Abstract: An LED driver has outputs to drive LEDs in groups of different colour temperatures. An input is configured to receive setpoint information, and a control device is configured to determine a combined LED setpoint intensity for the groups and a combined LED setpoint colour temperature for the groups, from the LED setpoint information. If the LED setpoint intensity is above a threshold, the control device operates the LED driver outputs to mix the LED group outputs to jointly achieve the LED setpoint intensity and the LED setpoint colour temperature. If the LED setpoint intensity is below the threshold, the control device selects a single LED group, operates the LED driver output associated with the selected LED group to drive that one LED group at the LED setpoint intensity, and operates the remaining LED driver outputs to drive the remaining LED groups at zero LED intensity.