Electronic Ballast Design

I had made a simple 12 V electronic ballast using a simple 555 timer , a flip flop, a single 2n3055 transistor ans a general purpose 15-0-15 to 220V 1 amp transformer. The circut was able to drive simple old 6W tubelight's but when it came to CFL tubelight's it just wouldn't work. Could someone tell me how to make those CFL's work. Will a simple inductor in series help. The frequency of my inverter was approximately 5Khz. It was also able to drive 2 small 6 W tubelight's(not CFL) simultaneously.