Monolithic Bidirectional GaN Switch-Based Buck-Boost Converter

Why It Matters

The CoBB architecture dramatically boosts power‑density and efficiency for battery‑powered systems such as eVTOLs, enabling lighter converters and longer flight ranges. Its simplified topology also lowers BOM cost and reliability risk, accelerating adoption of GaN‑based power electronics.

Key Takeaways

• Monolithic GaN BDS replaces four switches with one
• CoBB achieves >95% efficiency at 1 kW, 100 kHz
• Passive weight reduced threefold versus traditional buck‑boost
• Conduction losses cut roughly half versus MLFCC at N=6
• Single return‑path inductor lowers volume, raises common‑mode voltage

Pulse Analysis

Buck‑boost converters are the workhorses of battery‑ and fuel‑cell‑driven platforms, from electric aircraft to portable robotics. Conventional designs rely on large inductors or multilevel flying‑capacitor networks, which inflate size, weight, and component count. As manufacturers chase higher gravimetric power density, the industry has turned to gallium nitride (GaN) for its fast switching and low losses, yet integrating GaN devices into complex topologies often adds design overhead and thermal challenges.

The condensed buck‑boost (CoBB) converter tackles these issues by merging the buck and boost stages of a multilevel flying‑capacitor converter into a single monolithic bidirectional GaN switch. This BDS device eliminates the need for four discrete FETs, slashing conduction losses by about 50% and simplifying gate‑driver architecture. Because the voltage is shared across fewer active devices, lower‑rated switches can be used, further enhancing efficiency. Moreover, the CoBB’s passive component strategy—either dual input inductors or a single return‑path inductor—optimizes weight, delivering a three‑fold reduction in passive mass compared with traditional buck‑boost solutions, a critical advantage for aerospace applications where every gram counts.

Hardware validation confirmed the concept’s viability: a 1 kW prototype operating between 200 V and 500 V achieved over 95% efficiency in both buck and boost modes at 100 kHz, matching the performance of a conventional non‑inverting buck‑boost while offering a three‑times better passive‑weight ratio. These results signal a clear path for GaN‑centric power architectures to replace bulkier silicon‑based converters, promising lighter, more efficient power supplies for next‑generation electric vehicles, drones, and grid‑edge storage systems. Industry players adopting the CoBB topology can expect reduced bill‑of‑materials, improved reliability, and a competitive edge in markets demanding ultra‑dense power conversion.