The high-frequency transformer is the most important part of the switching power supply. The switching power supply generally adopts a half-bridge power conversion circuit. During operation, two switching transistors are turned on in turn to generate a 100kHz high-frequency pulse wave, and then the high-frequency transformer is used to step down and output low-voltage AC power. The ratio of turns determines the output voltage. The three most conspicuous high-frequency transformers in a typical half-bridge transformer circuit: the main transformer, the drive transformer and the auxiliary transformer (standby transformer). Each transformer has its own measurement specifications in the national regulations, such as the main transformer, as long as it is For power supplies above 200W, the core diameter (height) must not be less than 35mm. For auxiliary transformers, when the power supply does not exceed 300W, the core diameter will reach 16mm.
1. The most important function of the transformer is to transfer energy, and of course it also has the functions of isolation and transformation ratio.
Take the transfer of energy, for example, a mouse and an elephant carry things. Although the elephants transport more, they are slow, and the mouse transports less, but the speed is fast, so there are as many things. , As long as the speed is fast enough and the volume is small, it can also be completed. This is why the high frequency of the transformer can reduce the volume of the transformer. (This example was given to us by our power supply teacher when he talked about transformers).
2. Because of the high frequency, the switching frequency is high, so that the output ripple of the switching power supply can be made small. Here is also an example: Use a polygon to approximate a circle. The more sides it has, the more it can approach a circle. Therefore, the higher the switching frequency, the smoother the output waveform.
3. The volume of the high-frequency transformer is small; because of the high frequency, it can be used in a circuit with a higher switching frequency to reduce the output voltage ripple. Of course, firstly, with the increase of the switching frequency of power electronic devices, the high frequency of the transformer is likely to occur, otherwise there is no way to talk about it.
High frequency transformer optimizationSMPS power off, because of its small size and high efficiency, it is widely used in the electronic field. In addition, researchers continue to conduct research on its power density, and improve its T. operating efficiency by continuously increasing its changing frequency. In the high frequency state of the transformer, the volume of the transformer should be less than the range of 201Hz to 150kHz in theory 1, but this requires the same work to do the flux density and the high frequency state F magnetic material core loss can be compared with the low frequency, but- ∪ If the θ frequency exceeds 2001Hz, the working magnetic flux density will be reduced under the current material conditions, that is, if the core loss is guaranteed to be within the tolerable range, the frequency needs to be a few thousandths of a tex or a few hundredths of a tex. Therefore, power loss is the main factor limiting the effect of the high-frequency transformer optimization scheme. In other words,! For the specific condition F of the transmission power, the winding parameters and the magnetic core parameters should be reduced as much as possible, so as to ensure that the temperature rise range of the transformer during operation meets the requirements of the design standard. The paper analyzes the structure and design plan of the switching power supply to the musical instrument, and proposes an effective optimization design plan.
The above two formulas are used to calculate the positive impedance of the copper wire winding to determine the accurate impedance value in the actual T. operating frequency. However, this calculation method can only be completed by a computer because the calculation process is very complicated.
Through the analysis described above, the optimized design of high-frequency transformers is not a one-time T. work, and it is impossible to complete it all at once in actual operation. This is due to the interaction between various parameters in the operation of the variable instrument and the structure. Therefore, it is necessary to use T. as the magnetic flux density, winding wire diameter, number of windings, and number of parallel windings in the computer software for many attempts, so as to find the value that can meet the best design state, and complete Design Optimization. Among all the conditions, the most advantageous is that the types and parameters of the magnetic core are specific. For example, most of the magnetic core physical scale pairs are specific, and the characteristics of the lazy core material are also limited. But from another perspective, these conditions will also limit the optimization of the variable instrument and reduce the design space for optimization.
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