Analysis of the Influence of Magnetic Core Shape of High Frequency Transformer on Transformer Operation

2019-05-14 14:07:52 JuKe Technology (DongGuan) Co., Ltd. Read

Analysis of the Influence of Magnetic Core Shape of High Frequency Transformer on Transformer Operation

 High-frequency cores are common in switching power supplies. When you face high-frequency cores of various shapes, can you explain how they differ?

High frequency transformer is a device that converts an alternating voltage, a current, and an impedance. When an alternating current is passed through the primary coil, an alternating magnetic flux is generated in the iron core (or the magnetic core) to induce a voltage (or current) in the secondary coil. . The transformer consists of a core (or core) and a coil. The coil has two or more windings. The winding connected to the power supply is called the primary coil, and the other winding is called the secondary coil. The core of the transformer includes a can core, an RM core, an E core, an EC, ETD and EER core, a PQ core, an EP core, an EP core, a toroidal core, etc. So, how do these cores affect the operation of the transformer? Please see the specific analysis below.

1, can type core
can type core.jpg

The skeleton and the winding are almost completely wrapped by the magnetic core, so that it has a very good shielding effect against EMI; the can core size is in accordance with the IEC standard, and the interchangeability is very good at the time of manufacture; the simple skeleton can be provided (no pin And PCB board mounting skeleton (with pins); due to the shape of the can shape, it is more expensive than other types of cores of the same size; because its shape is not conducive to heat dissipation, it is not suitable for high power Transformer inductor.

 2, RM core
 RM core.jpg

Compared with the can type, the two symmetrical sides of the can type are cut off. This redesign is more conducive to heat dissipation and large-sized lead extraction. Compared with the can shape, it saves about 40% of the installation space; Needle type and pin type; can be mounted with a pair of clips; RM type core can be made into a flat shape (suitable for the current planar transformer or directly assembled to the printed circuit board circuit with the windings already designed) Although the shielding effect is not as good as the can type, it is still good.

 3, E core
E core.jpg

Compared with the can core, the cost of the E core is much lower, and the 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-core can be installed in different directions, or it can be applied with a larger amount of power; this core can be made into a flat shape (which is the popular core shape of planar transformers now); it can also provide needle-free and plug-in Needle-type skeleton; because of its very good heat dissipation and can be used in combination, generally high-power inductors and transformers use magnetic cores of this shape.

 4. EC, ETD and EER cores
EC, ETD and EER cores.jpg

These types of core structures are between the E and the cans. Like the E-core, they provide enough space for large-section lead-outs (suitable for low-voltage, high-current currents in switching power supplies); these shapes also have very good core heat dissipation; they are cylindrical in the center column and are identical Compared with the rectangular parallelepiped, the length of the winding of the single turn is shortened by 11%, which causes the copper loss to be reduced by 11%, and the core can provide a higher output power; while the central column is cylindrical and the center of the cuboid Compared with the column, the hidden danger of breaking the insulation of the winding wire due to the rectangular corners during winding is also avoided.

 5, PQ core
PQ core.jpg

The PQ core is specifically designed for inductors and transformers for switching power supplies. The PQ shape design optimizes the ratio between core volume, surface area and winding area; this design allows for maximum output power and minimal footprint at minimum transformer volume and weight. PCB mounting space; can be mounted and fixed using a clip; this effective design also makes the magnetic core cross-sectional area more uniform, so this core structure also makes it less than other core structure designs. Work hotspots.

 6, EP type core
EP type core.jpg

The circular center column of the EP type core has a three-dimensional structure. In addition to the end that is in contact with the PCB board, the winding is completely wrapped and the shielding is very good; this unique shape minimizes contact during assembly of the two cores. The effect of the air gap formed by the face and provides a greater ratio of volume to total space utilization.

 7, toroidal core
toroidal core.jpg

For the manufacturer, the toroidal core is the most economical, and its cost is the lowest among the various cores that can be compared; the cost of the additional and assembly is equal to zero due to the use of the skeleton; The wire machine is wound; its shielding is also very good.