The integrated and thin transformer design is a new development of power electronic transformers in recent years, but since this design is very related to materials and circuits, how to optimize the combination of the two must have materials , components and circuit design knowledge. For more integrated, thinner, and lower-cost transformers, a feasible direction is to achieve the functions required by traditional SPS in an integrated structure.
This type of design must take into account the distribution of the magnetic flux and the response of the circuit, but due to the complexity of such a magnetic circuit, the concept of the magnetic flux distribution of the traditional transformer is not easy to apply in this model, and the equivalent circuit model of the ideal transformer must be corrected. Considering the proportion of the inductor, the magnetic flux and voltage in the actual equivalent circuit are equal to the addition of the transformer and the inductor. It is more important that this structure makes good use of the magnetic flux capacity of the entire iron core, compared with the traditional discrete type. Components can have greater application flexibility. This concept of “coupled inductance” has the following key points: Combining the energy storage inductance of the power conversion circuit into a single iron core effectively saves the volume and weight of the magnetic component through the winding. The design of the line can control the magnitude of the ripple current, especially the last point above.
Under certain conditions, the output current ripple-free result can be obtained, which means that the output capacitor can be reduced or even unnecessary. In the same way, the energy storage inductor and the filter inductor can also be combined together to share one iron core.
From these circuit/magnetic circuit structures, the design of coupled inductors can produce many different effects, and the design principles can be described as follows:
1. Careful control of leakage inductance
2. The selected iron core must be able to bear all the AC and DC magnetic flux
3. The total number of windings should be less than three groups. If more than three groups, it is difficult to control the distribution of leakage inductance.
It should be noted that in some cases, the coupling may lead to other circuit problems, such as output polarity reversal. For the same reason, it is also feasible to couple the transformer and the inductor, and the BOOST circuit is designed by integrating the inductor component. Here, the design of this type of magnetic element is difficult to reduce the cost if it is produced by the traditional ferrite-winding method due to its complicated winding, but it is quite advantageous for the lamination or build-up process, because In this type of process, the number of windings has little effect on the cost, so it may be considered for application in the current power module design.
Inductive components are a very important part in switching power supplies, but they are very difficult to grasp. The improvement of product functions is closely related to the cooperation of the characteristics of iron core materials, the structure of inductive components and the design of switching circuits. In the past, the industry did not need to consider too many issues between materials-components-circuits in the way of vertical division of labor, but the current demand for high density and high performance has led the design of products to be highly integrated. Therefore, how to use materials-components? – Design considerations from the perspective of circuit integration. It is believed to be the design focus of high-performance switching power supplies. There are quite a few products abroad that use integrated design considerations, but the proportion in China seems to be insufficient. Obviously, this field is still worthwhile. space to invest.
