Phase-shifted Full-bridge Research Articles

Synchronous Rectifiers Drain Voltage Overshoot Reduction in PSFB Converters

The requirements for the blocking voltage of the rectification devices on the secondary side of phase shift full bridge (PSFB) dc-dc converter topology are, by nature, higher than for other quasiresonant or fully resonant topologies (DAB, LLC). This is especially aggravated in wide range operation converters and further increased by the rectifiers' drain voltage overshoot. Unlike other resonant topologies, the inductor at the output of the PSFB effectively decouples the capacitor bank from the rectification stage, which otherwise acts as a strong lossless snubber. Higher blocking voltage requirements for the rectification devices worsen their Figure of Merit, increasing their related losses and decreasing the overall efficiency of the converter. In this article, the main causes of the rectifiers drain voltage overshoots in PSFB are analyzed. Design guidelines for the mitigation of the different causes are introduced, as well as a novel modulation scheme for the overshoot reduction, while the output filter operates in discontinuous conduction mode, without penalties in performance, complexity, or cost. A prototype of PSFB DC-DC converter of 3300 W, with 400-V input to 54.5-V output nominal voltages, was designed and built to test the proposed solutions achieving a peak efficiency of 98.12% at 50% of load.

Modeling of ZVS Transitions for Efficiency Optimization of the Phase-Shifted Full-Bridge Topology

The emergence of wide bandgap semiconductors paved the way for integration of high-efficiency, high-power-density converters into industrial applications. Key to achieving these performance goals is operation at high switching frequencies, which requires mitigation of switching losses by schemes, such as zero-voltage switching (ZVS). The phase-shifted full-bridge (PSFB) converter is a very appealing converter for such industrial applications. However, the mechanisms that underlie the operation of ZVS within this topology are complex, as they depend on the coupled influence of multiple system parameters. This article aims to provide a detailed analytical treatment of the ZVS mechanisms within this topology, along with a detailed study of the interdependence of the associated critical system parameters. A prototype 10-kW, SiC-based PSFB converter is employed to aid this discourse and provide empirical validations. The outcome of these studies is leveraged to identify a set of practical guidelines for tuning the ZVS mechanisms. These guidelines also consider the impact of practical nonidealities, which are often neglected in the literature. Overall, the theoretical formulations, parametric trade studies, and practical implementation suggestions presented in this article constitute a set of tools that designers can utilize to obtain the full performance entitlement of this topology in practice.

Reconfigurable Control of the Quasi-Parallel Voltage Regulator for Powering Laptop Processors

The quasi-parallel voltage regulator (VR) topology with a phase-shifted full-bridge (PSFB) converter and a synchronous buck converter (SBC) in quasi-parallel configuration gives high efficiency even with widely varying input voltage at high and medium loads but not at light loads. Moreover, the “loop gain shaping” approach to controller design for this converter does not give satisfactory dynamic performance. Therefore, this article proposes a state feedback controller which meets the stringent dynamic performance requirement of the VRs. Additionally, techniques to reconfigure the state feedback controller are proposed to operate this converter in different light-load operating modes to improve its light-load efficiency so that the converter becomes suitable for laptop VR application. In the light-load modes, the PSFB and the SBC operate alternately to regulate the load voltage, thereby saving the losses of one of the converters. At very light loads, a burst mode operation is proposed where both the converters remain inactive for most of the time, further increasing the efficiency. A unified control method which enables the converter to seamlessly change the operating modes of the converter, based on the computing load on the processor, is proposed and experimentally verified on a laboratory prototype for satisfactory performance.

Phase-Shifted Full-Bridge DC–DC Converter With High Efficiency and High Power Density Using Center-Tapped Clamp Circuit for Battery Charging in Electric Vehicles

In this paper, a phase-shifted full-bridge (PSFB) converter employing a new center-tapped clamp circuit is proposed to achieve high efficiency and high power density in electric-vehicle battery charger applications. By using a simple center-tapped clamp circuit, which consists of two diodes and one capacitor, many limitations in conventional PSFB converters are solved. The proposed center-tapped clamp circuit provides the clamping path and allows the secondary voltage stress to be clamped to the secondary-reflected input voltage. This results in a greatly reduced conduction loss in the secondary full-bridge rectifier (FBR) due to the low-forward-voltage drop of low-voltage-rated diodes, and the resistor–capacitor–diode snubber loss is eliminated. In addition, the circulating current in the primary side is removed without any duty-cycle loss. Furthermore, the turn- off switching loss in the FBR is substantially reduced due to the decreased reverse-recovery current and the reduced reverse voltage. With these advantages, high efficiency can be achieved. Besides, the size of the output inductor is considerably reduced with the aid of clamping voltage, resulting in a high power density with saving the cost. In order to confirm the effectiveness of the proposed converter, a 3.3-kW prototype was tested. Experimental results show that the proposed converter achieves high efficiency over the entire conditions with high power density.

Optimal Dead-Time Control Scheme for Extended ZVS Range and Burst-Mode Operation of Phase-Shift Full-Bridge (PSFB) Converter at Very Light Load

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.

Half-Bridge Integrated Phase-Shifted Full-Bridge Converter With High Efficiency Using Center-Tapped Clamp Circuit for Battery Charging Systems in Electric Vehicles

In this article, a half-bridge (HB) integrated phase-shifted full-bridge (PSFB) converter with a new center-tapped clamp circuit is proposed to achieve high efficiency in electric vehicle battery charging systems. The proposed converter has the benefits of HB integrated PSFB converters, such as the extended zero-voltage-switching range and the reduced conduction loss on the primary side. In addition, by using a new center-tapped clamp circuit, which consists of two diodes and one capacitor, the proposed converter can solve the drawbacks of conventional PSFB converters, such as the substantial circulating current, the severe voltage stress and switching loss in the secondary full-bridge rectifier, and a large output inductor. With these improvements, the efficiency is fairly increased, and the volume of the output inductor is reduced. In order to validate the feasibility of the proposed converter, a 3.3-kW prototype was built and tested.

A Practical Approach to the Design of a Highly Efficient PSFB DC-DC Converter for Server Applications

The phase shift full bridge (PSFB) is a widely known isolated DC-DC converter topology commonly used in medium to high power applications, and one of the best candidates for the front-end DC-DC converter in server power supplies. Since the server power supplies consume an enormous amount of power, the most critical issue is to achieve high efficiency. Several organizations promoting electrical energy efficiency, like the 80 PLUS, keep introducing higher efficiency certifications with growing requirements extending also to light loads. The design of a high efficiency PSFB converter is a complex problem with many degrees of freedom which requires of a sufficiently accurate modeling of the losses and of efficient design criteria. In this work a losses model of the converter is proposed as well as design guidelines for the efficiency optimization of PSFB converter. The model and the criteria are tested with the redesign of an existing reference PSFB converter of 1400 W for server applications, with wide input voltage range, nominal 400 V input and 12 V output; achieving 95.85% of efficiency at 50% of the load. A new optimized prototype of PSFB was built with the same specifications, achieving a peak efficiency of 96.68% at 50% of the load.

High-Efficiency Phase-Shifted Full-Bridge Converter With a New Coupled Inductor Rectifier (CIR)

A conventional phase-shifted full-bridge (PSFB) converter is one of the most promising topologies in high-efficiency and high-power applications because of its small RMS current, inherent zero-voltage switching capability, and clamped voltage stress of the primary switches. However, when the PSFB converter operates with a small duty ratio, a large freewheeling current of an output inductor flows in the primary side, and it causes a large circulating current. In addition, it has a large voltage stress in the rectifier diodes due to a voltage ringing between parasitic components. To solve these problems, a new PSFB converter with a coupled inductor rectifier (CIR) is proposed in this paper. By adopting the CIR structure in the PSFB converter instead of the full-bridge rectifier, the proposed converter eliminates the freewheeling current in the primary side, which significantly reduces the primary circulating current. In addition, the two rectifier diodes of the CIR do not have voltage ringing. As a result, the proposed converter not only reduces the conduction loss in the primary side, but can also use two diodes in the rectifier with a low voltage rating. The effectiveness and feasibility were verified with a 320-400 V input and 56-V/12.8-A output prototype.

Design of 2kW DC Charger for Two Wheelers

The demand for Electric Vehicles is increasing day by day. EVs are silent, nonpolluting and produce zero emissions. This paper presents the design of a dc charger that performs the necessary functions for charging EV battery. An EV charger is a component in EV environment that supplies power for recharging the EV battery. Usually, charging an electric car seems to be very simple process, implying that one can plug one’s car into a charger that is connected to the electric grid. However, it is not as that simple. It depends on the types of EVSE that one has deployed. Offboard DC Charger is connected to the premises wiring of the mains ac supply network .It is designed to be separate and operate entirely off the vehicle. In the offboard dc charger, direct current electrical power is delivered directly to the vehicle. The power module in a DC fast charger consists of an AC-to-DC rectifier converter and an isolated DC/DC converter. The AC-to-DC rectifier is power factor correction stage in which a Vienna Rectifier based PFC converter is used. The Isolated DC-DC Converter used here is the Phase Shift Full Bridge DC-DC converter. A 2 kW prototype of the offboard DC Charger is designed and simulated in MATLAB/Simulink R2018b.

Simple soft‐switched phase‐shifted FB converter for reduced voltage stress and negligible duty cycle loss

A simple modified configuration of the conventional phase-shifted full-bridge (C-PSFB) converter, phase-shifted FB converter without filter inductor (PSFB-w/o-L) is proposed in this study in order to reduce the peak voltage stress on the rectifier diodes. As the proposed configuration is devoid of filter inductor, it features lighter weight and low cost. As the proposed configuration is achieved eliminating the filter inductor, the maximum voltage that comes across the rectifier diode is limited to the output voltage, thus eliminating the need for snubber circuit. Additionally, the proposed PSFB-w/o-L has the advantage of negligible duty cycle loss. A comprehensive analysis on the mechanism of the peak voltage problem across the rectifier diode in the C-PSFB is addressed and the way it is eliminated in the proposed PSFB-w/o-L is described. The detailed analysis of the operation and design consideration of the proposed PSFB-w/o-L is presented. Simulation and experimental results are presented to verify the analysis.

Design of ZVS DC/DC converter based on DSP2812 phase-shifted full bridge

The phase-shifted full-bridge DC/DC converter is a very important component of power electronics and is suitable for medium and large power output applications based on switching power supplies. Aiming at the implementation of soft-switching and the problem of power loss, this paper firstly describes the structure and working mode of DC/DC converter, then analyzes the calculation and selection process of resonant inductance and capacitance parameters in the converter, and finally adopts the traditional PI control to achieve stable control of the output voltage. The simulation and experimental results fully prove the feasibility and rationality of the design and parameter selection of this scheme.

Modulation Scheme for the Bidirectional Operation of the Phase-Shift Full-Bridge Power Converter

This paper proposes a novel modulation technique for the bidirectional operation of the phase-shift full-bridge (PSFB) dc/dc power converter. The forward or buck operation of this topology is well known and widely used in medium-to-high-power dc-to-dc converters. In contrast, backward or boost operation is less typical since it exhibits large drain voltage overshoot in devices located at the secondary or current-fed side—a known problem in isolated boost converters. For that reason, other topologies of symmetric configuration are preferred in bidirectional applications. In this work, we propose a modulation technique overcoming the drain voltage overshoot of the isolated boost converter, without additional components other than the ones in a standard PSFB and still achieving full or nearly full ZVS in the primary or voltage-fed side devices along all the load range. The proposed modulation has been tested in a bidirectional 3.3 kW PSFB achieving a 98% of peak efficiency in buck mode (380 V input, 54.5 V output), and a 97.5% in boost mode (51 V input, 400 V output). This demonstrates that the PSFB converter may become a relatively simple and efficient topology for bidirectional dc-to-dc converter applications.

Hybrid Modulation of Parallel-Series $LLC$ Resonant Converter and Phase Shift Full-Bridge Converter for a Dual-Output DC–DC Converter

A novel pulse frequency and phase shift hybrid modulated dual-output dc–dc converter is proposed in this paper. The proposed converter is composed of hybrid modulation of an input-parallel-output-series LLC resonant converter and a phase shift full bridge (PSFB) converter. The output voltage of the LLC resonant converter is modulated by the switching frequency, whereas the output voltage of the PSFB converter is modulated by the phase angle; therefore, the two output voltages are regulated independently and free from cross regulation. The series inductor of the PSFB converter does not need to be specially designed to help achieving the soft switching operation, and the duty cycle loss could be mitigated. Zero-voltage switching can be achieved on the power switches in the whole load range. Finally, a 1.2-kW 400-input 200–400-V and 48-V output prototype is built and tested to verify the effectiveness of the proposed converter.

Hybrid mode control for wide range soft‐switched full‐bridge converter with auxiliary parallel inductor networks

Aiming at the limitations of conventional phase-shifted full-bridge (PSFB) converter, such as, narrow zero-voltage switching (ZVS) range and large duty cycle losses, here, a wide range soft-switched full-bridge (FB) converter using hybrid mode control is proposed. Given using of two auxiliary inductors under light load, the energy that required for soft switching is satisfied and thus, ZVS can be achieved, and, therefore, efficiency of converter can be improved significantly under light load. Furthermore, the duty cycle losses of the secondary side are reduced by using a transformer with the small leakage inductor. Based on these merits, the proposed converter has some advantage for the wide range load variation applications without duty cycle losses. This paper presents the circuit configuration of the proposed converter and analyses its operating principles. Experimental results of an 800 W 200/50 V prototype are presented to validate the effectiveness of the proposed converter.

Lumped parameter model of the novel L‐C‐T used in the PSFB ZVS converter

A novel inductor-capacitor-transformer (L-C-T) has been proposed to integrate the passive components into an integrated magnetic component. The phase-shift full-bridge (PSFB) zero-voltage switching (ZVS) converter with a novel L-C-T has high-power density performance, which is used in electromagnetic exploration. The structure of the novel L-C-T is very complicated, and the lumped parameter of the L-C-T is very difficult to determine. Based on the dual method of the magnetic circuit, the electromagnetic energy method and the six-lumped capacitance method, a lumped parameter model suitable for the novel L-C-T is proposed. Moreover, the experiments and finite element analysis (FEA) are used to verify the accuracy of the lumped parameter model, and a 40 kW prototype of the PSFB ZVS converter with a novel L-C-T is designed and tested.

Evaluation of Power Processing in Series-Connected Partial-Power Converters

This paper proposes an analytical methodology to evaluate the power processed by dc–dc converters operating as series voltage regulators, which provide an alternative to increase efficiency in photovoltaic systems. Via the analysis of both active and nonactive power processing, the proposed methodology allows to clearly distinguish among circuit topologies as truly partial-power processing (PPP) or just partial active power processing topologies. When an isolated dc–dc topology is connected in series as a voltage regulator, the overall processed power can be reduced, which reduces power losses and improves efficiency. Conversely, this paper also demonstrates that some series-regulator topologies may not actually reduce the proportion of nonactive processed power. To demonstrate the applications of the proposed methodology and to emphasize its significance, two well-known series-connected voltage regulators (flyback and full-bridge phase shift) and a full-power regulator (boost) were evaluated. The results indicate that the full-bridge series regulator can perform a true PPP, whereas the flyback series-regulator processes the same amount of power as that processed by conventional nonisolated boost converters and cannot be considered a partial-power topology. This study finding contradicts assertions in the literature that this topology achieves high-efficiency dc–dc conversion through PPP. To confirm the theoretical analysis, experimental results from three 750-W prototypes are presented alongside its simulations.

A Novel Hybrid Mode Control for a Phase-Shift Full-Bridge Converter Featuring High Efficiency Over a Full-Load Range

A novel hybrid mode control technique for a phase-shift full-bridge (PSFB) converter is proposed in this paper. The proposed method can improve power efficiency under both the light-load and heavy-load conditions. The basic concept of the proposed control technique is to decrease the turns ratio to reduce the circulating current, hence resulting in lower circulating losses. However, the output voltage under heavy load may not be stabilized using phase-shift control if smaller turns ratio is utilized. Therefore, the proposed technique employs asymmetrical pulsewidth modulation to achieve higher output voltage. To further improve the efficiency, an adaptive dead-time control method, which determines the dead-time value according to the load level, is also proposed. To validate the correctness and effectiveness of the proposed method, a 480-W PSFB converter is constructed and experiments are carried out accordingly. Comparing with a conventional PSFB converter, the efficiency of the proposed method can be improved up to 3.2%, 1.3%, and 0.6% under light-load, 30% load, and full-load conditions, respectively.

Hardware Implementation of GaN-HEMT Based ZVS DC–DC Converter Considering PCB Layout

The gallium nitride high electron mobility transistors (GaN HEMT) are among the most promising power semiconductor devices. However, these transistors have a small gate voltage margin compared with conventional power devices. In this paper, the gate voltage of GaN HEMTs is mathematically analyzed when it is applied to a zero voltage switching (ZVS) phase-shift full bridge (PSFB) DC–DC converter. The analysis accounts for nonlinear capacitance characteristics under the ZVS switching condition, and a critical parasitic inductance are derived to restrict the gate voltage to a safety operation area. The optimal layout for bridge topologies and gate drivers is proposed, to satisfy the derived parasitic inductance limitation. A 500-W-power laboratory phase-shift full-bridge DC–DC converter is implemented to verify the proposed layout.

Analysis and Control of Input-Parallel Output-Series Based Combined DC/DC Converter With Modified Connection in Output Filter Circuit

Input-parallel output-series (IPOS)-based combined converter is usually used in the situation with low input voltage and high output voltage to satisfy the requirements in switch voltage stress reduction and power expansion. In such a system, the voltage balance of filter capacitor in the output side or current sharing in the input side usually used to guarantee the control performance of the conversion system. In this paper, a phase-shifted full bridge (PSFB)-based IPOS converter with modified connection of output filter circuit used for the wide variation of input voltage is proposed, which is beneficial to reduce ripple current of filter inductor significantly. A control scheme using the same phase shifting for the two different modules of this IPOS converter is detailedly investigated with both steady state and small signal model-based analysis, it manifests that special voltage balance and current sharing control scheme are not necessary for IPOS system under the common phase shifting control method. And the small signal transfer functions of this topology used for dual loop control system design are also developed. The simulation and experiment results are presented to validate the analysis and control scheme.

Virtual Resistor-Based Integrated DC Bus Voltage Conditioner for Stability Improvement of Cascaded Power Converters

A bidirectional integrated bus voltage conditioner (IBVC) for an isolated phase-shifted full bridge (PSFB) dc/dc converter is proposed to reduce the dc bus voltage oscillations in a cascaded power converter system, where a load converter is controlled tightly with high-control bandwidth. In the proposed method, unlike conventional dc bus voltage stabilization methods for which auxiliary switches are used, the multiplexing utilization of the full bridge switches at the primary side of a PSFB is adopted. In this paper, to improve the dc bus voltage stability, an equivalent virtual resistor is implemented by applying the duty cycle regulation for both legs of the PSFB. The effectiveness of the proposed method on the dc voltage stabilization is examined through simulations and experiments. The achieved results reveal that the dc bus voltage stability is significantly improved with the proposed method.