Research And Design Of Single Inductance Multi - Output DC - DC Converter Based On Ripple Adaptive Shutdown Time Control

In recent years, as the representative of smart phones, tablet PCs and e-books, portable electronic devices have become the backbones for further developing the technological revolution. As the issue which the consumer most concerned about, keeping long battery lifetime in portable devices usually requires the use of different voltage levels with a wide range of load capability for various functional blocks, but meanwhile this method will increase the cost of power management unit. Since a single-inductor-multiple-output (SIMO) converter can support multiple high-efficiency output voltages while using only one inductor, it is an excellent candidate to minimize the component count and thus the production cost. Therefore SIMO becomes a hot research direction of the DC-DC converter.In this dissertation, the basic structure and operating characteristics of SIMO converters are studied. The inherent problems of SIMO structure and inadequacies of the existing control method are also analyzed by investigating and summarizing the SIMO control principle. On the basis of this, a ripple-based adaptive off-time (RBAOT) control method is proposed in this dissertation to solve the contradiction between efficiency and cross-regulation and this control method can also achieve fast response speed and smaller implementation complexity. Furthermore, RBAOT control method is applied to a single-inductor-four-outputs buck converter and verified by testing result to demonstrate the stability and practicality of this control method.The RBAOT controlled single-inductor-four-outputs buck converter is designed and implemented on GF2P4M0.35μm CMOS process in this dissertation, and the off-chip inductor and output capacitors are4.7μH and10μF, respectively. The measurement results show the switching frequency of the converter is locked in1MHz accurately in different I/O conditions and each output ripple is less than30mV. For the dynamic characteristics, the converter can achieve fast load response with cross-regulation less than0.04mV/mA and DVS response speed reached50mV/μs. The peak efficiency of the converter can reach87%.