The transformer is a key component of the Power Supply. Conventional transformers are usually composed of a ferrite core and a copper coil, which are bulky and susceptible to electromagnetic interference. However, planar transformers can effectively solve volume and high frequency problems. Today, Xiaobian will take you to understand the classification of planar transformers and the characteristics of planar transformers.
Classification of planar transformers:
1. PCB type transformer, printed circuit PCB type transformer can eliminate the winding skeleton, can increase the heat dissipation area, can reduce the eddy current loss caused by the skin effect and the proximity effect at high frequency operation, and can also increase the current density. The current density is up to 20A/mm, the power is large, and the process is simple. However, with PCB, the window utilization rate is low, only 0.25~0.3, the window utilization rate of the traditional transformer is 0.4, and its volume is also large. The PCB type transformer can have a power of up to 20 kW and a frequency of the order of megahertz. Using the flat technology of pulse, the multi-layer PCB is sandwiched between the cores. The thin high-efficiency ferrite planar transformer has a small bottom area, a height of only 7.4mm, an operating frequency of 150~750kHz, and an operating temperature of -400~1300.
2, thin film type transformer, thin film type transformer is a laminated micro-transformer developed with magnetic film, the film height is less than 1mm, the working frequency is more than 1MHz, its small size, easy to integrate, but only for low power. Most of them use metallic magnetic materials such as permalloy, ferrosilicon and amorphous alloys. Mainly because they have high BS and high magnetic permeability. Tsuijimotl et al. used an insulating film (thickness 100 μm) with a strip type (copper thickness 35 μm, length 34 mm, width 3 mm), and an amorphous Co nbZr film (1.8 μm) constitutes a thin film transformer capable of output voltage control at high frequencies - - A pinhole type transformer is also fabricated with a chip transformer having a thickness of 210 μm. It is made of two 10μm thick CoZr amorphous films for 5V, 0.3A, 1MHz switching power supplies, and 77.5% ferrite materials (mainly MnZn) can also be made into thin film transformers, but It is difficult to produce a suitable micro-magnetic film by a conventional method, so a new film forming technique needs to be developed. At present, foreign countries mainly use PVD, CVD and other deposition techniques such as chemical etching, laser ablation, light irradiation and low temperature coating. The miniature transformer designed and manufactured by Yamaguchi K has an area of ​​only 2.4mm × 3.1mm and an efficiency of 67% at 10MHz.
3. Thick film transformers, thick film transformers are proposed to overcome the defects of large conductor resistance in thin film transformers. Using alumina as the substrate, the thick film process is used to print the primary and secondary windings on the upper and lower surfaces. The planar transformer made of ferrite is 2MHz, and the output power is 75W, the efficiency is 85%. Planar transformers manufactured by thick film processes are generally less efficient, so the search for further process technologies to improve the thick film process for planar transformer fabrication is the key to achieving high-frequency integration of planar transformers.
Features of the planar transformer:
1. High current density. The wires of a planar transformer are actually some planar conductors and thus have a high current density.
2, high efficiency. The efficiency can reach 98%~99%.
3, low leakage. It is about 0.2% of the primary inductance.
4, heat conduction is good. The hot aisle distance is short and the temperature rise is low.
5. Low EMI radiation. Good core shielding reduces radiation to a very low level.
6, small size. The use of a small magnetic core can reduce the volume accordingly.
7, the parameters are repeatable. Because the winding structure is fixed and pre-machined, the parameters are stable.
8, the working frequency range is wide. The frequency can range from 50 kHz to 2 MHz.
9. Wide operating temperature range. Operating temperature is -40 °C ~ 130 °C.
10. Good insulation. The planar transformer consists of a conductive circuit and an insulating sheet that overlap each other to ensure 4 kV insulation isolation between the windings, the primary-secondary and the secondary-secondary.
The above is a brief introduction to the classification of planar transformers and the characteristics of planar transformers. I believe that after reading the classification of planar transformers and the characteristics of planar transformers, we have learned more about the classification of planar transformers, and also know the characteristics of planar transformers to help you better choose transformers.
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