A lighting driver for driving a lighting load, comprising: a controlled DC power source adapted to generate a controlled DC output current for supplying the lighting load; a current sensor for sensing the controlled DC output current flowing through the lighting load; and a controller for controlling the controlled DC output current of the controlled DC power source, the controller comprising a voltage sensor for sensing an output voltage delivered by the controlled DC power source, wherein the controller is connected to the current sensor, wherein the controller is adapted to perform: a first, test, mode of operation for determining at least one operating current of the lighting load; and a second, operating mode of operation for controlling the controlled DC power source to generate the controlled DC output current in dependence on the determined at least one operating current, wherein the controller is adapted, in the first mode, to: increase the controlled DC output current delivered by the DC power source gradually thereby delivering a sequence of drive currents to the lighting load; sense the output voltage for each drive current value, and obtain a voltage current relationship therefrom; characterized in that the controller is further adapted to: determine an operating current range from the voltage current relationship; and determine a minimum and a maximum operating current based on the voltage current relationship, wherein the maximum operating current is determined at a level for which the drive current values remain substantially constant with increasing output voltage. a controlled DC power source adapted to generate a controlled DC output current for supplying the lighting load; a current sensor for sensing the controlled DC output current flowing through the lighting load; and a controller for controlling the controlled DC output current of the controlled DC power source, the controller comprising a voltage sensor for sensing an output voltage delivered by the controlled DC power source, wherein the controller is connected to the current sensor, wherein the controller is adapted to perform: a first, test, mode of operation for determining at least one operating current of the lighting load; and a second, operating mode of operation for controlling the controlled DC power source to generate the controlled DC output current in dependence on the determined at least one operating current, wherein the controller is adapted, in the first mode, to: increase the controlled DC output current delivered by the DC power source gradually thereby delivering a sequence of drive currents to the lighting load; sense the output voltage for each drive current value, and obtain a voltage current relationship therefrom; characterized in that the controller is further adapted to: determine an operating current range from the voltage current relationship; and determine a minimum and a maximum operating current based on the voltage current relationship, wherein the maximum operating current is determined at a level for which the drive current values remain substantially constant with increasing output voltage. a first, test, mode of operation for determining at least one operating current of the lighting load; and a second, operating mode of operation for controlling the controlled DC power source to generate the controlled DC output current in dependence on the determined at least one operating current, increase the controlled DC output current delivered by the DC power source gradually thereby delivering a sequence of drive currents to the lighting load; sense the output voltage for each drive current value, and obtain a voltage current relationship therefrom; characterized in that the controller is further adapted to: determine an operating current range from the voltage current relationship; and determine a minimum and a maximum operating current based on the voltage current relationship, wherein the maximum operating current is determined at a level for which the drive current values remain substantially constant with increasing output voltage. determine an operating current range from the voltage current relationship; and determine a minimum and a maximum operating current based on the voltage current relationship, wherein the maximum operating current is determined at a level for which the drive current values remain substantially constant with increasing output voltage.