Round LED Driver

Wrong !!

I recently converted mine and a LED driver will not work. They will flash. You need a ac transformer or whatever you want to call em with a va to suit the lamps.

I ended up renewing the lamp holders and getting rid of transformers to go 230v.

Well that is interesting. I mean LEDs are DC devices and you are saying proper driver did not work. Something was obviously not matched, that does not mean I am wrong, it just means this one case did not work. Most GU 10 type LED lamps incorporate a rectifier so they will work off AC or DC.
 
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Well that is interesting. I mean LEDs are DC devices and you are saying proper driver did not work.
It surely what is meant by "proper driver" (clear terminology is important). If it were a constant current source, and the "LED" were an LED lamp with internal current-controlling electronics, I can well imagine it not working - at all, or satisfactorily.

Kind Regards, John
 
"Well that is interesting. I mean LEDs are DC devices and you are saying proper driver did not work"

If it were a pure LED as in electronics, then you would need a LED driver (rectified supply).

The LED driver has an output of 12v approx. but the output is DC and not AC. So when you have an output of + and - and as mentioned the lamp has its own rectifier to convert ac to dc for the led. So how will the driver output match the lamps rectifier when its polarity connection is unknown. I used a LED driver where they had a DC output rated to suit the lamps and flashing as soon as switched on, the ac transformer was rated at 30 - 60va which was ok for the 12v 35w halogen lamps but when the 12v 5w LED lamp was fitted, if your'e lucky they may stay lit otherwise in my case they started flashng after approx 50 mins.
So in the end it was easier and cheaper in the long run to dump the transformers/drivers and fit new lamp holders for 230v LED's.
 
The LED driver has an output of 12v approx. but the output is DC and not AC. So when you have an output of + and - and as mentioned the lamp has its own rectifier to convert ac to dc for the led. So how will the driver output match the lamps rectifier when its polarity connection is unknown.
They use a bridge rectifier, so that the polarity fed to the LED elements is always correct, regardless of what polarity is fed to the lamp.

Kind Regards, John
 
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So if you connect dc supply the wrong way round from a driver, will the lamp will still work when the rectifier within the lamp is controlling the polarity. And the LED is a diode controlling the current flow direction (one way valve).

IE: + to - and - to +
 
some MRxx type led lamps I think dont care, possibly not all of them though.
Im not sure the 240 volt GU10 base ones would like DC, as winston seemed to state :rolleyes:, possibly the cheap 12 volt GU10 ones JohnW recently linked to, may work.
I have seen some MRxx type leds that had + and - on the base, I assume they were dc only, so would need plugging in the right way round

Some makers state

MR16 LED Bulbs
"All our SMD LED MR16 bulbs will work on AC or DC 12V
Compatible with solar power systems our LED bulbs have been designed to work safely to AC Voltage not exceeding 18V and a DC Voltage not exceeding 24V."
 
So if you connect dc supply the wrong way round from a driver, will the lamp will still work when the rectifier within the lamp is controlling the polarity. And the LED is a diode controlling the current flow direction (one way valve).
IE: + to - and - to +
As I said, they use a bridge rectifier (a ring of 4 diodes), like this:
upload_2017-1-1_22-47-59.png


As you can see, no matter what the polarity of the input is, the output (LED) is always the same (correct) polarity.

Does that help?

Kind Regards, John
 
Well done, JohnW happy new year.
I assume your drawings in turn, also explain how they run on DC even with the Alternating cycle of an ac supply,
Just going from the top drawing to the bottom drawing and repeating again and again so many times a second
 
Im not sure the 240 volt GU10 base ones would like DC, as winston seemed to state :rolleyes:
I'm not sure what you mean by "240V GU10 base ones". If you mean standard 230/240 GU10 LED lamps, I think people would struggle to find a 240V DC source, and 12V (DC or AC) would do little, if anything!
I have seen some MRxx type leds that had + and - on the base, I assume they were dc only, so would need plugging in the right way round.
That rather surprises me. I had always assumed that manufacturers who produced (ELV) LED lamps which were intended to work on DC (as well as AC) would include a bridge rectifier so that they were not polarity-sensitive. Otherwise, given that most of the standard lamp holders (other than, I suppose, screw ones) are not polarised (and even with polarity markings on the lamp base), one might expect that something approaching 50% of purchasers would complain that the lamps didn't work!!

Kind Regards, John
 
Well done, JohnW happy new year. I assume your drawings in turn, also explain how they run on DC even with the Alternating cycle of an ac supply, Just going from the top drawing to the bottom drawing and repeating again and again so many times a second
Exactly - that's why the same lamp can work on AC or (either polarity of) DC ....

... and a very Happy New Year to you, too!

Kind Regards, John
 
I'm not sure what you mean by "240V GU10 base ones".

Twas just a little dig at winston, I agree 240 volt Dc would be rare.
Most GU 10 type LED lamps incorporate a rectifier so they will work off AC or DC.

I will try and find a pic of the polarised ones, I think they were theatre bulbs and quite dear, i only asume the lampholder leads are possibly colour coded.
Wf was recently, stocking G5.3 holders with Brown and Blue leads, which did not seem right to me, though there are 240 lamps on ebay as we found.
 
Twas just a little dig at winston, I agree 240 volt Dc would be rare.
Yes, I realised that - but, if one could find a 240V DC supply, it's not impossible that they would work (at least with one supply polarity)
I will try and find a pic of the polarised ones, I think they were theatre bulbs and quite dear, i only asume the lampholder leads are possibly colour coded.
I suppose it might be OK in specialised areas. However, as I implied, I think the manufacturers would probably have more sense than to sell polarity-sensitive lamps with non-polarised bases (even if polarity was 'marked') for consumer products, since they would otherwise undoubtedly be driven mad by all the complaints about non-functioning lamps!!

Kind Regards, John
 
the ac transformer was rated at 30 - 60va which was ok for the 12v 35w halogen lamps but when the 12v 5w LED lamp was fitted, if your'e lucky they may stay lit otherwise in my case they started flashng after approx 50 mins.
So in the end it was easier and cheaper in the long run to dump the transformers/drivers and fit new lamp holders for 230v LED's.

So, once again, we have a switch mode power supply (not a transformer, transformers don't have minimum ratings like that) designed for halogen lamps. Earlier in this thread I said these don't work with LEDs.
 
So, once again, we have a switch mode power supply (not a transformer, transformers don't have minimum ratings like that) designed for halogen lamps. Earlier in this thread I said these don't work with LEDs.
In the example you're responding to, the problem with the LED was not necessarily anything to do with the type of power source, or what it was 'designed for' - but trying to run a 5W load from a source said to require a minimum load of 30 VA (or maybe Watts) is obviously "pushing one's luck" in quite a big way.

As has been discussed, it could be that a particular ELV LED lamp would not be happy with the high frequency output of a SMPSU, but that's not inevitably the case for all such lamps. A SMPSU with no minimum load, or a minimum less than that of the LED might well work satisfactorily for at least some LED lamps, despite the frequency.

Kind Regards, John
 
Some power supplies and or LED drivers designed for 230 volt AC will NOT work on a DC supply as they use a capacitor in series with the mains input as a current limiter / voltage dropper.

And the LED is a diode controlling the current flow direction (one way valve).

It is a diode but as a one way "valve" it is very weak and can break when even a low reverse polarity voltage is applied. The driver ( the device which controls the amount of current flowing through the LED element ) has to ensure that any reverse voltage is below the reverse break down voltage of the element. Some LED elements have a second diode built into the element that allows reverse polarity current to by pass the light emitting part of the element.

The LEDs used in low cost Christmas decorations have a form of "driver" built into the element. Either a semiconductor resistor or a constant current diode incorporated into the chip. This allows the LED to set its own current when connected directly to a battery of 3 or 4.5 volts. ( or some other low voltage source ). This more complex element is still cheap to produce and the inbuilt "driver" allows for very simple and very cheap assembly of long strings LED lamps connected in parallel to a low voltage supply.
 

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