15.4 A 52% Peak-Efficiency >1W Isolated Power Transfer System Using Fully Integrated Magnetic-Core Transformer

Abstract

Galvanic isolation is becoming increasingly important in a wide field of applications to guarantee human safety or better reliability in harsh industrial environments. The transfer of both data and power across an isolation barrier is often an essential requisite in these applications. While data transmission with galvanic isolation has been achieved through traditional optocouplers, capacitive coupling, or integrated transformers, transferring power across the isolation barrier presents several challenges regarding the size and the performance. Some of the state-of-the-art devices adopt post-processed micro-transformers [1], which use $6 \mu \mathrm {m}$-thick plated Au for both the primary and secondary windings. The operating frequency of the integrated transformers is $\sim 180$ MHz to achieve optimal quality factor of $\sim 10$, thus the switching power loss reduces the efficiency below 35%. At such a high frequency, the radiated emissions are a big concern for end users, especially for automotive and medical applications. In this work, a fully integrated isolated power transfer system is demonstrated using an integrated transformer with magnetic core. It represents a major improvement due to higher quality factor and lower operation frequency as a result of magnetic core integration on silicon.