A controller circuit for the control of a power converter is disclosed. An example controller circuit generates a waveform that drives a switch that controls the power converter. The controller circuit includes a divider module that generates a modification factor based on a ratio of the two input signals of the module. The circuit includes a module that generates a first waveform configured for a critical conducting mode of operation of a power converter and an on-time adjuster module that modifies the first waveform based on the modification factor and generates a second waveform. The second waveform is delivered to the switch. An example modification factor is the ratio of the output voltage to the rectified input voltage of the power converter.