How do I choose a smart LED power supply?

Schukat offers tips for setting up an intelligent lighting system

Modern light and building management systems are currently trending. Schukat explains how to find the right smart LED power supply for your application.

The problem

Users today have a wide range of options available to them for setting up an intelligent lighting system. Based on a few criteria, however, deciding on the right LED power supply is easy.

The right standard

Depending on the individual needs of the user, various standards are available, each with advantages and disadvantages:

• Dali/KNX: With its simple data structure, Dali as a pure light-management system is extremely robust and can be set up economically. However, the Dali system is limited to a maximum of 64 devices per Dali line. Using gateways, a Dali installation can also be integrated into a complex building management system, e.g. a KNX system. For direct integration into a KNX system, CC-LED power supplies with an integrated KNX interface are available. The first CV-LED power supplies from producer MEAN WELL are currently being developed.

KNX-Dali gateway (left) and LED power supply with integrated KNX interface (right) from MEAN WELL.

• EnOcean: These wireless solutions offer the advantage of not requiring an external power source. And because EnOcean motion detectors and light sensors generate energy from integrated solar cells, and EnOcean pushbuttons generate their energy from piezo elements, there is no need to change batteries in the components. Gateways to connect to building automation systems are also available for EnOcean wireless solutions. Coupling and parameterisation of the power supplies can be completed easily using on-device pushbuttons or "Navigan" software, as applicable.

CC LED power supply with integrated EnOcean interface

Dimming

For constant-current applications, power supplies with linear dimming are suitable, while for dimming LED strips, we advise a power supply that uses pulse width modulation (PWM) dimming. Negative visual effects like flickering can be minimised by using a PWM frequency of >1.2kHz.

CV Dali power supply with PWM output

Standards and directives

These standards and directives need to be observed:

• Low Voltage Directive 2014/35/EU has been in force since April 2016 – it regulates the safety of electrically driven devices. The applicable safety standards for LED power supplies are EN61347-1 and EN61347-2-13.

• Since April 2016, EMC Directive 2014/30/EU has regulated the electromagnetic compatibility of equipment. The applicable EMC standards for LED power supplies include EN55015, EN61000-3-2, EN61000-3-3 and EN61547

• The ''setting of ecodesign requirements for energy-related products'' – including the standby power consumption of LED power supplies – is covered by the Ecodesign Directive 2009/125/EC, in force since 2012.

Load variation for saving energy

Modern LED power supplies allow energy to be saved even in active operation. To maximise savings, the LED power supply should be chosen according to the load. The newest switching power supplies, depending on their output, achieve efficiency of up to 90%. If the load utilisation is too low, however, the efficiency of the power supplies, depending on the circumstances, can suffer. To achieve good efficiency even with dynamic loads, the efficiency-load curve should be as flat as possible.

Temperature and life expectancy

To reduce self-heating, it is advisable to plan for a reserve capacity of approx. 20% - temperature exercises a direct influence on the life expectancy of a power supply.

• Tip: An increase of around 10°C in temperature halves the life expectancy of the power supply. This means that the power supply should be installed as far from sources of heat as possible.

Start-up current

f an automatic circuit breaker monitors a certain number of power supplies, the start-up current of the power supplies needs to be taken into account and the installation designed accordingly. It is therefore also necessary that the rating of the automatic circuit breakers or an intermediate start-up current limiter be able to handle the sum of the start-up currents and their pulse duration

Inrush current limiter series ICL-16R/L for inductive and capacitive loads

Schukat electronic

We offer our customers a wide selection of smart LED power supplies from MEAN WELL. The producer is constantly driving development in this area and produces LED power supplies with digital interfaces for EnOcean, Dali and KNX. The KNX range also includes switching and dimming actuators that allow the integration of analogue LED power supplies into a KNX system. Questions? Our sales team are happy to advise you.