A LED driver comprises two output contacts (310, 311) and an additional contact (312) which enables detection of connection of the LED driver to a LED module (301). The LED driver has a normal current regulating mode and an open circuit protection voltage regulating mode. The LED driver is switched from the voltage regulating mode to the current regulating mode in response to the detection of connection of the LED module. This enables a LED module to be connected to the LED driver while it remains powered, in particular because the LED driver is placed in a voltage regulating mode prior to connection to the LED module.