A multioutput LLC-type parallel resonant converter

When an LLC-type parallel resonant converter (LLC-PRC) operates above resonant frequency, the switching transistors can be turned off at zero voltage. Further study reveals that the LLC-PRC possesses the advantage of lower converter voltage gain as compared with the conventional PRC. Based on the analytic results derived, a complete set of design curves from which a systematic design procedure is developed is obtained. Experimental results from a 150-W, 150-kHz, multioutput LLC-type PRC power supply are presented     

Current distribution control for parallel connected converters. II

For pt.I, see ibid., vol.28, no.3, p.829-840 (1992). In the central-limit control (CLC), the multiloop controls are employed to regulate the output voltage and track the central weighted current, thus equalizing the output current of each converter module (CM). The current distribution error (CDE) between the output current of each CM is used as a criterion in judging system performance. The prediction and simulation results of this control scheme are illustrated. When incorporated with the maximum current limit, the proposed control method can determine the number of required converters in the active state for each load condition. As a result, the efficiency of a system can be increased significantly. A comparison between the performances of the system under master-slave control (MSC) and CLC is given     

Simulation considers the human factors

Human factors aspects of flight simulation design at McDonnell Douglas are considered. Modeling approaches are examined and testing with pilots and cockpits is described.     

Noise analysis of a digital tanlock loop

The noise performance analysis of a nonuniform digital phase-locked loop (DPLL), called the digital tanlock loop (DTL), is investigated by both analytic and computer-simulation methods. The results are presented in terms of phase error probability mass function and mean time to skip cycle versus input signal-to-noise ratio (SNR). These results are compared to the ones obtained with the conventional sinusoidal DPLL loop (DPLL). It is found that, for low-to-moderate input SNR, the DTL has only a slight improvement over the DPLL. The DTL, however, has larger linear characteristics than the conventional DPLL, which makes it attractive for applications that require an increased tracking range or as a first stage in carrier tracking systems based on optimum estimation procedures such as a Kalman smoother     

Calculation of resonance current in high-frequency series-resonanceDC-DC converters

A method to calculate the resonance current in high-frequency series-resonant DC-DC converters is presented that includes the effect of the reverse-bias capacitance of output rectifiers and that of the primary inductance of the output transformer. A computer program developed as a tool to determine the amplitude of the resonance current for any given input and output conditions is also discussed. The results of the computer calculations agree well with experimental measurements     

The plasma Environment of Mars

Space Science Reviews -     

Radar: The Cassini Titan Radar Mapper

The Cassini RADAR instrument is a multimode 13.8 GHz multiple-beam sensor that can operate as a synthetic-aperture radar (SAR) imager, altimeter, scatterometer, and radiometer. The principal objective of the RADAR is to map the surface of Titan. This will be done in the imaging, scatterometer, and radiometer modes. The RADAR altimeter data will provide information on relative elevations in selected areas. Surfaces of the Saturn’s icy satellites will be explored utilizing the RADAR radiometer and scatterometer modes. Saturn’s atmosphere and rings will be probed in the radiometer mode only. The instrument is a joint development by JPL/NASA and ASI. The RADAR design features significant autonomy and data compression capabilities. It is expected that the instrument will detect surfaces with backscatter coefficient as low as −40 dB.RADAR Team LeaderThis revised version was published online in July 2005 with a corrected cover date.     

Development of three-phase switch-mode rectifier using single-phase modules

This paper presents a three-phase (3/spl phi/) switch-mode rectifier (SMR) consisting of three 1 /spl phi/ SMRs, two center-tapped autotransformers and three changeover switches. The ac input sides of three modules are /spl Delta/-connected, and their dc output sides are connected in parallel. As any one module fault occurs, the remaining two modules becomes modified T-connected and continuously perform three-phase rectification with good line drawn power quality. When two constituted 1/spl phi/ modules are faulted, the proposed 3/spl phi/ SMR will be operated as 1/spl phi/ SMR. The quantitative and robust voltage regulation controls for the developed SMR are made to consider the effects of changes of system parameters, operating condition, and number of connected modules.     

Phase modulated DGPS transmitter implemented with a clamped-mode resonant converter

A clamped-mode resonant converter (CMRC) is proposed to be used as a transmitter which broadcasts correction signals in a differential Global Positioning System (DGPS). The digital information of the DGPS modulates the carrier with different modulation methods minimum shift keying (MSK) (recommended for the marine radiobeacon band), stepped binary phase shift keying (S-BPSK) and BPSK. The first two methods allow keeping the converter's operation in soft switching mode. Extensive trials under impedance mismatch and modulation conditions confirm that the soft switching mode is preserved.     

Influence of a surface tension minimum as a function of temperature on the marangoni convection

Aqueous long chain alcohol solutions have a surface tension which presents a minimum as a function of the temperature. At this particular temperature, the dimensionless Marangoni number is vanishing. It is thus expected that around the temperature of the minimum, Marangoni Convection would be slowered with a convective pattern deeply modified. An experiment to be performed in microgravity during the Texus 8 flight is described.