I just happened to find an interesting presentation on light dimming technologies and who they work with LED lighting. Dimming LED sources: what’s working and what still needs fixing is a worth to take a look if you are into LED lighting or light controlling applications. It is a very good overview of the current light dimming practices and how they would work with LED lighting. In some applications dimming is easy and there are many applications where dimming is not so easy.
45 Comments
Loko says:
Led bulbs is nice color cold white
Tomi Engdahl says:
Cree won’t compromise on dimming
http://www.edn.com/electronics-products/other/4422720/Cree-won-t-compromise-on-dimming
The LMH2 LED module from Cree delivers a natural dimming profile that previously could not be achieved in an energy-saving context. The dimming experience providing by the module is very similar to incandescent lighting, dimming smoothly form 2700K to 1800K, yet achieves more than 80% energy reduction over incandescent bulbs.
Providing white light and moving to a rich, warm light for restaurants, bars, homes, conference and reception halls and theaters, the one-module form factor addresses a broad range of lighting applications.
Tomi Engdahl says:
Over-driving LEDs for brightness
http://bryanduxbury.com/2013/12/02/over-driving-leds-for-brightness/
Most of the time when I’m driving an LED, I do it with a simple ballast resistor, and that’s all there is to it.
EDs have a rated forward current, but they also have a rated peak current, specified at a given pulse width and duty cycle. For instance, these red LEDs are rated for 30mA forward current and 185mA peak in 0.1 ms pulses at 10% duty cycle. Why is this stat useful? As long as you stick to the pulse width and duty cycle parameters, you can intermittently drive an LED at an excess current and get a brighter light without burning it out.
There is a risk in using this setup, though. If for some reason your PWM signal were to lock up in the “high” state, then the pulse width limitations would be exceeded and you’ll probably fry the LED in an instant. This means you need to be especially cautious during development – crashing your microcontroller at the wrong time can be costly!
I would say that the PWM-only LED is substantially dimmer, and the overdriven LED is almost but not quite as bright as the steady-on LED. This turned out to be exactly the sort of obvious difference I was looking for. It seems well worth adding the additional circuitry to get a much brighter display.
Tomi Engdahl says:
Non-Isolated Buck-Boost TRIAC Dimmable LED Driver
http://www.eeweb.com/company-blog/power_integrations/non-isolated-buck-boost-triac-dimmable-led-driver
This is a design example report of a 12 W, high power factor, non-isolated buck-boost, TRIAC dimmable LED driver employing LYTSwitch™-4 LYT4322E. The design is intended for A19 LED driver application. It operates in a wide input range of 190 VAC to 265 VAC and provides an output of 120 V at 100 mA.
The topology used is a single-stage non-isolated buck-boost that meets high power factor, constant current regulation, and dimming requirements for this design. This document contains the LED driver specification, schematic, PCB details, bill of materials, transformer documentation and typical performance characteristics.
Tomi Engdahl says:
A Primer on Buck (and Boost) Converters
http://hackaday.com/2015/01/24/a-primer-on-buck-and-boost-converters/
Now, SparkFun Director of Engineering [Pete Dokter] has a tutorial which explains how these mysterious devices work.
Tomi Engdahl says:
Perceived Brightness and Dimming Conclusion
http://www.eeweb.com/company-blog/recom/perceived-brightness-and-dimming-conclusion/
Having discovered that there is no ideal way to dim LEDs, we hit the next problem: our eyes. Human visual perception of brightness is non-linear. At low light levels, our irises automatically open to let in more light – so we perceive the LED to be brighter than a simple light meter would indicate it to be. To work out the relationship between perceived brightness and measured brightness, you take the square root of the normalized measured light, e.g. a LED dimmed to a quarter (0.25) of the nominal LED current would appear to be 0.5 or half as bright to our eyes.
So although almost all LED driver manufacturers persevere to make their dimmers dim as linearly and as mathematically accurately as possible, our eyes naturally prefer the non-linear curve of the incandescent lamp as it matches our perception of brightness much more closely than the linear response of the LED. At present, the demand from the LED lighting market is for linearity over naturalness because it makes the matching up of different lights easier, but this may change in the future as the market matures and the demand for more natural dimming increases.
LED dimming may be represented as a “done deal” by many ballast suppliers who confidently write specifications like 1:1000 dimming ratios in their datasheets even though their output accuracy is only +/- 5% (1:20), but this short discussion shows that accurate, linear and flicker-free LED dimming still cannot be taken for granted, despite the many thousands of different dimmable LED drivers on the market.
Tomi Engdahl says:
LED Dimming
http://www.eeweb.com/company-blog/recom/led-dimming/
However LEDs are dimmed – be it by 1 – 10 V analogue voltage, mains phase angle, power-line, digital inputs such as DALI, or a WLAN link, there is in fact only two ways to actually dim the output of a LED; either by linearly reducing the current through the LED (analogue dimming) or by switching it off and on very quickly with different mark/space ratios (PWM dimming). Although both methods achieve the same effect, there are important differences in the way they work in practice, which makes the right choice of dimming method critical to many applications.
Analogue dimming can give very linear dimming curves apart from the extremes of adjustment at almost full brightness or almost total darkness. At the brightest dimming levels, saturation effects in the comparator can generate non-linear responses; while at the dimmest light levels the current through the shunt resistor is so low that the input offset voltages in the measuring amplifier become a significant source of error. The overall result is unavoidable non-linear dimming in the bottom 3% and top 3% of the dimming range for even a well-designed analogue dimming circuit.
An alternative to analogue dimming is PWM dimming.
PWM dimming is not as linear as analogue dimming. When the PWM control input goes low the output voltage does not switch off immediately as the output capacitance needs to discharge through the LED load. When the PWM input goes high, the voltage regulator has a delayed reaction time to the enable input as if first needs to powers up. These switch-on and switch-off delays mean that relatively low frequency PWM signals need to be used (a few hundred Hz) and the dimming responses is non-linear. In many designs, these delays mean that PWM dimming below 10% is not possible because the driver cannot react in time to the brief input signal.
Tomi Engdahl says:
30 W Isolated Flyback 1-10 V Analog Dimming LED Driver
http://www.eeweb.com/company-blog/power_integrations/30-w-isolated-flyback-1-10-v-analog-dimming-led-driver/
This design example report is a 30 W isolated flyback, 1 to 10 V analog dimming LED driver employing LYTSwitch™-4 LYT4315E. This design operates at 90 VAC to 132 VAC input voltage range and delivers an output of 30 V to 60 V at 0.5 A current output. It features wide output voltage range with accurate constant current regulation, single-stage pwoer factor correction, consistent dimming peroformance across output and input voltage range, energy efficient at 115 V, constant voltage open load protection, and integrated protection.
The key design goals were to achieve high efficiency, 1 V to 10 V dimming and constant current regulation across the output range.
The LYTSwitch-4 driver IC, combines the PFC function which both meet power factor and harmonics requirements.
The topology used is an isolated flyback operating in continuous conduction mode. Constant current and dimming regulation are achieved through a secondary feedback control
The document contains the power supply specification, schematic, bill of materials, transformer documentation, printed circuit layout, design spreadsheet and performance data.
Tomi Engdahl says:
More Than Efficient Lighting: An Effective LED Driver Using an 8-Bit MCU
An 8-bit microcontroller can create an effective LED driver and add advanced features that make the lighting solution even more attractive.
https://www.designnews.com/electronics-test/more-efficient-lighting-effective-led-driver-using-8-bit-mcu/126476129147250?cid=nl.x.dn14.edt.aud.dn.20170112.tst004t
In today’s energy-conscious environment, LEDs are often favored over conventional light sources. This is because of their inherent low power and long life. In addition to this, since LEDs are solid-state lighting (SSL), they can be dimmed, allowing the user to create fantastic lighting effects while reducing the overall power consumption.
Obtaining these benefits from LEDs requires an effective LED driver. The LED driver’s effectiveness is linked to its ability to provide an efficient energy source, to ensure LED’s optimal performance and to maintain the long life of LEDs, even both as the driver keeps the LED output intensity constant and while changing intensity. Also, an LED driver that is intelligent and has advanced capability can make lighting solutions even more attractive.
Although an effective LED driver can offer many advantages, there are also challenges in its implementation. This article will show how an 8-bit microcontroller (MCU) can be used to alleviate design challenges and create high-performance LED driving solutions with capabilities beyond that of traditional solutions.
Tomi Engdahl says:
Careful design delivers halogen-like LED dimming (MAGAZINE)
http://www.ledsmagazine.com/articles/print/volume-10/issue-10/features/careful-design-delivers-halogen-like-led-dimming-magazine.html?cmpid=enl_leds_architecturalillumination_2017-07-24
Enabling LEDs to follow the black-body radiation curve isn’t black magic, and Uwe Thomas explains a successful approach to the challenge of dimming SSL products to warm CCTs.
People are comfortable with the familiar, uncomfortable with the unexpected. When a halogen or incandescent lamp is dimmed, less current passes through the lamp filament. The filament cools down, producing a warmer light with a greater proportion of radiation at the red end of the spectrum. As a result, we are conditioned to expect that dimming a lamp will produce a warm, relaxing ambience. LEDs produce light through a different physical mechanism — electroluminescence rather than incandescence. Here there is no significant color temperature shift when the current that passes through an LED die is reduced in order to lower its lumen output. You must design LEDs and solid-state lighting (SSL) systems to dim like halogen lamps.
Directional halogen lamps are popular in hospitality environments. But in these applications, the well-documented benefits of LED lighting over halogen lamps are desirable. In particular, LED light sources are far more efficient at converting electricity into light, so they save energy and run cooler. However, making an LED source dim with a similar color shift to a halogen source, maintaining color quality along the way, has presented significant technical challenges to designers of LED emitters and fixtures.
The aim has been to find an LED emitter that closely follows the idealized black-body curve as it dims. Better still would be one that follows the curve even more closely than halogen sources.
The light emitted from the tungsten filament follows the idealized black-body curve quite closely but does deviate somewhat from the ideal black-body curve, producing a greenish tinge at some temperatures. Color quality, defined in terms of color rendering index (CRI), is well maintained by halogen lamps as they dim.
The light from an LED is not created by thermal radiation. LEDs create light through electroluminescence. Light is emitted when electrons and holes recombine in a material, most commonly a semiconductor. The spectrum, or color, of light emitted is determined primarily by the constituent materials of the semiconductor and by phosphors — chemicals used to coat the LED die. As a result, when an LED dims as less current is passed through it, the color temperature shift is very small because thermal radiation represents a negligible portion of the total light emitted. In fact, the hue change as an LED dims is hardly discernible to the human eye.
We’re accustomed to halogen-like dimming, and to the high CRI of halogens being maintained as they dim. CRI is most noticeable in skin tones.
We identify detail through the green and red regions of the spectrum and perceive luminance changes primarily within the green part. Incidentally, pure white is, by definition, 76% green, 22% red, and 12% blue light.
We’re used to halogen dimming; we feel familiar and comfortable with the effect and if a light dims without appearing to create a warmer white, it feels unnatural — something that’s very undesirable in a hospitality environment such as a restaurant, bar, or hotel.
Which vital characteristics count?
If we are going the change the color of an LED light source along the black-body curve or other profile as it dims, we must mix the light from at least three types of die to produce a range of white tones, or color temperatures. To make a white LED emitter, you coat a blue LED die with a combination of red and yellow phosphors. Most commonly, die that produce light at 445–455-nm wavelength are used, but those that produce longer wavelengths may be adopted. The combination of die wavelength and yellow/red phosphor recipe is used to achieve the desired color points.
Phosphors may be sprayed onto the LED wafer before it’s sliced up to create the individual die, or printed directly onto the die.
Combining multiple different die/phosphor configurations can produce color temperatures ranging from 1800K to 5500K when mixed within a single high-density package.
In order for light to be mixed effectively, the LED die must be closely packed on the substrate.
At 3000K, a CRI of 90 and R9 of 80 can be achieved and across the dimming range the CRI average is 85; the red component, R9, averages 70.
Tomi Engdahl says:
Control Thy LED
https://hackaday.com/2017/08/29/control-thy-led/
The idea is to be able to effectively control the brightness of the LED and prolong their life while doing it. An efficient driver can make all the difference if you plan to deploy them for the long-haul. Let’s take a look at the problem and then discuss the solutions.
The easiest thing to do is add a potentiometer in series with the LED. Simple! Essentially when you vary the resistance, Ohm’s Law kicks in and voila! Variable resistance equals variable current equals variable brightness.
Next easiest is to create a constant current circuit. There are a number of ways to create a simple constant current source
The Digital Method
The next circuit involves the use of a set of pulses to switch ON and OFF the current through the LED. It’s like flicking the power switch quickly enough that it seems like the light is dimmed. Commonly known as PWM or Pulse Width Modulation, a series of pulses with variable duty cycles or ON and OFF times can be employed for the task.
For generating the pulses, the humble 555 is a good choice.
You can use a BJT or a FET or a MOSFET depending upon your budget and state of mind. BJTs are simpler creatures and require very few additional components. A 2N2222 can safely deal with 800 mA of current which is good for many applications.
MOSFETs are an LED’s Best Friend
A MOSFET has a very low ON resistance of the order of a few milliohms which means that in such a state, it will dissipate very small amounts of heat as per P = I2R.
LED Drivers
Dedicated LED driver chips enable you to control LEDs effectively without having to think about all the parameters. A good example is the TPS92512 which allows for control of high brightness LEDs using PWM which is internally controlled. Current control is implemented internally and external signals including PWM as well as analog signals can be used to control the brightness linearly. No need for lookup tables.
Conclusion
So how do you drive an LED? The answer lies in your application area. For small LED current draws, BJTs are simpler and the least expensive. For medium current draws, MOSFETs are a better fit and if you want solutions that offer great out-of-the-box experiences, dedicated driver chips are the way to go.
Know Thy LED
https://hackaday.com/2017/08/08/know-thy-led/
Tomi Engdahl says:
LED driver offers dual dimming modes
https://www.edn.com/electronics-products/other/4459018/LED-driver-offers-dual-dimming-modes
A single-stage LED driver-converter with an integrated 2 A, 600 V MOSFET, Diodes’ AL1673 allows both PWM and analog dimming. When a 0.3 VDC to 2.4 VDC signal is applied on the APWM pin, the device operates in analog dimming mode. When a digital signal is applied on the same pin, the AL1673 operates in PWM dimming mode. The AL1673’s PWM dimming range is 3% to 100% at a 1 kHz PWM frequency. Analog dimming range is 12% to 100%.
The AL1673 is a constant-current flyback/buck-boost converter with primary-side regulation control.
Sold through Diodes’ distributor network, the AL1673 LED driver costs $0.58 each. In lots of 1000 units, the cost of the driver drops to $0.24720 each.
https://www.diodes.com/products/power-management/led-drivers/off-line-led-drivers/part/AL1673
Tomi Engdahl says:
Dimming LED lamps with ordinary dimmers.
https://www.youtube.com/watch?v=fWh2obSY0dQ
Using a traditional phase angle control wall-plate dimmer (the usual type) is just a terrible way to dim LED lamps. The rough chopping of a 50/60Hz sinewave with sharp voltage transitions is very hard to convert to a proper smooth and flicker free dimming of an LED lamp over a decent range. LED lamps also provide a very low load with sudden drop-off of current which can make ordinary dimmers very unstable.
How to Dim LEDs – the COMPLETE Buying Guide
https://www.youtube.com/watch?v=IB-CF0xCiDY
Tomi Engdahl says:
Using a Dimmer Switch with LED Bulbs
https://www.youtube.com/watch?v=z_gC_GXVL4w
Using a light dimmer with an LED bulb can be a bit confusing. Only a few dimmers are rated for dimmable LEDs and dimmable LED bulbs can vary greatly. In this video we will look at how the typical dimmer works along with a couple varieties of dimmers. In addition we will look at two different dimmable LED bulbs. An IntegraVision Power Analyzer is used to view the voltage, current, and power going into and out of the dimmer switch. IntegraVision allows the real time display and analysis of power waveforms.
Ask An Expert – How do I get my LED lighting design to dim and not flicker using CCR LED drivers?
https://www.youtube.com/watch?v=ofr9jwsMD3I
Learn how to get LED lights to dim and not flicker using the NSIC2050JBT3G constant current LED driver. Application experts answer your LED lighting design questions. Understand the basics of LED light dimming methods and the causes of LED lighting
Tomi Engdahl says:
Dimming LED lamps with ordinary dimmers.
https://www.youtube.com/watch?v=fWh2obSY0dQ
Using a traditional phase angle control wall-plate dimmer (the usual type) is just a terrible way to dim LED lamps. The rough chopping of a 50/60Hz sinewave with sharp voltage transitions is very hard to convert to a proper smooth and flicker free dimming of an LED lamp over a decent range. LED lamps also provide a very low load with sudden drop-off of current which can make ordinary dimmers very unstable.
Tomi Engdahl says:
http://www.etn.fi/index.php/tekniset-artikkelit/8453-ledivalon-himmennys-kay-katevasti-mikro-ohjaimella
Tomi Engdahl says:
An Illuminating Look at LED Driving
https://www.electronicdesign.com/analog/illuminating-look-led-driving?Issue=ED-004_20181016_ED-004_843&sfvc4enews=42&cl=article_1_b&utm_rid=CPG05000002750211&utm_campaign=20689&utm_medium=email&elq2=590fb56701b34fb3b3e8b0c7d349eb70
Sponsored by Texas Instruments: The LED is the dominant lighting solution today, but the processes involved in driving and dimming them are more sophisticated than you perhaps thought.
Tomi Engdahl says:
Dimming LED lamps with ordinary dimmers.
https://www.youtube.com/watch?v=fWh2obSY0dQ
Using a traditional phase angle control wall-plate dimmer (the usual type) is just a terrible way to dim LED lamps. The rough chopping of a 50/60Hz sinewave with sharp voltage transitions is very hard to convert to a proper smooth and flicker free dimming of an LED lamp over a decent range. LED lamps also provide a very low load with sudden drop-off of current which can make ordinary dimmers very unstable.
Tomi Engdahl says:
http://www.etn.fi/index.php/13-news/8693-ledinelikko-nayttaa-koko-variskaalan-langattomasti
Tomi Engdahl says:
Different Dimming Types for LED Lighting
http://www.light.fi/blog/different-dimming-types-for-led-lighting/
Leading & trailing edge dimming
There are dimmers and equipment that support both types of dimming, and others that support only one type.
The 1-10V system enables dimming of the luminous flux from around 1…10% to 100%. This is done by sending an analogue signal to the equipment over an additional, two-wire control line.
The analogue signal has a direct voltage value of 1V to 10V. 1V or short-circuiting the fixture’s input control gives the minimum light level. While 10V or leaving the input control circuit open gives out the maximum light level.
International standard, IEC 60929, defines the regulation curve.
It reflects a practically linear relationship in the range of 3V to 10V.
These in light fixtures generate power control with 1-10V dimming. Driver supplies a current to the controller through equipment control terminals. The controller current must be from 10µA to 2mA. The maximum control line current is obtained with a voltage of 1V and the minimum with a voltage of 10V.
Tomi Engdahl says:
DIm & Dimmer – design for test & installation
https://www.youtube.com/watch?v=cQWnLOCGpXM
Tomi Engdahl says:
Lamp Dimmers – Leading and Trailing Edge
https://www.youtube.com/watch?v=EDmXiG5AvSQ
A demonstration of the difference between leading edge dimmers and trailing edge dimmers using an oscilloscope.
Tomi Engdahl says:
Lediohjaimia vaativiin tehosovelluksiin
http://www.etn.fi/index.php/tekniset-artikkelit/9520-lediohjaimia-vaativiin-tehosovelluksiin
Tomi Engdahl says:
https://www.utu.eu/utulta-uudet-led-kiertovalonsaatimet-optimaaliseen-himmentamiseen
Tomi Engdahl says:
A Portable Flickering Detector for Any PWM-Operated Light Source
This DIY device lets you actually hear a light’s frequency.
https://www.hackster.io/news/a-portable-flickering-detector-for-any-pwm-operated-light-source-d20ece84685b
Tomi Engdahl says:
https://www.luxreview.com/2016/02/16/10-things-you-must-know-before-you-dim-led-lamps/
Tomi Engdahl says:
The Basics Behind Constant-Current LED Drive Circuitry
August 23, 2016 by Robert Keim
https://www.allaboutcircuits.com/technical-articles/the-basics-behind-constant-current-led-drive-circuitry/
This technical brief discusses the reasoning behind and implementation of constant-current drive circuitry for illuminating LEDs.
Tomi Engdahl says:
The Basics Behind Constant-Current LED Drive Circuitry
August 23, 2016 by Robert Keim
https://www.allaboutcircuits.com/technical-articles/the-basics-behind-constant-current-led-drive-circuitry/
This technical brief discusses the reasoning behind and implementation of constant-current drive circuitry for illuminating LEDs.
What Type of LED Driver Do I Need? Constant Current vs. Constant Voltage
https://www.ledsupply.com/blog/constant-current-led-drivers-vs-constant-voltage-led-drivers/
Tomi Engdahl says:
https://www.circuitcrush.com/how-leds-work-intro/
Tomi Engdahl says:
Dimmable mains LED bulbs
http://lednique.com/bulbs/dimmers-for-leds/
Not all mains bulbs are dimmable. Those that are may require special dimmers to operate. In this article we explain how filament lamp dimmers work and some of the issues that can occur with LED lamps.
Tomi Engdahl says:
The Subtle Circuitry Behind LED Lighting
The circuitry behind LED lighting poses tricky challenges
https://spectrum.ieee.org/energy/environment/the-subtle-circuitry-behind-led-lighting
Tomi Engdahl says:
Synchronous Boost Converter Powers High-Current LEDs Even at Low Input Voltages
https://www.electronicdesign.com/power-management/whitepaper/21153115/analog-devices-synchronous-boost-converter-powers-highcurrent-leds-even-at-low-input-voltages?utm_source=EG+ED+Analog+%26+Power+Source&utm_medium=email&utm_campaign=CPS210120095&o_eid=7211D2691390C9R&rdx.ident%5Bpull%5D=omeda%7C7211D2691390C9R&oly_enc_id=7211D2691390C9R
To overcome the limitations of asynchronous dc-dc converters, designers can implement a synchronous boost LED controller to deliver the required high output current via its synchronous switching.
Tomi Engdahl says:
A Relatively Easy Way to Realize a Programmable LED Driver
https://www.electronicdesign.com/power-management/whitepaper/21154356/analog-devices-a-relatively-easy-way-to-realize-a-programmable-led-driver?utm_source=EG+ED+Analog+%26+Power+Source&utm_medium=email&utm_campaign=CPS210204078&o_eid=7211D2691390C9R&rdx.ident%5Bpull%5D=omeda%7C7211D2691390C9R&oly_enc_id=7211D2691390C9R
This particular driver is well-suited for lighting-control applications that need a compact, scalable, easy to power, and highly linear power source, but be wary of the applications requirements.
Tomi Engdahl says:
LED driver basics
Learn about a variety of LED driver design topics, from PWM and analog dimming methodologies to overcoming specific system design challenges.
https://training.ti.com/led-driver-basics?HQS=app-psil-led-leddriverbasics-agg-tr-ElectronicDesign-wwe&DCM=yes&DCM=yes&dclid=CL_Jyp3mj_QCFUmQGAoddlMA3w
Tomi Engdahl says:
https://www.winled.fi/blogi/artikkeli/Voiko-Led-valoja-himment%C3%A4%C3%A4
Yhteenveto: Kaikkia ledejä voi himmentää
Yksinkertaisuudessaan kaikkia ledejä voi himmentää oikeanlaisella himmentimellä. Jopa niin sanottujen “ei himmennettävien” ledejen himmentäminen onnistuu, mikäli käytössä on ledeille tarkoitettu PWM-himmennin. Harhaanjohtavan tästä tekee se, että kysymyksellä “voiko ledejä himmentää” oikeasti käytännön elämässä tarkoitetaankin sitä, että voidaanko ledejä himmentää sellaisilla säätimillä, jotka on alun perin tarkoitettu halogeeneille tai hehkulampuille. Ja tämä ei aina onnistu, ellei ledeihin ole lisätty aiemmissakin kappaleissa mainittua elektroniikkaa.
Led-lamppujen ja valaisinten yleistyttyä muutamia vuosia sitten aloimme näkemään kahden suuntaista kehitystä. Himmenninvalmistajat alkoivat valmistamaan ledeille tarkoitettuja himmentimiä ja led valaisinvalmistajat alkoivat valmistaa hehkulamppu- ja halogeenisäätimillä himmentyviä ledejä. Nyt selkeästi näistä kahdesta suuntauksesta suositummaksi onkin muodostunut se, että led valaisin valjastetaan sellaisella virtalähteellä (muuntajalla), joka sopii yhteen hehkulamppu- ja halogeeni himmentimien kanssa. Viime vuosina käytäntöön vakioitunut “himmennettävä” termi ledeissä tarkoittaakin siis sitä, että lamppu tai valaisin himmenee hehkulamppu- ja halogeenisäätimillä. Näitä säädintyyppejä kutsutaan nimillä TRIAC (Tyristori / transistorisäädin hehkulampuille)
Mikä himmennin sopii ledeille
https://www.winled.fi/blogi/artikkeli/Mik%C3%A4-himmennin-sopii-ledeille
Tämän artikkelin tarkoituksena on auttaa teitä löytämään oikea himmennin led valaisimille. Perehdymme erilaisiin valonsäätimiin (tutummin himmentimiin), niiden toimintaperiaatteisiin ja käyttötarkoituksiin.
Selvennämme miksi toiset ovat paremmin soveltuvia led valaisimille kuin toiset sekä testaamme miten himmentimet käytännössä toimivat ledeillä.
Millaisia erilaisia himmennystapoja on?
Toisin kuin hehku- ja halogeenilamput, led-polttimot toimivat tasajännitteellä, jolloin virta kulkee vain yhteen suuntaan. Tästä syystä led-polttimoita ei voi kytkeä suoraan vaihtovirtaverkkoon, vaan se vaatii erillisen muuntajan, yleisimmin 12V tai 24V. Ledien tyyppi vaikuttaa esimerkiksi ohjaimen valintaan ja niiden himmentäminen poikkeaa toisistaan.
Vakiojännitteellä toimivat muun muassa retrofit-polttimot, valonauhat ja suurin osa led-listoista. Näitä valoja ei voida himmentää syöttöjännitettä säätämällä, sillä usein säätöalue on niin pieni, että valo saattaa sammua äkillisesti. Vakiojännitelähde toimii aina vakio jännitteellä, esim. 12V ja valaisin himmentyy säätämällä tehonlähteestä ulostulevaa virtaa.
Vakiovirralla toimivat muun muassa led-paneelit sekä suurin osa led alasvaloista. Näiden valaisinten muuntajissa on merkittynä ohjausvirta (mA) ja jännitteen vaihteluväli, esim. 8-16V. Jotkut ledit on suunniteltu toimimaan tietyllä virtamäärällä ja ne vaativat toimiakseen vakiovirtalähteen, joka pitää tehonlähteestä ulostulevan virran vakiona ja säätelee jännitettä kuorman mukaan pitääkseen ulostulo virran ilmoitetussa arvossa.
Vaihtovirtahimmennyksessä ensiöpuolella käytetään yleisimmin laskevan reunan (trailing edge) himmennystapaa, mutta on myös olemassa ledille soveltuvia nousevan reunan (leading edge) himmennystapaa tukevia virtalähteitä.
Osa ledien teholähteistä ei kestä ensiöpuolen himmennystä, jolloin himmennin asennetaan teholähteen ja valaisimen väliin.
Leading Edge
Kutsutaan myös TRIAC-himmentimiksi. Yleensä käytetty hehkulamppujen ja magneettisten muuntajien kanssa.
. Signaalia nousevalta osalta leikatessa virrannousunopeus on suuri ja tämä aiheuttaa häiriöitä sähköverkkoon. Voi aiheuttaa surinaa himmentäessä.
TRIAC-himmentimet ovat suunniteltu resistiivisille kuormille, kuten hehku- ja halogeenilampuille. TRIAC-himmentimien toimivuus LED valojen kanssa ei ole mikään itsestään selvyys: osa markkinoilla olevista säätimistä toimii, mutta suurin osa ei.
Trailing Edge
Kutsutaan myös elektronisiksi himmentimiksi. Sinimuotoinen signaali katkaistaan signaalin loppuosasta. Etuja nousevan reunan himmennykseen verrattuna on pehmeämpi ja sulavampi säätö, sekä muuntajan hiljaisuus (ei surinaa) ja pienempi häiriön tuotto sähköverkkoon.
0-10V ja 1-10V himmennys
Analooginen valaistusohjaus protokolla, jonka säätöjännite toimii välillä 0-10V. Ohjatun valaisimen valoteho on 100% 10V:lla ja alimmalla mahdollisella tasolla 0V:lla. Mikäli valaisin ei tue alle 10% himmentämistä, tulee himmentimeen lisätä rele, joka katkaisee valaisimelta jännitteen. Useimmissa himmentimissä rele on kuitenkin rakennettu itse himmentimen sisään.
Tämä himmennystapa on yksi ensimmäisistä ja yksinkertaisimmista himmennystavoista ja sitä käytetään laajalti edelleen. 0-10V himmennyksestä on muovautunut luotettava protokolla ledien himmentämiseen. 1-10V himmennyksen käyttö jo valmiiksi energiatehokkaan led valaistuksen ohjaukseen auttaa säästämään energiaa ja hallitsemaan valaistusratkaisujasi paremmin.
DMX
Kaikessa yksinkertaisuudessaan DMX on valaisinten kommunikointiväylä, jonka avulla valaisimet lähettävät ja saavat tietoa siitä, mitä tehdä ja milloin. Valaistusta ohjataan DMX konsolin (valopöydän) avulla, jonka perään voidaan ketjuttaa 32 kappaletta valaisimia.
Valoja voidaan ohjata myös esimerkiksi tietokoneella sovelluksien kautta ja se vaatii sovelluksen lisäksi tietokoneen perään sopivan DMX rajapinnan, joka lähettää tarvittavaa tietoa valaisimille. Useissa DMX ohjaukseen soveltuvissa sovelluksissa on myös mahdollista visualisoida valaistusta 3d:nä, jolloin eri tilanteiden ja efektien luonti on mahdollista suunnitella ilman, että valoja käytettäisiin fyysisesti.
DALI
DALI (Digital Addressable Lighting Interface), on digitaalinen valaistuksen ohjausväylä, joka perustettiin aikoinaan markkinoita hallinneen analogisen 0/1-10V järjestelmän seuraajaksi. DALIn lähtökohtainen idea on luoda mahdollisimman yksinkertainen ja selkeä järjestelmä valaistuksen ohjaukseen. DALI perustuu laitekohtaiseen ohjaukseen: yhden ohjauslaitteen verkossa voi olla maksimissaan 16 ohjattavaa ryhmää, 16 erilaista valaistustilannetta sekä 64 kuormaliitäntää tai ohjauslaitetta. DALI käyttää hajautettua väylää, mikä tarkoittaa sitä, ettei erillistä keskusyksikköä tarvita, vaan jokaisessa DALI-laitteessa on muisti, johon kyseisen laitteen asetukset tallennetaan.
Suomessa yleisimmin käytetyt valonsäätimet
Schneider
Katso tästä Winled-valaisimien yhteensopivat ja testatut himmentimet: Schneider Himmennystaulukko – Winled Oy
Exxact
Kehitetty pohjoismaista asennuskäyttöä noudattaen.
Suunniteltu vastaamaan nykyaikaisia asennusvaatimuksia.
Pohjoismaiden laajin valikoima
Kehys ja koje erotettu toisistaan, tukemaan ympäristöystävällisempää tilaustapaa.
Robust
Vaativiin ja kulutukselle alttiisiin kohteisiin.
Iskunkestävä (IK09) ja turvallinen.
Käytetään usein kouluissa, lentoasemilla, hotelleissa ja muissa julkisissa tiloissa
Renova
Perinteisen tyylisiä asennuskalusteita kahdessa perusvärissä: musta ja valkoinen (saatavilla myös metallin värisiä kehyksiä).
Pääty- ja keskikehyksillä voidaan toteuttaa kalusteyhdistelmiä.
ABB
Katso tästä Winled-valaisimien yhteensopivat ja testatut himmentimet: ABB Himmennystaulukko – Winled Oy
Impressivo
Suunniteltu suomalaisiin koteihin ja asennuskulttuuriin.
Tuotekehityksessä keskitytään toimivuuteen ja turvallisuuteen.
Saatavilla kolmessa värissä: valkoinen, alumiini ja antrasiitti.
Yhdisteltävissä eri värisillä Axcent ja Carat-peitelevyillä.
Jussi
Kehitetty pitkäjänteisesti käyttäjien mielipiteitä kuunnellen.
Laadukas, turvallinen ja asentajaystävällinen.
Kellastumaton ja helppo pitää puhtaana.
Himmentimet led nauhoille
Yleisimmin led nauhoja himmennetään tavallisilla TRIAC himmentimillä. Muun muassa kaikista yllä luetelluista yleisimmistä kalustesarjoista tämmöisiä himmentimimiä löytyy.
Tällöin tulee kuitenkin huomioida, että nauhan muuntaja on ns. “himmennettävä”, eli yhteensopiva TRIAC-säätimien kanssa. Käytännössä valonauhoja voi himmentää millä tahansa himmennystyylillä, kyse on vain oikeanlaisen muuntajan valinnasta.
DALI-ympäristöön löytyy markkinoilta himmennettäviä DALI-virtalähteitä, mutta kokemustemme mukaan paremman lopputuloksen saa, kun käyttää PWM-muuntajaa signaalinmuuntimen kanssa.
Tomi Engdahl says:
Pre-Emptive Boost Control Improves LED Driver Performance
https://www.allegromicro.com/en/insights-and-innovations/technical-documents/peb-control?utm_source=electronicdesign.com&utm_medium=referral&utm_campaign=Personif.ai&utm_term=&utm_content=pre-emptive-boost-control
Tomi Engdahl says:
https://shop.lumoscontrols.com/blogs/lumos/0-10-v
1-10V Vs 0-10V dimming
The main difference between 1-10V and 0-10V dimming is the current direction. 1-10V can DIM the load down to 10%, while the 0-10V can DIM the load down to 0% (DIM to OFF).
A 0-10V dimmer is a 4-wire device that receives an AC power signal and converts it to a DC 0-10V dimming signal based on the user input.
In the 0-10V dimming, when the controller receives the message to provide the required light intensity via the user interface (APP/Switches/Remote), it sends the voltage value to the driver via 0-10V wire. The driver will then respond to the corresponding value and adjust the intensity of the light devices. For example: If the controller receives 0 V as an input value, the driver will respond accordingly to this input value, and the luminaires will be turned OFF. However, in 1-10V dimming, the driver should be powered via relay (switch) to turn OFF the lights completely.
0-10V mA Rating
Every 0-10V device has a rating that determines the amount of current it sources or sinks. The IEC 60929 (International Standard created by the International Electro Technical Commission) standard dictates a minimum ballast source current of 10 µA and a maximum of 2 mA. Understanding the sink and source current is crucial to decide the maximum number of ballasts/drivers that a single control circuit can manage.
Where to Use a 0-10V Dimming?
0-10v dimming was developed as a standard method to control the light intensity. As LED technology progressed, 0-10V gained popularity as the most reliable dimming method. It can be used in :
Retail spaces
Offices and homes
Outdoor spaces
Spaces where multipurpose lighting is required
https://www.varilight.co.uk/leaflets/HF%20Single%20Ballast%20Dimmer%20Instructions%20112A.pdf
Tomi Engdahl says:
Standard EU type panel, size 84*84mm
Tomi Engdahl says:
Dimmers And LEDs
https://sound-au.com/lamps/dimmers+leds.html
Tested Controller Circuit For 0-10V Dimmable Drivers
5.1 – 0-10V Dimming Controller
Given that 0-10V dimming is now quite popular and is being used in many installations, one would have hoped that schematics for simple controllers would be easy to find. Unfortunately (and not for the first time) this is not the case. Not only are circuit diagrams for the controllers themselves absent from the Web, but even the physical controllers are not easy to find. In some cases you will find what you’re looking for, but I’ve seen what appear to be exceptionally simple controllers on-line for well over AU$100, which is far, far greater than their value. Meanwhile, others (which appear to do exactly the same thing) sell for not much over AU$17 or so. The sellers provide next to no information about how they are to be used, so it’s hard for people to know what they are getting.
The circuit shown above is a simple passive (it needs no power supply) controller, which will work with any LED power supply that provides more than 200µA for the dimmer. It will function with lower current, but the dimming range becomes rather non-linear. This isn’t a precision circuit, and it may be more or less complex than commercial versions.
The dimmer controller would normally be mounted on a standard wall-plate, along with the on/off switch for the controlled lights. Note that a separate wiring run is needed for the 0-10V dimming connections, but this ‘daisy chains’ from one fitting to the next. The maximum current for the controller shown is around 25mA (half the maximum current shown above), and Q2 will run warm at that current. There should be no more than 25 separate fittings connected to a single dimmer controller, or the number of fittings that amount to 25mA current, whichever is the lower number. For example, if the LED drivers output 2mA (the maximum recommended), then no more than 12 fittings should be on a single dimmer circuit.
At the time of writing, this is the only schematic on the Net for a passive 0-10V current-sinking dimmer controller. It may or may not follow industry practice, but it works very well. It’s been tested with a dimmable LED highbay, the only 0-10V dimmable fitting I had to hand when the circuit was developed. I expect that it will perform equivalently with any standardised equipment. While it does work at the lowest current suggested in the standard (10µA), it really needs at least 100µA to function properly. (It is doubtful that many commercial products would use a 10µA sense current because it’s too low, the overall impedance is too high and noise may become a problem.)
So, if you want to have dimmable LED lamps, feel free to experiment.
In fact, you must experiment, because the results are almost always unpredictable!
Even when you find a combination that works well, don’t expect the same dimming range or stability that you had with incandescent lamps, because you probably won’t get it. You might be lucky, but a seemingly infinite number of sites on the Net telling you of the problems encountered doesn’t bode well. This really is a case of buyer beware – the lights are usually very good (from reputable manufacturers at least), but dimming is another matter entirely. 0-10V standardisation is very much a step in the right direction, but only for fixed installations.
Ultimately, the best approach (and the one that will endure) is to use complete fixtures/ luminaires and forget the silly idea of replaceable globes. If you need dimming, choose a product that includes a 0-10V interface, but you will have get an electrician to install the extra wiring needed for the dimmer unit itself.
Tomi Engdahl says:
https://www.dreamline.at/media/pdf/28/29/04/85166.pdf
https://www.sunricher.com/media/resources/manual/SR-2205-v2%20instruction.pdf
Tomi Engdahl says:
https://www.sal.net.au/products/smart-controls-and-electrical-accessories/electrical-accessories/SDF30
Tomi Engdahl says:
https://github.com/SupremeC/ESP8266_MQTT_dimmer
Tomi Engdahl says:
https://www.electroschematics.com/simple-dc-dimmer-circuit/
Tomi Engdahl says:
0-10V Digital Rheostat for LED Dimmer?
https://electronics.stackexchange.com/questions/322950/0-10v-digital-rheostat-for-led-dimmer
Many of the LED power supplies such as those by Mean Well, etc., offer three modes of control: output constant current level can be adjusted through the control input by connecting a resistance or 0 ~ 10Vdc or 10V PWM signal between DIM+ and DIM-.
If the PSU is able to sense a resistance connected to the input then it must be supplying a current to the input terminals as shown by the constant current source. On the units I am familiar with 100 kΩ gives full brightness so that means the voltage drop across the 100 kΩ is 10 V and I = V/R = 10/100k = 0.1 mA. This theory is supported by the fact that if you use one pot to control multiple fittings that the required pot value is 100/n where n is the number of lamps. This makes sense as each PSU will drive 0.1 mA into the pot. So for five lamps in parallel on the one pot R = V/I = 10/0.5m = 2 kΩ. (Your system is using a 0.5 mA source so adjust R values accordingly.)
Finally, if nothing is connected the 0.1 mA will charge C1 to 10 V and give 100% brightness.
Tomi Engdahl says:
https://www.allegromicro.com/en/insights-and-innovations/technical-documents/peb-control?utm_source=electronicdesign.com&utm_medium=referral&utm_campaign=Personif.ai&utm_term=&utm_content=pre-emptive-boost-control