People have grown up with the sights and sounds of fluorescent lamps buzzing to life after a few attempts. As the new wave of energy saving appliances gripped the world, technology made the fluorescent lamps shrink in thickness as well as reduced the number of attempts made by lamps to shine their brightest. Today many homes use energy Saver CFL lamps and fluorescent tubes which start giving light the moment they are switched on. This instantaneous production of light is achieved by the use of electronic ballasts.
Electronic Ballast is a device which controls the starting voltage and the operating currents of lighting devices built on the principle of electrical gas discharge. It refers to that part of the circuit which limits the flow of current through the lighting device and may vary from being a single resistor to a bigger, complex device. In some fluorescent lighting systems like dimmers, it is also responsible for the controlled flow of electrical energy to heat the lamp electrodes.
For a lighting device based on electric gas discharge to work, the ionization of gas in the tube is necessary. This phenomenon takes place at a relatively high potential difference and/or temperature than the normal operating conditions of the lamp. After the arc is set up, the conditions can be brought down to normal. To achieve this, three types of methods are generally employed: pre-heat, instant start and rapid start. In pre-heat, the electrodes of the lamp are heated to a high temperature before the voltage is impressed upon them through a starter. Instant start ballasts were developed to start lamps without delay or flashing and use an initial high voltage in place of raised temperatures. Rapid start ballasts make a tradeoff between pre-heat and instant start and use a separate set of windings to initially heat the electrodes for a lesser duration and then, using a relatively lower voltage to start the lamp. Another type, programmed start ballasts is a variant of rapid-start. Any of these starting principles may be used in the ballasts. Initially, when the gas is unionized, it offers a high resistance path to current. But after the ionization takes place and the arc is set up, the resistance drops to a very low value, almost acting like a short circuit. If all this current is allowed to pass through the lamp, the lamp would either burn out or cause the power supply to fail. Thus the ballast needs to perform the current limiting.
Types of Ballast:
There are mainly three types of ballasts: magnetic, electronic and hybrid. Magnetic and hybrid ballasts employ a copper coil wound on a magnetic core as their essential components, while electronic ballasts use solid state electronic circuitry to provide the proper operating electrical conditions to the connected lamps. A brief comparison is tabulated below: