This paper presents the simulation of low voltage energy harvesting using an ac/dc step up converter with the power electronic simulation software PSIM©. The direct ac/dc conversion is achieved with boost and buck boost converters connected in parallel which are operated in positive and negative half cycles respectively. The input supply is from micro generators which scavenge energy from ambient which is of the order of milli volts. The output is to be supplied to an electronic load which has an input supply voltage of 3.3 V. The design of the converter and the simulation with a closed loop control is being realized.