The power management circuits (PMCs) of triboelectric nanogenerators (TENGs) play a key role in developing self-powered sensing system with high energy storage efficiency. However, when the operating voltage (Vop) of PMCs meets the voltage requirement of electronic equipment (generally around 5 V), PMCs have a reduced efficiency less than 36%. Here, based on analyzing the factors affecting the efficiency of PMCs, the general methods have been proposed to improve the efficiency at a lower Vop. It is found that energy loss of diodes in PMCs is the main part in total energy loss, reaching a ratio of 61.7% at a 5 V Vop. By using rectifier diodes with lower threshold voltage and developing double loops power management circuit (DL-PMC) with less operating diodes number, the energy loss of diodes is reduced from 38.6 to 17.0 μJ, and its ratio in total energy loss at a 5 V Vop is reduced to 47.1%. Moreover, it is found that in PMCs with varied open-circuit voltage (Voc) of TENG, the increasing trend of diodes energy loss (∝Voc) is slower than that of TENG’s output energy (∝Voc2), resulting in a reduced energy loss ratio from 62.7% to 26.1% as Voc increasing from 200 to 1000 V. Finally, the measured optimal energy storage efficiency of 48.9% at 5 V Vop, the record reported so far, has been reached as using a DL-PMC with rectifier diodes and Pulsed-TENG with a Voc of 1000 V. A self-powered flue gas monitoring system consisting of Pulsed-TENG, DL-PMC, and gas sensor is developed for detecting operating status of boiler, which can transmit data every 2.5 min and will have broad applications in industry. The proposed general methods are suitable for other PMCs and will promote the development of self-powered sensing systems.