AC adapter

We offer a clear and concise look into ac dc desktop adapter, helping readers grasp the essentials with ease.

Type of external power supply For other senses of this term, see Battery charger. "External Power Supply" redirects here. For the European standard, see Common external power supply. Not to be confused with Rectifier.

An AC adapter or AC/DC adapter (also called a wall charger, power adapter, power brick, or wall wart) is a type of external power supply, often enclosed in a case similar to an AC plug. AC adapters deliver electric power to devices that lack internal components to draw voltage and power from mains power themselves. The internal circuitry of an external power supply is often very similar to the design that would be used for a built-in or internal supply.

When used with battery-powered equipment, adapters typically charge the battery as well as powering the equipment.

Aside from obviating the need for internal power supplies, adapters offer flexibility: a device can draw power from 120 VAC or 230 VAC mains, vehicle battery, or aircraft battery, just by using different adapters. Safety can be another advantage, as hazardous 120 or 240 volt mains power is transformed to a lower, safer voltage at the wall outlet before going into the appliance handled by the user.

Modes of operation

Originally, most AC/DC adapters were linear power supplies, containing a transformer to convert the mains electricity voltage to a lower voltage, a rectifier to convert it to pulsating DC, and a filter to smooth the pulsating waveform to DC, with residual ripple variations small enough to leave the powered device unaffected. Size and weight of the device was largely 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 be physically supported by a wall outlet. The output voltage of these adapters varied with load; for equipment requiring a more stable voltage, linear voltage regulator circuitry was added. Losses in the transformer and the linear regulator were considerable; efficiency was relatively low, and significant power dissipated as heat even when not driving a load.

Early in the twenty-first century, switched-mode power supplies (SMPSs) became almost ubiquitous for this purpose due to their compact size and light weight relative to their power output ability. Mains voltage is rectified to a high direct voltage driving a switching circuit, which contains a transformer operating at a high frequency and outputs direct current at the desired voltage. The high-frequency ripple is more easily filtered out than mains-frequency. The high frequency allows the transformer to be small, which reduces its losses; and the switching regulator can be much more efficient than a linear regulator. The result is a much more efficient, smaller, and lighter device. Safety is ensured, as in the older linear circuit, because a transformer still provides galvanic isolation.

A linear circuit must be designed for a specific, narrow range of input voltages (e.g., 220–240 VAC) 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 and frequencies; a single 100–240 VAC unit will handle almost any mains supply in the world.

Many inexpensive switched-mode AC adapters do not implement adequate filtering and/or shielding for electromagnetic interference that they generate. The nature of these high speed, high-energy switching designs is such that when these preventative measures are not implemented, relatively high energy harmonics can be generated, and radiated, well into the radio portion of the spectrum. The amount of RF energy typically decreases with frequency; so, for instance, interference in the medium wave (US AM) broadcast band in the one megahertz region may be strong, while interference with the FM broadcast band around 100 megahertz may be considerably less. Distance is a factor; the closer the interference is to a radio receiver, the more intense it will be. Even WiFi reception in the gigahertz range can be degraded if the receiving antennae are very close to a radiating AC adapter. A determination of if interference is coming from a specific AC adapter can be made simply by unplugging the suspect adapter while observing the amount of interference received in the problem radio band. In a modern household or business environment, there may be multiple AC adapters in use; in such a case, unplug them all, then plug them back in one by one until the culprit or culprits is found.

Traditionally, wall adapters provided a constant voltage. For USB-powered devices, it is 5 volts. Later, battery charging protocols such as Quick Charge by Qualcomm and USB Power Delivery started allowing charged devices to request different voltages suited for their needs, usually higher voltages to increase power without adding heat to the copper wires of the USB cable. In the past, "SuperCharge" by Huawei and "Dash Charge" by OnePlus did the opposite, requesting a slightly lowered voltage to directly match the battery voltage inside the smartphone so no change of voltage has to take place inside the , leading to less heating up. This required special USB cables with thicker copper wires.

In the early s, the use of gallium nitride instead of silicon in switching wall adapters bumped up their output power at the same physical size, making compact wall warts able to power even some laptops, not only smartphones and tablet computers. The creation of Gallium Nitride chargers was delayed owing to their excessive costs and that fast charging technology was less in demand than it has become after .

Advantages

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

Safety – External power adapters can free product designers from worrying about some 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 necessity use dangerous mains voltage. If an external power supply is used (usually via a power connector, often of coaxial type), the equipment need not be designed with concern for hazardous voltages inside the enclosure. This is particularly relevant for equipment 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 reduction – Because radiated electrical noise falls off with the square of the distance, it is to the manufacturer's advantage to convert potentially noisy AC line power or automotive power to "clean", filtered DC in an external adapter, at a safe distance from noise-sensitive circuitry.
Weight and size reduction – Removing power components and the mains connection plug from equipment powered by rechargeable batteries reduces the weight and size which must be carried.
Ease of replacement – Power supplies are more prone to failure than other circuitry due 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 have the powered device repaired.

Configuration versatility – Externally powered electronic products can be used with different power sources as needed (e.g. 120 VAC, 240 VAC, 12 VDC, or external battery pack), for convenient use in the field, or when traveling.
Simplified product inventory, distribution, and certification – An electronic product that is sold and used internationally must be powered from a wide range of power sources, and must meet product safety regulations in many jurisdictions, usually requiring expensive certification by national or regional safety agencies such as Underwriters Laboratories (UL) or TÜV. A single version of a device may be used in many markets, with the different power requirements met by different external power supplies, so that only one version of the device need be manufactured, stocked, and tested. If the design of the device is modified over time (a frequent occurrence), the power supply design itself need not be retested (and vice versa).
Constant voltage is produced by a specific type of adapter used for computers and laptops. These types of adapters are commonly known as eliminators.

Problems

A survey of consumers showed widespread dissatisfaction with the cost, inconvenience, and wastefulness of the profusion of power adapters used by electronic devices.

Efficiency

The issue of inefficiency of some power supplies has become well known, with U.S. president George W. Bush referring in to such devices as "Energy Vampires". Legislation is being enacted in the EU and a number of U.S. states to reduce the level of energy wasted by some of these devices. Such initiatives include standby power and the One Watt Initiative.

But others [who?] have argued that these inefficient devices are low-powered, e.g., devices that are used for small battery chargers, so even if they have a low efficiency, the amount of energy they 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 older mains-frequency linear transformer-based power supply was found in a report to have efficiencies from 20 to 75%, and have considerable energy loss even when powered up but not supplying power. Switched-mode power supplies (SMPSs) are much more efficient; a good design can be 80–90% efficient, and is also much smaller and lighter. In most external plug-in "wall wart" power adapters commonly used for low-power consumer electronics devices were of linear design, as well as supplies built into some equipment.[citation needed]

External supplies are usually left plugged in even when not in use, and consume from a few watts 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 the United States by replacing all linear power supplies (average efficiency 40–50%) with advanced switching designs (efficiency 80–90%), by replacing older switching supplies (efficiencies of less than 70%) with advanced designs (efficiency of at least 80%), and by reducing standby consumption of supplies to not more than 1 watt.

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

Since wasted electrical energy is released as heat, an inefficient power supply is hot to the touch, 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 prevent overheating, and even to remove the unwanted heat from large supplies.

Universal power adapters

See also: DC connector and Coaxial power connector

External power adapters can fail, or can become separated from the product they are intended to power. Consequently, there is a market for replacement adapters. The replacement must match input and output voltages, match or exceed current capability, and be fitted with a matching connector. Many electrical products are poorly labeled with information concerning the 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 of power adapters can also reduce the likelihood of a mixup which could cause equipment damage.

Some "universal" replacement power supplies allow output voltage and polarity to be switched to match a range of equipment. With the advent of switch-mode supplies, adapters which can work with any voltage from 110 VAC to 240 VAC became widely available; previously either 100–120 VAC or 200–240 VAC versions were used. Adapters which can also be used with motor vehicle and aircraft power (see EmPower) are available.

Four-way X connectors or six-way star connectors, also known as spider connectors, with multiple plug sizes and types are common on generic power supplies. Other replacement power supplies have arrangements for changing the power connector, with four to nine different alternatives available when purchased in a set. This allows many different configurations of AC adapters to be put together, without requiring soldering. Philmore and other 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 supplies under varying conditions. Many low-cost power supplies are "unregulated", in that their voltage can change considerably with load. If they are lightly loaded, they may put out much more than the nominal "name plate" voltage, which could damage the load. If they are heavily loaded, the output voltage may droop appreciably, in some cases well below the nominal label voltage even within the nominal rated current, causing the equipment being supplied 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 and the load current vary. When introduced, their prices were high, but by the early 21st century the prices of switch-mode components had dropped to a degree which allowed even cheap supplies to use this technology, saving the cost of a larger and heavier mains-frequency transformer.

Auto-sensing adapters

Some universal adapters automatically set their output voltage and maximum current according to which of a range of interchangeable tips is fitted; tips are available to fit and supply appropriate power to many notebook computers and mobile devices. 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 be set correctly by the user. The advent of switch-mode power supplies has allowed adapters to work from any AC mains supply from 100 to 240 V with an appropriate plug; operation from standard 12 V DC vehicle and aircraft supplies can also be supported. With the appropriate adapter, accessories, and tips, a variety of equipment can be powered from almost any source of power.

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

Battery eliminator

A battery eliminator is an adapter intended to allow a device intended for battery operation, such as a radio, to be operated from an AC outlet.

All radios, except crystal sets, used inconvenient and messy vacuum tube batteries until the mid- to late-s. Battery eliminators that plugged into light sockets became very popular. Early commercial units were produced by the Edward S. Rogers, Sr. company in as a complement to its line of batteryless radios. Another early producer of battery eliminators was the Galvin Manufacturing Corporation (later known as Motorola), which was opened on September 25, by Paul Galvin and his brother Joseph E. Galvin. Eliminators became obsolete for radios after RCA introduced AC tubes in , enabling receivers to plug into household power. The industry rapidly adopted AC tubes, and companies which launched exclusively manufacture that product such as Philco had to quickly pivot to radio manufacturing to remain relevant and existent.

Laptop charger

In early laptop computers, the power supply units were internal like in desktop computers. To facilitate portability by sparing physical space and reducing the weight, power supply units were externalized.

When a laptop computer is operated while recharging, the integrated circuitry which controls the charging makes use of a power supply unit's remaining electrical current capacity. This allows supplying the device's components with power during usage while maintaining an uncompromised constant charging speed.

Use of USB

Standards

The ITU published Recommendation ITU-T L., "Universal power adapter and charger solution for mobile terminals and other hand-held ICT devices", which specifies a charger similar in most respects to that of the GSMA/OMTP proposal and to the European Common external power supply. The ITU recommendation was expanded and updated in June, . The hope is to markedly reduce the profusion of non-interchangeable power adapters.

The European Union defined a Common external power supply for "hand-held data-enabled mobile phones" (smartphones) sold from , intended to replace the many incompatible proprietary power supplies and eliminate waste by reducing the total number of supplies manufactured. Conformant supplies deliver 5 VDC via a micro-USB connector, with preferred input voltage handled ranging from 90 to 264 VAC.

In Larry Page, a founder of Google, proposed a 12 V and up to 15 A standard for almost all equipment requiring an external converter, with new buildings fitted with 12 VDC wiring, making external AC-to-DC adapter circuitry unnecessary.

IEC has created a standard for interchangeable laptop power supplies, IEC (full name "IEC Technical Specification : DC Power supply for notebook computer"), which was published on February 6, .

References

AC-DC power adapters are ubiquitous in our modern lives. We use them to power our laptops, smartphones, tablets, and other electronic devices. But what exactly is an AC/DC power adapter and how does it work?

In this blog post, we'll take a closer look at the basics of AC and DC power adapters. We'll explain what they are, how they work, and the different types of adapters available.

What Is An AC-DC Power Adapter?

An external power supply called an AC-DC power adapter, also known as an AC/DC converter or charger, transforms alternating current (AC) from a wall socket into the direct current (DC) required by electronic equipment. It makes it possible to power gadgets without using batteries or other power sources. Electrical components are powered by AC adapters, which come in a variety of types, voltages, and brands. They are frequently used with laptops, smartphones, gaming systems, and other portable electronics. Devices cannot be powered effectively or safely without AC adapters.

According to Extrapolate, the Global AC-DC Power Adapter Market is projected to be valued at $22.79 billion by , progressing at a 9.0% CAGR (compound annual growth rate). These s indicate that this industry is set up for rapid growth in the coming years.

What is AC Power?

Alternating current (AC) is the primary form of electricity that is supplied from the electrical grid to homes and businesses. It gets its name from the unique pattern followed by the flow of electrons. AC current is characterized by its periodic reversal of direction and fluctuating magnitude.

The voltage and frequency of AC power can vary from region to region. In the United States, for instance, the standard is 120 volts at a frequency of 60 Hz. However, across the Atlantic in the United Kingdom, 230 volts at a frequency of 50 Hz is the standard.

AC power is favored for electrical grid systems globally due to its ability to travel longer distances compared to DC power. The widespread use of AC power today is due to the groundbreaking work of visionaries like Nikola Te¬sla and Sebastian de Ferranti in the late 19th century.

What is DC Power?

Direct Current, abbreviated as DC, stands as an alternative form of electricity employed across a wide spectrum of applications. Unlike AC, the movement of electrons in DC power flows along a linear path. Devices such as batteries, solar cells, fuel cells, and alternators operate exclusively on DC electricity, distinguishing it from AC.

One notable advantage of DC power lies in its ability to provide a consistent voltage supply to electrical devices. However, DC power possesses a limitation in terms of transmission distance, making it impractical for utilization in electrical grid systems.

DC switchgear is a specialized type of electrical switchgear that is designed specifically for applications using direct current (DC). This type of switchgear is used to control and protect DC circuits and is essential for the safe and reliable operation of DC systems.

The majority of electronic devices prefer DC electricity due to its capacity for delivering "clean" power. Given that the primary form of electricity supplied to homes and businesses is AC power, the role of an AC-DC power supply is to affect the conversion of this electricity into DC power. The history of DC electricity traces back to the late 19th century and is intimately linked with the pioneering work of early electrical visionaries, prominently including Thomas Edison.

Why are there Two Distinct Types of Electrical Power?

Both AC and DC electricity exhibit their unique sets of advantages and limitations, which is why they continue to find equal utilization across diverse electrical applications. AC power excels in efficiently transmitting electricity over vast distances, rendering it highly suitable for distribution through mains grid systems.

How Does an AC/DC Power Adapter Function?

Let's delve into the workings of AC-DC power adapters and understand the distinctions between AC and DC power. AC cycles between positive and negative poles within an electrical circuit, repeatedly changing direction. This is the format used for delivering mains electricity. In contrast, DC maintains a steady flow without reversing direction. DC is employed for transmitting electricity along electrical pylons and powering various devices such as telecommunications equipment, vehicle batteries, and devices equipped with rechargeable batteries.

Typically, AC adapters comprise a compact central unit housing power-switching circuitry. This unit draws AC power from the mains and converts it into DC at the required voltage for the device. After this, a power cord transfers this converted electricity from the adapter to the device, either for battery charging or to enable its operation.

Similar to most of the electrical devices, AC adapters are designed to accommodate varying power levels, often expressed in Volts. They also feature a variety of plugs to fit different socket designs. For instance, the UK uses a different standard power plug than Europe.

Typically, AC/DC adapters are not universal and are compatible only with specific devices. However, some models function as versatile replacement chargers for a wide range of devices. These universal power supply adapters are designed to work with multiple voltage inputs within a specified range, such as 100-240 volts, and some even include various plug sizes, also referred to as star connectors or X connectors.

What is a Smart AC Power Adapter?

A smart AC adapter is a sophisticated power management solution that intelligently controls the power supply to a device. It has the capability to monitor the device's power consumption, optimizing and adjusting power delivery based on the device's specific requirements.

A smart power adapter charger can provide real-time monitoring of a device's power consumption and offer insights into its long-term power usage patterns. This information can be leveraged to fine-tune power delivery and consumption. Moreover, a smart AC power adapter enables customized power delivery according to a device's needs. For instance, it can supply more power during high-demand usage or reduce power delivery during idle periods.

What is Driving the AC-DC Power Adapter Industry?

The escalating demand for energy-efficient electronic devices is a pivotal driving force within the industry. Over the past two decades, the power supply sector has witnessed notable advancements, with a particular demand for AC-DC external plug-in power adapters tailored for low-voltage, high-current processor applications. To address the limitations of traditional electronic loads stemming from relatively low voltages, technologically enhanced power adapter converters have steadily emerged as the solution. Furthermore, recent innovations in the design of external plug-in power adapters have provided a substantial impetus to this field.

Moreover, significant technological advancements in the realms of medical devices and consumer electronics represent another crucial factor shaping the landscape. The demand for AC-DC power adapters is expected to witness a substantial uptick driven by substantial improvements in the consumer electronics sector. A multitude of ongoing research endeavors are dedicated to enhancing the reliability, precision, and cost-effectiveness of power adapters. It's worth noting that complying with new regulations and standards set forth by the US Department of Energy, which demand increased efficiency levels and updated limitations on no-load dissipation, poses a notable challenge for manufacturers throughout the value chain.

Winding Up

AC/DC power adapters play essential roles in our daily lives, bridging the gap between the electrical grid and our devices, and helping us stay connected. AC power's ability to travel long distances efficiently makes it ideal for widespread distribution, while DC power's reliability and precision cater to our electronic gadgets. The AC-DC power adapter is a reminder that in our quest for progress, even the smallest components can play a vital role.

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