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High Frequency Transformer Mainly Used For Voltage Conversion

Jul 27, 2017

High Frequency Transformer Mainly used for voltage conversion

Are there any differences between high frequency transformers and inductors?

The same point: are wrapped with enameled wire package, the internal core or core.

Differences: Transformers are mainly used for voltage conversion, which is based on the law of electromagnetic induction. Inductive coils are generally used in electronic circuits, according to Lenz's law. The former generally have two or three windings, there are primary windings and secondary windings, for the step-up transformer, the primary winding turns less coarse diameter, the number of secondary winding turns and fine line, step-down transformer with it On the contrary, the primary turns of multi-line fine, secondary turns less diameter rough, widely used in a variety of electrical appliances as a power use. Inductive coils are used in electronic circuits for two purposes:

1, and capacitance resistance with the waveform generator circuit or frequency selection circuit,

2, in the current is relatively large and pulsating relatively large occasions into the circuit as a smoothing device. There are many other occasions, such as the lamp in the ballast, the main is based on the inductor coil current can not be mutated when the current rate of change is too fast to produce a very high reverse electromotive force made of the principle.

With the development of power electronics technology, and further increase the demand for multi-functional and high-density electronic equipment, as an indispensable switching power supply of electronic equipment, the urgent need to achieve small and lightweight. In order to make the switching power supply miniaturization, the first requirements of switching power supply transformer miniaturization. Higher operating frequencies PC44 and PC50 power ferrite materials and cores are developed to meet this need.

The performance of ferrite is not determined solely by its chemical composition and crystal structure, but also the density and grain size, porosity and their distribution between grains and grains. Therefore, the preparation of high-performance power ferrite material, the formula is the foundation, sintering is the key. The formulation and density determine the saturation magnetic flux density of the material Bs (the power ferrite core usually operates in a DC bias field where the high Bs is required to ensure that the core has high DC superposition characteristics) and Curie temperature (Fc), and the incorporation of effective additives and with the appropriate sintering process to match the performance of the ferrite has a decisive effect, affecting the degree of solid phase reaction and the final phase composition, density and grain size , So that the microstructure of soft ferrite to be more effective control, so as to ensure that the main parameters of the material parameters to achieve a harmonious unity.

1 main performance selection of high performance power ferrite

In order to improve the power conversion efficiency and avoid saturation, the power ferrite material required for use in high frequency switching power transformers has high Bs, high starting permeability (μi) and high amplitude permeability (μa), and in order to avoid Transformer in the high frequency of heat breakdown, the material power loss (Rc) should be as small as possible, want a negative temperature coefficient. It can be said that the three important magnetic properties of the power ferrite material are μi, Bs and Rc and the frequency, temperature and time stability of these parameters, which is a contradictory unity, some parameters And even serious opposition, the organic idea of their organic unity is to control the magnetocrystalline anisotropy constant K1 ~ t curve and the ferrite microstructure, in the formula, additives and sintering process K1 has a good temperature characteristics, The minimum value of K1 is adjusted to the appropriate position and tends to zero.