A novel ripple controlled modulation for high efficiency DC-DC converters

To achieve high conversion efficiency, traditional DC-DC converters usually employ the hybrid-mode control, which is a combination of pulse-width modulation (PWM), pulse-frequency modulation (PFM) and pulse-skipping modulation (PSM) controllers. However, the hybrid-mode control does not maximize the efficiency because it only concerns about the load change of the converter under light-load condition, without taking the full range of load variation and the source voltage variation into consideration. In addition, a hybrid-mode controller also includes complex mode-switching circuit, which brings in more design difficulties. In this paper, a new ripple controlled modulation (RCM) is proposed. It aims to maximize the conversion efficiency with simple control. This is done by using a ripple controlling loop to optimize the switching frequency according to the converter output voltage ripple under all source and load conditions.