This paper presents a transistor-level design of a power management electrical circuit for asynchronous electrostatic energy harvester. The conditioning circuit of the harvester is based on a charge pump and a fly back circuits. The designed power management block implements the concept of adaptive behaviour of energy harvester, allowing it to operate in an optimal mode in environment where the magnitude of the vibrations may change in time. For the first time, such a system is designed to operate at high voltage (up to 30 V). However, this paper does not concern the design of electromechanical transducer. The IC design has been carried out in 0.35um high-voltage CMOS technology, and has been validated by a coupled VHDL-AMS/SPICE simulation. The control system average power consumption is less then 0.9uW, whereas the average harvested power is approximately 1.1uW for 14V operation voltage.