A novel discrete dimmable electronic ballast for a fluorescent lamp without changing the original power wiring system is developed. We propose a new method that detects the number of times the power-switch is pressed to make the electronic ballast generate the corresponding power rating. A dimming module realizes the proposed method and makes the DC-AC inverter in a round-robin manner to output the respective power rating. A prototype of the discrete dimmable electronic ballast for a T5 fluorescent lamp of 28W under 110VAC/60Hz, for generating a four-state power rating is developed to demonstrate the feasibility of this approach.