One disclosed example provides a high-power switch circuit, comprising a cathode and an anode. One or more of the cathode and the anode comprises a three-dimensional graphene network. The high-power switch circuit further comprising a gap separating the cathode and the anode, a high-power voltage source electrically connected to the cathode and the anode, and a trigger device configured to selectively control triggering of an electrical current between the cathode and the anode.

A method of controlling electrical power delivery to a well tool can include transmitting trigger light via an optical waveguide to a circuit in a well, and the circuit delivering the electrical power to the well tool in response to the circuit receiving the trigger light. A circuit for supplying electrical power to at least one well tool can include a photodiode which receives light from an optical waveguide in a well, a voltage increaser which increases a voltage output by the photodiode, and an electrical energy storage device which receives electrical energy via the voltage increaser, whereby the electrical power can be supplied to the downhole well tool from the storage device.

A method of controlling electrical power delivery to a well tool can include transmitting trigger light via an optical waveguide to a circuit in a well, and the circuit delivering the electrical power to the well tool in response to the circuit receiving the trigger light. A circuit for supplying electrical power to at least one well tool can include a photodiode which receives light from an optical waveguide in a well, a voltage increaser which increases a voltage output by the photodiode, and an electrical energy storage device which receives electrical energy via the voltage increaser, whereby the electrical power can be supplied to the downhole well tool from the storage device.

One disclosed example provides a high-power switch circuit, comprising a cathode and an anode. One or more of the cathode and the anode comprises a three-dimensional graphene network. The high-power switch circuit further comprising a gap separating the cathode and the anode, a high-power voltage source electrically connected to the cathode and the anode, and a trigger device configured to selectively control triggering of an electrical current between the cathode and the anode.