Switch Junction Research Articles

A Bootstrap Drive and Level Shifting Method for Buck-boost Converter with NMOS as the Main Switch Transistor

In the design of DC-DC power supply, compared with a P-type metal oxide semiconductor field effect transistor (PMOS) with the same width-to-length ratio, N-type metal oxide semiconductor field effect transistor (NMOS) as the main switching transistor greatly reduces the on-off loss and improves the conversion efficiency of the system. This article introduces a gate voltage bootstrap and level shifter circuit for a Buck-Boost DC-DC converter with NMOS main switching transistor. The drive voltage between the gate and the source pole of the main switch transistor can be stabilized, which is independent of the switch junction voltage (V SW) and solves the problem that the drive voltage of the gate is too high or too low due to the influence of the bootstrap voltage in the traditional structure. Based on the 0.18 μm BCD process, the circuit design and physical implementation of the proposed method are verified. The test results show that the bootstrap drive circuit functions normally and the bootstrap drive voltage is about 5 V when the input voltage is 2.9~4.5 V and the output voltage is −2~-5 V. In addition, the proposed gate-level shifting circuit can reduce the drive delay of the main switch transistor to less than 12 ns.

Modified Voltage Matching Control and Inductor Current Injections for Hybrid-Bridge-Based DAB Converter

In this paper, a modified voltage matching control and current injections method are proposed for the hybrid-bridge-based dual active bridge (DAB) converter, which is aimed at achieving full load range zero voltage switching (ZVS) with consideration of all the switch junction capacitors. With the proposed modified voltage matching control, the non-ZVS region under backward power transfer (even without the junction capacitors) is eliminated. The analysis of the operation principle, ZVS model analysis considering junction capacitors and current injection method are discussed in detail. In addition, the problem of discontinues ZVS region with consideration of the switch junction capacitors is solved through injecting two current sources with paralleling one inductor to the transformer. Finally, the effectiveness of the proposed solution is verified by experimental results on a 100kHz, 1kW converter prototype.

Magnetizing Current Injection Based Push-Pull Dual Active Bridge Converter With Optimized Control to Achieve Full Load Range ZVS for the Distributed Generation System

To reduce greenhouse gas emissions, the distributed generation system is an approach worth investigating. With fewer switches, the push-pull circuits are suited for low-voltage and high-current applications, such as the distributed generation system. In this paper, a modified push-pull dual active bridge (PPDAB) dc-dc converter and its optimized control are proposed to achieve full load range zero voltage switching (ZVS). Considering the switch junction capacitors, the added current is injected by the magnetizing inductance to achieve full load range ZVS. Based on the RMS value of transformer current, the optimized control strategy is proposed to enhance the system efficiency with the precondition of achieving full load range ZVS of all switches. The working principles, ZVS region analysis, and design of key parameters are discussed in detail. Finally, the effectiveness of the proposed method for the PPDAB converter is verified by the results of a laboratory prototype.

A wide zero-voltage-switching range with low reactive power modulation strategy for LCL resonant three-phase dual active bridge DC–DC converter in renewable energy generations

LCL resonant three-phase dual active bridge (LCL-TPDAB) dc–dc converter is progressively used in renewable energy systems due to the advantages of low circulating reactive power and wide voltage regulation. Conventional dual-phase-shift (DPS) modulation can effectively reduce the circulating reactive power of the converter, but it cannot achieve zero-voltage-switching (ZVS) of all switches, which increases switching losses and generates electromagnetic interference. To solve the above problems, an optimized modulation strategy based on phase-shift plus duty cycle (PSPDC) control is proposed in this paper. Firstly, the mathematical model of the LCL-TPDAB converter with the PSPDC modulation is established by harmonic analysis. Then, the relationship between the ZVS boundaries and the control variables is determined by analyzing the soft-switching characteristics. In order to accurately describe the ZVS boundaries, the impact of switch junction capacitance is considered in the analysis. Further, an optimized modulation strategy is proposed, which can achieve ZVS for all switches and low reactive power in the whole operating range. Furthermore, the offline particle swarm optimization (PSO) algorithm is introduced to acquire the optimal control variables in the operation of the converter. Finally, a 1.5 kW experimental prototype is applied to verify the effectiveness and excellence of the proposed optimized modulation strategy, where the efficiencies are improved in the whole operating range.

Single-Phase Single-Stage Bidirectional DAB AC–DC Converter With Extended ZVS Range and High Efficiency

Conventional analyzations on the dual active bridge-based single-phase single-stage ac–dc converter relies on the line-piecewise model with which power switches are viewed as ideal and the commutation process between the top and bottom switch in each bridge leg are ignored. Although many soft-switching have been proposed, the effects of the commutation process make them inaccurate because of the difference between the line-piecewise model-based theoretical waveforms and the real ones. In this article, the commutation process is described in view of the nonlinearity of the switch junction capacitance, the commutation delay time and the dead time of each bridge leg. Furthermore, the control variables are compensated with the commutation delay time so that the zero voltage switching (ZVS) range can be extended widely. The variable dead time control helps to achieve critical turn-on, reducing the body diode conduction loss. Finally, a 1-kW prototype is built to evaluate the proposed method can achieve extend ZVS and achieve high conversion efficiency.

Role of EXO1 nuclease activity in genome maintenance, the immune response and tumor suppression in Exo1D173A mice.

DNA damage response pathways rely extensively on nuclease activity to process DNA intermediates. Exonuclease 1 (EXO1) is a pleiotropic evolutionary conserved DNA exonuclease involved in various DNA repair pathways, replication, antibody diversification, and meiosis. But, whether EXO1 facilitates these DNA metabolic processes through its enzymatic or scaffolding functions remains unclear. Here, we dissect the contribution of EXO1 enzymatic versus scaffolding activity by comparing Exo1DA/DA mice expressing a proven nuclease-dead mutant form of EXO1 to entirely EXO1-deficient Exo1−/− and EXO1 wild type Exo1+/+ mice. We show that Exo1DA/DA and Exo1–/– mice are compromised in canonical DNA repair processing, suggesting that the EXO1 enzymatic role is important for error-free DNA mismatch and double-strand break repair pathways. However, in non-canonical repair pathways, EXO1 appears to have a more nuanced function. Next-generation sequencing of heavy chain V region in B cells showed the mutation spectra of Exo1DA/DA mice to be intermediate between Exo1+/+ and Exo1–/– mice, suggesting that both catalytic and scaffolding roles of EXO1 are important for somatic hypermutation. Similarly, while overall class switch recombination in Exo1DA/DA and Exo1–/– mice was comparably defective, switch junction analysis suggests that EXO1 might fulfill an additional scaffolding function downstream of class switching. In contrast to Exo1−/− mice that are infertile, meiosis progressed normally in Exo1DA/DA and Exo1+/+ cohorts, indicating that a structural but not the nuclease function of EXO1 is critical for meiosis. However, both Exo1DA/DA and Exo1–/– mice displayed similar mortality and cancer predisposition profiles. Taken together, these data demonstrate that EXO1 has both scaffolding and enzymatic functions in distinct DNA repair processes and suggest a more composite and intricate role for EXO1 in DNA metabolic processes and disease.

Power-Estimation-Based Synchronous Rectification Solution for Bidirectional DAB-LLC Converter

An LLC-DAB bidirectional converter with reduced switch count as a DC-DC transformer (DCX) is proposed in this paper. It can achieve voltage regulation, full load range zero voltage switching (ZVS) for eight main switches and wide load range ZVS for four auxiliary switches, with consideration of the switch junction capacitors under different power direction. A part portion of total power is transferred through an auxiliary DAB circuit to achieve voltage regulation and bidirectional power conversion. The main power is transferred through LLC circuit with an easy PWM scheme achieving high conversion efficiency. Different from the existing LLC-DAB DCX structure, the two secondary side transformer outputs are in parallel, and connected to the same full-bridge circuit. In this way, the auxiliary DAB circuit can not only adjust the output voltage, but also can inject current into the secondary side to help achieving ZVS of switches without synchronous rectifier (SR) circuit. The converter operation principle is analyzed under different power directions, and ZVS is analyzed with the consideration of all the switch junction capacitors. Based on the analysis, the design consideration is introduced. Finally, a 2-kW prototype with 750V input and 400V output is built up to verify the effectiveness of the proposed solution.

An Optimized DPS Control for Dual-Active-Bridge Converters to Secure Full-Load-Range ZVS With Low Current Stress

It is a challenge for dual-active-bridge (DAB) converters to take a good balance between full-load-range zero-voltage switching (ZVS) and control complexity with a wide voltage range. Dual-phase-shift (DPS) control can extend the ZVS range greatly compared with single-phase-shift (SPS) control, and it has fewer control variables with reduced operation modes compared with triple-phase-shift (TPS) control. However, with conventional DPS control, at least a pair of switches will be operated under hard switching within a large power range, which severely reduces the efficiency, especially at the high switching frequency. To solve this problem, based on the Lagrange multiplier method (LMM), an optimized DPS control utilizing magnetizing current is proposed. In this article, the magnetizing inductance is designed to create the possibility of full-load-range ZVS achievement for all power switches. Based on ZVS analysis considering switch junction capacitors and power characteristics analysis, a power control law premised on full-load-range ZVS achievement is proposed to achieve low current stress. Finally, the effectiveness of the proposed solution is verified by experimental results obtained with a 500-W, 250-kHz gallium–nitride (GaN)-based prototype.

An LLC-DAB Bidirectional DCX Converter With Wide Load Range ZVS and Reduced Switch Count

An LLC dual active bridge (DAB) bidirectional converter with reduced switch count as a dc–dc transformer (DCX) is proposed in this article. It can achieve voltage regulation, full load range zero voltage switching (ZVS) for eight main switches and wide load range ZVS for four auxiliary switches, with consideration of the switch junction capacitors under different power direction. A part portion of total power is transferred through an auxiliary DAB circuit to achieve voltage regulation and bidirectional power conversion. The main power is transferred through LLC circuit with an easy PWM scheme achieving high conversion efficiency. Different from the existing LLC -DAB DCX structure, the two secondary side transformer outputs are in parallel, and connected to the same full-bridge circuit. In this way, the auxiliary DAB circuit can not only adjust the output voltage, but also can inject current into the secondary side to help achieving ZVS of switches without synchronous rectifier circuit. The converter operation principle is analyzed under different power directions, and ZVS is analyzed with the consideration of all the switch junction capacitors. Based on the analysis, the design consideration is introduced. Finally, a 2-kW prototype with 750 V input and 400 V output is built up to verify the effectiveness of the proposed solution.

A Bidirectional Symmetrical C4LC-DCX Resonant Converter With Power Limitation Capability

To achieve the maximum efficiency of resonant converter under wide voltage conversion gain range, two stage conversion, which adopts the resonant converter operating at resonant frequency to work as a dc–dc transformer (DCX) in isolation stage, is a preferred solution. This article proposes a bidirectional C4LC resonant converter to work as a DCX. The structure of the topology is totally symmetrical, and two auxiliary inductors are used to achieve full load range zero-voltage-switching (ZVS) for all the power switches under bidirectional power flow. Unlike conventional ZVS analysis, the ZVS of the proposed converter is analyzed with considerations of all the switch junction capacitors and load. The clamping diodes are also combined in the topology which can help achieve natural power limitation in case of overload and limit the startup current. Even though four inductors and one transformer are illustrated in the topology, all these magnetic components can be simplified and manufactured with one external inductor and one conventional transformer. Meanwhile, the converter operates at a fixed frequency and adopts the synchronous pulsewidth modulation (PWM) modulation, which can achieve constant voltage gain and automatically change the power direction without synchronous rectifier (SR) current detection. Finally, the experimental results from a 1-kW prototype verify the effectiveness of the proposed converter.

Design and Evaluation of Synthetic RNA-Based Incoherent Feed-Forward Loop Circuits.

RNA-based regulators are promising tools for building synthetic biological systems that provide a powerful platform for achieving a complex regulation of transcription and translation. Recently, de novo-designed synthetic RNA regulators, such as the small transcriptional activating RNA (STAR), toehold switch (THS), and three-way junction (3WJ) repressor, have been utilized to construct RNA-based synthetic gene circuits in living cells. In this work, we utilized these regulators to construct type 1 incoherent feed-forward loop (IFFL) circuits in vivo and explored their dynamic behaviors. A combination of a STAR and 3WJ repressor was used to construct an RNA-only IFFL circuit. However, due to the fast kinetics of RNA–RNA interactions, there was no significant timescale difference between the direct activation and the indirect inhibition, that no pulse was observed in the experiments. These findings were confirmed with mechanistic modeling and simulation results for a wider range of conditions. To increase delay in the inhibition pathway, we introduced a protein synthesis process to the circuit and designed an RNA–protein hybrid IFFL circuit using THS and TetR protein. Simulation results indicated that pulse generation could be achieved with this RNA–protein hybrid model, and this was further verified with experimental realization in E. coli. Our findings demonstrate that while RNA-based regulators excel in speed as compared to protein-based regulators, the fast reaction kinetics of RNA-based regulators could also undermine the functionality of a circuit (e.g., lack of significant timescale difference). The agreement between experiments and simulations suggests that the mechanistic modeling can help debug issues and validate the hypothesis in designing a new circuit. Moreover, the applicability of the kinetic parameters extracted from the RNA-only circuit to the RNA–protein hybrid circuit also indicates the modularity of RNA-based regulators when used in a different context. We anticipate the findings of this work to guide the future design of gene circuits that rely heavily on the dynamics of RNA-based regulators, in terms of both modeling and experimental realization.

Optimized EPS Control to Achieve Full Load Range ZVS With Seamless Transition for Dual Active Bridge Converters

Dual active bridge (DAB) converters are widely studied for applications requiring isolation, bidirectional power flow and high efficiency. To solve the problem of limited zero voltage switching (ZVS) range and achieve seamless transition for extended-phase-shift (EPS) control, the magnetizing current is utilized and an optimized control law is proposed in this article. With the injection of magnetizing current, the two ZVS regions under EPS control will be creatively intersected with a large region, instead of disconnected or just intersected at a particular point as in previous studies. The ZVS model considering switch junction capacitors, ZVS region analysis with magnetizing current injection and power transfer characteristics are analyzed. Based on these analyses, the optimized EPS control is proposed to achieve full load range ZVS, low root-mean-square current and maximum transmission power capability. A 250 kHz, 500 W GaN-based DAB prototype is built to verify the effectiveness of the proposed solution.

Bidirectional Clamping-Based H5, HERIC, and H6 Transformerless Inverter Topologies With Reactive Power Capability

Transformerless inverters (TLIs) are competently accepted for photovoltaic (PV) applications because of their high efficiency, reduced size, and lower cost. But in the absence of a transformer, there exists a galvanic connection between the PV array to ground and it results in the flow of hazardous leakage current. Several TLI topologies have been proposed in the literature with decoupling circuits to reduce the leakage current. Among those H5, Heric, and H6 topologies are the most popular and widely accepted TLIs. Nevertheless, the effect of switch junction capacitances was not considered in the common-mode voltage analysis, which inevitably causes excess leakage current. Also, reactive power capability cannot be accomplished with traditional pulsewidth modulation (PWM) schemes due to the absence of a bidirectional current path during the freewheeling period. Therefore, in this article, a bidirectional clamping (BDC) based H5, Heric, and H6 TLI topologies are proposed with improved PWM schemes. BDC branch reduces the leakage current by clamping the inverter terminal voltages to half of the dc-link voltage during the freewheeling period and the improved PWM schemes ensure the bidirectional current path while operating in negative power region. The performance of both traditional and proposed topologies is tested with MATLAB simulations and further justified with experimental results.

A New All-Solid-State Bipolar High-Voltage Multilevel Generator for Dielectric Barrier Discharge

Dielectric barrier discharge (DBD) can produce a large amount of active particles and has many applications in the industry. In order to study the effect of different rising edges, falling edges, and waveform voltages on DBD, a novel all-solid-state bipolar multilevel high-voltage pulse generator is proposed. Compared with other topologies, the proposed system can achieve more levels of waveforms with fewer switches. This article introduces the structure and working principle of the system in detail. Through PSPICE simulation, it is found that the capacitance of the switch junction will generate prepulse for the output. To solve this problem, an improved control strategy is proposed. Finally, a nine-level test prototype is built, which can work steadily under different loads. Meanwhile, different types of output waveforms are allowed to be generated when the control is adjusted. Finally, the main circuit uses 20 power switches and nine energy storage capacitors and this system can achieve a maximum output voltage of ±4 kV, adjustable frequency, and a total of 19 level voltage output (including 0 level).

An Improved Hybrid-Bridge Transformerless Inverter Topology With Bidirectional Clamping and Reactive Power Capability

Transformerless inverters are getting popular in distributed photovoltaic power generation (PVPG) system due to its light weight, low cost, and higher efficiency in power conversion. However, the production of leakage current leads to severe electromagnetic interference and operational insecurity, which declines the reliability and efficiency of the overall system. Besides that many of the topologies have been addressed with real power injection capabilities in the literature. Therefore, in this paper, an improved hybrid-bridge (IH-B) inverter for transformerless PVPG system is proposed with 1) reduced leakage current by abolishing the fluctuations in common-mode voltage (CMV) due to switch junction capacitances and 2) reactive power capability with a modified sinusoidal pulsewidth modulation technique. This topology is constructed with the combination of bidirectional clamping branch and hybrid-bridge (H-B) inverter topology to maintain CMV at half of the dc-link voltage and ensure better quality of output waveforms at different power factors of the grid. Further, MATLAB simulation results of the IH-B and H-B topologies are presented and compared to prove the potential benefits of the proposed topology. Finally, a 500W prototype model is built and tested to validate the effectiveness of the IH-B topology in reduction of leakage current and reactive power capability.

Reliability evaluation of buck converter based on thermal analysis

The design, which is based on the concept of reliability, is impressive. In power electronic circuits, the reliability design has been shown to be useful over time. Moreover, power loss in switches and diodes plays a permanent role in reliability assessment. This paper presents a reliability evaluation for a buck converter based on thermal analysis of an insulated-gate bipolar transistor (IGBT) and a diode. The provided thermal analysis is used to determine the switch and diode junction temperature. In this study, the effects of switching frequency and duty cycle are considered as criteria for reliability. A limit of 150°C has been set for over-temperature issues. The simulation of a 12 kW buck converter (duty cycle = 42% and switching frequency = 10 kHz) illustrates that the switch and diode junction temperature are 117.29°C and 122.27°C, respectively. The results show that mean time to failure for the buck converter is 32,973 hours.

Research on transformerless dual‐buck full‐bridge grid‐connected inverter with H5‐type for PV systems

To eliminate the common-mode leakage current in the transformerless grid-connected photovoltaic (PV) system, inspired by the newly-developed embedded-switch H5 topology and dual-buck full-bridge grid-connected inverter (GCI), a novel transformerless dual-buck full-bridge GCI with H5-type (TDFGI-H5) topology for PV systems is firstly presented. Then, the operating modes and common-mode leakage current of TDFGI-H5 modulated by unipolar sinusoidal pulse-width modulation are analysed. The analysis result shows that TDFGI-H5 has the advantages of the three-level output, no shoot-through problem, high reliability, and can completely meet the condition of eliminating common-mode leakage current. Aim at the problem of the common-mode leakage affected by the switches' junction capacitances, the effect of switch's junction capacitance is explored in detail when TDFGI-H5 is in the transient process that converts from non-decoupling states to decoupling states. Finally, the results of experiment verify the correctness of the theoretical analysis.

Fundamental frequency region-based thermal control of power electronics modules in high power motor drive

The reliability of power modules in motor drive is closely related to its thermal cycling. Especially in low speed and high output power condition, the thermal performance can be even worse. In this paper, a fundamental frequency region-based thermal control strategy is presented. Firstly, the model for high power drive thermal cycling calculation is established. With the electro-thermal model, power switch junction temperature and its number of power cycles can be mapped with fundamental frequency. Then, the fundamental frequency region can be divided by the junction temperature fluctuation. Based on the obtained frequency region, a switching frequency control method is proposed to improve the thermal fluctuation and reliability. A comparison results with and without the proposed control method are given to validate the switching frequency hysteresis control strategy and the improvement on system power cycling capability.

From chip to inverter: Electro-thermal modeling and design for paralleled power devices in high power application

Power loss and thermal stress of semiconductor components are closely related to the reliability of high power inverter. In addition to the inverter electrical parameters, the size of semiconductor is also an important factor in inverter electro-thermal performance. In this paper, an electro-thermal model correlated with chip area and chip paralleled number is built to calculate the power switch loss and junction temperature. Then, the relationship between chips size and inverter loss/thermal behaviors can be established by this model, enabling more flexible in chip design to optimize the inverter efficiency and thermal loading. Finally, the inverter electro-thermal design procedure is established to properly select the chip area and number in a power switch. As a case study, the optimal chip paralleled structure in the high power inverter is estimated and the results are compared under varying inverter output frequency. By selecting the chip area and number in the target region, junction temperature can maintain in the limited range.

Research on Grid-Connected and Off-Grid Switching Distributed Photovoltaic Power System

Photovoltaic power system (PV system) includes grid-connected and off-grid (islanding) types. With the improvement of power supply reliability, it is necessary to provide distributed PV power system with functions of grid-connection and off-grid operation, which as well as being easily switched. This research comparative analyzes on model of AC bus and model of DC bus of grid-connected and off-grid PVsystem and presents the control strategy. In order to safely operate and seamlessly switch grid-connected and off-grid, PV system is furnised constant-power control and constant-voltage frequency control with switching operation. Additionally, the switch junction for off-grid and the public supply system must be connected to the synchronization device for controling system of PV system therefore the PV system can be safely operated and switch from off-grid to grid-connected can be smoothly and rapidly.