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Hysteretic modulators have superior dynamic performance, and they also help reduce the number of output capacitors without sacrificing the transient response. For proper hysteretic operation, the voltage ripple is required to be piecewise linear and noise free. With modern computational integrated circuits lower supply voltage with tight regulation requirements, the output voltage ripple is both small and noisy. The synthetic ripple modulator (SRM) allows proper hysteretic operation even with a small and corrupted output voltage ripple. This paper discusses the dynamic behavior of the SRM. Small-signal characteristics of the modulator are derived. An easy-to-use numerically efficient model has been developed to accurately predict the small- and large-signal behavior of the converter driven by the SRM. The model is able to predict the small-signal behavior of the SRM up to half the switching frequency with sufficient accuracy. It can predict the same large-signal responses as real-time simulation, but at two orders of magnitude less in computation time. Laboratory tests on a 1.8 V/20 A single-phase prototype shows good correlation between experimental results and theoretical predictions both in frequency and time domain. Index Terms--Buck converter, fast transient response, hysteretic, ripple control, voltage regulator module.

This article proposes a novel single-phase bridgeless Cuk-derived power factor corrected (PFC) converter with reduced component count for on-board EV charging application. The unique feature of this proposal is to design and operate the output inductor of the converter in discontinuous current mode for the complete power range to attain PFC naturally at ac mains, thereby not requiring the input voltage and input current sensing, which reduces the converter cost, and improves the power density as well as converter robustness to high-frequency noise. The converter control is very simple in operation and easy in implementation with only a single sensor-based voltage control loop. The semiconductor components voltage stress of the proposed power converter is lower when compared to the traditional Cuk converter. The simulation results from PSIM 11 and experimental results are given by testing a proof-of-concept hardware laboratory prototype to demonstrate the high performance of PFC operation of the proposed converter. [ABSTRACT FROM AUTHOR]

This article proposes a systematic synthesis method to identify the optimum converter topology for a specified voltage conversion ratio. This gain-oriented converter synthesis is formulated as an inverse problem around the inductor flux balance equations. The proposed synthesis method consists of two processes. A set of distinct converter topologies is first synthesized from the specified voltage conversion ratio by obtaining the solutions for a set of six inverse equations in twelve unknowns. The optimal topology for any intended application can be identified based on the desired performance metrics. The complete synthesis method is illustrated with quadratic buck–boost gain as an example. In total, 25 distinct topologies are synthesized using the first process, and their feasibility is validated by PLECS simulation. In total, three case studies are reported to explain the second process. Ground-referenced output and the minimum number of switches are used as the first two selection criteria in all the case studies. Minimum peak inductor current, minimum component stress factor, and minimum voltage and current stress are the third selection criterion in Case Studies-1, 2, and 3, respectively. The steady-state operations of two optimal converters selected in Case Study-1 were verified experimentally. [ABSTRACT FROM AUTHOR]

This article proposes a voltage-fed zero-voltage-switched topology based on the push–pull converter. The proposed converter uses the leakage inductance of the transformer to transfer power from input to output. Phase-shift modulation strategy is used to control the flow of this power. A coupled LC regenerative snubber-based energy recovery circuit reclaims the trapped energy in the leakage inductance. The snubber circuit also ensures soft-switched operation and reduces the voltage stress across the semiconductor switches. The power-flow equation is characterized and experimentally verified for the proposed converter. The gate control signals are implemented using an field-programmable gate array (FPGA). A 240-W prototype validates the steady-state behavior and snubber design equations. [ABSTRACT FROM AUTHOR]

This article presents an analytical method to derive an optimum converter topology for a specified voltage conversion ratio (G). An optimum topology for any given G can be identified after obtaining the comprehensive pool of converter topologies. This gain-oriented converter synthesis is formulated as an inverse problem around the principle of inductor flux balance. A step-by-step method is proposed to solve the inverse problem and obtain a comprehensive set of non-redundant converter topologies for any given voltage conversion ratio. Consequently, the number of possible converter topologies for a specified voltage conversion ratio is also identified. The optimum converter topology is chosen from the comprehensive set based on three selection criteria, viz., ground-referenced output, a minimum number of switches, and minimum peak inductor current. The proposed solution methodology is illustrated with quadratic boost and quadratic buck gains as case studies. A comprehensive set of non-redundant topologies is identified in both cases. The steady-state operations of all the topologies are studied with PLECS simulation. Based on the selection criteria, an optimum topology is selected in each case, and their steady-state operation is verified experimentally using lab-developed prototypes. [ABSTRACT FROM AUTHOR]

Nonisolated dc–dc converters are fundamental building blocks in the power supply for a wide range of applications. To cater to this heterogeneity in applications, development of dc–dc converters with suitable voltage conversion ratio (G) is imperative. Given a converter topology, G can be found out uniquely by using the principle of inductor volt-second balance, and the process of obtaining the voltage conversion ratio from the topology is simple. In contrast, the inverse problem, i.e., the process of obtaining the converter topology for a given voltage conversion ratio (G) is a challenging task, and the obtained topology is also not unique. This article presents a simple method to obtain a family of converter topologies from a required voltage conversion ratio. This method utilizes the principle of inductor flux balance as a synthesis tool. The step-by-step procedure to synthesize the converter topologies is outlined. To illustrate the efficacy of the proposed method, it is applied to synthesize various quadratic buck–boost topologies, and a family of converters is identified. Operation and feasibility of two novel topologies, identified by the proposed theory, are verified experimentally. [ABSTRACT FROM AUTHOR]

The inverse problem for the dc–dc converters refers to synthesizing converter topologies from a specified voltage gain expression. Though the flux balance principle is widely used in the analysis of dc–dc converters, its application as a synthesis tool has not been explored. This letter describes a mathematical approach to synthesize converter topologies from a required voltage gain expression by utilizing the principle of inductor flux balance. At first, the general form of gain expression for second-order converters is derived. From the general form of gain expression, the inverse problem is formulated by identifying the governing equations. The mathematical formulation of the inverse problem and highlighting challenges involved in solving it are the primary subjects of this article. To outline these challenges, a probable solution strategy of this inverse problem is presented. In order to derive a converter topology, at first, the appropriate flux balance equations are determined, and then the circuit topology is derived to establish the required flux balance. In contrast to the forward problem, the solution to the inverse problem is neither direct nor unique. Hence, getting the optimum closed-form solution to this inverse problem is an open-ended challenge with many possible approaches. [ABSTRACT FROM AUTHOR]

Unity power factor rectifiers find applications in modern utility systems and consumer electronic devices. However, a dedicated rectifier is required for a given load. In this study, a Unity Power Factor (UFP) power block is described which can generate two DC outputs, one buck and one boost, with a reduced number of switches and associated driver circuits. The topology adapts well with conventional control as it retains the dynamic behaviour of a buck and boost topology. While supplying simultaneous loads it exhibits minimal cross-regulation interference between the outputs. The controller implementation for the proposed power block is described and its difference with the conventional Power Factor Correction (PFC) controller is outlined. The topology along with its control to regulate the outputs and force UPF operation are validated using a 200 W prototype with 110 V utility input and 180–24 V DC outputs. [ABSTRACT FROM AUTHOR]

The relative share of renewable energy, specifically the solar photovoltaic (PV), is increasing exponentially in the world electric energy sector. This is a cumulative result of reduction in the cost of solar panels, improvement in the panel efficiency, and advancement in the associated power electronics. Among different types of PV plants, installation of small-scale rooftop PV is growing rapidly due to direct end-user benefits and lucrative governmental incentives. There are various standards developed in regards to grid integration of PVs and other distributed generations (DGs). Different power converter topologies are developed to interface the PV panel with the utility grid. To keep up with the stringent regulations imposed by the standards, various control strategies and grid synchronization methods have been developed. This review article amalgamates and summarizes all of the aforementioned aspects of a grid-integrated PV system including various standards, power stage architectures, grid synchronization methods, operation under extreme events, and control methodologies, pertaining to small-scale PV plants. This article will help freshman researchers to gain some familiarity with the topic and introduce them to some of the key issues encountered in this field. [ABSTRACT FROM AUTHOR]

This paper describes a theory to synthesize nonisolated dc–dc converters. It uses the fundamental flux balance equation across the inductors of a converter as a starting point in this synthesis process. The flux balance equations are the linear equations of the input voltage, capacitor voltages, and duty cycle (D). The coefficients of these linear equations can be selected from a finite set of choices. These choices define the converter topologies that are subsequently used to synthesize a converter. The synthesis procedure applies to a converter of multiple order. All the possible converters are identified for a first-order topology. In the case of second-order converters, all the choices of the flux balance equation are defined. Based on these choices, three new quadratic topologies are derived and verified to demonstrate the effectiveness of the theory. The procedure to synthesize a converter from a given voltage conversion ratio is also outlined. [ABSTRACT FROM AUTHOR]

Due to the pulsating power at the inverter output terminals, the passive storage elements of the boost stage of the current-fed switched inverter (CFSI) contain a power frequency harmonic component (100 Hz), apart from dc and switching frequency components. In prior designs, the second harmonic component is suppressed by increasing the size of the input filter inductor and capacitor or by using additional circuits. This paper presents a complete characterization of a control-based approach to suppress the power frequency harmonic component in the input inductor current of a CFSI. It also presents a comprehensive characterization of the harmonic power redistribution. Using the proposed approach, it is demonstrated that the inductor value of a CFSI is reduced by 61% for the same peak-to-peak ripple. This leads to an improvement in the conversion ratio, efficiency, and power density of the overall converter. A SiC MOSFET-based CFSI with 75-kHz switching frequency is used to verify the proposed design philosophy. [ABSTRACT FROM AUTHOR]

Dielectric elastomer generator (DEG) is a special variable capacitor generator used to harvest electrical energy from ambient mechanical vibrations, such as waves, building vibrations, wind, and human movement. The DEG, by virtue of its variable capacitance, converts the applied mechanical energy into electrical form. For successful energy harvesting, the DEG requires controlled charging and discharging operations. Thus, the energy harvesting circuits, used to charge and discharge the DEG, must work in tandem with the mechanical vibrations. The energy harvested during a single cycle of DEG operation increases with an increase in the DEG operating voltage. Hence, energy harvesting circuits must drive the DEG at high voltage levels. These two requirements make the energy harvesting circuit design a challenging job. In this paper, a novel energy harvesting system is proposed to drive the DEG without needing a position sensor, a high-voltage source, or a high turns ratio transformer. The theory of the proposed scheme is explained and validated with experiments performed on a prototype DEG. The control implemented leads to a special intermittent operation of the energy recovery circuit, which is also introduced. 2.597 mJ energy was harvested from a single elastomer film of 10 cm diameter with 2.3 nF capacitance in relaxed condition. [ABSTRACT FROM AUTHOR]

Inductor current is an important feedback parameter in synchronous buck converters (SBCs). It is used for overcurrent protection, current sharing among interleaved modules, and current-mode feedback regulation, among others. While implementing a digital controller, inductor current is sensed and fed into the controller through a high sampling frequency analog to digital converter (ADC). As the switching frequency of the converter becomes higher, the need for an even higher sampling frequency ADC also goes up, which is a distinct disadvantage in terms of the overall cost. This paper discusses a simple current estimation technique that avoids use of any expensive current sensor and high sampling frequency ADCs. The paper shows that in a buck converter, inductor current can be estimated by tracking the width of the switch node voltage. Implementation and limitations of the proposed current estimation scheme are discussed in detail. The proposed method is validated using a 3.3 V–15 A SBC prototype and results show the estimation technique is accurate within 5% with a converter switching frequency of 800 kHz. In order to prove the effectiveness of the technique in feedback regulation, the current estimation technique is used to implement average current mode and hysteretic current mode control on a SBC. To prove the effectiveness of the proposed current estimation scheme, it is used in closed-loop control of the SBC to verify the dynamic responses, such as start-up transient, step change in load, and reference. [ABSTRACT FROM AUTHOR]

Multioutput converters with single input source are currently studied as an alternative to conventional dc–dc topologies in order to improve power density in low-power multiload applications. This paper reviews three different ways in which a boost topology can be customized to supply multiple outputs. The first way uses a charge-sharing approach using individual switches to distribute inductor energy to different capacitors. The second method of creating a multiport converter (MPC) combines two converters with similar front end to generate two outputs using only one controlled switch. Using this method, a boost converter can be combined with single–ended primary–inductor converter (SEPIC), Cuk, and current source converter topologies. The third method uses time multiplexing of switches to produce two regulated ports and is referred to as switched-boost action. This method uses relatively less number of switches and allows regulation and control of all the outputs. Practical utility of switched-boost action based MPC is reported in this paper. This switched-boost MPC is applied to a renewable power converter system to interface a solar panel, a battery, and home loads to produce a 12-V and a 48-V bus. The 12-V bus is interfaced to battery and capable of optimally charging the battery in constant current–constant voltage (CC-CV) mode. The converter is demonstrated to operate with solar panel as it supplies a 12-V battery and a 48-V load bus. When the solar power is not available, the converter automatically goes into a mode in which the 12-V battery supplies the loads on the 48-V bus. [ABSTRACT FROM AUTHOR]

Impedance source inverters (ISIs) are gaining attention due to features such as single-stage conversion, buck-boost capability, and inherent shoot-through protection. To maintain the required ac output voltage, typically ISIs are operated at a higher dc-link voltage due to constrained modulation index. This also increases voltage stress across capacitors and switches of the converter. This voltage stress is approximately double compared to that of voltage source inverter with preboost stage (Boost-VSI). To mitigate this problem, a new pulsewidth modulation (PWM) scheme for the active-front-end based ISIs (AFE-ISIs) is proposed. The proposed scheme enables the ISIs to produce high ac gain with lower voltage stress across the capacitor and switches. In other words, the proposed scheme blends the advantages of Boost-VSI into ISIs. With the new PWM scheme, there are also reductions in output voltage total harmonic distortion, switching frequency ripple in the inductor current, and power loss in the converter. A prototype of the current-fed switched inverter, an AFE-ISI, is designed, and the proposed PWM scheme is implemented. Experimental results obtained are in accordance with the proposed theory and show that the voltage stress has reduced from 325 V to 203 V for an ac output of 110 V. [ABSTRACT FROM AUTHOR]

Elastomer is an electroactive polymer, which finds popular application in the field of actuators and artificial muscles. Though elastomers are popularly used as actuators, with proper modification to their operating cycle, they can also be used as generators. These dielectric elastomer generators (DEGs), due to properties such as high energy density and frequency independent operation are suitable for different energy harvesting applications. In this letter, a simplified electrical model of the DEG is proposed, which can be used in various simulation platforms to verify compatibility of DEG with electrical circuits and predict its behavior. Detailed process of deriving the model parameters from a physical DEG is discussed at length. Performance of the proposed model is verified by comparing its behavior with a prototype DEG-based energy harvesting system having a DEG of 1.3 nF capacitance. The proposed DEG model was simulated with similar conditions and the simulation results have shown good accuracy with the experimental results. [ABSTRACT FROM PUBLISHER]

Capacitively coupled power transfer (CCPT) uses electrostatic mechanism to deliver power from a stationary transmitter to a mobile receiver. The authors study various aspects of this technology including physical limitations that are encountered to increase power transfer. They characterise the impact of input voltage, dielectric area, and permittivity of the dielectric material in realisation of CCPT system. It is observed that the peak voltage and VA ratings of the capacitors are affected by the choice of the aforementioned parameters. Air as a dielectric medium leads to low power density. A high permittivity material instead of air dielectric can be used to improve power density. This strategy will make the CCPT technology non-contactless, because a physical contact exists between the transmitter and receiver. However, this contact is different from an ohmic contact. A high power density CCPT system is realised using ceramic dielectric surfaces. Issues encountered in system realization are discussed including automatic resonant frequency tracking. Detailed mathematical models under resonance and off-resonance operation are proposed. The models are validated using simulations and experimental results. A low cost multilayer ceramic capacitor (MLCC) based high power-density transfer surface is realised. Results show that 35 W can be easily transferred using a set of 12 mm2 capacitive surfaces and 32 V source. [ABSTRACT FROM AUTHOR]

The Z-source inverter (ZSI) employs an LC impedance network between the main inverter bridge and the power source. The unique feature of the ZSI is that it can operate either in buck or boost mode with a wide range of obtainable output voltages from a given input voltage. This topology also exhibits better electromagnetic-interference noise immunity when compared to a traditional voltage-source inverter (VSI). However, the LC impedance network of ZSI significantly increases the size and cost of the power converter and can make it unsuitable for low-power applications. This paper proposes a novel topology called switched boost inverter (SBI) which exhibits similar advantages of ZSI with lower number of passive components and more active components compared to ZSI. The steady-state and small-signal analyses of SBI, along with its pulsewidth modulation (PWM) control strategies, have been discussed in this paper. This paper also presents a comparison of SBI and ZSI with the same input and output parameters. The theoretical analysis given in this paper has been validated using a laboratory prototype of SBI, and the experimental results are presented for verification. The experimental harmonic spectrum of the inverter's output voltage with the proposed PWM technique is also plotted and compared with that of a traditional VSI. All the experimental results show good correlation between theory and experiments. [ABSTRACT FROM PUBLISHER]

Switched boost inverter (SBI) is a single-stage power converter derived from Inverse Watkins Johnson topology. Unlike the traditional buck-type voltage source inverter (VSI), the SBI can produce an ac output voltage that is either greater or less than the available dc input voltage. Also, the SBI exhibits better electromagnetic interference noise immunity when compared to the VSI, which enables compact design of the power converter. Another advantage of SBI is that it can supply both dc and ac loads simultaneously from a single dc input. These features make the SBI suitable for dc nanogrid applications. In this paper, the SBI is proposed as a power electronic interface in dc nanogrid. The structure and advantages of the proposed SBI-based nanogrid are discussed in detail. This paper also presents a dq synchronous-reference-frame-based controller for SBI, which regulates both dc and ac bus voltages of the nanogrid to their respective reference values under steady state as well as under dynamic load variation in the nanogrid. The control system of SBI has been experimentally validated using a 0.5-kW laboratory prototype of the SBI supplying both dc and ac loads simultaneously, and the relevant experimental results are given in this paper. The low cross regulation and the dynamic performance of the control system have also been verified experimentally for a 20% step change in either dc or ac load of SBI. These experimental results confirm the suitability of the SBI and its closed-loop control strategy for dc nanogrid applications. [ABSTRACT FROM AUTHOR]