A 50 nW to 10 mW Output Power Tri Mode Digital Buck Converter With Self Tracking Zero Current Detection for Photovoltaic Energy Harvesting
This paper presents a tri mode digital buck converter in 0.18 mm 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.
IEEE Journal of Solid State Circuits