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This article presents a reconfigurable voltage multiplying rectifier (RVMR) to improve the performance of an 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 a wide output voltage range into two narrow ranges. Therefore, the RVMR enables the LLC resonant tank to be designed in a narrow output voltage range, which results in a narrow switching frequency range, high efficiency, and high power density. A smooth mode transition can be achieved by adopting a phase-shift control to general pulse frequency modulation 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 full-bridge 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 article presents a reconfigurable totem-pole bridgeless power factor correction converter employing an auxiliary circuit and a simple control scheme to achieve high efficiency. Under light load condition, instead of delivering the energy through the main switch, the proposed converter utilizes only the auxiliary switches by using a 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 zero-voltage switching 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 control. As a result, the proposed converter can achieve high efficiency over the entire load condition. The effectiveness of the proposed converter is verified by a prototype with ac 230 V rms input and 750 W 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 article, 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 high efficiency. The validity of the proposed converter is verified with a 60-W prototype for high efficiency, almost maintaining the system size, compared with the conventional LLC converter.

A bidirectional-switch bridgeless power factor correction (PFC) converter (BBPFC) is a fascinating topology for high-power application among various bridgeless PFC (BPFC) converters due to its simple structure and easy control method despite using a 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 article, a new BPFC for high efficiency and simple structure without any patent issues is proposed. Moreover, it can be simply implemented since the proposed converter does not require floating gate driver but use a simple bootstrap circuit. Furthermore, in both positive and negative cycles, the proposed converter can have lower power loss characteristics due to utilization of one switch for build-up operation. The proposed converter also uses 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 800-W/400-V output.

This article presents a semiresonant half-bridge zeta (HBZ) converter for high-efficiency power supply. Since the proposed converter utilizes a primary inductor and secondary capacitor as a resonant tank, it can make a resonant operation during the on-state of a low-side primary switch. Therefore, the proposed converter can effectively reduce turn-off currents of the low-side primary switch and the secondary diode without any additional component and control scheme, which decreases turn-off switching loss and reverse-recovery loss. Moreover, the proposed converter can maintain advantages of the conventional HBZ converter such as high input/output (I/O) voltage gain and wide zero-voltage-switching (ZVS) range with the proposed design procedure. As a result, the proposed converter can improve its efficiency over the entire load conditions compared to the conventional HBZ converter. A 250 W, 300-400 V input, and 56 V output prototype has been built and tested to verify the effectiveness of the proposed converter.

Phase-shift full-bridge (PSFB) converter is a widely used topology for high-efficiency and high-power applications, thanks to low voltage/current stress of all components and zero-voltage-switching operation of primary mosfet s. The critical drawback of the PSFB converter is hard-switching characteristics of primary mosfet s at a very light load, which causes severe thermal explosion and extremely high input power consumption, especially with the latest super-junction mosfet . To minimize the switching loss of the PSFB converter at a very light load, a new optimal dead-time control scheme with burst-mode operation is proposed in this paper and its validity is verified experimentally with the implemented 2.2-kW server power supply unit.

The improved three switch-active clamp forward (3S-ACF) converter is proposed in this paper. The proposed converter has minimized the switching loss on all switches of the conventional 3S-ACF converter by simply changing the gate control method without any additional components. Moreover, the modified gate control enables peak and average currents on the clamp diode to be reduced. Though, all switches of the proposed converter have low-voltage stress similarly to those of the conventional 3S-ACF converter. Consequently, the proposed converter can achieve a high efficiency without any additional components. To confirm the operation, features, and validity of the proposed converter, a 180–288 V dc input and 12 V/550 W output laboratory prototype is built and tested.

This paper proposes a new control strategy applicable to active clamp forward converter (ACFC) under light load conditions. Conventional ACFC is difficult to achieve high efficiency under light load conditions due to conduction losses caused by the excessive freewheeling current. The proposed control strategy can significantly improve the light-load efficiency while reducing conduction losses without the need for additional circuitry. The feasibility and performance of the proposed control strategy are experimentally verified with a USB PD adapter prototype designed for a universal AC input and 65W maximum output.

In the receiver-side of wireless power transfer (WPT) system, the two power stages such as rectifier and battery control converter have been widely used due to its easy implementation. However, since the two power stages cause many number of components on the conduction path, it degrades the efficiency and power density of WPT system. Also, in the WPT system, because the communication control between transmitter and receiver side have to be used due to its physical contactless structure, the transmitter-side cannot effectively control receiver-side rectifier outputs. To relieve these drawbacks, this paper proposes a new receiver-side integrated regulator. The proposed structure is based on the general full-wave rectifier diode structure, and a single-switch is integrated for output voltage regulation with phase-shift control strategy. The proposed structure can reduce the number of components on the conduction path, resulting in high power density. Moreover, the proposed method can remove communication control with stable receiver-side outputs. Theoretical analysis and simulation results verify that the proposed structure and control method enables stable output voltage regulation without communication control between transmitter and receiver side. The effectiveness of the proposed structure and control method is verified by a prototype with input 380V DC and 150W output.

The phase-shifted full-bridge (PSFB) converter with synchronous rectifier (SR) is one of the most attractive dc–dc converters for the server power supply due to its high power capability and small secondary ripple current with the output inductor. Moreover, it can more reduce the secondary conduction loss by using parallel-connected mosfet s in SR. However, due to large input capacitance of the parallel-connected mosfet s in SR, the PSFB converter has large SR gate driving loss, which particularly degrades the light load efficiency. Thus, in this paper, one additional resistor is added to the conventional SR gate driving circuit to recycle the gate driving energy. As a result, the proposed circuit can improve the light load efficiency of the PSFB converter without operation mode change, additional controls, and complex circuits. The most advantage of the proposed circuit is that it is very simple and available to any other SR gate driver IC. The validity of the proposed circuit is confirmed by experimental results from a prototype with 340–400 V input and 12 V/66.66 A output.

A bi-directional bridgeless PFC converter (BBPFC) is fascinating topology for high power application among many bridgeless PFC converters due to small EMI filter size and simple control method despite of floating gate driver. By varying reverse recovery characteristics of diodes placed on the conduction path, it is possible to improve EMI characteristics without reducing power density. Therefore, when BBPFC is applied to high power application such as server power supply, it can be seen that it has the highest EMI performance and the highest power density. However, the way to improve the common-mode (CM) noise through this topology is difficult to actually use because of the patent already registered. In this paper, an improved bridgeless PFC converter (BPFC) for avoiding patent already registered is proposed. By using this proposed converter, the power system can achieve high EMI performance and high efficiency. Moreover, it is very simple to implement because the proposed converter is not required for floating gate driver. Also, when applied in DC input voltage conditions, the proposed converter has better characteristic due to utilizing only one switch for build-up operation. The principle and analysis of the proposed method are presented. The performance and feasibility are verified by analysis and simulation results from the high line, i.e. 230 VRMSinput, 800W/400V output prototype.

A new bridgeless totem-pole boost PFC rectifier is proposed to achieve a soft-switching for power factor correction (PFC) circuit. Based on the conventional totem-pole bridgeless rectifier, an auxiliary circuit is applied to retain zero-voltage-switching (ZVS) of main switches under the middle-to-heavy load conditions and minimized conduction loss under the light load conditions utilizing auxiliary switches. Moreover, the proposed converter can reduce additional conduction loss under the light load conditions without complicated control method. Therefore, the proposed converter can have high efficiency at the entire load conditions. The feasibility of the proposed converter is verified by experimental results of prototype configurations with universal AC input and 750W output.

In this paper, a dual half-bridge (HB) LLC resonant converter with a new hybrid secondary rectifier (HSR) is proposed for wide-output-voltage applications. In the proposed converter, the HSR can operate like a voltage doubler rectifier or voltage quadrupler rectifier according to the switching strategy of the dual HB LLC resonant converter. For low output voltage range, the dual HB LLC resonant converter are controlled by 180 degree phase-shifted gate signals. Thus, it can achieve low voltage gain with a voltage doubler rectifier. Whereas, in high output voltage range, in-phase gate signals are applied to the dual HB LLC resonant converter. Thus, the proposed converter can obtain high voltage gain with a voltage quadrupler rectifier. As a result, the proposed converter is able to be designed with narrow switching frequency variation, which results in high efficiency over the entire output voltage range. The validity of the proposed converter is confirmed by a 750W prototype with 400V input, 100-300V output.

A new high-efficiency two-inductor boost converter is proposed in this letter. The proposed converter has topology variation characteristic by an additional single-pole double-throw relay. By operating a two-phase interleaved boost converter at ac low line input and single-boost converter with two series-connected inductors at ac high line input, the proposed converter efficiently utilizes two inductors and switching components. Therefore, the proposed converter can be optimally designed and its efficiency can be maximized at the respective ac input range. The proposed converter can be the most attractive solution for high-efficiency server power supply and other universal input power-factor-correction applications.

In this paper, an LLC resonant converter using three metal-oxide-silicon field-effect transistor (MOSFET) switches is proposed for high efficiency with universal input voltage. At high line input, the proposed converter operates same as the conventional half-bridge (HB) LLC converter. At low line input, by changing the operation of three switches, the resonant tank of the proposed converter is divided into two resonant tanks and turns-ratio of the proposed converter is changed to half. As a result, the DC voltage gain is doubled for the low line input, which enables the proposed converter to be designed with large magnetizing inductance (L m ). Therefore, the proposed converter has low conduction loss and low turn-off switching loss over the entire input voltage range. The proposed converter is verified by experimental results with 90V ac ∼264V ac input and 45W/19V output prototype.

The improved three switch-active clamp forward (3S-ACF) converter is proposed in this paper. The proposed converter has minimized switching loss on all switches of 3S-ACF converter by simple change of gate control scheme without any additional components. In addition, current stress of clamp diode can be significantly reduced. Though, all switches of the proposed converter have low voltage stress similarly to those of conventional 3S-ACF converter. Therefore, the proposed converter can be the most attractive candidate for high efficiency power supply in wide input applications.

In phase-shifted full-bridge (PSFB) converter, using discontinuous conduction mode (DCM) is one of the most effective ways to improve efficiency in the light load condition. DCM of the PSFB converter allows getting reduced the duty ratio and zero voltage switching (ZVS) in the light load condition. Because of its simplicity, commercial IC adapted DCM by turning-off synchronous rectifiers (SRs). However, turning-off SRs causes large conduction losses in body diodes of SRs, and ZVS condition or optimized dead time are not defined yet. This letter proposes to use “AND-gated” control signals for SRs to reduce conduction losses in body diodes. Also, the ZVS condition is presented to design dead time easily. The feasibility of the proposed technique has been verified with 90-265 Vac input, 400 V link voltage, and 12V/750 W output server computer power supply system.

This paper proposes a new control method in the phase-shifted full-bridge converter for the server power supply, which is variable delay time of lagging-leg switches under the light load conditions. By widening the delay time, the switching occurs at the lower drain–source voltage and then switching loss can be reduced under the light load conditions. The voltage stress of synchronous rectifier switches is also reduced. Without additional power devices and side effects at heavy load condition, the higher efficiency under the light load conditions can be obtained. The analysis and experimental results are presented in this paper to confirm the validity of this study.

In this paper, a control method to achieve a high power density and improve the power factor (PF) in the light load conditions for a voltage range of 180∼305Vac using a cascade buck-boost PFC converter is proposed. Recently, the requirement of a 277Vac for an input voltage rather than a 240Vac has been increased in a power distribution stage. The output voltage of the PFC stage of the conventional boost PFC converter, which is widely used for the PFC stage, is increased to 450V under a voltage range of 180∼305Vac compared to the output voltage (400V) under a voltage range of 180∼264Vac, i.e, nominal 240Vac. Therefore, the volume of the output capacitor is also increased compared to a existing voltage range of 180∼264Vac, which reduces the power density of the PFC stage. Moreover, the conventional boost PFC converter has a poor PF in the light load conditions due to the phase leading input current caused by the input capacitor. To overcome these problems, this paper proposes the control scheme using a cascade buck-boost PFC converter in order to achieve the conventional output voltage (400V) under a voltage range of 180∼305Vac. Therefore, a smaller output capacitor can be used in the proposed method and achieve a high power density. Also, with proper control of an additional switch (Q1), the phase leading input current can be relieved. The concept and principles are explained and the performance of the proposed method is verified by the prototype converter with 800W conventional output (450V, 1.78A) and proposed output ( 400V, 2.00A).

This paper presents the implementation of a high-efficiency slim adapter using an resonant converter. A new structure of the slim-type transformer is proposed, which is composed of copper wire as the primary winding and printed-circuit-board winding on the outer layer as the secondary winding. The proposed structure is suitable for a slim and high-efficiency converter because it has advantages of easy utilization and wide conductive cross-sectional area. In addition, the voltage-doubler rectifier is applied to the secondary side due to its simple structure of secondary winding, and a filter is adopted to reduce the output filter size. The validity of this study is confirmed by the experimental results from an 85-W prototype.

The burst-mode control is generally used to regulate the output voltage of the ac/dc adapter under either lighter no-load condition. Although the burst-mode control reduces the switching loss, the control-IC and the feedback circuit at the output side still consume a large amount of power. In order to further reduce the power consumption at no-load condition, a no-load power reduction technique for ac/dc adapters is proposed in this paper. At first, the proposed technique employs a control-IC ON/OFF scheme to reduce the power consumption of the control-IC while the gate signal of primary power switch is idle. In addition, an out-put voltage drop scheme is adopted to cut down on the loss of the feedback circuit because the output voltage of the ac/dc adapter is not required to be regulated when the ac/dc adapter is disconnected from the load system. Thus, the proposed technique can greatly reduce the no-load power consumption below 30 mW. To verify the validity of the proposed technique, loss analysis and experimental results of 65 W/17.5 V ac/dc adapter are presented.

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.

The output voltage of an adapter for a laptop computer should vary according to the load current in order to supply power to the computer. To satisfy this requirement, an LLC resonant converter with an adaptive link-voltage-variation (ALVV) scheme is proposed in this letter. The proposed ALVV scheme helps the LLC resonant converter to operate at a nearly constant resonant frequency and also allows for the optimal design of the converter. High power density and high efficiency can therefore be obtained. The proposed LLC resonant converter with the ALVV scheme is analyzed theoretically and verified experimentally.

In low-to-medium power applications, an active-clamp forward (ACF) converter is popular for its simple structure and zero-voltage switching (ZVS) capability. However, the high voltage stress on switches can be a burden in high-input-voltage applications. To relieve this, a three-switch ACF (TS-ACF) converter, which employs two main switches for a forward converter and one auxiliary switch for an active-clamp circuit (ACC), is proposed in this paper. With a repositioned ACC, all the switches of TS-ACF converter have relatively low voltage stress compared to the conventional one. In addition, one of the main switches always ensures ZVS during the transformer reset. Consequently, the TS-ACF converter can be promising for high-input-voltage applications with high efficiency.

The flyback converter is one of the most attractive isolated converters in small power applications because of its simple structure. However, it suffers from a high device stress and a large transformer size. To relieve these drawbacks, a high-efficient pulsewidth modulation resonant single-switch isolated converter is proposed. The proposed converter derives the power using the resonance between transformer leakage inductor and secondary capacitor without a large filter inductor. Therefore, the switch turn-off loss and snubber loss are reduced by a sinusoidal-shaped current. Moreover, it has a reduced voltage stress on the secondary diodes without a dissipative snubber and a smaller transformer size. Therefore, it features a simple structure, low cost, and high efficiency. The operational principle and characteristics of the proposed converter are presented and verified experimentally with a 300~400 Vdc input, 70 Vdc/1.5 A output prototype converter.

The single sustaining driver (SSD) for an AC plasma display panel (AC-PDP) can simplify and optimize the circuit part of the PDP; however, it suffers from twice the high voltage stress of switches compared with the conventional sustaining driver. To solve this problem, a new SSD employing a voltage stress reduction technique is proposed. By adjusting the gate timing with the proposed simple structure, the voltage stresses of all devices are effectively ensured at the sustaining voltage.

A new double-ended type zero-voltage switching (ZVS) half-bridge zeta (HBZ) converter employing a double-ended rectifier (DER) is proposed. The proposed DER for the HBZ converter provides a bidirectional powering path in the rectifier. As a result, the improved voltage waveform of the rectifier reduces the output filter size and voltage stresses on rectifier components. Moreover, it offers a wide ZVS range. In addition, to minimize the secondary snubber loss, a simple lossless snubber is adopted. The operational principles and characteristics of the proposed converter are to be analyzed and verified experimentally.