Besides energy saving, controllability is the next highly expected feature of LED Lighting over Traditional Lighting. However, such a control aspect seems to be missing in daily applications. Since 2015, we've been developing & marketing Phase Dimmers* and related products to address LED dimming control

Driven by our project field experience, we developed a new type of Tunable White control using Phase Dimming & 0-10V technologies, which gives our Tunable White Controller (DZ1G300TUNE) & Dynamic Lighting Controllers (DZ2G300TUNE_TOGG / _PUSH). It's our goal to lower the technical and costs barriers for different Circadian Lighting or Commercial applications that desire Multi-Purpose Lighting.

* Our 450W / 220-240Vac Single Live-wire Operational Trailing-edge LED Phase Dimmers released to market includes DZ2G450DIAL & DZ1G450CAPS (2015), DZ3G450DIAL (2017), DZ4G450MULT (2018). In 2017, our DZ3G450DIAL was listed as a SORAA® Compatible dimmer. In Q2 2021, an Enhanced version of DZ3G450DIAL has been available.

In this Application Video Library, we shared a number of interesting topics on LED dimming or how our products can be applied in different scenarios.

Dimmable LED MR16 with 12V Electronic Transformer Backward Compatibility (ELV)

Although both the magnetic low voltage (MLV) and electronic low voltage (ELV) transformers produce 12Vac to the LED MR16 bulbs, they operate by completely different principles, which leads to their obvious difference in size and weight. The MLV transformers only couple the line voltage to the step-down 12Vac waveform. On the other hand, the ELV transformers are originally designed for Low Voltage Halogen lighting and contain self-oscillating circuit, which requires the resistive Tungsten Halogen bulb to maintain the stability for the internal circuitry. To support LED lighting adoption, the new generation of ELV transformers, so-called “LED Compatible” already have lowered the minimum power requirement to support the lower power consumption LED lighting, but the fundamental principle remains.

In this video, we continue to use the same two LED MR16 bulbs, a local brand, and a Philips MASTER, that we dimmed with an MLV transformer in the previous video to explore their performance using different commonly available 12V electronic transformers ( Philips ETE-60 and OSRAM ET-LED 30 ).  The contrast between the two LED bulbs is a perfect illustration of the Backward-Compatibility Issue: The local brand ceases to function properly once changed to the two common electronic transformers, while the Philips MASTER continues with consistent dimming performance with either ELV transformer. If a poor backward LED MR16 bulb is connected, the electronic transformer would not function properly and fail to provide stable 12V to the MR16 LED bulbs. This results in the shimmer at high brightness or for the whole operation range, which is different than the flickering observed at low brightness level. However, a good backward compatibility LED MR16 bulbs can work consistently with different electronic transformers and provide the predictable result.

In fact, the backward compatibility issue is heavily related to the LED driver IC inside the bulb. Ironically, in order to keep the 12V electronic transformer working properly, the more advanced LED driver ICs simulate the current consumption behavior of the Halogen bulbs for the LED MR16 bulbs. This explains why the situation seems to be improved when a poor backward compatibility LED MR16 bulb is connected with more LED bulbs together to the same electronic transformer. This leads to the point that the backward compatibility issue is also subject to the number of LED bulbs connected. We added that from our experience, the wide input range, 12Vac/12Vdc vs. 12Vac, introduces further complexity for backward compatibility.

Since in retrofit cases, we don’t want to change the already installed 12V transformers for the LED MR16 bulbs, we hope the video on the MLV and on this ELV transformer can help installers to identify the key issue quickly and deal with the problems effectively, in case they find mysterious flickering issue for a drop-in replacement scenario. For the LED MR16 retrofit application, our advice is to have the money spend on Good Backward Compatible LED MR16 bulbs instead of doing trial-and-errors with the many different 12V transformers. Before making a purchase, installers may also want to ask for supplier’s suggestion on the compatible electronic transformers and to be clear on the expected dimming performance prior to the installation to avoid argument after.

Although many resellers recommend TRIAC dimmers for dimmable LED MR16 bulbs, towards the end of the video, we mention that TRIAC dimmers should not be used for the LED MR16 bulbs due to the leading-edge phase-cut methodology, which would lead to shortening product lifespan over time. Thus, in order to realize the expected long product lifespan benefit, it’s necessary to use the appropriate Digital LED Dimmers!