An energy-adaptive MPPT power management unit for micro-power vibration energy harvesting

A batteryless power management unit (PMU) that manages harvested low-level vibration energy from a piezoelectric device for a wireless sensor node is presented. An energy-adaptive maximum power point tracking (EA-MPPT) scheme is proposed that allows the PMU to activate different operation modes according to the available power level. The harvested energy is processed by an ac-dc voltage doubler followed by on-chip charge pumps with variable up/down conversion ratios for higher efficiency. Interleaving technique is employed for the high-power output to reduce both current and voltage ripples. The PMU is designed using a 0.35mum CMOS process, and simulation results are presented to demonstrate its functions.