Power equipment is used to achieve electric energy conversion and power transmission. It is a product with high technical content, wide knowledge and fast replacement. It has been widely used in industry, energy, transportation, information, aviation, aerospace, shipping, national defense, education, culture and other fields. In the information age, all the above industries are developing rapidly, and at the same time, more and higher requirements are put forward for the power supply industry. Such as energy saving, electricity saving, material saving, shrinking, weight reduction, pollution prevention, environmental improvement, reliability, safety, etc. This forces power supply workers to continuously explore 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 supply technology will drive the development of related technologies, and the development of related technologies in turn promotes the development of the power supply industry. At present, the dominant products in the power supply industry include various linear voltage-stabilized power supplies, AC/DC switching power supplies for communication, DC/DC switching power supplies, AC variable frequency speed-regulating power supplies, electrolytic electroplating power supplies, high-frequency inverter rectifier welding power supplies, medium-frequency induction heating power supplies, power operation power supplies, sine wave inverter power supplies, high-power high-frequency high-voltage DC voltage-stabilized power supplies, green lighting power supplies, chemical power supplies, UPS, reliable, efficient and low-pollution photovoltaic inverter power supplies, wind-solar complementary power supplies, etc. The technologies related to power supply include high-frequency conversion technology, power conversion technology, digital control technology, full-resonance high-frequency soft-switching 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, variable frequency speed regulation technology, intelligent monitoring technology, intelligent charging technology, microcomputer control technology, integration technology, network technology, various forms of drive technology and advanced process technology.