A high frequency transformer is a device that transforms AC voltage, current and impedance. When an AC current is passed through the primary coil, an AC magnetic flux is generated in the iron core (or magnetic core), which induces a voltage (or current) in the secondary coil . The transformer consists of an iron core (or magnetic core) and a coil. The coil has two or more windings. The winding connected to the power supply is called the primary winding, and the remaining windings are called the secondary winding. Transformer cores include pot cores, RM cores, E cores, EC, ETD and EER cores, PQ cores, EP cores, EP cores, Toroidal cores, etc. , Then what impact do these cores have on the transformer's work in Switch Mode Power?
01 Pot Cores
The bobbin and winding are almost completely wrapped by the magnetic core, resulting in a very good shielding effect on EMI; the size of the can-shaped magnetic core conforms to the IEC standard, and the interchangeability is very good when manufacturing; a simple bobbin (no pin is available) ) And PCB board mounting frame (with pins); due to the design of the tank shape, the cost is higher than other types of the same size magnetic core; because its shape is not conducive to heat dissipation, it is not suitable for high power Transformer inductor.
02 RM cores
Compared with the Pot Cores, the two symmetrical sides of the Pot Cores are cut off. This redesign is more conducive to heat dissipation and large-size lead leads; compared with the Pot Cores, it saves about 40% of the installation space; whether there is a skeleton Pin-type and pin-type; can be installed with a pair of clips; RM-type magnetic core can be made into a flat shape; although the shielding effect is not as good as the can-type, it is still good.
03 E cores
Compared with pot-shaped cores, the cost of E-shaped cores is much lower. In addition, winding and assembly are relatively simple. This core shape is now the most widely used, but its disadvantage is that it cannot provide self-shielding; The E-type magnetic core can be installed in different directions, and several pairs of superimposed applications can be used for higher power; this kind of magnetic core can be made into a flat shape (it is a popular core shape for planar transformers); it can also provide needleless and plug-in Needle-shaped bobbin; because of its very good heat dissipation and can be used in stacks, generally high-power inductors and transformers use this shape of core.
04 EC, ETD and EER cores
These types of core structures are between E type and pot type. Like E-shaped cores, they can provide enough space for large cross-section leads to lead out (suitable for the current trend of low-voltage and high-current switching power supplies); these shapes of cores also have very good heat dissipation; the central column is cylindrical, which is the same as Compared with the rectangular cross-section, the length of the single-turn winding is shortened by 11%, which reduces the copper loss by 11%, and at the same time enables the core to provide a higher output power; at the same time, the central column is cylindrical, and the center of the rectangular parallelepiped Compared with the column, it also avoids the hidden danger of damaging the winding wire insulation due to the rectangular parallelepiped edges and corners during winding.
05 PQ core
The PQ core is specially designed for inductors and transformers for switching power supplies. The design of the PQ shape optimizes the ratio between the magnetic core volume, surface area and winding area; this design allows this design to obtain the maximum output power under the smallest transformer volume and weight, and occupy the smallest PCB installation space; a pair of clips can be used for installation and fixing; this effective design also makes the magnetic core cross-sectional area more uniform, so this magnetic core structure also makes it less than other magnetic core structure designs Hot work.
06 EP type core
The EP-type magnetic core has a three-dimensional structure with a circular center column. Except for the end contacting the PCB board, the winding is completely wrapped, and the shielding is very good; this unique shape minimizes the contact between the two magnetic cores during assembly The effect of the air gap formed by the surface, and provides a larger volume and the ratio of total space utilization.
07 Toroidal core
For manufacturers, the toroidal core is the most economical, and its cost is the lowest among the comparable magnetic cores; due to the use of the skeleton, the additional and assembly costs are equal to zero; the winding can be used when appropriate Wire passing machine for winding; its shielding is also very good
The above is the analysis about the influence of the shape of the high-frequency transformer core on the work of the transformer.