Wide Output Range Research Articles

High Efficiency LLC Resonant Converter With Wide Output Range of 200–1000 V for DC-Connected EVs Ultra-Fast Charging Stations

DC-connected ultra-fast chargers consist of isolated DC/DC converter modules to provide the required charging profile. This paper proposes a charging module that interfaces with a fixed voltage DC-bus and covers a wide variety of electric vehicles (EVs) with battery voltages ranging from 200 to 1000 V. DC/DC converters for EVs charging has been discussed several times in the literature, however the DC-connected structure with fixed DC-bus voltage is rarely considered. This paper proposes a full-bridge LLC DC/DC converter module with a configurable secondary. This configuration extends the converter’s charging voltage range without adding stress on the resonant components or operating far from the unity gain point. Due to wide output range, the converter parameters are optimized using the time-domain analytical model to cover the required range without adding unnecessary circulating current that compromises the efficiency. First, the LLC resonant converter fundamentals are briefly introduced. Then, the proposed topology operation and advantages are discussed. After which, the converter’s requirements and design method are presented, focusing on circulating current minimization. Finally, the effectiveness of the proposed converter and the optimized design strategy is verified experimentally on a 10 kW prototype with an input of 800 V and an output of 200 - 1000 V.

Design and Experimental Verification of a General Single-Switch N-Stage Z-Network High Gain Boost Converter

A single-switch N-stage Z-network high-gain boost converter is proposed in this study, which can be applied in the field of chip etching for bias provision. The circuit topology, operation mode, voltage gain and the control strategy are analyzed. Thereafter, the steady-state performance of the circuit is analyzed with small signal stability modeling. A simulation model is built using Simulink and compared with the traditional quadratic circuit. Combined with the control strategy, the circuit can obtain better steady-state performance by controlling the number of working N-networks and adjusting the duty ratio in the case of high voltage, wide range of voltage output and dynamic voltage output. The simulation model and hardware prototype of the single-switch four-stage Z-network high-gain boost circuit are built and tested, which have verified the effectiveness of the proposed design.

Low-Noise Potentiostat Readout Circuit with a Chopper Fully Differential Difference Amplifier for Glucose Monitoring

This paper presents a low-noise potentiostat readout circuit with a chopper fully differential difference amplifier (FDDA) for glucose monitoring. Glucose monitoring is necessary for the early diagnosis of diabetes complications and for health management. Ammeter electrochemical sensors are widely used for glucose detection, and in general, a three-electrode structure of a reference electrode (RE), a counter electrode (CE), and a working electrode (WE) is implemented with a potentiostat structure. A low-noise characteristic of the readout circuit is essential for highly accurate glucose monitoring. The chopping technique can reduce low-frequency noises such as 1/f noise and can achieve the required low-noise characteristic. The proposed potentiostat readout circuit is based on a low-noise chopper FDDA with a class-AB output stage. The implementation of the chopper FDDA scheme of the potentiostat readout circuit can decrease the number of amplifiers in the control part of the potentiostat, with reduced power consumption and a wide dynamic output range. The negative feedback loop of the inverting amplifier scheme with the FDDA maintains the voltage between the WE and RE constants. The negative feedback loop tracks the reference voltage of the RE with an input voltage of the WE. The proposed potentiostat readout circuit is designed in the standard 0.18 µm CMOS process, and the simulated current consumption is 48.54 μA with a 1.8 V power supply. The simulated input-referred noise level was 8.53 pArms.

Design and Implementation of a Two-Stage Resonant Converter for Wide Output Range Operation

This article proposes and analyzes a two-stage isolated dc–dc converter for electric vehicle charging applications, where high efficiency over a wide range of battery voltages is required. It employs a first preregulation stage and a second half-bridge LLC stage, integrated with the first. The second stage is always operated at resonance, ensuring high efficiency. The first preregulation stage is responsible for the desired input-to-output voltage conversion ratio and the zero-voltage switching operation of all the switches. This allows low conversion losses even with voltages that may vary over a wide range. The article presents the conversion structure, the converter analysis, the design of the magnetic elements, and demonstrates the converter operation considering an experimental prototype interfacing a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${750\text{-}} \mathrm{V}$</tex-math></inline-formula> dc-link with an output bus with nominal voltage range <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${250} \mathrm{}$</tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${500}\, \mathrm{V}$</tex-math></inline-formula> . The implemented module is rated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${5}\,\text{kW}$</tex-math></inline-formula> and achieves a peak efficiency of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{98.0\%}$</tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${3\text{-}} \text{kW}$</tex-math></inline-formula> output power.

A Bidirectional Five-Level Buck PFC Rectifier With Wide Output Range for EV Charging Application

AC-to-DC conversion is integral to the two-stage charging interface of electric vehicle (EV) batteries. For such chargers, the use of multilevel rectifiers (MLRs) reduces voltage ratings of power switches, while achieving a high-quality input voltage waveform. Balancing of capacitors in MLRs, however, is an important challenge. In this work, a power factor correction (PFC) five-level rectifier with self-balanced switched capacitors is proposed. Each leg of the presented topology comprises five power switches and one switched capacitor, where the voltage ratings of power switches are equal to the output dc voltage. It does not require an additional filter capacitor on the dc side, as the load appears in parallel always with a switched capacitor of one of the legs. The five-level operation with continuous conduction leads to the elimination of the capacitive filter on the ac-side and inductive filter on the dc-side. This article presents the operating principle, modulation strategy, closed-loop control, and design aspects of the proposed rectifier. The proposed topology is validated through experimental results and a comparison is made with other topologies. Following three features of the proposed topology make it suitable for EV battery charging applications—buck operation with a wide output regulation, the possibility of bidirectional flow of power needed for vehicle-to-grid systems, and easy realization of its three-phase version by simply adding one more leg. These features too have been demonstrated with experimental results.

Suppression of self-excited thermoacoustic instabilities by convective-acoustic interference

In this paper we demonstrate direct suppression of self-excited thermoacoustic instabilities over a range of operating conditions using targeted convective-acoustic interference. Premixed hydrogen enriched methane-air flames were confined in a cylindrical pipe resulting in self-excited instabilities that corresponded to the quarter wave mode of the pipe. To suppress the instability, the phenomenon of lock-in (synchronisation) between the acoustic mode and vortex shedding from a set of cylinders placed upstream was used to produce destructive interference and suppress the self-excited modes. This was done by varying the location of the cylinders to control the convective time-delay between the convective and acoustic modes so that their combined effect on the flame response was tuned to suppress the global fluctuation of the heat release rate. This leads to a reduction in the limit-cycle amplitude and stable operation without a significant change to the flame structure. Measurements were taken over a wide range of equivalence ratios to demonstrate that the method is capable of stabilising the system for all conditions. Using a methodology which relies on time-delays related to hydrodynamic instability, rather than flame-related parameters, enables its application to fuel-flexible systems, often designed to operate within a wide range of power outputs.

Assessing the impact of COVID-19 measures on COPD management and patients: a simulation-based decision support tool for COPD services in the UK

ObjectivesTo develop a computer-based decision support tool (DST) for key decision makers to safely explore the impact on chronic obstructive pulmonary disease (COPD) care of service changes driven by restrictions...

An Ultrasonic Energy Harvesting IC Providing Adjustable Bias Voltage for Pre-Charged CMUT.

Ultrasonic wireless power transmission (WPT) using pre-charged capacitive micromachined ultrasonic transducers (CMUT) is drawing great attention due to the easy integration of CMUT with CMOS techniques. Here, we present an integrated circuit (IC) that interfaces with a pre-charged CMUT device for ultrasonic energy harvesting. We implemented an adaptive high voltage charge pump (HVCP) in the proposed IC, which features low power, overvoltage stress (OVS) robustness, and a wide output range. The ultrasonic energy harvesting IC is fabricated in the 180 nm HV BCD process and occupies a 2 × 2.5 mm2 silicon area. The adaptive HVCP offers a 2× - 12× voltage conversion ratio (VCR), thereby providing a wide bias voltage range of 4 V-44 V for the pre-charged CMUT. Moreover, a VCR tunning finite state machine (FSM) implemented in the proposed IC can dynamically adjust the VCR to stabilize the HVCP output (i.e., the pre-charged CMUT bias voltage) to a target voltage in a closed-loop manner. Such a closed-loop control mechanism improves the tolerance of the proposed IC to the received power variation caused by misalignments, amount of transmitted power change, and/or load variation. Besides, the proposed ultrasonic energy harvesting IC has an average power consumption of 35 μW-554 μW corresponding to the HVCP output from 4 V-44 V. The CMUT device with a local surface acoustic intensity of 3.78 mW/mm2, which is well below the FDA limit for power flux (7.2 mW/mm2), can deliver sufficient power to the IC.

A Topology-Reconfigurable LLC Resonant Converter for Wide Output Range Applications

A novel topology-reconfigurable LLC resonant converter for wide output range applications is proposed in this article. In the proposed wide output converter, a reconfigurable topology based on matrix transformer is presented, the primary sides of the matrix transformer are connected in parallel, the connection of the secondary sides can be changed by controlling the selector switch on the secondary side, which are categorized into HV and LV operation mode and suitable for different output levels. The HV operation mode whose secondary rectifiers are connected in series is employed for the high output level, while the LV operation mode whose secondary rectifiers are connected in parallel is employed for the low output level. Consequently, the output range is widened by configuring the connection structure. What's more, the switching frequency range can be reduced. Furthermore, the magnetizing current will be reduced by the parallel connection of the primary sides, and soft-switching operation is realized on all of the switches over the full operation range. Therefore, the proposed converter features a wide output voltage range along with high efficiency. Finally, an experimental prototype with 400 VDC input and 150 VDC/14 A-500 VDC/4.2 A output is fabricated and tested to verify the feasibility and effectiveness of the converter.

Minimum-Output-Current-Ripple Control of Current-Fed Three-Level Phase-Shift Full-Bridge Converter

Electrified ports using medium-voltage DC (MVDC) renewable energy microgrids require current-fed dc/dc converters in application scenarios such as battery or ultracapacitor charging units and hydrogen production systems. This paper designs a three-level phase-shift full-bridge (TL-PSFB) converter that interfaces with the MVDC microgrid. Its operation in the current source mode requires a wide output voltage range and small output current ripple. Firstly, the dual-output TL-PSFB topology is introduced, and the principle of phase-shift pulse width modulation (PS-PWM) is presented. Secondly, the principle of the traditional constant-conduction-duty-cycle (CCDC) strategy is analyzed. Then, a minimum-output-current-ripple (MOCR) strategy is proposed by analyzing the relationship between output current ripple, conducting-duty cycle, and phase-shift duty cycle, and a constant current control combined with the MOCR strategy is designed. The output current ripple of the MOCR strategy is smaller than that of the CCDC strategy in a full range of operating conditions. Under the same output current ripple design index, the value and loss of the filter inductor can be reduced with the MOCR strategy. In addition, the MOCR strategy can widen the output voltage regulation range and increase the bus voltage utilization without causing significant changes to the total harmonic distortion (THD) of primary voltage. Finally, experimental results verify the correctness of the theoretical analysis.

A Programmable Multiple Frequencies Clock Generator With Process and Temperature Compensation Circuit for System on Chip Design

This article presents a programmable multiple frequencies clock generator with a process and temperature compensation circuit design. The proposed clock generator can achieve a stable and wide frequency range output for a single input frequency by using digital control codes as well as process and temperature compensation mechanisms. In our approach, the first step is to adjust the duty-cycle of the input clock by using a digitally controlled pulsewidth modulator (DCPWM) to generate an output clock signal with a duty-cycle of 20% to 80%. Second, the various duty-cycle clock outputs of the DCPWM are integrated by the duty-cycle-to-voltage converter to generate analog voltage signals to control the succeeding voltage-controlled ring oscillator (VCO). Through the use of various control voltages, different VCO output frequencies are generated. Finally, by using the process and temperature compensation circuit, the proposed clock generator can provide a stable and wide frequency range. The proposed chip is fabricated in a 180-nm CMOS process and has an output frequency range of 35–138 MHz at a supply voltage of 0.9 V. At 120 MHz, the power dissipation and rms jitter are 224.3 μW and 7.84 ps, respectively. The active area of the chip is 0.62 mm × 0.76 mm.

A 270-mA Self-Calibrating-Clocked Output-Capacitor-Free LDO With 0.15–1.15V Output Range and 0.183-fs FoM

This article proposes a fully integrated output-capacitor-free low-dropout regulator (LDO) for mobile applications. To overcome the limited output voltage range of typical analog LDOs, our design uses a rail-to-rail voltage-difference-to-time-converter (VDTC) and a charge pump (CP) to achieve a wide output range. Using a self-calibrating clock generator (SCCG) removes the need for an external clock source and adaptively tunes the clock frequency, enabling fast transient responses while minimizing quiescent current. A tunable undershoot compensator (TUC) mitigates voltage droop by detecting the drop in the output voltage due to a sharp increase in load current and compensating the output voltage immediately. The proposed LDO is fabricated in a 65-nm low power (LP) CMOS process and demonstrates a maximum load current capacity of 270 mA. The input and output voltage ranges of the LDO are 0.5–1.2 and 0.15–1.15 V, respectively, with 12.7- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> quiescent current and 99.99% peak current efficiency. The measured undershoot and settling time are 150 mV and 100 ns at a slew rate of 200 mA/3 ns, respectively, achieving a figure of merit (FoM) of 0.183 fs.

Self-Powered and Self-Configurable Active Rectifier Using Low Voltage Controller for Wide Output Range Energy Harvesters

This article presents a self-configurable and self-poweredactive rectifier that operates from 0.25–20 V for energy harvesting applications. The proposed circuit self-startups from a low voltage using a charge pump and amplifies the voltage with a voltage doubler topology to provide succeeding circuits such as boost converters with a higher voltage. When the voltage of the energy harvester reaches a high threshold, the circuit switches its topology to a full-wave rectifier that does not amplify the voltage. The start-up circuit can limit its voltage intake to prevent boosting the high voltage, which may damage the whole circuit. Comparators with a maximum operating voltage of 5.5 V used in the implementation of the rectifier are protected by a diode and resistor based circuit. A piezoelectric energy harvester (PEH) that has a wide open-circuit voltage of 0.4–15 V under the acceleration of 0.04–0.3 g was used to test the circuit. The experiment results showed the rectifier can startup from 0.25 V and switch its topology according to the PEH voltage. The voltage and power conversion efficiencies are over 90% in most cases.

Accurate Steady-State Modeling and Design Based on State Trajectory Analysis for LCC Resonant Converter With Voltage Doubler Rectifier

The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> series–parallel resonant converter with a voltage doubler rectifier, widely used in X-ray machines, is required to meet an extremely wide output range. However, state-of-the-art models are based on fundamental harmonic approximation and cannot maintain good accuracy over the entire output range. The state trajectory method has the potential to achieve a full range of high accuracy without high complexity, but it only applies to simple topologies, like <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> with a full-bridge rectifier. For <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> with a voltage multiplier, the capacitors in the multiplier are involved in the resonance, which can be modeled as a five-element resonant circuit. Moreover, the conduction sequence of components in the minor mode is different from that in the major mode, which is usually ignored in the steady-state model. The influence of the output capacitance of power transistors on the state trajectory is so unclear that the model accuracy decreases considerably at high frequencies. In this article, the equivalent parallel resonant capacitance is derived through the current distribution. The steady-state model of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> converter with a voltage doubler rectifier is developed for both major mode and minor mode. The deviation of the state trajectory and modeling accuracy induced by the output capacitor is investigated. Based on the proposed model and device stress analysis, the design procedure for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> under a wide operation range is presented. The simulations and experiments verify the accuracy of the model and the validity of the design method. The simulation mismatches are less than 2.3% over the entire output range. The maximum experimental mismatch is 15%.

A modified constant-torque spring hinge toward synchronous deployment

Spring hinges, due to their lightweight and energy-saving characteristics, have emerged as an imperative power source for deploying spacecraft appendages. In this paper, a modified constant-torque spring hinge (MCTSH) is proposed for aerospace applications. The conventional constant-torque hinge (CCTSH) is enhanced to bridge the gap toward new applications, resulting in a more compact structure with less friction and wide-range output torques. A novel torque control method is elaborated on for deployable, MCTSH-driven and multi-link mechanisms, thereby simplifying the design procedure via reducing the design variables by half. Given the intricate coupling effects of multi-link mechanisms, a synchronous deployment technique integrating the Newton-Euler dynamics, the design of experiments (DOE) method and the optimization is introduced, and its performance is verified by both simulations and experiments on multi-link grippers. The results demonstrate the high potential of the proposed method for deployable mechanisms toward aerospace applications, e.g., solar array panels and antennas.

Wideband Photonic Microwave Frequency Divider With Large Harmonic Suppression Capability

An all-optical photonic microwave frequency divider (PMFD) is presented. It is based on injecting an RF phase modulated optical signal into a semiconductor laser oscillating in the period-two state. New optical frequency components with frequency separation of half of the input RF signal frequency are generated at the laser output. A frequency divided signal can be obtained by the beating of these optical frequency components at a photodetector. Large harmonic suppression can be achieved by using an optical filter to select only two optical frequency components to be detected by the photodetector. The proposed PMFD is free of electrical components and does not suffer from the modulator bias drift problem. It has the potential to operate over a 100 GHz frequency range. System parameters required to realise divide-by-two frequency division operation for different input RF signal frequencies are investigated. Experimental results are presented for the novel PMFD, which demonstrate the generation of a 1/2 frequency component for different input RF signal frequencies by controlling the forward bias current of an off-the-shelf semiconductor laser, and which also show the important advantages of large harmonic suppression and high signal-to-noise ratio performance. Wide input RF signal power range and high output stability performance are also demonstrated experimentally.

Post‐fatigue ability to activate muscle is compromised across a wide range of torques during acute hypoxic exposure

The purpose of this study was to assess how severe acute hypoxia alters the neural mechanisms of muscle activation across a wide range of torque output in a fatigued muscle. Torque and electromyography responses to transcranial and motor nerve stimulation were collected from 10 participants (27 years ± 5 years, 1 female) following repeated performance of a sustained maximal voluntary contraction that reduced torque to 60% of the pre‐fatigue peak torque. Contractions were performed after 2 h of hypoxic exposure and during a sham intervention. For hypoxia, peripheral blood oxygen saturation was titrated to 80% over a 15‐min period and remained at 80% for 2 h. Maximal voluntary torque, electromyography root mean square, voluntary activation and corticospinal excitability (motor evoked potential area) and inhibition (silent period duration) were then assessed at 100%, 90%, 80%, 70%, 50% and 25% of the target force corresponding to the fatigued maximal voluntary contraction. No hypoxia‐related effects were identified for voluntary activation elicited during motor nerve stimulation. However, during measurements elicited at the level of the motor cortex, voluntary activation was reduced at each torque output considered (P = .002, η p 2 = .829). Hypoxia did not impact the correlative linear relationship between cortical voluntary activation and contraction intensity or the correlative curvilinear relationship between motor nerve voluntary activation and contraction intensity. No other hypoxia‐related effects were identified for other neuromuscular variables. Acute severe hypoxia significantly impairs the ability of the motor cortex to voluntarily activate fatigued muscle across a wide range of torque output.

Aptamer-Array-Guided Protein Assembly Enhances Synthetic mRNA Switch Performance.

Synthetic messenger RNA (mRNA) switches are powerful synthetic biological tools that can sense cellular molecules to manipulate cell fate. However, their performances are limited by high output signal noise due to leaky output protein expression. Here, we designed a readout control module that disables protein leakage from generating signal. Aptamer array on the switch guides the inactive output protein to self‐assemble into functional assemblies that generate output signal. Leaky protein expression fails to saturate the array, thus produces marginal signal. In this study, we demonstrated that switches with this module exhibit substantially lower signal noise and, consequently, higher input sensitivity and wider output range. Such switches are applicable for different types of input molecules and output proteins. The work here demonstrates a new type of spatially guided protein self‐assembly, affording novel synthetic mRNA switches that promise accurate cell manipulation for biomedical applications.

Aptamer‐Array‐Guided Protein Assembly Enhances Synthetic mRNA Switch Performance

AbstractSynthetic messenger RNA (mRNA) switches are powerful synthetic biological tools that can sense cellular molecules to manipulate cell fate. However, their performances are limited by high output signal noise due to leaky output protein expression. Here, we designed a readout control module that disables protein leakage from generating signal. Aptamer array on the switch guides the inactive output protein to self‐assemble into functional assemblies that generate output signal. Leaky protein expression fails to saturate the array, thus produces marginal signal. In this study, we demonstrated that switches with this module exhibit substantially lower signal noise and, consequently, higher input sensitivity and wider output range. Such switches are applicable for different types of input molecules and output proteins. The work here demonstrates a new type of spatially guided protein self‐assembly, affording novel synthetic mRNA switches that promise accurate cell manipulation for biomedical applications.

Wide-Output Range Power Processing Unit for 6-kW Hall Thruster

The Japan Aerospace Exploration Agency (JAXA) has developed a power processing unit (PPU) for a 6 kW Hall thruster system. The PPU is a candidate for future mission applications, such as all-electric satellites, exploration vehicles, and orbital transfer services. The PPU has to be small and still provide a wide output range of outputs, consider the in orbit and launch environments, and manage any instability in the Hall thruster's discharge. Specifically, the four converters that make up the anode power supply of the PPU is digitally controlled to reduce the size of the control circuit. It must operate stably despite small output capacitors and long dead times. This article clarifies the design criteria for the power supply, focusing on the size of capacitors and the PI control parameters to solve these problems. The result is a compact, high-performance PPU for the 6 kW Hall thruster. The power supply meets stringent design criteria and operates the thruster stably with an output voltage that can be varied between 200 and 730 V, provide a maximum power of 5.9 kW, and offer a maximum efficiency of 96.1% in the coupling test for the 6 kW Hall thruster. The proposed PPU, including the anode power supply, achieves a power density of 0.3 kW/kg, significantly higher than that of comparable PPUs.