Electronic control units in vehicles with LED headlamps

Useful knowledge and valuable tips on the subject of electronic control units in modern vehicles with LED headlamps.

The digitalisation of headlamp systems and a steadily increasing technological complexity of variable functionalities lead to ever higher demands on lighting electronics. The targeted control of individual LEDs enables optimum light distribution and luminous intensity, providing the driver with the best possible visibility on the road in every situation. Furthermore, the precise control avoids disturbing other road users in the vicinity.

Important safety note
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their work. The information provided on this website is intended for use by suitably qualified personnel only.


Design and function of electronic control units in modern vehicles with LED headlamps: Design

In addition to the already familiar LED technologies such as daytime running light, position light, tail light or direction indicator light, the headlamp functions of low beam and high beam have now also established themselves in LED design in the vehicle exterior lighting. Additional control units are necessary to ensure these functions.

The main task of these so-called light control units is to control and monitor the individual light functions of the headlamp. In addition to the central control of all lighting functions, additional coordination tasks such as the dynamic adjustment of light distribution in adaptive lighting systems are also carried out individually and adjusted to the respective driving situation. In vehicles with Highbeam Assist, the control units linked in the system manage the control of the individual LEDs per headlamp according to the situation and demand. Thus, the light intensity is regulated individually.

The latest generation of headlamps, such as those in the VW Touareg, the Audi A8 or the Audi A7, are increasingly controlled by software.

Depending on the vehicle and system, several different types of control units can be used. The control units are usually mounted directly on the headlamp housing.


The following functionalities are implemented with this control unit:

  • Power supply for low beam, high beam and daytime running lights
  • Power supply of the internal periphery with +5 V and +12 V (three voltage transformers)
  • Direction recognition right/left
  • Control of additional functions (e.g. dynamic cornering light)
  • Control of the fans in the headlamp
  • Integration of up to seven signal inputs for coding temperature or light classes

System integration in the vehicle

In-vehicle communication with additional BUS participants takes place by networking the headlamp control units with the on-board network control unit as well as with the control units of individual driver assistance systems. The light control units communicate via data bus and thus receive necessary information that is permanently and reliably converted into the required light distribution. Any system errors that occur are detected and stored in the error memory of the higher-level control units.