12V LED bulb and "electronic" transformer

[pepin2pomme]

Hello,
A testimony and a question ...
I connected white LED bulbs to a 12V line supplied by a "normal" transformer (ie without electronics and relatively heavy). There were on the same line LED bulbs and incandescent bulbs. Everything worked without any problem.
When I later replaced the transformer with an electronic model (both more powerful and lighter), the incandescent bulbs continued to shine as before, but the LED bulbs all burned (they permanently went out at end of 20 to 30s) before I understand what is happening.
There are of course special LED transformers, but they are of low power, and can not feed a mixed line (with incandescent and LED bulbs). The manufacturer does not guarantee its bulbs (yet specified 12V) if they are not powered by a special transformer LED, I can not play the guarantee.
My questions are:
- What is the power supply difference between a "normal" transformer and an electronic transformer? (voltage seems to be the same, but what about frequency)
- Did you have the same experience?
- Are there LED MR16 12V bulbs able to replace incandescent bulbs, (which therefore support the electronic power supply)?

[elephant]

special led transformers probably have a current limitation. You probably slammed your leds.

[Did67]

Like you, I connected LEDs on a 12 V line fed by an antediluvian transformer (a big block dating from the 2000 years).

It's been going for a few weeks.

Note, the line is powered by a dimmer, I hesitated and I started. I always put the drive in full. No problem so.

But in the other direction, I do not know!

[Christophe]

Uh silly question before going into details: the new electronic transformer is it AC or DC and your LED bulbs were they AC and DC? And why did you change your transformer?

At home we have a 12V AC hybrid test luminaire (3 incandescent 20W + several types of MR16 AC / DC led bulbs) and it has been holding for 2 years without any worries. The transformer is iron type therefore old and heavy (type "long live magnetic pollution" )

Here are the bulbs that are on them: https://www.econologie.com/shop/ampoules-led-c-90

Here is an 12 V AC 60W electronic transformer with pseudo sinus hash:
https://www.econologie.com/shop/transfor ... p-311.html

And a real 12V power supply DC / DC 60W: https://www.econologie.com/shop/alimenta ... p-227.html

The 1st, which makes a pseudo sine signal, is not a "clean" AC signal and it can cause problems with the electronics. Their use is not recommended with led bulbs (some pass, others not).

The difference in price (and weight) gives an idea of ​​the difference in quality between 2. The 2ieme is adjustable (9 to 15V DC) too.

Attention also to the quality of LED bulbs, we find everything and anything on the market ...

ps: another subject on the subject https://www.econologie.com/forums/quel-trans ... t2719.html

[Leo Maximus]

The LEDs "go off" when they are boosted. Usually the internal impedance of an "electronic" transformer is much higher than that of a conventional transformer. Suddenly, if we replace the same number of 12 volts filament lamps by LEDS lamps then there is less current consumed and the output voltage is higher then the LEDs "fart". It is a simple application of Ohm's law.

Ideally, the LEDs should be powered under constant current or voltage. It is not complicated, b .....! But LEDs that piss it still suits the traders, right?

For a white LED under 3,4 volts we have about 20 mA, beyond there is danger. An LED can support a reverse voltage of the order of 4 to 5 maximum effective volts, so it can be made to work in AC to some extent.

Léo

[Christophe]

Not entirely agree: LEDs are probably more sensitive than halogens (which 15 16V have no problem) but a transformer is not supposed to rise too much voltage (especially ferric: if it gives 12.5V 230V AC, to go up to 15V AC must feed it in 276V which never happens except network problem or love at first sight) ...

As for the cleaving that is said arranges the sellers: there is the guarantee ... no?

[Alain G]

Good evening pepin2pomme!

Well the problem is not very complicated, your new power supply is a chopper without transformer, a lot of electronic device does not support this type of power supply, I cooked for about 150 euros fluorescent bulb outside only a dozen years ago by installing a triac timer instead of relays.

These pseudo power supplies work a bit like an inverter and generates a high frequency of small pulses that if the LED bulb is not designed for this type of power is self-destructive, which is surprising is that you coupled with glowing and it should not have destroyed your LEDs unless it worked independently.

Beware of these power supplies and read the instructions on the bulbs and the power supply.

[Forhorse]

Yeah, I'm pretty much of the same opinion. it must be the high frequencies at the output of this kind of "transformer" which has burnt your led lamps.
This kind of switching power supply works at frequencies close to 20Khz, given the simplicity of the trick, not sure that the output current is not simply at this frequency. And I do not think that a power supply intended to work under 50-60Hz supports frequencies far beyond.

[Forhorse]

I would add, to illustrate my hypothesis, an experience that happened to me a long time ago.
At the time I was riding a moped and, having tired of having my back light grilling, I decided to make a LED based: simple assembly a diode bridge, a condo, a voltage regulator and 4-5 leds in series and a resistance.
The magnetic flywheel of a moped produces alternating, whose frequency varies naturally according to the engine speed.

I plug my little assembly and start my moped. it works, impeccable I tell myself. I'm going a little bit, it's still working. I even more acceleration, suddenly it goes away. I release the accelerator, the engine speed goes down my taillight lights up again.
I experience it several times, each time same problem, yet I'm far from over-voltage, the headlight usually light up him ...
To have the heart net, I acclimatize thoroughly (but deep in the background, must say that my mob was a little trafficked ...) suddenly puff, little smoke in my rear light. I open, a diode of the rectifier had blown up.
I assumed she did not support the frequency. I then measured something like 8000Hz (if I remember correctly) in current frequency at the output of the magnetic flywheel when the engine is at full speed.

[Obamot]

...so what?

Little circuit idea to solve this type of problem?