Loop Conductance Adapting Methodology to Suppress Switching Oscillations in High-Frequency GaN-Based Circuits

Abstract

Gallium nitride (GaN) devices have enormous potentials in electric vehicle (EV) applications. The trend of high frequency and high power density help increase EV mileage level greatly. However, due to the ultra-fast switching speed of the GaN devices and low damping level in the compact circuit, switching oscillations are prone to happen and sometimes even sustain, which affects the circuit stability heavily. In this research, loop conductance adapting methodology is proposed to solve this problem, which is inserting a loop conductance adapter (LCA) into the GaN-based circuit. The LCA can be in manifold forms and inserted into different positions. A modified negative conductance model is established, which is universal to all the forms and inserting positions. Based on the established model and a derived stability criterion, the optimized design method is proposed, with which the most appropriate LCA parameters could be calculated and the corresponding suppression effects could be predicted. The details of the design method are introduced with three typical LCA examples. All the theoretical achievements are verified with LTspice simulations and experiments. In addition, the three examples are compared with each other according to suppression effects and power losses. Suggestions about LCA inserting position selection are also proposed.