A DC/DC Converter for ISDN Terminals

Changes of maximal power output of lower extremity during a decathlon

This paper presents a PV DC/DC converter which has high efficiency at low output power. The factors that influence the efficiency are analyzed firstly. On the basis of the analysis, a converter base on interleaved multiple-phase buck converter is proposed. By controlling the number of the phases that is active and the angle shift of the PWM carrier between the active phases, the converter can operates near the point with highest efficiency regardless the variation of output power. High efficiency can be obtained at both full output and low output power, which may increase the energy capture from the PV cell. Analysis, design and implementation of the converter are presented in detail. Tested results show an obvious improvement of the efficiency at low output power, which ratifies the validity of proposed topology and control strategy in PV DC/DC converter application.

Digital cellular telephone interaction with implantable cardioverter-defibrillators.

A nonlinear capacitance-compensation technique is developed to help improve the linearity of CMOS class-AB power amplifiers. The method involves placing a PMOS device alongside the NMOS device that works as the amplifying unit, such that the overall capacitance seen at the amplifier input is a constant, thus improving linearity. The technique is developed with the help of computer simulations and Volterra analysis. A prototype two-stage amplifier employing the scheme is fabricated using a 0.5-/spl mu/m CMOS process, and the measurements show that an improvement of approximately 8 dB in both two-tone intermodulation distortion (IM3) and adjacent-channel leakage power (ACP1) is obtained for a wide range of output power. The linearized amplifier exhibits an ACP1 of -35 dBc at the designed output power of 24 dBm, with a power-added efficiency of 29% and a gain of 23.9 dB, demonstrating the potential utility of the design approach for 3GPP WCDMA applications.

Based on an analog-gain control bias circuit (AGBC), a dynamic and fixed bias-controlled InGaP/GaAs HBT MMIC power amplifier module (PAM) is designed for code-division multiple-access (CDMA) and advanced mobile-phone service (AMPS) handset applications. The proposed AGBC effectively improves the power-added efficiency (PAE) of a power amplifier (PA) over a wide range of output power while satisfying the CDMA/AMPS linearity requirements. The PA gain slope with respect to AGBC mode-control voltage is about 12 dB/V. The measured average current of this AGBC PA is reduced by 64% compared to a standard PA. The AGBC PA exhibits a 28 dB power gain, a 45% PAE, and a -49 dBc adjacent channel power ratio (ACPR) at 28 dBm output power with a fixed mode-control voltage.

Main task of power semiconductor converter is transfer of electrical energy from its input to the output and to the load. This energy flow is provided by control of the switching process of one or more semiconductor devices. Based on converter application it is necessary to choose correct control algorithm for selected switching frequency of converter. Algorithm itself has to be utilized with suitable hardware platform, whereby through the set of instructions the turn on and turn of control pulses are generated. Control system also has to secure other important functions for secondary processes. Nowadays a huge number of converter topologies exists, whereby each type should be suited for different conditions of use. For example uninterruptible power supply must generate constant output voltage with constant frequency and constant amplitude for wide range of output power. Converters for electric drive applications have to control their speed through generation of three phase voltage system with configurable amplitude and speed. From mentioned above it is clear to say that for each topology of power converter, the different type of control modulation (PWM Pulse Width Modulation, PSM Phase Shift Modulation, FM Frequency Modulation) and different structure of regulator has to be used. Therefore selection of suitable control system depends on number of various factors, which are output power of converter, type of switching devices, type of load, possibility of hardware implementation and ways of switching. In the field of DC/DC converters for switching power supplies, the main focus is on implementation of digital control, which means use of microcontrollers or DSP with implemented control algorithms and functions for communication with user as well. Analog control systems are well known and its design procedure is mastered, so it is easy to convert analog (continuous) controller into discrete and consequently implementing in microcontroller and DSP. But this approach ignore sample and hold effect of A/D converter and computing time of microprocessor. For proper discrete controller design, the method named direct digital design can be used. This method uses transfer function of converter in discrete form, including effect of sampling and computation delay. For controller design purposes, transfer function of converter is necessary. This transfer function is based on model of power stage of controller. For PWM converters such as buck, boost, etc. the averaging method is widely used, but for new resonant topologies such as LLC converter, with this averaging method, the control to output transfer function cannot be used. In this chapter, new simulation based method for obtaining the transfer function of converter is discussed. This method uses MATLAB and OrCad PSPICE environments for

Introduction: Although soccer matches require players to perform repetitive power-related abilities, the impact of lower-body strength and power asymmetry on sprint and change of direction (COD) performance receives little attention. Therefore, this study aimed to establish the relationship between lower limb power, sprint, and change of direction (COD) performance. In addition, the relationship between lower limb power asymmetry and the above mentioned running tests was determined. Material and Methods: Twenty-four male soccer players from First Polish League (age = 24.8 ±8.2 years, body mass = 77.4 ±16.9kg, body height=179.5 ±14.5cm, soccer training experience = 10 ± 1.5years) took part in the study. To examine the relationship between linear sprint, lower limb muscle power, and COD performance (time and deficit), the following tests were performed: 5-and 20-m linear sprint, leg press exercise, and two 20-m COD sprints (“COD90” and “L” test). Result: Pearson correlation coefficients didn’t show any statistically significant relationship between lower limb power and linear sprint speed as well as COD performance. The results indicate that the considered variables are independent physical characteristics. Conclusion: Relative lower limb-power output and low level of mean inter-limb asymmetry in power output does not affect 5- and 20-m linear sprint time and COD performance with 90° turn.

This brief presents a three-way Doherty power amplifier (DPA) with a symmetric structure in terms of the output power capacities between the carrier and peaking amplifiers for high efficiency and linearity. Based on the analysis for the efficiency peak at the output power back-off, a symmetric structure was adopted to have higher overall efficiency for the modulated signal. Through the optimized bias condition for the two peaking amplifiers, the proposed three-way DPA can be linearized in the wide output power range. To validate the proposed scheme, a three-way DPA was designed and implemented using a 60 W GaN-HEMT for the carrier amplifier and two 30 W GaN-HEMTs for the peaking amplifiers. Using a 2.14 GHz long-term evolution downlink signal with a peak-to-average power ratio of 6.5 dB, the implemented symmetric three-way DPA exhibited a drain efficiency (DE) of 33.7% and an ACLR of -38 dBc at an average output power of 41.4 dBm. Compared to the condition with the same bias for the peaking amplifiers, the DE and average output power were improved by 8.0% and 2.4 dB for the given ACLR of -38 dBc, respectively.

Inductive power transfer (IPT) systems in high-power transport applications are often required to operate under highly variable conditions, including a wide range of coupling and output power. For classical controllers, a fixed gain is selected to ensure the system stability in the full range of operation, which poses a challenge to the dynamic performance of the system with different working conditions. This paper presents a primary-side gain-scheduled controller for inductive battery charging systems with the sub-resonant frequency control to significantly improve the system dynamic response. The output power and dynamic coupling of IPT systems with the sub-resonant frequency control are estimated in real-time by using only the information on the primary side. The parameters of the gain-scheduled controller are then determined by the power reference value and estimated coupling, to ensure the rapid response and stability of the system. Moreover, the risk of instability and failure caused by dual-side communication in closed-loop power control is avoided. Effectiveness and feasibility of the proposed method are validated by simulation and experimental results from a small-scale laboratory prototype.

To correlate radiant warmer bed power output with state of hydration in the critically ill infant, warmer power input was measured by a wattmeter and recorded by an on-line computer every 5 sec for 2 periods of 8-24 h each in 11 newborns with respiratory distress syndrome (mean birth weight 1.42 kg, mean gestational age 31.4 weeks). The 2 periods were compared to define a high and a low radiant power period. Fluid intake and urine output, urine and serum osmolalities, serum electrolytes, and free water clearance during each study period (high vs low radiant power) were also compared. Mean radiant power density received during periods of high radiant power output (8.93 mw/cm2) was significantly greater than during periods of low radiant power output (7.85 mw/cm2, p less than 0.001). Mean urine osmolality and fluid intake to output ratio were also significantly increased during periods of high radiant power density. There was a trend toward increased serum osmolality and decreased free water clearance during periods of high radiant power; however, these differences were not significant. This study suggests that prospective measurement of radiant power density delivered to critically ill newborns may be clinically significant in predicting an infant's state of hydration.

This paper proposes a half bridge CLL resonant DC-DC converter for wide output power range applications. This topology can achieve zero-voltage switching at entire load and zero-current switching for output rectifiers. The characteristics of the CLL resonant DC-DC converter are analyzed firstly. Then the design considerations for CLL resonant DC-DC converters based on wide output power range are introduced. An 150W CLL resonant converter prototype is built to verify the circuit performance with good performances on flat efficiency, narrow switching frequency range for wide output power range application at both 75V & 150V output voltage from 10% output current to 100 % output current.

Rapid advancements in embedded memory technologies have opened the market to a wide range of low power computing applications, such as MCUs and Internet-of-Things (IoT). Innovative solutions, such as Edge computing, where data is stored and processed close to the application, have been proposed as a cost and energy-effective solution. STT-MRAM technology is an attractive candidate for edge computing memory owing to its high endurance (> 1012 cycles), negligible leakage and non-volatility [1-2]. To enable adoption of eMRAM in low power applications, low active power consumption at operating frequencies ≤ 50 MHz is desirable. Reduction in the write power consumption is possible by materials engineering the free and reference layers in conventional MTJ stacks to improve switching characteristics [3, 4] and RA engineering to reduce switching voltages (Vsw) [3]. Unfortunately, Jsw improvement has often come at the cost of a lower Δ, which is unsuitable for the targeted application.An alternative approach to minimizing Jsw is to incorporate two reference layers (RLs) and MgO barriers on either side of the free layer (FL), also known as Double-MTJ (DMTJ) STT-MRAM [4] (Fig. 1a). A critical requirement is the anti-parallel alignment of the RLs which leads to a ‘doubling’ of the total spin torque. However, this approach suffers challenges in processing (two setting fields), TMR performance, RA control, stray field control, degraded retention times and back-end-of-line (BEOL) compatibility [5]. Thus, to demonstrate the feasibility of DMTJ STT-MRAM the following challenges must be addressed: Δ improvement, offset control (μoHoffset < 0.1*μoHc), read/write optimization (TMR>100%, Jsw < 3 MA/cm2), and BEOL compatibility. In this work, we demonstrate device-level performance with full stray field compensation, best-in-class switching (Jsw) and retention (Δ) exceeding 10 years.To achieve BEOL compatibility and compensated stray fields, a 400 °C SAF-SAF design was enabled. Both the bottom-pinned and top-pinned halves of the DMTJ stack employed a synthetic antiferromagnet (SAF) design on either side of the FL. Figure 1(a, b) illustrates the stack design alongside a blanket M-H loop. The challenges involved in the design and demonstration of a 400 °C-compatible top-pinned SAF will be discussed in this work. This includes optimization of the SAF material stack design for annealing and stray field control. The successful demonstration of the SAF-SAF design is shown in the device R-H loops of CD = 80 nm devices where μ0Hoffset ~ 0 mT (Fig. 2a). Figure 2b shows the switching current density (Jsw) trends from 125 devices as a function of pulse-width. An average Jsw = 2.7 MA/cm2 at 50 ns is observed on devices with Δ = 82 kBT and TMR ~ 100%. In addition, WER curves demonstrating 1ppm error-free switching, and a wide switching-breakdown margin of ~0.7 VDC will also be presented. These performance metrics clearly exhibit the importance of the SAF-SAF design in achieving manufacturable DMTJ STT-MRAM devices, thus making it ready for implementation in low power applications. **

During the last years, several attempts have been carried out to provide clean energy storage as an alternative to overcome the energy demand. Vanadium redox flow batteries (VRFBs) appear as a suitable device that converts the chemical energy present in the electrolyte into electrical energy in a noiseless and clean manner. In the mentioned device, the electrolyte is polarized by using renewable energy, and later the stored energy is used in several applications from mobile to stationary scenarios. There are two fundamental design parameters to be considered in the sizing of a VRFB: the state of charge (SoC), and the electrolyte volume. The mentioned parameters are related to two independent parameters of great importance, the energy consumption per unit of time (power delivered by the device), and the amount of energy that can be stored in the system (energy capacity).The purpose of the current study is, based on collected data and theoretical approximations, analyze the SoC and the required electrolyte volume for several applications. To estimate the SoC for the different VRFB, a Nernst-modified equation is used. In this case, the number of cells was a key part of achieving the desired results. A correction factor (λ) was introduced to visualize the trend of the generated curve family in a better manner. On the other hand, to calculate the volume of electrolyte, an equation derived from the definition of electric charge is implemented. Similarly, due to the power applications range covering the study, a correction factor (γ) was also introduced. Considering the obtained results, as the correction factor increases the load state in the system will tend to present higher values of open circuit voltage and nevertheless constant values of load state. Based on the energy capacity calculations, and considering common vanadium concentrations among the electrolytes, it was found that the higher the vanadium concentration the required electrolyte volume will tend to be minor. In addition, on a large scale, there is a greater convergence of the required electrolyte volume to values greater than 10 000 m3. Figure 1. Trend of the open circuit voltage (OCV) when the state of charge (SoC) is increasing. Due to the wide range of output power analyzed in the current study, all the OCV presented values have been determined by using a correction factor (λ). Figure 1

Gyrotrons operating in the millimeter and submillimeter wavelength ranges are the promising sources for applications that are requiring good spectral characteristics and a wide range of output power. We report the precise measurement results of gyrotron spectra. Experiments were conducted using a 140-GHz long-pulse gyrotron that is developed for the dynamic nuclear polarization/nuclear-magnetic-resonance spectroscopy at the Massachusetts Institute of Technology. Transient downshift of the frequency by 12 MHz with a time constant of 3 s was observed. After reaching equilibrium, the frequency was maintained within 1 ppm for over 20 s. The coefficient of the frequency change with cavity temperature was -2.0 MHz/K, which shows that fine tuning of the gyrotron frequency is plausible by cavity-temperature control. Frequency pulling by the beam current was observed, but it was shown to be masked by the downward shift of the gyrotron frequency with temperature. The linewidth was measured to be much less than 1 MHz at 60 dB relative to the carrier power [in decibels relative to carrier (dBc)] and 4.3 MHz at 75 dBc, which is the largest dynamic range to date for the measurement of gyrotron linewidth to our knowledge.

The capability of a power plant to operate at a wide range of output power is essential for initial commissioning and normal maintenance. Critical physics issues related to operating a tokamak fusion reactor at fractions of its rated power are explored, and methods for power control are identified. Analysis is carried out with a steady-state, profile-dependent, zero-dimensional power balance model of the plasma, in which several empirical transport scalings appropriate to tokamaks are used. It is found that reactor operation depends strongly on the confinement model, the plasma beta limit, and the effect of alpha power on transport. Parametric calculations indicate that density, auxiliary heating power, and an effective external confinement control mechanism are the key control elements, and burn control is required in most cases. Transition between power plateaus is facilitated by operating in the hybrid transformer mode. In general, the impact of fractional power operation on full-power reactor designs appears to be small.