An emulator circuit for forming a signal representative of current flow in an inductor of a switched mode power supply, where the inductor is associated with a switching arrangement operational to connect a first node of the inductor to a first voltage (Vin) or to one of a reference voltage (gnd) or a current flow path, a second node of the inductor to a second voltage (Vout) or to one of a second reference voltage (gnd) or the current flow path, and wherein the emulator circuit forms a emulator output signal representing the integral with respect to time for which the first and second node of the inductor are connected to the first voltage and the second voltage respectively.