A high-efficiency power management unit with wide dynamic range for RF energy harvesting system

A high-efficiency power management unit (PMU) with wide dynamic range for radio frequency (RF) energy harvesting system is proposed in this paper. A digital zero current switching (ZCS) and a digital maximum power point tracking (MPPT) circuits are adopted. A sub-threshold current reference circuit and a subthreshold voltage detection circuit are proposed to reduce the power consumption of always-on control circuits and improve the conversion efficiency at low input power. A dual-oscillator is designed to extend the frequency range and widen the input power range with optimized power consumption under low-end band and high-end band, respectively. Switch size and on-time are adjusted according to the input power, which optimizes the conversion efficiency in a wide power range. Proposed PMU is implemented in a standard 180 nm CMOS process. The post-layout simulation results show that proposed PMU can achieve cold-start at the input voltage of 280 mV, the power consumption to maintain the PMU is only 9.6 nW. The input power range of the PMU is 11 nW-677 mu W. When the input power is 50 nW, a power conversion efficiency (PCE) of 65% is achieved, and the peak PCE can reach 93% at 23.5 mu W.