A 50 nW-to-10 mW Output Power Tri-Mode Digital Buck Converter With Self-Tracking Zero Current Detection for Photovoltaic Energy Harvesting

• Published in: IEEE journal of solid-state circuits Vol. 51; no. 2; pp. 523 - 532
• Main Authors: Po-Hung Chen, Chung-Shiang Wu, Kai-Chun Lin
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.02.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Asynchronous mode (AM); buck converter; Delays; digital pulsewidth modulation (DPWM); digital zero current detection; Frequency modulation; Inductors; Power generation; Power transistors; Pulse width modulation; pulse-frequency modulation (PFM); System-on-chip; tri-mode; digital pulsewidth modulation (DPWM); digital zero current detection; buck converter; pulse-frequency modulation (PFM); Asynchronous mode (AM); tri-mode
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2015.2506685

This paper presents a tri-mode digital buck converter in 0.18-μm CMOS technology for photovoltaic energy harvesting. The on-chip gate-boosted digital pulsewidth modulation (DPWM) improves the conversion efficiency at heavy load conditions. Pulse- frequency modulation (PFM) along with digital self-tracking zero current detection is proposed to avoid reverse current at light load. The asynchronous mode (AM) operation further reduces the controller loss and improves the conversion efficiency at ultra-light load conditions. By applying DPWM, PFM, and AM at different load conditions, the proposed converter provides a maximum conversion efficiency of 92% with output power ranging from 50 nW to 10 mW. In addition, the proposed buck converter achieves more than 70% efficiency from 400 nW to 10 mW output power.