Quasi-resonant Research Articles

Analysis of the Input Current Distortion and Guidelines for Designing High Power Factor Quasi-Resonant Flyback LED Drivers

Nowadays, LED lamps have become a widespread solution in different lighting systems due to their high brightness, efficiency, long lifespan, high reliability and environmental friendliness. The choice of a proper LED driver circuit plays an important role, especially in terms of power quality. In fact, the driver controls its own input current in addition to the LED output current, thus it must guarantee a high power factor. Among the various LED drivers available on the market, the quasi-resonant (QR) flyback topology shows interesting benefits. This paper aims at investigating and analyzing the different issues related to the input current distortion in a QR flyback LED driver. Several effects, such as the distortion caused by the ringing current, crossover distortion due to transformer leakage inductance and crossover distortion due to the input storage capacitor have been experimentally reported. These effects, not previously studied for a high power factor (Hi-PF) QR flyback, have been analyzed in depth. Finally, some practical design guidelines for a Hi-PF QR flyback driver for LED applications are provided.

A Dual Active Clamp DC–DC Converter With High Voltage Gain

In this article, a novel dual active clamp converter with high voltage gain is proposed for dc-dc applications. The active clamps' switches turn on and off under zero-current switching (ZCS). In addition, the main switch turns on under ZCS condition, as well. Therefore, switching losses are significantly reduced. The converter is also capable of operating under quasi-resonance (QR) mode. In this mode, switching losses are reduced further by lowering the voltage and current, at which the main switch turns off. In comparison with the conventional interleaved converter, the voltage gain of the proposed converter is almost the same, but the number of semiconductors and switching loss are significantly reduced. The switching frequency of the active clamps' switches is half of the main switching frequency. The operation principles of the proposed converter are studied in both pulsewidth modulation and QR modes, and the advantages are investigated. A 200-W prototype is implemented to validate the desired functionality of the converter, and experimental results are compared in both modes.

A real-space Green’s function approach for disordered Hubbard model

Based on the equation-of-motion approach, a real-space Green’s function method is proposed, which allows us to fully consider the disorder effect in Hubbard model. Meanwhile, we improved the decoupling scheme to obtain the quasi particle resonance peak on the Fermi energy, consistent with the DMFT method with Quantum Monte Carlo solver. After introducing the Anderson disorder into the system, the three peak structure in spectrum density still exists at intermediate regime of Coulomb interaction. However, the electronic state tends to be restricted in some small puddles in presence of on-site disorder, suggesting the Anderson localization has been introduced in the Kondo peak.

A Step-Up Nonisolated Modular Multilevel DC–DC Converter With Self-Voltage Balancing and Soft Switching

Evolving from the popular modular multilevel ac-dc converter, the single-stage nonisolated modular multilevel dc-dc converter (MMDC) is advantageous for medium- and high-voltage applications. However, exploiting ac circulating power to balance the submodule energy, when utilized for high step ratio applications, existing MMDC topologies suffer from circulating current through the arms and large filter inductor at the low-voltage side. To overcome these issues, this article presents a new power transfer mechanism to balance the submodule energy automatically by reconstructing the half-bridge submodule into a quasi-resonant circuit. Based on this submodule structure, a new MMDC topology for step-up applications is proposed. Compared to the existing MMDCs, the proposed one offers the following advantages. First, the common-mode circulating current through the lower and upper arms is avoided. Second, the self-balancing of the capacitor voltages is guaranteed by the proposed modulation method to insert and bypass adjacent submodules in a complementary manner. Third, the soft-switching operation is achieved for the majority of the switches to alleviate switching losses. Fourth, the voltage stress across the input side inductor is limited to the submodule voltage, thereby reducing the size of the inductor. Simulation analysis and experimental results verify the performance of the proposed MMDC.

Capacitor Charging by Quasi-Resonant Approach for a Pulsed Plasma Thruster in Nano-Satellite

In this article, a quasi-resonant (QR) flyback converter has been proposed for capacitor charging in a pulsed plasma thruster (PPT) of a nano-satellite. The energy in the transformer leakage inductance can be recycled to the resonant capacitor, suppressing the switch-off voltage spikes on the semiconductor power switch. The power switch is turned on with a hybrid switching mode. In this mode, valley-voltage-switching (VVS) is applied until the zero-voltage stress on the power switch is obtained, and zero-voltage-switching (ZVS) is used in the remaining charging process. Consequently, the switching-on loss is reduced, and charging efficiency is improved. When a capacitor bank of $2\mu \text{F}$ is charged to 1.5 kV (i.e., 2.25 J), the switching loss contribution of QR flyback converter using hybrid switching approach is reduced significantly to 0.61% while a flyback converter using hard-switching technique has a switching loss contribution of 15.24%. As a result, the proposed QR flyback converter improves the charging efficiency by 2.43%, from 72.69% to 75.12%. Moreover, the diode in the secondary side can be turned-on with zero-voltage and off with zero-current. Hence, the turn-on overshoot voltage and recovery loss are reduced.

Quasi-resonant flyback PSR converter with adaptive frequency control

In this paper, a quasi-resonant (QR) flyback primary-side regulation (PSR) converter with adaptive frequency control is proposed. The converter adopts the PSR scheme to detect load information through the auxiliary winding. The converter employs the QR control scheme to switch in the valley mode either in CV or CC operation, which greatly reduces the switching loss. In addition, according to the load condition, the converter adaptively reduces the switching frequency and realize valley switching, which achieves better light-load efficiency in the CV mode. The proposed QR converter was implemented using the HHGRACE 0.35 μm BCD process and verified in a 5 V/1A circuit prototype. Experimental results show that the light-load power efficiency of the proposed converter is improved by up to 4.0% when compared to the conventional QR controller. In addition, the valley switching is realized under different load conditions, which improves the system efficiency in the entire range of output load.

Design and Implementation of an Active Clamped Full Wave Quasi Resonant ZCS Boost Converter

This paper presents a closed loop control of an active-clamped full-wave quasi-resonant boost converter with zero-current-switching (ZCS) for power factor correction. Possibility to incorporate higherswitching frequency and has some potency to reduce switching losses. Power factor improvement and high efficiency is achieved with a constant output voltage and DC output voltage is regulated by using closed loop control .The concept of the proposed switchingscheme results lesser switching loss, higher efficiency, possibility to have higher switching frequency, and has potential to reduce converter's conducted EMI. This paper also presents voltage regulation using closed loop system and the simulation results are verified.

Quasi-Resonance Fluorine-19 Signal Amplification by Reversible Exchange.

We report on an extension of the quasi-resonance (QUASR) pulse sequence used for signal amplification by reversible exchange (SABRE), showing that we may target distantly J-coupled 19F-spins. Polarization transfer from the parahydrogen-derived hydrides to the 19F nucleus is accomplished via weak five-bond J-couplings using a shaped QUASR radio frequency pulse at a 0.05 T magnetic field. The net result is the direct generation of hyperpolarized 19F z-magnetization, derived from the parahydrogen singlet order. An accumulation of 19F polarization on the free ligand is achieved with subsequent repetition of this pulse sequence. The hyperpolarized 19F signal exhibits clear dependence on the pulse length, irradiation frequency, and delay time in a manner similar to that reported for 15N QUASR-SABRE. Moreover, the hyperpolarized 19F signals of 3-19F-14N-pyridine and 3-19F-15N-pyridine isotopologues are similar, suggesting that (i) polarization transfer via QUASR-SABRE is irrespective of the nitrogen isotopologue and (ii) the presence or absence of the spin-1/2 15N nucleus has no impact on the efficiency of QUASR-SABRE polarization transfer. Although optimization of polarization transfer efficiency to 19F (P19F ≈ 0.1%) was not the goal of this study, we show that high-field SABRE can be efficient and broadly applicable for direct hyperpolarization of 19F spins.

A Soft-Switched Power Module With Integrated Battery Interface for Photovoltaic-Battery Power Architecture

In conventional photovoltaic (PV)-battery systems, a centralized battery storage system (BSS) is typically connected through a separate bidirectional converter at the common dc link to support the PV system. It is known that a bidirectional converter typically requires more switches than a unidirectional converter, and hence, a complete PV-battery power interface will result in a high-cost system and will suffer high power losses. This paper proposed an integrated battery storage interface with soft-switching capability for module-integrated PV systems. In the proposed system, a multi-input converter (MIC) structure that consists of an integrated soft-switched quasi-resonant (QR) Cuk- and flyback-based circuit is presented. In this approach, the battery charging circuit is integrated with the input side of the PV power optimizer while the battery discharging circuit of the proposed system shares the output filter of the PV power optimizer, resulting in a compact and efficient system. The proposed converter is capable of tracking the maximum power point (MPP) and following the charging profile (constant voltage and constant current) of the battery. Moreover, all the switches in the proposed converter are able to achieve soft-switched turn on and turn off for different operating conditions. The operating principles and the theoretical analysis of the proposed system are presented. Experimental results on a 175-W proof-of-concept prototype are presented to demonstrate the features of the proposed converter.

Estimation of a class of quasi‐resonances generated by multiple small particles with high surface impedances

We deal with the stationary acoustic waves propagating in a cluster of small particles enjoying high contrasts. Such contrasts allow the appearance of (complex valued) resonances that are close to the real line as the size of the particles becomes small. For single (but not necessarily small) particles, we derive the characteristic equation that generates a class of these resonances (the ones for which the corresponding eigenfunctions are uniformly constant). For multiple and small particles, we provide sufficient conditions on the contrasts that generates quasi‐resonances for which the corresponding eigenfunctions are uniformly constant. Precisely, we show that, if we distribute the particles on a uniform line, then the existence of such quasi‐resonances is related to the eigenvalues of the Harary matrix. To show these results, we take, as the small contrasted particles, small obstacles with high surface impedances λ of the form λ: = βa−1 − αβa−1 + h where a is the maximum radi of the particles, with a < <1, and β is a universal and positive constant depending only on the shape of the particles (but not on their size). In this case, if the relative constant α is an eigenvalue of the Harary matrix, then the used frequency is a quasi resonance of the cluster of the small particles where the error of approximation is of the order for h ∈ (0,1) as a < <1.

MagCap DC–DC Converter Utilizing GaN Devices: Design Consideration and Quasi-Resonant Operation

A MagCap DC-DC converter using GaN semiconductor devices is presented to improve the efficiency and modularity of the vehicular power system. While the topology is as simple as the flyback converter, all the semiconductor switches turn on and off with soft switching. A design guideline to transformer and capacitor is suggested considering the conduction loss and voltage stress of the switches. A quasi-resonant (QR) operation for low output-power condition is also explained. The switches turn on at the valley of the drain-source waveform to secure soft switching and maximize the efficiency. A 180-W prototype hardware was populated on 63 mm × 31 mm printed circuit board using 200-V GaN FET devices. Peak efficiency was 97.1% at 155-W output power and 1.2-MHz switching frequency. Another prototype was built for the QR operation and demonstrated 91.6% peak efficiency by maintaining the soft switching and avoiding excessive switching frequency.

Modulation of Dual-Polarized X-Band Radar Backscatter Due to Long Wind Waves

Investigation of microwave scattering mechanisms is extremely important for developing methods for ocean remote sensing. Recent studies have shown that a common two-scale scattering model accounting for resonance (Bragg) scattering has some drawbacks, in particular it often overestimates the vertical-to-horizontal polarization radar return ratio and underestimates the radar Doppler shifts if the latter are assumed as associated with quasi linear resonance surface waves. It is supposed nowadays that radar backscattering at moderate incidence angles is determined not only by resonance Bragg mechanism but also contains non polarized (non Bragg) component which is associated supposedly with wave breaking but which is still insufficiently studied. Better understanding of the scattering mechanisms can be achieved when studying variations of radar return due to long wind waves. In this paper, results of experiments from an Oceanographic Platform on the Black Sea using dual co-polarized X-band scatterometers working at moderate incidence are presented and variations of Bragg and non-Bragg components (BC and NBC, respectively) and radar Doppler shifts are analysed. It is established that BC and NBC are non-uniformly distributed over profile of dominant (decametre-scale) wind waves (DWW). Variations of BC are characterized by some “background” return weakly modulated with the dominant wind wave periods, while NBC is determined mostly by rare and strong spikes occurred near the crests of the most intense individual waves in groups of DWW. We hypothesize that the spikes are due to intensification of nonlinear structures on the profile of short, decimetre-scale wind waves when the latter are amplified by intense DWW. Bragg scattering in slicks under the experimental conditions was suppressed stronger than NBC and spikes dominated in total radar return. It is obtained that radar Doppler shifts at HH-polarization are larger than at VV-polarization, particularly in slicks, the same relation is for NBC and BC Doppler shifts, thus indicating different scattering mechanisms for these components.

Soft-switching cells for Modular Multilevel Converters for efficient grid integration of renewable sources

The Modular Multilevel Converter (MMC) concept is a modern energy conversion structure that stands out for a number of interesting features that opens wide application chances in Power Systems, for example for efficient grid integration of renewable sources. In these high-voltage, high-power application fields, a high efficiency is mandatory. In this regard, an interesting and promising development opportunity could be to make soft-switching the elementary converters of the submodules (cells), half H-bridges or full H-bridges, obtaining at the same time the advantage of increasing the switching frequency. The-Active Resonant Commutated Pole Converter (ARCP) or the Auxiliary Quasi Resonant DC-link Inverter (AQRDCL) soft-switching topologies appear adequate for this purpose. This paper is dedicated to examining these development possibilities.

A Single Switch Parallel Quasi Resonant Converter Topology for Induction Heating Application

In this paper 32 KHZ Single phase Single switch Parallel Resonant converter topology (SSPR) using power MOSFET is simulated using MATLAB simulink for the different duty cycle and the THD, Power with respect to change in duty cycle is compared . The workingcoil is the combination of R, L in parallel with C which produces the output power of 1.7KW to 3KW with variation in duty cycle at higher value in duty cycle we get less THD and more power. The operating frequency is selected nearer to the resonant frequency for the improvement performance. The experimental set up of this SSPR Inverter in the induction heating application for the domestic purpose is implemented is depicted and this validates the implementation of quasi resonant using IGBT for domestic applications.

Quasi-Resonance Signal Amplification by Reversible Exchange.

Here we present the feasibility of NMR signal amplification by reversible exchange (SABRE) using radio frequency irradiation at low magnetic field (0.05 T) in the regime where the chemical shifts of free and catalyst-bound species are similar. In SABRE, the 15N-containing substrate and parahydrogen perform simultaneous chemical exchange on an iridium hexacoordinate complex. A shaped spin-lock induced crossing (SLIC) radio frequency pulse sequence followed by a delay is applied at quasi-resonance (QUASR) conditions of 15N spins of a 15N-enriched substrate. As a result of this pulse sequence application, 15N z-magnetization is created from the spin order of parahydrogen-derived hyperpolarized hydrides. The repetition of the pulse sequence block consisting of a shaped radio frequency pulse and the delay leads to the buildup of 15N magnetization. The modulation of this effect by the irradiation frequency, pulse duration and amplitude, delay duration, and number of pumping cycles was demonstrated. Pyridine-15N, acetonitrile-15N, and metronidazole-15N2-13C2 substrates were studied representing three classes of compounds (five- and six-membered heterocycles and nitrile), showing the wide applicability of the technique. Metronidazole-15N2-13C2 is an FDA-approved antibiotic that can be injected in large quantities, promising noninvasive and accurate hypoxia sensing. The 15N hyperpolarization levels attained with QUASR-SABRE on metronidazole-15N2-13C2 were more than 2-fold greater than those with SABRE-SHEATH (SABRE in shield enables alignment transfer to heteronuclei), demonstrating that QUASR-SABRE can deliver significantly more efficient means of SABRE hyperpolarization.

Development of a modular single-phase grid-tie inverter system for fuel-cell power generation

To enhance the conversion efficiency and electrical reliability of the low-voltage fuel-cell (FC) power generation system, this paper proposes a modular single-phase grid-tie inverter system equipped with a power management and remote monitoring interface. In this system, each single power module is composed of three single-stage quasi-resonant (QR) flyback current-source inverters that are connected in parallel, and all the power modules are connected in parallel to achieve flexible power scaling and load sharing. The proposed grid-tie inverter system possesses a power management unit (PMU) and can be integrated with a home energy management system (HEMS). An experiment was conducted to verify the feasibility of the proposed concept, in which five power modules were assembled to form a 1-kW high-efficiency grid-tie inverter system, which was modulated through the PMU. The results showed satisfactory load-sharing characteristics between the parallel-connected power modules. The peak efficiency for each power module and the overall power generation system are about 94.5 and 90%, respectively. The proposed system exhibits flexible power scaling, load sharing, and high reliability.

Двухканальный драйвер силовых ключей с параллельным резонансом в цепи затвора

The well-known scheme of a one-channel power switch driver with parallel resonance in gate circuit (PRD) is considered and its merits and demerits in comparison with the standard drivers are given. A new type of PRD drivers for control of FETs, combined and composite transistors is proposed and described. The proposed driver performs opposite-phase control of two MOSFETs with induced channels and can be used in advanced static converters of a megahertz frequency range. The two-channel PRD driver has a number of advantages over the previously proposed driver schemes. In comparison with traditional drivers it allows significantly smaller gating losses and a higher switching frequency to be achieved. In comparison with quasi-resonant circuits, the two-channel PRD opens the possibility to have a considerably lower power and cost of the semiconductor amplifier. In comparison with one- channel drivers better performance characteristics and more stable operation were obtained owing to the use of a resonant-circuit three-winding coil and mutual compensation of the nonlinearity of the transistors’ input capacitances. The above-mentioned nonlinearity is compensated due to the transistor input capacities being connected in coupled resonant circuits in an opposite-phase manner. As a result, a close to a sine wave shape of the gate voltage is obtained. The duty cycle for each switch is a little bit smaller than 0.5. The use of the proposed scheme guarantees that a dead interval of time is secured between the opening instants of switches controlled by a single driver and that the system will have high noise immunity. On the other hand, the two-channel PRD driver has certain shortcomings: it features a fixed duty cycle, a comparatively long switching time, and a noticeable influence of the power circuit parameters on the system operation. In view of these circumstances, it is recommended to use PRD drivers in megahertz frequency range resonance converters with phase and discrete control modes. The functional diagram of a bridge converter with phase control and two-channel PRD drivers is presented, and recommendations on selecting its elements are given. The proposed drivers are supposed to be used mainly for constructing compact converters with a high specific power for portable devices and for electric vehicles.

A Control Strategy of a Single-phase H6-type Grid-connected Inverter with Low Harmonic Current

In order to reduce the total harmonic distortion (THD) of the grid-connected current caused by the high-frequency switching of the inverter, this paper combines the high efficiency single-phase H6-type inverter with LCL filter. The double closed-loop control method that consists of grid-connected current outer loop and capacitor current inner loop is put forward, by which a resonance peak of a low damping LCL filter is eliminated. In the grid-connected current outer loop, quasi proportion resonant (QPR) controller is adopted to overcome the steady-state error and weak anti-jamming capability in traditional PI controller. Finally, a simulation model is built in SIMULINK to verify the research. The simulation results show that, based on the single-phase H6-type inverter and LCL filter, the double closed-loop QPR control strategy can achieve the static error free tracking control of grid-connected current, which makes the system more stable and reduces the THD of grid-connected current effectively.

A High-Switching-Frequency Flyback Converter in Resonant Mode

The demand of miniaturization of power systems has accelerated the research on high-switching-frequency power converters. A flyback converter in resonant mode that features low switching losses, less transformer losses, and low switching noise at high switching frequency is investigated in this paper as an alternative to a conventional quasi-resonant (QR) flyback topology to increase power density. In order to find a compromise between magnet size, electromagnetic interference (EMI), and efficiency, the concept utilizes the resonant behavior between transformer leakage inductance and snubber capacitor to achieve near-zero-voltage switching at both turn-on and turn-off of the primary switch, low core loss due to a continuous transformer magnetizing current, and reduced EMI due to low di / dt and dv / dt values. Meanwhile, the concept uses the regenerative snubber to recycle the transformer leakage energy with two snubber diodes and one snubber capacitor. The proposed concept has been validated on a 340-kHz 65-W prototype. Compared to the conventional QR flyback converter operating at the same switching frequency, the proposed concept has 2% efficiency improvement and better EMI performance.

Modeling, Analysis and Control of Different DC-DC Converter Topologies for Photo Voltaic Emulator

This paper presents the modeling, analysis and control of different DC-DC converter topologies to emulate the photovoltaic (PV) system. A PV emulator is basically a DC-DC converter having same electrical characteristics that of solar PV panel. The emulator helps to achieve real characteristics of PV system in a better way in an environment where using actual PV systems can produce inconsistent results due to variation in weather conditions. The paper describes different types of DC-DC converters like buck, Resonant and Quasi Resonant Converter. The complete system is modelled in MATLAB<sup>®</sup> Simulink SimPowerSystem software package. The Simulation results obtained from the MATLAB<sup>®</sup> Simulink SimPowerSystem software package for different topologies under steady and dynamic conditions are analyzed and presented. An evaluation table is also presented at the end of the paper, presenting the effectiveness of each topology.