Different type of CFLs around usThe term ‘CFL’ stands for Compact Fluorescent Lamp. It is also known as compact fluorescent light, energy-saving light, and compact fluorescent tube. The CFL was initially designed to replace the incandescent lamp in terms of its compactness as well as energy efficiency. The basic construction of a CFL consists a tube which is curved/spiralled to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp.

The most valuable property of this CFL is its energy efficiency and life. A CFL has many advantages if compared to the old filament bulbs. For example – It has lesser power rating (almost 80 percent) and a higher life span ( nearly five to fifteen times). Though, it has a higher purchase price than an incandescent lamp, it can save over five times its purchase price in electricity costs over the lamp’s lifetime.

There are few disadvantages too. It takes more time to start and price is higher, if compared to old filament bulbs. In addition, It does not comes in dark shades too. Like all other fluorescent lamps, CFLs contain mercury, which complicates their disposal.

Inner view of a CFL

A CFL uses vacuum pipe which is principle wise same to the strip lamps (commonly known as Tube light) . Tube has two electrodes on both ends which is treated with Barium. Cathode is having a temperature of about 900º C and generates a beam of electrons which is further accelerated by potential difference between electrodes. These accelerated electrons strike Mercury and Argon atoms which in turn results in the arise of a low temperature plasma. This process initiates the radiation of Mercury in Ultra violet form. Tube’s inside face contains ‘Luminophore’ whose function is to convert Ultra violet light into visible light. This tube is fed with AC power supply which facilitate the changing functionality of Anode and Cathode. The CFL also consists a switched mode converter. It functions on a very high frequency and acts as a replacement of ballast (choke) and starter assembly.

it diagram of PCB of CFL

How the Circuit works :

The PCB consists the following components :

  • Bridge rectifier made up of diode 1N-4007
  • Suppressor for suppressing interference
  • Filter capacitor
  • Fuse point
  • Supply point

The starter segment Starting section comprise of a Diac, C2, D1 and R6. The components D3, R3, D2 and R1 work as a protection circuit and the rest as normal operation circuit. You have to keep the following terminology in mind :
(a) D refers for diode,
(b) R refers for Resistor
(c) C refers for Capacitor, and
(d) Q stands for Transistor

Starting Phase :

The Diac, C2 and R6 send a voltage pulse to Q2 Transistor’s base which causes it to get its threshold value and it starts operating. As soon as the operation starts, the D1 diode blocks the whole section. Capacitor C2 is also discharged (after charged to its full value) each time the transistor Q2 operates. Therefore after its first start, There is not enough energy left for reopening of Diac. Further, the transistors are excited with the help of TR1 transformer. As the voltage is raised from resonant circuit (L1, TR1, C3 and C6), the tube lights up as soon as resonant voltage is specified by capacitor C3 (which feeds Filaments). At this moment the voltage C3 is over 600V.

Normal Phase :

Just after the ionisation of gas present in the vacuum-pipe, the practical shorting of capacitor C3 is carried out. This results in stepping down of the voltage. After that C6 starts driving the changer. A very small voltage is generated by this changer, yet it is sufficient to run the lamp in ‘ON’ condition. Under regular running condition, if the transistor comes in OPEN state, The current being fed to TR1 keeps increasing till the core of transformer saturates, and thus the feed to base drops down resulting it to close the transistor. Immediately after this process, the second transistor is excited by reverse winding of TR1 and so the process goes on.