Dimmable luminaire. Dimming LEDs in general and in detail

Rich Rosen, National Semiconductor

Introduction

The exponential growth in the number of LED light sources is accompanied by an equally rapid expansion of the range of integrated circuits designed to control LED power. Switching LED drivers have long replaced the voracious linear regulators unacceptable in the energy-conscious world, becoming the de facto standard for the industry. Any application, from a flashlight to stadium signage, requires precise constant current control. In this case, it is often necessary to change the radiation intensity of LEDs in real time. Controlling the brightness of light sources, and in particular LEDs, is called dimming. This article outlines the basics of LED theory and describes the most popular dimming methods using pulse drivers.

Brightness and color temperature of LEDs

LED brightness

The concept of the brightness of the visible set emitted by an LED is fairly easy to understand. The numerical value of the perceived brightness of the LED radiation can be easily measured in units of surface luminous flux density, called candela (cd). The total light output of an LED is expressed in lumens (lm). It is also important to understand that the brightness of an LED depends on the average forward current.

Figure 1 shows a graph of the dependence of the luminous flux of a certain LED on the forward current. In the range of used values \u200b\u200bof forward currents (I F), the graph is extremely linear. Non-linearity begins to appear as I F increases. When the current goes beyond the linear section, the efficiency of the LED decreases.

Picture 1.

When operating outside the linear region, much of the power supplied to the LED is dissipated as heat. This wasted heat overloads the LED driver and complicates the thermal design of the design.

LED color temperature

Color temperature is a parameter that characterizes the color of an LED and is indicated in the datasheet. The color temperature of a specific LED is described by a range of values \u200b\u200band shifts with changes in forward current, junction temperature, and as the device ages. The lower the color temperature of an LED, the closer it is to a reddish yellow color, called “warm”. Higher color temperatures correspond to blue-green colors called "cool". Often, for color LEDs, instead of the color temperature, the dominant wavelength is indicated, which can shift just like the color temperature.

Ways to control the brightness of the LED

There are two common methods of dimming (dimming) LEDs in pulse driver circuits: pulse width modulation (PWM) and analog dimming. Both methods ultimately boil down to maintaining a certain level of average current through an LED, or a string of LEDs. Below we will discuss the differences between these methods, evaluate their advantages and disadvantages.

Figure 2 depicts a pulsed LED driver in a buck converter configuration. The voltage V IN in such a circuit must always be greater than the sum of the voltages across the LED and R SNS. The inductor current flows entirely through the LED and resistor R SNS, and is controlled by the voltage applied from the resistor to the CS pin. If the voltage at the CS pin starts to fall below the set level, the duty cycle of the current flowing through L1, the LED and R SNS increases, thereby increasing the average LED current.

Analog dimming

Analog dimming is a cycle-by-cycle control of the forward current of the LED. Simply put, it is keeping the LED current at a constant level. Analog dimming is done either by adjusting the current sensor resistor R SNS or by changing the DC voltage level applied to the DIM pin (or similar pin) of the LED driver. Both examples of analog control are shown in Figure 2.

Analog dimming with R SNS control

Figure 2 shows that with a fixed CS reference voltage, a change in R SNS causes a corresponding change in LED current. If it were possible to find a potentiometer with a resistance of less than one Ohm, capable of withstanding large currents of the LED, this method of dimming would have a right to exist.

Analog dimming with CS supply voltage control

A more complex method involves direct cycle-by-cycle control of the LED current using the CS pin. For this, in a typical case, a voltage source is included in the feedback loop, taken from the LED current sensor and buffered by an amplifier (Figure 2). The gain of the amplifier can be controlled to adjust the LED current. It is easy to introduce additional functionality into this feedback circuit, such as overcurrent and temperature protection.

The disadvantage of analog dimming is that the color temperature of the emitted light can be affected by the forward current of the LED. In cases where a change in the color of the glow is unacceptable, dimming of the LED by controlling the forward current cannot be used.

Dimming with PWM

PWM dimming consists in controlling the moments of switching on and off the current through the LED, repeated at a sufficiently high frequency, which, taking into account the physiology of the human eye, should not be less than 200 Hz. Otherwise, a flickering effect may appear.

The average current through the LED now becomes proportional to the duty cycle and is expressed by the formula:

I DIM-LED \u003d D DIM × I LED

I DIM-LED - average current through the LED,
D DIM - duty cycle of PWM pulses,
I LED - LED nominal current, set by selecting the R SNS resistance value (see Figure 3).

Figure 3.

LED driver modulation

Many modern LED drivers have a dedicated DIM input that accepts PWM signals over a wide range of frequencies and amplitudes. The input provides a simple interface with external logic circuits, allowing you to turn the converter output on and off without delay for driver restart, without affecting the operation of the rest of the microcircuit nodes. A number of additional functions can be implemented using the output enable pins and auxiliary logic.

Two-wire PWM dimming

Two-wire PWM dimming has become popular in automotive interior lighting. If the VINS pin becomes 70% less than VIN (Figure 3), the internal power MOSFET is inhibited and current through the LED is turned off. The disadvantage of this method is the need to have a PWM signal driver circuit in the converter power supply.

Fast PWM dimming with shunt device

The delay in the moments of switching on and off the converter output limits the PWM frequency and the range of the duty cycle. To solve this problem, a shunt device, such as the MOSFET shown in Figure 4a, can be connected in parallel with the LED, or string of LEDs, to quickly bypass the output current of the converter bypassing the LED (s).

and)
b)
Figure 4.	Fast PWM dimming (a), waveforms of currents and voltages (b).

The inductor current remains continuous for the time the LED is turned off, due to which the rise and fall of the current stop being delayed. Now the rise and fall times are limited only by the characteristics of the MOSFET transistor. Figure 4a shows the shunt transistor connection to the LED controlled by the LM3406 driver, and Figure 4b shows oscillograms showing the difference between the results obtained when dimming using the DIM pin (top) and when connecting the shunt transistor (bottom). In both cases, the output capacitance was 10 nF. Shunt type MOSFET transistor.

When shunting the current of LEDs controlled by converters with current stabilization, one must take into account the possibility of inrush currents when the MOSFET transistor is turned on. The LM340x family of LED drivers are designed to control the turn-on time of converters to solve the emission problem. To maintain the maximum on / off speed, the capacitance between the LED terminals must be minimal.

A significant disadvantage of fast PWM dimming, in comparison with the method of modulating the output of the converter, is the decrease in efficiency. When the shunt is open, it dissipates power in the form of heat. To reduce such losses, you should choose MOSFET transistors with a minimum on-channel resistance R DS-ON.

Multi-mode dimmer LM3409

• The eye "tool" is good, but no "numerical" values. Only a spectrometer can show something concrete. Link pliz. And do you seriously believe that something is being done outside of "China" (Asian countries)?
• A link, please.
• \u003d Vlad-Perm; 111436] [B] Vladimir_007 [B] "To extend the service life, they put several more LEDs next to it (in the butt-end),"? - I have a lot of LEDs standing side by side in order to increase the total brightness ........... I'm sorry, purely by chance I got on this branch again. Numbers 6 - 8 back in the radio pilot there was an article where I also inserted my remark. It's not modest to mention the quality of LED products, a couple of magazines ago a motorist had an article on headlights - about overheating of the LED. So 6 - 8 numbers back in the article there was a driver circuit, which is a switch of garlands for 4 channels. "thanks to the driver, we increase the life of the LED by 4 times due to the fact that it works 4 times less often, also 2_th +, the duration of the diode crystal with an exponential graph increases the service life by reducing the temperature of the crystal" - approximately literally for memory ... As for photographing headlights, an LED is a stroboscope for the human eye, but with a very high switching speed and so far no one has boasted of an increase (afterglow) of the LED after a voltage failure.
• Dear [b] Vladimir_666, hello. How did you decide this? When the LED is powered by a constant current, a continuous stream of light radiation is formed. When powered by a pulsed current, light pulses are formed. LED [B] is inertia-free. This remarkable property is widely used when transmitting digital information over optical fiber at a speed of tens of Gigabytes per second or more. For him and the phosphor needs a corresponding one, which does not create an afterglow. I suppose you understand this perfectly. Speaking about a stroboscope, you obviously mean individual quanta of light. But they have not yet learned how to use them separately. It is not clear who and for what put the "minus"?
• [b] SATIR, you are kind of grass in the fact that [I] The LED is inertia-free. This is true for bare crystal LEDs. White LEDs designed for lighting have a phosphor layer. And it has some afterglow time (several milliseconds), which is quite enough when powered by pulses with a frequency of kilohertz. In addition, a filter capacitor is installed in the drivers.
• Dear [b] lllll, hello. Absolutely with you, absolutely. Agree, because the phosphor is only an accessory of the LED itself to give it the necessary properties.
• Good day. By the word stroboscope with a high frequency - I meant exactly the stroboscope. If we take the glow of an ordinary light bulb with a maximum voltage of 220V and a minimum of 0 and this with a frequency of 50 Hz - the temperature of the filament at 220V is 2200 degrees, but when the voltage drops to 0 and rises again to 220V, the filament temperature does not drop to 0, but drops to 1500 - 1800 degrees, which we see with the naked eye. As for the LED, their principle of operation is a stroboscope, with a high switching speed, which is not visible to the human eye, but this does not mean that it does not affect vision. As for the data transfer, gigabytes per second - usually data transfer is transmitted (in Morse code, a blinking light), I understand that a person would put (-), you can be stupid, if you consider yourself to be just as smart according to people's reviews - decide for yourself where you have a constantly burning light bulb and which of us needs to install -.
• Well, like 50 Hz. these are two half sine waves and really blink at 100 Hz. and the amplitude voltage is about 300 V. Who told you that? Or where did you read it? Read about the principle of work in "Vika", and the topic seems to be about powering LEDs. The normal driver powers the LED constant like this. PWM regulators are used only if you need to CHEAPLY reduce the brightness of the glow. A good driver, again, is able to reduce the current to the LED without using PWM. PWM is used in multi-mode flashlights - and if the driver is at least slightly adequate, the PWM frequency is from several kHz. Completely invisible in any use. Yeah, for me, too, when the hard drive transmits data, the "light" (LED) blinks, it blinks quickly! It is she who transmits the data!
• Do not touch Vladimir 666. He does not understand how the LED works. And, obviously, he won't understand. He came up with an incorrect explanation for himself and pushes him to the left and to the right.
• All of the above is exactly the opposite.
• ctc655 I think I have written to you in an understandable form that a constantly burning light bulb cannot transmit information if you try to protect LED manufacturers with your minus by your actions [B] not professional
• Thanks Vladimir666. My opinion of you has not improved. Alas. Even as a child, 38 years ago, they made a light telephone on a BULB. It was powered by direct current. It worked. Transferred information. Another thing is at what speed, if I may say so. But your idea of \u200b\u200bthe LED work is nonsense. Now he is a spark gap, then a stroboscope. Young people read and then start talking nonsense. If it's hard to understand, don't bother. For this they got -1. This is an assessment of the information content of the message. Your messages are not only not informative, but also give an erroneous idea of \u200b\u200bthe topic. Where there is no such big nonsense, I put nothing.
• View the topic on the same sat, that would be clear why again! http: //www..php? p \u003d 199007 # post199007 Discussion: Lighting devices based on AC LEDs are finding their niche and, perhaps, going beyond it. I'm also not 10 or 30 years old, but it will be useful for you to read. Increase knowledge in addition to a high-tech device with a pn junction. I wonder how you transmitted information with a light bulb burning on direct current 30 years ago? All lighting devices, it doesn't matter - an optocoupler, an optothyristor, etc. all work by interrupting the light flux. Probably a specially created patent for this?
• Justify or confirm. I am an "electronics engineer" - you don't have to be limited in terminology. The fact that the driver (powered from 220 V.) works according to the AC (220 V.) - DC (300 V.) - AC PWM - DC (stable required current CC) - CC circuit on the LED does not make it PWM regulator. (you could just call it a voltage rectifier!) Feedback PWM is just one way to keep the LED brightness (current) stable. But you can adjust the brightness in two ways: in the specified chain in the "AC PWM" additionally enter the "fill" adjustment (the LED will be powered by an adjustable stable current) or adjust the PWM directly [B] the average current per light. In the first case, it is powered by a stable current (there is no ripple!) In the second case, the LED is powered by "pulses" and they are basically visible. (not necessarily with my eyes - in flashlights I met the frequency of 200 Hz and 9 kHz.) Is it not a transmission of information with the Morse code?
• To be honest, I do not know why to confirm the known truth. Maybe, of course, there are some nuances in the development of regulated drivers (and they should be). I haven't done this yet. Therefore, the methods of regulation proposed by you have the right to life. But each is applied in its own way. About the Morse code. Yes, this is the transmission of information, but with an interruption in the luminous flux. And that light telephone worked on changing the brightness of the light bulb without extinguishing. In the absence of speech, the stars were constantly. I did not find the scheme. They did it in a circle and didn't have the habit of sketching diagrams yet. Also, some closed optocouplers, resistor for example, can work without interrupting the luminous flux.
• Dear [b] ctc655, hello. [B] You're absolutely right. A similar method of sound transmission is still used in cinema. At the edge of the film there is a light path that modulates the luminous flux, which is converted into an electrical signal. The method has existed since the invention of sound films! It was he who killed the tappers.
• I forgot about it. Although it may be different now. Honestly not interested in cinema for a long time.
• I do not argue that without going out the light bulb and circuits can be different, from ordinary logic to 554CA .. (3) comparators, you can just light the light bulb and pull the "flag" in front of the light, but the signal transmission always worked by changing the "1" and "0".
• In digital devices, yes. Do the light level sensors also work by the extinction of a light bulb or the sun? Moreover, the illumination level is regulated ...
• The previous topic or dispute, if you read it, was about the transfer of data by a "supposedly constantly burning light" from a DC source, that is, a battery or a stabilized power supply. (I do not want to raise the topic - where does the alternating voltage end and the constant voltage begins, since there is a lot of controversy on this topic now, starting with the battery itself .....) As for the level of illumination, you are permissible about motion sensors or night lighting around shop windows? It seems that in 1_x light in the usual sense does not correspond to the topic a little, but the principle is practically the same!

Previously, room illumination was controlled by a rheostat. A significant drawback of these devices was their high power consumption, regardless of brightness. At the minimum power of the lamp, electricity was consumed in the same amount as at the maximum, since most of it heated the rheostat.

Room lighting control

Advantages and disadvantages

You can now buy an electrical load regulator (dimmer) at an electrical store. It is mainly used to change the brightness of different types of lamps and has the following advantages:

• changing the intensity of the glow of the lamps;
• setting automatic brightness change Automatic dimmer of the glow using a timer;
• remote control;
• it is used as a switch and to set the lamp glow modes: smooth change, creation of light pictures, blinking;
• increase in lamp durability due to soft start;
• saving of consumed electricity.

Regulators have disadvantages:

• extraneous interference interferes with the operation of devices that do not have filters;
• generation of interference for other devices that receive radio signals;
• not all devices save energy;

Dimmer types

The simplest adjustable device has a switch and a rotary knob. The brightness of the regulator depends on the position of the potentiometer. The dimmer is suitable for controlling incandescent and halogen lamps. In terms of power, it is selected at least 15% higher than the connected maximum load. It must have built-in short-circuit protection. The easiest option is a fuse.

The dimmer is of the following types:

1. Overhead. Most often contains an auxiliary rheostat and is used for LED strips.
2. Checkpoint - for large areas of premises.
3. Two- and multichannel - are selected by the number of lamps and control modes.

Where do you not need to install dimmers?

1. In public places where frequent use will not allow their basic functions to be performed. Everywhere it is possible to install devices for smooth switching on of lamps built into the switches, allowing to increase their service life.
2. In places where there is no certainty about the installation of lamps.

Regulation methods

1. Mechanical - turning the handle. First, the dimmer turns on until it clicks, and then the brightness is set. The rotary-push device is more convenient, since a switch with a constant regulator setting can be used.
2. Electronic: push-button, keyboard. Can be used as a switch and regulator.
3. Touch - The control panel provides many different functions.
4. Remote - control by radio signal or by using the IR remote control.

Dimmer lamp types

• Incandescent and halogen lamps for 220V. Any dimmers can be used to change the light intensity, since the load is only active (does not have inductance and capacitance). The disadvantage is the shift of the spectrum towards red when the voltage is reduced. The power limitation for dimmers exists in the range of 60-600 W.
• Low voltage halogen lamps. For them, a step-down winding transformer is applicable, which requires a regulator that can handle an inductive load. It is marked RL. When using an electronic transformer, capacitive loads are installed.

Halogen lamps require a smooth voltage change, which increases their service life. The latest models determine the type of load and adapt to it, changing the control algorithm. It is possible to simultaneously regulate different groups of lamps: incandescent and halogen.

• Fluorescent lamps. If they are triggered by a switch, glow starter and electromagnetic choke, a conventional dimmer and rheostat will not work with them. Here you need electronic control gear (ECG).
• LED bulbs. For them, voltage regulation leads to a spectrum change. Therefore, the LEDs are regulated by changing the duration of the supplied pulses. At the same time, flickering is not noticed, since their repetition rate reaches 300 kHz.

Connecting regulators to the load

Connection to the load is made in series (Fig. A). The regulator works in the same way as a switch, but it is advisable to install the latter separately, since in case of failure from frequent switching, you will have to change an expensive dimmer to a new one.

Dimmer connection diagrams

The main requirement is polarity. The phase is always connected to the input terminal of the dimmer, marked with the letter L, and from the output, the wire goes to the lamp. The phase can be detected with a voltage indicator.

A breaker is often installed in the phase wire break (Fig. B). It is located closer to the door, and the dimmer is near the bed for convenient control.

You can install another regulator and connect them in parallel with each other (Fig. C). To do this, lead 3 wires from each device to the junction box. Such switching, similar to pass-through switches, is done in long corridors.

The use of dimmers differs in the number of loads. The single method consists in connecting one device or combined into a common group. The next control method is based on accent lights to highlight individual areas.

Adjustable room lighting

Dimmer connection

The regulator is mounted in an installation box like a conventional switch. First, it is connected in the absence of voltage in the supply wires, and then installed in the box. Then the frame and the brightness control knob are put on.

The basic scheme for regulating the light intensity of lamps is the same for most conventional devices. The only difference is in the additional details for smoother handling and stability at lower limits.

To supply voltage to the lamp, open the triac (Fig. A). For this, a voltage must be created between the electrodes.

Circuits with triac regulation for incandescent lamps: a - the simplest; b - improved

At the beginning of the positive half-wave, capacitor C is charged through the variable resistor R. When a certain value is reached, the triac opens. At the same time, the lamp comes on. Then the triac closes and a similar situation occurs on the negative half wave, since the semiconductors pass current in both directions.

Thus, “stumps” of half-waves with a frequency of 100 Hz are fed to the light bulb, which was not the case when the rheostat was used. As the brightness decreases, the flickering of light becomes more and more apparent. To avoid this, details are added to the diagram, as shown in Fig. b. Triacs are installed according to the actual load, and the permissible voltage is 400V.

By selecting the values \u200b\u200bof resistors and capacitors, you can change the initial and final moments of ignition and the stability of the lamp glow.

For LED lamps

Despite the efficiency of LED lamps, garlands and ribbons, energy saving issues also apply to them. There is often a need to reduce the brightness of the glow. LED lamps with conventional dimmers do not work and quickly break down during regulation. For this, special regulators of two types are used: changing the supply voltage, controlling by the method of pulse-width modulation - PWM (load switching intervals).

Devices with dimming by changing the voltage are expensive and bulky (rheostat or potentiometer). At the same time, they do not fit well with low-voltage lamps and turn on only at 9V and 18V.

A modern regulator is a complex device that provides a smooth start of lamps, brightness control and setting the light switching modes by timer.

The LED lamp differs from conventional tapes and assemblies, which can only be connected using additional devices. Its main features are as follows:

1. Availability of standard plinths types E, G, MR for connection.
2. The ability to work with a network without additional devices. If the lamp is powered by 12V, auxiliary devices are specified in its characteristics.
3. The luminous flux generated should not differ significantly from the standard values.

To ensure the required mode of operation, a driver is built inside the lamp, which performs useful functions. If it provides for dimming, it is said in the passport and on the packaging. In this case, the brightness of such lamps can be adjusted using conventional controls.

If dimming is not provided, you should purchase special control devices with PWM control. They differ in the types of installation:

• modular (in distribution boards) controlled by external regulators, remote controls or by special buses;
• located in an installation box, like a switch, with rotary or push-button control;
• remote blocks mounted in ceiling structures (for spotlights and LED strips).

PWM-based regulators operate on expensive microcontrollers that cannot be repaired. It is easier to make a homemade device based on a simple microcircuit. The dimmer made on the basis of the NE555 timer works stably at a voltage of 3-18 V with an output current of up to 0.2 A.

Dimmer circuit for LED lamps

The oscillation frequency is provided by a generator consisting of a resistor and a capacitor. By the value of the variable resistor, you can set the interval for turning on and off the load at the output 3 of the microcircuit. The field-effect transistor here serves as a power amplifier, since the microcircuit cannot cope with the load from the LED lamps. If the current through them exceeds 1A, a cooling radiator is required for the transistor.

For fluorescent lamps

The brightness of the lamps can be controlled using electronic ballasts, which perform the main function of starting them. A simple diagram is shown in Fig. below.

Controlling a fluorescent lamp using an electronic ballast

The voltage is supplied to the lamp from a frequency generator of 20-50 kHz. The circuit formed by the capacitor and the choke enters into resonance and ignites the lamp. To change the current and thus the intensity of the light, you need to change the frequency. Dimming is done only after the lamp reaches full power.

The adjustable electronic ballast is created on the basis of the IRS2530D controller with 8 outputs. The device is a 600V half-bridge driver with trigger, dimming and anti-failure functions. The integrated circuit allows you to implement all the necessary control methods through 8 pins and is used in many ways to change the brightness of lamps.

Block diagram of electronic control of fluorescent lamps

Choice. Video

It is better to learn about the right choice of dimmers from the video in advance.

When buying a dimmer, you should carefully study its technical characteristics and determine what types of lamps it is intended for. The correct choice of the device makes it easy to connect it yourself without the help of specialists.

NOTE!

We have connected the ground of the LED and variable resistor (potentiometer) to the long rail “-” of the breadboard, and have already connected it to the GND input of the microcontroller. This way we used fewer inputs and less wires stretch from the breadboard to the controller.

Signs "+" and "-" on the layout do not oblige you to use them strictly for power supply, it is just that most often they are used this way and the marking helps us.

It does not matter which of the extreme legs of the potentiometer will be connected to 5 V, and which to GND, only the direction in which you need to turn the knob to increase the voltage will change. Remember that we read the signal from the middle leg.

To read an analog signal that accepts a wide range of values, and not just 0 or 1 like digital, only the ports marked on the board as "ANALOG IN" and numbered with the A prefix are suitable. For Arduino Uno, this is A0-A5.

SKETCH

COMMENTS ON THE CODE

Using the #define directive, we told the compiler to replace the POT_PIN identifier with A0 - the number of the analog input. You may come across a code where an analog port will be addressed by a number without an A index. This code will work, but use an index to avoid confusion with digital ports.

Variables are usually given names starting with a lowercase letter. To use a variable, you need to declare it, which we do with the instruction:

To declare a variable, you must specify its type, here - int (from the English integer) - an integer value in the range from -32 768 to 32 767, we will get acquainted with other types later.

Variables of the same type can be declared in one statement, listing them separated by commas, which we did.

The analogRead (pinA) function returns an integer value in the range from 0 to 1023, proportional to the voltage applied to the analog input, the number of which we pass to the function as the pinA parameter.

Notice how we got the value returned by analogRead (): we just put it in rotation with the assignment operator \u003d, which writes what's to the right of it to the variable to the left.

QUESTIONS FOR SELF-TEST

1. When assembling the circuit, can we connect the LED and the potentiometer directly to different GND inputs of the microcontroller?

2. In which direction do you need to turn the variable resistor to increase the brightness of the LED?

3. What happens if you erase the pinMode (LED_PIN, OUTPUT) line from the program? line pinMode (POT_PIN, INPUT)?

4. Why do we divide the value received from the analog input before setting the LED brightness? what will happen if this is not done?

TASKS

1. Turn off the board power, connect another LED to port 5. Change the code so that the second LED glows at 1/8 of the brightness of the first.

Dimming (from the English dimming - dimming) is a process of controlling the intensity of light, with its roots in the 19th century. For the first time, dimming was used in theaters, when, according to the director's plan, the stage was to be darkened and illuminated depending on the action taking place on it. For this, the arc lamp projectors used at that time were covered with blackout curtains. The more these curtains blocked the light flux, the more they dimmed the lighting. Today's dimmers have gone far from their uncomplicated predecessor, but in general their purpose remains the same.

Brightness control is widely used in modern systems. So, by means of dimming, you can create soft chamber lighting in the living room or bedroom, quickly change the atmosphere in a cafe or restaurant, and enhance visual "magnets" in retail.

Dimming benefits

• Possibility of creating and quickly changing lighting scenarios that are unattainable with standard two-position switches.
• Brightness control allows you to operate lighting devices in a sparing mode, which extends their service life.
• Dimming results in reduced power consumption and heat dissipation.

The widest possibilities for controlling the lighting environment open up when dimming is combined with dividing lighting devices into groups. This approach allows you to control the overall light and accents independently of each other, realizing the most interesting and complex scenarios.

Benefits of dimming LEDs

Adjusting the brightness of the LEDs allows you to fully unleash their full potential. The features of the LED make this lighting element an ideal candidate for dimming.

• The brightness of an LED can be changed over a very wide range, unlike fluorescent lamps.
• Changes in brightness have no effect on color temperature and color rendering, unlike incandescent lamps.
• A decrease in brightness leads to an increase in the service life, and not vice versa, as is the case with halogen lamps.
• The dimming of LED luminaires takes place without delay, which allows them to be used even in the most dynamic lighting scenarios.

Features of LED dimming

The simplest dimmer, which controls the dimming of incandescent lamps, does this by "cutting" the AC sinusoid. But unlike incandescent lamps, LED luminaires have a more complex device and operate under the control of an electronic circuit - a driver. Thus, the correct operation of the lighting equipment directly depends on the driver that controls it. At the same time, by choosing the right driver, you can dim absolutely any lamps, regardless of their power and type.

Dimming Standards and Protocols

TRIAC

Triac dimmer with phase cutoff. Its main advantages are its low price and the ability to be built into a circuit without unnecessary commutation (like a switch). For correct dimming of the LEDs, it is important to check the compatibility of the equipment (dimmer-driver bundles). This will avoid unwanted hum and flickering during operation.

1-10V

The standard that gained wide popularity in the era of widespread use of fluorescent lamps. Its essence lies in sending a signal from 1 to 10V over a separate pair of wires. That is, the dimmer in this case is implemented as an ordinary potentiometer. The main advantage of this approach is complete insensitivity to load. Disadvantages include the inability to control the light source from multiple locations and poor support from LED manufacturers.

DALI

A digital protocol supported by most professional lighting manufacturers. Its main advantage is a digital bus that integrates all dimmable LED luminaires into a single system. Switching on, off and dimming are carried out by signal commands, and not by opening the supply circuit. This approach allows you to reassign at any time which switch is responsible for which luminaire.

But the most important advantage of the digital DALI protocol is the ability to program scenes and store them in memory. This completely redefines lighting control. A conventional switch key can now not only control the luminaire, but set the operating mode for the whole group.

Among the disadvantages of the DALI protocol, one can single out only the high cost and the need for preliminary configuration of the control system.

Push DIM

An interesting type of dimming in implementation, which allows you to use only two wires for connection. Buttons with normally open contacts serve as control elements. As long as you hold the button, there is a signal, let go - there is no signal. Lighting devices will perceive such clicks as follows:

• short: on / off;
• long: adjust the brightness.

The method is simple to implement, does not require additional settings and can be implemented with almost any electrical fittings. But there are also disadvantages: the low prevalence of drivers with such a standard and a limited number of lamps connected to one button.

Driver selection

The choice of driver and type of dimming is determined by many factors. They are the most flexible in this regard, since their driver is taken out of the case. In the case of a large number of nuances have to be taken into account. However, there are no unsolvable problems. Enlisting the support of qualified specialists, you can even dim those lamps that were not originally designed for this.