Taeyoung Ahn

Design and implementation of low-profile contactless battery charger using planar printed circuit board windings as energy transfer device

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.

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.

Multi-phase interleaved LLC-SRC and its digital control scheme

This paper proposes a new 3-phase interleaved LLC resonant DC-DC converter and its control scheme. The proposed circuit consists of three conventional interleaved LLC resonant DC-DC converters and each converter operates with π/3 of phase difference respectively. Therefore the current ripple of the output capacitor can be significantly reduced and the life cycle of the converter will be extended. To verify the validity of the proposed converter and digital scheme, an experiment with a prototype 1kW (12V/84A) DC-DC converter was implemented and its results are presented in this paper.

Average Current Mode Control for LLC Series Resonant DC-to-DC Converters

An average current mode control scheme that consistently offers good dynamic performance for LLC series resonant DC-to-DC converters irrespective of the changes in the operational conditions is presented in this paper. The proposed control scheme employs current feedback from the resonant tank circuit through an integrator-type compensation amplifier to improve the dynamic performance and enhance the noise immunity and reliability of the feedback controller. Design guidelines are provided for both current feedback and voltage feedback compensation. The performance of the new control scheme is demonstrated through an experimental 150 W converter operating with 340 V to 390 V input voltage to provide a 24 V output voltage.

New half-bridge dc-to-dc converters for wide input voltage applications

This paper presents new soft-switched half-bridge dc-to-dc converters intended for applications where the input voltage varies widely. The proposed converters are presented in both non-isolated form and isolated form. The proposed dc-to-dc converters operate with zero voltage switching characteristics for MOSFET switches. The duty ratio of the proposed converter could expand to 100 % and its voltage gain is twice the voltage gain of conventional half-bridge converters. Accordingly, the proposed converters are well suited for applications requiring high conversion efficiency at the presence of wide input voltage variations. The operation and performance of the proposed converters are demonstrated with experimental converters that deliver a 12V/5A output from a 35–60 V input. The non-isolated converter recorded the maximum efficiency of 91 % at 1.5 A load current.

Reliability improvement of FB inverter in HID lamp ballast using UniFET™ II MOSFET family

This paper introduces a newly developed UniFETTM II MOSFET family of which the body diode characteristic has been highly improved and presents its effectiveness for the mixed frequency switching inverter leg in the HID lamp ballast. Its reverse recovery time, Trr of the body diode is 35 nsec and the peak value of reverse current, irr is also much smaller than that of the typical MOSFET and even smaller than FRDs. Therefore, it can ensure the better reliability in the switching inverter applications in which the performance of the MOSFET body diode is significant. In order to verify the validity, an experiment with an 150W HID lamp ballast was implemented and its results and effectiveness are presented in this paper.

A study on low-profile DC-DC converter module by applying electromagnetic induction type wireless power transmission and bluetooth feedback controller

We proposed slim type DC to DC converter modules based on wireless power transmission technology, and 500W class prototype was produced with applying the technology on Switching power supply converter designing. The wireless power transmission technology is actively studied in these days to increase isolated voltage of transformer. The power transmitting transformer was fixed on ceramic centered multi-layer PCB to increase efficiency and to lower height of the prototype. Also, winding wire of the transformer was designed with PCB patterns to minimize the height. And wireless power transmission technology is important for the output compensation circuit, so we applied for Bluetooth technology. The Specification of the prototype was 400V of input voltage; 1 Mhz of switching frequency; output voltage control through Bluetooth system. Even though wireless power transmission structured transformer was used, the power transmission efficiency was relatively high.

A study on novel active clamp snubber applied DC-DC quasi resonant flyback converter to effectively reduce switch voltage surge

In this paper, active clamp snubber method was proposed to reduce effectively the switching surge voltage of the conventional quasi resonant (QR) flyback converter. The usefulness and practicality of the proposed method in QR flyback converter were verified through steady-state analysis and its experimental results. The performance of the proposed circuit was compared with the RCD snubber method. It was verified from the experimental results that the switch peak voltage of the proposed method was limited below 5% while the switch peak voltage of the RCD snubber was continuously increasing accordingly with the load current. Furthermore, this new active clamp snubber method could be applied to QR flyback and its power conversion efficiency was superior to the RCD snubber one.

A Study on the Efficiency Characteristics of the Interleaved CRM PFC using GaN FET

This paper presents the efficiency analysis of a critical current mode interleaved PFC rectifier, in which each of three different semiconductor switches is employed as the active switch. The Si FET, SiC FET, and GaN FET are consecutively used with the prototype PFC rectifier, and the efficiency of the PFC rectifier with each different semiconductor switch is analyzed. An equivalent circuit model of the PFC rectifier, which incorporates all the internal losses of the PFC rectifier, is developed. The rms values of the current waveforms main circuit components are calculated. By adapting the rms current waveforms to the equivalent model, all the losses are broken down and individually analyzed to assess the conduction loss, switching loss, and magnetic loss in the PFC rectifier. This study revealed that the GaN FET offers the highest overall efficiency with the least loss among the three switching devices. The GaN FET yields 96% efficiency at 90 V input and 97.6% efficiency at 240 V, under full load condition. This paper also confirmed that the efficiency of the three switching devices largely depends on the turn-on resistance and parasitic capacitance of the respective switching devices.

Power device consideration on high power PFC pre-regulator for optimized design

A latest super-junction MOSFET is applied to hard switching, high power PFC application and compared to soft switched IGBT. With reduced on-resistance and enhanced switching characteristics, the super-junction MOSFET can compete with soft switched IGBT. A 1.5kW rated CCM PFC circuit is designed and ZVS logic has implemented for performance evaluation of both configurations. Limit line of power rating is discussed through analyzing switching and conduction losses.