Wide Range Of Conversion Ratios Research Articles

Regulated Resonant Switched-Capacitor Point-of-Load Converter Architecture and Modeling

This article presents a novel control system for a regulated resonant switched-capacitor point-of-load converter, together with its steady-state and small-signal analyses. The output voltage is regulated through a combined frequency/phase shift on-chip controller that operates, thanks to a zero-crossing detector for the tank current. By using such a control technique, voltage regulation can be achieved for a wide range of conversion ratios. Different operation modes are adopted to maximize the efficiency at every load condition. A prototype based on an ASIC developed in a 130-nm CMOS technology has been designed, which achieves the 2.5 to 0.8-1.35 V conversion and supplies up to 3 A. The external resonant tank is composed of a 12 nH air-core inductor and a 4.7 μF capacitor in a 0805 package, achieving high power density. The converter efficiency is demonstrated to be similar to that of an integrated buck converter designed for the same application, whereas the inductor size is reduced by a factor of eight.

A Nonisolated Buck–Boost DC–DC Converter With Continuous Input Current for Photovoltaic Applications

In this article, a novel nonisolated buck–boost dc–dc converter is introduced with a wide range of conversion ratios. The proposed buck–boost converter, unlike the traditional one, draws continuous current from its input port. Moreover, the proposed converter has high step-up voltage gain, which makes it suitable for industrial and renewable energy applications. Operation principles and small-signal modeling of the proposed converter are addressed in detail. Furthermore, the proposed converter is compared with other buck–boost topologies regarding different criteria, such as the number of elements, voltage gain, switch stress, and the type of input current (continuous or discontinuous). By considering the features of the proposed converter, it can be used in renewable applications, specifically in photovoltaic systems. A prototype is developed to experimentally evaluate the validation of theoretical analysis.

Syngas production performance and degradation analysis of a solid oxide electrolyzer stack

A short stack of the Jülich F10 design with anode-supported cells (ASCs; in fuel cell mode), based on the Jülich design with a lanthanum strontium cobalt ferrite (LSCF) air electrode, was employed for a medium-term co-electrolysis operation in technically-relevant conditions at 800 °C. The feed and product gases for an identically-constructed stack under the same conditions were monitored by a process-grade gas analysis system analyzing all relevant gases, including water per direct measurement. The product gas composition conforms to the expectation based on electrolysis and the reverse water-gas shift (RWGS) reaction for a wide range of conversion ratios. The formation of methane as a by-product is discussed. The degradation for stationary phases of the experiment amounted to ∼2% kh−1 (voltage degradation) and 4% kh−1 (based on area specific resistance (ASR)), respectively. Based on the evaluation of electrochemical impedance spectra and post-mortem analyses, the degradation is induced by the depletion of nickel near the electrolyte interface which must be urgently resolved. A hypothesis for an electrochemical mechanism is postulated that complements existing theories. The mass transport contributes the most to the total impedance and the porosity in our cathodes should be optimized for electrolysis mode.

A Family of Switched-Resonant Converters With Wide Conversion Ratio and Controlled Sourcing Features for Volume-Sensitive Applications

In this paper, a family of switched-resonant converters with high efficiency over a wide conversion ratio range is introduced. Inspired by the gyrator resonant switched-capacitor concept, the new topology provides high efficiency over wide and continuous range of conversion ratios using a single resonator. This is enabled by new modes of operation (switching sequences) developed and analyzed in this paper that modify the charge balance of the flying capacitor. By that, the sourcing as well as the efficiency characteristics of the converter can be shaped to peak at various conversion ratios. A generalized methodology is presented to describe resonant converters with multiple operation modes as a two port which is then used to analyze several operational modes of the presented topology. Experimental results validate the developed theoretical model and demonstrate the superiority of the concept in terms of efficiency (over 10%) and current-sourcing capabilities (over 80%) using a compact 5-W prototype.

Multiple Conversion Ratio Resonant Switched-Capacitor Converter With Active Zero Current Detection

This paper introduces an active method for zero current switching for resonant switched capacitor converters (SCC) with wide dynamic range. The method is demonstrated on a binary SCC that features wide range of conversion ratios. Due to the resultant high efficiency of the converter operating under soft-switching conditions, it is applicable for higher power levels up to the medium power range (100 W). The resonant operation is achieved with a single air core inductor and precise commutation at zero current. The sensing signals of the resonant currents are obtained from the flying capacitors rather than form element in which the current includes a dc component. The zero detection method developed is capable of compensating for both the processing delays (from detection to switching action) and for the large variations of the resonant characteristics (due to transition between subcircuits), and for any other component variations. A 100 W prototype with maximum input voltage of 100 V and up to 19 conversion ratios has been built and tested experimentally. The current sensing has been implemented with a simple, cost-efficient, passive sensor. For proper construction of a higher power experimental prototype with desired target efficiency, a set of design considerations for the selection of the power stage components, based on an expanded equivalent resistance concept for multiple subcircuits converter, has been delineated. In addition, a simple and efficient isolated gate driver circuitry is presented.

Buck or Boost Tracking Power Converter

A cascade of buck and boost converter is presented here. The control operates in a manner that the converter is either in buck or boost (BOB) mode on a cycle by cycle basis. It transitions between the modes seamlessly to provide a tracking power conversion function for modulating the power supply of a variable envelope radio frequency (RF) power amplifier. The control algorithm and its implementation using switched capacitor circuits is described. Simulation and measured experimental results including converter efficiency, tracking accuracy, and spectrum at the output of the RF power amplifier are provided. This control technique allows seamless transition between the buck and boost modes while tracking RF envelopes with bandwidth greater than 100 kHz, and maintaining extreme accuracy and extremely low ripple. The efficiency of this converter operating at 1.68 MHz is close to 90% over a wide range of conversion ratios. The area of the power converter is extremely small allowing this to be integrated into a cellular telephone. The controller was integrated as part of a larger power management IC as well as a discrete IC.