The basic factors to be considered when selecting the magnetic core structure in the design of high-frequency transformer are as follows: reduce magnetic leakage and leakage inductance, increase the heat dissipation area of the coil, which is conducive to shielding, easy winding of the coil, convenient assembly and wiring, etc.

In the structural design of high frequency transformer core, the window area should be determined after considering various factors.In order to prevent electromagnetic interference from inside to outside and from outside of high frequency power transformers, some magnetic core structures have closed and semi-closed shells outside Windows.The closed shell has a good effect on shielding electromagnetic interference, but heat dissipation and wiring are very inconvenient, so wiring holes and air outlets must be left.Semi-closed shell, closed place plays the role of shielding electromagnetic interference, not closed place for wiring and heat dissipation.If the window is completely open, the wiring and heat dissipation are convenient, and the shielding effect of electromagnetic interference is poor.

The patch core

The basic structure of magnetic core includes:

(1) stack, usually by silicon steel or nickel steel sheet cut into E, I, F, O shape, stack into an iron core.

(2) ring core, by o-shaped lamination, also can be made of narrow long silicon steel, alloy steel tape winding.

(3) C - shaped iron core, this kind of iron core can avoid the ring core winding difficult shortcomings, by two C - shaped iron core butt.

(4) tin iron core, it is the magnetic core outside, copper wire in the ring, without the inconvenience of a structural form of coil, can reduce EMI.The disadvantage is the internal coil heat dissipation bad, high temperature rise.

Causes of inductance core loss: the loss of SMD inductance core mainly comes from two aspects: core loss and coil loss, and the loss of these two aspects needs to be judged according to its different circuit mode.Among them, the core loss is mainly because the alternating magnetic field in magnetic core material, its loss is generated by the operating frequency and the total magnetic flux swing (Δ B) function, will greatly reduce the conduction loss effectively.Coil loss is due to the energy loss caused by the change of magnetic energy, which will reduce the strength of the magnetic field when the power inductance current drops.Inductance core loss reduction method: first, the loss of inductance core will decrease with the increase of inductance core loss, but also will bring the same inductance core material flux surge.Thus, when the switching frequency rises above 500 kHz, the inductance core loss and winding ac loss can greatly reduce the allowable dc current in the inductance.The loss of the inductor core in the coil is mainly manifested in the loss of copper wire. Therefore, in order to reduce the loss of copper wire, the loss of the inductor core must be reduced when the loss of the inductor core rises until all losses are equal.A good case is one where the losses are stable and equal at high frequencies, allowing the output current from the magnetic structure.