Capacitive-Coupled Stacked Class-D Oscillators for Galvanic Isolators

Abstract

This brief presents a novel class-D oscillator topology conceived for galvanically isolated data transfer based on RF planar coupling. In its general implementation, it consists of n capacitively coupled stacked class-D oscillators, each one loaded by a primary transformer winding. Capacitive coupling between the oscillators guarantees robust frequency/phase synchronization. The oscillation voltages are combined at the secondary transformer winding, thus ideally producing the same oscillation amplitude of a class-D topology with a power consumption reduced by a factor of 1/n thanks to the current-reuse configuration. With respect to traditional topologies, capacitive-coupled stacked class-D oscillators also allow standard MOS transistors (i.e., with a low breakdown voltage) to be reliably operated at higher supply voltages. The oscillator advantages have been highlighted in comparison with the traditionally adopted complementary cross-coupled topology within an isolated data link based on RF planar coupling in a 0.18-µm CMOS technology.

A GaN-Integrated Galvanically Isolated Data Link Based on RF Planar Coupling With Voltage Combining for Gate-Driver Applications

“…2). Recently, the current-reuse approach has been adopted to a novel topology based on class-D coupled oscillators [35], [36], especially devised for package-scale isolation. The TX front-end of the proposed isolation channel exploits such a solution according to the schematic shown in Fig.…”

“…In the first design (i.e., layout A) two identical TX micro-antennas were placed at a distance, d TX . Since a less than linear decay of k P is observed at the increasing of d TX [36], whereas k is almost constant, a d TX of 20 μm has been used to minimize the silicon area for a given level of induced RX voltage, V RX , according to (2). In the second solution (i.e., layout B), a superposition of around 30% has been obtained by a shifting of 50 µm and 160 µm along the x (namely the channel direction) and y axis, respectively.…”