Simple electronic fluorescent ballast circuits are difficult to find and build. A simple homemade electronic 40 watt ballast circuit is neatly explained in this article. The PCB layout of the proposed electronic fluorescent ballast is also provided along with the torroid and the buffer choke winding details.

Introduction


Even the promising and the most talked about LED technology is perhaps unable to produce lights equal to the modern electronic fluorescent ballasts lights. The circuit of one such electronic tube light is discussed here, with efficiency better than LED lights.



Just a decade ago electronic ballasts were relatively new and due to frequent failures and high costs were not generally preferred by everyone. But with passing time the device went through some serious improvements and the results were encouraging as they started becoming more reliable and long lasting. The modern electronic ballasts are more efficient and fail proof.

Difference between Electrical Ballast and Electronic Ballast


So what’s the exact advantage of using electronic flourescent ballast compared to the age old electrical ballast? To understand the differences correctly it is important to know how ordinary electrical ballasts work.

Electrical ballast is nothing but a simple high current, mains voltage inductor made by winding number of turns of copper wire over laminated iron core.

Basically, as we all know a fluorescent tube requires a high initial current thrust to ignite and make the electrons flow connect in between its end filaments. Once this conduction is connected the current consumption to sustain this conduction and the illumination becomes minimal. Electrical ballasts are used just to “kick” this initial current and then control the supply of the current by offering increased impedance once the ignition is completed.

Use of a Starter in Electrical Ballasts


A starter makes it sure that the initial “kicks” are applied through intermittent contacts, during which the copper winding’s stored energy is used to produce the required high currents.

The starter stops functioning once the tube gets ignited and now since the ballast is routed via the tube, starts getting a continuous flow of AC through it and due to its natural attributes offers high impedance, controlling the current and helping sustain optimal glow.

However, due to variation in voltages and lack of an ideal calculation, electrical ballasts can become quite inefficient, dissipating and wasting a lot of energy through heat. If you actually measure you will find that a 40 watt electrical choke fixture may consume as high as 70 watts of power, almost double the required amount. Also, the initial flickers involved cannot be appreciated.

Electronic Ballasts are More Efficient


Electronic ballasts on the other hand are just the opposite as far as efficiency is concerned. The one which I built consumed just 0.13 Amps of current @ 230volts and produced light intensity that looked much brighter than normal. The have been using this circuit since last 3 years without no problems whatsoever (though I had to replace the tube once as it blackened at the ends and started producing lesser light.)

The current reading itself proves how efficient the circuit is, the power consumption being just around 30 watts and an output light equivalent to 50 watts.

How the Electronic Ballast Circuit Works


Its working principle of the proposed electronic flourescent ballast is rather straightforward. The AC signal is first rectified and filtered using a bridge/capacitor configuration. The next comprises a simple two transistor cross-coupled oscillator stage. The rectified DC is applied to this stage which immediately starts oscillating at the required high frequency. The oscillations are typically square wave which is appropriately buffered via an inductor before it is finally used to ignite and illuminate the connected tube. The diagram shows a 110 V version which can be easily modified into 230 volt model through simple alterations.

The following illustrations clearly explains how to build a homemade electronic 40 watt electronic fluorescent ballast circuit at home using ordinary parts.


40 watt electronic fluorescent ballast circuit

PCB Component Layout

WARNING: PLEASE INCLUDE A MOV AND A THERMISTER AT THE SUPPLY INPUT, OTHERWISE THE CIRCUIT WILL BECOME UNPREDICTABLE AND MIGHT BLOW-OFF AT ANY MOMENT.

ALSO, MOUNT THE TRANSISTORS OVER SEPARATE, 4*1 INCH HEATSINKS, FOR BETTER EFFICIENCY AND LONGER LIFE.

PCB Track Layout


PCB design for 40 watt ballast

Torroid Inductor

T13 torroid winding details

Choke Inductor

choke filter EMI

Parts List


R1,R2,R5 = 330K MFR 1%

R3,R4,R6,R7=47 Ohm, CFR 5%

R8=2.2 Ohms, 2watts

C1,C2=0.0047/400V PPC for 220V, 0.047uF/400V for 110V AC input

C3,C4=0.033/400V PPC

C5=4.7uF/400V Electrolytic

D1=Diac DB3

D2……D7=1N4007

D10,D13=B159

D8,D9,D11,D12=1N4148

T1,T2=13005 Motorola

Heatsink is required for T1 and T2.

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