The following topics are formulated base on our customer interactions, which represent some of the most concerned topics related to LED Dimming. The info should be read with our product brochure & demo video clips.
LEDs (Light Emitting Diodes) are semiconductor devices to convert electricity to light and are inherently dimmable. As LED technology (light source) continues to advance, more lumen output can be achieved with even less input power. Compared to Traditional Lighting, LED lighting is more complicated in terms of supply chain and has more electronics involved. Thus, LED dimming becomes a practical needs as the LED technology continues to evolve.
It's now more common to find a dimmer control in LED lighting than a few years back. Since there are many types of LED dimming technologies (both Wired and Wireless), it’s good to have a basic understanding of different types of LED dimming in order to understand the difference between AC Phase Dimming or Mains Responsive Dimming and other approaches. (Below) Typical AC Output Waveform of a TRIAC Dimmer. It's easy to see that's not the familiar sine-wave waveform.
The easiest way to recognize AC Phase Dimming is by looking at how the LED drivers are connected to the Dimmers (or the Control Units like a PC). For DIMEZE™ type of AC Phase Dimmer, it only has 2-wires for connection: One for connecting to the AC Live wire and the other for providing dimmed Live connection to the Live input of subsequent LED Driver(s). The Neutral wires of the LED Drivers are commonly connected together for a return to the Main Circuit Board. As both terminals of Phase Dimmers are connected to the Live Wire, some Electricians say this type of connection as “Live-In / Live-Out”. Note we do not distinguish polarity during wiring for our phase dimmers.
An AC Phase Dimmer controls the Live input and manipulates the actual input power / input voltage into the LED Drivers in the form of a Chopped Sine-Wave, preferably in the Trailing-Edge phase-cutting format for LED lighting. The Phase Dimmable LED Driver(s) then adjust the light intensity level and regulate the LED driving current accordingly. How accurate can the LED Driver adjust and stability to regulate the driving current are the key performance indicators of the LED Drivers. How deep can the LED Drivers dim is what we describe as Deep Dimming Compatibility. Thus, AC Phase Dimmers operate at Line Voltage (110 / 220Vac).
Although the remarkable difference in their waveforms, when measured at the DC output of the LED Driver, the chopped sine wave has no impact on the DC at maximum brightness level. (Below left) The DC output measurement (35.31V) at LED driver when no phase dimmer is connected. (Below right) DC output measurement (35.28V) at LED driver when a phase-cut (TRIAC) dimmer is connected, basically no difference.
What's the Difference Between Dimmable and Non-Dimmable Lamps?
In a nutshell, Dimmable LED lamps are capable of handling the input power reduction (as dimmer dims) and steadily reduce the LED driving current to produce the dimming effect. However, non-dimmable LED lamps CANNOT. Thus, dimmable LED lamps can be used in the On / Off (non-dimmable) circuit, but the reverse is usually not true. When the line voltage drops below a certain level, it appears to be a power failure to a non-dimmable lamp, which will be switched off suddenly.
What's the Requirement for Dimmable Fixture?
To achieve LED dimming, the LED bulb itself or the driver (power supply) must support dimming function. In other words, replacing the LED driver with a dimmable LED driver would make a non-dimmable LED lamp become a dimmable version. See our video for implementing a dimmable function with a malfunction LED lamp.
What Happen if I use a Dimmer to Dim a Non-Dimmable LED Lamp?
“Can the dimmer also dim non-dimmable LED lamps?” From our experience, grudgingly using a dimmer on non-dimmable LED lamps may somewhat reduce the brightness level. But eventually, the lamps would misbehave (flickering or even popping up at low frequency) and switch-off.
What's "Depth" in LED Dimming?
Compared to Incandescent & Fluorescent lamps, the flickering issue with LED is much more noticeable because LEDs exhibit very fast luminous response to minor fluctuations of the LED driving current. Thus, the Dimming Range (Depth) of Dimmable LED driver is always the first consideration for LED dimming.
What Do They Mean by a "Flicker-free" LED Driver?
“Flicker-free” LED drivers refer to dimmable drivers that are designed for driving the LEDs at low brightness level. Then, the next question is how "low" is low? In practice, very often an LED dimmer controls more than a single lamp or more than one types of lighting fixtures, which means that it's likely the dimmable equipment from multiple manufacturers (individual devices in the system) may not support the same level of dimming range. Unfortunately, this is only found when all the lamps are connected together or in the field installation stage. In cases like this, it's recommended to deploy DIMEZE™’s MIN-LEVEL-SET feature to fix an acceptable System Dimming Range to achieve flicker-free LED dimming. See how Minimum-Level-Set works here.
What's a Phase Dimmable LED Driver?
A phase dimmable LED driver from the market has an unknown dimming performance; Phase dimmable LED drivers are also commonly known as "TRIAC dimmable LED drivers". However, as we point out that although TRIAC dimmers operate by phase-cut technology, they are not suitable for reliable LED dimming. See comparison video to illustrate the difference between TRIAC and Digital LED dimmer.
What Should We Expect for LED Dimming?
Since there is not yet a ready market standard for dimming performance, any product with its brightness level adjustable can be termed as “Dimmable” product. In order to set an expectation on LED dimming effect, we utilize the information from the IESNA Lighting Handbook 9th Ed.:
“At low levels, the human eye would enlarge the pupil to allow more light to enter the eye. This mechanism creates a difference between the measured light (by light meter) and the perceived light (by the human eye). A lamp that is dimmed to 20% of its maximum measured light output is perceived as being dimmed to only 45%.”
For our discussion, we shall refer 20% or below of the maximum measured light to as “Deep Dimming”! Read on
How About the LED Dimmer?
For AC mains powered LED dimmable lighting, the dimmer manipulates the AC waveform and controls the phase dimmable LED driver(s). Thus, the dimmer stability directly affects the whole LED driver operation.
Same Lamp, Different Dimmers! Very Different Results!!
| So far, we've mentioned that an LED driver is critical to LED dimming performance. In the following example, we choose to use the same dimmable lamp (i.e. exact same LED driver) to illustrate the significance of an LED dimmer. Using the same Tune-able downlight with different dimmers (Philips SED-200A vs. DIMEZE™ DZ2G450DIAL), two very different dimming performance is captured to the right.
The right photo shows the lowest dimming level by SED-200A, while the immediate left photo shows Deep Dimming performance achieved by DIMEZE™ Digital LED Phase Dimmer. This example of achieving two very different dimming performance with the same LED driver (the same LED Lamp) shows that dimmer is another critical factor for LED Deep Dimming performance.
See the comparison video to understand difference between Deep Dimming and. “Dimmable” Effect with the same Downlight
What's a Phase-Cut Dimmer?
Phase-Cut dimmer blocks the input line for a portion of the line cycle, which inhibits the average energy transferred to the lamp load and hence, the output brightness. Both TRIAC dimmer and DIMEZE™ LED dimmers operate by phase-cut dimming principle. However, they are very different in design.
TRIAC dimmers operate on leading (forward) phase-cutting methodology, while DIMEZE™ Digital dimmers are known as “Universal Dimmers” because it has the option to support both leading and trailing (reverse) phase-cutting methodology. Designed for Incandescent and Halogen bulbs, when used with LED Lighting, TRIAC dimmers are usually associated with the following problems:
See how TRIAC dimmers are different from Digital LED dimmers here
Sometimes even with a great lighting design, designers should realize that in the local market, most of the retrofitting scenario only has the Live- wire for the dimmer switch to connect and the Neutral wire is shared or connected to the lamps next rooms. Thus, if the designer selects a dimmer that requires individual Neutral wire connection would be problematic in field installation or the design just can’t be implemented.
The schematics of our Evaluation kit shows "Single-Live and Common-Neutral" connection or “Live-in, Live-out”, also known as “Hot, Dimmed Hot” in the US. Our EV kit is great for mock-up or field evaluation; for interested customers, please contact us for our evaluation kit or samples for evaluation. Contact Us
Interaction Between LED Dimmer and LED Driver
In conclusion, how should we understand the role of Dimmer and Driver in LED Dimming? First, we must remember dimmer and driver always work hand-in-hand. The first condition for LED dimming is obviously the driver, since if the driver is not dimmable, the LED lamp won’t dim; if the dimmable driver design is not good, the dimming performance would be prompt to problems.
From LED dimmers point-of-view, a quality dimmer only reflects (not changes, nor improves) the driving capability of the LED driver at low brightness level. As a system controller, the dimmer determines how low can the LED driver dim; there are cases when a LED driver has a "buck-boost topology" design in such a ways that regardless of any further line voltage drop, the driver raises its internal voltage and keep it at a certain minimum level (from the lamp perspective, the brightness level would not be able to dim anymore).
For deep dimming, a key dimmer performance indicator is the Minimum-Load-Required by the dimmer itself. As LEDs are very sensitive to the changes of the driving current from the driver, which ultimately is powered through the dimmer, very stable system performance by both the dimmer and the driver at low brightness level (when the current is already very small) is the key to project success.
“Deep Dimming Compatibility” shall be the real target to look for in practical applications. When we refer to “Deep Dimmable Compatibility”, we refer to the following:
• “Quality Dimmer” + “Quality Dimmable Driver” = “Deep Dimming Performance”
• “Quality Dimmer” + “Poor Quality Dimmable Driver” = “Poor Dimming Performance”
While there are numerous LED driver manufacturers in the market, we're glad to recommend Meanwell PCD series (AC Phase-Cut Dimming) to work with DIMEZE™ Digital Phase LED Dimmers. See our product video here. To further illustrate that different "dimmable LED drivers" perform differently, please see this comparison video between Meanwell and HEP TRIAC Dimmable LED Drivers for more ideas.
To choose the right dimmer device, it’s necessary to understand correctly the MAX and MIN loading requirement of the device in order to ensure product safety and to have consistent performance as the number of lamps increase or decreases during installation.
In practice, it's common that electrician or end-users would find a LED dimmer burnt-out after used for a while. One of the reasons for such failure is due to LED dimmer overload, which usually means too many LED drivers are connected together to the same dimmer. While the 450W power rating for the DIMEZE™ LED dimmers sounds like "too much" for the average LED bulbs or a downlight that consumes less than 20W, we should remember about power de-rating for the devices in installation. Instead of finding out how many LED drivers can be connected by trial-and-error, we should consider the Inrush Current parameter of the LED drivers.
[Above / Data extracted from Meanwell Product Marketing materials on PCD series, which is an AC phase-cut dimmable LED driver series; Meanwell website: www.meanwell.com]
The maximum inrush current that the DZ1G450CAPS can handle is 35A, which seems to be a big number. However, when we look up the maximum inrush current for the LED drivers, you may find the number can be as high as 10A or more (e.g. Meanwell PCD-16-xxxB series has a 10A figure for the max inrush current). If we use this number for a rough estimation, that means we may only connect 2 to 3 units of PCD-16-xxxB to a single DZ1G450CAPS. In terms of power rating, this would mean around 3x 16W or 48W vs. the 450W of the DZ1G450CAPS.
However, for best practice, electricians are recommended to reduce the numbers of LED drivers connected to the dimmer and use a bigger power rating driver instead. In our example, using 3x PCD-16-300B (48W) would result a Maximum-Inrush-Current as high as 30A; on the other hand, for similar power range, if we only use a single PCD-40-xxxB (40W) or PCD-60-xxxB (60W), the actual maximum inrush current stress posted onto the LED dimmer would be largely reduced to 11A or 13A respectively! Thus, from minimizing the Maximum-Inrush-Current point-of-view, our suggestion is to "Always reduce the number of LED drivers connected to the LED dimmer and select a single LED driver with suitable power rating (include proper de-rating) if possible".
Back to the scenario at the beginning, when electricians found the LED dimmers burnt-out, one of the suggestions is to split the lighting circuit and install more LED dimmers. But in reality, sometimes it is not an easy option to implement a new set of wiring for additional dimmer switches. Alternatively, electricians may review and design the overall system configuration to reduce the number of LED drivers and or both replace the LED dimmer with a higher power rating. Choosing high power rating modular switches that fit into a single wall plate can make the re-wiring much easier and save making a new hole in the wall and is a good alternative to explore!
Before choosing the LED driver from a supplier product catalog, the 1st step is always to understand the lighting equipment itself. The most obvious question is “Does it require an External LED Driver?”
Products with Integral Drivers
Typical LED retrofit application (popular lamp base for screw-in: E27, E14, A19, GU10, MR16 etc.) all have integral LED driver ICs that provide the necessary constant current for the LEDs inside the lamp; the dimming performance and the compatibility with the dimming control device / dimmer of such types of products would be determined by the capability of the integral LED driver (driver IC) inside. While it’s more common to have integrated LED drivers to the lighting equipment now, the Electricians or End-Users should remember that products to be directly driven from the AC mains must pass proper Safety Regulation (Critical Factors: EMI/EMC, Efficiency % (ƞ), Power Factor etc.) and must be provided with proper Heat Dissipation to avoid overheating during operation. Additional consideration on Years of Warranty and International Protection Ratings (IPxx) should also be checked. See the actual dimming performance of popular off-the-shelf retrofit lamps here or dimmable LED filament bulbs here.
Using high CRI and dimmable LED MR16 (aka GU5.3) bulbs for Halogen replacement is a good energy saving practice (besides the electrical power saving, ignited Halogen bulbs are very hot!). As it is supposedly a straightforward replacement, Electricians seldom pay attention to the 12Vac transformers that are required to be connected to the wall dimmer and the MR16 bulbs. Note the dimming function is realized by the wall (phase) dimmer and the dimmable LED MR16 bulbs; the function of a 12Vac transformer merely provides a stable power source for the light bulbs. First-thing-first, the electrician should always double-check if that’s a dimmable LED MR16 bulb being installed; of course, it would be difficult to understand about the product's dimming performance from the product package.
DC 1-10V dimming is a common approach in a large area or high power consumption requirement LED strip light dimming application. Today’s market norm for LED strip application is to have around 14.4W/Meter and it’s common to have 10 meters long LED strip for the various indirect lighting purpose. Therefore, the power consumption required for the LED strip alone may easily be in the range of 150W - 800W per driver or 3000W+ for a large indoor area. Assuming only 80 lumen per watt, that's equivalent to 240000 lumen for the indoor area! Hence, dimming becomes a real energy saving practice to save the huge amount of energy consumption on indirect lighting.
Each Constant Current LED driver has a specific Output Voltage (VOUT) range for the rated Constant Current output. For Non-Dimming applications, matching a LED Driver with a lighting fixture is mostly about selecting a LED driver that has the VOUT range to cover the Forward Voltage Required to support the Target Constant Current Output operation (VF @ Rated IF). Note that during the Dimming operation, the Phase Dimmable driver output current and output voltage will both be reduced continuously.
Since LEDs from different LED chip suppliers have different I/V characteristic, some LED chips would have a wide Forward Voltage (VF) range. Therefore, it’s likely that during the dimming operation with some LEDs, the driver VOUT will be dropped outside its specified Constant Current Output Voltage range (VOUT,MIN).
To achieve Deep Dimming effect, detail understanding of both the Dimmable LED Driver Output and the LED Forward Voltage Ranges would be required, which makes Dimmable Driver selection little more complicated than that for Non-Dimmable Driver. As we try to show in our "LED Dimmable Driver Selection" Application Notes (see the bottom of this section), it would be wise to make proper measurements of an unfamiliar LED lighting fixture before matching it with the right LED dimmable driver.
While Two-Way Dimming is a common requirement in Lighting Application, having more than one dimmer in the line is forbidden in the traditional wiring approach. As a result, the implementation based on single pole dimmers would only allow dimming at a single location. Therefore, the resultant connection is actually a Two-way Switching-plus-One-Way Dimming, similarly for the Three-Way setup.
As lighting control technology evolves, one way of solving this is to use Smart Dimmers. With Smart Dimmers, more than one dimmers can be connected wirelessly and paired to control the same light. However, as the Smart Dimmers must have its own electricity supply at all times, it’s common to see that such dimmers would require a Neutral Wire in order to be functional. Again, this may not suit for the Retrofit installation, where no Neutral Wire is available.
Another approach to solving the unfulfilled market demand of True Two-Way Dimming is to develop an Upgraded Single Pole Dimmer that allows inter-communication among the dimmers, which in turn makes Two-Way Dimming-plus-Two-Way Switching operation possible. This is the target application of our Digital Multi-Way LED Phase Dimmers, DZ4G450MULT.
While our dimmer can be used independently, more than one dimmers can be connected together to form a proprietary network that controls the same lights from multiple locations, as if only a single dimmer was installed.
Unlike our previous offers, our DZ4G450MULT has three terminals: Terminal 1 for LIVE, Terminal 2 for DATA & Terminal 3 for DIMMED LIVE. When in Multi-Way operation, the MASTER unit is the one that connects to the light load and the rest of the units in the loop are the INTERFACE units that only have the LIVE (Terminal 1) and DATA (Terminal 2) connected back to the MASTER unit.
When more than one INTERFACE units are present, all the units should be connected to the DATA port of the MASTER unit. In other words, for the DATA port connection among the MASTER and INTERFACE units, it would be a PARALLEL connection for all the units in the loop. For convenient wiring, each DZ4G450MULT can be connected to the MASTER unit that is nearest to the lighting connection.
See Product Video here.