A method of controlling a DC power supply to change a DC offset voltage applied to a component for manipulating charged particles. The method includes, whilst an AC voltage waveform is being applied to the component: controlling the DC power supply to produce an initial DC offset voltage that is applied to the component via a link that causes the DC offset voltage at the component to lag behind the DC offset voltage produced by the DC power supply when the DC offset voltage produced by the DC power supply is changed; then controlling the DC power supply to produce an overdrive DC offset voltage that is applied to the component via the link for a predetermined period of time; then controlling the DC power supply to produce a target DC offset voltage that is applied to the component via the link, wherein the target DC offset voltage is between the initial DC offset voltage and the overdrive DC offset voltage.