A fault-tolerant controller for a lighting system comprising: a plurality of light emitting diode (LED) circuits and a controllable power source to power the plurality of LED circuits. The controller comprising a minimum voltage selector to determine a minimum voltage from a plurality of feedback voltages, one feedback voltage for each of the plurality of LED circuits. A control logic to regulate the drive voltage for the LEDs; and an overvoltage warning mechanism to determine an overvoltage of the drive voltage. The controller identifies one or more open-circuit conditions, one for each LED circuit, for which the respective feedback voltage is below an open-circuit threshold, and which causes the minimum voltage selector to exclude one or more respective feedback voltages associated with the LED circuits which have an open-circuit condition.