A power conversion system for supplying a load, the power conversion system comprising: a power factor corrective front end comprising: an input inductor configured to receive a rectified mains input voltage, a selection module connected to the input inductor via a switching node (V x), and a multi-level half-bridge stage comprising a plurality of half-bridge stages connected in series, each half-bridge stage comprising a pair of switches connected at a floating switching node (V x1, V x2, V x3, V x4, V x5), whereby each half-bridge floating switching node is connected to one of a plurality of outputs of the selection module; a power combining stage coupled to each half-bridge stage of the power factor corrective front end by way of one of a plurality of parallel bus voltage lines (V L1, V L2, V L3, V L4, V L5) output from said multi-level half-bridge stage, the power combining stage configured to combine power on the plurality of parallel bus voltage lines to output a DC voltage to said load; and a controller configured, in dependence on the rectified mains input voltage, to selectively control one of said half-bridge stages to operate in a half-bridge mode, and control the selection module to connect the switching node with the floating switching node of the selected half-bridge stage to provide a stepped-up voltage on one of the plurality of parallel bus voltage lines, wherein the controller is further configured to control the power combining stage to provide a voltage (V BUS) between each of the plurality of parallel bus voltage lines, wherein the sum (5*V BUS) of the voltages across each of the plurality of parallel bus voltage lines is higher than a peak of the rectified mains input voltage. a power factor corrective front end comprising: an input inductor configured to receive a rectified mains input voltage, a selection module connected to the input inductor via a switching node (V x), and a multi-level half-bridge stage comprising a plurality of half-bridge stages connected in series, each half-bridge stage comprising a pair of switches connected at a floating switching node (V x1, V x2, V x3, V x4, V x5), whereby each half-bridge floating switching node is connected to one of a plurality of outputs of the selection module; a power combining stage coupled to each half-bridge stage of the power factor corrective front end by way of one of a plurality of parallel bus voltage lines (V L1, V L2, V L3, V L4, V L5) output from said multi-level half-bridge stage, the power combining stage configured to combine power on the plurality of parallel bus voltage lines to output a DC voltage to said load; and a controller configured, in dependence on the rectified mains input voltage, to selectively control one of said half-bridge stages to operate in a half-bridge mode, and control the selection module to connect the switching node with the floating switching node of the selected half-bridge stage to provide a stepped-up voltage on one of the plurality of parallel bus voltage lines, wherein the controller is further configured to control the power combining stage to provide a voltage (V BUS) between each of the plurality of parallel bus voltage lines, wherein the sum (5*V BUS) of the voltages across each of the plurality of parallel bus voltage lines is higher than a peak of the rectified mains input voltage.