Patent attributes
A power supply system for a lighting unit, comprises a driver, a local energy storage device and a converter. The converter implements a first, charging mode, mode by connecting to the output of said driver for diverting at least a part of the driving current from the lighting unit to charge the energy storage device, a second, battery driving, mode by connecting to the lighting unit for converting the local energy storage device power supply to drive the lighting unit, and a third, grid driving, mode to neither charge the energy storage device nor convert the secondary power supply. The converter and the driver are controlled actively and synchronously to maintain the current through the lighting unit when switching the converter between modes.
