Patent ID: 8848322

Claim:
A gate control circuit comprising: a main gate unit arranged to supply, via a plurality of main gate unit outputs, a gate signal to respective gates of a plurality of parallel power switches 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 still being in operation; a plurality of gate switches 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, 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 provided between the optical power converter and respective outputs for each of the plurality of power switches, each one of the plurality of auxiliary gate unit resistors 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 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 connected to the respective gates of the plurality of the parallel power switches and arranged to assume a blocking state when a failure has occurred in one power switch.