Digital Systems

Technical application guide

9 Dimming principles

Hybrid dimming

OPTOTRONIC DALI drivers can be dimmed between 100 % and 1 %. In order to cover this wide range, two dimming methods (hybrid dimming) are combined:

  • Dimming by amplitude modulation. The dimming range between 100 % and about 30 % (depending on LED driver) is controlled by adjusting the amplitude of the current. The current value specified for the device corresponds to a dimming level of 100 %. The amplitude of the current is reduced to dim the lighting down.
  • Dimming by Pulse Width Modulation (PWM). The dimming range between about 30 % and 1 % is controlled by pulse width modulation. PMW dimming is beneficial at lower dimming levels as there are no color and brightness differences between the individual LEDs.

The transition between the two dimming methods is seamless.

Picture 1: Hybrid dimming

Phase-cut dimming

Phase-cut dimming is a popular kind of dimming. OPTOTRONIC ECO (OTe) Phase Cut drivers allow LED modules to be dimmed with phase-cut dimmers. Both trailing-edge and leading-edge phase-cut dimmers can be used. An up-to-date list of suitable dimmers can be found in the OSRAM OEM Download Center at

For the integration of phase-cut dimming into DALI dimming installations, the OSRAM HTi DALI 315 DIM dimmer module can be used to dim the OTe Phase Cut drivers. Commands of the DALI interface are converted into the corresponding mains voltage trailing-edge signal.

Picture 2: Driver for phase-cut dimming