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Fuel cell electric vehicles (FCEVs) have batteries to mitigate problems such as the inability to store energy, poor response speed, and low power density. In the conventional power conversion system, the fuel cell (FC) and battery can be connected to the output load via two independent converters, namely a unidirectional converter for powering with the FC and a bidirectional converter for powering and regenerating via the battery. The conventional converter has a simple structure; it achieves specific operating modes that are required in various driving situations. However, it has two inductors and many operating switches when the FC and battery are simultaneously used. In addition, all the switches have high voltage stresses. These factors can degrade the overall power density and efficiency. Thus, an integrated converter with single inductor is proposed in this paper. By employing a battery mode selection cell (BMSC), the two converters can be integrated with only one inductor. Moreover, the number of operating switches is reduced during powering, and low voltage-rated semiconductor devices can be used. Therefore, the proposed converter can achieve high power density and low conduction and core losses. The validity of the proposed converter was demonstrated by the experiments under various operating conditions.

Among the various dc grid system concepts connected to battery and load, the parallel-connected structure is widely adopted due to its simplicity. However, it has two inductors, which operate simultaneously when using a battery, so the power density and efficiency can be degraded. To alleviate these problems, in this article, we propose a new single inductor converter. By integrating the two converters and using the battery switching cell, the proposed converter can reduce the number of inductors required and employ lower voltage-rated switches. Therefore, the proposed converter can achieve high power density and efficiency. A 500-W prototype converter is implemented, and each mode is examined under various operating conditions to confirm the validity.

It has been proposed that the main battery voltage of electric vehicles should be increased to increase the driving distance and decrease the charging time. Thus, a low-voltage dc/dc converter (LDC) with high and wide input voltage range is required for electronic loads. This article proposes a two-mode LDC and the entire input range is divided into two low and high input voltage ranges. The converter has two operating modes corresponding to these input voltage ranges. In the low input voltage range, it operates as a three-switch double-ended active clamp forward converter. In the high input voltage range, it operates as an asymmetric half-bridge converter. Changing the operating mode according to the input voltage, the proposed converter can have low-voltage stresses on the switches and a low dc offset current of the transformer resulting in high efficiency for the entire input voltage range. In order to confirm the validity of the proposed converter, a 600 W prototype is implemented and experimented.

This article proposes a half-bridge LLC resonant converter applying a simple circuit with a variable magnetizing inductance scheme for hold-up time requirement. By changing the magnetizing inductance of the main transformer, the proposed converter can satisfy the hold-up time requirement without sacrificing efficiency, featuring small conduction, and turn- off switching losses of the primary switches in the nominal status. In addition, the proposed converter can relieve the burden of the additional components by positioning them on the signal path, and the proposed circuit is self-powered by adding only one additional winding instead of the isolated power supply. Therefore, those of the size and cost of the proposed circuit can be reduced compared to the previous studies. The feasibility of the proposed method was verified with a 350 W prototype converter (56 V/6.25 A), and the improved circuit for the transient mode was also presented. The experimental results validated the theoretical analysis and showed the effectiveness of the proposed converter for high-efficiency applications, especially in light-load conditions.

The double-ended (DE) active-clamp forward (ACF) converter is one of the attractive dc–dc converters for the power supply of digital devices due to a simple structure and zero voltage switching (ZVS) capability of primary switches. However, due to a dc offset current of transformer, the size and core loss of transformer are increased. In this paper, a new DE-ACF converter having an additional switch and a diode is proposed to achieve a low dc offset current of transformer by charging a clamp capacitor additionally during a turn- off interval between main switches. Thus, the transformer size can be reduced in the proposed converter. Furthermore, since the output inductor current ripple is reduced, the primary and secondary conduction losses can be decreased under medium and heavy loads. As a result, the proposed converter can have higher efficiency than conventional DE-ACF converter. The validity of the proposed converter is confirmed by experimental results from a prototype with 400 V nominal input voltage and 400 W (12 V/33.33 A) output.

Two-dimensional (2D) Janus transition metal dichalcogenides (TMDCs) are highly attractive as an emerging class of 2D materials, but only a few methods are available for fabricating them. These methods rely on the initial growth of 2D TMDCs in one process, followed by an additional plasma or high-temperature (T) process. To overcome these drawbacks, we employ the new approach of NaCl-assisted single-process chemical vapor deposition, which consists of three steps that proceed only by altering the temperature in situ. In the first step, MoS2 is deposited onto a SiO2/Si substrate with the Mo and S atoms activated in different temperature zones. In the second step, S vacancies are formed in the upper layer of the grown MoS2 by annealing. In the third step, the vacancies are filled with activated Se atoms. Throughout the steps, NaCl lowers the melting point of the constituent atoms, while the T in each zone is properly controlled. The growth mechanism is clarified by a separate annealing experiment that does not involve a supply of activated atoms. These results highlight a simple and cost-effective approach for growing Janus MoSSe, which is more useful for fundamental studies and device applications.

This paper presents a new interleaved active clamp forward converter for low and wide input, and high current output applications. In the proposed converter, the operating duty ratio can be extended over 0.5 due to the additional powering path resulting from additional series-connected secondary windings from each transformer. As a result, the proposed converter can be designed with large transformer turns ratio. Thus, since the proposed converter can reduce not only the primary RMS current but also switch turn- off current, it can achieve high efficiency. Moreover, since all secondary switches can operate without floating gate drivers, the proposed converter can maintain simple structure and low complexity of gate driving circuits in the secondary side. The validity of this proposed converter is verified by the experimental results from 36V–72 V input and 12 V/500 W output for the dc/dc prototype.

In this paper, a half-bridge (HB) converter, additionally employing a diode compared with the conventional modified duty-cycle-shifted (MDCS) HB converter, is proposed to achieve a high efficiency in wide-input-voltage and low-output-current applications. Since the proposed converter has symmetrical operation, it maintains the advantages such as no transformer dc-offset current, and identical and low-voltage stresses on the secondary diodes. Moreover, due to one additional switch connected in series, the zero-voltage-switching capability of the upper switch is improved. As a result, small resonant inductances are required, which reduces the duty cycle loss, thus the primary conduction losses decrease. In addition, since additional clamping diodes separate external resonant inductor from the resonance path, additional voltage stresses on the secondary diodes can be decreased. Therefore, its snubber loss can be reduced, and it can achieve higher efficiency than that of the MDCS HB converter. To confirm the operation, features, and validity of the proposed converter, a 310–400 V input and 50-V/250-W output laboratory prototype is built and tested.

A bridgeless dual boost rectifier is proposed to achieve a soft switching for power factor correction circuit. Based on the conventional bridgeless dual boost rectifier, an auxiliary circuit is employed in the proposed converter to perform zero-voltage switching of the main switches and zero-current switching of the auxiliary switches. As a result, switching losses can be significantly reduced. In addition, the design guideline for the optimized turn-on time of the auxiliary switches is presented to minimize the additional conduction loss in the auxiliary circuit. The validity of the proposed converter is confirmed by the experimental results of a prototype converter with 100–240 $V_{{\text{AC}}}$ universal-line input and 800-W (400 V/2 A) output.

A new asymmetric half-bridge (HB) resonant converter for dc/dc power system with a wide range of low input voltage is proposed in this paper. The proposed converter is easily derived based on the switch integration technique, merging a buck–boost, which is the same with the active-clamp forward's primary circuit, and the HB LLC resonant converter. By adopting the buck–boost circuit in front of the HB LLC resonant converter, higher input voltage of LLC resonant converter stage can be achieved. As a result, the primary conduction loss can be significantly reduced. In addition, to cover wide input voltage range, an asymmetric pulse width modulation control is applied. It can mitigate the design limitation for a high efficiency. Moreover, the proposed converter can achieve not only the small conduction loss and the optimal design for high efficiency, but also high power density and low cost due to the switch integration technique. The validity of the proposed converter is confirmed by the experimental results of a prototype converter with 36–72 V DC input and 300 W (12 V/25 A) output.

The half-bridge (HB) LLC converter is one of the most attractive dc–dc converters for medium power supplies due to its soft switching capability. However, its conversion efficiency is considerably degraded in wide-link-voltage applications because of a small magnetizing inductance and wide switching frequency variation for a high voltage gain. In this paper, a boost power factor correction (PFC) stage, which can also play an important role during the hold-up time, is proposed for a high-efficiency HB LLC converter. In the proposed PFC stage, the boost PFC converter can be effectively utilized as a HB converter by replacing a boost diode and inductor with a synchronous switch and transformer, respectively. After the ac line is lost, the proposed PFC stage can operate as the HB converter and regulate the output voltage instead of the HB LLC converter. Thus, it enables the HB LLC converter to be designed with a large magnetizing inductance and narrow switching frequency variation. As a result, the proposed PFC stage can enhance the overall efficiency of the PSU by improving the efficiency of the HB LLC converter. To confirm the validity of this paper, a prototype with 180–264-Vrms ac line, 250–400-V link voltage, and 48 V/480 W output is tested.

This paper presents a new buck–boost converter. Unlike the single-switch buck–boost converter, the proposed converter has low-voltage stresses on semiconductors. Moreover, although both the conventional two-switch buck–boost (TSBB) and the proposed converters have the same number of passive and active components, and the proposed converter can reduce the conduction loss as a result of having fewer conducting components. Therefore, the proposed converter obtained a higher efficiency than the TSBB converter. A 48-V output voltage and 150-W output power prototype was fabricated to verify the effectiveness of the proposed converter.

In the standby stage of a server power supply, the flyback converter has been widely used due to its simple structure and low cost. However, since the flyback converter suffers from high-voltage stress and a large transformer, it degrades the efficiency and power density of the server power supply. To relieve these drawbacks, this paper proposes a new standby structure where a flyback converter is integrated with a boost power-factor-correction (PFC) converter. The proposed standby structure can relieve the high-voltage stress and eliminate the large transformer of the conventional flyback converter because the primary side of the flyback converter is merged with the boost PFC converter. Thus, the proposed structure can achieve high efficiency and high power density in the standby stage. Furthermore, it can help the boost PFC converter achieve a soft switching operation, which results in a high-efficiency PFC stage. As a result, the proposed structure improves the overall efficiency and power density of the server power supply. The validity of the proposed structure is confirmed by a prototype with 100–240 Vrms ac input, 750-W PFC output, and 12-V/2-A standby output.

The conventional half-bridge converter for a dc/dc stage in wide-output-voltage and constant-output-current applications such as LED drivers is limited in achieving high efficiency because it is difficult to be designed optimally. To overcome this limitation, an integrated asymmetrical half-bridge zeta converter is proposed for high efficiency in the overall output voltage range. The proposed converter can be simply implemented by replacing a snubber diode with a switch. The proposed converter operates similar to the asymmetrical half-bridge converter by turning off the switch in the low-output-voltage region, which enables it to have a small dc-offset current in the transformer. In the high-output-voltage region, the proposed converter operates similar to the half-bridge zeta converter by turning on the switch, which has small transformer core loss. Therefore, the proposed converter can achieve high efficiency over the entire output voltage range compared with the conventional converters. The validity of the proposed converter is confirmed by experimental results from a prototype with 400-V input and 90–180-W/3-A output.

In this paper, an asymmetrical half-bridge (AHB) converter employing a new center-tapped zeta rectifier (CTZR) is proposed to achieve a high efficiency in wide-input-voltage and low-output-current applications. Due to the proposed CTZR with high dc conversion ratio and extended maximum duty cycle above 0.5, the transformer turns ratio of the proposed converter can be increased, which decreases the transformer dc-offset current compared with that of the AHB converter. Therefore, its transformer core size is decreased. Moreover, it has a wide zero-voltage-switching range with small transformer leakage inductor, which improves light and medium load efficiency. Furthermore, since it has low voltage stress on the secondary diode, its conduction loss can be reduced. In addition, due to the elimination of a diode, the snubber loss in the secondary side is reduced compared with the AHB converter. Therefore, the proposed converter can achieve a higher efficiency compared with the AHB converter without additional devices. To confirm the operation, features, and validity of the proposed converter, a 250–400 V input and 50 V/250 W output laboratory prototype is built and tested.

Recently, the various types of the half-bridge (HB) converters with the output inductor have been developed, and they exhibit a good performance in medium power applications such as the server power supplies and personal computer power supplies requiring high output current. However, they have common problems such as the primary and secondary switch turn-off losses and snubber loss in the secondary side caused by the output inductor, which degrades light load efficiency. To relieve these limitations of the conventional HB converters, a new HB converter, which employs one additional switch and capacitor in the secondary side, is proposed for a high efficiency under light load conditions in this paper. Since the proposed converter operates like the HB LLC converter with below operation by turning on additional switch under light load conditions, the switch turn-off losses and snubber loss can be minimized, and the zero-voltage switching (ZVS) capability can be improved. Consequently, the proposed converter can achieve a high efficiency under light load conditions. To confirm the operation, features, and validity of the proposed converter, a 330–400 V input and 12 V/300 W output laboratory prototype is built and tested.

This paper presents nonisolated single-switch high step-up converters with low voltage stress. Based on the conventional flyback converter, one single-switch high step-up converter is derived. The voltage stresses on the switch and diodes are limited by using a clamping diode and voltage doubler structure. Also, to further reduce the voltage stresses of them, another single-switch high step-up converter is proposed simply by using one additional capacitor and rearranging the components. Thus, lower voltage-rated switch and diodes can be used, which results in higher efficiency. The operational principle, analysis and design considerations of each converter are presented in this paper. The validity of this study is confirmed by the experimental results from 24 V input and 250 V/125 W output prototype.

A zero-voltage-switching (ZVS) bridgeless power factor correction (PFC) boost converter to reduce switching losses is proposed in this paper. Based on the conventional dual boost bridgeless converter, an auxiliary circuit including another main switch on the opposite side is added in the proposed converter to perform ZVS in man switches. Moreover, ZCS of auxiliary switches can also be achieved. As a result, the switching loss can be significantly reduced in the proposed converter. In addition, to minimize the additional conduction loss in the auxiliary circuit, the optimized design method for turn-on time of auxiliary switches is presented. The validity of the proposed converter is confirmed by the experimental results of a prototype converter with 100–240 V AC universal-line input and 800 W (400 V/2 A) output.

This paper presents a new non-isolated dual-input dc-dc converter. The proposed converter can transfer energy from different input sources to the output load individually and simultaneously. In addition, by operating in the step-up/down mode, the input voltages can be higher or lower than the output voltage which leads to a wide input voltage range. This feature is suitable for renewable energy systems that have wide voltage variations. The validity of the proposed converter is confirmed by experimental results from a prototype with 36–72V/24–60V inputs and a 48V/200W output.

This paper proposes an automatic link voltage controller (ALVC) in low power and universal input applications. The ALVC is composed of an auxiliary capacitor and switch, and control circuits. The auxiliary capacitor voltage increases the link voltage in low line. Thus, the link voltage variation can be reduced, which makes higher efficiency of overall circuit. The validity of this proposed circuit is confirmed by the experimental results from 18 V/40 W prototype in universal line.

This paper presents a new multioutput converter. It consists of a half-bridge inverter in primary side and a flyback rectifier that is integrated with an auxiliary buck converter in secondary side. The primary switches control the main output voltage and the secondary synchronous switches control the auxiliary output voltage. The main advantages of the proposed converter are that the transformer size can be reduced due to the lower magnetizing offset current, all the switches including synchronous ones can achieve the zero-voltage switching, and it has no cross regulation problems. The operational principle, analysis, and design considerations of the proposed converter are presented in this paper. The validity of this study is confirmed by the experimental results from dual-output (24 V/8 A and 12 V/4 A) prototype.

This paper presents a new standby structure where a forward converter is integrated with a dc-dc phase-shift full-bridge (PSFB) converter for server power supplies. While a typical standby structure consists of an independent flyback converter, the proposed standby structure is integrated with one leg of the dc-dc PSFB converter. Its main advantages are that the voltage across a standby switch is clamped at the link voltage across the link capacitor and that the standby switch achieves zero-voltage switching over entire load range. The validity of the proposed standby structure is confirmed by the experimental results from 12 V/58 A for the dc-dc output prototype and 11.5 V/1.5 A for the standby output prototype.

This paper presents a new interleaved active clamp forward converter for wide input and high current output applications. The operating duty ratio can be extended over 0.5 by using additional series-connected secondary windings from each transformer. All secondary switches are operated without floating gate driver, which results in low circuit complexity and high power density. The validity of this proposed converter is confirmed by the experimental results from 36V–72V input and 12V/500W output for DC/DC prototype.

The conventional two-stage structured power-supply units (PSUs) requiring the hold-up time operation have generally low efficiency dc/dc stage because it is difficult to be designed optimally. As a result, to improve the efficiency of the dc/dc stage, many hold-up time compensation methods have been presented. However, they cannot still optimize the dc/dc stage due to its bad influence on the design conditions. In addition, they can only be employed in certain dc/dc topologies as well as they still ill-affect the design conditions of the dc/dc stage. Therefore, in this paper, a new hold-up time compensation method is proposed to overcome the conventional limitation. Compared to the conventional method, since the proposed method delivers the output power by using not the dc/dc stage but the power factor correction (PFC) stage during the hold-up time, it can optimize the dc/dc stage at the nominal state without any bad influence, which enables the dc/dc stage achieve a high efficiency. Furthermore, it can be widely applied to various dc/dc stages. The validity of the proposed method is confirmed by experimental results from a prototype with 90–264Vrms input and 480W/10A output.

This paper presents a new standby structure where the standby flyback converter is integrated with the zero-voltage-switching multi-output full-bridge dc-dc converter. While the standby power is generated from the conventional flyback converter in standby mode, the auxiliary output of the multi-output full-bridge converter is used for the standby output in normal mode. The validity of this proposed structure is confirmed by the experimental results from 12 V/58 A for the dc-dc output and 5 V/3.2 A for the standby output prototype.