How does a compact fluorescent lamp consume less electricity than conventional fluorescent lamps and bulbs?

Fluorescent lamps are based on the phenomenon of gas discharge between two electrodes at the ends of the glass tube.Generally these tubes contain a little mercury in the low-vapour phase.When sufficiently large voltage is appiled between the electrodes,some atoms of the vapour get ionised.
The process of ionisation starts with stray electrons and ions that are generally present in the vapour.The electron-ion pair so formed gets accelerated towards electrodes of opposite electrical polarity,gaining kinetic energy.When they collide neutral mercury atoms,some of them are ionised and some are electronically exicted.Excited atoms release their energy in the form of electromagnetic radiation,part of which is in the visible and in the infrared regions of the spectrum.But it is rich in the visible ultraviolet region.
         A fluorescent light source has the inner surface of its glass tube painted with a material called phosphor.Zinc sulphide is the commonest example of a phosphor.But phosphor used in particle are complex mixtures of the sulphides and phosphates of barium,strontium and rare earth elements.These phosphors have the property of absorbing ultraviolet component of the radiation and re-emitting a major fractrion of the corresponding energy in the form of visible light.This enhances the lamp's efficiency of converting electrical energy into visible light.
         The ordinary fluorescent lamp works with a supply voltage of about 220 volt.Since the start of the discharge process demands a little higher voltage,it also employs a starter and ballast(a choke coil) that together produce the desired voltage.On the other hand, the compact tube works at about 400 volt(constant), which is produced by a transformer arrangement embedded in its base.
         Higher efficiency means low consumption of electrical energy.A filament lamp has the lowest efficiency, because is is based on the fact that a material body heated to a high temerature emits radition of all wavelenghts.This radition is richer in the infrared part of the spectrum and since there is no mechanism of converting this into visible light, it has poor efficiency.The three types of lamps may have a typical efficiency ratio of 8:6:3.