High power density transformer need to "go light" and embrace development.

2026-05-14

A transformer is a device that uses the principle of electromagnetic induction to change the alternating voltage. It works by applying an alternating voltage to the primary winding of the coil, generating an alternating magnetic flux, and then inducing an output voltage in the secondary winding. This enables the transmission of energy, voltage transformation, or electrical insulation isolation. When used in power circuits and power equipment, a transformer becomes a power transformer. A high-frequency power transformer refers to one with a working frequency higher than 20kHz. Why is 20kHz chosen as the boundary? Because 20kHz is the upper limit of the audible frequency range, and anything above it cannot be heard as noise.

Current power products generally aim for the characteristics of "light, thin, short, and small" and develop towards miniaturization and portability. Power transformers must adapt to the volume and weight requirements of the power products used by users. At the same time, the most prominent feature of high-frequency power transformers is their high-frequency nature. From the working principle of the transformer, increasing the working frequency can reduce the volume and weight of the transformer, achieving shortness, thinness, and lightness, thereby increasing the power transmission per unit volume or weight, and achieving high power density. Moreover, the raw materials for power transformers, such as the core material and conductive material, have seen an increase in price. Therefore, power transformers need to reduce their volume and weight to be lightweight and ready for deployment, in order to reduce costs, improve weight transmission power, and achieve better development.
Technology empowerment, multi-dimensional breakthrough to achieve "slimming and improving quality". The lightweighting of high-frequency power transformers is not simply reducing the volume, but a collaborative innovation in three dimensions: materials, structure, and process. While reducing weight and size, it also achieves a comprehensive improvement in efficiency, stability, and power density.
In the material innovation aspect, new high-frequency soft magnetic materials replace traditional silicon steel sheets as the core direction. Ferroresonant materials, amorphous alloys, and nanocrystals, with their characteristics of low loss at high frequencies and high magnetic permeability, can operate stably in the 20kHz - 1MHz high-frequency conditions. The volume of the magnetic core is reduced by 30% - 50% compared to silicon steel sheets, and the loss is reduced by 60% - 80%. At the same time, the application of lightweight copper foil and ultra-thin insulation materials further reduces the volume and weight of the windings, laying the foundation for the "slimming" of the transformer.

To streamline the development process, the following three points can be adopted as references:
1. Optimization of the overall structure
To adapt to the increasingly thinner and smaller power supply equipment, high-frequency power transformers can evolve from three-dimensional structures to planar structures, chip structures, and film structures, thereby creating a series of new high-frequency power transformers. For example: planar transformers, chip transformers, and film transformers. In terms of design, it is necessary to study the electromagnetic field distribution of various new structures, how to achieve the best optimization design, and also study various issues related to multi-layer structures; in terms of production processes, it is necessary to research various new processing methods to ensure the consistency of performance and realize the mechanization and automation of the processing technology, etc.; it can also explore the structure, design methods, manufacturing processes, and application characteristics of hollow transformers. Using computers to optimize and specifically design the overall structure scheme can shorten the design time, reduce material usage, shorten the production cycle, and lower costs.

2. Reducing the cost of magnetic core materials
The magnetic core is the most critical component in high-frequency power transformers that operate based 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 lower costs. Soft ferrite is currently the main core material used in high-frequency power transformers. The development direction is to develop new varieties with better performance and new processes to reduce costs. Compared with traditional soft ferrite and soft magnetic alloys, the magnetic metal particles or films in it can be distributed in non-conductive materials and other materials, significantly reducing high-frequency losses and increasing the operating frequency. The processing technology can be either processed into powder cores by hot pressing or molded into complex-shaped magnetic cores using current plastic engineering techniques, featuring low density, light weight, high production efficiency, low cost, good product repeatability and consistency. Different ratios can also be used to change the magnetism. Examples of composite materials composed of soft ferrite and palladium alloys have been introduced above. Now, soft magnetic composite material powder cores with a working frequency above 10 kHz have been developed. They can replace soft ferrite in high-frequency filter inductors.
According to the development requirements of the overall structure of high-frequency power transformers, the development direction of core structure is planar cores, chip-type cores and thin-film cores. Planar cores were previously modified from the original soft ferrite core. Now, various low-height soft ferrite core materials specifically for planar transformers are available. In the future, various low-height soft magnetic composite material cores may also be developed. The magnetic core of the chip-type transformer is further compressed from the planar core, and also includes chip-type magnetic cores manufactured by the co-firing method.

3. Development of Coil Structure
The main development direction of the coil structure is planar coils, chip-type coils and thin-film coils.
For the high-frequency transformer coils with a three-dimensional structure, the conductor material considers the skin effect and proximity effect by using multi-strand twisted wires. Sometimes, flat copper wires and copper strips are also used. The insulating material uses materials with high heat resistance to increase the allowable temperature rise and reduce the coil volume. Double-layer and triple-layer insulated wires are used to reduce the coil size. Domestic development has produced C-class insulating electromagnetic wires coated with mica on copper wires using nanotechnology, which has been applied in industrial frequency motors and transformers and achieved good results. It is estimated that it will also be applied in high-frequency power transformers.

Planar structure coils use copper foil conductors, most are manufactured using single-layer and multi-layer printed circuit boards, and also include copper foil with certain patterns folded together. The insulating material generally uses B-class materials.
Thin-film structure coils use copper, silver and gold films to form shapes such as comb-shaped, spiral-shaped and stadium-shaped. The insulating material uses H-class and C-class materials. They can be multi-layer structures or combinations of several multi-layer coils, or formed by the intersection and overlap of several coils and several magnetic cores.

Market pressure is forcing a rapid shift towards lightweighting. In scenarios such as fast charging power supplies, on-board chargers, photovoltaic energy storage inverters, 5G base station power supplies, and rail transportation, the requirements for space utilization, energy efficiency ratio, and portability of terminal devices have reached unprecedented heights. Traditional high-frequency transformers are constrained by silicon steel sheet cores and heavy winding structures, and generally suffer from large size, heavy weight, and high losses. This not only occupies valuable space but also intensifies energy consumption and heat dissipation pressure, making them unable to meet the upgrading needs of the downstream industry.

The lightweight transformation of high-frequency power transformers is not only a technological breakthrough but also releases significant economic and social value, enabling high-quality development in multiple fields.

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