An Improved Inductance and Stray Capacitance Analytical Calculation Method For Multilayer Planar Spiral Inductors

Planar indcutors has been widely used in DC/DC convertor to achieve compact structure and improve power density. In order to achieve high inductance and high-frequency working, a multi-layer planar spiral inductor based on Low Temperature Co-fired Ceramics (LTCC) technology was desigined in this paper. Meanwhile, an improved analytical calculation method was  proposed to  estimate the inductance and stray capacitance. The mutual inductance of different turns is abtained by simply solving traditional Neumann’s formula, and self inductance of each turn is solved by Samimi’s method. Moreover, the equivalent capacitance is estimated according to the capacitance distribution model building in this paper. Experiment tests by impedance analyzer and 3D fenite element analysis (FEA) were conduct on different layer planar indutors. The calculated inductance matrix verify that,  both the analytical and FEA results are close with experiment test, and the proposed indctance calculating method show similar accuracy with FEA method but signicficantly reduced the calculating time. The relative error of stary capacitance estimating is near 5% in 3-layer inductor, wherease, the calculation error increase with winding layer increasing because the energy stored in the non-adjacent layers are ignored in the capacitance distribution model.

Posted by: Xin Liu, engineer, Institute of Electronic Engineering, China Academy of Engineering Physics, China (20-Jan-2020)
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