Energy harvesting from current loops

A method of harvesting energy from a two-conductor loop in electrical connection with a power source and with a loop current controller, the loop current controller comprising a first port having a first terminal and a second terminal to connect to respective conductors of the two-conductor loop and a second port in operative connection with a sensor, the loop current controller controlling a current in the two-conductor loop to be equal to a current signal to transmit the current signal to a receiver connected to the two-conductor loop, the current in the two-conductor loop being controlled by the loop current controller to be proportional to a signal output from the sensor, comprising:

• electrically connecting an energy harvesting circuit to the two-conductor loop, the energy harvesting circuit comprising a second current controller connected in parallel electrical connection with the loop current controller and a power converter in electrical connection with an output of the second current controller, the second current controller controlling a portion of current drawn from the two-conductor loop and delivered to the power converter from an output port of the second current controller, the portion of the current drawn from the two-conductor loop being less than the current signal into an input port thereof, converting the primary current and a primary voltage to a secondary current and a predetermined secondary voltage to be supplied to at least one load device via the power converter, and returning the portion of the current drawn from the two-conductor loop to the loop current controller from the energy harvesting circuit, wherein noise in the portion of the current drawn from the two-conductor loop by the second current controller is controlled by the second current controller to be below a predetermined threshold so that the loop current controller controls noise in the current in the two-conductor loop to be less than a current corresponding to the resolution of the sensor.

A system comprising a two-conductor loop in electrical connection with a power source and with a loop current controller, the loop current controller comprising a first port having a first terminal and a second terminal to connect to respective conductors of the two-conductor loop and a second port in operative connection with a combustible gas sensor, the loop current controller controlling a current in the two-conductor loop to be equal to a current signal to transmit the current signal to a receiver connected to the two-conductor loop, the current in the two-conductor loop being controlled by the loop current controller to be proportional to a signal output from the combustible gas sensor, the system further comprising energy harvesting circuitry in electrical connection with the two-conductor loop, the energy harvesting circuitry comprising a second current controller in parallel electrical connection with the loop current controller and a power converter in electrical connection with the second current controller, the second current controller drawing a portion of current from the two-conductor loop which is less than the current signal into an input port thereof, the second current controller controlling a portion of current drawn from the two-conductor loop and delivered to the power converter from an output port of the second current controller, the portion of the current drawn from the two-conductor loop being less than the current signal into an input port thereof, the power converter converting a primary current and a primary voltage to a secondary current and a predetermined secondary voltage to be supplied to at least one load device, the portion of the current drawn from the two-conductor loop being returned to the loop current controller from the energy harvesting circuit, wherein noise in the portion of the current drawn from the two-conductor loop by the second current controller is controlled by the second current controller to be below a predetermined threshold so that the loop current controller controls noise in the current in the two-conductor loop to be less than a current corresponding to the resolution of the combustible gas sensor.