What is an AC adapter? Essential Guide to Power Conversion

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

An AC adapter is an external power supply capable of AC/DC power conversion and is usually housed in a black case. AC/DC refers to converting 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 the U.S

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

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

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

3. Which electronic devices require an AC adapter?

Generally, devices requiring 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, electrical power can be supplied to the electronic device or batteries charged. As will be described later under "Summary of advantages offered by using an AC adapter," AC adapters eliminate the need to install an internal power supply in the central unit of electronic devices. This makes it possible for users to carry devices powered by the main power supply or batteries.

Also, users wishing 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 can prepare a suitable AC adapter 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 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?

Various AC pins exist, from folding types to universal adapters whose pins can be configured with multiple outlets worldwide.

Our company has an extensive track record of supplying AC adapters to countries worldwide, 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), and 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 adapter's shape can be L-shaped, straight, or an inlet. Various shapes of AC adapters have emerged in recent years, depending on the side design of the primary 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
Round	Detachable AC-pins type (Can be configured in four directions)	Inlet-type

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:How does the AC adapter work, and what is its principle of operation?

The following link provides a detailed explanation of How the AC adapter works and its principle of operation.

https://en.unifive.com/faq/about_product/How+AC+Adapters+Work+A+Detailed+Explanation.html

7: Tips for Selecting the Best AC DC Power Adapter

How to Select an AC DC Power Adapter for a Longer Lifespan?

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

If you use an adapter with a rated output that is barely adequate over a long period, there may be other options than maximizing its shelf life.

When selecting an AC adapter, pay attention to the usage environment of the device you plan to power.

When selecting an adapter, it is essential to consider the operating environment's ambient temperature and whether there are external features for heat dissipation. Reducing the output is necessary when operating at high ambient temperatures.

Please look at the product specifications for the graph showing ambient temperature vs. power output reduction.

Choose the correct DC plug.

Click here for more information on DC plugs.

Ensuring AC Adapter Safety and Compliance

AC adapter safety is an essential factor for all buyers. Therefore, AC adapters must comply with safety standards and be tested and approved by a certification body.

Common AC adapter safety standards include international standards such as IEC 62368 and UL 62368 in the US. These standards establish requirements to minimize the risk of electric shock and fire.

Certification bodies exist to verify that AC adapters comply with safety standards. Typical certification organizations include UL (Underwriters Laboratories), CE (Conformité Européene), and FCC (Federal Communications Commission). Each country and region has this kind of safety certification organization. These agencies test AC adapters for safety and electromagnetic compatibility and decide whether to approve.

Consider the peak load of the devices when selecting an AC adapter.

Choosing an adapter that accounts for peak loads is essential for dental devices, printers, sewing machines, electric shavers, and massage equipment using DC motors. UNIFIVE offers AC adapters capable of handling peak currents up to twice the rated current for more than 10 seconds.

8: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 power voltage 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 significant enough to affect the device. Unfortunately, these "linear power supplies" utilized large transformers rated 10W and above, making the adapters large and heavy. This made it difficult for them to be physically supported by 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 requiring a stable voltage, this method could have been more efficient and resulted in a significant energy loss. Electrical power was consumed even when no load was present, and the loss was 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, the SMPS (switched-mode power supply), which contains a switching mechanism to regulate DC flow, became mainstream. It sought to address the issues confronted by linear power supplies described above.

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 more minor loss compared to linear power supplies. Also, high-frequency ripples can be easily removed.

Therefore, switching regulators are much more efficient than linear regulators, making adapters lighter and more compact. Some may wonder if using a small transformer has issues, but galvanic isolation in an SMPS transformer makes it highly safe.

The linear power supply circuit is designed to have a narrow range of input voltages (e.g., AC/95V105V) and usually contains a transformer suitable for frequencies from 50Hz to 60Hz. In comparison, switched-mode power supplies operate efficiently over an extensive range of input voltages and frequencies. They provide coverage from 100V/AC to 240V/AC and are compatible with almost all commercial power supplies worldwide.

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, 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, which 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 transmitting 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, which can supply up to 100W of standardized power, was proposed and has gradually gained popularity.

9: Summary of advantages offered by using an AC adapter

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

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.

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

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

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.

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

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

AC adapters facilitate the easy maintenance of devices.

Power supplies are more susceptible to output voltage spikes and heat generated by the device than other circuits 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 repairing each device separately.

AC adapters offer more convenience.

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