Power supply equipment is a product with high technology content, wide knowledge and fast update. Now it has been widely used in industry, energy, transportation, information, aviation, aerospace, shipping, national defense, education, culture and other fields. In the information age, the above-mentioned industries are developing rapidly. At the same time, more and higher requirements are put forward for the power industry. Such as energy saving, power saving, material saving, shrinkage, weight reduction, pollution prevention, environmental improvement, reliability, safety, etc. This forces the power supply workers to explore continuously in the process of power supply research and development, and use various related technologies to make qualified power supply products to meet the needs of all walks of life. Obviously, the development of power technology will drive the development of related technologies, which in turn promote the development of power industry. At present, in the power supply industry, the leading products include various linear regulated power supply, AC / DC switching power supply for communication, DC / DC switching power supply, AC variable frequency speed regulating power supply, electrolytic electroplating power supply, high frequency inverter rectifier welding power supply, medium frequency induction heating power supply, power operation power supply, sine wave inverter power supply, high power high frequency high voltage DC regulated power supply, green lighting power supply Chemical power supply, UPS, reliable, efficient and low pollution photovoltaic inverter, wind solar complementary power supply, etc. The technologies related to power supply include high-frequency conversion technology, power conversion technology, digital control technology, full resonance high-frequency soft switch conversion technology, synchronous rectification technology, highly intelligent technology, electromagnetic compatibility technology, power factor correction technology, protection technology, parallel current sharing control technology, pulse width modulation technology, frequency control technology, intelligent monitoring technology, intelligent charging technology Technology, microcomputer control technology, integration technology, network technology, various forms of driving technology and advanced technology.