Comprehensive analysis and design of a switched-inductor type low inductance-requirement DC-DC buck-boost converter for low power applications

This paper aims to comprehensively analyze, critically discuss, and provide a step-by-step design guideline for a previously proposed Modified Switched-Inductor type Buck-Boost (MSIBB) converter which is based on a boost converter. The MSIBB converter is originally based on switched-inductor phenomena whereby two inductors are switched in a proper sequence to ensure appreciable buck as well as boost characteristics. Appreciable buck and boost characteristics are desirable specifically in low power applications. In regulated low power applications, DC-DC switching power converters undergo frequent mode-shift from buck to boost, and vice versa. At the overlap between input/output voltage, the converters efficiency does not suffer significantly, but the wide input-voltage operating area compels the regulated converters to operate at extreme values of the duty cycle, that is, close to 0 and 1, which causes lower efficiency. A high-efficiency switching converter is required specifically for low-power applications that can ensure voltage step-up and step-down without resorting to operating at extreme values of the duty-cycle. In this perspective, switched-inductors based converter, termed as MSIBB converter, was previously proposed. The MSIBB converter exhibits appreciable voltage-gain, and experiences lesser current/voltage stress on the semiconductor components. In particular, it has comparable Maximum Switch Stress Factor that generally translates to alleviated switch conduction and switching losses. Besides, the inductors minimum peak stored energy is comparatively lower, reflecting reduced physical size of the inductors as well as reduced onboard losses, and therefore better caters to low power applications. Detailed analysis of the converter and step-by-step approach for design example, and comparative analysis are carried out, besides providing some experimental results from the previously proposed converter.