Closed Loop Analysis of Single-Inductor Dual-Output Buck Converters with Mix-Voltage Conversion

A single-inductor dualoutput (SIDO) buck converter has recently found applications in handheld battery-powered electronic devices. The circuit operation and the functional interdependencies among basic converter parameters such as dc voltage gains, transistor duty cycles, and load current levels are much more complicated than those of the singleoutput counterpart. In this project, a rigorous analysis was conducted to develop dc equations in steady state operation for SIDO converters. More importantly, from the analysis results, a possibility of a new mode of operation, dubbed “mix-voltage” operation, will be pointed out. In the so-called “mixvoltage” operation, the converter is capable of working even when the input voltage is lower than one of the two output voltages. In the past, a SIDO buck converter has been used for providing “pure-buck” outputs, i.e., both output voltages are lower than the input voltage. Therefore, this possibility not only opens up new applications but also extends the operating battery range in existing applications. Experimental results confirmed the dc equations and the “mix-voltage” conversion of SIDO buck converters. KeywordsDC Power converters,mixvoltage conversion,single inductor dual output (SIDO).