Author(s)

Lai Yaokang, Li Guolin, Wu Weigang

Corresponding Author

Yaokang Lai

ABSTRACT

The present article puts forward a mathematical model for spiral windings transformer based on the PCB technique and the coils is equivalent to the concentric rings. Formulas for calculating the mutual inductance between two parallel rings are derived from Neumann formula and three simplified formulas are obtained for three special circumstances, i.e. two coils are coaxial but in different planes, in the same plain and concentric, and complete coincidence. Then the self and mutual inductances of the spiral windings are calculated. Base on theoretical calculation, the spiralwinding specifications are analyzed including turns of windings, the distance between turns and between layers, the number of layers, the relationship of those between inductances, coupling coefficient. The key points relating spiral transformer design are summarized. Finally, the PCB spiral transformer electrical model is established based on the ideal transformer and practical samples are produced to verify the accuracy of the formulas and the electrical model. The theoretical formulas and the electrical model derived are suitable for circuit designs in practice.

KEYWORDS

PCB, spiral windings, transformer, couple