The design of the hottest transformer and the tech

2022-08-07
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Transformer design and dc/dc converter technology have developed synchronously

in recent years, in many fields of the electronic industry, companies engaged in the design and manufacture of dc/dc converters are under great commercial and competitive pressure. The market demand has shifted to products with small volume, high density and higher efficiency

in terms of cost, volume and performance, transformer is a key device in the design of dc/dc converter. Therefore, everyone is trying to optimize the device to match the development of advanced semiconductors and passive components

although the traditional wound type transformer is still used in many large waveform factor power supply applications, the emergence of several new technologies in recent years has brought significant benefits to the design of dc/dc converter, one of which is the flat panel transformer

free standing and embedded flat panel transformers. The independent flat panel transformer is composed of planar copper lead frame or copper wire of printed board as winding resistance. This means that they occupy much less space than traditional transformers with copper wire wound on the bracket. The precision copper lead frame or printed winding makes the design specification more accurate than that of wire wound transformer, and the repeatability level between pieces is also improved

the etched copper lead frame or printed winding resistance is stacked in the flat plate and walks along the opening direction, forming the magnetic circuit of the transformer with the high-frequency ferrite core. This design makes it a very low profile transformer assembly. The realization of large cross-sectional area copper conductor in flat panel design makes the design of high power density and high current easier. The high surface capacity ratio of flat plate winding and ferrite makes the product have good heat dissipation function

especially at high operating frequency, high efficiency is a further key benefit of planar transformer. In the wound transformer, the efficiency is inversely affected by the "skin effect", that is, when the high-frequency current passes through the cylindrical conductor, it forces the electrons from the middle to the edge to concentrate on the surface of the copper wire, thus reducing the cross-sectional area of the conductor through which the current passes

from the point of view of completion and assembly, the planar transformer is also better than the wound transformer. Wound transformer usually requires manual operation to strip the coating at the winding end, and then dip tin or manually solder. The lead out ends of pressed or etched copper sheets on planar transformers can often form surface mount terminals to increase assembly speed and repeatability, thereby reducing costs. This advantage is even more prominent when combined with the embedded planar transformer, where the ferrite passes through the dc/dc converter PCB, and the winding is spirally wound on the printed circuit board

although they occupy more space than embedded design, the popularity of independent planar transformers has been increasing in recent years. Because the fully embedded transformer uses the circuit board of the dc/dc converter as its own winding, each group of input/output voltage needs to design different circuit boards. Moreover, for embedded planar design, because multilayer circuit boards are required to etch the coil, the overall cost is high. Some hybrid designs use the main board as the primary winding, and then use the separated small PCB as the secondary to generate different output voltages. This design is also common

although the embedded design achieves high power density and has good thermal performance to achieve space saving, for many applications, these advantages are limited by cost, lack of flexibility and interchangeability. High production will offset the higher cost of embedded design to some extent

more transformer designs. The design of existing transformers is based on magnetic technology. In the future, the large-scale adoption of acoustic coupling technology will provide the potential for smaller transformer design. At present, some dc/dc converters with low power and high output voltage have been realized to some extent

The acoustic transformer uses the characteristics of piezoelectric materials to couple electric energy through a vibrating structure. One converter excites a resonant mode of the material, which is then intercepted by a second secondary converter and converted to a secondary voltage

in other developments in transformer design, the use of extremely high operating frequencies can produce effective air coupling, so ferrite is not required. The combination of transformer and other magnetic devices such as output choke into the circuit is another big start, which will help reduce the total waveform coefficient of dc/dc design

finally, the development of new magnetic materials allows for higher operating frequencies and low losses, which will help to provide smaller transformers for a specified power source that is no longer charged from the 4th policy year

it is obvious that wound transformer has become increasingly unsuitable for dc/dc converters and other applications. Their large size, low efficiency and the difficulty of not meeting the repeatability of each piece mean that they are rapidly being replaced by new technologies

embedded and independent planar transformers have their own advantages and disadvantages. One or the other depends on the application needs in the design. Tapped secondary (or primary) transformer is an innovation and provides some advantages over traditional design. Again, applications will determine whether they are the most appropriate choice for a given design. In the future, the development from magnetic transformer to acoustic transformer seems to produce some exciting new products, and the choice of dc/dc converter designers will be more and more

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