A power supply is a device that provides electrical energy. The power supply is called a power supply because

 it can convert other forms of energy into electrical energy.

Common power sources are dry batteries (DC) and household 110V-220V AC power sources. The power source 

is based on the principle of "magneto generated electricity", which is generated by renewable energy sources 

such as water power, wind power, ocean tides, dam water pressure difference, solar energy, and burning coal, 

oil residue, etc.

High quality power supplies generally have certification marks from multiple countries such as FCC, American UL, 

and Great Wall of China. These certifications are professional standards established by certification agencies for 

power supplies based on industry technical specifications, including production processes, electromagnetic 

interference, safety protection, etc. Products that meet certain indicators can only use certification marks on 

packaging and product surfaces after passing the application for certification, which has a certain level of authority.