PURPOSE: To make one transformer commonly available to both high power factor type and constant power type leakage transformer ballasts by connecting one end of an electromagnetically bonded second coil to the middle of a first coil, and providing a power supply connection terminal in the vicinity thereof.

CONSTITUTION: A condenser 118 is put in connection between both ends of a first coil 102, and by placing a power supply 114 in connection between the end 102c and a power supply connection terminal, and by placing a lamp 120 in connection between one terminal 104b of a second coil 104 and the terminal 102c, a high power factor type leakage transformer type ballast is obtained. By serially placing the condenser 118 and the lamp 120 in connection between both ends 102a and 102c of the first coil 102, and by placing the power supply 114 in connection terminal between the 102c of the coil 102 and one terminal of the coil 104, a constant power type leakage transformer type ballast which is actuated in the same way as a transformer + choke type one, can be obtained.