What is the Design Principles and Considerations for High-Frequency Transformers?
The casing and bobbin are usually used for transformers to fix and protect the internal structure of the transformer. The transformer's bobbin is typically made of metal or plastic, with high strength and heat resistance. Its main function is to support the magnetic core and winding of the transformer and fix them in place. In addition, the transformer's bobbin can also be used to connect the input and output of the transformer and provide distribution of current and voltage. In some applications, larger clearances and edge distances are required to meet design requirements. The transformer's framework has a significant impact on the overall performance of the transformer, so special attention is required in designing and manufacturing transformers. Transformers have various design applications, such as flyback transformers, forward converters, half-bridge transformers, or full-bridge transformers, etc. However, in general, the following related parameters are considered in the design.
Leakage inductance: The leakage inductance of a transformer is generated because there is not complete coupling between the primary and secondary coils. Designers can reduce the value of leakage inductance by using different winding methods, such as wider winding windows, fewer winding turns, fewer stacking layers, or by using the sandwich winding method to cancel out the primary and secondary coils. However, the sandwich winding method will increase parasitic capacitance, which reduces efficiency, so special attention is needed in the design process.
Insulation and voltage resistance: This is crucial in the design of high-frequency transformers, and the voltage resistance or safety distance between the primary and secondary should be considered. The voltage resistance specifications of materials can be increased, or wire racks with sufficient safety distance can be used. If the space is limited, other insulation materials can be used, such as insulating tapes, insulating sleeves, shields, or impregnation processes to strengthen or overcome insulation between the primary and secondary windings. Generally, the simplest way is to add insulating tapes or insulating sleeves to achieve better insulation between the primary and secondary windings. Insulating tape is usually rated for 1500V AC, with 1-2 layers of tape. If a higher rating of 3000V AC is required, 2-3 layers are needed.
Interference shielding: When a transformer is in operation, interference problems often occur. Therefore, to solve this phenomenon, a copper foil layer is added to the outer layer when winding the wire package, and it is connected to the pin for grounding or an insulating tape can be added to the outermost layer of the iron core to increase the shielding effect.