Wonseok Lim

Small-signal analysis and control design of asymmetrical half-bridge DC-DC converters

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.

Comparative Performance Evaluation of Current-Mode Control Schemes Adapted to Asymmetrically Driven Bridge-Type Pulsewidth Modulated DC-to-DC Converters

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.

Analysis and design of a forward-flyback converter employing two transformers

This paper presents the steady-state analysis and design of a forward-flyback converter that employs two transformers and an output inductor. By utilizing two separate transformers, the proposed converter allows a low-profile design to be readily implemented while retaining the merits of a conventional single-transformer forward-flyback converter with secondary center tap. By using an output inductor, the proposed converter efficiently reduces the output ripple to an acceptable level. The design and performance of the proposed converter are confirmed with experiments on a 100 W prototype converter.

Low-profile contactless battery charger using planar printed circuit board windings as energy transfer device

This paper presents 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. In this paper, a prototype contactless battery charger developed for the application to cellular phones is used as an example to address design considerations for the PCB windings and energy transfer circuit and demonstrate the performance of the contactless charger adapted to a practical application system.

Control design and closed-loop analysis of a switched-capacitor DC-to-DC converter

The theoretical and practical details involved in the control design and closed-loop analysis of a step-down switched-capacitor (SC) DC-to-DC converter are presented. 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 an SC converter. The results of the control design and closed-loop analysis are substantiated by experiments using a prototype SC converter.

Comparative performance evaluation of current-mode controls adapted to asymmetrically-driven bridge-type pulse-width modulated DC-to-DC converters

Three different current-mode control schemes, peak current-mode control, charge control, and average current-mode control, are investigated for the applications to asymmetrically-driven bridge-type pulse-width 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 examples for feedback compensations are given for the three control schemes. The theoretical predictions of this paper are supported by computer simulations and experimental results

Current-mode control to enhance closed-loop performance of asymmetrical half-bridge dc-to-dc converters

Asymmetrical half-bridge dc-to-dc converters exhibit the fourth-order power stage dynamics. When the conventional voltage-mode control is employed, the fourth-order dynamics impose certain constraints on the feedback compensation design and the result could be poor closed-loop performance. This paper demonstrates that the current-mode control could alleviate the detrimental effects of the power stage dynamics and offer an improvement in the closed-loop performance. The principles, performance, and experimental results of current-mode control are presented in comparison with those of voltage-mode control.

Average and small-signal model for asymmetrically-driven double-ended PWM DC-to-DC converters

This paper presents average and small-signal models for a wide class of asymmetrically-driven double-ended (ADDE) pulsewidth modulated (PWM) dc-to-dc converters. In this paper, average models for the primary- and secondary-side circuits, commonly employed to most ADDE converters, are first derived using the circuit averaging technique. The principle of energy conservation is then invoked to systematically incorporate the effects of multiple parasitic resistances. The resulting average models are appropriately assembled to constitute an average model for a specific ADDE converter. Finally, the average model of an ADDE converter is linearized to yield the respective small-signal model. The validity and accuracy of the proposed models are experimentally verified using two prototype ADDE converters.