A semiconductor switching circuit (70, 170), for use in a HVDC power converter, comprising: a main current branch including at least one main semiconductor switching element and through which current flows in a first direction (D1s1) when the or each main semiconductor switching element is switched on; an auxiliary current branch connected in parallel with the main current branch, the auxiliary current branch including at least one auxiliary semiconductor switching element (72, 172); and a control unit operatively connected to the or each main semiconductor switching element to control switching of the or each main semiconductor switching element, wherein the control unit is programmed to switch on the or each auxiliary semiconductor switching element (72, 172) in the auxiliary current branch so that an alternative current path via the auxiliary current branch is selectively created so that current (i stray) flowing in the first direction through the main current branch is diverted to flow through the alternative current path so that the rate of change of current (i stray) flowing through the or each main semiconductor switching element is reduced immediately after the or each said main semiconductor switching element is switched on, characterised in that: a gate of one or more auxiliary semiconductor switching elements is at a different potential than that of a gate of the or each main semiconductor switching element; and the control unit is operatively connected via the respective voltage isolation device to the or each auxiliary semiconductor switching element (72, 172) to control switching of the or each auxiliary semiconductor switching element (72, 172), wherein the voltage isolation device permits triggering of the or each auxiliary semiconductor switching element (72, 172) by the same control unit that is used to trigger the or each main semiconductor switching element. a main current branch including at least one main semiconductor switching element and through which current flows in a first direction (D1s1) when the or each main semiconductor switching element is switched on; an auxiliary current branch connected in parallel with the main current branch, the auxiliary current branch including at least one auxiliary semiconductor switching element (72, 172); and a control unit operatively connected to the or each main semiconductor switching element to control switching of the or each main semiconductor switching element, wherein the control unit is programmed to switch on the or each auxiliary semiconductor switching element (72, 172) in the auxiliary current branch so that an alternative current path via the auxiliary current branch is selectively created so that current (i stray) flowing in the first direction through the main current branch is diverted to flow through the alternative current path so that the rate of change of current (i stray) flowing through the or each main semiconductor switching element is reduced immediately after the or each said main semiconductor switching element is switched on, characterised in that: a gate of one or more auxiliary semiconductor switching elements is at a different potential than that of a gate of the or each main semiconductor switching element; and the control unit is operatively connected via the respective voltage isolation device to the or each auxiliary semiconductor switching element (72, 172) to control switching of the or each auxiliary semiconductor switching element (72, 172), wherein the voltage isolation device permits triggering of the or each auxiliary semiconductor switching element (72, 172) by the same control unit that is used to trigger the or each main semiconductor switching element. a gate of one or more auxiliary semiconductor switching elements is at a different potential than that of a gate of the or each main semiconductor switching element; and the control unit is operatively connected via the respective voltage isolation device to the or each auxiliary semiconductor switching element (72, 172) to control switching of the or each auxiliary semiconductor switching element (72, 172), wherein the voltage isolation device permits triggering of the or each auxiliary semiconductor switching element (72, 172) by the same control unit that is used to trigger the or each main semiconductor switching element.