An Ultra-low-power Power Management Circuit with Output Bootstrapping and Reverse Leakage Reduction Function for RF Energy Harvesting

The reverse leakage current in the rectifier is a key challenge in RF energy harvesting systems, especially in harvesting modulated RF signals. In this paper, we propose a dual-band energy harvesting system operating at GSM-900 and WLAN 2.4 GHz bands. To harvest the RF energy from the WLAN band more efficiently, an event-triggered 1:2 parallel-series switched-capacitor (SC) converter is proposed to reduce the reverse leakage current. Meanwhile, this SC converter can provide an output voltage bootstrapping function while consuming 28 nW by asynchronous control. The power management unit (PMU) with the rectifier is fully integrated in a CMOS 130-nm process. Measurement results have shown the PMU can boost up the output voltage by 1.73x with an input voltage as low as 0.2 V. When harvesting the modulated waveform, the output ripple is decreased by 6x, and reverse leakage current reduction is over 2500x compared to the direct connection condition.