US Patent 7394231 Current-mode control for switched step up-step down regulators

A switched regulator circuit provides step-up and step-down operation in which the level of the input voltage can be greater, equal to, or less than a preset controlled output voltage. A four switch arrangement or two switch arrangement provides buck, boost, and buck-boost regulation under constant frequency valley-peak current mode control. A single sense resistor may be utilized for sensing inductor current during only a short period during each duty cycle. As an alternative to the sense resistor, the switches themselves can be used to sense current during operation.