Other than by reducing power, extending battery life in portable microelectronics amounts to increasing power efficiency, which, when coupled with accuracy, translates to increasing filter inductance. The problem with higher inductances is that magnetic cores require more space to prevent the onset of saturation, so accuracy and efficiency (via their need for bulky inductors) hamper the miniaturization benefits gained from chip integration. This paper illustrates the time-domain and efficiency effects of inductor saturation in switched-inductor DC-DC converters and shows how they can accommodate saturation (with up to 65% reduction in inductance) with minimal impact on battery life and accuracy. Extending the useful range of an inductor in this fashion not only reduces the printed circuit board (PCB) area and volume to a fraction (e.g., 30-50%) of what an otherwise larger unsaturated inductor would require, but also helps bridge the integration gap that enables practical system-on-chip (SoC) implementations.
While the large passive elements of power converters are in the way of converging walls of shrinking cell phones and cameras, the new capabilities these devices flaunt are creating additional burdens and making it difficult to meet specifications without even bigger elements. Active circuits that enhance the effects of passive elements will allow power converters to handle larger loads and get smaller at the same time. This paper presents a predictive inductor multiplier circuit that amplifies the effective inductance in a Buck converter. The output ripple of the simulated converter is so small that the converter appears to have an inductance thirty-eight times the value actually used. Compensating for small inductors introduces new power losses, but it is discovered that linear regulators and faster switching converters can be even less efficient.
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