Digital Systems

Technical application guide

DALI dimming curves (power consumption depending on dimming level)

DALI dimming curves

IEC 62386 defines the dimming range of a DALI controller from 0.1 to 100 %. The dependance of the relative luminous fl ux X (n) on the digital 8-bit DALI value n is described by the following correlation:

This results in the following graphical association:

  • Logarithmic curve (factory setting) used for standard applications (e.g. daylight control)
  • LED drivers according to IEC 62386-207 and other drivers such as OTi DALI additionally provide a linear dimming curve, which is only used in special cases, particularly for easier adjustment of RGB colors in RGB dimming applications

Switching between the curves is possible with Tuner4TRONIC, DALI Wizard or other tools.

The arc power means the relative wattage to the LED module and, in first estimation, the relative luminous flux. In principle, the DALI standard defines 0.1 % as the lowest relative luminous flux, which corresponds to the relative DALI value 1. Not all DALI drivers start at 0.1 % of the relative luminous flux. For many drivers, the smallest value is 1 %, which corresponds to DALI value 85. For each driver, the smallest light output level is the minimum physical level. A light output level lower than the minimum physical level but greater than 0 is interpreted as the smallest light output level. To ensure that the transitions from one digital level to the next are not visible, OSRAM DALI drivers feature digital “smoothing”. This is an additional function of OTi and QTi drivers for increasing lighting comfort and is not part of the DALI standard.

System energy consumption and dimmer setting

Because there is a largely linear relationship between the power consumption of the DALI/DIM systems (LED module and driver) and the dimmer setting, the power consumption PN(d) can be calculated for each dimmer setting d (in percent) based on the values PN100% (100 % of nominal power, PN = Power Nominal) and PN1% (1 % of nominal power):

Linear correlation: Dimming level and system power consumption

Constant lumen programming graph (operating time = 10 kh)

Dimming range and lowest dimming level of a DALI LED driver

For the permitted dimming range and the lowest dimming level of a DALI LED driver, please refer to the corresponding product datasheets. CLO (Constant Lumen Output) function The CLO function can be used to compensate the lumen decrease over the lifetime of the LED. To achieve a constant light output of the LED module, the LED driver can store the operating hours of the LED module and increase the output current to react on the light output drop. The benefits are:

  • Energy and cost savings
  • Longer lifetime of the LED module
  • Same light output und same light color over the lifetime of the luminaire
  • Better maintenance due to group change of LED modules

To set this feature according to the applied LED module, the Tuner4TRONIC software can be used, for example, as shown in the figures below.

The output levels have to be monotonically increasing from the beginning.

Warning: The output level is indicated as a red number if the level is set higher than 100 %. In this case, the reliability and safety of the module needs to be checked if the nominal operating current is exceeded. It is not possible to achieve a higher output current than the maximum nominal output current of the LED driver.

Lamp operating counter

The LED driver monitors the operating hours of the connected LED module. Operating hours are only counted when the LED module is powered. The lamp operating time also has an influence on the CLO function. It can be set using the Tuner4TRONIC software as shown in the figure below.