Retrofit MR16 LED problems revealed!

Singapore, 6th October 2012

After nearly a year of frustrating testing and researching I can finally share my findings and conclusions on why we have problems with LED MR16 retrofit lamps. The most significant problem being flickering issues when dimming and unexplainable shortened life of some of the LED lamps. Despite all the flowery marketing talk about the long life and the dimming ability of the LED lamps, the fact is that all of us lighting designers face these problems continuously.

While I initially started my investigations together with the manufacturers, it was becoming clearer and clearer that manufacturers were not totally fort right in their assessments and kept diverting the attention away from the lamp/ transformer combination. With sales of these lamps reported to be in the millions per month understandable, but not helpful. So I sought help from a professional and independent specialist body, an ODM (Original Design and Manufacturing) plant in Penang Malaysia, who test, design, develop and manufacture LED lamps for many major brands in the world. Their independent findings and testing results have led me to finally being able to pinpoint the root cause of all our problems. Moreover I have come to the understanding that this problem is not manufacturer specific, but applicable to all brands, worldwide! No manufacturer to date seems to be able to master the issues surrounding the use a conventional transformer with a LED retrofit lamp without seriously affecting lamp life and lamp performance! Wow!

What was tested and measured were the current and voltage generated by the lamp (LED MR16 12V GU5.3) together with the transformer and what came out as a general result is that somehow the LED technology induces a “reaction” in the conventional transformer which in return creates continuous spikes and surges as output to the lamp. These spikes over time damage the electronics in the LED circuitry and lead to flickering and plain failing of the lamp. It appears that the stronger and longer the dimming action, the faster the deterioration of the LED lamp. This also explains why in newly installed installations the problems are not immediately apparent.

While probably ok in residential applications, it has become unacceptable in professional and commercial applications. The fact is that conventional transformers are designed for conventional technology and not for LED and vice versa! Conventional transformer and new LED technology therefore do not mix, it’s a bad marriage!

Light & Learn 3-19: Screen shots of a typical conventional transformer with surge spikes compared to what an LED lamp is designed to receive. Below that a typical schematic of the retrofit situation and one of the possible remedies taking the transformer (old non-LED technology) out of the equation.

06. October 2012 by Martin Klaasen
Categories: Education, Light & Learn, lighting applications | 8 comments

Comments (8)

  1. Heat dissipation,optical design and drivers are always key topics for LED. I am Judy from China, I am also a “light” girl,lol.

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  3. Inject a phantom mirror image voltage.
    Oh, maybe only I know how to do this.

  4. thanks for this, I’m glad to have finally have someone find out the issues and state them for us. What about replacing the existing transformer with a new LED driver, would this be a suitable alternative?

  5. As I understand the nomenclature…the MR16 is a DC device.
    The spikes can be filtered with a series inductor and shunt capacitor…preventing the failure of the emitter sites at the LED.

    One thing I am looking for is a schematic for the typical MR16 with the lower power leds. 1watt or 3 watts. I want to see about removing the input diode and see what else I can do to run it on lower voltage.

  6. I recently had a Diall LED GU5.3 12VAC/DC 1.5W catch fire here in Shanghai. I suspect lightning surge on the mains and through the transformer. The ceramic base had a big black hole burned into it.

  7. So a PAR bulb is made for 120V and an MR bulb is made for 12V. The removal of the transformer means that you need to change bulbs to get the wiring required for higher voltages at the “pins”. I would NOT rewire a MR fixture to do this. MR bulbs should only be used in un-dimmed circuits.

  8. In side all led retrofit mr16 12v lamps is a buck switmode regulator , and a full bridge rectifier. Connecting the lamps to ac iron core transformers with dimmers the switching spikes created by the dimmer damage the buck regulator inside the lamp. They first start to flicker and then fail. The LEDs are generally still ok but since the power supply is inside the lamp it cannot be repaired. The shitty light dimmers still create switching spikes even when at full. The diode bridge rectifier is also inside the mr16 lamp this allows the lamp to be pluged in either way into the mr16. Socket way can run from ac. The lamps don’t dim properly because of the buck regulator inside ramps up when voltage to lamp is reduced. Manufactures use buck regulators instead of a power resistor to improve effiency and to keep heat dissipation down. Heat destroys LEDs.

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