This paper presents a performance enhancement feature for a novel power management circuit to generate 1.8 V from the low DC voltage rectified at the output of the vibration-based electromagnetic (EM) energy harvesters. The proposed 180 nm circuit utilizes a low voltage charge pump based boost converter with variable output-stages, and an autonomous regulator circuit with negative feedback topology. 2 and 3 stage charge pump options in the variable stage configuration has been validated to extend the supported input voltage range at the same load, or alternatively maintain higher efficiency operation at a higher load range. The simulation results showed that under no-load condition the output voltage reached to 1.8 V for input voltage of 0.65 V and 0.48 V with 2 and 3 stage outputs, respectively. The power conversion efficiency of the power management circuit can be kept stable around 55% by switching from 2 to 3 stages after 3.5 mu A.