Marco Passoni

Lossless current sensing in low-voltage high-current DC/DC modular supplies

New data processing ICs require low-voltage high-current supplies together with high reliability and efficiency. The use of a modular power supply would be the ideal solution, but it requires detecting the current in each module, and resistive shunts are usually used. In this paper, a new lossless current-sensing circuit is presented. This lossless current transducer is obtained by applying the technique used to compensate the parasitic inductance in resistive shunts to the filter inductor of the DC/DC power supply. The causes that can influence transducer response are investigated. The current sensing was implemented in a modular DC/DC power supply and experimental results are reported.

Analysis of High-Frequency IGBT Soft Switching Buck Converter With Saturable Inductors

In this paper, a high switching frequency buck converter using insulated gate bipolar transistors (IGBTs) is presented. This was done by using an auxiliary branch made of an IGBT of the same type as the one used for the main switch and saturable inductors. The proposed topology allows both switches to be fully soft switched to keep the efficiency high over a wide load range. Because of its topology the open loop behavior of the converter can be unstable. A detailed small signal analysis is presented to explain this behavior and as a basis for the synthesis of a closed loop controller. Experimental measurements on a laboratory prototype demonstrated the accuracy of the small signal analysis and validated the operation of the auxiliary network. The resulting efficiency is around 92% over a 200 to 800W output power range and at a 80-kHz switching frequency

A high efficiency integrable power converter with soft switching slew-rate control

Slew-rate control (SRC) in integrated switching power stages for noise sensitive systems is presently carried out at switching loss expense by linearly driving the power devices in the active region during the rising and falling output voltage edges. In this work, the zero voltage transition soft switching technique is considered as a means of performing the same SRC function. A bridge-type power scheme is proposed and three structures for the auxiliary branches are evaluated in a breadboard prototype. Experimental results demonstrate that better efficiency than the conventional SRC technique can be attained by splitting the auxiliary branch structure. Finally, preliminary aspects of converter integration are presented.

Grating Couplers in Silicon-on-Insulator: The Role of Photonic Guided Resonances on Lineshape and Bandwidth

Most grating couplers for silicon photonics are designed to match the approximately 10 μm mode-field diameter (MFD) of single-mode telecom fibres. In this letter, we analyse grating-coupler designs in the Silicon-on-Insulator (SOI) platform in a wide range of MFDs (4–100 μm) and related footprints, to give a physical understanding of the trends in efficiency and lineshape of the corresponding coupling spectra. We show that large-footprint grating couplers have an intrinsic Lorentzian lineshape that is determined by the quasi-guided photonic modes (or guided resonances) of the corresponding photonic crystal slab, while small-footprint grating couplers have a Gaussian lineshape resulting from the k-space broadening of the incident mode. The crossover between the two regimes is characterized by Voigt lineshapes. Multi-objective particle-swarm optimisation of selected small-footprint apodized grating-couplers is then used to locate the “Pareto fronts;” along which the highest coupling efficiency is achieved f...

Design and optimization of a high insulation voltage DC/DC power supply with coreless PCB transformer

In this work the design and optimization of a DC/DC half-bridge converter with a coreless PCB transformer and high insulation voltage is presented. The analysis starts by computing coreless transformer magnetic parameters (i.e. auto and mutual inductance of the coils) through a simple Matlab/sup /spl reg// function. The procedure is applicable to both circular and rectangular spiral coils. These results were used to model the half bridge converter, and obtain the output V-I characteristic and the maximum output power. Detailed experimental results on a 4 W laboratory prototype confirmed theoretical predictions.

Comparison between PWM and sigma-delta modulation in a power factor correction system

In this work, the sigma-delta (MA) and the PWM techniques in boost power factor correction (PFC) systems, are compared. To make a comparison under the same power section operating conditions, the problem of evaluating the average switching frequency arises. Electromagnetic emission for both configurations is also investigated. The results show that the MA approach represents an effective solution for obtaining low distortion and that the introduction of a third level allows it to operate in DCM. Theoretical results were confirmed by simulations and experimental results on a laboratory prototype.

Modelling of DC-DC converter based on a piezoelectric transformer and its control loop

A modelling of a piezoelectric transformer DC-DC power converter is illustrated. The modelling of the power converter includes a piezoelectric transformer, an output rectifier stage and the control circuitry. The control loop is based on a phase and frequency detector circuit which always tracks the transformer resonance frequency. The modelling of the various parts is reported and discussed, the complete system is simulated and experimental results confirm the simulations.

A switching current-mode power stage based on sigma-delta modulation

An integrated current-mode switching power stage for hard-disk drive voice-coil motors is presented. In this system the current in the voice-coil is directly regulated by a sigma-delta modulator. Because of its nature the sigma-delta modulator does not need an external control loop so that a single loop system is obtained. The output stage employs a H-bridge and uses the zero voltage transition commutation technique to control the slope of the output voltage. Output voltage slope control is a basic requirement for the application in order to prevent interference with the hard disk drive signal circuitry. Preliminary experimental results on a prototype are presented.

An integrated switching current-mode sigma-delta power stage for hard disk drives

An integrated current-mode switching power stage for hard-disk drive voice-coil motors is presented. In this system the current in the voice-coil is directly regulated by a sigma-delta modulator. Given its nature, the sigma-delta modulator does not need an external control loop and a single loop system is thereby obtained. The output stage employs an H-bridge and uses the zero voltage transition commutation technique to control the slope of the output voltage. Output voltage slope control is a basic application requirement to prevent interference with the hard disk drives signal circuitry. Preliminary experimental results on a prototype are presented. The system showed it could work with an output slope of up to 500 V//spl mu/s with no significant performance losses.

Comparison of transient performance in a peak current-mode flyback converter

In this paper, the voltage regulation of a flyback converter under load transient conditions is investigated. First, the best regulation is found with an optimization algorithm which uses a cycle-by-cycle model. The predictions are then compared with the performance given by an optimized peak current-mode controlled converter. Simulation results are then provided to highlight the two different output voltage dynamics during load transients.