29.11.2014
The increased number of complaints from the readers regarding burning LEDs associated with my earlier posted transformerless 1 watt LED driver circuit, compelled me to solve the issue once for all.
The complaints that I kept on receiving were undoubtedly because of the initial switch ON surge which kept destroying the 1 watt LEDs connected at the output of the circuit. The above problem is pretty common with all capacitive type of power supply, and the problems has created  a lot of bad reputation to these types of power supplies. Therefore normally many hobbyists and even engineers opt for lower values capacitors fearing the above consequence in case larger value capacitors are included. If the switch ON surge is tackled appropriately, these circuits would become spotless and could be used without the fear of any damage to the output load, especially an LED. During switch ONs, the capacitor quite acts like a short for a few microseconds until it gets charged and only  then it introduces the required reactance to the connected circuit so that the appropriate amount of current only reaches the circuit. However the initial few micro second short condition across the capacitor inflicts huge surge to the connected vulnerable circuit and is sometimes enough for destroying the accompanied load.
The above situation can be effectively checked if the connected load is inhibited from responding to the initial switch-ON shock, or in other words we can eliminate the initial surge by keeping the load switched OFF until the safe period is reached. The next stage which includes the two 10 K resistors, two capacitors, transistor and the zener diode form the parts of the important delay timer circuit. When power is switched ON, the two resistors and the capacitors restricts the transistor from conducting until both the capacitors get fully charged and allows the biasing voltage to reach the transistor base, illuminating the connected LED after a delay of about 2 seconds. More number of LEDs may be connected in series for increasing the power output, however the number may not exceed 25   nos. The above concept looks great but is probably not working well with the proposed high voltage capacitor power supply.
The resistors in the above circuit are unable to withstand high current requirements, same is true for the transistor which also becomes quite hot in the process. Even though the above concept failed to work it doesn't mean the high voltage capacitive power supplies are completely hopeless. It's by using  many 1N4007 diodes in series at the output or in parallel to the connected LEds. The above circuit is yet to be tested for many months, so these are still early days, but I don't think the surge from the capacitor will be high enough to blow the 300V, 1 amp rated diodes.
The first circuit attempt which seemed to be vulnerable itself to surge causalities can be effectively remedied by replacing the power BJT with an 1 amp mosfet as shown in the following diagram. The mosfet being a voltage controlled device, here the gate current becomes immaterial and therefore a high value 1M resistor works perfectly, the high value makes sure that the resistor does not heat up or burn during the initial power switch ON. A little investigation revealed that the high voltage transistor in the first diagram is actually not needed, rather it can be replaced with a high current Darlington TIP122 transistor as shown in the following diagram.


The high voltage surge from the capacitor becomes ineffective against the high current specs of the transistor and the LEDs and no damage is caused to them, in fact it forces the high voltage to drop to the specified allowable safe limits of the LEDs and the transistor. The TIP122 also allows the use of a high value base resistor thereby making it sure that it does not become hot or blow off in the course of time, it also allows the inclusion of a low value capacitor at the base of the transistor for implementing the required delayed switch ON effect.
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Use the form below to delete this Flers Album Photo Dun Petit Matin Dautomne Autour Du Plan Deau image from our index. Even the promising and the most talked about LED technology is perhaps unable to produce lights equal to the modern electronic fluorescent ballasts lights.
Just a decade ago electronic ballasts were relatively new and due to frequent failures and high costs were not generally preferred by everyone. So what’s the exact advantage of using electronic flourescent ballast compared to the age old electrical ballast? 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. 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.
Electronic ballasts on the other hand are just the opposite as far as efficiency is concerned. 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. Its working principle of the proposed electronic flourescent ballast is rather straightforward.


The following illustrations clearly explains how to build a homemade electronic 40 watt electronic fluorescent ballast circuit at home using ordinary parts. 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. The power supply section of the circuit discussed here remains exactly identical to the previous configuration, except the inclusion of the "switch ON delay feature" which has been exclusively designed by me and added in the circuit for rectifying the burning LED problem (hopefully). And that's exactly what I have  included in this proposed surge protected hi-watt LED driver circuit.
It also facilitates a relatively low value capacitor to be used for the required delay ON surge suppressing feature. The circuit of one such electronic tube light is discussed here, with efficiency better than LED lights. 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. To understand the differences correctly it is important to know how ordinary electrical ballasts work. 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. 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. 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. The PCB layout of the proposed electronic fluorescent ballast is also provided along with the torroid and the buffer choke winding details. Once this conduction is connected the current consumption to sustain this conduction and the illumination becomes minimal. 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.



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Comments Uv tube driver rack

  1. PIONERKA
    Dip a sponge into the glue on the screw of nose pad and glue may.
  2. lala_ASEF
    Issue is that reflection is caused by an impedance mismatch.