A Fully Capacitive Transformer Device for Galvanic Isolation Applications

Galvanic isolation is commonly utilized in power transmission and data communication. Studies have explored inductive and electromagnetic coupling for isolation between nearby circuits, while optocoupler devices employ modulated light for data transmission. However, isolation devices have inherent limitations, such as restricted bandwidth, susceptibility to temperature variations, and long-term degradation. These challenges underscore the need for alternative methods to enable reliable and efficient bidirectional data exchange in isolated circuits. We developed a fully capacitive transformer device, based on mutual capacitance, which provides good linear properties across a wide range of frequencies, as well as stability with temperature variations. A model transformer was characterized using circuit analysis and experiments, confirming the physical properties of the device. Then, a functional device was built and applied to provide galvanic isolation between circuits with two different voltage levels. Finally, the device was explored in the configuration with maximum power transfer, using inductors to improve the coupling.