CFL Driver Circuit TESTING STAGE Part2

[s4w2099]

The other one was getting kind of long so I decided to create another one.

Ok, flux. I have done it. I got a ballast and made the circuitry. There is a little discrepancy though. The DC side says that I am using up 17 Watts and the AC side says 18 Watts so I dont know how to calculate the efficiency on this one.
Both of my meters are different models so maybe thats the problem. I am still waiting on the ferrite core transformer so that I can actually run it at 20Khz.

I think that I am kind of cheating here because this is basically an inverter connected straight to the ballast and then to the tube. But I dont know if the ballast will work with higher frequency when the ferrite core transformer arrives.

I have a question. will the ballast tolerate that kind of frequency? in the label it specifies that its to be used with 60Hz. Injecting 60 Hz to it and it works wonderfully.

Thanks

[Flux]

I think it highly unlikely that a conventional inductive ballast will work much beyond 60 Hz.

If your ballast is an electronic one then it will work very well, it will incorporate all the driver circuitry and be designed for high efficiency. All you need to do is provide the voltage transformation from 12v to that needed by the ballast.

Most will work perfectly well on dc, the input is just a rectifier. You can use a dc converter or an inverter to fairly wild frequency ac as long as the peak ac volts are within reason.

The more sophisticated electronic ballasts incorporate power factor correction circuits that get confused with square waves. These particular ones will object to modified sine( square) wave inverters but will work perfectly well if you rectify the output and provide some measure of smoothing.

The down side is the high cost of these ballasts but if you can stand the cost a simple dc/dc converter feeding an electronic ballast is very effective ( you let someone else do the awkward tube drive circuit).

Silicon Chip did a 40W unit including the dc converter and ballast. This link is to a modifications page but you should be able to find your way back to the original article.

http://www.siliconchip.com.au/cms/A_104436/article.html

Flux

[s4w2099]

Ok, so this should be easy then. My circuitry can act as a DC-DC converter stepping up the frequency, rectifying with high speed bridges and a good filter and then feed that to the electronic ballast. My circuit cost me less than 5 bucks so I will keep using it.

I will try to get a hold of such ballast.

[Nando]

I went to read your first message to see what was going on.

Since you are using a 12 volts supply to make a fluorescent lamp, you may produce around 160 volts DC or 300 volts DC for 115 or 230 volts regular electronic ballast lamps.

The lamps using the magnetic ballast operate at 60 or 50 HZ depending where they are sold ( different inductance).

These ballasts do not accept high frequency input power and their design is very dependent on the input frequency, basically they are designed for 45 of 55 HZ up 10 to 20 additional Hz.

The way I have made low voltage fluorescent lamps if to have 2 semiconductors driving in push-pull a transformer producing 300 volts AC, then a resonant inductance in series with a isolating capacitor plus a resonant capacitor in the pins of the lamp, using the filaments in series.

In addition I used a small transformer with a primary that is in series with the resonant inductance and two secondaries that feed the semiconductors to turn on with positive feed back.

There is another simple circuit that pulses once every 3 to 5 milliseconds to pulse one of the semiconductors ON to initiate the oscillations and the circuit is then disabled.

Basically is the initial high voltage totem pole electronic ballast converted for lower voltage.

The transformer is designed to saturate at around 1/2 the operating frequency and it will operate in the linear region, always, reducing the losses to a minimum.

There many companies making Integrated Circuits for fluorescent lamps and many DO include Power Factor correction for better energy savings.

85 to 93 % efficiency can be obtained.

One can use a single transistor to make a fluorescent lamp with a small transformer

and a few resistors, though the efficiency is lower and the lamp life 50 to 75 %lower due to not bi-directional lamp current pulses

Nando

[s4w2099]

Thanx for the information. My two transistor DC-DC converter is ready and its output in DC is about 190V. This is a full wave version using PWM. I ordered an electronic ballast to hook it up to this converter. It should make a good fixture once they are together.

[JW]

Hi all,

 I ordered a 12v cfl on the net last week, got it a couple days ago. Anyhow I have found theres something special about the bulbs. Ive got 2 13watt bulbs, one is driven by a ballast and 120vac @60hz. The circuit is kinda weird. Its got a small transformer "in series" with the hot and the circuit completes thru the bulb. That works fine on 120vac. The other is powered with 12 volts dc to a circuit board and from there runs the 12v cfl with what appears to be 34volts ac.

 So I decided I was going to 'interchange' that bulb of the circuit that drives the 12v with the 120vac one. So I have the 120v cfl and the 12v cfl, both are 13watts. But the 120v cfl absolutly will not work with the 12v circuit board.

JW

   

[Nando]

Some lamps have Kp 85 (radioactive Kripton) to assist in the turn on, also some of the low voltage inverters have a spike during switch to assist in the turn ON.

Also some have a double filament, some do not have any, just an electrode at each end.

Nando

[willib]

s4w2099, i'm not sure if anyone mentioned it or not , but you can find some ferrite core transformers in old pc monitors , i dunk them in ascetone to dissolve the "glue" then you could rewind one?

i've also found some very usefull ICs in monitors , like Fets and even found two serial EEPROMS with sockets , little 8 pin jobs...

[s4w2099]

Thanx for the info but unfortunately I tried to wind one and I failed. The transformer was vibrating badly.

I dont know the specifics about winding a high frequency transformer.

I am on hold right now with these CFLs until my electronic ballast gets here. I got it for 2USD on ebay.

:-D

[Norm]

  Okay Nando....I had this 24 inch tube GE ....

LiteStik or something like that, anyway it was

34 watt...it finally started having a hard time

turning on...confounded blinking, never really turning  on

......so I replaced it with a

Lights of America 120v~60Hz 17w 300mA, takes a

bulb replacement No. RB17T8 or F17T8 (Model 7020 E

 75 watt output and it is considerably brighter

than the 34 watt ever was...also just turns on

seemingly instantly so I was thinking would this

work fairly well with a 12 volt 225 watt inverter?

 Even with the power consumed by the

inverter...I'd be a lot farther ahead than using

the 34 watt with inverter or a 12 volt fluorescent light,

 and would this lamp maybe have

this KP85 that you spoke of ?

     (Electronically Illiterate  ( :>)Norm ))

[JW]

Hi s4w2099,

 I got my complete lamp assy for 12 bucks, the driver circuit with matching 12v 13watt bayco bulb in a nice hand wand dealee. It had a fused cigerette lighter adaptor.

 The other 120vac 13watt bulb has a special series ballast that works with 120vac. I swear to God that im scared to plug it into my only remaining invertor(600watt). It has something called 'bounce bulb technology' and the last couple of times I tried to start it with an invertor, sparks shot out of the back of my 3000watt invertor(both of the ones I tried) at the exact same intervals of the lamp fliker before the the invetor shut down.(for good)...

 Im going to try a standard 23watt screw in CFL with the invertor. Im curious to see if its a series ballast with the 120vac, but im sure it wont fliker before starting, By the way the 13watt bulb running on 120vac(bounce bulb, series transformer ballast[the one that flikers at start up][ im not sure if this is from the bulb or ballast])was twice as bright but with more of an orange color, once it lit, the 13watt DC-CFL, @12volts with the circuit driving it, was dimmer and more of a blue color.

JW

[s4w2099]

Ok, I got my electronic ballast. Just as flux said it also works with DC.

One thing that I noticed is that when it is working with AC straight from the converter it draws 2.2Amps from the 12V battery. In the other hand, when I rectify and filter the output of the converter it only uses 1.8Amps from the 12V battery. There is absolutely no difference in the amount of light emitted from both methods. Both ways work with full intensity.

I dont quite understand whats happening here. Please someone explain.

Thanx

[commanda]

Is your multimeter a true RMS type, and can it handle ac at the frequency you're working at?

Cheap multimeters are set up for working with pure sine waves. Once you deviate from that they could read almost anything.

Amanda

[s4w2099]

Yes it is true RMS. I am still working at 60Hz from my converter. I measured the power draw from the battery and the power draw from the lamp at the other side of the transformer. by dividing the output power by the input power I get that the efficiency is about 87.5%. I think that that is not acceptable for this application.

Since I still have to speed up the frequency I guess that I still have one more chance to get the efficiency in the 90s.

I just have to wait for a high frequency transformer, but so far so good. No sparks or smoke from the circuit yet. :-D

[Nando]

I don't know, high brightness could be due to a tri-phospor coating with long time emissivity compared to the energy pulses.

KP85 allows lower voltage triggering because the radioactivity in the gas, it has a median life of about 18 years.

To see what is going on, data has to be taken.

Nando