Novel LED street lights reduce costs
Researchers of Karlsruhe Institute of Technology (KIT) have developed a novel type of LED street light of increased efficiency. Compared to conventional LEDs, power consumption may be reduced by up to 20%. This will also decrease costs and CO2 emission. Conventional high-power diodes are replaced by a special array of LEDs. This enhances efficiency, increases service life and safety, and produces a better light.
Parallel connection of a large number of LEDs is difficult, as failure of a single diode will cause failure of the overall system or section. According to Michael Heidinger of KIT's Light Technology Institute, the alternative of connecting LEDs in series is also associated with drawbacks, because the voltage required increases with the number of diodes used. As the legally permissible contact voltage is limited to 120 volts, only up to 40 LEDs have been connected in series so far.
Heidinger has now invented an interconnection method that compensates aging and failures of individual LEDs. This method allows to install a large number of LEDs -- 144 in the prototype -- on a single board and to operate the array safely. This new switching concept works with far smaller voltages. "Voltage of the prototype was 20 volts," Heidinger says.