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All colleagues unite and focus their efforts to write a new chapter of developmentDetailed Classification of Power Adapters and Their Pros and Cons
所属分类： Industry News
发布时间：2020-06-20
What is a power adapter? A power adapter, also known as an external power supply, is a voltage‑conversion device used to power small, portable electronic devices and appliances. Its function is to step down the 220‑volt mains voltage to a stable low voltage—typically between 5 and 20 volts—that these products can operate at, ensuring they function properly. It serves as the power‑supply unit for such devices and generally consists of a housing, a power transformer, and a rectifier circuit. Based on output type, adapters are classified as AC‑output or DC‑output; based on connection method, they are divided into wall‑mounted and desktop models. Below, we’ll examine the detailed classifications of power adapters along with their respective advantages and disadvantages.
I. Types of Power Adapters
Power adapter There are mainly two types: linear power supplies and switching power supplies.
1. A linear power supply steps down AC voltage using a transformer, then rectifies and filters it to produce an unregulated DC output. To achieve high‑precision DC output, the power adapter must employ a voltage‑feedback circuit to regulate the output voltage. Advantages: This technology is well‑established, the circuitry is simple, and it avoids the interference and noise typical of switch-mode power supplies. Disadvantages: The voltage‑feedback circuit operates in linear mode, resulting in significant power dissipation in the regulating transistor and low conversion efficiency; moreover, the use of an inductive transformer makes the device relatively heavy.
2. A switching power supply is a type of power supply that uses modern electronic technology to regulate the on‑off duty cycle of switching transistors, thereby maintaining a stable output voltage. Switching power supplies in power adapters typically consist of a pulse‑width modulation (PWM) control IC and MOSFETs. Advantages: high efficiency, compact size, and operation over a wide input voltage range. Disadvantages: relatively high electromagnetic interference with the power circuitry, and greater difficulty in troubleshooting when failures occur.
II. It can be confidently stated that the power adapter is both a transformer and a rectifier.
So, an adapter is essentially a transformer—something we should all understand. When 220V AC passes through the transformer and is stepped down, it then goes through a rectifier to become DC. This process involves energy losses, which are converted into heat; therefore, it’s perfectly normal for a power adapter to get warm. The transformer core is made of silicon steel laminations. Once current flows, magnetic flux is generated, and this flux induces forces between the laminations, producing a humming sound—this is perfectly normal. However, if the noise becomes excessively loud, that’s no longer normal, and there can be many reasons for it:
1. The AC voltage is unstable.
2. Chip damage.
3. Interturn short circuit.
4. Component failure.
III. Applications of Power Adapters
They are widely used in consumer electronics, with most offering output powers below 100 watts, and market demand is growing rapidly. Applications include electric‑bike battery chargers, small‑size LCD TVs, laptops, printers, DVD players, and set‑top boxes. In the early days, power adapters typically employed linear transformers; however, as consumer electronics increasingly demand higher efficiency and wider input voltage ranges—coupled with rising costs for copper, iron, and labor—linear transformers have largely been replaced by switch‑mode power supplies.
It’s easy to tell them apart based on their respective advantages and disadvantages. The key factors are size, weight, and the output voltage range. Transformer‑based designs step down the voltage using coils, followed by rectification and voltage regulation; they tend to be larger in size and offer stable performance, but suffer from higher transformer costs and a tendency to heat up. Switching‑mode power supplies, on the other hand, are compact and cost‑effective, though poorly manufactured components can fail easily. The main distinguishing criteria are size and weight, which show clear differences.