A gate control circuit comprising: a main gate unit arranged to supply, via a plurality of main gate unit outputs (30a-f), a gate signal to respective gates of a plurality of parallel power switches (20a-f) of a main circuit, for controlling switching of the power switches; an auxiliary gate unit comprising an optical power converter for converting incoming optical power to an auxiliary electrical gate signal and arranged to, when a short-circuit failure occurs in one of the plurality of power switches, provide the auxiliary electrical gate signal to respective gates of any of the plurality of power switches (20a-f) still being in operation; a plurality of gate switches (25a-f) for preventing the provision of the auxiliary electrical gate signal to the respective gates of any switches no longer being in operation, and a gate supervisor connected to the plurality of gate switches (25a-f), the gate supervisor being arranged to disconnect the gate switch connected to a gate for which the gate supervisor detects a gate voltage drop below a threshold voltage due to a power switch failure, wherein the auxiliary gate unit comprises a plurality of auxiliary gate unit resistors (16a-f) provided between the optical power converter and respective outputs for each of the plurality of power switches (20a-f), each one of the plurality of auxiliary gate unit resistors (16a-f) is sufficiently large to keep a gate voltage of operating power switches such that the respective operating power switch conducts, the main gate unit further comprises a plurality of main gate unit resistors (17a-f) respectively connected to each main gate unit output, wherein the resistance of each main gate unit resistor is significantly lower than the resistance of each auxiliary gate unit resistor, and a plurality of output switches (18a-f) connected to the respective gates of the plurality of the parallel power switches (20a-f) and arranged to assume a blocking state when a failure has occurred in one power switch (20a-f). a main gate unit arranged to supply, via a plurality of main gate unit outputs (30a-f), a gate signal to respective gates of a plurality of parallel power switches (20a-f) of a main circuit, for controlling switching of the power switches; an auxiliary gate unit comprising an optical power converter for converting incoming optical power to an auxiliary electrical gate signal and arranged to, when a short-circuit failure occurs in one of the plurality of power switches, provide the auxiliary electrical gate signal to respective gates of any of the plurality of power switches (20a-f) still being in operation; a plurality of gate switches (25a-f) for preventing the provision of the auxiliary electrical gate signal to the respective gates of any switches no longer being in operation, and a gate supervisor connected to the plurality of gate switches (25a-f), the gate supervisor being arranged to disconnect the gate switch connected to a gate for which the gate supervisor detects a gate voltage drop below a threshold voltage due to a power switch failure, wherein the auxiliary gate unit comprises a plurality of auxiliary gate unit resistors (16a-f) provided between the optical power converter and respective outputs for each of the plurality of power switches (20a-f), each one of the plurality of auxiliary gate unit resistors (16a-f) is sufficiently large to keep a gate voltage of operating power switches such that the respective operating power switch conducts, the main gate unit further comprises a plurality of main gate unit resistors (17a-f) respectively connected to each main gate unit output, wherein the resistance of each main gate unit resistor is significantly lower than the resistance of each auxiliary gate unit resistor, and a plurality of output switches (18a-f) connected to the respective gates of the plurality of the parallel power switches (20a-f) and arranged to assume a blocking state when a failure has occurred in one power switch (20a-f).