07-12-2012, 02:07 PM
Electronic Ballast Fundamentals
[attachment=42928]
Fluorescent tubes
Much more efficient than incandescent lamps : 2 to 4 times more efficient
The lamps last a lot longer – 10k to 20k hours versus 0.75k to 1k hours for an incandescent lamp
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 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
Conventional starter switch
A mechanical starter switch together with an inductive ballast start up the lamp
The starter switch is a small discharge bulb containing a gas like neon.
When connect to a voltage source the gas breaks down and the switch glows
The heat generated bends the bimetallic switch and closes it
One the switch is closed the glow is turned off and the bimetallic switch cools down and opens
When the switch opens a series connected ballast provides a high voltage and strikes on the tube
High frequency ballast
Conventional ballast produces 100/120Hz flicker
High frequency ballast is more efficient than magnetic ballast [3]
High frequency ballast, like most power electronics products, has smaller size and weight
Integrates ballast and starting functions
[attachment=42928]
Fluorescent tubes
Much more efficient than incandescent lamps : 2 to 4 times more efficient
The lamps last a lot longer – 10k to 20k hours versus 0.75k to 1k hours for an incandescent lamp
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 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
Conventional starter switch
A mechanical starter switch together with an inductive ballast start up the lamp
The starter switch is a small discharge bulb containing a gas like neon.
When connect to a voltage source the gas breaks down and the switch glows
The heat generated bends the bimetallic switch and closes it
One the switch is closed the glow is turned off and the bimetallic switch cools down and opens
When the switch opens a series connected ballast provides a high voltage and strikes on the tube
High frequency ballast
Conventional ballast produces 100/120Hz flicker
High frequency ballast is more efficient than magnetic ballast [3]
High frequency ballast, like most power electronics products, has smaller size and weight
Integrates ballast and starting functions