A switched mode power supply (100) comprises a reactive element (10) and a control signal generator (30) is arranged to generate a first control signal at a first output (31) of the control signal generator (30) and a second control signal at a second output (32) of the control signal generator (30). The first output (31) of the control signal generator (30) is coupled to a first input (21) of a switching stage (20) by means of a first control signal path (40) and the second output (32) of the control signal generator (30) is coupled to a second input (22) of the switching stage (20) by means of a second control signal path (50). The switching stage (20) is arranged to, responsive to the first and second control signals, alternately charge and discharge the reactive element (10) by coupling it alternately to first and second supply voltages. A delay detector (60) is arranged to generate a delay indicator signal indicative of a relative delay between the first control signal at the first input (21) of the switching stage (20) and the second control signal at the second input (22) of the switching stage (20). An adjustable delay stage (53) in one of the first and second signal paths (40, 50) is arranged to, responsive to the delay indicator signal, control an adjustable delay so that a first delay experienced by the first control signal passing from the first output (31) of the control signal generator (30) to the first input (21) of the switching stage (20) is substantially equal to a second delay experienced by the second control signal passing from the second output (32) of the control signal generator (30) to the second input (22) of the switching stage (20).