How to Choose Right Bobbin for Switching Transformer?

— OUGE gives you an insight into bobbin

Bobbin, also called wire frame, is the main structure of the electrical transformer. In other words, the bobbin is the same as the human skeleton and is the primary form of the whole body. Nowadays, the transformer is widely used in every field, so bobbin has an irreplaceable role, like Mjolnir for Thor in marvel.

However, the classification of the bobbin is complicated, which makes it difficult for both the supplier and the demand side in a transaction. As long as the dimensions are slightly different, the existing molds can’t be used entirely. So, how to choose the right bobbin from a professional perspective?

Classification of Bobbin

Firstly, of course, you need to know how many kinds of bobbin there precisely, which bother you so much. The bobbin is generally classified according to the type of magnetic core (or iron core) used in power transformers, including EI, EE, EF, EPC, ER, RM, PQ, UU, etc., and each type can be distinguished according to the size of the magnetic core (or iron core), such as EE5, EE8, EE13, EE19, etc.

According to its shape, the bobbin is divided into vertical type and horizontal type. Also, bobbin also can be divided into two types: high frequency and low-frequency bobbin. The frequency mentioned here does not refer to the number of times of use, but the frequency of electric transformer changes. The unit is Hertz (Hz), KHz, MHz, and GHz usually used in the calculation. Moreover, according to the usage property of bobbin pin, it is divided into DIP and SMD.

The bobbin has many features, so it has various shapes. Regarding the EE-19 vertical bobbin of XUYI OUGE, there are at least a dozen of them.

Jason Lee, an expert of OUGE, the preeminent transformer manufacturer in China, says that “Some have different baffle heights, some have different winding slots, and even the most critical sizes, PIN and row spacing are different.”Therefore, the selection of the bobbin must be matched with the transformer. Simple structure can match a part of the newly developed mode, but the complicated moulds have to be remade. If the circuit board is forced to use an inappropriate bobbin, it can lead to safety issues.

Function of Bobbin

Provide winding space for copper wire in the transformer.
Fix the magnetic core in the transformer.
The wire way in the bobbin provides a path for winding in transformer production.
The metal pin in the frame is the brace of the winding copper. After soldering tin is connected with PCB plate, it can conduct electricity when the transformer works.
The baffle at the bottom of the frame can make the transformer and PCB plate that has a fixed effect. It provides a specific distance space for solder stack and PCB board; magnetic core and PCB board. At the same time, it can isolate the magnetic core and tin reactor to avoid poor pressure resistance.
The convex point, hollow point or chamfer in the bobbin can determine the direction or stitch sequence when the transformer is used.

How to Choose

Firstly, the power size of the product should be determined, and then search the AE of the magnetic core. Once the type of magnetic core is chosen, the bobbin can be found or assisted by the bobbin manufacturer according to the type and width of the magnetic core.
At this time, the transformer layout should also be taken into consideration. If the plate size is specified by the customer or the outer box, where space is insufficient, you can find relatively small bobbin with a tight layout, but the production process will take longer. If space is large enough, you can find a lengthened frame on the side to meet the safety regulations, which can save the baffle wall or sleeve, easy to be wound, mainly to save the cost.

Bobbin material must also meet the safety requirements of high- frequency power switching transformer. The distributed capacitance of the frame should be small to avoid reducing the self-resonant frequency of the switching power supply.

Select the pin number of the bobbin by the winding number of the transformer.

Choose vertical or horizontal bobbin in line with the size and height of the transformer.

Choose the PIN or SMD bobbin on the grounds of the circuit board design.

The bobbin plays a vital role in switching transformer, so the selection of proper bobbin requires professional knowledge and experience. For safety and reducing unnecessary consumption, it is best to find a specialized manufacturer for customization.

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