Contents 1. Types of Ballast 2. Basics of Electronic Ballast 3. Starting Methods 4. Fluorescent tube 5. Lamp Structure 6. Working of lamp 7. Startup Circuit 8. Advantages of EB
Types of Ballast 1. Electromagnetic 2. Hybrid 3. Electronics Purpose of EB a. Provide a start−up voltage, b. Maintain a constant current, c. Assure that the circuit will remain stable.
Basics of Electronic Ballasts C1 L C2 Halfbridge configuration The resonant circuit strikes on the lamp
A. Instant start electronic ballastsStart lamps withoutdelay (<0.1 seconds) orflicker by providing astarting voltage that issufficiently high to start adischarge through thelamps without the needfor heating lampelectrodes. , the startingvoltage is about 600V.Lamps operated byinstant start ballaststypically operate 10,000to 15,000 switch cyclesbefore failure.
B. Rapid start electronic ballastsStart lamps quickly (0.5– 1.0 seconds) withoutflicker by heating thelamp electrodes andsimultaneously applyinga starting voltage.Lamps operated by rapidstart ballasts typicallyoperate 15,000 to20,000 switch cyclesbefore failure.
C. Programmed start electronic ballastsProgrammed startballasts are designed toprovide maximum lamplife in frequent lampstarting applicationssuch as in areas whereoccupancy sensorcontrols are used. .Lamps operated byprogrammed startballasts typically operateup to 50,000 switchcycles before failure.
Fluorescent tubes Much more efficient than incandescent lamps : 2 to 4 times more efficient. Less energy required to operate. Eco-friendly for environment. The lamps are much cooler than incandescent lamps.
Lamp Structure The lamp is a sealed tube containing mercury vapor and some inert gases such as argon at very high pressure The inside of the tube is coated with phosphor At the ends of the tube there are filaments or electrodes
How does it work? When the tube is off it does not conduct It is turned on by a high voltage which excites the gas inside the tube Once the tube conducts on a lower voltage is sufficient to maintain conduction The electric current passes through the gas and emits UV, the internal phosphor coating converters the UV to visible light The color of the light cab be varied by different combinations of phosphors
Lamp starting When the lamps is off the tube is non -conductive The tube must be excited or started by a high voltage After the lamps is started the lamp voltage drops A current limiting “ballast” is needed in between the power source and the lamp