Transformer is a device that uses the principle of electromagnetic induction to change the AC voltage. It refers to adding alternating voltage to the primary winding of the coil to generate alternating magnetic flux, and inducing the output voltage to the secondary winding, so as to transmit energy, transform voltage or signal electrical insulation. role of isolation. Transformers are used in electronic circuits and electronic equipment to become electronic transformers. High-frequency electronic transformers refer to electronic transformers whose operating frequency is higher than 20kHz. Why choose 20kHz as the limit? Because, 20kHz is the upper limit of the audio frequency, beyond which no audible noise can be heard.

    Today's power products are generally characterized by "light, thin, short, and small" and are developing towards miniaturization and portability. Electronic transformers must adapt to the volume and weight requirements of the user's power supply products. At the same time, the biggest feature of high-frequency electronic transformers is high frequency. From the working principle of the transformer, it can be known that increasing the working frequency can reduce the volume and weight of the transformer, realize the short, light and thin, thereby increasing the transmission power per unit volume or weight, and increasing the power density. In addition, the prices of raw materials for electronic transformers, core materials and conductive materials, have risen. Therefore, electronic transformers need to be reduced in size and weight, so as to reduce costs and increase weight and transmit power for better development.

    There are three points that can be learned from the following three points:

    1. Overall structure optimization

    In order to adapt to the increasingly thin and short electronic equipment, high-frequency electronic transformers can be developed from three-dimensional structures to planar structures, chip structures, and thin-film structures, thereby forming new generations of high-frequency electronic transformers. For example: planar transformers, chip transformers, thin film transformers. In terms of design, it is necessary to study the electromagnetic field distribution of various new structures, how to achieve the best optimal design, and various problems of multi-layer structures; in terms of production technology, it is necessary to study various new processing methods to ensure consistent performance It can also discuss the structure, design method, manufacturing process and application characteristics of air-core transformers. The computer is used to optimize and design the overall structure scheme, which can shorten the design time, reduce the amount of materials, shorten the production cycle and reduce the cost.

    2. Reduce the cost of magnetic core materials

    The magnetic core is the most critical component in high-frequency electronic transformers that work on the principle of electromagnetic induction. The main development direction of magnetic core materials is to reduce losses, widen the temperature range of use and reduce costs.

    Soft ferrite is the main magnetic core material used in high-frequency electronic transformers. The development direction is to develop new varieties with better performance and new processes to reduce costs. Compared with the traditional soft magnetic ferrite and soft magnetic alloy, its magnetic metal particles or films can be distributed in non-conductor and other materials, so that the high frequency loss is significantly reduced and the operating frequency is increased. The processing technology can either be processed into powder cores by hot pressing, or injection molded into complex-shaped magnetic cores by using current plastic engineering technology, which has the advantages of low density, light weight, high production efficiency, low cost, product repeatability and consistency. good features. Different ratios can also be used to change the magnetic properties. Examples of composite materials composed of soft ferrite and permalloy have been introduced above. Now, soft magnetic composite powder cores with operating frequencies above 10 kHz have been developed, which can replace soft ferrite in high-frequency filter inductors.

    According to the development requirements of the overall structure of high-frequency electronic transformers, the development direction of the magnetic core structure is planar magnetic core, chip magnetic core and thin-film magnetic core. Planar cores used to be transformed with the original soft ferrite cores, and now there are various low-height soft ferrite cores specially used for planar transformers. Various low-height soft magnetic composite cores may also be developed in the future. In addition to further compressing the planar magnetic core, the magnetic core of the chip transformer also has a chip magnetic core manufactured by the co-firing method.

    3. Development of coil structure

    The main development direction of the coil structure is the plane coil, the chip coil and the thin film coil.

    The three-dimensional structure of the high-frequency transformer coil, the wire material considers the skin effect and the proximity effect, and uses multi-stranded stranded wires, and sometimes flat copper wires and copper tapes are used. The insulating material is made of high-grade heat-resistant materials, in order to increase the allowable temperature rise and reduce the volume of the coil, and use double-layer and triple-layer insulated wires to reduce the size of the coil. The C-class insulated magnet wire, which uses nanotechnology to coat mica on copper wire, has been developed in China. It has been used in power frequency motors and transformers, and has achieved good results. It is estimated that it will also be used in high-frequency electronic transformers.

    Flat structure coils are made of copper foil wires, most of which are made of single-layer and multi-layer printed circuit boards, and some are made of copper foil with a certain pattern, which is folded multiple times. Insulation materials are generally B-class materials.

    Thin-film structure coil, the wires are made of copper, silver and gold thin films, which are made into comb-shaped, spiral-shaped, sports field-shaped and other patterns, and the insulating materials are H-class and C-class materials. It can be a multi-layer structure or a combination of several multi-layer coils, or several coils and several magnetic cores are overlapped.