The two major technologies of AC-DC power adapters - PFC technology and isolation technology

I. Power Factor Correction (PFC) technology Passive PFC: Working principle: Use a filter composed of passive elements such as inductors and capacitors to shape the input current to make it close to a sine wave, thereby improving the power factor. Advantages: Low cost and high reliability. Disadvantages: The power factor improvement is limited and generally can only reach about 0.7 - 0.9. Active PFC: Working principle: By controlling the switching tubes in the control circuit, make the input current follow the change of the input voltage to achieve power factor correction. Active PFC can increase the power factor to above 0.99 and significantly reduce harmonic pollution to the power grid. Advantages: High power factor, low harmonic content, and high efficiency. Disadvantages: High cost and complex circuit.

II. Isolation technology Transformer isolation: Working principle: Use the insulation isolation between the primary and secondary windings of the transformer to electrically isolate the input side and output side circuits. Transformer isolation can effectively prevent high voltage and interference signals on the input side from being transmitted to the output side, ensuring the stability and safety of the output DC power. Advantages: Good isolation effect and high reliability. Disadvantages: Large volume and high cost. Optocoupler isolation: Working principle: Isolate and transmit the signals on the input side and output side through an optocoupler. Optocoupler isolation has the advantages of fast response speed, high isolation voltage, and strong anti-interference ability. Advantages: Small volume, low cost, and good isolation performance. Disadvantages: Relatively low transmission efficiency.