Toward chip-scale Off-line Power supplies in GaN: Advancing monolithic GaN analog and mixed signal circuit design for high-efficiency and highly integrated power-factor correction (PFC) converters

• Applicant: Professor Dr.-Ing. Bernhard Wicht
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 546122684

Grid-powered applications like desktop computers, TVs, industrial power supplies, and telecommunications infrastructure (5G/6G) are experiencing an increasing demand for higher power efficiency and density. Despite the moderate power levels (~100 W), their growing number and long runtimes sum up to annual consumptions of many TWh. Therefore, having high energy efficiency is crucial to reducing global energy usage, which is a strong motivation behind the proposed research. With the trend towards flatter screens and smaller desktop computers, the power interfaces must also become more compact. Both goals favor monolithic GaN technology due to the low-loss, high-frequency switching capability, and compact system size. The proposed research targets the monolithic GaN integration of a high-voltage, fast-switching power conversion topology combined with closed-loop analog/mixed-signal control to replace conventional, space-consuming power supplies within the highly relevant 75-200 W range. International and regional standards demand power factor correction (PFC) in this power range. A well-established PFC topology using GaN is the totem-pole PFC (TPPFC) converter, typically targeting the kW power range due to a bulky system overhead in a discrete implementation. A key aspect of the proposed research entails harnessing the unique advantages of the monolithic GaN integration using imec’s 650V GaN-on-SOI technology, available through regular MPW runs. The power stage design for this project draws on previous GaN-IC experience by the applicant. The integration of analog, mixed-signal, and power circuits on a single die reduces parasitics and pin count significantly, enabling power conversion at switching frequencies beyond 1MHz. The research aims to determine the level of complexity that can be achieved by integrating the GaN-IC from a circuit design perspective, considering the current state of technological possibilities. The use of monolithic GaN technology in non-power circuits (analog/mixed-signal) is an ongoing research topic with vast potential for control-loop circuit blocks such as high-gain amplifier stages and voltage references. However, GaN technology still shows significant drawbacks in various aspects, including parameter variations and analog performance, and lacks a suitable p-type device. Limited knowledge exists on the design of non-power circuits in GaN. Therefore, this project focuses on analog and mixed-signal circuits in GaN. A particular focus is developing innovative approaches to replace missing p-type devices as an active load in analog circuits. Preliminary studies conducted by the applicant’s group suggest that a switched-capacitor-based floating n-type device could be a viable replacement for the p-type device. The targeted research will be demonstrated in a monolithic TPPFC GaN-IC containing a high-voltage power stage and necessary sensing and closed-loop control circuitry, supporting >400 V at >1MHz switching.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2312: Energy Efficient Power Electronics "GaNius"