Switching power supplies, due to their high-frequency switching operation, draw a substantial amount of input ripple current. Such ripple current manifest itself as electromagnetic interference (EMI). Active and passive ripple cancellation methods have been proposed in the past. This paper discusses the cancellation methods, and classifies the basic circuit configurations for ripple current cancellation. The basis of discussion is a 'nullification' process, which can be described effectively in terms of the ideal circuit element nullor. The initial focus is on differential-mode noise cancellation, but the basic technique can be applied equally to cancelling common-mode noise. The classification provides a clear guideline for synthesizing practical cancellation circuits. Both active and passive implementation examples are given and experimentally demonstrated.published_or_final_versio

This paper discusses the basic construction procedure and topological possibilities of creating AC/DC converters out of simple DC/DC converters. It is shown that two separately controlled DC/DC converters are sufficient for producing a regulated DC output and shaping the input current, from an AC voltage source, without the need for input rectifiers. Some design constraints are discussed, emanating from the limitation of the conversion ratios that can be achieved by particular DC/DC converters. Selected topologies are verified experimentally. This kind of rectifierless converter find applications in airborne power supplies where zero-crossing distortions are significant because of the inevitable phase-lead effect of the input rectifier bridge.

A novel current-driven synchronous rectifier is presented in this paper. With the help of a current sensing energy recovery circuit, the proposed current-driven synchronous rectifier can operate at high switching frequency with high efficiency. Compared with those voltage-driven synchronous rectification solutions, this current-driven synchronous rectifier has several outstanding characteristics. It can be easily applied to most switching topologies like an ideal diode. Constant gate drive voltage can be obtained regardless of line and load fluctuation. This makes it desirable in high input range application. Power converters designed with this synchronous rectifier are also capable of being connected in parallel without taking the risk of reverse power sinking. Their principle of operation is given in the paper. A series of experiments verify the analysis and demonstrate the merits.

Predicting the expected life of switching power supply is essential since unexpected failure of the subsystem can produce enormous loss. Electrolytic capacitor is the weakest among various power components in a power converter. Monitoring the Equivalent Series Resistance (ESR) variation of the electrolytic capacitor, achieving by voltage and current ripple, can estimate the converter life. Currently, Hall Effect sensor or others are current sensing options but all of them add series impedance to the capacitor and deteriorate capacitor voltage waveform. A sensor-less current waveform prediction method is proposed. Popular current mode control with the switch current signal is used. Repetitive sampling on the switch current allows capacitors current waveforms prediction without any current sensor at capacitor nodes. Together with the voltage waveform acquired, the ESR value can be calculated.

A single-phase fast transient converter topology with stepping inductance is proposed. The stepping inductance method is implemented by replacing the conventional inductor in a buck converter by two inductors connecting in series. One has large inductance and the other has small inductance. The inductor with small inductance will take over the output inductor during transient load change and speed up dynamic response. In steady state, the large inductance takes over and keeps a substantially small ripple current and minimizes root mean square loss. It is a low cost method applicable to converters with an output inductor. A hardware prototype of a 1.5-V dc-dc buck converter put under a 100-A transient load change has been experimented upon to demonstrate the merit of this approach. It also serves as a voltage regulator module and powers up a modern PC computer system

The expanding functions of the emerging smart grid have posed new technical challenges on the power supplies for online monitoring systems in the transmission and distribution networks. A recent study has suggested that magnetic energy around the transmission line can be harvested and delivered wirelessly to the monitoring equipment through printed circuit board (PCB) resonators embedded inside an insulation rod. This article presents a rigorous analysis, modeling, and optimization of such PCB resonators. A new closed-form quasi-static model of the PCB resonators is derived. A fully automated simulation-driven optimization framework is constructed to enhance the quality factor of the resonator. Practical measurements show that the optimal design improves the quality factor ( $Q$ factor) from 52 to 132 as compared to the existing trial-and-error design. The corresponding wireless power transfer efficiency in a 20-W prototype across a 1.14-m distance improves significantly from 11 to 46%.