What is an AC adapter?

This section contains basic information on AC adapters. This information has been laid out in a comprehensive and accessible manner, including the types and shapes of adapter pins, the shapes of adapter cases, the history of AC adapters up to the present, and the advantages offered by AC adapters.

1. What is an AC adapter in the first place?

An AC adapter is a type of external power supply capable of AC/DC power conversion that is usually housed in a black case. AC/DC refers to the conversion of alternating current (AC) to direct current (DC). The AC adapter is used to supply electricity to batteries in the case of most users, and it is sometimes called an "AC power supply," "adapter," "charger," or "battery charger."

2: Types of AC adapters commonly used in U.S

The pins and shape of an A-type AC adapter used in Japan and the United States More specifically, an AC adapter is an electrical component used for electronic devices that require electrical power to operate.

This electrical component does not draw the required power from the main power supply, but instead transforms the commercial power supply provided by power plants from AC to DC and converts its voltage accordingly.

In the case of Japan, the commercial power supply has a voltage of 100V and a frequency ranging from 50Hz to 60Hz. The design of the internal circuit of an AC adapter is very similar to the circuit design in built-in power supplies and internal power supplies.

3. Which electronic devices require an AC adapter?

Generally speaking, devices that require an AC adapter are divided into the following categories

  1. Electronic devices without a source of power
  2. Battery-operated electronic devices

By plugging the AC adapter into the AC power outlet and connecting the power supply, it is possible to supply electrical power to the electronic device or charge batteries. As will be described later under "Summary of advantages offered by using an AC adapter," using AC adapters eliminates the need to install an internal power supply in the main unit of electronic devices.This makes it possible for users to carry around devices powered either by the main power supply or batteries.

Also, for users who wish to supply electrical power to the same electronic device from 100V/AC or 240V/AC mains, or power outlets in the car and on airplanes, they can prepare a suitable AC adapter beforehand that caters to a wide range of settings. This eliminates the need for manufacturers to produce electronic devices that can only be operated using specific power supplies.

At the same time, the use of AC adapters can enhance safety. As the commercial power supply of 100V/240V (100V in the case of Japan) may cause instant death from electrocution, AC adapters can convert this to lower voltages that are safer and supply electrical power at these lower voltages to devices handled by users.

4: What are the types and shapes of AC pins?

A variety of AC pins exist, from folding types to universal adapters whose pins can be configured for use with various outlets in the world.

Our company has an extensive track record of supplying AC adapters to countries around the world, and we can cater to the standards for AC pins in different countries.

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

A-Type Japan, United States, Canada, Mexico, some South American countries such as Brazil, Taiwan, China (Central and Northern China), parts of Thailand. A-type without holes in pins (China standard certified type) 2 round pins European countries and former European territories, Korea, Vietnam, Cambodia, Indonesia, India, Egypt.
O-Type Oceanian countries such as Australia and New Zealand, North and Central China, Argentina, the Philippines BF-Type United Kingdom, Hong Kong, Singapore, China, Malaysia

5: What are the features of AC adapter units?

The shape of the adapter can be L-shaped, straight, or an inlet. AC adapters of various shapes have emerged in recent years depending on the side design of the main device.

In addition to AC adapters with the shapes listed above, our company also offers AC adapters with a round case in our lineup.

L-shaped Straight Folding AC-pins type

Detachable AC-pins type

(Can be configured in four directions)


Inlet-type AC adapters have three main types of AC input connectors, including IEC60320-C1 which is known as the pig nose adapter, IEC60320-C7 or the glasses-type adapter, as well as IEC60325-C5 and IEC60320-C14 which are 3-pole adapters.

6: Tips when deciding on an AC adapter

How to select an AC adapter that lasts longer

Typically, it is said that AC adapters will last longer if you select a model with a rated output that is 30% higher than what is required. For instance, if the device for which you are using the adapter requires 60W of power, it is recommended to select an adapter model with a rated output of at least 75W.

If you use an adapter with a rated output that is barely adequate over a long period of time, it may not be possible to maximize its shelf life.

Paying attention to the operating environment

When selecting an adapter, it is important to consider the ambient temperature of the operating environment and whether there are external features for heat dissipation. It is necessary to reduce the output when operating at high ambient temperatures.

Please refer to the product specifications for the graph of ambient temperature vs. power output reduction.

Selecting the correct DC plug

Click here for more information on DC plugs.

9: History of AC adapters

Part 1: The advent of linear power supplies and their disadvantages

Originally, AC adapters had emerged as linear power supplies (droppers) composed of a transformer for converting the voltage of power from commercial power supplies to lower voltages, a rectifier for converting it to DC, and a filter to smooth the pulsating waveform.

The ripple variations of these adapters were still large enough to affect the device. Unfortunately, these "linear power supplies" had utilized large transformers rated 10W and above, making the adapters themselves large and heavy, which posed difficulties for them to be physically supported at power outlets on the wall.

The output voltage of a "linear power supply" AC adapter usually varies depending on the load. Although a linear voltage regulator was added to the circuit for devices that require a stable voltage to operate, this method was inefficient and resulted in a significant loss of energy. Electrical power was consumed even when no load was present with the loss dissipated as heat.

Part 2: The advent of switched-mode power supplies

At the beginning of the 21st century, a new kind of power supply that had sought to address the issues confronted by linear power supplies described above became mainstream. This was the SMPS (switched-mode power supply), which contains a switching mechanism to regulate the flow of DC current.

In switched-mode power supplies, the input AC voltage is rectified by a diode bridge rectifier and smoothed by an aluminum electrolytic capacitor, before being transmitted to a secondary section via switching between full-on/full-off states using a switching element. The high frequency of this full-on/off switching allows for the use of smaller transformers and gives rise to a smaller loss as compared to linear power supplies. Also, high-frequency ripples can be easily removed.

Therefore, switching regulators are much more efficient than linear regulators, making it possible for adapters to become more lightweight and compact. Some of you may wonder if there are issues with using a small transformer, but the use of galvanic isolation in an SMPS transformer makes it extremely safe.

The circuit of a linear power supply is designed to have a narrow range of input voltages (e.g., AC/95V~105V) and usually contains a transformer suitable for frequencies in the range of 50Hz to 60Hz. In comparison, switched-mode power supplies operate efficiently over an extremely wide range of input voltages and frequencies. They provide coverage from 100V/AC to 240V/AC and are compatible with almost all commercial power supplies in the world.

In other words, they are the so-called universal adapters. However, as switched-mode DC-regulated power supplies are susceptible to overloading due to lightning and ESR, etc., users who wish to use these power supplies in an environment that may be exposed to lightning strikes or fluctuations over a wide range of temperatures are advised to select our company's models that have been designed to protect against ESR, ripples and noise, lightning surges, and large temperature fluctuations.

Part 3: The growing popularity of USB AC adapters

In recent years, USB connectors have been adopted for many portable devices. In addition to the transmission of data, these products can supply output power at DC 5V and up to a maximum of 500mA (or 900mA in the case of USB 3.0) to the device.

Many devices are now being designed to draw power from USB connectors, from portable batteries to coffee makers, small lamps, and alarm clocks. In 2012, the USB Power Delivery specification that can supply up to 100W of standardized power was proposed and has gradually gained popularity since.

10: Summary of advantages offered by using an AC adapter

While you can find an outline of the advantages and disadvantages of using an AC adapter in the "Advantages and disadvantages of using an AC adapter and directly using an AC power supply" page of our website, the following presents a detailed summary.

Part 1: AC adapters enhance safety.

Using an AC adapter allows designers of electronic devices to design the device itself without being restricted by safety-related legal regulations set forth by the countries in which the device will be sold.

Part 2: AC adapters can lower the temperature of the device's power supply.

Heat is the nemesis of electronic devices. High temperatures negatively affect the shelf life and reliability of electronic components, and may cause delicate circuits to malfunction. By switching to an external power supply, the heat generated by the device's built-in power supply can be dissipated.

Part 3: AC adapters can reduce the effect of noise on the device.

AC adapters can reduce electrical noise which may damage noise-sensitive circuits in the device. Since the magnitude of electrical noise is inversely proportional to the square of the distance, AC adapters can reduce the effect of noise by increasing this distance.

Part 4: AC adapters can make devices lighter, smaller, and more compact.

Using an external power supply allows the device to be made more compact.

Part 5: AC adapters facilitate the easy maintenance of devices.

Compared to other circuits, power supplies are more susceptible to output voltage spikes and heat generated by the device, and are thus prone to failure. Using an external power supply allows users to easily replace the power supply in the event of failure instead of having to repair each device separately.

Part 6: AC adapters offer more convenience.

Devices that utilize AC adapters are compatible with a wide variety of voltages. (For instance, by using a universal AC adapter, users can draw power from power outlets in different countries around the world with no issues.)

You can get the product catalog in PDF.

Product initiatives

Since 1989, UNIFIVE has maintained the quality of their AC power adapters and switching power supplies through rigorous quality controls.

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