In response to fast-growing high-voltage (HV) power IC market demands, this article presents a tri-state double step-down (DSD) power converter to achieve direct 12V/24V- to-1V dc–dc power delivery ...with high efficiency and high power density. By taking advantage of the benefits from both three-level and DSD converter topologies, the converter allows the use of lower voltage rating power devices and thus facilitates high switching frequency operation with smaller power passives. An online flying capacitor voltage (Formula Omitted) rebalancing scheme is introduced to optimize switching nodes voltages and minimize power path mismatch for improved reliability and efficiency. During startup transients, an in-situ precharge rate regulation technique manages the charging process on flying capacitors precisely in avoidance of potential device breakdown. An IC prototype of this design was fabricated using a 180 nm HV bipolar-CMOS-DMOS (BCD) process with an active area die of 6.3 mm2. At 3-W output power, a chip power density of 476 mW/mm2 is accomplished. The online Formula Omitted rebalancing reduces voltage mismatch between the flying capacitors by 16.7%. The converter achieves peak efficiencies of 88.3% and 92.1% for 24V/1V and 12V/1V conversion, respectively.
To unlock the full potential of monolithic gallium nitride (GaN) power integrated circuits, this article explores the feasibility of developing efficient and reliable on-chip gate driving and level ...shifting solutions, which fundamentally facilitate the on-chip implementation of GaN power circuits. As results, a self-bootstrapped hybrid (SBH) gate driving scheme and its circuitry are developed, which achieve rail-to-rail dynamic gate driving in normal operation and robust static gate driving in large transient moments. Meanwhile, an auto-lock auto-break (A2) level shifting technique is proposed to convert the gate driving control signals from low-voltage (LV) to high-voltage (HV) domains, without requiring any p-type devices. This enables the on-chip operation of high-side power switches and makes synchronous rectification possible. On-chip temperature sensing is implemented to monitor junction temperature directly at low circuit complexity and power and cost overheads, facilitating thermal protection at high power density. Furthermore, on-die dead-time control is presented to optimize zero voltage switching (ZVS) for high efficiency. All the techniques and circuits are demonstrated in a monolithic asymmetrical half-bridge (AHB) power converter on a GaN-on-SOI process. It achieves direct 48V/1V dc-dc conversion with a maximum load current of 5 A and a current density of 1.1 A/mm2. Among the existing monolithic GaN power ICs capable of on-chip synchronous rectification, it achieves the shortest rising- and falling-edge gate driving delays of 11.6 and 14.0 ns. Despite running doubled numbers of on-chip power transistors and gate drivers, it only consumes 70-mW static power.
This article presents a new power converter capable of direct 48-V/1-V dc-dc conversion with high efficiency. The proposed three-path four-state (3P4S) hybrid switching power stage enables high ...switching frequency (<inline-formula> <tex-math notation="LaTeX">f_{\mathrm {SW}} </tex-math></inline-formula>) operation and minimizes power passives by significantly reducing power switch voltage stress. To address the issues of power delivery path imbalances and potential device breakdown, an adaptive flying capacitor voltage (<inline-formula> <tex-math notation="LaTeX">V_{\mathrm {CF}} </tex-math></inline-formula>) rebalancing technique is introduced that improves design robustness and eliminates the need for direct floating <inline-formula> <tex-math notation="LaTeX">V_{\mathrm {CF}} </tex-math></inline-formula> sensing. Additionally, a dual-edge deadtime (<inline-formula> <tex-math notation="LaTeX">t_{\mathrm {dead}} </tex-math></inline-formula>) modulation with elastic <inline-formula> <tex-math notation="LaTeX">t_{\mathrm {dead}} </tex-math></inline-formula> control at switching nodes optimizes converter efficiency across different input voltage and load conditions. An IC prototype of the design was fabricated and tested with input voltage <inline-formula> <tex-math notation="LaTeX">V_{\mathrm {IN}} </tex-math></inline-formula> ranging from 12 to 48 V, delivering up to 4 W of power at 1-V <inline-formula> <tex-math notation="LaTeX">V_{\mathrm {O}} </tex-math></inline-formula>. It achieves peak efficiency of 90.7% and 85.6% for 12-V/1-V and 48-V/1-V power conversion, respectively, at an effective switching frequency of 4.5 MHz, which is based on a three-phase operation with each phase at 1.5 MHz. The adaptive <inline-formula> <tex-math notation="LaTeX">V_{\mathrm {CF}} </tex-math></inline-formula> rebalancing technique reduces <inline-formula> <tex-math notation="LaTeX">V_{\mathrm {CF}} </tex-math></inline-formula> imbalance error by up to 65.1%. Overall, the proposed 3P4S hybrid switching power converter offers an efficient and robust solution for direct dc-dc conversion with a wide <inline-formula> <tex-math notation="LaTeX">V_{\mathrm {IN}} </tex-math></inline-formula> range.
There has been a classic design trade-off between electromagnetic interference (EMI) and power efficiency in switching power circuits historically. This work explores the technical strategies that ...well balance this trade-off. In particular, an emulated Miller plateau tracking scheme is proposed to identify critical di / dt and dv / dt instants, which are susceptible to load current and power input voltage conditions. An adaptive strength gate driving scheme facilitates low di / dt and high dv / dt switching operation, which leads to the targeted EMI and switching loss optimization. A switching power converter IC prototype was implemented in a 0.35-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> high-voltage (HV) Bipolar-CMOS-DMOS (BCD) process. Operating at 10 MHz, the converter regulates an output at 5 V with 6-W power range, accommodating a wide input supply voltage ranging from 5 to 40 V. It achieves above 70% efficiency over 95.8% of the full power range, with a peak efficiency of 81.4% at 1.25 W. With the proposed strategies, the peak EMI of the converter is reduced by 19.23 dB<inline-formula> <tex-math notation="LaTeX">\mu \text{V} </tex-math></inline-formula> in Band B (< 30 MHz) and 9 dB<inline-formula> <tex-math notation="LaTeX">\mu \text{V} </tex-math></inline-formula> in Band C/D (>30 MHz), with only 2.44% efficiency penalty.
In modern automotive electronics, there are uprising demands on enhanced power density and reliability for power delivery systems. To achieve high power density, single-stage gallium-nitride ...(GaN)-based power converters at high switching frequencies (<inline-formula> <tex-math notation="LaTeX">f_{\mathrm {SW}} </tex-math></inline-formula>) are highly desirable but face formidable reliability challenges in the aspects of electromagnetic interference (EMI) suppression and consequential output voltage <inline-formula> <tex-math notation="LaTeX">V_{O} </tex-math></inline-formula> regulation. To address these challenges, this article presents a GaN-based switching power converter that employs an anti-aliasing multi-rate spread-spectrum modulation (MR-SSM) technique for EMI suppression and an in-cycle adaptive zero-voltage switching (ZVS) technique to minimize switching power losses. Compared with classic fixed-rate SSM (FR-SSM), the proposed MR-SSM technique spreads EMI spectra in a wider frequency range without aliasing spikes and, thus, reduces peak EMI more effectively. To improve efficiency, an elastic dead-time (<inline-formula> <tex-math notation="LaTeX">t_{\mathrm {dead}} </tex-math></inline-formula>) control facilitates in-cycle ZVS despite of a continuously changing <inline-formula> <tex-math notation="LaTeX">f_{\mathrm {SW}} </tex-math></inline-formula>. An IC prototype based on this design was fabricated on a 180-nm HV BCD process, with an active die area of 0.87 mm 2 . The converter can handle a variable automotive-use battery voltage from 5 to 24 V and delivers up to 1.2-W power to a regulated output <inline-formula> <tex-math notation="LaTeX">V_{O} </tex-math></inline-formula> at 1 V, with a peak efficiency of 90.2%. It accomplishes a 29% further peak EMI reduction compared with the FR-SSM counterpart.
We report results of systematic molecular-dynamics computations of the elastic properties of single-crystalline tungsten containing structural defects, voids and overpressurized He nanobubbles, ...related to plasma exposure of tungsten serving as a plasma-facing component (PFC) in nuclear fusion devices. Our computations reveal that the empty voids are centers of dilatation resulting in the development of tensile stress in the tungsten matrix, whereas He-filled voids (nanobubbles) introduce compressive stress in the plasma-exposed tungsten. We find that the dependence of the elastic moduli of plasma-exposed tungsten, namely, the bulk, Young, and shear modulus, on its void fraction follows a universal exponential scaling relation. We also find that the elastic moduli of plasma-exposed tungsten soften substantially as a function of He content in the tungsten matrix, following an exponential scaling relation; this He-induced exponential softening is in addition to the softening caused in the matrix with increasing temperature. A systematic characterization of the dependence of the elastic moduli on the He bubble size reveals that He bubble growth significantly affects both the bulk modulus and the Poisson ratio of plasma-exposed tungsten, while its effect on the Young and shear moduli of the plasma-exposed material is weak. Our findings contribute directly to the development of a structure–property database that is required for the predictive modeling of the dynamical response of PFCs in nuclear fusion devices.
RNA silencing (RNAi) has a well-established role in anti-viral immunity in plants. The destructive eukaryotic pathogen Phytophthora encodes suppressors of RNAi (PSRs), which enhance plant ...susceptibility. However, the role of small RNAs in defense against eukaryotic pathogens is unclear. Here, we show that Phytophthora infection of Arabidopsis leads to increased production of a diverse pool of secondary small interfering RNAs (siRNAs). Instead of regulating endogenous plant genes, these siRNAs are found in extracellular vesicles and likely silence target genes in Phytophthora during natural infection. Introduction of a plant siRNA in Phytophthora leads to developmental deficiency and abolishes virulence, while Arabidopsis mutants defective in secondary siRNA biogenesis are hypersusceptible. Notably, Phytophthora effector PSR2 specifically inhibits secondary siRNA biogenesis in Arabidopsis and promotes infection. These findings uncover the role of siRNAs as antimicrobial agents against eukaryotic pathogens and highlight a defense/counter-defense arms race centered on trans-kingdom gene silencing between hosts and pathogens.
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•Phytophthora infection increases production of a pool of secondary siRNAs in Arabidopsis•Secondary siRNAs from a PPR gene cluster contribute to defense against Phytophthora•PPR-siRNAs potentially silence Phytophthora transcripts to confer resistance•Phytophthora effector PSR2 suppresses the biogenesis of PPR-siRNAs to promote infection
The role of plant RNAi in defense against eukaryotic pathogens is unclear. Hou et al. report that Arabidopsis produces a reservoir of secondary siRNAs that confer resistance against the notorious pathogen Phytophthora, likely through trans-kingdom gene silencing. However, a Phytophthora effector defeats this defense by specifically inhibiting secondary siRNA biogenesis.
In mobile applications, power density highly affects mobility, cost, form factor, and battery time. To improve power density, high switching frequency operation is highly desirable for a power ...converter. However, with high switching frequency, switching power loss increases significantly, compromising efficiency and battery time. This article presents an on-chip 3-level DC-DC converter, using all NMOS devices as power switches, which reduces switching power loss and silicon cost. To facilitate the all-NMOS power stage operation and enhance the robustness to input supply variation, a 3-switch boost-strap gate driver is designed. Meanwhile, an interception coupling dead-time (ICDT) control is introduced to minimize dead-time related power loss. An integrated circuit prototype was fabricated using a 0.35 μm CMOS process. Robustly working with a variable input voltage from 3 to 6 V, it regulates a programmable power output from 0.4 to 1.6 V, with a maximum power efficiency of 85.5% over a full power range of 800 mW and a maximum power density of 1.07 W/mm 2 . Thanks to the ICDT control, it achieves a 0.5 ns dead-time over a full-load range of 500 mA.
Tobacco smoke exposure dramatically alters DNA methylation in blood cells and may mediate smoking-associated complex diseases through effects on immune cell function. However, knowledge of smoking ...effects in specific leukocyte subtypes is limited. To better characterize smoking-associated methylation changes in whole blood and leukocyte subtypes, we used Illumina 450K arrays and Reduced Representation Bisulfite Sequencing (RRBS) to assess genome-wide DNA methylation. Differential methylation analysis in whole blood DNA from 172 smokers and 81 nonsmokers revealed 738 CpGs, including 616 previously unreported CpGs, genome-wide significantly associated with current smoking (p <1.2x10-7, Bonferroni correction). Several CpGs (MTSS1, NKX6-2, BTG2) were associated with smoking duration among heavy smokers (>22 cigarettes/day, n = 86) which might relate to long-term heavy-smoking pathology. In purified leukocyte subtypes from an independent group of 20 smokers and 14 nonsmokers we further examined methylation and gene expression for selected genes among CD14+ monocytes, CD15+ granulocytes, CD19+ B cells, and CD2+ T cells. In 10 smokers and 10 nonsmokers we used RRBS to fine map differential methylation in CD4+ T cells, CD8+ T cells, CD14+, CD15+, CD19+, and CD56+ natural killer cells. Distinct cell-type differences in smoking-associated methylation and gene expression were identified. AHRR (cg05575921), ALPPL2 (cg21566642), GFI1 (cg09935388), IER3 (cg06126421) and F2RL3 (cg03636183) showed a distinct pattern of significant smoking-associated methylation differences across cell types: granulocytes> monocytes>> B cells. In contrast GPR15 (cg19859270) was highly significant in T and B cells and ITGAL (cg09099830) significant only in T cells. Numerous other CpGs displayed distinctive cell-type responses to tobacco smoke exposure that were not apparent in whole blood DNA. Assessing the overlap between these CpG sites and differential methylated regions (DMRs) with RRBS in 6 cell types, we confirmed cell-type specificity in the context of DMRs. We identified new CpGs associated with current smoking, pack-years, duration, and revealed unique profiles of smoking-associated DNA methylation and gene expression among immune cell types, providing potential clues to hematopoietic lineage-specific effects in disease etiology.
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