A power supply start-up sequencing mechanism for controlling activation of a plurality of power supply circuits with a predetermined timing is disclosed. The mechanism comprises a time value generator arranged to provide a time value signal; and for each of the power supply circuits, a logic circuit arranged to receive the time value signal and from the received signal provide an activation signal to the respective power supply circuit, wherein the respective logic circuit is associated with a start timing value for the respective power supply circuit such that the activation signal is provided when the associated start timing value coincides with the received time value signal. An apparatus comprising such a mechanism, and a method for controlling activation of a plurality of power supply circuits are also disclosed.