The seven kinds of magnetic cores that are often used in high frequency transformers are pot cores, RM cores, E cores, EC, ETD and EER cores, PQ cores, EP cores, and toroidal core
s. Magnetic core etc.
1. Pot-type magnetic core The bobbin and winding are almost completely wrapped by the core, resulting in a good EMI shielding effect; the size of the slot-type core conforms to the IEC standard and has good interchangeability in the manufacturing industry; a simple frame can be provided ( PIN) and PCB mounting skeleton (pin); Due to the shape of the pot design, the size of the core and other types is greater than the cost; Since its shape is not conducive to heat dissipation, it is not suitable for large power transformer applications.
2. EP core The three-dimensional structure of the circular central column of the EP core completely wraps the winding except for the end in contact with the PCB board, and the shielding is very good; The impact of the air gap formed by the contact surface when the core is assembled, and provides a larger volume and overall space utilization ratio.
3. EC, ETD and EER type magnetic cores These types of magnetic core structures are between E type and pot type. Like E-type magnetic cores, they can provide enough space to lead to a large part (for low voltage, high current switching power supply is now trending); the shape of the core heat is also very good; there is a cylindrical shape in the center column, Compared with a cuboid with the same cross-section, the length of the single-turn winding is reduced by 11%, resulting in an 11% reduction in copper loss. At the same time, the core can provide higher output power; at the same time, the central column is cylindrical, which is similar to the rectangular central column Than, also avoid damage to the winding insulation winding wire problem caused by rectangular edges and corners.
4. Compared with the tank type, the two symmetrical sides of the RM type magnetic core are cut off. This design is more conducive to heat dissipation and the size of the lead wire is larger; compared with the shape of the tank, it saves about 40% of installation Space; skeleton needle-free needle type, can install a pair of pliers; RM magnetic core can be made into a flat shape (current planar transformer or directly design the winding of the printed circuit board for the assembly of the magnetic core); although the shielding effect is not as good as that of the can Well shaped, but still good.
5. PQ core PQ core designed for switching power supply inductors and transformers. The PQ shape optimization design of the magnetic core volume, the ratio between the surface area and the winding area; the design enables the use of a small core to provide inductance and maximize the possible area; such a design, in a small transformer volume and weight, large output power, And occupy a small PCB installation space; a pair of clips can be used to fix; the design of the effective cross-sectional area also makes the core magnetic circuit more uniform, so the core structure is also smaller than the core structure design such as hot spots.
6. E-type magnetic core Compared with pot-type magnetic core, E-type magnetic core has lower cost and relatively simple assembly. The shape of the core is widely used now, but the disadvantage is that it cannot provide self-shielding; E-type magnetic core can be installed In different directions, it is also possible to apply several pay high power coverage. The core can be made into a flat shape, and now planar transformers are very popular core shapes; it is also possible to provide a skeleton without pins and pin types, because its heat dissipation is very good, and it can be used in superposition. Generally, power inductors and transformers are used core shape.
7. Toroidal core For the manufacturer, the toroidal core is economical, and its cost is the lowest among all kinds of magnetic cores compared with it; due to the use of the bobbin, the additional and assembly costs are equal to zero; when suitable Can be wound using a wire winder; it's also very well shielded.