/wiki/Micro-USB


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typically responsible for changing the voltage that runs from an outlet. A common ACadapter is also a type of transformer, but it does not change the amount of electricity,

just the direction in which it flows back and forth through a wire or adjoining devices.

2. In todays world most of the electronic appliances needs DC voltages from 3-12 Voltsfor operation. An adaptor is a device which is used to convert high AC voltages to

low DC voltage. Adaptors come in various shapes, sizes & configuration depending

on the use. In some cases adaptors are used to provide power to electronic appliances

like video games, modems etc and in some cases they are used to charge the primary

battery of the electronic device and also act as alternate power source like mobile

chargers, laptop chargers, cell chargers etc. A typical adaptor is shown in the figure

below.

3.

4.5. The left red knob changes the output voltage while the right one is used to change the

polarity of output voltage.

6. An adaptor works in these 3 simple steps:7. 1. AC voltage is stepped down using a Transformer8. 2. A rectifier circuit changes the AC signal to DC signal.9. 3. A capacitor filters the signal to smooth DC waveform.10. Internal Circuitry11.


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12.13.On removing the outer plastic body of the adaptor, glimpse of transformer and other

circuitry is shown in the image above.

14.

What Is the Function of an AC Adapter?

AC adapters provide power for your laptop

computer, cellphone, home telephone, and other small electronics.

1. Voltageo The AC adapter scales the 120 volts from your wall down to a voltage in the area of 6

to 18 volts using a small transformer. A transformer consists of two coils of wires


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interspersed around an iron core. By electromagnetic law, the ratio of the number ofcoil turns in one wire to the other will equal the ratio of the voltages in the two wires.

Rectifying

o After converting the power to the desired voltage level, the adapter converts the AC toDC using a setup called a rectifier. The rectifier uses a combination of diodes, one-way electronic components, to make constant DC power from alternating AC power.

oExample

o A 12-volt adapter performs the following steps. First, the 120 volts of AC power fromthe wall goes into one end of the transformer, which has 10 coil windings on the inputfor every 1 on the output, and induces 12-volt AC power. Next, the AC power goes

through a series of diodes and comes out as 12 volts DC, ready to power your laptop,your home telephone, or to charge your cellphone.

AC Adapter

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