the mechanism of electronic ballast

Instructed by: Rethwan Faiz

Prepared By

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

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

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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

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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

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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

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

Half bridge configuration The resonant circuit strikes on the lamp

C2

C1

L

Before strike on the tube has very high resistance and effectively it is an open circuit

Operation at a high frequency preheats the filaments Operation near resonance produces high voltage across C2 and

strikes on the lamp Ref <start1>

In the steady state the lamp resistance reduces greatly current is controlled by L & C1Ref <steady>

i(R3)

V(C2)

Self oscillating circuit IC driven circuitNew Capacitor Couple Converter

(CCC) circuit developed at the HKU Power Electronics Lab

Simple & low cost

Easy to design

Low loss – zero voltage switching Reliable – automatic power limiting

Load101

Encyclopedia http://www.britannica.com/

Books http://www.knovel.com/knovel2/default.j

spCompany web sites

http://www.irf.com/technical-info/ IEEE/ IEE papers

http://ieeexplore.ieee.org/Xplore/DynWel.jsp

1. http://home.howstuffworks.com/2. http://www.repairfaq.org/sam/flamp.htm#int03. “HID Electronic Ballast Testing” Public Interest Energy Research

Program (PIER) Program, California, USA4. T. Ribrarich “A Systems Approach to Ballast IC Design” IR

Technical notes.