This paper presents a reconfigurable voltage multiplying rectifier (RVMR) to improve the performance of LLC resonant converter for wide output voltage applications. The RVMR can operate as voltage doubler mode or voltage quadrupler mode according to the primary switching strategy. Two operation modes split an wide output voltage range into two narrow ranges. Therefore, the RVMR enables the LLC resonant tank to be designed in narrow output voltage range, which results in narrow switching frequency range, high efficiency, and high power density. Smooth mode transition can be achieved by additionally adopting a phase-shift control to general pulse-frequencymodulation (PFM) control without any additional switch. The proposed RVMR LLC converter can improve its efficiency by 2.9% and reduce component volume by 26% compared to the conventional FB LLC resonant converter. A 750 W prototype with 400 V input, 100-300 V output voltage, and 2.5 A max output current has been built and tested to verify the effectiveness of the proposed converter.

This paper presents a reconfigurable totem-pole bridgeless power factor correction (PFC) converter employing an auxiliary circuit and simple control scheme to achieve high efficiency. Under light load condition, instead of delivering the energy through the main switch, the proposed converter utilizes the auxiliary switches only by using different control scheme. Since the auxiliary switches have much smaller parasitic capacitances than the main switches, the proposed converter can obtain high efficiency under light load condition. Over middle-to-heavy load condition, the proposed converter can acquire both ZVS operation and relieved reverse recovery problem thanks to the auxiliary circuit, which leads to high efficiency even with Si-MOSFET in the continuous conduction mode (CCM) control. As a result, the proposed converter can achieve high efficiency over the entire load conditions. The effectiveness of the proposed converter is verified by a prototype with ac 230VRMS input and 750W output.

A bi-directional switch bridgeless PFC converter (BBPFC) is a fascinating topology for high power application among various bridgeless PFC converters due to its simple structure and easy control method despite using floating gate driver. In addition, by varying reverse recovery characteristics of rectifying diodes placed on the conduction path, it is possible to improve common-mode (CM) noise characteristics without additional line filter. However, the BBPFC is difficult to actually use in server power supply product because of high guarantee payment. Thus, in this paper, a new bridgeless PFC converter (BPFC) for high efficiency and simple structure without any patent issues is proposed. Moreover, it can be simply implemented since the proposed converter is not by requiring for floating gate driver but by using a simple bootstrap circuit. Furthermore, in the both positive and negative cycles, the proposed converter can have lower power loss characteristic due to utilizing one switch for build-up operation. The proposed converter also makes use of the relative reverse recovery characteristics resulting in good CM noise characteristics. Thus, the proposed converter can obtain high efficiency and good CM noise characteristics with simple structure and easier control method. The effectiveness of the proposed converter is verified by a prototype in universal input and 800W/400V output.

The LLC resonant converter is one of the most attractive topologies in many applications, due to its simple structure and zero-voltage-switching capability. However, under wide-input-voltage condition, it has large primary conduction and turn-off switching losses, because of small magnetizing inductance. Thus, in this paper, the LLC resonant converter using three switches is proposed for high-efficiency under wide universal ac input voltage. These three switches can make two operating modes of LLC resonant converter according to low/high line input conditions. As a result, the proposed converter can be designed with larger magnetizing inductance, resulting in a high efficiency. The validity of the proposed converter is verified with 60W prototype for high-efficiency, almost maintaining the system size, compared with the conventional LLC converter.

LLC resonant converter is very attractive topology for high efficiency and high power density applications, thanks to zero-voltage-switching (ZVS) of primary switches and zero-current-switching (ZCS) of secondary rectifiers as well as low voltage stress of the overall components. Its critical drawback is unintended increase of output voltage beyond the regulation limit at very light load, in spite of much higher switching frequency for low input-to-output voltage gain. To suppress output voltage within the regulation range at very light load, the external capacitor attached across drain-source of primary switches is investigated and the optimal capacitance is designed in this paper. Its validity is verified experimentally with the implemented 240W prototype for flat panel display application.

The effect of displacement defect on SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) due to radiation is investigated using technology computer-aided design (TCAD) simulation. The position, energy level, and concentration of the displacement defect are considered as variables. The transfer characteristics, breakdown voltage, and energy loss of a double-pulse switching test circuit are analyzed. Compared with the shallow defect energy level, the deepest defect energy level with E_C − 1.55 eV exhibits considerable degradation. The on-current decreases by 54% and on-resistance increases by 293% due to the displacement defect generated at the parasitic junction field-effect transistor (JFET) region next to the P-well. Due to the existence of a defect in the drift region, the breakdown voltage increased up to 21 V. In the double-pulse switching test, the impact of displacement defect on the power loss of SiC MOSFETs is negligible.