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.
Flickering with TRIAC Dimmer & Why Trailing-edge Phase Cut Dimmer for LED Dimming?Background of Incandescent (TRIAC) Dimmers
When people say about “Dimmers”, they usually refer to the Wall Dimmers that are used for Incandescent Light. Indeed, these Incandescent Light Dimmers have many names, such as “Standard Dimmers”, “Wall Dimmers” etc. and represent a big product catalog from manufacturers all over the world. These Incandescent Light Dimmers have been existing in the market for over many decades, long before the invention of High Power LED Lighting. They will remain in the market for another long period of time.
- In our discussion, when we say “ LED Dimmer”, we 'd refer to “Special Designed Wall Dimmers for LED Lighting”.
Common to all these Incandescent Light Dimmers is the TRIAC IC inside. The most fundamental TRIAC dimmer circuit has only 4 major components and it is operated based on Phase Cut technology. (Below Right) A Typical On-Cord Dimmer only has 4 components, including the TRIAC IC. We know how an AC sine-wave from the outlet is like. Phase Cut technology is really about chopping the AC sine-wave in proportion to the amount of dimming desired: The Deeper the Dimming to be, the More of the sine-wave to be Chopped. Naturally, there are Two Ways of Chopping the sine-wave, Leading-edge is to cut the sine-wave when the line begins to rise and the Trailing-edge is to cut the sine-wave when the line begins to drop to zero voltage.
- See our Technology Section / Overview of LED Dimming Technology for the actual waveform. We also suggest interested parties to browse other sections of this website for more technical details.
Incandescent (TRIAC) Dimmers Not for LED Dimming?
TRIAC dimmers are designed for Incandescent and Halogen bulbs, using them for LED dimming have proven to be problematic as experienced by many installers. But TRIAC dimmers are still commonly seen in Major Furniture Franchise for Dimmable LED Lights demonstration. It may look fine in the shop, but for Lighting Professionals and anyone with installation experience, such “Demo-Only” approach would introduce Project Nightmares when such Dimmers are used after a period of time.
Leading-edge Phase Cut Introduces Electrical Stress for LED Lighting!
TRIAC IC's are very common in Electronics Design and they operate based on Leading-edge Phase Cut methodology. This is one of the two fundamental reasons why we say Leading-edge Phase-Cut is not good for LED lighting or LED dimming. Phase Cut dimming methodology is simple to understand. But in reality, when the sine-wave is chopped by the Leading-edge, due to the capacitive loading nature of LED lighting, there are Repetitive Current Spikes generated, which cause Continuous Electrical Stress to the TRIAC IC.
Note the Repetitive Current Spikes are not equal to the Inrush Current. Repetitive Current Spikes would occur every time the line voltage is altered from positive to the negative side and vice versa. On a 50Hz line, 100 Current Spikes can be expected per second and it will be present as long as the light is on. This is one of the reasons why the TRIAC Dimmers seem to work in the Retail shop or when in the Project Evaluation stage but failed in Practice. This is the exact reason why people are frustrated with Phase-Cut dimming! Their bad experiences lead some people even to wrongly conclude that Phase Cut dimming does not work with LED Lights!
In this video, we first demonstrated dimming effects with two Incandescent Wall Dimmers and both of them looked fine in the beginning. However, as we replaced some of the LED Lighting Fixtures, those dimmers no longer worked properly and massive flickering or lights became unstable immediately after.
Minimum Holding Current of TRIAC IC Introduces Unreliable Dimming Effect
In the 2nd half of the video, we found the same TRIAC dimmers showing Flickering when an LED Strip Light was connected and further Flickering after connected back to the previous downlight that was okay before. We then touched on the Holding Current of TRIAC IC’s, which is the other fundamental reason why we say Incandescent Light Dimmers are not suggested to be used with LED Dimming.
Towards the end of the video, we highlighted the conditions in order for TRIAC dimmers to work with LED Dimming, which is subject to 2 parameters. However, both are not unknown in practice and should not be relied on in any Lighting Design.
- Minimum-Holding-Current of the particular TRIAC IC inside TRIAC Dimmer (Unknown in Product Level)
- How much Current is drawn by the LED Driver(s) when dimming at Very Low Brightness Levels (Unknown in Product Level)
If the current drawn by the LED Dimmable Drivers always exceeds the Minimum-Holding-Current during the whole dimming operation, then in principle, the TRIAC dimmer would appear to be working normally. Since Incandescent and Halogen bulbs consume a much higher current than LED bulbs, TRIAC dimmers would appear to work fine in traditional lighting. But the same is not true for LEDs.
- Note as dimmer and driver work hand-in-hand, Deep Dimming effect can only be realized if both the Dimmer and Driver support the same level of performance. And we’d prefer this to as “Deep Dimming Compatibility” to distinguish the Generic "LED Dimmable" products.
Recently, we came across an F&B restaurant that had installed with 20x TRIAC Dimmers with all the Lights in the restaurant and called us for help as the lights become unstable shortly after. The restaurant could not open for business as a result of this and the timeline was tight! Both the Restaurant Owner and Lighting Suppliers became really stressed when several rounds of replacement of Wall Dimmers of different brands failed.
Appropriate Approach for LED Dimming: Digital LED Phase Dimmer
In fact, it’s very common for the Lighting Designer, Interior Designer, Electrician or End-Users, run into a scenario like this. Unfortunately, there is little demonstration and information in the market attempting to explain the reason behind. Our Digital LED Phase Dimmers (DZ3G340DIAL, DZ4G450MULT and more) are specially designed for LED Deep Dimming and deliver other Benefits from Digital Processing that the TRIAC Dimmers cannot. For other product benefits, please browse other videos or our Product page for details.