What is AC/DC Power Adapters — Desktop & Wall-Mount?

On this page, we explain what an AC/DC Power Adapters — Desktop & Wall-Mount is, including basic knowledge such as pin types and shapes, differences in enclosures, and the history and features of AC/DC Power Adapters — Desktop & Wall-Mounts, from the perspective of a power supply manufacturer specializing in AC/DC Power Adapters — Desktop & Wall-Mounts, in an easy-to-understand manner.

What is an AC Adapter?

More specifically, an AC adapter is an electronic device used with electrical Products (devices) that require power. Rather than drawing power directly from the main source, it converts the commercial power supply provided by power plants from AC to DC and adjusts the voltage as needed. In Japan, the commercial power supply voltage is 100V, with a frequency of 50Hz to 60Hz.

The internal circuit design of an AC adapter is very similar to that of a built-in power supply.

• See How does an AC adapter work? for an explanation of AC adapter circuits.
• See What is the role of an AC adapter? for an explanation of its function.
• See How to use and maintain an AC adapter for tips on extending its lifespan.

What electrical Products (devices) require an AC adapter?

Devices that require an AC adapter can be broadly divided into the following:

• Electrical Products (devices) without a built-in power source
• Battery-powered electrical Products (devices)

By plugging the AC adapter into an AC outlet and connecting the power, it can supply power to electrical Products (devices) or charge their batteries.

As described later in the summary of advantages of using AC adapters, adopting an AC adapter eliminates the need to install an internal power supply in the device itself, making it easier to carry devices powered either by the main supply or by batteries.

Additionally, if you want to supply power to the same electrical Products (device) from 100VAC, 240VAC, or from vehicle or aircraft power sources, preparing a compatible AC adapter enables broad usage. This eliminates the need to manufacture devices that can only be used with a specific power source.

Using an AC adapter also enhances safety. Commercial power supplies of 100V or 240V (100V in Japan), which can pose a fatal electric shock risk, are converted into safe low voltages, allowing devices handled by users to receive low-voltage power.

What types and shapes of AC pins are available?

AC pins range from foldable types to interchangeable types compatible with standards around the world. Our company has extensive experience supplying AC adapters globally and can provide AC pins tailored to the destination country.

The table below introduces the main types and shapes of AC pins.

Type A

Japan, USA, Canada, Mexico, parts of South America including Brazil, Taiwan, China (central and northern regions), parts of Thailand

Type A without pin holes (China certification type)

Round 2-pin

European countries and former European territories, South Korea, Vietnam, Cambodia, Indonesia, India, Egypt

Type O

Australia, New Zealand (Oceania), central and northern China, Argentina, Philippines

Type BF

United Kingdom, Hong Kong, Singapore, China, Malaysia

Features of the AC adapter body

Adapter shapes include L-shaped, straight type, and inlet type. In recent years, various AC adapter designs have appeared to match the design of the main device.

In addition to the above shapes, we also offer round-housing AC adapters.

Inlet-type AC adapters have three main types of AC input connectors: IEC60320-C1 (commonly called the "figure-8" type), IEC60320-C7 (also called the "figure-8" type), and 3-pole types such as IEC60325-C5 and IEC60320-C14.

Tips for selecting an AC adapter

Choosing an AC adapter that lasts longer

It is generally said that selecting a model with a rated output about 30% higher than required allows the AC adapter to last longer.

For example, if a device requires 60W of power, it is recommended to select a model with a rated output of 75W or more. Using an adapter continuously at its maximum rated capacity may shorten its lifespan.

Consider the operating environment

When selecting an AC adapter, consider its operating temperature range and whether external heat dissipation is available. If it will be used in high-temperature environments or under special conditions, please contact our sales department.

Select the correct DC plug

Choosing the correct DC plug is essential. An incorrect selection may prevent operation or cause unexpected accidents. Be sure to verify DC plug polarity (center positive or center negative) and EIAJ voltage classification. DC cable lengths also vary.

Consider the device's peak current

Devices using motors, such as dental equipment, printers, sewing machines, electric shavers, and massage devices, require adapter selection that accounts for peak current. Unifive offers AC adapters that support peak currents up to twice the rated current for 1 to 10 seconds.

Check product safety standards

The required safety standards and technical regulations vary depending on the type of device using the AC adapter. For example, medical devices require medical standards, and LED devices must comply with harmonic current standards. Additionally, AC adapters must meet the safety standards and technical regulations of the destination country. Efficiency standards such as DoE, ErP, and FCC must also be considered.

History of AC adapters

Part 1: Emergence and disadvantages of linear power supplies

Originally, AC adapters referred to linear power supplies (droppers) consisting of a transformer to lower the commercial power supply voltage, a rectifier to convert it to DC, and a filter to smooth ripple waveforms. These had significant ripple effects on devices. However, for ratings above 10W, large transformers were required, making the adapters bulky and heavy, and difficult to support when plugged into wall outlets.

The output voltage of linear AC adapters typically varies depending on the load. For devices requiring stable voltage, linear voltage regulators were added, but their efficiency was low, resulting in high losses and power consumption even under no-load conditions, with excess energy dissipated as heat.

Part 2: Emergence of switching power supplies

In the early 21st century, to overcome the disadvantages of linear power supplies, switching mode power supplies (SMPS) became mainstream.

Switching power supplies rectify the input AC voltage using a diode bridge rectifier, smooth it with an aluminum electrolytic capacitor, and transfer energy to the secondary side through rapid on/off switching. The high switching frequency allows for smaller transformers and reduced losses compared to linear types. High-frequency ripple can also be easily removed, making switching regulators far more efficient and enabling lightweight, compact designs.

Although some may question whether small transformers are safe, SMPS transformers use galvanic isolation to ensure safety.

Linear power supply circuits are designed for a narrow input voltage range (e.g., AC95V-105V) and typically use transformers suited for 50Hz or 60Hz. In contrast, switching power supplies operate efficiently over a wide range of input voltage and frequency, covering 100VAC to 240VAC and supporting commercial power supplies worldwide - so-called universal types.

However, switching power supplies are vulnerable to lightning-induced overload and ESR. Customers concerned about lightning strikes or wide temperature range usage are advised to choose models with robust ESR, ripple/noise countermeasures, surge protection, and temperature range design.

Part 3: Widespread adoption of USB AC adapters

In recent years, many portable devices have adopted USB connectors. In addition to data transmission, they can supply DC 5V output up to 500mA (up to 900mA with USB3.0). A wide variety of devices - from portable batteries and coffee makers to small lamps and alarm clocks - are now designed to receive power via USB connectors. In 2012, USB Power Delivery, standardizing power supply up to 100W, was proposed and has gradually become widespread.

Recently, AC adapters using GaN devices have appeared, enabling smaller and more portable Products.

Summary of advantages of using AC adapters

Our website briefly introduces the advantages and disadvantages of using AC adapters compared to direct AC power on the page Advantages and disadvantages of using AC adapters vs. direct AC power. Here, we summarize the advantages in more detail.

1: Safety

By adopting AC adapters, designers of electrical Products can design the main device without being subject to safety regulations imposed by the destination country.

2: Reduced heat in the main device power supply

Heat is a major enemy of electrical Products. Increased heat affects component lifespan and reliability and may cause malfunction of sensitive circuits. Using an external power supply eliminates heat generated by an internal power supply.

3: Reduced noise impact on the main device

Electrical noise that adversely affects sensitive circuits in the main device can be reduced. Since electrical noise decreases with the square of the distance, separating the power supply using an AC adapter helps reduce its impact.

4: Lighter weight and smaller size of the main device

Using an external power supply allows the main device itself to be made smaller and lighter.

5: Easier maintenance of the main device

Power supplies are more prone to failure compared to other circuits due to output spikes and heat. By externalizing the power supply, users can easily replace it in case of failure, eliminating the need to repair the entire device.

6: Improved convenience

Devices using AC adapters can support various voltages as needed.

(For example, by adopting a universal-type AC adapter, power can be obtained from outlets around the world without issues.)

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