The high-frequency transformer replaces the heavy frequency transformer in the traditional inverter, which greatly reduces the volume and weight of the inverter. In the design of high frequency chain hardware circuit, high frequency transformer is an important link. High-frequency transformers are operating frequency of more than if (10kHz) of the power transformer, mainly used in high-frequency switching power supply for high-frequency switching power transformers, but also for high-frequency inverter power supply and high-frequency inverter welder for high-frequency inverter power transformers.
High-frequency transformers are not standard parts, variety specifications are mixed, no naming standards. The so-called model, is only the manufacturer to mark a symbol used to distinguish the classification. Custom processing is usually required.
The design of High-frequency Transformers should first start with the core. Switching power transformer cores are mostly soft magnetic materials used in low magnetic fields, which have higher permeability, lower coercivity, and high resistivity. High permeability, in a certain number of coil turns, through a small excitation current can withstand a higher external voltage, therefore, the output of a certain power requirements, can reduce the core volume. The magnetic core coercivity is low, the hysteresis area is small, and the iron consumption is less. High resistivity, the eddy current small, iron consumption is small. Ferrite material is a composite oxide sintered body, high resistivity, suitable for high-frequency use, but the BS value is relatively small, often used in switching power supply.
The design of high-frequency transformers is generally used in two ways: the first is to find out the core window area AW and magnetic core effective cross-sectional area Ae's product AP (Ap=awxae, called the core area product), according to the AP value, look-up table to identify the required number of magnetic materials;
The second is to find out the geometrical parameters, check the table to identify the core number, and then design.
In the high-frequency transformer design process should pay attention to:
1 in the transient process, high-frequency chain leakage and distribution capacitance will cause inrush current and spike voltage and pulse top oscillation, so that the loss increases, the serious damage caused by the switch tube. At the same time, the output winding turns more, the number of layers, should consider the influence of distributed capacitance, reduce the distribution of capacitance is conducive to suppress high-frequency signal on the load interference. The same transformer at the same time reduce the distribution of capacitance and leakage is difficult, should be based on different work requirements, to ensure the appropriate capacitance and inductance.
2 in the design, when the maximum output power, the magnetic induction in the core should not reach saturation, to avoid distortion in the large signal.
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