Abstract:

Increasing the operating frequency of the DC-DC converter is a direct way of reducing the size of energy storage elements such as bulky capacitors and inductors, which usually dominate the overall converter size. The challenges arise when the converter operating frequency is increased into Very High Frequency (VHF) range from 30 MHz to 300 MHz; the conventional topologies become impractical. In the literature one can find the converter circuits suitable for operation in this frequency range. Some of them, for the lower end of the band, were breadboard prototyped, yet, their fully integrated realization, to the best of our knowledge, is not known yet.

The VHF converters may be loosely qualified as the circuits with self-oscillating resonant gate drivers. This driver is realized using a separate from load oscillating circuit. In our case the load and feedback circuits are combined using one integrated transformer. Usually an integrated coil is realized using the top metal layer of lowest resistivity.

The layers under this coil can be used to create a transformer secondary without any additional silicon area. The transformer parameters and layout were carefully investigated, and it happens that the high resistance of the secondary is only beneficial in our case: the secondary operates as open circuit, it does not introduce any load in the primary, the description of the circuit operation is simplified, and the oscillation frequency may be evaluated.

In the proposed converter the primary represents a “necessary” passive connection providing the path from the power supply to the capacitive load. The core of the system is the feedback loop. The feedback loop, besides of the secondary, includes a duty cycle detector and a pulse-shaping circuit. The output signals of the pulse-shaping circuit represent two in-phase rectangular pulses driving the gates of power transistors. As usual in the feedback systems, it is the feedback that determines such parameters as, for example, the system stability. For this reason we provide full calculation of signals in the duty cycle detector.
We describe the full circuit of the proposed converter and its operation principle. Then the detailed analysis of the signals in the duty cycle detector is given. The recommendations on smooth start-up of the converter power transient are provided. Then we describe the circuit layout. Finally, we discuss the obtained results and outline the direction of further investigation.

Bio

Igor M. Filanovsky received the M.Sc. degree in 1962 and the Ph.D. degree in 1968, both in electrical engineering from V. I. Ulianov (Lenin) Institute of Electrical Engineering, Leningrad, USSR. In 1976, he joined the University of Alberta, Canada, where he is currently a Professor Emeritus. Dr. I. M. Filanovsky is the author or coauthor of 9 books and about 300 journal and conference papers on circuit theory (theory of approximation, theory and technical applications of oscillations, strongly nonlinear oscillations), and applied microelectronics (analog electronic circuits, oscillators and multivibrators, signal-conditioning circuits for sensors). He has four patents on electronic circuits. His paper ”A 100 dB CMRR CMOS Operational Amplifier with Single-Supply Capability,” co-authors V. Ivanov and Junlin Zhou, obtained “The Best Paper Award” at the International Conference on Electronics, Circuits and Systems, ICECS2004, Tel-Aviv, Israel. Dr. I. M. Filanovsky is currently an Associated Editor of CTA.

Date: 2015-Nov-23     Time: 14:00:00     Room: 336

For more information:

• l.oliveira@fct.unl.pt