Abstract: A lighting unit is described which has a discharge lamp (1), in particular a high pressure or high intensity discharge (HID) lamp or an ultra high performance (UHP) lamp, a lamp driver (2) and a cooling device (3). To reduce mechanical stresses caused by temperature variations in the lamp (1), one or more operating parameters of the lamp (1) are detected. In addition, a control unit is provided for controlling the lamp driver (2) and/or the cooling device (3) at least during switching on and/or off of the lighting unit in such a way that there is no excursion from a predetermined range of the at least one operating parameter. By selecting the parameter range suitably, the service life of the lamp may be extended considerably or the power of the lamp may be increased while the service life remains the same.

Abstract: A cooling unit (2) having a pump (20) for generating an airflow is provided for cooling a High Power lamp (10) during operation. The value of the airflow is controlled by a control unit (3) which comprises a driver (30) for determining a required value of the airflow on the basis of the operating power of the lamp (10). The control unit (3) comprises two pressure sensors (32, 33) for measuring a pressure of the airflow as well as a pressure drop of the airflow across an orifice (31). The driver (30) is designed for processing the measuring results in order to determine an actual value of the airflow. The value of the airflow is accurately controlled by adjustment of the power supply to the pump (20) in order to obtain a match of the actual value of the airflow and the required value of the airflow.