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This paper proposes a new load impedance specification for multistage dc power conversion systems. The proposed specification avoids drawbacks of the existing specifications, such as the lack of explicit connections to the dc-link dynamics and the unnecessary conservativeness. The new specification offers a direct command/supervision of the frequency- and time-domain dynamics of the intermediate dc link, while being less conservative than the existing specifications. This paper also presents procedures for redesigning ill-conditioned load impedances to comply with the specification. The validity and utility of the proposed specification are demonstrated using an experimental two-stage dc power conversion system.

This paper investigates the impacts of the load subsystem on stability and performance of the upstream converter in multistage Dc-to-Dc power conversion systems. This paper demonstrates that an appropriate load subsystem can be constructed to provide both stability and intended performance for the upstream converter at the brink of instability before being coupled with the load subsystem. These stabilizing effects of the load subsystem are theoretically analyzed and experimentally validated using a two-stage power conversion system, consisting of an upstream boost converter, downstream buck converter, and two filter stages. This paper also presents the design procedures for the stabilizing load subsystem, along with the performance verification of the upstream boost converter and the downstream buck converter.

In this paper, an isolated double step-down dc–dc converter with high efficiency and high step-down function is proposed. The proposed converter employs an additional capacitor in the primary side. Compared to the conventional full-bridge converters, the proposed converter has a double step-down feature with reduced voltage stress at the primary side of the transformer. Moreover, voltage stress of three primary-side switches reduces to half of the input voltage and zero voltage switching (ZVS) is naturally achieved for all switches with lower output capacitor energy of the switches. Therefore, the proposed converter requires smaller leakage inductance than the conventional full-bridge converter. Without adding complexity to the hardware and control, the proposed converter inherently prevents transformer saturation problem caused by the dc component of the transformer. A 3-kW experimental prototype is constructed to verify the performance of the proposed converter.

Three different current-mode control schemes, peak current-mode control, charge control, and average current-mode control, are investigated for application to asymmetrically driven bridge-type pulsewidth modulated dc-to-dc converters. The principles, implementation, and performance of the three control schemes are compared in an attempt to identify their respective merits and limitations. Design considerations for feedback compensations are also given for the three control schemes. The theoretical predictions of this paper are supported by both experimental results and computer simulations.

This paper presents the theoretical and practical details involved with the small-signal analysis of switching power converters under a strong influence of input filter interaction. A boost dc-to-dc converter controlled by voltage-mode control and the same boost converter controlled by current-mode control are used as illustrative examples. The theoretical predictions of this paper are supported by experimental results and computer simulations

This paper presents the small-signal modeling, dynamic analysis, and control design of the asymmetrical half-bridge dc-dc converter that employs a clamp capacitor and a magnetizing inductor to accommodate pulsewidth-modulated operation with asymmetrical duty ratios. The circuit averaging technique is applied to extract the small-signal dynamics of the power stage, and a graphical loop-gain method is used to design the feedback compensation and analyze the closed-loop performance of the converter. The distinctive power-stage dynamics of the converter are addressed and design guidelines for voltage feedback compensation are established. The results of the control design and closed-loop analysis are substantiated by experiments using an experimental converter.

This paper paper presents the practical details involved in the design and implementation of a contactless battery charger that employs a pair of neighboring printed circuit board (PCB) windings as a contactless energy transfer device. A prototype contactless battery charger developed for application with cellular phones is used as an example to address the design considerations for the PCB windings and energy transfer circuit, plus demonstrates the performance of the contactless charger adapted to a practical application system.

Blind beamforming based on the maximum signal-to-noise ratio (MSNR) can improve the performance of an array system only when the processing gain of the given code-division multiple-access (CDMA) system is high enough such that the desired signal can become dominant after despreading (see Choi, S. and Shim, D., IEEE Trans. Veh. Technol., vol.49, p.1793-1806, 2000; Choi, S. and Yun, D., IEEE Trans. Antennas Propagat., vol.45, p.1393-1404, 1997). We consider a maximum signal-to-interference-plus-noise ratio (MSINR) beamforming. The MSINR performance criterion is chosen to deal with strong interferers effectively. It is shown that blind MSINR beamforming is possible by directly utilizing the input and output signals of correlators of the CDMA systems. In addition, we propose an adaptive beamforming algorithm at a lower computational complexity - about O(7.5N) - where N is the number of antenna elements of the array system. Simulation results are presented in various signal environments to show the performance of the proposed adaptive algorithm.

This paper presents a method for designing the control loop for DC-to-DC power converters when uncertainties exist in the AC characteristics of the converter's load. In the proposed method, a converter is initially considered as a stand-alone module feeding a current sink load and the control loop of the converter is then designed in a way that maximizes the robustness of the converter's closed-loop performance against the unknown AC dynamics of a potential load. As a result, the proposed control design method can provide the predictable closed-loop performance for a converter when it is loaded with an actual load whose AC characteristics are unknown in advance.

This paper presents the theoretical and practical details involved in the control design and closed-loop analysis of a step-down switched-capacitor DC-to-DC power converter. The state-space averaging technique is applied to extract the small-signal dynamics of the power stage, and a graphical loop gain method is used to design the feedback compensation and analyze the closed-loop performance of a switched-capacitor converter. The results of the control design and closed-loop analysis are substantiated by experiments on a prototype switched-capacitor converter.

A large-signal average model for the controlled on-time boost power-factor-correction (PFC) circuit is developed and subsequently linearized, resulting in a small-signal model for the PFC circuit. AC analyses are performed using the small-signal model, revealing new results on the small-signal dynamics of the PFC circuit. The analysis results and model predictions are confirmed with experimental measurements on a 200-W prototype PFC circuit.

Three different paralleling schemes for multimodule converters are investigated. For each paralleling scheme, benefits and limitations are addressed for distributed power applications, and guidelines for designing the feedback controller are presented. Results of the analysis are verified by both frequency and time-domain simulations.

This paper analyzes the step load response of a current-mode-controlled pulsewidth modulation (PWM) converter and also presents design guidelines for obtaining a good step load response. Analytical expressions for the step load response are derived in terms of the power stage and feedback compensation parameters. Control design to minimize the overshoot and settling time of the output voltage is presented. Analysis results are verified by large-signal simulations.

This paper presents simple, noniterative, and practical design procedures for intermediate line filters intended for distributed power applications. The design procedures realize a line filter which simultaneously meets both impedance compatibility requirements and EMI specifications. Design examples are given for both single-stage and two-stage filters. >

A three-loop control scheme for multimodule power converter systems with a secondary LC filter is presented. In addition to output voltage and inductor current feedback, the control scheme employs feedback from the output capacitor of each module to improve the dynamic performance of the system, particularly the transient response in the event of failure of a module. The superiority of the three-loop control over the conventional two-loop current mode control is demonstrated by both small-signal analysis and large-signal simulations. >