Switch controller circuit (10) for controlling switching in a topology (1) having a first switch (4), a second switch (5), and a switching node (6) coupled therebetween. A driver arrangement (101,104,105) controls the first and second switches (4,5) to alternately open and close, wherein a deadtime period is applied between the opening of one switch (4) and the closing of the other switch (5) in use. A voltage sensor (106) connected to the switching node (6) provides feedback based on a sensed voltage as it transitions between high and low voltage states and sets a length of the deadtime period based on a measured first time period and a multiplier coefficient. The first time period is measured from a time of opening of one of the switches to a time when the sensed voltage transitions through a threshold set between the high and low voltage states.