Dual current path power management integrated circuit design for step-down multiple-output and step-up output

Abstract

In Chapter 1, portable electronic devices require multiple supply voltages with relatively large differences in load currents, which causes serious problems such as regulation problem, EMI issues, and low efficiency when adopting a single-inductor multiple-output (SIMO) DC-DC converter. To resolve these problems, this paper presents a SIMO system with 10-output dual-bus DC-DC converter having two buses for heavy and light load outputs, respectively. The converter maintains the load condition for each bus to be well balanced even when the load currents are diversified with the proposed group allocator that properly assigns the bus for each output depending on its load current. The allocation of the load currents is performed using a load current sensing technique of the group allocator specialized for a multiple-output converter. Due to such load balancing function, regulation issues which could occur under diversified load condition are resolved. In measurement result, the system has 10 independently regulated outputs with output voltage ripples below 25mV, and over 81% efficiency is achieved under wide range of load (0-300mA). In Chapter 2, this paper proposes a new boost converter topology called dual-path step-up converter (DPUC). Unlike conventional boost converter (CBC), which has single path, it has a hybrid structure using one inductor and one flying capacitor and has two paths that can deliver the current. This allows the current delivered to the output to be continuous, reducing the DC level of the inductor current and significantly reducing the output voltage ripple. Therefore, DPUC has higher efficiency and smaller output voltage ripple than CBC. This means that smaller inductors and capacitors than CBC can be used. In addition, the feedforward nature of the flying capacitor can reduce the RHP-zero effect that slows the transient response of the CBC. The measured results show that the DPUC has a high efficiency of 95.2% and a small ripple of up to 15mV can be observed even though the DCR of the inductor is 200m$\Omega$. Moreover, the RHP-zero effect reduced by the load transient response.