A plug-and-play ripple mitigation approach for DC-links in hybrid systems

© 2016 IEEE.In this paper, a plug-and-play ripple mitigation technique is proposed. It requires only the sensing of the DC-link voltage and can operate fully independently to remove the low-frequency voltage ripple. The proposed technique is nonintrusive to the existing hardware and enables hot-swap operation without disrupting the normal functionality of the existing power system. It is user-friendly, modular and suitable for plug-and-play operation. The experimental results demonstrate the effectiveness of the ripple-mitigation capability of the proposed device. The DC-link voltage ripple in a 110 W miniature hybrid system comprising an AC/DC converter and two resistive loads is shown to be significantly reduced from 61 V to only 3.3 V. Moreover, it is shown that with the proposed device, the system reliability has been improved by alleviating the components' thermal stresses

Reset-sensing quasi-V2 single-inductor multiple-output buck converter with reduced cross-regulation

This paper proposes a reset-sensing quasi-V2 single-inductor multiple-output (SIMO) converter with minimal cross-regulation. The conventional quasi-V2 sensing scheme in SIMO converters suffers from serious cross-regulation which is primarily induced by the load differentiation with unbalanced loads. It is shown that the proposed reset-sensing quasi-V2 control scheme can significantly reduce cross-regulation by completely discharging the feed-forward sensing node to zero volts during the idle phase in Discontinuous Conduction Mode (DCM). The cross-regulation with the conventional quasi-V2 single-inductor dual-output (SIDO) converter for a load current step of 150 mA is experimentally verified to be more than 1.25 mV/mA. By employing the proposed quasi-V2 control method, the experimental results demonstrate that the cross-regulation for a load current step of 150 mA is significantly reduced to within 0.087 mV/mA. Hence, with the proposed scheme, a load transient in one output will have a minimal effect on the DC operating point of another output. This enables separate current control at each individually-driven output of a SIMO converter. © IEEE.published_or_final_versio

T cell cytolytic capacity is independent of initial stimulation strength.

How cells respond to myriad stimuli with finite signaling machinery is central to immunology. In naive T cells, the inherent effect of ligand strength on activation pathways and endpoints has remained controversial, confounded by environmental fluctuations and intercellular variability within populations. Here we studied how ligand potency affected the activation of CD8+ T cells in vitro, through the use of genome-wide RNA, multi-dimensional protein and functional measurements in single cells. Our data revealed that strong ligands drove more efficient and uniform activation than did weak ligands, but all activated cells were fully cytolytic. Notably, activation followed the same transcriptional pathways regardless of ligand potency. Thus, stimulation strength did not intrinsically dictate the T cell-activation route or phenotype; instead, it controlled how rapidly and simultaneously the cells initiated activation, allowing limited machinery to elicit wide-ranging responses

Non-linear feedback control of robust bi-color LED lighting

Light-emitting diode (LED) technology involves highly complex interactions of heat, light, power and color. Dimming a bi-color LED system with color mixing feature will alter the power and junction temperatures, which in turn shift the color spectra of the LEDs. In this paper, a closed-loop control method based on the nonlinear empirical LED model is proposed for decoupling the dimming control and color control of a bi-color system comprising warm-white and cool-white LEDs. The proposed control scheme has been successfully implemented to provide highly precise and independent control of dimming and correlated color temperature (CCT). Even considering significant changes in ambient temperature, the maximum errors in luminous flux and CCT employing the proposed method are around 3% and 1.78% respectively while the corresponding errors using an existing linear duty-cycle control method are 20% and 27.5% respectively.link_to_OA_fulltex

Plug-and-play voltage ripple mitigator for DC links in hybrid AC-DC power grids with local bus-voltage control

In this paper, a straightforward plug-and-play voltage ripple mitigator (RM) is proposed. Unlike existing voltage ripple reduction methods, the proposed device can be attached to the dc link of a hybrid ac-dc power system without modifying the host system itself. In particular, a local bus-voltage control scheme is employed to achieve the plug-and-play operation. With the requirement of the dc-link voltage measurement only, this device can be operated as a standalone module. Theoretical analysis and experimental work on a boost-type power factor correction rectification system have been successfully performed to validate the effectiveness of the ripple-mitigating function, the hot-swap operation and the nonintrusive property of the RM. Practical results obtained from a 110-W miniature hybrid ac-dc power system comprising an ac/dc converter and two resistive loads are included to demonstrate some of the functions of the RM

Buck-boost single-inductor multiple-output (SIMO) high-frequency inverters for medium-power wireless power transfer

In this paper, a non-isolated buck-boost single-inductor multiple-output (SIMO) DC-AC inverter for driving multiple independent high-frequency AC outputs of medium power, is proposed. Compared with traditional bridge-type inverters, the proposed buck-boost SIMO inverter achieves (i) a smaller component count, (ii) fully independent power control of its outputs, (iii) better scalability in increasing the number of AC output channels, and (iv) higher power efficiency. Operating in pseudo-continuous conduction mode (PCCM), the rated power of each output channel of this inverter can be high while attaining zero cross-regulation. The scalability factor of the proposed inverter is formally investigated and the theoretical maximum number of AC outputs is analytically derived. The targeted application of the proposed inverter is for driving multiple transmitter coils to realize versatile multi-device medium-power wireless power transfer. A hardware prototype of a single-inductor three-output (SITO) buck-boost inverter delivering a medium power of 8.4 W per output channel has been constructed. It is experimentally verified that precise and independent current regulation of individual transmitter coil is achievable with the proposed inverter

Precise Dimming and Color Control of LED Systems Based on Color Mixing

This paper proposes a closed-loop nonlinear scheme for precisely controlling the luminosity and correlated color temperature (CCT) of a bicolor adjustable light-emitting diode (LED) lamp. The main objective is to achieve a precise and fully independent dimming and CCT control of the light mixture emitted from a two-string LED lamp comprising warm-white and cool-white color LEDs, regardless of the operating conditions and throughout the long operating lifetime of the LED lamp. The proposed control method is formulated using the nonlinear empirical LED model of the bicolor white LED system. Experimental results show that with the proposed closed-loop nonlinear approach, both CCT and dimming control of the bicolor lamp is significantly more accurate and robust to ambient temperature variations, ambient light interference, and LED aging than the conventional linear approach used in existing products. The maximum error in luminous flux employing the proposed closed-loop nonlinear approach is 3%, compared with 20% using the closed-loop linear approach. The maximum deviation in CCT is only 1.78%, compared with 27.5% with its linear counterpart

Single-Stage AC/DC Single-Inductor Multiple-Output LED Drivers

Various ac/dc LED driver topologies have been proposed to meet the challenges of achieving a compact, efficient, low-cost, and robust multistring LED lighting system. These LED drivers typically employ a two-stage topology to realize the functions of ac/dc rectification and independent current control of each LED string. The choice of having two stage conversions involves additional hardware components and a more complicated controller design process. Such two-stage topologies suffer from a higher system cost, increased power loss, and large form factor. In this paper, a single-stage ac/dc single-inductor multiple-output LED driver is proposed. It uses only one single inductor and N + 1 active power switches (N being the number of LED strings) with reduced component count and smaller form factor. The proposed driver can achieve both functions of ac/dc rectification with a high power factor and precise independent current control of each individual LED string simultaneously. A prototype of an ac/dc single-inductor triple-output LED driver is constructed for verification. Experimental results corroborate that precise and independent current regulation of each individual LED string is achievable with the proposed driver. A power factor of above 0.99 and a peak efficiency of 89% at 30-W rated output power are attainable

Harnessing CURATE.AI for N-of-1 Optimization Analysis of Combination Therapy in Hypertension Patients: A Retrospective Case Series

10.1002/adtp.202100091Advanced Therapeutics4102100091-210009