A current control circuit for a power converter to control the switching thereof, wherein the current control circuit comprises: a digital controller using a logical input signal to produce a logical control signal with a fixed fundamental frequency for the power converter; and a current measurement device for measuring the current in the power converter (Imes), wherein said circuit is operable to compare said current in the power converter to a current reference (Iref) to determine a current error value (lerr), which current error value causes the generation of the logical control signal from the digital controller; and wherein said digital controller is arranged to control said power converter such that said current in the power converter has a profile comprising a rising slope and a falling slope within a single clock period and said digital controller is arranged to attempt to centre said falling slope on said current reference, by: storing a first time interval between a first time defined by a regular clock edge and a second time defined by a crossing of said rising slope and said current reference; determining a second time interval from said first time interval, said clock period and a crossing factor, as measured in the preceding clock cycle; said second time interval for determining the time at which said logical control signal causes said current in the power converter to transition from a rising slope to a falling slope, said third time period being delimited by said second time and the time of said transition; determining the crossing factor from the ratio of the second time interval and a third time interval, said third time interval being delineated by the end of the second time interval and a subsequent time defined by the next crossing of said falling slope and said current reference; and determining the logical control signal from the crossing factor. a digital controller using a logical input signal to produce a logical control signal with a fixed fundamental frequency for the power converter; and a current measurement device for measuring the current in the power converter (Imes), wherein said circuit is operable to compare said current in the power converter to a current reference (Iref) to determine a current error value (lerr), which current error value causes the generation of the logical control signal from the digital controller; and wherein said digital controller is arranged to control said power converter such that said current in the power converter has a profile comprising a rising slope and a falling slope within a single clock period and said digital controller is arranged to attempt to centre said falling slope on said current reference, by: storing a first time interval between a first time defined by a regular clock edge and a second time defined by a crossing of said rising slope and said current reference; determining a second time interval from said first time interval, said clock period and a crossing factor, as measured in the preceding clock cycle; said second time interval for determining the time at which said logical control signal causes said current in the power converter to transition from a rising slope to a falling slope, said third time period being delimited by said second time and the time of said transition; determining the crossing factor from the ratio of the second time interval and a third time interval, said third time interval being delineated by the end of the second time interval and a subsequent time defined by the next crossing of said falling slope and said current reference; and determining the logical control signal from the crossing factor. storing a first time interval between a first time defined by a regular clock edge and a second time defined by a crossing of said rising slope and said current reference; determining a second time interval from said first time interval, said clock period and a crossing factor, as measured in the preceding clock cycle; said second time interval for determining the time at which said logical control signal causes said current in the power converter to transition from a rising slope to a falling slope, said third time period being delimited by said second time and the time of said transition; determining the crossing factor from the ratio of the second time interval and a third time interval, said third time interval being delineated by the end of the second time interval and a subsequent time defined by the next crossing of said falling slope and said current reference; and determining the logical control signal from the crossing factor.