Additional Auxiliary Circuits Research Articles

Variable-Frequency Control for Totem-Pole Bridgeless Power Factor Correction Converter to Achieve Zero-Voltage Switching Without Zero-Crossing Detection Circuits

The totem-pole bridgeless power factor correction (PFC) converter, known for its advantages including simple topology, capability for zero-voltage switching (ZVS), and low common mode interference, presents an opportunity to enhance the efficiency and environmental friendliness of power systems. However, these converters have issues such as ZVS, requiring zero-crossing detection (ZCD) under circuits’ critical continuous mode (CRM) or additional auxiliary resonant circuits, resulting in increased circuit costs and control complexity. Therefore, this paper proposes a variable switching frequency digital control method to achieve ZVS under a wide operating range without ZCD circuits. At the same time, under the premise of ZVS, an interleaved parallel scheme is adopted to further minimize the current ripple and enhance the quality of the current waveform. Finally, an experimental 2 kW two-phase interleaved totem-pole bridgeless PFC converter prototype is designed to verify that the proposed method is correct and effective. The experimental prototype can reach an efficiency of 97.78%.

Ultra-low-power CMOS ring oscillator with minimum power consumption of 2.9 pW using low-voltage biasing technique

Abstract The need for low-power low-voltage circuit so lutions increases significantly with the rapid spread of wireless sensor network (WSN) and energy harvesting applications. The design of Complementary Metal-Oxide Semiconductor (CMOS) oscillators in sub-threshold region is challenged by the limits of the minimum start-up sup ply voltage, the power available from the harvester, die area, the demand of fully integrated CMOS circuits, and the additional auxiliary circuits that are needed to stabilize the frequency vs a supply voltage V DD. In this work, low-power CMOS oscillator with a simplified design is proposed in order to overcome the aforementioned obstacles. The circuit is designed using 2.5 µm 2-polySi 2-metal CMOS technology from IMB–CNM (CSIC) [1] with a threshold voltage of n-channel metal oxide semiconductor NMOS and p-channel metal oxide semiconductor PMOS transistors of 0.86 and −1.52 V, respectively. The suggested oscillator is capable to start up even in the deep sub-threshold region at V DD of 0.25 V. Accordingly, the minimum power consumption is 2.9 pW with an oscillation frequency of 2 Hz. The circuit can produce a P–P voltage of the oscillation signal equal to the supply voltage within a power supply range of 0.25–1.25 V.

Artificial Neurons Using Ag−In−Zn−S/Sericin Peptide‐Based Threshold Switching Memristors for Spiking Neural Networks

AbstractMemristive devices with threshold switching characteristics can be effectively utilized to mimic biological neurons acting as one of the key building blocks for constructing advanced hardware neural networks. In this work, the emulation of leaky integrate‐and‐fire memristive neuron is realized in one single cell with Ag/Ag−In−Zn−S/silk sericin/W architecture without the need for additional auxiliary circuits. The studied devices demonstrate excellent electrical properties, such as stably repeatable threshold switching, concentratedly low threshold voltage (≈0.4 V), and relatively small device‐to‐device variation. In addition, multiple neural features, such as leaky integrate‐and‐fire neuron functionality and strength‐modulated spike frequency characteristic, have been successfully emulated owing to the forming‐free volatile threshold switching effect. The stable volatile threshold switching behaviors and regular firing event may be attributed to the controllable metallic Ag filamentary mechanism. Furthermore, a solid accuracy of 91.44% of the pattern recognition of Modified National Institute of Standards and Technology (MNIST) data is obtained via a trained spiking neural network (SNN) based on the leaky integrate‐and‐fire behavior of sericin‐based device. These achievements shed light on the fact that employing sericin biomaterials has great application potential in advanced neuromorphic computation.

Design and Analysis of Quasi-Y Source High Gain DC/DC Resonant Converter for Renewable Energy Applications

This paper proposes a magnetically coupled partial resonant isolated quasi-Y source DC/DC converter. Here, to achieve soft switching, there is no additional auxiliary circuits or magnetic components are used. By making use of transformer’s parasitic elements like winding capacitance (Cp) and leakage inductance (Lk1), zero current switching (ZCS) is obtained at the turn-off instant of all MOSFETs. Hence, the converter can operate at a higher frequency, so that compact size and good efficiency are feasible. This converter inherits all the conventional impedance source converter features, and a higher gain is obtained by using three winding coupled inductor and isolation transformer with small shoot-through duty (dST). Hence, the continuous input current (CIC) and galvanic isolation feature of this converter is most suitable for renewable energy applications. Also, the output voltage is regulated by changing the switching frequency. Finally, a 300 W prototype is designed and tested in the laboratory. The simulation, experimental results with mathematical and design analysis are provided.

A Second-Harmonic Suppression Method Based on Differentiated-Capacitance Design for Input-Parallel Output-Series DAB Fed Single-Phase VSI

In the single-phase voltage source inverter (VSI), the instantaneous output power pulsates at twice the line frequency, generating second-harmonic voltage in dc bus. Bulky electrolytic capacitors or additional auxiliary circuits are used in traditional methods, which inevitably limit the system lifetime, efficiency, and power density. In this article, the input-parallel output-series (IPOS) dual active bridge (DAB) with differentiated-capacitance design is adopted as the front-end dc–dc stage. The pulsating power is compensated by the energy gap that the differentiated output capacitors release. The small-signal model of the IPOS DAB fed VSI is built, and based on which, the voltage-complementary algorithm is proposed. Then, the preferred zone and optimization scheme of the main circuit parameters are designed according to the quantitative analysis of the suppressing effect. Furthermore, a 625-W IPOS DAB fed VSI design example is presented and tested. The experimental result shows that at least seven times the capacitance requirements can be reduced without any additional components, and the power quality of both the input current and the output voltage is well guaranteed.

Mutual Inductance Identification of IPT System Based on Soft-Start Process

Accurate estimation of mutual inductance in wireless power transfer (WPT) system is a prerequisite for accurate identification of load parameters, which is critical in system constant output and efficiency tracking control. In this article, a general load decoupling method for WPT system considering soft-start process and battery initial voltage is proposed. Moreover, a double-sided <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> topology is used to explain how to calculate the boundary conditions of load decoupling. Based on the proposed load decoupling method, a mutual inductance identification method is proposed for WPT system with double-sided <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> topology. Within the frequency range recommended, the unique solution of mutual inductance can be obtained by solving high-ordered equivalent impedance equation. In this case, there is no need to discuss the situation for multiple solutions. Based on the WPT prototype, the effectiveness of the proposed load decoupling method is verified, and parameter sensitivity of the identification method is analyzed in detail. Finally, the proposed method is experimentally verified. Results show that high identification accuracy can be achieved even when the coils are misaligned. Compared with the existing identification methods, the proposed method does not need any additional switches and auxiliary circuits, which reduces the complexity and system cost effectively.

Research on Phase-Shifted Full-Bridge Circuit Based on Frequency and Phase-Shift Synthesis Modulation Strategy

The full-bridge converters usually use transformer leakage inductance and parallel resonant capacitors to achieve smooth current commutation and soft switching functions, which can easily cause problems such as energy leakage and significant duty cycle loss. This paper designs a novel full-bridge zero-current (FB-ZCS) converter with series resonant capacitors and proposes a frequency and phase-shift synthesis modulation (FPSSM) control strategy based on this topology. Compared with the traditional parallel resonant capacitor circuit, the passive components used are significantly reduced, the structure is simple, and there is only a slight energy loss. By controlling the charging time of the capacitor, it can be achieved without additional switches or auxiliary circuits. The automatic control of capacitor energy based on input current addresses the low efficiency of the traditional control strategies. This paper introduces its principle in detail and verifies it through simulation. Finally, an experimental prototype was built further to demonstrate the feasibility of the theory through experiments. The module can be applied to a photovoltaic DC collection system using input parallel output series (IPOS) cascade to provide a new topology for large-scale, long-distance DC transmission.

Optimal Design Method of LLC Half-Bridge Resonant Converter Considering Backflow Power Analysis

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> half-bridge converters have been extensively studied in low power industrial applications. However, the phase shift angle between the voltage and current of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant network makes the converter have power circulation, that is, backflow power. The increase of the backflow power will increase the converter conduction loss, which restricts the improvement of the converter efficiency. The existing literature often improves the backflow power from the control aspect, which greatly increases the control complexity. To solve this problem, this article proposes an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> half-bridge resonant converter analysis method that takes the backflow power into account. Based on the analysis of operating mode and ac equivalent model of the converter, backflow power is indirectly characterized by the phase-shift angle of the resonant network voltage and current. Based on this, this article analyzes the internal relationship between resonant parameters and backflow power to reduce backflow power by optimizing resonant parameters. Under the setting operating conditions, converter can achieve zero voltage switching (ZVS) switching, voltage gain conditions, and minimum backflow power. Compared with the existing methods, the proposed optimization method avoids additional auxiliary circuits and control complexity, improves the stability of the circuit. Experimental results verify the accuracy and feasibility of the theoretical analysis.

Improved bidirectional DC/DC converter configuration with ZVS for energy storage system: analysis and implementation

This study proposes a novel design of soft-switching based bidirectional converter for the applications in energy storage systems. By implementing an additional auxiliary circuit to the conventional non-isolated converter, the proposed converter inherits better efficiency with minimised turn-on losses. Moreover, auxiliary switching devices are also soft-switched. This converter can be operated at high power outputs through ZVS turn-on operation. The operation principle, design analysis and experimental results are reported to validate its main features in the study. Furthermore, the performance of this converter is analysed on a 1 kW laboratory prototype for both boost and buck modes.

An SiC MOSFET Based Three-Phase ZVS Inverter Employing Variable Switching Frequency Space Vector PWM Control

In this paper, a variable switching frequency space vector pulsewidth modulation control is proposed. It is used to achieve zero voltage switching (ZVS) for a three-phase grid-connected voltage source inverter with unity power factor. A wide range of ZVS can be realized without any additional sensors, auxiliary circuits, or current zero crossing detection circuits. The switching frequency can be easily calculated by a digital controller. The frequency variation range in a line cycle is only about 1.5 times at any specific load. An LCL filter is used to attenuate the high current ripples at the inverter side, and active damping is adopted to avoid the resonance and reduce the filter power loss. The switching loss can be significantly reduced by using silicon carbide mosfet s so that the conversion efficiency is high. The power density can also be improved due to the high switching frequency and the low inductance value of the filter. The operating principle, design considerations, and loss analyses are discussed in detail. A 3.5-kW simulation and experimental prototype interfacing a 350–400-V dc with a three-phase 110-V ac grid is developed to verify the performance of the proposed control strategy.

A Variable Switching Frequency Space Vector Modulation Technique for Zero-Voltage Switching in Two Parallel Interleaved Three-Phase Inverters

A variable switching frequency space vector modulation control method is proposed in this paper. It is used to achieve zero-voltage switching (ZVS) for two parallel 180° interleaved three-phase grid-connected voltage-source inverters at unity power factor. A wide range of ZVS can be achieved without any additional sensor, auxiliary circuit, or current zero-crossing detection circuit. The carrier wave frequency is easy to be calculated and updated with digital control. The current ripple is precisely predicted and controlled to minimize unnecessary circulation loss. The high current ripple at the inverter side can be considerably canceled by the parallel interleaved configuration. LCL filter is used to further attenuate the current ripple and improve the power quality at the grid side. The switching loss can be significantly reduced especially by using a wide bandgap device with low turn- off loss. The power density is greatly improved owing to the high switching frequency and low component parameters of the filter. A 4.5-kW simulation and experimental prototype interfacing 400 V dc with a three-phase 110-V ac grid is developed to verify the performance of the proposed control strategy.

A Novel Dual-Input ZVS DC/DC Converter for Low-Power Energy Harvesting Applications

In this paper, a novel dual-input dc/dc topology is proposed for low-power energy harvesting applications. The converter is able to interface with two different power sources simultaneously. In the proposed topology, two boost converters are integrated with a shared diode and a filter capacitor, while the gate signals of two power MOSFETs are complimentary with certain dead-bands. The proposed topology may operate either in discontinuous-conduction mode or in hybrid conduction mode. In each operation mode, zero-voltage switching is achieved for both MOSFETs, while zero-current switching is achieved for the power diode, without any additional auxiliary circuit. Theoretical analysis, circuit modeling, and design considerations are also addressed in detail in this paper. Finally, a 10.1-W, 200-kHz prototype is designed and tested to validate the proof of concept. Experimental results are in accordance with the theoretical analysis.

Investigation of Self-Output Voltage Balancing in Input-Parallel Output-Series DC–DC Converter

Voltage balancing control (VBC) between the upper and lower voltages is critical in neutral-point-clamped (NPC) inverter and bipolar dc grid systems due to the structure of cascaded dc capacitors. To address this issue, a high-voltage-gain boost converter with inherent output voltage balancing capability has been recently developed. The main benefit is that it can automatically balance the output voltages without additional control schemes or auxiliary circuits. Nevertheless, the output voltages are slightly unbalanced under certain load conditions, and the poor reverse recovery of body diodes leads to large switching losses due to hard-switching operation. This paper presents the principle of self-output voltage balancing in an input-parallel output-series (IPOS) dc–dc converter and proposes an enhanced self-balancing strategy to eliminate voltage imbalance at all load conditions. The process of implementing the proposed strategy enables zero-voltage switching (ZVS) of all the switches; hence, switching and reverse recovery losses can be significantly reduced. A 2-kW hardware prototype of the IPOS converter was built and tested to verify the feasibility of the proposed scheme.

Full-Bridge ZCS-Converter-Based High-Gain Modular DC-DC Converter for PV Integration With Medium-Voltage DC Grids

This paper presents a high-gain modular input-parallel output-series dc-dc converter for photovoltaic integration with medium-voltage dc grids. A new full-bridge zero-current-switching (FB-ZCS) converter proposed in this paper is used as a fundamental building block. Existing FB-ZCS converters utilize transformer leakage inductance and a shunt-connected resonant capacitor for achieving smooth resonant current commutation and ZCS. The shunt-connected capacitor requires dedicated charging interval in every switching cycle and stores full-load-rated resonant energy at all load/input conditions, resulting in significant duty-cycle loss. Moreover, it suffers from energy leakage through transformer winding and requires overrating. All these factors adversely impact the operation range of the converter, which is important for achieving a wide maximum power point tracking range. Novel improvements in the proposed converter include minimization of duty-cycle loss and resonant capacitor leakage and the realization of the current-adaptive resonant energy storage mechanism, without using additional switches or auxiliary circuits. Operation of the proposed converter is presented and validated with simulation and experimental results.

LLC resonant converter utilizing a step-gap transformer structure for holdup time improvement

This letter presents a current-controlled variable magnetizing inductance of transformer for further improving the holdup time on half-bridge LLC converter. When the input voltage is failed, the magnetizing inductance of transformer can be decreased sharply; therefore, the LLC converter holdup time can be improved without adding additional auxiliary circuit. The mathematic model between magnetizing inductance and step-gap structure of transformer is proposed, and the benefit effects using this step-gap structure of transformer have been verified in this letter. Finally, a 180-W, LLC converter utilizing step-gap structure of transformer has been achieved, and detailed analysis and design of the proposed step-gap structure are described.

Adaptive DC-Link Voltage Control of LLC Resonant Converter

In this study, an adaptive DC-link voltage control of a two-stage switching power supply with LLC resonant converter is proposed. With this control method, the frequency variation range can be reduced and the conversion efficiency under different load conditions can be improved compared with the conventional variable frequency control technique. By operating the LLC resonant converter near its resonant frequency, circulating loss as well as the conduction loss can be reduced and optimal design of LLC resonant converter can be made possible. Moreover, no additional auxiliary circuits are required for the proposed method. The operational principle of the proposed control scheme is verified with a 350 W prototyping circuit. The switching-frequency-variation range is reduced from 12 to 4 kHz and the efficiency is improved from 89.4 % to 90.2 % at full load.

A New Nonisolated High-Voltage-Gain Boost Converter With Inherent Output Voltage Balancing

In this paper, a new nonisolated high-voltage-gain boost converter is proposed. The proposed converter is constructed by adding an additional inductor to a conventional three-level-boost (TLB) converter. When compared with the conventional boost and TLB converters, the proposed converter can achieve higher voltage conversion ratio with reduced voltage and current stresses in the switches. In particular, the proposed converter can reduce the losses of active devices by reducing the current of the switch compared to conventional converters, thus, can achieve high efficiency. In addition, the proposed converter automatically balances the output voltages for an unbalanced load without the need for any additional control strategy or auxiliary circuit. A 2-kW prototype converter was built and tested to verify performances of the proposed converter.

Analysis of Solar PV Application Based on Bidirectional Inverter

Building a DC-DC converter with high step-up, low cost and high efficiency from low DC voltage is the requirement in many applications. It is achieved by employing a front end boost converter based full bridge inverter on bidirectional inverter. In conventional boost converter during device turn-off, voltage overshoot occurs across the semiconductor devices. So, an additional snubber or voltage clamping is required to limit the overshot voltage. It upturns the component’s count and losses making the converter less efficient. The above problem can be avoided by operate the converter with soft-switching method by using secondary modulation technique. Hence, it avoids the need of additional snubber or auxiliary circuit. Soft switching operation is proposed in the bidirectional inverter. Soft switching operation is achieved through the auxiliary circuit, which consist of two auxiliary switches, Front end converter and full bridge inverter. Bidirectional inverter allows current flow in both direction and therefore permits energy flow from the grid to storage when solar energy is not available. The theoretical analysis of the proposed converter is verified using simulation results.

Modeling and implementation of a new ZCS interleaved bidirectional buck–boost DC–DC converter for energy storage systems

This paper deals with a new soft-switched interleaved bidirectional DC–DC converter for energy storage systems. The conventional interleaved bidirectional converter incorporates with an additional auxiliary circuit to attain soft turn-on operation of the main switching devices (IGBTs). The proposed converter is operated in boost and buck modes with zero current switching turn-on operation in order to have minimized turn-on losses by adding auxiliary switches, inductor and capacitors to the main interleaved converter module. The proposed interleaved converter has advantages like reduced switching power losses, device count and improved efficacy. The operating principles and theoretical analysis of the interleaved topology under buck and boost modes are presented in detail. Design simulation analysis and its experimental results were executed using 1-kW, 50-kHz laboratory prototype. The converter’s soft-switching characteristics and its performance were also demonstrated.

An Inherent Zero-Voltage and Zero-Current-Switching Full-Bridge Converter with No Additional Auxiliary Circuits

An inherent zero-voltage and zero-current-switching phase-shifted full-bridge converter with reverse-blocking insulated-gate bipolar transistor (IGBT) or non-punch-through IGBT is proposed in this paper. This converter not only ensures that the switches in the lagging leg works at zero-current switching, but also minimizes circulating conduction loss without any additional auxiliary circuits. A 1.2 kW hardware prototype is designed, fabricated, and tested to verify the proposed topology. The control loop design procedures with small-signal models are also presented. A simple, low-cost, and robust democratic current-sharing circuit is also introduced and verified in this study. The proposed converter is a suitable alternative for compact, cost-effective applications with high-voltage input.