Electronic engineering

ABSTRACT Due to the functionality increase of modern battery- powered portable devices such as PDAs, smartphones, and notebooks etc.., the battery life is an important issue. An efficient voltage regulator (VR) is a must if we need to extend the battery life. For this purpose, this paper discusses the employment of two-stage architecture on the design of point-of- load (POL) Dc-Dc converters. At first, the paper discusses the benefits of replacing the conventional one-stage buck converter by an integrated two-stage step-down converter. The design aspects of a two-stage 6V-to-1V converter are shown as an example to clarify the benefits of the design over one-stage approach. The results show that efficiency of two-stage converter is higher than the one-stage approach by at least 5% in addition to size and cost reduction. Then, the benefits of replacing boost converters by integrated two-stage step-up converters are discussed followed by a design example for two- stage step-up converter from 3.6V-to-12V. The results show that the two-stage approach increases the efficiency of the converter in addition to the benefits from stability point of view.

ABSTRACT Recently, most of researches are directed toward the design of small size and high efficiency power management integrated circuits (PMICs). The advantage of small sizes supports minimizing the PCB area. The high efficiency advantage supports the increase of battery life and energy saving. This paper presents a high efficiency two-stage voltage regulator for the point-of-load (POL) applications. A 6V-to-1V converter is divided into two conversion stages. The first stage is a high efficiency switched capacitor converter to obtain 3V from the 6V input. This low output voltage (3V) gives the chance to design second stage buck converter with a very high efficiency and a small footprint with 3-1V conversion. A detailed design of the fully integrated two-stage converter is provided using H-Spice. The results show a better performance for this combination than using the regular design of one stage 6-1 buck converter. The combined system achieves 93.6% peak efficiency and an average efficiency of 91% over an output current range from 1A to 6A.

In multiple receivers wireless power transfer (WPT) systems, it is preferable to retune the resonant frequency of every receiver to the transmitter operating frequency in front of frequency mismatches. This paper discusses a proposal for electronic tuning for WPT receivers by means of a variable active switch-mode inductance. The proposed method benefits from the gyrator concept to emulate a variable inductance. Instead of the conventional approach of linear amplifier based implementation of a gyrator, a switch-mode gyrator circuit is exploited for more efficient operation. Additionally, a PLL-like control is presented to enable self-tuning for the receiver resonant tank. Furthermore, a design-space characterization for the system dynamic behavior has been discussed to show the control robustness and the instabilities (including slow-scale and fast-scale chaotic instabilities) it may undergo.