Dimmer for LED systems: techniques and characteristics – Sicom Testing

Thanks to the ever-increasing attention paid to the environment, pollution and energy saving, the use of LED technologies - in housing solutions, public and private structures - presents itself as a dominant reality in terms of diffusion and advantages.

Among the key values that make this system an effective option, we find the long lifespan - with little need for maintenance - of the components; great energy savings and excellent environmental protection, both in terms of emissions of UV and IR rays and in relation to toxicity some materials.

In terms of design, however, the modularity and the adaptability to the most varied creative solutions are characterized as characteristics that make LED technologies even more attractive, alongside a fundamental possibility: that of regulating the intensity of the luminous flux.

As is known, in fact, a light dimmer regulates the luminous intensity of a LED from 0% to 100%, insisting on pulse width modulation or using digital regulation systems.

Using a dimmer: the strengths

Thanks to the use of these devices, great advantages are obtained in terms of use and consumption, such as:

the possibility of adapting the intensity of light in an environment depending on the activity being carried out, avoiding an insufficient or excessive light supply for our visual capacity;
the increase in the efficiency and life of the lamps, guaranteed by the reduction of the operating temperature, to which the long lifespan is generally correlated;
the increase in energy savings, correlated to the increase in efficiency and durability of the appliances.

It is therefore fundamental to know how to associate the right dimming device to the lighting system that has been chosen, taking into account the objective, but also the types and functions.

DIMMING AND PWM TECHNOLOGY

The PWM system (Pulse-Width Modulation) – certainly among the most used – involves the variation in frequency from hundreds of cycles per second to hundreds of thousands of cycles per second, a factor that modifies the quantity of light emitted.

This is dimming energy efficient because the transistor is in the condition of conducting completely or not at all, in a context of minimum absorbed power. The problem with PWM dimming lies in the fact that - through the series of switching on and off, the classic "flickering" effect perceptible to the human eye can be generated.

DIMMING VIA TRIAC

With Triode Alternating Current dimming the current is conducted in both directions, alternately, at a variable speed. This makes the light turn on and off faster than with PWM dimming. This system can, in fact, reduce the lifespan of LEDs, but - generally - it does not create the conditions under which the human eye can perceive a flickering light.

The Triac dimmer, like the PWM one, requires that the range of voltage to vary, which is found in the formula 0-10 Volts the most used version.

TECHNICAL-REGULATORY REFLECTIONS

For this type of products, in addition to the aspects of certification of lighting components, the constraints imposed by the regulations for electrical systems in buildings must also be considered.

In the past, voltage variators - used with filament and halogen lights - were located in place of the switch but - with low consumption lamps and LED lights which have their own power supply - this solution is no longer viable, since normally it is not possible to insert a variator before the switch itself.

The scenario of the most well-known techniques, therefore, includes the possibility of acting on the power supply with a radio control (placing the receiving control unit between the power supply and the LED and associating the radio control itself) and the 0-10 Volt technique, of which we want to highlight some regulatory aspects.

In fact, with the 0-10 Volt technique, the system is given a voltage between 0 and 10 Volts thanks to an additional electrical regulation connection. This dynamic poses problems of precept, because - being a low voltage signal – this should not be run together with dangerous voltage cables, for example, 230 Volt cables.

To stem this condition, there is a more complex, but certainly viable, solution. In fact, some are being planned more complex power supplies, which detect the typical waveform produced by traditional voltage regulators of the past and adjust the brightness of the LEDs accordingly. In this way you can use the same scheme as in the past using current light sources. It is tempting to use old voltage regulators near the switch, but this is normally not possible because the consumption of current LED lights is too low. You must use special regulator modules that also work well with less power.

Although the system may appear a little complex, it is the most practicable and widespread, but it is also the most convenient in terms of costs: regulator and power supply, in fact, cost around 3 times as much as a LED ceiling light, but it is still the cheapest solution Compared to others. Above all - key factors in terms of safety and correctness of the technology - it is a system that does not present regulatory problems and does not require the passage of any additional cables.

To be sold in Europe, these components must also bear the CE mark like all electrical and electronic equipment, therefore they must follow the procedure certification of lighting components.