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.