How to choose high frequency transformer core

2019-05-31 11:46:56 JuKe Technology (DongGuan) Co., Ltd. Read

How to choose high frequency transformer core

When designing a High frequency transformer,the basic factors to be considered in selecting the core structure are: reducing leakage and leakage inductance, increasing the heat dissipation area of the coil, facilitating shielding, easy coil winding, and convenient assembly and wiring.

In the design of the high-frequency transformer core structure, the window area is determined by considering various factors. In order to prevent electromagnetic interference from the inside and outside of the high frequency power transformer and from the outside to the inside, some core structures have a closed and semi-enclosed outer casing outside the window. The closed casing shields electromagnetic interference, but the heat dissipation and wiring are very inconvenient. There must be a wiring hole and an air outlet. Semi-enclosed enclosure, sealed to shield electromagnetic interference, unclosed for wiring and heat dissipation. If the window is completely open, wiring and heat dissipation are convenient, and shielding electromagnetic interference is poor.
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Patch core

The basic structure of the core is:

1 lamination, usually cut from silicon steel or nickel steel sheet into E, I, F, O and other shapes, stacked into a core.

2 annular core, which is made up of O-shaped sheets, and can also be wound by narrow-length silicon steel and alloy steel strips.

3C-shaped iron core, this kind of iron core can avoid the shortcoming of the winding of the toroidal iron core, and is formed by docking two C-type iron cores.

4 can iron core, which is a structure in which the core is outside and the copper coil is inside, which eliminates the inconvenience of the toroidal coil and can reduce EMI. The disadvantage is that the internal coil has poor heat dissipation and a high temperature rise.

The reason for the loss of the inductor core is that the loss of the chip inductor core is mainly derived from the core loss and the coil loss, and the magnitude of the loss in these two aspects needs to be judged according to different circuit modes. Among them, the core loss is mainly caused by the alternating magnetic field in the core material, and the loss generated by it is a function of the operating frequency and the total flux swing (ΔB), which greatly reduces the effective conduction loss. The coil loss is due to the energy loss caused by the change in magnetic energy, which reduces the strength of the magnetic field when the power inductor current drops. The method of reducing the loss of the inductor core: First, the core loss generated in the inductor core will decrease the allowable copper loss as the inductor core loss rises, and will also bring about the same flux core material flux surge. Therefore, when the switching frequency rises above 500 kHz, the inductor core loss and winding AC loss can greatly reduce the allowable DC current in the inductor. Second, the loss of the inductor core in the coil is mainly manifested in the loss of the copper wire. Therefore, in order to reduce the loss of the copper wire, it must be reduced when the loss of the inductor core increases, and continues until the equal loss. The better case is that the losses are stable and stable at high frequencies and allow the output current to be obtained from the magnetic structure.