An automatic slope compensation adjustment technique for peak-current mode DC-DC converters

Abstract In a current-mode switching DC-DC converter, the amount of deliverable energy to the load depends on the inductor current limit for the safety of the power components and the slope compensation current which is determined by the slope of the inductor current and the switching duty cycle. However, excess or insufficient slope compensation current may reduce the available load current or cause subharmonic oscillations, respectively. This paper presents an input-to-output conversion ratio sensing circuit which sets a proper slope-compensation (SC) current to avoid both excess slope compensation current and subharmonic oscillations. Both the slope and the duty-cycle of the proposed slope-compensation current are automatically adjusted based on the sensed input-to-output conversion ratio. As a result, the maximum available output current and the main-loop bandwidth of the converter are improved by the proposed structure. The compensation current is generated based on a fast ( μ s settling time) sensing circuit to track the input voltage or the load current changes. The proposed slope-compensation circuit was integrated into a boost topology with 0.038 mm2 extra silicon area and 190 μ A current consumption.