Integrated single-inductor multiple-output and adaptive DC-DC conversion for efficient power management

Emerging portable applications demand low-power operation to maximize battery run-time, and high-efficiency DC-DC conversion is a key ingredient in low-power systems. Recently, voltage scheduling techniques such as dynamic voltage scaling (DVS) and multiple supply scheduling (MSS) have been demonstrated to be the most effective ways in efficient power management, which require multiple or/and adaptive-output power converters. However, researches on such DC-DC conversion techniques are still in the theoretical stage. This research first analyzes and compares prior arts of DC-DC conversions on topology, control method, stability and circuit implementation issues. A family of single-inductor multiple-output (SIMO) converters are then proposed as cost-effective solutions in realizing multiple-output converters. A time-multiplexing (TM) control method is developed to solve the cross regulation problem, which widely exists in multiple-output counterparts. Freewheel switching control and pseudo-continuous conduction mode (PCCM) are first introduced to SIMO converters to decrease current and voltage ripples, and reduce switching noise and current stress. The designs are extended to transform one supply voltage to virtually any given multiple output voltages, regardless of whether the output voltage is higher or lower than the input voltage, or having the same or opposite polarity. A CAD simulator on closed-loop gain analysis of SIMO converters is developed on the MATLAB platform. As a nonlinear simulator, it is capable of simulating both time domain performance and frequency response of closed-loop SIMO converters. The simulator is applicable for loop compensation and stability analysis on nonlinear switching networks. Adaptive-output converter design is next discussed. Design challenges on dynamic response, stability, line and load regulations are analyzed. A dual-loop one-cycle control is then developed to achieve a very fast tracking time, while retaining accuracy for output voltage regulation. This work also covers techniques on on-chip one-cycle control implementation and can be extended to any other DC-DC conversion topologies. Three integrated CMOS DC-DC converters have been fabricated and tested successfully, demonstrating the techniques proposed in this research. All the designs have good line and load regulation with high efficiency. The designs could be developed as standard systematic techniques in realizing cost-effective and high-efficiency power management systems