A light unit driver system comprising: - a light unit driver comprising a plurality of light unit driver channels, each light unit driver channel comprising a switching type converter comprising an inductor, - a supply rail that is connected to respective power inputs of the light unit driver channels to conduct electrical energy to the light unit driver channels, - a backup energy storage configured for storing electrical energy, - a control device for controlling the light unit driver, wherein each light unit driver channel comprises a respective light unit driver channel output, each light unit driver channel being configured for driving a respective light unit via the respective light unit driver channel output of the light unit driver channel, wherein the backup energy storage is electrically connected to the light unit driver channel output of one of the light unit driver channels to be charged via the light unit driver channel output of the one of the light unit driver channels, the light units being connected to the light unit driver channel outputs of the remaining light unit driver channels, wherein the one of the light unit driver channels, of which the light unit driver channel output is connected to the backup energy storage, is operable to conduct energy back from its light unit driver channel output to the supply rail, and wherein the control device is configured to: - in an operational mode, operate the one of the light unit driver channels to charge the backup energy storage via the one of the light unit driver channel outputs to which the backup energy storage is connected, and operate the remaining light unit driver channels to drive the light units, and - in an emergency mode, operate the one of the light unit driver channels to feed energy back from the backup energy storage, via the light unit driver channel output of the one of the light unit driver channels, to the supply rail, and operate the remaining light unit driver channels to drive the light units powered via the one of the light unit driver channels from the backup energy storage. - a light unit driver comprising a plurality of light unit driver channels, each light unit driver channel comprising a switching type converter comprising an inductor, - a supply rail that is connected to respective power inputs of the light unit driver channels to conduct electrical energy to the light unit driver channels, - a backup energy storage configured for storing electrical energy, - a control device for controlling the light unit driver, - in an operational mode, operate the one of the light unit driver channels to charge the backup energy storage via the one of the light unit driver channel outputs to which the backup energy storage is connected, and operate the remaining light unit driver channels to drive the light units, and - in an emergency mode, operate the one of the light unit driver channels to feed energy back from the backup energy storage, via the light unit driver channel output of the one of the light unit driver channels, to the supply rail, and operate the remaining light unit driver channels to drive the light units powered via the one of the light unit driver channels from the backup energy storage. <EOS>