Dimming LED Lamps

Solid-state lighting (SSL) differs from conventional lighting because it uses light-emitting diodes (LEDs) rather than filaments, plasma, or fumes. Although still reasonably early in its development, SSL became competitive in several markets and it is broadening into other people due to the fact technology continues to enhance. However in the process, it is encountering several important issues that need to be dealt with, certainly one of which is dimming.

Lots of people consider SSL to be completely dimmable, an expectation that gets strengthened to different degrees by maker statements. The theory is that, LEDs can be and completely dimmable, because — unlike other types of light resources — there’s absolutely nothing built-in in their makeup products that could hinder the dimming process. Furthermore, LEDs typically preserve their effectiveness whenever they’re dimmed, and on occasion even increase it — whereas incandescent sources come to be less efficacious when dimmed.

Acting up in place of dimming down

However, as we all know, principle doesn’t always hold up around when you look at the real-world — where in actuality the plastic satisfies the trail. Whenever installed, the particular dimming behavior of several Light-emitting Diode lighting effects services and products (their reputation notwithstanding) will leave a lot to be desired. While dimming performance differs dramatically across various types of commercially offered Light-emitting Diode sources, less-than-ideal behavior turns up most frequently whenever integral LED replacement lights are set up on circuits controlled by phase-cut dimmers.

This misbehavior runs the gamut of quirkiness. Some products won’t dim after all — a restriction that could or may not be clearly revealed on product packaging. Other people may exhibit what’s generally “dropout, ” where they just dim area of the way-down to zero light result — state, to 60% of maximum — in place of entirely from 100percent down to 1% or below, just how incandescent lamps do. Nevertheless others may dim in an abrupt or “staircase” fashion, rather than dimming effortlessly and constantly because so many of us are used to. In the worst situation, users can experience the exasperating occurrence called “dead travel” — where dimming slider or knob moves a particular distance with no apparent improvement in light result anyway.

And that’s perhaps not the termination of the feasible shenanigans. Some Light-emitting Diode lighting items may also show a “pop-on” event, wherein a light source that’s been switched off in a dimmed state doesn’t “remember” the dimmed setting. Alternatively, it in the beginning reverts to complete light output when it’s turned-back on or, worse yet, requires the consumer to improve the dimmer setting above some threshold prior to the light will “pop on.”

Then there are the distracting noises that can come with the dimming of LED light resources, and undoubtedly the perceptible flicker that may in addition happen. Even simplest function a lighting control executes — turning the source of light off and on — is not immune to unwanted effects. Whenever some LED light resources are put within the “off” state by some phase-cut dimmers, they could display many different unforeseen and unwelcome behaviors, including: “flashing, ” where light source flashes repetitively; “ghosting, ” if the unwelcome light is faint but steady; or even “popcorning, ” where different lights regarding the dimmed circuit flash randomly and asynchronously.

Surprisingly, there is technique behind the seemingly arbitrary insanity of those numerous dimming issues. Ghosting, like, does occur primarily with additional advanced phase-cut dimmers, where extra functions include microprocessors or other energy-consuming elements that require a little but regular supply of current streaming through the light source, even if the lamp is off. While that small amount of present is not enough to make a filament shine, it could “fool” some LED lights into emitting light — an unwanted result that is notably less expected to occur with dimmers which have a neutral third cable rather than just two real time cables.

A question of compatibility

Each one of these dimming issues may be disconcerting, to say the least. Nevertheless, it’s important to keep in mind that they’re perhaps not caused by any shortcomings of SSL technology. Instead, they’re due to the fact that almost all of the existing dimmers inside nation were created for another kind of illumination versus for LEDs. This is certainly, almost the whole installed base of old-fashioned line-voltage (phase-cut) dimming controls was made for incandescent light sources (Figure). Therein lies the wipe — there could be compatibility problems between these controls and an LED light source’s “driver, ” which converts AC power to low-voltage DC power and maintains a consistent present inside LEDs to keep them emitting a steady amount of light.