ANALYSIS OF ZERO-VOLTAGE QUASI-RESONANT BOOST DC-DC CONVERTER

The zero-voltage quasi-resonant boost switching DC-DC converter has been inves-tigated by using the time averaging equivalent circuit approach of periodically switching linearnetworks.The DC steady state and AC small signal characteristics of the converter are also given.

Topographicaly Forced Thre-Wave Quasi-Resonant and Non-Resonant Interactions among Barotropic Rossby Waves on an Infinite Beta-Plane

In this paper, we first apply the assumption h=εh' of topographic variation ( h is the nondimensional topographic height and is a small parameter) to obtain nonlinear equations describing three-wave quasi-resonant and non-resonant interactions among Rossby waves for zonal wavenumbers 1—3 over a wavenumber-two bottom topography (WTBT). Some numerical calculations are made with the fourth-order Rung-Kutta Scheme. It is found that for the case without topographic forcing, the period of three-wave quasi-resonance (TWQR) is found to be independent of the zonal basic westerly wind, but dependent on the meridional wavenum ber and the initial amplitudes. For the fixed initial data, when the frequency mismatch is smaller and the meridional wavelength is moderate, its period will belong to the 30-60-day period band. However, when the wavenumber-two topography is included, the periods of the forced quasi-resonant Rossby waves are also found to be strongly dependent on the setting of the zonal basic westerly wind. Under the same conditions, only when the zonal basic westerly wind reaches a moderate extent, intraseasonal oscillations in the 30-60-day period band can be found for zonal wavenumbers 1-3. On the other hand, if three Rossby waves considered have the same meridional wavenumber, three-wave non-resonant interaction over a WTBT can occur in this case.When the WTBT vanishes, the amplitudes of these Rossby waves are conserved. But in the presence of a WTBT, the three Rossby waves oscillate with the identical period.The period, over a moderate range of the zonal basic westerly wind, is in the intraseasonal, 30-60-day range.

Quasi-resonant cavity enhanced photodetector with a subwavelength grating

We designed a tunable wavelength-selective quasi-resonant cavity enhanced photodetector(QRCE-PD)based on a high-contrast subwavelength grating(SWG).According to simulation results,its peak quantum efficiency is 93.2%the 3 dB bandwidth is 33.5 GHz,the spectral linewidth is 0.12 nm,and the wavelength-tuning range is 28 nm(1536-1564 nm).The QRCE-PD contains a tunable Fabry-Perot(F-P)filtering cavity(FPC),a symmetrical SWG deflection reflector(SSWG-DR),and a built-in p-i-n photodiode.The FPC and the SSWG-DR form an equivalent multi-region F-P cavity together by multiple mutual mirroring,which makes the QRCE-PD a multi-region resonant cavity enhanced photodetector.But,QRCE-PD relies on the multiple-pass absorption enhanced effect to achieve high quantum efficiency,rather than the resonant cavity enhanced effect.This new photodetector structure is significant for the application in the dense wavelength division multiplexing systems.

Interaction between Planetary-Scale Diffluent Flow and Synoptic-Scale Waves During the Life Cycle of Blocking

In this paper, a new transient forced quasi-resonant triad interaction theory in a beta channel is proposed to investigate the interaction between planetary-scale diffluent flow composed of zonal wavenumbers 1-3 and synoptic-scale waves produced continuously by a synoptic-scale vorticity source fixed upstream of an incipient blocking region during the life cycle of blocking. It is shown that the superposition of initial three Rossby waves for zonal wavenumbers 1 （monopole）, 2 （dipole）, and 3 （monopole）, which permit triad quasi-resonance, can represent an incipient blocking event. The synoptic-scale eddies may act to amplify the incipient blocking and to excite a blocking circulation with a strong meander, whose flow pattern depends on the initial amplitudes of the planetary waves and both the intensity and location of preexisting synoptic-scale waves. The onset （decay） of the planetary-scale split-flow blocking is mainly represented by a strong increase （decrease） in the amplitude of the zonal wavenumber 2 component, having a dipole meridional structure related to the preexisting synoptic-scale eddies. The typical persistence time of the model blocking was of about 20 days, consistent with observations of blocking patterns. In our model, isolated asymmetric dipole blocking is formed by synoptic-scale waves. The instantaneous fields of total streamfunctions exhibit a remarkable resemblance to the synoptic maps observed during the life cycle of blocking. During the onset stage, the synoptic-scale waves are enhanced and split into two branches around the blocking region due to the feedback of the amplified blocking, in agreement with the observed changes of synoptic-scale waves in real blocking events. In addition, a diagnostic case study of blocking is presented to confirm the forced quasi-resonant triad interaction theory proposed here.

QUASI-RESONANCE OF BAROCLINIC ATMOSPHERIC WAVES AND EXTRATROPICAL LOW-FREQUENCY OSCILLATION

In operating the quasi-geostrophic two-layer model,the quasi-resonance occurs possibly in two cases:(1)pure barotropic waves;(2) two baroclinic and one barotropic waves.For case (2),we find the analytical solution of triad amplitude of quasi-resonance and approximate expression for the period of wave energy variation.Both the approxi- mate expression and numerical calculation indicate that this period tends to approach the period (2πε)/(△ω) of the quasi-resonance frequency mismatch △ω itself for the baroclinic atmosphere than for the barotropic atmosphere.Phys- ically,there is a feedback mechanism between the wave phase and amplitude,and the slowly varying phase difference be- tween the barotropic wave and the baroclinic wave causes the conversion of kinetic energy and available potential energy,which gives rise to the wave-related low-frequency oscillation alternatively strengthening and weakening with the oscillation period identical to the above approximate formula.For △ω～(0.1-0.02) 0(ωj),the averaged energy peri- od is 12-43 days and when △ω=0,i t is 366 days.Therefore,the occurrence of frequency mismatch △ω is probably a new important mechanism for the formation of extratropical low -frequency oscillation in baroclinic atmosphere as well.

QUASI-RESONANCE OF BAROTROPIC ATMOSPHERIC WAVE MOTION AND MID-LATITUDE LOW-FREQUENCY OSCILLATION

It is proved, based on the quasi--geostropic barotropic vortex equation and the quasi-resonance conditions K1+ K2+ K3=0 and ω1 +ω1 +ω3 =Δω, that the analytic solution ofthe 3--wave amplitude of quasi--resonance is an elliptical function. The approximate expressionfor the periodic variation of wave energy is thus obtained under certain conditions. Boththe approximate expression and numerical calculation indicate that the period of energyvariation approaches the period 1/Δω corresponding to the quasi--resonance frequency biasΔω itself. When Δω～（0.1--0.025）o（ωj）, the energy variation period is 12---46 days andwhen Δω=0, it is 25--568 days. Therefore, the occurrence of frequency bias Δω is probablya new important mechanism for the formation of mid-latitude low--frequency oscillation.This also accounts for the result of the numerical test Egger （1978） did on blocking causedby the resonance of two topographic stationary waves and one free slow wave.

Mode-varying Cell Equalizer Based on Interleaved Parallel Multiple Transformers

In the application of long series batteries,there is always the phenomenon that multiple cells in a pack are unbalanced simultaneously.In view of this situation,a modevarying cell equalizer topology based on interleaved parallel multiple transformers is proposed in this paper.Every unit in this equalizer can freely switch between LLC resonance mode and 3-state LC quasi-resonance mode.The boosting effect of LLC structure is used to reduce the number of transformer’s total turns.When multiple equalizer units need to work in LLC mode simultaneously,interleaved parallel technology is used to limit secondary side equalization current ripple for long-term protection of battery life.A prototype was designed and built to validate the effect of a closed loop LLC mode control algorithm with a state-of-charge(SOC)based equalization scheme selection strategy.Experimental results including up to 88.52%efficiency in LLC mode with 90.7%efficiency in 3-state LC mode,and minute level balancing time show the proposed topology demonstrates excellent balancing performance.

A multimode digital controller IC for flyback converter with high accuracy primary-side feedback

A digital controller IC for the flyback converter with primary-side feedback is proposed. The controller is used for adapter charger or LED driver applications. To obtain high accuracy for the primary-side feedback, a digital primary-side sensing technology is adopted, which can auto-track the knee point of the primary auxiliary winding voltage. Furthermore, an internal digital compensator eliminates the need for external loop compensation components while achieving excellent line and load regulation. The controller could output both constant voltage and constant current depending on the load current. Pulse width modulation and pulse frequency modulation are used in constant voltage mode while quasi-resonant control is used in constant current mode. The digital controller is validated by using FPGA.

Numerical study of nonlinear interactions of bi-chromatic progressive deep-water waves

This paper proposes a 3-D non-hydrostatic free surface flow model with a newly proposed general boundary-fitted grid system to simulate the nonlinear interactions of the bi-chromatic deep-water gravity waves.First,the monochromatic bidirectional and bi-chromatic bidirectional waves of small wave steepness are successively simulated to verify the abilities of the numerical model.Then,a series of bi-chromatic progressive waves of moderate wave steepness and different crossing angles are simulated and analyzed in detail.It is found that if the crossing angle is close to or smaller than the resonant angle,apparent discrepancies are observed among the numerical results,the linear wave theory,and the steady third-order theory.Otherwise,the three solutions coincide well.Through analysis,it is concluded that the discrepancies are caused by the third-order quasi-resonant interactions between the bi-chromatic progressive waves.Such interactions not only could modify the wave spectrum,but could also change the wave shape patterns.