Control of hysteretic current mode multilevel buck converter

An apparatus, comprising:

• a multilevel power converter including a controller, four transistors in a series arrangement, a flying capacitor configured to span a center two transistors in the series arrangement, and an inductor having a first terminal that is connected to an intermediate node that joins the center two transistors, each of the four transistors in the series arrangement being driven by a pulse width modulation signal from the controller based on a sequence of pulse width modulation states,
• the controller being configured to:
• measure an input voltage at a converter input;
• measure an output voltage at a converter output, the multilevel power converter including a power stage having four transistors in a series arrangement, the power stage including a flying capacitor configured to span a center two transistors in the series arrangement, the power stage including an inductor having a first terminal that is connected to an intermediate node that joins the center two transistors, each of the four transistors in the series arrangement being driven by a pulse width modulation signal based on a sequence of pulse width modulation states;
• determine a half input voltage based on the input voltage;
• compare the measured output voltage to the half input voltage;
• determine whether the measured output voltage is within a predetermined percentage of the half input voltage;
• when the measured output voltage is within the predetermined percentage of the half input voltage corresponding to a mid duty mode, the controller is further configured to:
• drive the four transistors in the series arrangement through the sequence of pulse width modulation states that includes a first state corresponding to magnetizing the inductor, a second state corresponding to charging the flying capacitor, a third state corresponding to demagnetizing the inductor, and a fourth state corresponding to discharging the flying capacitor;
• and
• operate the multilevel power converter to produce an output current through the inductor to the converter output at the output voltage based on the sequence of pulse width modulation states.