Switching Time Delay Optimization for “SiC+Si” Hybrid Device in a Phase-leg Configuration

Compared to SiC MOSFET, the switching loss of Si IGBT is much higher due to its slow switching speed and tail current. Si IGBT/SiC MOSFET hybrid switch device can reach to optimal performance with low static and dynamic loss, which can improve the current capacity of SiC devices and reduce the power loss of Si IGBT based converters. With the separated gate control signals, the switching moments of the two devices can be controlled independently to ensure Si IGBT under zero-voltage switching (ZVS) conditions. This measurement tends to reduce the switching loss of Si IGBT. However, the switching time delay between these two devices has significant impacts on its power loss. In this paper, the switching time delay optimization method is proposed to minimize the power loss of the hybrid switch. The static and dynamic characteristics of Si IGBT/SiC MOSFET hybrid-paralleled switch are studied, and a generalized power loss model for hybrid switch is developed. The influence of switching time delay on the characteristics of hybrid switch is analyzed and verified through double pulse tests in a phase-leg configuration. The experimental results show that the optimal turn-on delay time is that the two devices turn on at the same time and the turn-on loss can be reduced by about 73% compared with the solely Si IGBT and by about 52% compared with the solely SiC MOSFET. While the optimal turn-off sequence is that the Si IGBT turns off ahead of the SiC MOSFET. Under the proposed optimal turn-off delay time of the hybrid switch, the turn-off loss is reduced by about 61.4%. This optimization strategy is used in a Buck converter to verify the superiority of the SiC/Si hybrid switch and the optimal switching sequence. Simulation results show that the optimal switching sequence is consistent with theoretical analysis, and the efficiency is improved by 2.5% compared with Buck converter using solely Si IGBT

Parameters Design and Optimization of SiC MOSFET Driving Circuit with Consideration of Comprehensive Loss and Voltage Stress

In conventional parameters design, the driving circuit is usually simplified as an RLC second-order circuit, and the switching characteristics are optimized by selecting parameters, but the influence of switching characteristics on the driving circuit is not considered. In this paper, the insight mechanism for the gate-source voltage changed by overshoot and ringing caused by the high switching speed of SiC MOSFET is highlighted, and we propose an optimized design method to obtain optimal parameters of the SiC MOSFET driving circuit with consideration of parasitic parameters. Based on the double-pulse circuit, we evaluated the influence of main parameters on the gate-source voltage, including driving voltage, driving resistance, gate parasitic inductance, and stray inductance of the power circuit. A SiC-based boost PFC is constructed and tested. The test results show that the switching loss can be reduced by 7.282 W by using the proposed parameter optimization method, and the over-voltage stress of SiC MOSFET is avoided

An optimized parameter design method of SiC/Si hybrid switch considering turn-off current spike

In order to reduce the switching loss of SiC MOSFET/Si IGBT (SiC/Si) hybrid switch, the switching mode that turn off the Si IGBT prior to the SiC MOSFET is generally adopted to achieved the zero-voltage switching operation of IGBT. The minority carrier in N-base region of the IGBT are recombined in the form of exponential attenuation due to the conductivity modulation effect. When the SiC MOSFET is turned off, if the carrier recombination process of the IGBT is not finished, it needs to bear a large collector–emitter voltage change rate, resulting in apparent current spike. This current spike will increase the current stress of the device and produce additional turn-off loss. The equivalent model of double pulse test circuit of SiC/Si hybrid switch considering parasitic parameters is established, and the turn-off transient process is given analytically. The influence of turn-off delay time, circuit parameters and working conditions on current spike are analysed quantitatively. Combined with the consideration of device stress and comprehensive turn-off loss, an optimized circuit design method of SiC/Si hybrid switch considering turn-off current peak is proposed, which provides theoretical and design guidance for high reliability and high efficiency SiC/Si-based converters

Evaluation and Suppression Method of Turn-off Current Spike for SiC/Si Hybrid Switch

SiC MOSFET/Si IGBT (SiC/Si) hybrid switch usually selects the gate control pattern that SiC MOSFET turns on earlier and turns off later than Si IGBT, with the aim of making the hybrid switch show excellent switching characteristics of SiC MOSFET and reduce switching loss. However, when SiC MOSFET turns off, the fast slew rate of drain source voltage causes the current spike in Si IGBT due to the effects of parasitic capacitance charging and carrier recombination, which will produce additional turn-off loss, thus affecting the overall efficiency and temperature rise of the converter. Based on the double pulse test circuit of SiC/Si hybrid switch, the mathematical model of the turn-off transient process is established. The effects of the remnant carrier recombination degree of Si IGBT, the turn-off speed of SiC MOSFET and the working conditions on the turn-off current spike of hybrid switch are evaluated. Although adjusting these parameters can reduce the turn-off current spike somewhat, additional losses will be introduced. Therefore, a new method to suppress the turn-off current spike is proposed to balance the power loss and current stress

Structural reconstruction of the catalytic center of LiPDF through multiple scattering calculation with MXAN

Abstract Peptide deformylase (PDF, EC 3.5.1.27) is essential for the normal growth of eubacterium but not for mammalians. Recently, PDF has been studied as a target for new antibiotics. In this paper, X-ray absorption spectroscopy was employed to determine the local structure around the zinc ion of PDF from Leptospira Interrogans in dry powder, because it is very difficult to obtain the crystallized sample of Li PDF. We performed X-ray absorption near edge structure (XANES) calculation and reconstructed successfully the local geometry of the active center, and the results from calculations show that a water molecule (Wat1) has moved towards the zinc ion and lies in the distance range to coordinate with the zinc ion weakly. In addition, the sensitivity of theoretical spectra to the different ligand bodies was evaluated in terms of goodness-of-fit

The first X-ray polarimetric observation of the black hole binary LMC X-1

We report on an X-ray polarimetric observation of the high-mass X-ray binary LMC X-1 in the high/soft state, obtained by the Imaging X-ray Polarimetry Explorer (IXPE) in October 2022. The measured polarization is below the minimum detectable polarization of 1.1 per cent (at the 99 per cent confidence level). Simultaneously, the source was observed with the NICER, NuSTAR and SRG/ART-XC instruments, which enabled spectral decomposition into a dominant thermal component and a Comptonized one. The low 2-8 keV polarization of the source did not allow for strong constraints on the black-hole spin and inclination of the accretion disc. However, if the orbital inclination of about 36 degrees is assumed, then the upper limit is consistent with predictions for pure thermal emission from geometrically thin and optically thick discs. Assuming the polarization degree of the Comptonization component to be 0, 4, or 10 per cent, and oriented perpendicular to the polarization of the disc emission (in turn assumed to be perpendicular to the large scale ionization cone orientation detected in the optical band), an upper limit to the polarization of the disc emission of 1.0, 0.9 or 0.9 per cent, respectively, is found (at the 99 per cent confidence level).Comment: 12 pages, 9 figures, 4 tables. Accepted for publication in MNRA

Optimal design of kelvin source SiC MOSFET based PFC considering inductor parasitic capacitance and source mutual inductance

SiC MOSFET with Kelvin source has the advantage of high switching speed due to the lack of common source parasitic inductance. However, the high switching speed will make the parasitic parameters affect the performance of PFC converter obviously. Thus, it is necessary to analyze the influence of parasitic parameters on PFC circuits. The input PF model and switching energy loss model are established considering the inductor parasitic capacitance, and the influence of inductor parasitic capacitance on input PF and switching energy loss is analyzed. The switching energy loss model was established considering source mutual inductance, and the influence of source mutual inductance on switching energy loss was analyzed. Then we obtained the optimum value range of inductor parasitic capacitance and Kelvin source mutual inductance. The simulation and experimental results are given to verify the correctness of the mathematical model and analysis

Switching characteristics analysis and power loss minimization of SiC BJT based on dual power supply RC driving circuit

As a current driven power device, SiC BJT needs effective driving scheme, but the present schemes are either complicated or not parameter optimized. In this paper we give an optimized parameter design method based on dual power supply RC driving circuit. First, the detailed switching process of SiC BJT considering the loop parasitic parameters is presented. Then, the influence of the accelerating capacitor on the switching loss and driving loss of SiC BJT is analyzed. The theoretical and simulation analysis shows that as the accelerating capacitor increases, the driving loss of SiC BJT increases proportionally, while the switching loss decreases less. Finally, the switching process of SiC BJT was investigated experimentally at various accelerating capacitor values from 3.3 nF to 94 nF. It was found that with the increase of the accelerating capacitor, the total loss during the switching process first decreases and then increases. The total loss minimization during the switching process of SiC BJT can be achieved through properly selecting the accelerating capacitor

TIGAR cooperated with glycolysis to inhibit the apoptosis of leukemia cells and associated with poor prognosis in patients with cytogenetically normal acute myeloid leukemia

Abstract Background Cancer cells show increased glycolysis and take advantage of this metabolic pathway to generate ATP. The TP53-induced glycolysis and apoptosis regulator (TIGAR) inhibits aerobic glycolysis and protects tumor cells from intracellular reactive oxygen species (ROS)-associated apoptosis. However, the function of TIGAR in glycolysis and survival of acute myeloid leukemia cells remains unclear. Methods We analyzed TIGAR expression in cytogenetically normal (CN-) AML patients and the correlations with clinical and biological parameters. In vivo and in vitro, we tested whether glycolysis may induce TIGAR expression and evaluated the combination effect of glycolysis inhibitor and TIGAR knockdown on human leukemia cell proliferation. Results High TIGAR expression was an independent predictor of poor survival and high incidence of relapse in adult patients with CN-AML. TIGAR also showed high expression in multiple human leukemia cell lines and knockdown of TIGAR activated glycolysis through PFKFB3 upregulation in human leukemia cells. Knockdown of TIGAR inhibited the proliferation of human leukemia cells and sensitized leukemia cells to glycolysis inhibitor both in vitro and in vivo. Furthermore, TIGAR knockdown in combination with glycolysis inhibitor 2-DG led leukemia cells to apoptosis. In addition, the p53 activator Nutlin-3α showed a significant combinational effect with TIGAR knockdown in leukemia cells. However, TIGAR expression and its anti-apoptotic effects were uncoupled from overexpression of exogenous p53 in leukemia cells. Conclusions TIGAR might be a predictor of poor survival and high incidence of relapse in AML patients, and the combination of TIGAR inhibitors with anti-glycolytic agents may be novel therapies for the future clinical use in AML patients

DCAG in Combination with HLA-mismatched Stem-Cell Microtransplantation for the Treatment of Refractory or Relapsed AML in Elderly Patients

No reference salvage regimen has been established in elderly patients with refractory or relapsed acute myeloid leukemia (AML). In our study, six patients older than 60 diagnosed with refractory or relapsed AML receivednbspprogrammed infusions of granulocyte colony-stimulating factor (G-CSF)ndashmobilized HLA-mismatched donor peripheral-blood stem cells after the DCAG regimen of chemotherapy treatment. The complete remission (CR) rate was 33.33% after the first therapy cycle. The median recovery times of neutrophils and platelets were 12 days and 14.5 days, respectively. No acute graft-versus-host disease (GVHD) or chronic GVHD was observed in any of the patients. The median overall survival (OS) time was 6.2 months (range, 0.9-26.2), and one out of six patients (16.7%) achieved persistent CR. In Conclusion, DCAG regimenin in combination with microtransplantation was well tolerated and showed a promising clinic efficacy in elderly patients with refractory or relapsed AML