Transformer shielding layer design method for flyback switching power supply

Abstract

The invention discloses a transformer shielding layer design method for a flyback switching power supply. The transformer shielding layer design method comprises the steps of 1) measuring and estimating structures and electrical parameters of a transformer; 2) setting a shielding layer length as the circumference of the layer, setting the thickness according to actual supply, wherein the position of the layer is set based on a proper value; obtaining structural capacitance between a primary side winding and a secondary side winding of the transformer, and structural capacitance between the secondary side winding and a shielding copper foil layer under different shielding layer widths in a simulation manner through finite element software analysis; 3) calculating common-mode evaluation equivalent capacitance in the transformer under the different shielding layer widths, and drawing a common-mode equivalent capacitance-shielding layer width characteristic curve; and 4) obtaining the shielding layer width when the common-mode evaluation equivalent capacitance is equal to 0 according to the drawn characteristic curve, wherein the obtained shielding layer width is the optimal shielding layer width for restraining common-mode current of the transformer. Compared with the existing common-mode restraining technology, the transformer shielding layer design method has the advantages of simple realization, low cost, capability of reducing the volume and the weight of the common-mode filter, obvious restraining effect, and the like.

Description

technical field [0001] The invention belongs to the technical field of transformer design, and in particular relates to a design method for a transformer shielding layer of a flyback switching power supply. Background technique [0002] Flyback switching power supplies are widely used in communications, service systems and low-power electronic equipment due to their isolation function. These devices all need to meet relevant electromagnetic compatibility (EMC) standards, so there are often certain electromagnetic interference (EMI) filtering measures in the design of switching power supply products. With the switching characteristics of switching devices getting better and better, high dv / dt and di / dt bring serious EMI problems. On the one hand, these serious EMI problems will make it difficult for power supply products to meet the relevant EMC standards. On the other hand, even if the relevant EMC standards are met, common-mode noise will sometimes form on the sensitive lo...

AI Technical Summary

Problems solved by technology

With the switching characteristics of switching devices getting better and better, high dv / dt and di / dt bring serious EMI problems

On the one hand, these serious EMI problems will make it difficult for power supply products to meet the relevant EMC standards. On the other hand, even if the relevant EMC standards are met, common-mode noise will sometimes form on the sensitive load side, causing serious interference to electronic loads.

In theory, fixing the width, thickness and position of the shielding layer and adjusting the length appropriately; or fixing the length, thickness and position of the shielding layer and adjusting the width properly can minimize the common-mode current in the transformer, thereby reducing the common-mode current on the load side. How to suppress the mode noise to the lowest level, but how to quantitatively design these indicators is a long-term problem in the industry that is difficult to achieve well

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