Who are the manufacturers of high frequency transformers in the world?

A transformer is a product that uses the principle of electromagnetic induction. This product is very common in our lives. Basically, there are shadows of transformers on the sides of a large number of residential areas. The main function of transformers is to transfer current The voltage changes so that the current flowing into the residents' homes is a standard current. Transformers are divided into many categories according to their usage and structure, the most common of which is high-frequency transformers. FKS CoilS will introduce the structure of high-frequency transformers below.

In order to adapt to the increasingly thinner and smaller electronic equipment, one of the main development directions of high-frequency electronic transformers is from three-dimensional structures to planar structures, chip structures, and thin-film structures, thus forming new high-frequency electronic transformers from generation to generation: planar transformers, Chip transformers, film transformers. The development of the overall structure of high-frequency electronic transformers not only forms new magnetic core structures and coil structures, adopts new materials, but also brings new development directions to design and production processes. In terms of design, in addition to studying the electromagnetic field distribution of various new structures and how to achieve the best optimal design, various problems of multi-layer structures should also be studied. In terms of production technology, it is necessary to study various new processing methods, so as to ensure the consistency of performance and realize the mechanization and automation of processing technology.

In MHz-level high-frequency electronic transformers, air-core transformers are used in more and more application fields. Discussing the structure, design method, manufacturing process and application characteristics of the air-core transformer is also its research and development direction. In addition, research on high-frequency electronic transformers with new working principles such as piezoelectric transformers is also a development direction. After nearly ten years of research and development, piezoelectric transformers have been practically applied in some fields.

Using computer to optimize and design the overall structure scheme is one of the main development directions of various electronic devices, and of course it is also a main development direction of high-frequency electronic transformers. This can shorten design time, reduce material consumption, shorten production cycle, and reduce costs.

Core Material and Construction

The magnetic core is the most critical component in a high-frequency electronic transformer that uses soft magnetic materials and works on the principle of electromagnetic induction. The main development direction of magnetic core materials is to reduce loss, widen the temperature range of use and reduce cost. The main development direction of the magnetic core structure is how to form planar magnetic cores, chip cores and thin film magnetic cores with the best shape and size (parameters such as electromagnetic performance, heat dissipation, consumption and cost).

All kinds of soft magnetic materials are constantly being improved and developed to compete in the market of high-frequency electronic transformers.

Soft ferrite is the main magnetic core material used in high-frequency electronic transformers, and its development direction is to develop new varieties with better performance and new processes to reduce costs. In terms of new varieties of materials, Japan’s TDK Corporation developed PC95, a wide-temperature low-loss material in 2003, with a loss of less than 350mW/cm3 in the temperature range of 25°C to 120°C (under the condition of 100kHz×200mT). The loss is the smallest at 80°C, which is 280mW/cm3. At 25°C, Bs is 540mT, and at 100°C, Bs is 420mT. Also developed a high-temperature high-saturation magnetic density material PE33, the Curie point Tc>290 ℃, at 100 ℃, Bs is 450mT. Under the condition of 100 ℃, 100kHz×200mT, Pc≤1100mW/cm3, Japanese FDK company, German EPCOS company, Ferrocube company have also developed similar high temperature and high saturation magnetic density materials.

There are also many new varieties of high magnetic permeability materials, such as TDK's pulse transformer H5C5, μi is about 30,000. The anti-electromagnetic interference inductor uses HS10, which has good frequency characteristics and impedance characteristics. It still has a high magnetic permeability at 500kHz, although the initial magnetic permeability is not high, only about 10,000. High magnetic permeability and high saturation magnetic density material DN50, Bs is 550mT at 25°C, Bs is 380mT at 100°C, μi is about 5200, Curie temperature Tc≥210°C.

In terms of new technology, self-propagating high-temperature synthesis (SHS) is a research hotspot in recent years. Its principle is to use the chemical energy inside the reactants to synthesize materials. The whole process is extremely simple, with low energy consumption, high production efficiency and product purity, and no pollution to the environment. Mg, MgZn, MnZn, and NiZn ferrites have been successfully synthesized and are being industrialized. Spark plasma sintering (SPS) can successfully make multi-layer MnZn ferrite and permalloy composite soft magnetic material cores, which have the high frequency and low loss characteristics of MnZn ferrite and the high magnetic permeability of permalloy High-frequency saturation magnetic density characteristics, this composite soft magnetic material core will significantly improve the performance of high-frequency electronic transformers. Other processes such as self-combustion synthesis, rapid combustion synthesis, hydrothermal synthesis, new hydrothermal synthesis, mechanical alloying, microwave sintering, etc., have carried out a lot of research in recent years, all of which are in line with the development direction of improving performance and reducing costs .

Due to the low saturation magnetic density of soft magnetic ferrite, in the higher frequency range of 20kHz to 100kHz, the advantage of cost performance is not as obvious as in the high frequency range above 100kHz. In the frequency range, it competes fiercely with soft ferrite. Various soft magnetic materials have their own characteristics. Therefore, how to give full play to the advantages of various soft magnetic materials in specific high-frequency electronic transformer products to achieve better performance and price ratio is the soft magnetic material used in high-frequency electronic transformers. The development direction of magnetic materials.

Silicon steel is characterized by high saturation magnetic density, stable performance, and low price. In recent years, a series of high-frequency silicon steels have been developed, including ultra-thin strip silicon steel, 6.5% silicon steel, gradient silicon steel and chromium-containing silicon steel. Especially chromium-containing silicon steel has been used in 25kHz and 70kHz electronic transformers. The working frequency used by silicon steel has reached 325kHz.

High magnetic permeability permalloy is characterized by high magnetic permeability and good environmental adaptability, but it is expensive. The ultra-thin permalloy strip developed in recent years has a working frequency of more than 1MHz. It is used in places with special requirements and military equipment. used in . Cobalt-based amorphous alloy is the material with the lowest high-frequency loss in the existing soft magnetic materials, and it is expensive. However, when used at high frequencies above 200kHz, the core weight is small and the price factor is not prominent. At 200kHz and 1MHz It is widely used in high-frequency electronic transformers.

Soft magnetic composite materials have become a major development direction of magnetic core materials for high-frequency electronic transformers. Compared with traditional soft ferrite and soft magnetic alloys, their magnetic metal particles or films can be distributed in non-conductors and other materials. , so that the high frequency loss is significantly reduced and the operating frequency is increased. At the same time, its processing technology can be processed into powder cores by hot pressing, or it can be injection-molded into complex-shaped magnetic cores by using advanced plastic engineering technology. It has the advantages of low density, light weight, high production efficiency, low cost, and product repeatability. Good consistency and other characteristics. Different ratios can also be used to change the magnetic properties. The examples of composite materials composed of soft ferrite and permalloy have been introduced above, and soft magnetic composite powder cores with operating frequency above 10kHz 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. Some of the planar magnetic cores used to be modified with the original soft ferrite cores, and there are various low-height soft ferrite cores specially used for planar transformers. It is also possible to develop various low-height soft magnetic composite cores in the future. In addition to further compressing the planar magnetic core, the core of the chip transformer also has a chip core manufactured by co-firing. Thin-film magnetic cores and magnetic materials are one of the most active development directions of high-frequency electronic transformers, and will become the main core materials and structures of high-frequency electronic transformers above MHz. It is possible to make the height of thin-film electronic transformers below 1mm, which can be installed into various cards. Several centers have been established in China to study vigorously. It is hoped that material development, electronic transformer manufacturing and application units can be united, and the domestically developed thin-film soft magnetic materials can be turned into high-frequency electronic transformer cores in electronic information products as soon as possible, forming a domestic thin-film transformer with independent intellectual property rights. Efforts are being made to make this work.

Coil Material and Construction

With the development of the overall structure of high-frequency electronic transformers, the main development directions of the coil structure are planar coils, chip coils and film coils, including multi-layer structures. There are also some new developments in the selection of materials for various coil structures.

For the high-frequency transformer coil of the three-dimensional structure, the wire material adopts multi-strand wires (Ritz wires) due to consideration of skin effect and proximity effect, and sometimes flat copper wires and copper strips are also used. The insulation material is made of high heat-resistant material to increase the allowable temperature rise and reduce the volume of the coil, and the use of double-layer and triple-layer insulated wires can reduce the size of the coil. To give an example, recently, a C-class insulated magnet wire that uses nanotechnology to coat mica on copper wire has been developed in China. It has been applied 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. will be applied.

Coil with planar structure, the wire is made of copper foil, most of which are made of single-layer and multi-layer printed circuit boards, and some copper foil with a certain pattern is folded. Insulation materials generally adopt B-grade materials.

Thin-film structure coils, the wires are made of copper, silver and gold films, made into comb-shaped, spiral-shaped, sports field-shaped and other graphics, and the insulating materials are made of H-grade and C-grade materials. There are also multi-layer structures, or several multi-layer coils are combined, or several coils and several magnetic cores are overlapped. In short, thin-film transformers are high-frequency electronic transformers that are being vigorously developed, and many structures are not finalized. Perhaps, many new coil structures will appear

Direction of development

The biggest feature of high-frequency electronic transformers is high frequency. From the perspective of the working principle of the transformer, increasing the operating frequency can reduce the volume and weight of the transformer, that is, to achieve shortness and lightness, thereby increasing the transmission power per unit volume (or weight), that is, high power density. These are the inherent characteristics and direct results of high-frequency electronic transformers themselves, and high-frequency, short, thin, and high-power density cannot be simply regarded as the development direction of high-frequency electronic transformers. Wouldn't it be too easy to "have great guiding significance for the electronic transformer industry" if you mention a few "transformation" slogans? A series of problems should be brought to the electronic transformer by high frequency. By solving these problems, the performance can be improved and the cost can be reduced, that is, the pursuit of the best performance-price ratio is the starting point, and a more detailed development direction can be put forward. Only then can it have a certain impact on the industry. guiding significance.