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A linear power supply is a traditional power solution that achieves stable DC output through linear regulation.
The core working principle of a linear power supply can be divided into two steps: First, a mains frequency transformer steps down the 220V AC to the required voltage, which is then converted into rough DC via a rectifier and filter circuit; subsequently, the linear regulator (a power transistor operating in its linear amplification region) acts as a dynamic variable resistor. By continuously comparing the output voltage with a reference voltage, it automatically adjusts its own voltage drop to absorb excess energy, ultimately delivering a highly stable and clean DC output.
The main advantage of this solution is its excellent output characteristics: extremely low ripple and noise (typically below 1mV), no high-frequency interference from switching power supplies, virtually zero electromagnetic radiation, simple circuit structure, high reliability, and fast dynamic response. However, its inherent disadvantages are lower conversion efficiency and larger size. Based on its "clean" yet "inefficient" nature, linear power supplies are mainly used in medical equipment, industrial control, audio and testing, and small household appliances.
Our switching power supplies utilize Pulse Width Modulation (PWM) and high-frequency switching conversion technology, controlled by precision circuits, to achieve efficient power conversion and precise regulated output. The product series includes compact rail power supplies, open-frame board power supplies, enclosed waterproof power supplies, and other types to meet different installation environment requirements.
▶ Core Topologies: Utilizing mature and reliable advanced topologies such as Flyback, Forward, Half-Bridge/Full-Bridge, and LLC Resonant, optimized for efficiency and cost across different power ranges.
▶ Key Components: MOSFETs and controllers from world-class brands (e.g., Infineon, TI, STM), paired with high-performance high-frequency transformers and low-ESR solid-state capacitors, ensuring product reliability and long lifespan from the source.
▶ Precision Control & Protection: Built-in precision feedback loops ensure low ripple noise and high load/line regulation for clean output. Equipped with comprehensive protection functions including Overload (OLP), Overvoltage (OVP), Short Circuit (SCP), and Overtemperature (OTP) protection, ensuring safety for both the power supply and end equipment.
▶ Design & Compliance: Product designs comply with international safety and EMC standards such as UL, CE, CB, RoHS, etc. Some models meet stringent requirements such as Industrial Grade (Class I, Div 2) or Medical (BF type).
The Core Role of AC/AC Adapters
1. Voltage Transformation: This is the most direct function. It steps down the mains high voltage (e.g., 220V AC in China, 110V AC in the USA) to a safe low voltage required by the equipment (such as the 16.5V, 9V, 18V you mentioned).
2. Electrical Isolation: This is the most critical and important safety function of AC/AC adapters. It uses an internal transformer to completely isolate the input side (primary coil) from the output side (secondary coil) electrically through electromagnetic induction. The output side voltage has no potential difference with earth ground. Even if you accidentally touch one end of the output wire, no circuit is formed with ground, thus avoiding electric shock risk and greatly enhancing the safety of device usage. Isolation effectively blocks surges, voltage spikes, and noise interference from the mains grid, providing a "clean" power source for downstream precision electronic equipment and extending device lifespan.
3. Design Legacy & Cost: For some well-established devices, the internal circuit board already integrates rectification, filtering, and DC-DC regulation modules. Continuing to use a simple and reliable AC/AC adapter can reduce the adapter's own cost.
▶ Thermal Consideration: Placing the heat-generating rectification and regulation circuits on the main board inside the device allows using the device's larger space and housing for heat dissipation, instead of concentrating all the heat in a small adapter.
▶ Interference Immunity: Simple mains frequency transformers are not sensitive to external electromagnetic interference and may be more reliable in certain noise-sensitive applications.
▶ Safety: For Class I appliances (metal enclosure requiring grounding), separating the power supply's "coarse adjustment" (step-down isolation) and "fine adjustment" (rectification regulation) is a classic and safe design approach.
Fundamental Differences from AC/DC Adapters
To better understand the role of AC/AC adapters, comparing them with AC/DC adapters is very effective:
| Feature | AC/AC Adapter | AC/DC Adapter |
| Output Current Type | Alternating Current (AC) | Direct Current (DC) |
| Core Component | Mains Frequency Transformer | Transformer + Rectifier Bridge + Filter Capacitor + (Regulation Circuit) |
| Nature | Isolation Step-Down Transformer | Switching or Linear Power Supply |
| Output Voltage Characteristics | Usually unregulated, voltage slightly varies with load | Usually regulated, output voltage stable at nominal value |
| Weight and Size | Heavy, Large (due to iron core and copper wire transformer) | Light, Small (especially switching supplies) |
| Efficiency | Relatively Low | Relatively High |
| Application Logic | "I only provide safe low-voltage AC; you handle rectification and regulation yourself." | "I directly provide the stable DC your device needs, ready to use." |
Some models are UL certified, complying with UL1310 safety standard (UL File No. E310452).
|
Model |
Input |
Output |
|||
|
V ac |
Hz |
A or W |
V ac |
VA |
|
| ETL-AA025x-W165152 |
120 |
60 |
0.3A |
16.5 |
25 |
| ETL-AA025x-W090277 |
120 |
60 |
0.3A |
9.0 |
25 |
| ETL-AA020y-W090223 |
120 |
60 |
0.3A |
9.0 |
20 |
| ETL-AA040x-W165240 | 120 | 60 | 50W |
16.5 |
40 |
| ETL-AA050X-W165300 | 120 | 60 | 0.50A |
16.5 |
50 |
| ETL-AA0502-W180278 | 120 | 60 | 0.59A |
18 |
50 |
Note: x=1,2,3 or 4; y=1, 2, 3, 4, A, B, C or D
Our switching power supplies serve as the "power heart" for the following fields, providing stable and clean DC power:
▶ Industrial Automation: Control power for PLCs, servo drives, stepper motors, industrial robots, sensors, I/O modules, touchscreen HMIs.
▶ Communication & Network Infrastructure: 5G base stations, routers, switches, servers, optical transceivers, data center backup power systems.
▶ Smart Manufacturing & Mechanical Equipment: CNC machines, laser engravers, 3D printers, packaging machinery, textile machinery, production line equipment.
▶ Smart Buildings & Security: Access control systems, intercoms, video surveillance (CCTV), alarm systems, LED lighting drivers.
▶ Medical & Laboratory Equipment: Medical diagnostic equipment, patient monitors, laboratory analytical instruments (requires medical certified models).
▶ Transportation & New Energy: Railway electronic systems, electric vehicle charging facilities, photovoltaic monitoring systems, UAV ground stations.
