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| Electronic 12V transformer for GU5.3 MR16 LED bulbs |
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| thexeno:
--- Quote from: Zero999 on September 07, 2019, 06:35:18 pm --- --- Quote from: thexeno on September 07, 2019, 05:24:59 pm ---Ok, I thought the same. Sorry, I should have put arrows in the picture. But then, seems to work without visible issues. Could be that might get damage over time? Now I have them for 3 months already... It does not seem to overheat, but I don't have a reference to be sure for that. My engineer side is telling me to make an age test and see if they survive on the 50Hz line over time --- End quote --- If they're working without any issues then leave them alone. They won't damage the transformer and if they stop working, they're easy to replace. --- End quote --- I was a bit worried that they might become a EM power transmitter in terms of EMI (the regulator working in different modes with 50Hz, or the like, wildly switching to keep track of the slow, high swing changing voltage). But I have no clue to qualitatively check that.... |
| Twoflower:
Also a normal halogen transformer is rated to 11.something Volt under the rated load. So if you replace the 50W bulb by 7W LED the voltage will be higher. And if you have multiple bulbs it get even worse. Depending on the transformer it can exceed the 12V. That's probably the reason of the short LED lifetime some people face. Switching PSUs shouldn't suffer this problem as they are regulated. By the way that is also the reason why it is a good idea to replace a burnt halogen bulb quickly if multiple bulbs are connected in parallel. The increased voltage will shorten the lifetime of the others. |
| Zero999:
I would have thought there would be less EMI when powered from 50Hz, than the 50kHz. It's generally recommended to keep cable runs as short as possible with electronic transformers, to minimise EMI. Quire often, each lamp will have its own transformer, so the cables can be very short. Conventional transformers are less of a problem: just make the cable thick enough, do the voltage drop isn't significant, with the maximum length being determined by the wire gauge which will fit in the terminals. If the LED lamps are properly designed, they should work over a reasonably wide voltage range, so the slightly higher voltage from a lightly loaded transformer won't be a problem. It should have a switched mode power supply, which will deliver the same current to the LED dies, over a reasonably wide supply voltage range. Electronic transformers aren't regulated either. They typically consist of a Royer oscillator driving a high frequency transformer, with no feedback. It's possible electronic transformers offer better regulation, than conventional transformers, because they have lower copper losses, but they also have additional losses in the rectifier and transistors. Regulation specifications for conventional transformers are easy to find, but I haven't found any for electronic transformers, so it's not possible to compare, unless one has the time and resources to do the experiments. Here's an SG application note on electronic transformers. https://www.st.com/content/ccc/resource/technical/document/application_note/e5/88/46/11/35/8c/4a/bf/CD00003902.pdf/files/CD00003902.pdf/jcr:content/translations/en.CD00003902.pdf It's actually more difficult to design an LED lamp to be compatible with an electronic transformer, compared to a conventional one. Electronic transformers typically require a minimum load current, which is much greater than an LED lamp, so various tricks need to be employed to make it work. This is why I'm surprised this LED is recommended for use with electronic transformers only. Here's a brief presentation I've found on designing LED lamps to work off electronic transformers. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&cad=rja&uact=8&ved=2ahUKEwiG5-fHmNHkAhXUasAKHcnGC44QFjAKegQIAhAC&url=http%3A%2F%2Fwww.deyisupport.com%2Fcfs-file.ashx%2F__key%2Fcommunityserver-discussions-components-files%2F24%2F7711.Transformer-application.pdf&usg=AOvVaw1O71tqHvjAr0ZlgfiOK-9n I suspect people have problems with short LED lifetimes because they have bought cheap, crappy LEDs. It may be even more of a problem if they're run off an electronic transformer, as the slow rectifier diodes in cheap LED designed for 50Hz, will get much hotter at 50kHz, assuming they use enough to fulfil the minimum load requirement of the transformer, so it actually works. |
| thexeno:
As additional thought on my original post, I read this AN022, paragraph 8. Which makes me think that my LED lamp was showing the capability to work with electronic transformer, while some other LED lamps do not. AFAIK, the conventional toroidal transformer should always work. If the assumption is correct, this makes the LED lamp an higher quality than other LEDs ones, not a worse one as initially thought. Despite the package documentation might not be at the same quality level, as I am still making assumptions. But I thought it could be an interesting read. |
| Zero999:
--- Quote from: thexeno on December 16, 2019, 02:15:44 pm ---As additional thought on my original post, I read this AN022, paragraph 8. Which makes me think that my LED lamp was showing the capability to work with electronic transformer, while some other LED lamps do not. AFAIK, the conventional toroidal transformer should always work. If the assumption is correct, this makes the LED lamp an higher quality than other LEDs ones, not a worse one as initially thought. Despite the package documentation might not be at the same quality level, as I am still making assumptions. But I thought it could be an interesting read. --- End quote --- I agree, it should have no problems working off an ordinary iron core transformer. I suspect it will also work of a wide range of AC or DC voltage. |
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