A Highly Reliable SIMO Converter Using Hybrid Starter and Overcharging Protector for Energy Harvesting Systems

This paper proposes a highly reliable single-inductor multi-output (SIMO) converter for energy harvesting systems, which is controlled by the power management controller (PMC) including the hybrid starter, overcharging protector (OCP), and switch controller (SWC). The proposed hybrid starter employs the power-on-reset to accurately control the activated and deactivated moments of the SWC, thus generating a system supply voltage (V-SYS) within the stable operating voltage range. The proposed OCP employs the diode-connection and Schmitt trigger schemes to monitor the voltage of a storage device (V-STG) in real time, thereby protecting the IC from being damaged without using either a capacitor or Zener diode, which causes the additional area or reverse leakage current, respectively. The proposed SIMO converter with the PMC was fabricated using 0.18-mu m CMOS process. The measurement results show that V-SYS values at the activated and deactivated moments of the SWC are 1.798 V and 1.510 V, respectively, both of which are within the stable system voltage range for 1.8 V devices. In addition, the measured maximum V-STG is 5.892 V, which is much lower than an absolute maximum rated voltage of 9.2 V for 5 V devices. Furthermore, the measurement results reveal that the hybrid starter allows the proposed SIMO converter to be properly restarted immediately after V-SYS is shorted to ground, while the OCP safely protects the SIMO converter even when the storage device is removed from the IC while charging. Therefore, the proposed SIMO converter with the PMC is suitable for energy harvesting systems that require high reliability.