Why does a tube light have a glow delay compared to CFL?« Back to Questions List


Tube light falls under the category of conventional fluorescent lamp. CFL stands for Compact Fluorescent Lamp. Flicker start is a common feature of conventional tube lights. CFL emits light immediately on switching on unlike conventional fluorescent lamp. 

Tube lights and CFLs work based on same principle. Both have fluorescent phosphor coated glass tubes that are filled with a mixture of inert gas argon and mercury. However, the chemical combination of the coating materials used in tube lights and CFL are slightly different that differentiate the quality of light emitted.   In order to produce light, this gas mixture inside the glass tube needs to be energized.  This gas gets excited by emission of energetic electrons from the cathodes at the ends of the tube. The phosphor in the material coated inside the glass tube starts glowing and emits light when the phosphor is bombarded by the excited gas atoms.  The process is a self-sustainable one. Once the process is started, the excited gas atoms and the electrons keep on repeating the excitation process. 

The release of energized electrons from a heated cathode and excitation of gas atoms are accomplished by an instantaneous high voltage pulse generation by a ballast circuit. In a conventional tube light,  this is carried out by application of a magnetic choke (voltage converter) and bi-metallic strip starter combination. The ballast circuit makes use of self-inductance of an iron core choke coil and a discharge lamp type automatic starter switch to trigger.  An inductance has a slower voltage build up due to longer time constant which leads to more time for release of electrons from the cathode.  Further, these characteristics need more than one attempt to release electron and  excite the gas mixture. This is the cause for startup flicker and slow discharge of light. Apart from this negative feature, the power consumption for this method is also higher. 

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Compact Fluorescent Lamp (CFL) has a built in integrated electronic ballast comprising of an array of AC-DC-AC converters and oscillators. This ensures fast emission of electrons and quick excitement of gas atoms that leads to fast emission of visible light. 

However, it may be noted that electronic ballasts that can be used along with tube lights are presently available. This has replaced traditional chokes. These electronic devices generate higher voltage faster to extract high speed electrons which excite the gas atoms. This modern process leads to light emission without flickering. These ballasts are termed ‘rapid start ballasts’ as the entire process is faster and do not lead to flickers.  Why shape of CFL lamp differs from incandescent lamp?

What are the advantages and ill-effects of using CFLs?

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