Peak System Efficiency Research Articles

A Sustainable Soil Energy Harvesting System With Wide-Range Power-Tracking Architecture

For wide-range deployment of wireless sensing nodes in power- and size-constrained Internet of Things applications, self-sustaining wireless sensors without batteries are needed. The energy supply for these ubiquitous sensing devices should harness environmental energy sources to avoid frequent battery replacement and pollution. This paper presents a new soil energy harvesting system with a power management integrated circuit (IC) for wide-range maximum power point tracking (MPPT). The output power of a soil energy cell varies widely according to the soil moisture and soil contents. To extract the maximum amount of energy from the soil, high-efficiency power management with adaptive dc–dc conversion ratios and an MPPT mechanism is essential. The proposed system is implemented with a high-efficiency dc–dc converter IC in a 0.18- ${\mu }\text{m}$ CMOS process. The design achieves a peak tracking efficiency of 90.5% in the throughput power range from 56 $\mu \text{W}$ to 1 mW at an output voltage of 3 V and system efficiency exceeding 65% over an input resistance range of the soil energy source; the peak system efficiency is 73.9%. A demonstration was undertaken of the soil energy harvesting system lighting an LED array without any chemical batteries.

Experimental study on flux mapping for a novel 84 kWe high flux solar simulator

A novel 84 kWe high flux solar simulator with six instantaneous switch gates is designed in this study. Based on the indirect measurement method, a data acquisition and control software for the flux measurement is developed. A flux measurement algorithm is accomplished based on image processing method. In order to reduce random error, the least squares method is used to fit the average radiative flux and the average gray value. Then, the indirect flux measurement error is analyzed. The total errors of radiative flux and total radiative power for high flux solar simulator with all lamps in operation are ±10.57% and ±10.63%, respectively. The radiative flux mappings of solar simulator at different planes are obtained. The experimental results show that the radiative flux mapping is consistent with the ellipsoidal Gaussian distribution. The maximum system efficiency of 84 kWe high flux solar simulator is 38.1%. The maximum peak flux is 9.3 MW/m2 at the focal plane. The maximum average radiative flux on 5 cm diameter target is 5.2 MW/m2 at +1 cm plane. For a single short-arc xenon lamp, the maximum of peak flux, radiative power and system efficiency reach 1.2 MW/m2, 2.88 kW, and 41.1%, respectively.

A Zero-Voltage-Switching, Physically Flexible Multilevel GaN DC–DC Converter

Improving the power density of a power converter has many benefits for systems integration. Aspects such as thermal management, weight, conformation to mounting locations, and the footprint of the converter all become critical factors as systems continue to scale down in size. The flying capacitor multilevel converter topology is of interest because it has characteristics which contribute to high power density. This paper presents a quasi-square-wave zero-voltage switching (ZVS) multilevel dc–dc converter. ZVS greatly reduces switching losses and enables high-frequency operation of the converter. A hardware prototype is implemented, built on a flexible polyimide substrate circuit board. Experimental results show a peak system efficiency above 98.1%, an effective switching frequency of up to 3 MHz, and a power output of 250 W.

A Watt-Level Quadrature Class-G Switched-Capacitor Power Amplifier With Linearization Techniques

A 30.1-dBm quadrature transmitter is implemented based on Class-G IQ-cell-shared switched-capacitor power amplifier (SCPA) and voltage mismatch compensation techniques for dual-supply voltage in a Class-G SCPA. For the Class-G operation in the IQ-cell-shared quadrature SCPA, a merged cell switching (MCS) technique comprising vector amplitude switching (VAS) and vector phase switching (VPS) is proposed. The VAS boosts system efficiency (SE) by enabling the Class-G operation with multiple supply voltages and the VPS conserves vector information in the merged cells that process the quadrature vectors. The linearization technique for Class-G SCPA minimizes the distortion that arises from the supply-voltage mismatches in a multiple supply-voltage system. Two SCPAs are coupled with a power combining transformer to achieve a watt-level output power. A time-domain interpolation minimizes the spectral image. The prototype SCPA, fabricated in a 65-nm CMOS, achieves peak output power and SE of 30.1 dBm and 37.0%, respectively. It achieves error vector magnitude (EVM) of −40.7 dB (−40.3 dB) and SE of 14.7% (18.3%) at an average output power of 19.5 dBm (22.5 dBm) with 802.11g 64-QAM OFDM signal with 10.6 dB peak-to-average power ratio (PAPR) (20-MHz single-carrier 256-QAM signal with 7.6-dB PAPR).

Unit-Minimum Least Power Point Tracking for the Optimization of Photovoltaic Differential Power Processing Systems

Recently, the module integrated converter and differential power processing (DPP) architecture were introduced to enable the photovoltaic (PV) power conditioning system to maintain the optimal operating condition of PV cells, such as maximum power point tracking (MPPT), even under partial shading conditions. However, the DPP architecture was found to have more room to optimize the performance of the systems, by the application of an extra extremum-seeking control, the so-called least power point tracking (LPPT) method that was introduced last year. The main idea is that most of the power from the PV modules is processed through the main-string high-efficiency nonisolation converter, and only a minimal fraction of the power that changes depending on the PV-string current is transferred through the low-efficiency bidirectional isolated DPP converters. This paper suggests a second version of the LPPT method, called unit-minimum power-distributing LPPT, which improves the first version of LPPT, called total-minimum centralized power-distributing LPPT. Instead of minimizing the total power of DPPs, the proposed LPPT minimizes the power of the DPP converter unit, which is the largest among them. Then, the system size and cost can be reduced by the proposed LPPT method, which enables the multiple DPP converters to have smaller power capacity and losses than those of the previous LPPT method. The real-time extremum-seeking algorithm employs a perturb-and-observe method, which comes from the conventional MPPT one, while the optimization process directs minimal extremity, not maximal. The peak system efficiency achieved with a 400-W prototype DPP system employing the LPPT algorithm is 96.7%.

Wireless Power Charger Based on Class E Amplifier with the Maximum Power Point Load Consideration

The construction of an electromagnetic coupling power transfer system is introduced in this paper. Considering the characteristics of the battery charger, a novel parameter design method based on the load of the maximum power transfer point is proposed. Then, the compensator, resonant circuits, and some key parameters of the electromagnetic coupler are discussed in detail by constructing a mutual inductance model to carry out impedance calculation and analysis. Coupling coefficient influenced by different magnetic circuits and coil distribution were analyzed by building a finite element model and an equivalent magnetic circuit. Moreover, impedance matching and compensation network parameters were theoretically calculated and simulated. Finally, a wireless power charger based on an open-loop class E amplifier with the maximum power point load consideration was manufactured. Simulation and experiments were done to verify the analyses, and the capability of 4.2 W power delivery at a distance of 10 mm and a peak system efficiency exceeding 72% were demonstrated.

A Coin-Battery-Powered LDO-Free 2.4-GHz Bluetooth Low-Energy Transmitter With 34.7% Peak System Efficiency

This brief reports a 2.4-GHz Bluetooth low-energy (BLE) transmitter (TX) that can operate against a coin-battery voltage discharging from 1.5 to 1 V, corresponding to a 99.2% battery capacity usage. Specifically, a class-B/C push–pull power amplifier with dual feedback control loops is proposed to dynamically adjust two gate biases, ensuring stable output power and low output HD2. The TX fabricated in 65-nm CMOS occupies a die area of 0.5 mm2 and achieves three stable power levels: $\text{P}_{{\mathbf{ out,H}}}$ (2.7 ± 0.4 dBm), $\text{P}_{{\mathbf{ out,M}}}$ (−0.1 ± 0.6 dBm), and $\text{P}_{{\mathbf{ out,L}}}$ (−2.5 ± 0.8 dBm). At $\text{P}_{{\mathbf{ out,H}}}$ , the system efficiency reaches 34.7%. The 1-Mb/s GFSK output ( ${\mathbf{ m = 0.5}}$ ) and HD2,3 comply with the BLE specifications, and the FSK error is 8.2%. A tiny demo board with an antenna, a crystal, and a coin battery (Nanfu LR44) verifies the feasibility of the TX over-the-air, achieving 27.5 h of continuous operation for a 1-dB reduction of the received power.

Split-Array, C-2C Switched-Capacitor Power Amplifiers

This paper presents a 13-b C-2C split-array (SA) multiphase switched-capacitor power amplifier (SAMP-SCPA) implemented in 65-nm CMOS. The SAMP-SCPA was designed for 16-b resolution to offer extra states for linearization/calibration using digital pre-distortion (DPD). Resolution limits for SA SCPAs are presented. The SAMP-SCPA allows for the improvement of the SCPA resolution while minimizing the impact on the input power required driving it. A prototype SAMP-SCPA, occupying 0.85 mm $\times $ 2 mm, delivers a peak output power of 24 dBm with a peak system efficiency (SE) of 40% at 1.8 GHz. When amplifying a long-term evolution (LTE) signal, the average output power and SE are 18.8 dBm and 21.6%, respectively, with an adjacent channel leakage ration (ACLR) < −30 dBc and error vector magnitude (EVM) of 2.65% rms. The increased resolution allows output power to be traded off for improved linearity and a low power mode demonstrates an EVM as low as 1% rms.

Wideband Mixed-Domain Multi-Tap Finite-Impulse Response Filtering of Out-of-Band Noise Floor in Watt-Class Digital Transmitters

A major drawback of digital transmitters (DTX) is the absence of a reconstruction filter after digital-to-analog conversion which causes the baseband quantization noise to get upconverted to radio frequency and amplified at the output of the transmitter. In high power transmitters, this upconverted noise can be so strong as to prevent their use in frequency-division duplexing systems due to receiver desensitization or impose stringent coexistence challenges. In this paper, we describe a DTX that embeds mixed-domain multi-tap finite-impulse response (FIR) filtering with programmable analog sub-sample delays within a highly linear and mismatch-resilient switched-capacitor DTX architecture. It is shown that switched-capacitor power amplifiers (SCPA) in conjunction with transformer-based power combining are ideal candidates for embedding mixed-domain FIR filtering since the near-constant source impedance of the SCPA greatly aids in linear FIR summation thereby preserving the desired noise-shaping profile. Moreover, their excellent mismatch characteristics help in ensuring precise tap weights in the FIR which enhances noise suppression. The availability of multiple taps in this architecture also allows the synthesis of FIR configurations with wide notch bandwidths (BW). Theoretical analyses of this architecture and design trade-offs related to linearity, mismatch, output power, and efficiency are discussed. The implemented 65 nm CMOS prototype exhibits a peak output power of 30.3 dBm and a peak system efficiency of 34%, and achieves a noise floor of -149 dBc/Hz over a BW of 20 MHz at an offset of 135 MHz from a 2.23 GHz carrier while transmitting a 1.4 MHz 64-QAM signal with an average output power of 22 dBm.

A Switched-Capacitor-Controlled Digital-Current Modulated Class-E Transmitter

An envelope elimination and restoration transmitter that comprises a class-E power amplifier (PA) and a digitally controlled current digital-to-analog converter (DAC) modulator are presented. A switched-capacitor DAC is designed to control an open-loop transconductor that operates as a current modulator, modulating the amplitude of the current supplied to a class-E PA. Such a topology allows for increased filtering of the quantization noise that is problematic in most digital PAs (DPA). The system measurements yield a peak output power and system efficiency (SE) of 22.5 dBm and 23.6%, respectively. When applying a local thermal equilibrium signal, the measured error vector magnitude is 3.72% and the adjacent channel leakage ratio is −30.2 dBc, while outputting 18.1 dBm at 10.6% SE.

A Multiphase Switched Capacitor Power Amplifier

This paper presents an all-digital multiphase switched capacitor power amplifier (MP-SCPA) implemented in a 130-nm CMOS. Quadrature architectures suffer reduced output power and efficiency owing to the combination of out-of-phase signals. The MP architecture reduces the phase difference between the basis vectors that are combined, and hence the output power and efficiency are greatly improved. Sixteen clocks with identical adjacent phase separations are produced by a phase generator with each phase’s relative amplitude weighted on the top plate of a capacitor array and combined on a common bottom plate, resulting in linear amplification. The MP-SCPA delivers a peak output power $P_{\mathrm{ out}}$ of 26 dBm with a peak system efficiency (SE) of 24.9%. When amplifying a long-term evolution signal at 1.85 GHz, the average $P_{\mathrm{ out}}$ and the SE are 20.9 dBm and 15.2%, respectively, with an Adjacent Channel Leakage Ratio (ACLR) < −30 dBc and error vector magnitude of 3.5% rms using a 2-D digital predistortion.

A 3-kW Wireless Power Transfer System for Sightseeing Car Supercapacitor Charge

Wireless power transfer (WPT) is the preferred charging method for electric vehicles (EVs) powered by battery and supercapacitor. In this paper, a novel WPT system with constant current charging capability for sightseeing car with supercapacitor storage is designed. First, an optimized magnetic coupler using ferrite cores and magnetic shielding structure is proposed to ensure stable power transfer and high efficiency. Compared with the traditional planar shape ferrite core coupler, the proposed magnetic coupler requires lesser ferrite material without degrading the performance of the WPT system. Second, the model of supercapacitor is applied to the WPT system and the relationship between equivalent load resistances of supercapacitor and charging time is analyzed in detail. Then, a Buck converter with proportional integral (PI) controller is implemented on the secondary side to maintain constant charging current for the variable load. Finally, the proposed design is verified by experiments. Constant charging current of 31.5 A across transfer distance of 15 cm is achieved. The peak transfer power and system efficiency are 2.86 kW and 88.05%, respectively.

Least Power Point Tracking Method for Photovoltaic Differential Power Processing Systems

Differential power processing (DPP) systems are a promising architecture for future photovoltaic (PV) power systems that achieve high system efficiency through processing a faction of the full PV power, while achieving distributed local maximum power point tracking (MPPT). In the PV-to-bus DPP architecture, the power processed through the DPP converters depends on the string current, which must be controlled to minimize the power processed through the DPP converters. A real-time least power point tracking (LPPT) method is proposed to minimize power stress on PV DPP converters. Mathematical analysis shows the uniqueness of the least power point for the total power processed through the system. The perturb-and-observe LPPT method is presented that enables the DPP converters to maintain optimal operating conditions, while reducing the total power loss and converter stress. This work validates through simulation and experimentation that LPPT in the string-level converter successfully operates with MPPT in the DPP converters to maximize output power for the PV-to-bus architecture. Hardware prototypes were developed and tested at 140 and 300 W, and the LPPT control algorithm showed effective operation under steady-state operation and an irradiance step change. Peak system efficiency achieved with a 140-W prototype DPP system employing LPPT is 95.7%.

Determination of some psychotropic drugs in serum and saliva samples by HPLC-DAD and HPLC MS

A simple, rapid and sensitive HPLC-DAD method has been developed and validated for the simultaneous determination of seven psychotropic drugs (risperidone, citalopram, clozapine,quetiapine, levomepromazine, perazine and aripiprazole) in human serum or saliva samples. The chromatographic analyses were performed on a XSELECT CSH Phenyl-Hexyl column with a mobile phase containing methanol, acetate buffer at pH 3.5 and 0.025mL−1 diethylamine. The influence of concentration of methanol in injection samples and injection volume on peak symmetry and system efficiency was examined.The full separation of all investigated drugs, good peaks' symmetry and simultaneously high systems efficiency were obtained in applied chromatographic system. The method is suitable for the analysis of investigated drugs in human plasma or saliva for psychiatric patients for control of pharmacotherapy, particularly in combination therapy. HPLC–MS was applied for verification of the presence of drugs and their metabolites in serum and saliva samples from patients.

A High-Density, High-Efficiency, Isolated On-Board Vehicle Battery Charger Utilizing Silicon Carbide Power Devices

This paper presents an isolated on-board vehicular battery charger that utilizes silicon carbide (SiC) power devices to achieve high density and high efficiency for application in electric vehicles (EVs) and plug-in hybrid EVs (PHEVs). The proposed level 2 charger has a two-stage architecture where the first stage is a bridgeless boost ac-dc converter and the second stage is a phase-shifted full-bridge isolated dc-dc converter. The operation of both topologies is presented and the specific advantages gained through the use of SiC power devices are discussed. The design of power stage components, the packaging of the multichip power module, and the system-level packaging is presented with a primary focus on system density and a secondary focus on system efficiency. In this work, a hardware prototype is developed and a peak system efficiency of 95% is measured while operating both power stages with a switching frequency of 200 kHz. A maximum output power of 6.1 kW results in a volumetric power density of 5.0 kW/L and a gravimetric power density of 3.8 kW/kg when considering the volume and mass of the system including a case.

Flat-Panel Compatible Photovoltaic Energy Harvesting System

In this work, an amorphous silicon (a-Si:H) thin-film transistor (TFT) circuit designed for charging of intermediary energy storage devices using photovoltaic (PV) solar cell arrays is demonstrated and analyzed. The proposed circuit combines the functionality of a linear DC-DC voltage regulator and a maximum power point tracking unit (MPPT). The circuit reduces the dependence of the charging voltage on light intensity and offers relatively stable operation when electrically stressed. The effects of light intensity and the PV array size on the system and circuit efficiencies as well as on PV utilization are investigated. A peak system efficiency of 18% is demonstrated. Although this is significantly lower than state-of-the-art switch mode DC-DC voltage regulator and MPPTs, the combined use of thin-film technology and low fabrication temperatures (below 150 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C) allow its integration within a wide range of mobile devices, making it an attractive solution for energy harvesting systems.

Experimental investigation of solar powered diaphragm and helical pumps

For several years, many types of solar powered water pumping systems were evaluated, and in this paper, diaphragm and helical solar photovoltaic (PV) powered water pumping systems are discussed. Data were collected on diaphragm and helical pumps which were powered by different solar PV arrays at multiple pumping depths to determine the pumping performance, efficiency, and reliability of the different systems. The highest diaphragm pump hydraulic efficiency measured was ∼48%, and the highest helical pump hydraulic efficiency measured was ∼60%. The peak total system efficiency (e.g. solar radiation to pumped water) measured for the diaphragm and helical pumps were ∼5% and ∼7%, respectively (based on PV modules with ∼12% efficiency). The daily water volume of the three-chamber high head diaphragm pump performed better than the dual-chamber high head diaphragm pump (∼5 to ∼100% depending on PV array input power and pumping depth). Use of a controller was shown to improve the quad diaphragm pump performance below a solar irradiance of 600 W/m 2 (20 m head) to 800 W/m 2 (30 m head). While diaphragm pumps made mostly of plastic demonstrated similar to much better pumping performance than diaphragm pumps made with a high proportion of metal, the metal pumps demonstrated a longer service life (>2 years) than the plastic pumps service life (<2 years). Helical pumps analyzed in this paper were capable of deeper pumping depths and usually demonstrated a longer service life than the diaphragm pumps that were analyzed.

GE SECA Prototype System Development and Testing

This paper summarizes the prototype system development and testing under Solid State Energy Conversion Alliance (SECA) Solid Oxide Fuel Cell Program. There were two generations of the SECA prototype systems developed. The Gen 1 prototype system met or exceeded the SECA requirements over a 1720h test, achieving 41% peak system efficiency and 5.4 kW peak net power. The Gen 2 prototype achieved 49.6% peak efficiency and 5.6 kW peak net power over a 120h commissioning test. The Gen 2 prototype system has been delivered to National Energy Technology Laboratory (NETL) for final testing.

P.2.153 Typical-to-atypical versus atypical-to-typical antipsychotic switching strategies and visual evoked potentials (VEPs) in paranoid schizophrenia

A simple, rapid and sensitive HPLC-DAD method has been developed and validated for the simultaneous determination of seven psychotropic drugs (risperidone, citalopram, clozapine,quetiapine, levomepromazine, perazine and aripiprazole) in human serum or saliva samples. The chromatographic analyses were performed on a XSELECT CSH Phenyl-Hexyl column with a mobile phase containing methanol, acetate buffer at pH 3.5 and 0.025 mL−1 diethylamine. The influence of concentration of methanol in injection samples and injection volume on peak symmetry and system efficiency was examined.The full separation of all investigated drugs, good peaks' symmetry and simultaneously high systems efficiency were obtained in applied chromatographic system. The method is suitable for the analysis of investigated drugs in human plasma or saliva for psychiatric patients for control of pharmacotherapy, particularly in combination therapy. HPLC–MS was applied for verification of the presence of drugs and their metabolites in serum and saliva samples from patients.

EXPERIMENTAL STUDY OF A GLAZED SOLAR COLLECTOR/REGENERATOR OPERATED UNDER A HUMID CLIMATE

The performance of a glazed solar collector/regenerator (C/R) for an open-cycle absorption solar cooling system using aqueous lithium chloride solution as the working fluid was tested at Kaohsiung, Taiwan under a humid climate. The results indicate that the peak system efficiency is 15.2% and the day-average efficiency is 14.1%. The effects of parameters on the C/R performance are studied, and the non dimensional correlations for heat and mass transfer were given.