High frequency transformer is the most important part of switching power supply. There are many topological structures in switching power supplies. For example, a half-bridge power conversion circuit. When working, two switching transistors are turned on in turn to generate a high-frequency pulse wave of 100kHz, which is then transformed through a high-frequency transformer to output alternating current. The ratio of the turns of each winding coil of the high-frequency transformer is determined How much is the output voltage.

       The most conspicuous in a typical half-bridge transformer circuit are three high-frequency transformers: the main transformer, the drive transformer and the auxiliary transformer (standby transformer). Each transformer has its own measurement standards in national regulations, such as the main transformer. As long as it is a power supply above 200W, the core diameter (height) must not be less than 35mm.

As for the auxiliary transformer, the core diameter of 16mm is sufficient when the power supply does not exceed 300W.

The improvement of efficiency is a common requirement of today's power supply and electronic equipment. Traditional transformers cannot meet the requirements of today's efficiency.

　　 This is because the magnitude of the transformer induced electric potential depends on how much the magnetic flux changes per unit hour, that is to say, the faster the magnetic flux changes, the greater the induced electric potential. Although the magnetic core of a high-frequency transformer is small and the maximum magnetic flux is not large, it works at high frequency and the magnetic flux changes fast, so it can generate sufficient electric potential when the magnetic core is small and the number of coil turns is small. The opposite.

　　The design and calculation of high-frequency and low-frequency transformer show that under the same power condition, the higher the frequency, the smaller the core and the fewer turns per volt. The design of a high-frequency transformer should first start with the magnetic core. Switching power supply transformer cores are mostly soft magnetic materials used in low magnetic fields. They have high permeability, low coercivity, and high resistivity. The magnetic permeability is high, and at a certain number of coil turns, it can withstand a higher applied voltage through a small excitation current. Therefore, under a certain output power requirement, the volume of the magnetic core can be reduced.