Buck converter with inductor pre-energizing

Circuits and methods to achieve a buck-boost converter, capable to achieve a constant output voltage by pre-charging of an inductor if the input voltage is close to the output voltage has been achieved. The prior art problem of output voltage variations occurring while the input voltage is close to the output voltage is avoided. In case the input voltage is lower than a defined threshold voltage or the duty cycle exceeds a defined maximum allowable level, the inductor of the converter is pre-charged followed by boosting of the energy of the inductor to the output of the converter. In both modes the control loops of the buck converter can be used for buck duty cycle control. The duration of the pre-charge depends upon the level of the input voltage, the lower the input level is the longer is the pre-charge performed.