AC/DC boost converter with fast self-start-up for electromagnetic energy harvesting in wireless sensors

Electromagnetic energy harvesting-powered wireless sensors (EEHWS) are required to exhibit ultra-low power consumption, maintain operability under low-vibration conditions, and achieve autonomous fast start-up capability after long periods without ambient energy supply. However, most current EEHWS do not meet these requirements, remain inefficient under weak excitations, rely on dedicated start-up and complex gate driver circuits, even requiring up to 5 V supply voltage. Most of them do not take into account or report the time to restart after unpowered phases. To address these challenges, this paper proposes a novel AC/DC boost converter that eliminates the need for a dedicated start-up circuit by integrating a passive multi-stage voltage multiplier (VM) in the rectification stage to quickly reach the voltage level required for start-up. The number of required VM stages has been analytically and experimentally investigated in dependence on the characteristics of the electromagnetic converter and the energy profile of the output. The converter requires only a simple ancillary circuit and ensures faster start-up within 20 s instead of 43.67 s after low-energy phases because, during start-up, the VM charges the supercapacitor (SC) while supplying power to the ancillary circuit. Once the SC reaches the necessary voltage level, the system transitions to the boost phase, supplying power to the ancillary circuit and raising the output voltage for continuous operation. The novel converter has an output power of 1.2 mW with an efficiency of 72% and realizes a footprint reduction of 12.2%. It can supply a common microcontroller-based wireless sensor node for approximately 17 s.