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A single-inductor dual-output boost converter reported in works either in discontinuous conduction mode or in pseudo-continuous conduction mode and requires separate controllers. As each controller regulates the output in time-multiplexed manner, it is difficult to extend the number of outputs and power capacity. The converter reported in solves these limitations by adopting comparator-controlled method. Each comparator-controlled output receives its required energy and one final PWM controller adjusts the total inductor current so that the remaining current is adequate for the last output. However, as the PWM controller regulates one of the converter outputs, the response of controller becomes slow and voltage ripple of the other outputs increases when the load current of PWM-controlled output is reduced to zero (or near zero). As a possible solution, minimum bleeding current can be set for the last output, however, this approach degrades the efficiency at light-load condition. Also, the operation region of the previously reported multiple- output converters is restricted to step-up mode only.
Date of Conference: 8-12 Feb. 2009