DC-DC converter-aware power management for battery-operated embedded systems

Abstract

Most digital systems are equipped with DC-DC converters to supply various levels of voltages from batteries to logic devices. DC-DC converters maintain legal voltage ranges regardless of the load current variation as well as battery voltage drop. Although the efficiency of DC-DC converters is changed by the output voltage level and the load current, most existing power management techniques simply ignore the efficiency variation of DC-DC converters. However, without a careful consideration of the efficiency variation of DC-DC converters, finding a true optimal power management is impossible. In this work, we solve the problem of energy minimization with the consideration of the characteristics of power consumption of DC-DC converter. Specifically, the contributions of our work are: (1) We analyze the effects of the efficiency variation of DC-DC converters on a single task execution in DVS (dynamic voltage scaling) scheme, and propose a technique, called DC/spl I.bar/DVS, of DC-DC converter-aware energy-minimal DVS; (2) DC/spl I.bar/DVS is then extended to combine the effects of DC-DC converters with the procedures of general DVS techniques with multiple tasks; (3) Conversely, we propose a technique, called DC/spl I.bar/CONF, of generating a DC-DC converter that is best suited, in terms of total energy efficiency, to the intended application, and (4) finally, we complete our integrated framework DC-lp, which is based on DC/spl I.bar/DVS and DC/spl I.bar/CONF, that attempts to solve the DC-DC converter configuration selection problem and the DVS problem simultaneously. To show the effectiveness of the proposed techniques, a set of experimental results is provided. In summary, it is shown that DC-lp is able to save 16.0% /spl sim/ 22.1% of energy on the average, which otherwise was dissipated in the previous power management schemes with no consideration of DC-DC converter efficiency variation.