Challenges and Solutions for Non-Inverting Buck-Boost Converters

This paper discusses several challenges in the design of non-inverting buck-boost regulators. These range from the design of control loop to operation in various regions and associated issues. Several novel schemes are introduced like a universal timer which could work in all the regions of buck-boost, an adaptive region detector which provides optimum point of region-transition independent of input and output voltage measurements or load current and a simple state machine controlled trapezoidal regulation which enables efficient switching. These enable a peak current mode control with adaptive off-time to be maintained throughout all the regions preventing control loop discontinuities. All the ideas presented here are realized on a silicon integrated circuit. Subsequently these concepts are validated and proven through rigorous LAB analysis leading to a commercially usable product which generates adjustable outputs in the range of 1.8V to 5.2V from input voltages in the range of 1.3V to 5.5V.