Overview of Power Adapters

A power adapter is a power supply conversion device for small portable electronic devices and electrical appliances. It is typically composed of components such as an outer casing, transformer, inductor, capacitor, control IC, and PCB board. Its working principle involves converting alternating current (AC) input into direct current (DC) output. In common terms, a power adapter is also referred to as an "external power supply."

Power adapters are primarily categorized into two major types:

Switching Power Supply
This type primarily utilizes modern electronic technology to control the on and off time ratio of a switching transistor, thereby maintaining a stable output voltage. The switching power supply in a power adapter is generally constituted by a Pulse Width Modulation (PWM) control IC and MOSFETs.

Advantages and Disadvantages of Switching Power Supplies:

Advantages: High efficiency, compact size, and the ability to operate within a wide voltage range.

Disadvantages: The circuit generates relatively more interference, and troubleshooting can be more difficult when faults occur.

Linear Power Supply
This type converts AC power through a transformer for voltage change, followed by rectification and filtering circuits to obtain an unstable DC voltage. For a power adapter to achieve a high-precision DC voltage, it must further adjust the output voltage through a voltage feedback circuit.

Advantages and Disadvantages of Linear Power Supplies:

Advantages: Mature technology, simple circuit design, and absence of the interference and noise associated with switching power supplies.

Disadvantages: The voltage feedback circuit operates in a linear state, resulting in high power dissipation in the regulating transistor and low conversion efficiency. Additionally, the use of inductive transformers makes the device relatively heavy.

Power adapters are a type of power product with extremely widespread application. Their application domains already extensively cover various electronic equipment such as: security cameras, set-top boxes, routers, LED light strips, massagers, laptops, and printers. The application of power adapters is particularly prevalent in the security industry and consumer electronics.

Within consumer electronics, the output power provided by adapters is mostly within 100 watts, and market demand is growing rapidly. Applications include electric bicycle battery chargers, small-sized LCD TVs, laptops, printers, DVD players, and set-top boxes. Early power adapters mostly used linear transformers. However, with consumer electronics demanding higher efficiency and wider input voltage ranges from power adapters, coupled with increases in the cost of copper, iron, and labor, the linear transformers originally inside such adapters have largely been gradually replaced by switching power supplies.

Can Protect Computers During Power Outages
A power adapter (AC to DC converter) converts AC to DC before supplying power to a computer. While the adapter itself does not protect the computer, computers contain a power storage unit (also known as a charger/battery), which can provide protection during power outages.

Capable of Automatically Detecting 100–240V AC (50/60Hz)
Power adapters are widely used with routers, cordless telephone systems, game consoles, language repeaters, portable audio players, laptops, mobile phones, and other devices. Most power adapters can automatically detect and adapt to 100–240V AC (50/60Hz).

Reduces the Size and Weight of the Host Device
As a power supply conversion device for small portable electronic devices and appliances, the power adapter externalizes the power supply, connecting to the host device via a cable. This design helps reduce the volume and weight of the host device. Only a very small number of devices and appliances have the power supply built into the host.

The "Nameplate" of a Power Adapter
The interior of a power adapter consists of a power transformer and a rectifier circuit. Every power adapter features a nameplate indicating specifications such as power rating, input/output voltage, and current. Particular attention should be paid to the input voltage range listed.