A GaN-based Single-Stage Solid-State Transformer Replacement for 40 VA Class 2 Line-Frequency Transformers

Class 2 transformers are common among several low-power applications, including HVAC control systems, doorbells, automatic doors, and much more. These transformers have low peak efficiencies and very high standby losses. We propose a power-electronic alternative with an emphasis on reducing the yearly average power loss based on a use-case load cycle. Using GaN power devices, a single-stage solid-state transformer is designed, focused on reduced overall solution control and complexity, while maximizing standby efficiency through reduced switching and core losses. An optimization model was developed, providing both passive component recommendations and an optimum operating condition for the selected topology. The 40 VA, 120 VAC to 24 VAC, prototype achieves a peak efficiency of 98.8%, a standby loss of 106 mW, and a use-case average yearly power loss of 207 mW; a 17x reduction in the yearly average power loss compared to Class 2 line-frequency transformers.