Ring-core transformers are a major type of electronic transformers, featuring high electrical efficiency, a solid core with no air gap, a stacking factor of up to 95% or more, minimal leakage flux, and low electromagnetic radiation. They have a small physical size and light weight, adapt to the core size, have very low iron loss, and a low core temperature rise. They are widely used in home appliances and other electronic devices with high technical requirements, primarily as power transformers and isolation transformers. Ring-core transformers are already available in a complete series internationally, and are extensively used in computers, medical equipment, telecommunications, instruments, and lighting.