Showing papers on "Switched capacitor published in 2017"

Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

Abstract: DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

Topology, Modeling, and Design of Switched-Capacitor-Based Cell Balancing Systems and Their Balancing Exploration

Abstract: A series of switched-capacitor (SC) cell balancing circuits is proposed for rechargeable energy storage devices like battery and supercapacitor strings in this paper. Taking a basic SC-based cell balancing unit as an equivalent resistor, the behavioral models of the proposed cell balancing circuits are developed to evaluate their balancing performance. Comparing with existing SC-based cell balancing circuits, the main advantage of the proposed circuits is that their balancing speed is independent of both of the number of battery cells and initial mismatch distribution of cell voltages. In order to improve the operation performance of SC-based cell balancing circuits in the respect of minimizing the equivalent resistance, optimizing methodologies of circuit parameters are introduced by referring the concepts of slow switching limit and fast switching limit as well as inductive switching limit of SC power converters. Simulation and experimental results are provided to verify the feasibility of the proposed cell balancing circuits.

Extended Switched-Boost DC-DC Converters Adopting Switched-Capacitor/Switched-Inductor Cells for High Step-up Conversion

Abstract: This paper proposes a family of switched-boost dc–dc converters for the high stepup voltage conversion applications, such as renewable energy power generation, uninterruptible power supply, and automobile high-intensity discharge headlamps. Compared with other dc–dc converters, the proposed switched-boost converter, which combines the traditional switched-boost network with the switched-capacitor/switched-inductor cells, has the following features: higher output voltage gain, a fewer passive components such as inductors and capacitors, and lower voltage stress across the output diode and power switches. Another advantage of the proposed topology is its expandability. If a higher voltage conversion ratio is required, additional cells can be easily cascaded by adding one inductor and three diodes. The structure, operating principle analysis, parameter design, and comparison with other dc–dc converters are also analyzed. Finally, both simulations and experimental results are presented to verify the effectiveness of the proposed converter.

A Quasi-Resonant Switched-Capacitor Multilevel Inverter With Self-Voltage Balancing for Single-Phase High-Frequency AC Microgrids

Abstract: In this paper, a quasi-resonant switched-capacitor (QRSC) multilevel inverter (MLI) is proposed with self-voltage balancing for single-phase high-frequency ac (HFAC) microgrids. It is composed of a QRSC circuit (QRSCC) in the frontend and an H-bridge circuit in the backend. The input voltage is divided averagely by the series-connected capacitors in QRSCC, and any voltage level can be obtained by increasing the capacitor number. The different operational mechanism and the resulting different application make up for the deficiency of the existing switched-capacitor topologies. The capacitors are connected in parallel partially or wholly when discharging to the load, thus the self-voltage balancing is realized without any high-frequency balancing algorithm. In other words, the proposed QRSC MLI is especially adapted for HFAC fields, where fundamental frequency modulation is preferred when considering the switching frequency and the resulting loss. The quasi-resonance technique is utilized to suppress the current spikes that emerge from the instantaneous parallel connection of the series-connected capacitors and the input source, decreasing the capacitance, increasing their lifetimes, and reducing the electromagnetic interference, simultaneously. The circuit analysis, power loss analysis, and comparisons with typical switched-capacitor topologies are presented. To evaluate the superior performances, a nine-level prototype is designed and implemented in both simulation and experiment, whose results confirm the feasibility of the proposed QRSC MLI.

Single-switch high step-up converter based on coupled inductor and switched capacitor techniques with quasi-resonant operation

Abstract: This study presents a novel single-switch high step-up dc-dc converter employing a quasi-resonant operation with high efficiency and low ripple continuous input current characteristics. In order to achieve a high voltage gain, a combination of coupled inductor and switched capacitor techniques is used in the proposed dc-dc converter. Moreover, utilising a series resonance capacitor with the leakage inductance of the coupled inductor leads to a resonant circuit. Subsequently, by employing a quasi-resonant operation, the switching loss of the proposed dc-dc converter has been reduced significantly. Operational analysis, mathematical derivation, component voltage and current ratings are well demonstrated in this study. Finally, the performance of the proposed circuit is evaluated through a 200 W laboratory prototype with 25 V input voltage and 400 V output voltage. The maximum efficiency achieved at full load is 96.4%.

Investigation of capacitor voltage balancing in practical implementations of flying capacitor multilevel converters

Abstract: Flying capacitor multilevel (FCML) converters are known to naturally balance the capacitor voltages through the use of phase-shifted pulse-width modulation. However, in practice, the capacitor voltages can still deviate and active balancing is often required. This work investigates the origins of the voltage imbalance in practical implementations of such converters and presents corresponding solutions. It is shown that the source impedance and the input capacitor can have a drastic impact on the flying capacitor voltages. Moreover, we also demonstrate that an FCML converter with an even number of levels has significantly better immunity to the presence of source impedance than one with an odd number of levels. It is also found that gate signal propagation delay mismatch from half-bridge gate drivers will lead to capacitor imbalance. An alternative gate drive power supply circuit is designed to address this problem. Lastly, variations of switches' on-resistance are found to have a small impact on the capacitor voltage balance.

A Two-Terminal Active Capacitor

Abstract: This letter proposes a concept of two-terminal active capacitor implemented by power semiconductor switches and passive elements. The active capacitor has the same level of convenience as a passive one with two power terminals only. It is application independent and can be specified by rated voltage, ripple current, equivalent series resistance, and operational frequency range. The concept, control method, self-power scheme, and impedance characteristics of the active capacitor are presented. A case study of the proposed active capacitor for a capacitive dc-link application is discussed. The results reveal a significantly lower overall energy storage of passive elements and a reduced cost to fulfill a specific reliability target, compared to a passive capacitor solution. Proof-of-concept experimental results are given to verify the functionality of the proposed capacitor.

Multitrack Power Conversion Architecture

Abstract: This paper introduces a MultiTrack power conversion architecture that represents a new way of combining switched-capacitor circuits and magnetics. The MultiTrack architecture takes advantages of the distributed power processing concept and a hybrid switched-capacitor/magnetics circuit structure. It reduces the voltage ratings on devices, reduces the voltage regulation stress of the system, improves the component utilization, and reduces the sizes of passive components. This architecture is suitable to dc–dc and grid-interface applications that require both isolation and wide voltage conversion range. An 18–80 V input, 5 V, 15 A output, 800 kHz, 0.93 in $^2$ (1/16 brick equivalent) isolated dc–dc converter has been built and tested to verify the effectiveness of this architecture. By employing the MultiTrack architecture, utilizing GaN switches, and operating at higher frequencies, the prototype converter achieves a power density of 457.3 W/in $^3$ and a peak efficiency of 91.3%. Its power density is 3 $\times$ higher than the state-of-the-art commercial converters with comparable efficiency across the wide operation range.

Multilevel modular switched-capacitor resonant converter with voltage regulation

Abstract: This paper presents a novel modular multilevel switched-capacitor based resonant converter (MMSCRC) to achieve dc-dc power conversion function. In comparison to existing multilevel modular switched-capacitor circuits, the proposed switched-capacitor resonant converter (SCRC) possess voltage regulation capability. Its modular structure accomplishes voltage conversion function and proposed closed-loop phase-shift control regulates the output voltage. Meanwhile, zero-voltage switching (ZVS) operation can be accomplished. By increasing switching frequency of wide bandgap device and reducing inductance in the circuit, magnetic components can be minimized. Hence, high power density and high efficiency of the proposed converter can be achieved. This paper includes circuit operation, steady-state characteristics as well as in-depth analysis for ZVS operation. Simulation results are provided to verify the operation principle of the proposed MMSCRC. A 600W lab prototype with 6:1 conversion ratio has been built. Experimental result are also provided to validate the theoretical analysis.

Multilevel MVDC Link Strategy of High-Frequency-Link DC Transformer Based on Switched Capacitor for MVDC Power Distribution

Abstract: To improve the power quality of a medium-voltage dc (MVDC) power distribution grid, a multilevel MVDC link strategy (MMS) for high-frequency-link dc transformer based on switched capacitor is proposed in this paper. By applying MMS, the fluctuations in current can be decreased effectively, and the current stress and efficiency performance will be improved. Representative theoretical analysis and experimental results are presented to verify the correctness and effectiveness of the proposed solution.

High step-up high step-down bidirectional DC/DC converter

Abstract: In this study, a new high step-up high step-down bidirectional dc–dc converter is proposed. In the proposed converter, the voltage conversion ratio is increased by using two coupled inductors and switched capacitor circuit in both boost and buck operations. The proposed bidirectional converter in comparison with other presented high-voltage gain boost converters with two coupled inductors in the literature has the highest voltage conversion ratio. In this study, the proposed topology is analysed in all operating modes and the current and voltage stresses of all switches, voltage gain and maximum and minimum current through the inductors are calculated for both boost and buck operations. Finally, the accuracy of the obtained analytical results and correct operation of the proposed converter are verified through PSCAD/EMTDC simulation and experimental results.

Modeling and Performance Limits of Switched-Capacitor DC–DC Converters Capable of Resonant Operation With a Single Inductor

Abstract: This paper explores generalized output impedance models and develops a new performance-limit figure of merit (FOM) for switched-capacitor (SC) dc–dc converters that can be resonated or soft-charged with a single inductor. Compared to past work, the output impedance model is greatly simplified through a two-port charge multiplier treatment, yet it maintains accuracy across conversion ratios and is valid in both slow- and fast-switching operation. Building on previous analytical treatments of SC and ReSC converters, the model is expanded to derive optimizations that include both conduction and switching losses. The process is used to identify a new FOM for hybrid–resonant SC converters that can be used to identify the most suitable architectures for a given conversion ratio and relevant (energy or area) constraints on flying capacitors. This is used to highlight the active-device and capacitance utilizations of common topologies, as well as which are most favorable for hybrid–resonant operation.

A 10 W On-Chip Switched Capacitor Voltage Regulator With Feedforward Regulation Capability for Granular Microprocessor Power Delivery

Abstract: Granular power delivery with per-core regulation for microprocessor power delivery has the potential to significantly improve the energy efficiency of future data centers. On-chip switched capacitor converters can enable such granular power delivery with per-core regulation given a high efficiency, high power density, fast response time, and high output power converter design. This paper details the implementation of an on-chip switched capacitor voltage regulator in a $32\,\mathrm{n}\mathrm{m}$ SOI CMOS technology with deep trench capacitors. A novel feedforward control for reconfigurable switched capacitor converters is presented. The feedforward control reduces the output voltage droop following a transient load step. This leads to a reduced minimum microprocessor supply voltage, thereby reducing the overall power consumption of the microprocessor. The implemented on-chip switched capacitor voltage regulator provides a $0.7-1.1$ V output voltage from $1.8$ V input. It achieves a $85.1\%$ maximum efficiency at $3.2\,\mathrm{W}\mathrm{/}\mathrm{m}\mathrm{m}^2$ power density, a subnanosecond response time with improved minimum supply voltage capability, and a maximum output power of $10\,\mathrm{W}$ . For an output voltage of $850\,\mathrm{m}\mathrm{V}$ , the feedforward control reduces the required voltage overhead by $60\,\mathrm{m}\mathrm{V}$ for a transient load step from $10\%$ to $100\%$ of the nominal load. This can reduce the overall power consumption of the microprocessor by $7\%$ .

A delta-structured switched-capacitor equalizer for series-connected battery strings

Abstract: A delta-structured switched-capacitor equalizer (DSSCE) is proposed to achieve the automatic any-cells-to-any-cells (AC2AC) balancing for a long battery string, leading to the fast-speed and high-efficiency balancing. Only two switches are required for each battery cell, and one capacitor is set for any two cells, materializing the delta-structured switched capacitors (SC). All MOSFETs are triggered by two complementary PWM signals, and energy can be automatically and directly exchanged among all cells without the need of cell monitoring. The proposed system has the advantages of simple control, high efficiency, and direct, simultaneous, and automatic equalization among cells. A prototype system for four LiFePO 4 battery cells is set up. Experimental results demonstrate the proposed topology has an improved balancing performance with a high balancing efficiency of 94.5%.

PWM Converter Integrating Switched Capacitor Converter and Series-Resonant Voltage Multiplier as Equalizers for Photovoltaic Modules and Series-Connected Energy Storage Cells for Exploration Rovers

Abstract: Power systems for exploration rovers tend to be complex as three separate converters are necessary; in addition to a main dc–dc converter and cell equalizer for rechargeable energy storage cells, an equalizer for photovoltaic (PV) modules is desirably equipped in order to preclude negative impacts of partial shading. This paper proposes the pulse width modulation (PWM) converter integrating voltage equalizers for PV modules and energy storage cells. The proposed integrated converter comprises a switched capacitor converter, PWM buck converter, and series-resonant voltage multiplier that perform PV equalization, power conversion from the PV modules to the load, and cell equalization, respectively. Three converters can be integrated into a single unit with reducing the total switch counts, achieving not only system-level but also circuit-level simplifications. The derivation procedure of the integrated converter is explained, followed by the operation analysis. Experimental tests were performed using series-connected supercapacitor (SC) modules and solar array simulators to emulate a partial shading condition. With the integrated converter, the extractable maximum power from the PV modules significantly increased while voltage imbalance of SC modules was adequately eliminated, demonstrating the integrated performance of the proposed converter.

A 20-pW Discontinuous Switched-Capacitor Energy Harvester for Smart Sensor Applications

Abstract: We present a discontinuous harvesting approach for switch capacitor dc–dc converters that enables ultralow-power energy harvesting. Smart sensor applications rely on ultralow-power energy harvesters to scavenge energy across a wide range of ambient power levels and charge the battery. Based on the key observation that energy source efficiency is higher than charge pump efficiency, we present a discontinuous harvesting technique that decouples the two efficiencies for a better tradeoff. By slowly accumulating charge on an input capacitor and then transferring it to a battery in burst mode, dc–dc converter switching and leakage losses can be optimally traded off with the loss incurred by nonideal maximum power point tracking operation. Harvester duty cycle is automatically modulated instead of charge pump operating frequency to match with the energy source input power level. The harvester uses a hybrid structure called a moving-sum charge pump for low startup energy upon a mode switch, an automatic conversion ratio modulator based on conduction loss optimization for fast conversion ratio increment, and a 40% end-to-end efficiency from 113 pW to 1.5 $\mu \text{W}$ with 20-pW minimum harvestable input power.

Sensor-Less Current Sharing Over Wide Operating Range for Extended-Duty-Ratio Boost Converter

Abstract: An extended-duty-ratio (EDR) boost converter is studied extensively in this paper for high voltage gain applications with a wide input (and/or output) voltage range. The EDR is a unique combination of an interleaved, multiphase boost converter and switched capacitor configuration that achieves high voltage gain with significantly lower switch voltage stress and switching losses compared to conventional high-gain solutions. Most of the switches in the multiphase EDR experience only a fixed fraction of the output voltage ( $1/M, 2/M$ , etc., where $M$ is the number of phases). Through extensive analysis over a wide operating range, it is shown here that the EDR boost converter has inherent current sharing among the phases only in a limited range of duty ratio— $(M-1)/M \leq D \leq 1$ . As the duty ratio reduces beyond this range as required in wide input voltage applications, inherent current sharing property is lost. In this paper, techniques to ensure current sharing under all operating zones without requiring current sensors are presented. Instead of having equal duty ratio for each phase, it is adjusted for each phase according to the operating region of the converter. Extensive analysis is presented to derive the required duty ratio changes for the different phases. The proposed concept is validated with experimental results from a 250 W, 3-phase EDR boost, and GaN-based hardware prototype.

A Multiphase Switched Capacitor Power Amplifier

Abstract: 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.

Design of Soft-Charging Switched-Capacitor DC–DC Converters Using Stage Outphasing and Multiphase Soft-Charging

Abstract: In this paper, two techniques, called stage-outphasing (SO) and multiphase soft-charging (MSC), are introduced, which make use of the advanced multiphasing concept to soft-charge charge transfers between flying capacitors. As such, the charge sharing losses of fully integrated switched-capacitor (SC) converters are reduced, leading to better capacitance utilization, higher efficiency, and higher power density. Furthermore, when used in combination with the Dickson converter, the relative improvement gets better with increasing voltage conversion ratio (VCR), making them an excellent choice to reduce power delivery network-induced losses in modern microchips. The impact of the proposed techniques on the performance is discussed. A 3:1 Dickson SC converter is realized, which implements SO and MSC and achieves a state-of-the-art 1.1-W/mm2 power density and 82% efficiency combination using common capacitor technologies. Finally, two figures of merit for monolithic SC dc-dc converters are proposed that include the VCR and power density, to allow fair comparison of the converter’s performance to the literature.

10.3 A 94.2%-peak-efficiency 1.53A direct-battery-hook-up hybrid Dickson switched-capacitor DC-DC converter with wide continuous conversion ratio in 65nm CMOS

Abstract: Owing to the need for low power consumption, portable and wearable electronics operate at low voltages, typically below 1V, with recent designs in near- and subthreshold operation resulting in voltages down to 0.3 to 0.5V. Meanwhile, voltage range of the most common energy source - the Li-ion battery - is 3 to 4.2V, motivating the need for compact power converters capable of large conversion ratio with wide and efficient voltage regulation.

Cascaded High-Voltage-Gain Bidirectional Switched-Capacitor DC–DC Converters for Distributed Energy Resources Applications

Abstract: A family of bidirectional switched-capacitor (SC) converters with high-gain ratio of any positive integer is proposed in this paper for distributed energy resources applications. As compared with other existing SC converters achieving a same conversion gain, the main advantages of the proposed converters are that they require a relatively lower number of switches and capacitors, have a relatively lower switch's and capacitor's stress, and that their associated driver circuits are simpler to realize. Importantly, with the achievable conversion ratio being flexible and that the input and output of the proposed converters are of common ground, the proposed converters are widely suitable for many applications. Moreover, as the proposed converters do not possess magnetic component or any component that can severely degrade the converters’ performance at high temperature, they are especially useful for high-temperature applications. Besides, the proposed converters are capable of delivering bidirectional power, which is a key requirement for emerging applications with battery storages. Different aspects of the proposed converters, including a simple auxiliary power supply circuit for the MOSFETs’ drivers, will be discussed in this paper. A nine-time SC converter prototype that operates with 20-V input voltage, 100-W output, and at 75 kHz, is constructed and tested. Experiment results show that the maximum efficiency achievable with this prototype is over 98% (without driver's loss) and the efficiency over the entire load range between 25 and 100 W is over 95.5% including the driver's loss. The output voltage ripple of the SC converter is less than 1%. When the SC converter is open-loop controlled, the load voltage regulation is relatively well kept at less than 5% between full load and no load conditions.

A Cell-to-Cell Equalizer Based on Three-Resonant-State Switched-Capacitor Converters for Series-Connected Battery Strings

Abstract: Due to the low cost, small size, and ease of control, the switched-capacitor (SC) battery equalizers are promising among active balancing methods. However, it is difficult to achieve the full cell equalization for the SC equalizers due to the inevitable voltage drops across Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) switches. Moreover, when the voltage gap among cells is larger, the balancing efficiency is lower, while the balancing speed becomes slower as the voltage gap gets smaller. In order to soften these downsides, this paper proposes a cell-to-cell battery equalization topology with zero-current switching (ZCS) and zero-voltage gap (ZVG) among cells based on three-resonant-state SC converters. Based on the conventional inductor-capacitor (LC) converter, an additional resonant path is built to release the charge of the capacitor into the inductor in each switching cycle, which lays the foundations for obtaining ZVG among cells, improves the balancing efficiency at a large voltage gap, and increases the balancing speed at a small voltage gap. A four-lithium-ion-cell prototype is applied to validate the theoretical analysis. Experiment results demonstrate that the proposed topology has good equalization performances with fast equalization, ZCS, and ZVG among cells.

A high efficiency resonant switched-capacitor converter for data center

Abstract: In this paper, a resonant switched-capacitor dc-dc converter is proposed for data center application. The proposed converter possesses features such as high efficiency, high power density and light-weight. Zero current switching (ZCS) can be achieved with the resonant operation, which allows the converter operating under high efficiency. Proper switching device selection and in-depth power loss analysis on different devices have been performed to support better design of the proposed converter. Simulation results are provided in this paper to validate operation principle of the proposed converter. A GaN based prototype with nominal 450W, 54V input and 9V output has been built to verify the theoretical analysis. The maximum power rating of the designed prototype is 600W. Power density of the prototype reaches 750W/in3. When the prototype operating at 253kHz, it achieves 98.55% peak efficiency.

Analysis and Design of a Passive Switched-Capacitor Matrix Multiplier for Approximate Computing

Abstract: A switched-capacitor matrix multiplier is presented for approximate computing and machine learning applications. The multiply-and-accumulate operations perform discrete-time charge-domain signal processing using passive switches and 300 aF unit capacitors. The computation is digitized with a 6 b asynchronous successive approximation register analog-to-digital converter. The analyses of incomplete charge accumulation and thermal noise are discussed. The design was fabricated in 40 nm CMOS, and experimental measurements of multiplication are illustrated using matched filtering and image convolutions to analyze noise and offset. Two applications are highlighted: 1) energy-efficient feature extraction layer performing both compression and classification in a neural network for an analog front end and 2) analog acceleration for solving optimization problems that are traditionally performed in the digital domain. The chip obtains measured efficiencies of 8.7 TOPS/W at 1 GHz for the first application and 7.7 TOPS/W at 2.5 GHz for the second application.

Analysis, Design, and Experimentation of a Dimmable Resonant-Switched-Capacitor LED Driver With Variable Inductor Control

Abstract: This paper proposes a new 48-V dc-fed dimmable LED driver based on a resonant-switched-capacitor topology (RSCT), where the analog-based dimming feature is accomplished by means of a variable inductor (VI). The proposed topology is based on the classic RSCT step-up double mode converter and it provides a simple and cost-effective solution while guaranteeing a wide dimming range. In order to implement an analog-based dimming, the control of the dc current in the LED lamp is required. This technique proposes to replace the resonant inductor by a VI, which will control the rms value of the resonant current, and, therefore, the mean value of the LED lamp current. In order to evaluate the feasibility and performance of this method, a 22-W LED lamp and driver prototypes were built. The most relevant experimental results are presented and briefly described.

Voltage Mode Doherty Power Amplifier

Abstract: This paper presents a new wideband Doherty amplifier technique that can achieve high efficiency while maintaining excellent linearity. By modifying a “forgotten” topology originally proposed by Doherty, a new Doherty amplifier architecture is realized with two voltage mode power amplifiers (PAs) and transformers, thus eliminating a narrowband impedance inverter. The voltage mode PA is implemented using switched capacitor PA techniques. The PA is fabricated in 65-nm low-leakage CMOS and achieves 24-dBm saturated power (at the standard supply voltage) with PAE of 45% at peak power and 34% at 5.6-dB back-off over 750 to 1050 MHz 1 dB bandwidth. With memory-less linearization, the PA can transmit 40 MHz 256-QAM 9 dB peak-to-average power ratio 802.11ac modulation centered at 900 MHz meeting the spectral mask with measured EVM of −34.8 dB and 22% PAE without backing off or equalization.

Analysis and implementation of high-gain non-isolated DC–DC boost converter

Abstract: High step-up DC-DC converters are increasingly required in many industrial applications. Conventional topologies operate at extreme duty cycle, high-semiconductor voltage stress, switching loss, and diode reverse recovery problems. This study presents a new non-isolated high gain, boost converter operating with a modest duty cycle by integrating a coupled inductor and switched capacitor technique. Importantly, the structure of the high-voltage side, together with the switched capacitor, reduces the voltage stress of the power switch to less than one third of the output voltage, which in turn helps to reduce the conduction loss by using a low on-resistance (R ds-on ) switch. The diode voltage stress is less than the output voltage which facilitates faster recovery. Furthermore, the converter employs a passive clamp circuit to recycle the leakage energy. The main switch achieves zero current switching (ZCS) turn-on performance and all diodes achieve (ZCS) turn off reducing reverse recovery related losses. As a result, the circuit exhibits high efficiency performance; which is essential for most modern power electronic applications. In this study, the operational principle and performance characteristics of the proposed converter is presented and validated experimentally with a 250 W, 20V input voltage/190V output voltage prototype circuit.

Efficient Solar Power Management System for Self-Powered IoT Node

Abstract: An efficient micro-scale solar power management architecture for self-powered Internet-of-Things node is presented in this paper. The proposed architecture avoids the linear regulator and presents a complete on-chip switched capacitor-based power converter in order to achieve higher end-to-end efficiency. Unlike traditional architectures, where the harvested energy processes twice, the proposed architecture processes the harvested energy only once before it reaches to the load circuit, irrespective of the ambient conditions. The system efficiency has been improved by ~12% over the traditional architecture. The entire power management system has been designed using 0.18- $\mu \text{m}$ CMOS technology node, and the circuit simulations demonstrate that the proposed architectural changes bring in a system efficiency of 82.4% under different light conditions. In addition to that, a hardware setup is created using commercially available ICs and photovoltaic cells, to validate that the proposed power management system is practically realizable.

A data-driven analysis of capacitor bank operation at a distribution feeder using micro-PMU data

Abstract: In this paper, we conduct a data-driven experimental analysis on capacitor bank switching event at a distribution grid in Riverside, CA using data from two distribution level phasor measurement units, a.k.a, μPMUs. Of particular interest was to detect the capacitor bank switching events based on feeder-level and load-level μPMUs and thus eliminating the need to install separate sensors for the switched capacitor banks. In addition, the operational parameters of capacitor bank is investigated. Moreover, the dynamic effects of capacitor bank switching events is also considered through voltage and current synchrophasor data. This paper takes a first step in using μPMU data to conducting a detailed analysis of how different voltage-levels are affected by capacitor bank switching events in distribution systems.

High step-up DC–DC converter with switched-capacitor and its zero-voltage switching realisation

Abstract: As generally acknowledged, the high step-up DC–DC converter is widely used in the sustainable energy system as the front-end stage of the DC–AC converter. Therefore, a novel high step-up DC–DC converter is proposed in this study. The proposed converter with network of switched-inductor and switched-capacitor can achieve high voltage gain under low duty cycle. Meanwhile, the active switches and diodes suffer from low voltage stress. More importantly, an auxiliary resonant circuit with lower losses and cost is employed to realise zero-voltage switching (ZVS) turned-on and ZVS turned-off for the active switches, resulting in high conversion efficiency. Firstly, the operation principle and steady-state performance are discussed in detail. Then, prototype with power rating of 200 W is built to verify the performance of the proposed converter. The maximum efficiency of the prototype can be up to 96%, and the experimental results agree with the theoretical analysis and the simulation results well.