A control circuit operable to generate a control signal to control the duty cycle of a switched mode power supply is provided. The control circuit comprises an input terminal for receiving a signal indicative of an input voltage (Vin) of the switched mode power supply, and a reference signal generator to generate, in dependence upon the received signal, a reference signal (VR) that is a function of the input voltage (Vin). The control circuit further comprises an error signal generator to receive a signal indicative of an output voltage (Vout) of the switched mode power supply and to generate an error signal (VE) based on the reference signal (VR) and based on the output voltage, a low pass filter, and a duty cycle control signal generator to generate the control signal to control the duty cycle of the switched mode power supply in dependence upon the error signal (VE).