Abstract: An electronic circuit for operating a High Intensity Discharge (HID) lamp, in particular a Ultra High Pressure (UHP) lamp, such as those preferably used in image projectors. The circuit comprises a lamp ballast for offering a controlled lamp current for operating the HID lamp and a brightness sensor for generating and providing a sensor signal which represents the brightness of the light applied by the lamp to the image generator. The lamp ballast controls the lamp current such that the brightness of the light of the lamp remains constant. Brightness control is made possible throughout the entire operational life of the lamp, and the use of sensors of simple construction is made possible by an incorporation within the electric circuit of a filter that high-pass filters the sensor signal before it is supplied as a control signal to the lamp ballast.

Abstract: The invention relates to a DC—DC converter and a power supply unit formed thereby, with which a DC input voltage (Vdc) may be converted into two DC output voltages (U1, Usb) via a resonant switched-mode power supply. Via a circuit stage (M1, M2), a control circuit (C) generates a first AC voltage (VAC), which is converted via two resonant circuits with different transmission behavior and two rectifiers (G1, Gsb) in frequency-dependent manner into DC output voltages (U1, Usb). To achieve a standby mode, in which the first DC output voltage (U1) is designed to be very low and hardly any power is drawn on the output side, a second, thinner auxiliary circuit stage (M3, M4) is provided, which is coupled to the resonant circuits via an inductor (L2). The current consumption of the circuit in standby mode may be reduced considerably by appropriate dimensioning.

Abstract: The invention relates to an electronic circuit for operating a High Intensity Discharge (HID) lamp, in particular a Ultra High Pressure (UHP) lamp, such as those preferably used in image projectors. The circuit comprises a lamp ballast 110 for offering a controlled lamp current for operating the HID lamp 422 and a brightness sensor 130 for generating and providing a sensor signal which represents the brightness of the light applied by the lamp to the image generator. The lamp ballast 110 controls the lamp current such that the brightness of the light of the lamp remains constant. It is an object of the invention to develop the electronic circuit and the image projector further such that the brightness control is made possible throughout the entire operational life of the lamp 322, and the use of sensors of simple construction, and thus less expensive sensors, is made possible.

Abstract: The invention relates to a standby circuit, an electrical device with a standby circuit, a method for the control of the electrical device and a power supply assembly. Whereas the power supply unit and the control electronics are in permanent operation when conventional devices are in the standby mode and consequently have a high power consumption, the invention proposes a solution for saving energy while retaining convenience of operation by which the power supply unit is switched off in the standby mode. A standby circuit, preferably fed by an energy buffer element, remains active in the standby mode and monitors signal inputs for activation events. When an activation event occurs, the standby circuit switches on the power supply unit.

Abstract: The invention relates to a DC-DC converter and a power supply unit formed thereby, with which a DC input voltage (Vdc) may be converted into two DC output voltages (U1, Usb) via a resonant switched-mode power supply. Via a circuit stage (M1, M2), a control circuit (C) generates a first AC voltage (VAC), which is converted via two resonant circuits with different transmission behavior and two rectifiers (G1, Gsb) in frequency-dependent manner into DC output voltages (U1, Usb). To achieve a standby mode, in which the first DC output voltage (U1) is designed to be very low and hardly any power is drawn on the output side, a second, thinner auxiliary circuit stage (M3, M4) is provided, which is coupled to the resonant circuits via an inductor (L2). The current consumption of the circuit in standby mode may be reduced considerably by appropriate dimensioning.