In the operation of high-frequency circuits, the manganese zinc material used in common-mode inductors faces the challenge of eddy current loss. This problem is closely related to the filtering efficiency of common-mode inductors and has a significant impact on their performance in many aspects.
In high-frequency circuits, alternating magnetic fields will induce closed current loops, that is, eddy currents, inside manganese zinc material. Although manganese zinc material does not have good conductivity like metal, it still has a certain conductivity. When eddy currents flow inside the material, heat will be generated due to the material's own resistance, causing energy to be consumed in the form of heat energy. This energy loss will directly weaken the energy storage capacity of the common-mode inductor, reducing the available energy when the inductor suppresses common-mode noise, thereby reducing the filtering efficiency.
As the circuit frequency increases, the skin effect becomes more obvious. Under high-frequency conditions, the current is no longer evenly distributed over the entire cross-section of the manganese zinc material, but is mainly concentrated on the surface of the material. This is equivalent to reducing the effective area through which the current passes, increasing the equivalent resistance of the material, and further exacerbating the eddy current loss. The increase of equivalent resistance not only increases energy loss, but also changes the impedance characteristics of common-mode inductors, making it impossible for the inductors to suppress high-frequency common-mode noise as expected, affecting the overall filtering performance.
Eddy current loss will also cause changes in the magnetic properties of manganese zinc material. The high-frequency alternating magnetic field and the additional magnetic field generated by eddy currents are superimposed on each other, resulting in uneven magnetic field distribution inside the magnetic core. This uneven magnetic field distribution will reduce the effective magnetic permeability of manganese zinc material, and the effective magnetic permeability is directly related to the inductance of the common-mode inductor. When the effective magnetic permeability decreases, the actual inductance of the common-mode inductor will deviate from the design value, and it will not be able to provide stable and sufficient impedance for common-mode noise of different frequencies, resulting in insufficient noise suppression capability in the filtering frequency band, reducing the filtering efficiency.
Another problem caused by eddy current loss is the temperature rise of the magnetic core. A large amount of energy is released in the form of heat energy, which will increase the temperature of manganese zinc material. The magnetic properties of manganese zinc material are sensitive to temperature. When the temperature rises to a certain level, its saturation flux density and magnetic permeability will decrease. The deterioration of magnetic properties caused by temperature rise will in turn aggravate eddy current loss, forming a vicious cycle. In this case, the performance of common-mode inductors continues to decline, and the filtering efficiency also decreases, and may even fail to meet the basic requirements of high-frequency circuits for common-mode noise suppression.
In order to evaluate the eddy current loss of manganese zinc material in high-frequency circuits, engineers usually focus on indicators such as loss tangent and quality factor. The loss tangent reflects the proportional relationship between the energy loss and energy storage of the magnetic core, while the quality factor reflects the comprehensive performance of inductor energy storage and energy consumption. When the eddy current loss increases, the loss tangent value will increase and the quality factor will decrease, which means that the loss of common-mode inductors increases and the energy storage capacity becomes worse, which directly affects its suppression effect and filtering efficiency on common-mode noise.
Faced with the impact of eddy current loss on the filtering efficiency of common-mode inductors, engineers have also adopted a variety of coping strategies. In terms of materials, the formula of manganese zinc material is optimized to increase its resistivity and reduce the generation of eddy currents; in terms of structural design, thin strip winding and segmented magnetic core are used to change the core structure, reduce the resistance of the eddy current path, and reduce losses. In addition, in circuit design, other components such as capacitors can be combined to work with common-mode inductors to compensate for the problem of reduced high-frequency filtering ability caused by eddy current losses.
The eddy current loss problem of manganese zinc material in high-frequency circuits has a negative impact on the filtering efficiency of common-mode inductors from multiple angles such as energy loss, magnetic property changes, and temperature rise. Only by deeply understanding the mechanism of eddy current loss and through various means such as material improvement, structural optimization, and circuit collaborative design, can eddy current loss be effectively reduced, the filtering efficiency of common-mode inductors in high-frequency circuits be improved, and the strict requirements of modern electronic equipment for electromagnetic compatibility performance can be met.
