Single-inductor multiple-output (SIMO) step-up DC-DC switching converter with modified comparator control (MCC)

Abstract

Among multiple output dc-dc converter ICs, this thesis deals with single-inductor multiple-output (SIMO) dc-dc converters which adopted ordered power distributive control (OPDC) for a compact, cost-effective and power-efficient feature in a battery-operated portable device. Firstly, a single-inductor step-up DC-DC switching converter with bipolar outputs is implemented for active-matrix OLED mobile display panels. The positive output voltage is regulated by a boost operation with a modified comparator control (MCC), and the negative output voltage is regulated by a charge-pump operation with a proportional-integral (PI) control. The proposed adaptive current-sensing technique successfully supports the implementation of the proposed converter topology and enables the converter to work in both discontinuous-conduction mode (DCM) and continuous-conduction mode (CCM). In addition, with the MCC method, the converter can guarantee a positive output voltage that has both a fast transient response of the comparator control and a small output voltage ripple of the PWM control. A $4.1 mm^2$ converter IC fabricated in a $0.5\mum$ power BiCMOS process operates at a switching frequency of 1 MHz with a maximum efficiency of 82.3% at an output power of 330 mW. A SIMO converter which has three positive-output voltages is next discussed. The converter adopts two MCC-loops to regulate the first two output voltages fast and accurately with small voltage ripples. It is the first multiple MCC-implementation in a SIMO converter. The compensations of MCC loops are designed with off-chip manner to verify the operation experimentally and it is analyzed. The comparison results between a MCC and a conventional comparator control (CCC) prove experimentally that MCC is very powerful control method. The improved zero-current sensing circuit successfully rejects the malfunctions in a freewheeling operation of the reported OPDC SIMO converters, and it is verified experimentally. The min...