A light source power supply circuit having multiple output channels, comprising: a front end circuit configured to receive an input voltage and provide a regulated front end direct current voltage; said light source power supply circuit being characterised in that it further comprises: a plurality of voltage converter circuits (106-1, 106-2,... 106-N), each of the voltage converter circuits (106-1, 106-2,... 106-N) in the plurality of voltage converter circuits (106-1, 106-2,... 106-N) being configured to receive the regulated front end DC voltage and provide a separate associated DC output for an associated one of the multiple output channels; a protection switch coupled between the plurality of voltage converter circuits (106-1, 106-2,... 106-N) and the front end circuit, the protection switch having a conducting state to couple the front end DC voltage to the plurality of voltage converter circuits (106-1, 106-2,... 106-N) and a non-conducting state to decouple the front end DC voltage from the plurality of voltage converter circuits (106-1, 106-2,... 106-N); a current sense circuit coupled to the plurality of voltage converter circuits (106-1, 106-2,... 106-N), the current sense circuit comprising a current sensor and a bypass switch coupled in parallel with the current sensor, the bypass switch having a conducting state to shunt current around the current sensor and a non-conducting state to allow current to flow through the current sensor, whereby when the bypass switch is in the non-conducting state a voltage across the current sensor establishes a current sense output representative of current through at least one of the voltage converter circuits (106-1, 106-2,... 106-N) in the plurality of voltage converter circuits (106-1, 106-2,... 106-N); and a controller circuit configured to place the protection switch in the non-conducting state in response to the current sense output, when the current sense output exceeds a predefined threshold; wherein the protection switch is coupled between a low side output or a high side output of the front end circuit and the plurality of voltage converter circuits (106-1, 106-2,... 106-N); wherein the plurality of voltage converter circuits (106-1, 106-2,... 106-N) is a plurality of switching converter circuits, and wherein the current sensor comprises at least one resistor coupled between an output of the front end circuit and each of the switching converter circuits in the plurality of switching converter circuits to sense current through the plurality of switching converter circuits; and wherein the protection switch comprises a transistor having a gate coupled to the controller circuit, a source coupled to the at least one resistor, and a drain coupled to each of the switching converter circuits in the plurality of switching converter circuits. a front end circuit configured to receive an input voltage and provide a regulated front end direct current voltage; a plurality of voltage converter circuits (106-1, 106-2,... 106-N), each of the voltage converter circuits (106-1, 106-2,... 106-N) in the plurality of voltage converter circuits (106-1, 106-2,... 106-N) being configured to receive the regulated front end DC voltage and provide a separate associated DC output for an associated one of the multiple output channels; a protection switch coupled between the plurality of voltage converter circuits (106-1, 106-2,... 106-N) and the front end circuit, the protection switch having a conducting state to couple the front end DC voltage to the plurality of voltage converter circuits (106-1, 106-2,... 106-N) and a non-conducting state to decouple the front end DC voltage from the plurality of voltage converter circuits (106-1, 106-2,... 106-N); a current sense circuit coupled to the plurality of voltage converter circuits (106-1, 106-2,... 106-N), the current sense circuit comprising a current sensor and a bypass switch coupled in parallel with the current sensor, the bypass switch having a conducting state to shunt current around the current sensor and a non-conducting state to allow current to flow through the current sensor, whereby when the bypass switch is in the non-conducting state a voltage across the current sensor establishes a current sense output representative of current through at least one of the voltage converter circuits (106-1, 106-2,... 106-N) in the plurality of voltage converter circuits (106-1, 106-2,... 106-N); and a controller circuit configured to place the protection switch in the non-conducting state in response to the current sense output, when the current sense output exceeds a predefined threshold;