a light source is protected by selectively coupling a shunt path in parallel with the light source , such that current is diverted away from the light source and through the shunt path . a detection circuit detects the current flowing in the shunt path when the shunt path is connected in parallel with the light source . a comparator determines whether the current flowing in the shunt path exceeds a predetermined threshold and , if so , prevents or limits the flow of current when the shunt path is disconnected from being in parallel with the light source . in this way , a current detector is provided for monitoring the flow of current in a shunt path , the current detector being configured to disable or limit the flow of current through a light source when a predetermined threshold is reached . this aspect of the invention has the advantage of enabling the current flowing through a light source to be controlled by monitoring the current in the shunt path rather than the path having the light source , thus enabling the maximum current to be controlled without potentially damaging the light source .