This paper describes the high efficiency inverter ballast circuit using very cheap microprocessor, which has been developed by the author. A variety of soft-switching techniques have been proposed to reduce the switching losses and EMI publems that accur with higher switching frequencies in switched inverter ballast 1be inverter ballast circuit, which employs a temperature sensing circuits has been also proposed to improve starting performance of the fluorescent lamps. That is, the inverter ballast circuit, which employs a soft-starting circuits and soft-switching techniques to implement the power factoc correcticn and to mitigate of power-loss and iocrease a life time of the fluorescent lamps, has become an attractive performance forballasting the fluorescent lamps. In this paper, the operation and the control of the inverter ballast are described in detail and experimental results are presented. As the experimental results, when enviroment temperatture is at TEX>$-40^{circ}C$</TEX>, the inverter ballast circuit has low THD(4.8%) of the input current and large power factor(98%) of the lamp current. The proposed improved ballast circuit awears to be a good performance for ballasting fluorescent lamps. lamps.