An apparatus for delivering power to a load having load circuitry configured to draw power from the apparatus, the apparatus comprising: an isolated power converter configured to convert input power at a primary side of the isolated power converter to output power and a supply voltage at a node on a secondary side of the isolated power converter; on the primary side of the isolated power converter, primary-side control circuitry configured to limit an extent to which the isolated power converter is capable of supplying power for providing the supply voltage at an output; on the secondary side of the isolated power converter, a load switch configured and arranged along a current path between the node and the load having load circuitry configured to draw power from the apparatus; and on the secondary side of the isolated power converter, secondary-side control circuitry configured to receive the supply voltage and to control the load switch to operate in an ON mode in which the current path is used to provide current to the load, and in response to a fault condition corresponding to an effective sudden disconnection of the supply voltage, to switch the load switch into an OFF mode in which the current path to the load is blocked, characterised in that: the secondary-side control circuitry is configured to be powered via the supply voltage and in that when, in said fault condition, the secondary-side control circuitry is disconnected from the supply voltage, another power source at another node (OPTO pin) of the secondary- side control circuitry (106, 232, 354) is configured to be used to power the secondary-side control circuitry to switch the load switch into said OFF mode, and the secondary side of the isolated power converter further includes an opto coupler configured to draw power and charge said another node (OPTO pin) of the secondary-side control circuitry (106, 232, 354) when the load switch is in an ON mode, and in response to the fault condition in which the secondary-side control circuitry is disconnected from the supply voltage, the secondary-side control circuitry is configured to switch the load switch into the OFF mode using the drawn power. an isolated power converter configured to convert input power at a primary side of the isolated power converter to output power and a supply voltage at a node on a secondary side of the isolated power converter; on the primary side of the isolated power converter, primary-side control circuitry configured to limit an extent to which the isolated power converter is capable of supplying power for providing the supply voltage at an output; on the secondary side of the isolated power converter, a load switch configured and arranged along a current path between the node and the load having load circuitry configured to draw power from the apparatus; and on the secondary side of the isolated power converter, secondary-side control circuitry configured to receive the supply voltage and to control the load switch to operate in an ON mode in which the current path is used to provide current to the load, and in response to a fault condition corresponding to an effective sudden disconnection of the supply voltage, to switch the load switch into an OFF mode in which the current path to the load is blocked, characterised in that: the secondary-side control circuitry is configured to be powered via the supply voltage and in that when, in said fault condition, the secondary-side control circuitry is disconnected from the supply voltage, another power source at another node (OPTO pin) of the secondary- side control circuitry (106, 232, 354) is configured to be used to power the secondary-side control circuitry to switch the load switch into said OFF mode, and the secondary side of the isolated power converter further includes an opto coupler configured to draw power and charge said another node (OPTO pin) of the secondary-side control circuitry (106, 232, 354) when the load switch is in an ON mode, and in response to the fault condition in which the secondary-side control circuitry is disconnected from the supply voltage, the secondary-side control circuitry is configured to switch the load switch into the OFF mode using the drawn power. the secondary-side control circuitry is configured to be powered via the supply voltage and in that when, in said fault condition, the secondary-side control circuitry is disconnected from the supply voltage, another power source at another node (OPTO pin) of the secondary- side control circuitry (106, 232, 354) is configured to be used to power the secondary-side control circuitry to switch the load switch into said OFF mode, and the secondary side of the isolated power converter further includes an opto coupler configured to draw power and charge said another node (OPTO pin) of the secondary-side control circuitry (106, 232, 354) when the load switch is in an ON mode, and in response to the fault condition in which the secondary-side control circuitry is disconnected from the supply voltage, the secondary-side control circuitry is configured to switch the load switch into the OFF mode using the drawn power.