A ballast is the big bulky box like structure on fluorescent lamps. The electric ballasts of the past have been replaced by PCB based electronic ballasts. The conglomeration of PCB technology and electronics has been helpful in achieving this.
What a ballast does
The ballasts are used to limit the electric currents in fluorescent lamps. The lamps are filled with mercury vapor. Due to negative resistance characteristics of the mercury vapor, it draws heavy currents in the lamps, which can destroy the lamp. For limiting these dangerous amounts of electric current, ballasts are used.
Electrical ballasts
The traditional ballasts used to be either inductive or resistive in nature. Inductive ballasts produced high voltages across discharge tubes that ionize the gas and limits the amount of current to save the lamp. One of the major disadvantages with the ballasts was the frequency at which the lamp operates. The electrical ballasts operating at low frequencies affected the performance of the lamps. Flicker could be observed in the lamps due to low frequency operation. Also, the windings used to be under constant stresses producing an irritating humming noise during their operation.
PCB based electronic ballasts
But now the tide has changed and with the development of solid state electronics and PCB technology, electronic ballasts are replacing the electrical ballasts and the the latter is on the verge of extinction.
The electronic ballasts are based on the principles of SMPS technology, pulse width modulation or frequency modulation techniques. The electronic components in the form of switching devices like MOSFETs, IGBT or transistor and diodes, transformers, etc. are embedded on a PCB. These circuits in addition to limiting the amount of current, increase the frequency of the power to high levels. As a result, flicker in the lamp is reduced and buzzing sound from the ballasts is also eliminated. Due to absence of preheating technique, the lamp life is increased.
Advantages of PCB electronic ballasts
- With the advent of PCB electronic ballasts, which are relatively small sizes of the components, the electronic ballasts have become smaller and lighter than electric ballasts.
- The lamps have become sleeker and the thickness has been reduced giving the same illumination.
- They are comparatively inexpensive due to mass production techniques and low cost of the components.
- Flicker and buzzing in the fluorescent lamps is reduced considerably.
- They are more efficient than the electrical ballasts and result in saving of power and lead to long life of lamps.