Commonly controlled buck-boost converter

A controller for a buck-boost converter comprising a high side buck switch coupled to a low side buck switch at a first switch node and a high side boost switch coupled to a low side boost switch at a second switch node, the buck-boost converter configured to have an inductor coupled between the first switch node and the second switch node, the controller comprising:

• a compensator responsive to a feedback signal based at least in part on an output voltage of the converter to generate a compensation voltage;
• and
• a modulator comprising:
• a buck signal path comprising a summation element configured to add an offset value to the compensation voltage to generate a first offset voltage and a subtraction element configured to subtract a ramp voltage from the first offset voltage to generate a first threshold voltage, wherein the buck signal path is coupled to receive the compensation voltage and to generate a control signal to control an on time of the high side buck switch based at least in part on a current through the inductor and a first threshold voltage having a first slope;
• and
• a boost signal path comprising a subtraction element configured to subtract the offset value from the compensation voltage to generate a second offset voltage and a summation element configured to add the ramp voltage to the second offset voltage to generate a second threshold voltage, wherein the boost signal path is coupled to receive the compensation voltage and to generate a control signal to control an off time of the high side boost switch based at least in part on the current through the inductor and a second threshold voltage having a second slope.