Method for controlling a non-inverting buck boost DC-DC converter and corresponding converter

A method for controlling a non-inverting buck boost DC-DC converter that includes:

• a first input half bridge coupled to an end of an inductive coil and a second output half bridge coupled to an other end of said inductive coil, said first input half bridge comprising a first high side switch coupled between an input node and said end of the inductive coil and a first low side switch coupled between said end of the inductive coil and ground, said second input half bridge comprising a second high side switch coupled between an output node and said other end of the inductive coil and a second low side switch coupled between said other end of the inductive coil and ground, the method comprising:
• providing a control voltage based on an error between a feedback signal from said output of said non-inverting buck boost DC-DC converter and a reference signal;
• performing a first comparison of said control voltage, adding an offset voltage, with a reference signal that is proportional to a current flowing in said inductive coil, said first comparison detecting the control voltage reaching a peak voltage;
• performing a second comparison of said control voltage, subtracting the offset voltage, with a reference signal that is proportional to the current flowing in said inductive coil, said second comparison detecting the control voltage reaching a valley voltage;
• generating from results of the first and second comparisons control signals applied to said switches of said non-inverting buck boost DC-DC converter to drive switch opening and closing;
• controlling operation of said non-inverting buck boost DC-DC converter with ripple-hysteretic-current-mode-control in a plurality of states of operation including:
• a first state in which said control signals cause the first high side switch and the second low side switch to be closed;
• a second state in which said control signals cause the first high side switch and the second high side switch to be closed;
• a third state in which said control signals cause the first low side switch and the second high side switch to be closed;
• and
• a fourth state in which said control signals cause the first low side switch and the second low side switch to be closed;
• wherein said controlling comprises:
• passing from the first state to the second state when the control voltage is detected reaching the peak voltage;
• passing from the second state to the first state when the control voltage is detected reaching the valley voltage;
• passing from the second state to the third state upon detection of the expiration of a first time interval, measured from entering the second state, having a length that varies as a function of a set of detection parameters and decreases with increase of said input voltage, said control voltage being detected as having not reached said valley voltage;
• passing from the third state to the fourth state when said control voltage is detected reaching said valley voltage and a second time interval, having a fixed length measured from entering said third state, is not expired;
• passing from the third state to the first state when the second time interval is expired and the control voltage is detected reaching the valley voltage;
• and
• passing from the fourth state to the first state when the second time interval is expired.