12.5 An error-based controlled single-inductor 10-output DC-DC buck converter with high efficiency at light load using adaptive pulse modulation

Abstract

Reducing the number of large external components, especially inductors, is a very important issue for Power-Management ICs (PMICs). Single-Inductor Multiple-Output (SIMO) converters are excellent candidates to meet this requirement [1-3]. However, there are several issues with SIMO converters, such as cross regulation, instability and inefficiency at light load. Under normal load conditions, comparator-based controlled SIMO converters [1,2] show good cross regulation performance due to the fast response of the comparator. However, the switching loss remains constant and degrades light load efficiency due to the fixed switching frequency of output switches. The low-efficiency characteristic when any output is under light load condition is a critical issue that must be solved because a SIMO converter is very suitable for light load applications. In addition, the cross regulation issue appears again when any output is under no load because the output receives energy from the inductor every cycle despite the load condition. To solve these issues, a SIMO converter was previously reported to support Pulse Frequency Modulation (PFM) mode [3]. However, the mode change control method increases the complexity of the control loop, which makes it unsuitable for a multi-output SIMO converter. In this paper, an Error Based Controlled (EBC) SIMO converter is presented to resolve the problems raised above using load-dependent Adaptive Pulse Modulation (APM). A hybrid topology composed of a switching converter and a linear regulator is also presented to minimize the cross regulation issue. To highlight the advantages, a 10-output SIMO converter is designed.