Variation of LED bulbs and LED overclocking

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Christophe
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Variation of LED bulbs and LED overclocking




by Christophe » 13/02/09, 11:13

I just made, a little by chance, some tests of variation of led bulbs by directly feeding multileds circuits with a variable supply of laboratory.

Well, contrary to what we often hear: the variation of LED lighting continuously is quite possible! It suffices to supply them with a variable DC voltage.

I did tests with warranty return (transformer HS) of:

Image

With this model, the board must be powered by 24V but it can go up to 30V and in this case the brightness and consumption increase in arrow (30W instead of 5W!)! I will soon make a demo video, with a luxmeter.

ps: I have already smoked some leds ... : Cheesy:
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by elephant » 13/02/09, 11:43

All is to see how the reduction of the 230V is to supply the led, but in principle, everything must be possible, variation of the alternating current, cutting by triac, as long as there is not a switching transformer to lower voltage.
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by Christophe » 13/02/09, 20:59

Yes, there I spoke in low voltage only: by directly feeding the leds (or with low voltage bulbs MR16)
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by Christophe » 16/02/09, 20:29

Here is an 1ere series of measurement: the variation of the luminous efficiency of a series of DC LEDs according to the power.

Test plate (1 led is HS):

Image
I measure:

a) input voltage
b) current input
c) lux output with a unidirectional luxmeter (ITC 777 of the photo)

I vary the voltage and the power input.

1) Curve of luminous efficiency according to the consumed power:

Image

We quickly reach a maximum to fall then, so stay low voltage for better performance!

In my case the peak is obtained at 3.4 V, which corresponds to about 0.5W

2) Evolution of the circuit resistance according to the voltage

Image

We get a completely different behavior (the opposite!) From that of the internal resistance of an incandescent bulb!
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Re: Variation of LED bulbs and LED overclocking




by paul_f5hpq » 17/04/20, 22:51

Nice experimentation!
I like to find methodical handymen!
The LEDs have a threshold voltage and a nominal current, beyond which the light produced increases, but in a lesser ratio.
When you reach a certain current, the LED heats up and loses efficiency, you have perfectly pinpointed these phenomena.
LEDs sometimes hold very strong impulse currents, but cannot dissipate too much power, hence the fact of having a strong light then "paf la LED" ...
If I remember my lessons, the threshold voltage of the junction decreases with heat, hence: it heats up> the threshold voltage drops> the current increases> the power too and it is thermal runaway (at the scale of a few milliwatts).
If you have the option on your diet, set a current limitation so that you can do all the tests possible without ever exceeding the fateful values.
Your feedback is very interesting, continue these sharing.
Thank you.
Pol
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