Duty Cycle Loss Research Articles

Research on Phase-Shifted Full-Bridge Circuit Based on Frequency and Phase-Shift Synthesis Modulation Strategy

The full-bridge converters usually use transformer leakage inductance and parallel resonant capacitors to achieve smooth current commutation and soft switching functions, which can easily cause problems such as energy leakage and significant duty cycle loss. This paper designs a novel full-bridge zero-current (FB-ZCS) converter with series resonant capacitors and proposes a frequency and phase-shift synthesis modulation (FPSSM) control strategy based on this topology. Compared with the traditional parallel resonant capacitor circuit, the passive components used are significantly reduced, the structure is simple, and there is only a slight energy loss. By controlling the charging time of the capacitor, it can be achieved without additional switches or auxiliary circuits. The automatic control of capacitor energy based on input current addresses the low efficiency of the traditional control strategies. This paper introduces its principle in detail and verifies it through simulation. Finally, an experimental prototype was built further to demonstrate the feasibility of the theory through experiments. The module can be applied to a photovoltaic DC collection system using input parallel output series (IPOS) cascade to provide a new topology for large-scale, long-distance DC transmission.

Wide Input Variable Mode ZVZCS Converter Design

With the emphasis on energy conservation and emission reduction in various countries, industries such as new energy power generation and electric vehicles have developed rapidly. In many applications, the converter needs to adapt to a wide input voltage range, for example, the input voltage range of electric car charger is 200 ~ 450V. Based on this, this paper proposes a wide-input variable-mode ZVZCS converter for electric vehicles with two operating modes. Before the MOSFETs of the lagging-legs is opened, the primary side current is extinguished by the auxiliary circuit to realize ZCS. Due to the parasitic inductance and diode of MOSFETs, ZVS is realized by MOSFETs on leading-legs. It not only broadens the input voltage range of the traditional phase-shifted full-bridge ZVZCS converter, but also keeps the advantages of the traditional phase-shifted full-bridge ZVZCS converter, such as wide load range and small duty cycle loss. Experimental results with 60 ~ 240 V input voltage are demonstrated to verify the advantages.

An Investigation of Zero-Voltage-Switching Condition in a High-Voltage-Gain Bidirectional DC–DC Converter

This paper analyzes the zero-voltage switching (ZVS) for all switches in a high-voltage-gain bidirectional DC–DC converter in triangular conduction mode (TCM) operation without any auxiliary components. From the ZVS condition, the reverse inductor current can be derived, and the required dead-time duration between the main switches and SR switches can be determined, which leads to a reduction in the duty cycle loss. Moreover, the relationship between switching frequency and load in TCM operation can be determined, which helps to reduce the peak-to-peak inductor current and reduce the conduction loss at light load. An experimental prototype of a high-voltage-gain bidirectional DC–DC converter is implemented with a maximum output power of 48 W. The result shows the peak efficiency of 97% and 96.8% in the forward and reverse directions, respectively.

Design and Implementation of Improved High Step-Down DC-DC Converter for Electric Vehicles

An improved high step-down DC-DC converter for charging the batteries in an electric vehicle application is proposed in this paper. It adopts the topology of the conventional full-bridge converter, which has a coupled inductor current-doubler rectifier as the secondary side of the transformer. In addition, four power switches are driven using a phase-shifting technique. The proposed converter can achieve a high step-down voltage with low-voltage stress on the rectifier diodes. In addition, the coupled inductor current-doubler rectifier of the secondary side can reduce the ripple current and losses of the secondary side to achieve high efficiency. Furthermore, the proposed converter can overcome the drawbacks of the conventional full-bridge converter, such as switching loss caused by high switching frequency, duty-cycle loss, voltage stress, and numerous components, and can increase the efficiency with the soft-switching technique. A 600 W laboratory prototype of the proposed converter was manufactured. The results of the experiments performed with the prototype proved the effectiveness and validated the use of the proposed converter for better charging of electric vehicles.

A Simple, Accurate Small-Signal Model of a Coupled-Inductor-Based DC-DC Converter Including the Leakage Inductance Effect

This brief proposes a method to dynamically modeling the coupled-inductor double-boost converter operating in continuous-conduction mode. Such method has the advantage of including the leakage inductance effect on the dynamic behavior of the converter in a simple, straightforward approach. The presence of the leakage inductance is initially neglected and a traditional circuit-averaging technique is used. The averaged models are then refined by accounting the impacts of the reported inductance. Since its major impact is on the damping factor of the system, this dynamic change is modeled by equivalent resistors. Equations for describing the equivalent resistors are derived based on the analysis of the duty cycle loss caused by leakage inductance in the static gain of the converter. The effect on the averaged small-signal model is shown by a closed-form control-to-output transfer function and experimental results demonstrate its accurate performance.

An Improved Adaptive Synchronous Rectification Method with the Enhanced Capacity to Eliminate Reverse Current

Adaptive synchronous rectification (SR) is a good solution to solve duty cycle loss for LLC resonant converter. Usually, whether the synchronous rectifier is turned off prematurely or late can be detected by whether the body diode is conducted on or not. However, when the switching frequency is below the resonant frequency, both SR turning- off prematurely and late may generate body diode conduction (BDC), which will cause logic errors in the conventional adaptive SR strategy. Then, a large reverse current from load to source will occur, which damages the efficiency. To solve the problem, the time-domain modeling of the SR drain-to-source voltage is established to analyze the mechanism of BDC caused by SR turning- off late. Moreover, an improved adaptive SR driving scheme is proposed, which can identify the two different types of BDC and tune SR to be turned off exactly. Finally, a 280 W LLC prototype is built to verify the established model and the proposed SR method. The prototype proves that both the duty cycle loss and the reverse current are eliminated and efficiency improvement of 0.54% is achieved.

A comparison of different DC-DC converter topology for electric vehicle charging

The DC-DC converter with soft switching technique is now a widely accepted industrial application/electric vehicle. But it also deteriorate from some problems like duty cycle loss, conduction loss, circulating current loss, narrow range of soft switching, and voltage ringing. Some methods are proposed to rectify these problems to make the DC-DC converter more efficient. In this paper, typical auxiliary networks are analysed and classified. The features and limitations of the DC-DC converters are compared. Finally, the characteristics of the DC-DC converter are summarised to choose the best topological architecture for electric vehicle application.

A ZVZCS Hybrid Dual Full-Bridge Converter Suitable for Wide Input Voltage Range

A phase-shift modulated converter with two full bridges at primary side and rectifier diodes in hybrid combination at secondary side is proposed in this article. Due to the proposed symmetrical modulation strategy, two full-bridges always equally share the total system power rating, and thus the VA rating of two transformers is minimized. The circulating currents decay to zero in the zero state, contributing to reduce the conduction loss and duty-cycle loss. Zero-voltage or zero-current switching is achieved for all switches over whole input voltage range with an auxiliary inductor. The rectifier output voltage is synthesized of two controlled transformer secondary voltages all the time, which achieves the same output current ripple suppression effect as the conventional input-parallel output-parallel full-bridge converters with interleaved control scheme, and reduces the voltage stress of rectifier diodes. These advantages make the converter suitable for wide input voltage range applications. In this article, the operation principle and steady-state analysis of the proposed converter are illustrated in detail. Experimental results with 220–460 V input voltage are demonstrated to verify the advantages.

A Comparison of Different DC-DC Converter Topology for Electric Vehicle Charging

The DC-DC converter with soft switching technique is now a widely accepted industrial application/electric vehicle. But it also deteriorate from some problems like duty cycle loss, conduction loss, circulating current loss, narrow range of soft switching, and voltage ringing. Some methods are proposed to rectify these problems to make the DC-DC converter more efficient. In this paper, typical auxiliary networks are analysed and classified. The features and limitations of the DC-DC converters are compared. Finally, the characteristics of the DC-DC converter are summarised to choose the best topological architecture for electric vehicle application.

Low MOSFET Count Isolated DC–AC Converter

This letter proposes a novel soft-switched single-stage-isolated dc-ac converter topology from the industry point of view. The proposed converter requires a lesser number of MOSFETs compared to a widely studied cycloconverter-type (CCT)-isolated dc-ac converter topology. This converter provides lower duty cycle loss, better efficiency, and electromagnetic interference performance compared to a CCT dc-ac converter. Also, it is thermally more stable, thus requires a smaller heat sink. The converter operation is demonstrated in a 1-kW prototype developed with SiC MOSFETs.

FB-ZCS DC–DC Converter With Dual-Capacitor Resonant Circuit for Renewable Energy Integration With MVDC Grids

Full-bridge zero-current-switching (FB-ZCS) dc–dc converters realize quasi-resonant soft-switching and smooth current commutation by utilizing the leakage inductance of high-frequency transformer and a resonant capacitor. The following two types of resonant capacitor configurations are proposed in the literature: First, shunt-connected across the transformer-secondary and, second, series-connected with the transformer-primary. Shunt-connected capacitor has the drawbacks of storing full-load-rated resonant energy irrespective of converter loading. This results in large duty-cycle loss and consequently regulation loss at light-loads. Series-connected capacitor addresses this issue but suffers from higher peak-voltage stress across components and insufficient voltage for resonance at light-loads. To address these limitations, a dual-capacitor resonant circuit is proposed in this article. Series-capacitor facilitates current-adaptive resonant energy storage and shunt-capacitor is designed only for a fraction of full-load-rated resonant energy, which lowers the duty-cycle loss and supports soft-switching at light-loads. This combination also reduces the series-capacitor voltage required for resonance, thereby reducing the peak-voltage stress. Steady-state analysis of converter operation is presented and the advantages over existing converters are demonstrated through simulations for medium-voltage dc application. Experimental results from a scaled-down prototype are presented to validate the proposed converter.

Analysis and Design of ZVZCS Full-Bridge Converter With Reduced Components for Input-Series-Output-Parallel Application

Different from the conventional performance improvement of a single phase-shift full-bridge (PSFB) converter by adding auxiliary components, this article utilizes the intrinsic advantage of multimodule in the input-series-output-parallel (ISOP) application to achieve zero-voltage and zero-current switching (ZVZCS) operation of switches and reduce the duty-cycle loss and conduction loss in two PSFB converters through their interaction. The interaction is established by sharing the secondary rectifier diodes, and hence the number of components used in the proposed converter is reduced compared with the ISOP PSFB converter. Moreover, the voltage stress of the shared diodes is reduced. As a consequence, lower cost is achieved along with the improved performance. In this article, operational principle and relevant analysis of the proposed ZVZCS PSFB converter with reduced components are presented in detail to obtain a comprehensive understanding. Besides, its small-signal model is gained and a closed-loop control scheme is accordingly designed to improve the dynamic performance. Finally, the favorable advantages of the proposed converter are experimentally verified in a prototype circuit with 400 V input and 120 V/500 W output.

Duty Cycle Loss Compensation Method Based on Magnetic Flux Cancelation in High-Current High-Frequency Synchronous Rectifier of LCLC Converter

With uncertainty of the parasitic parameter in different practical layout, two synchronous rectifiers (SR) with same topology and identical components may exhibit significant difference in driving timing and each SR FET may suffers from the duty cycle loss. In this article, the mutual induction between the voltage detection network of SR controller and the transformer secondary windings is first investigated. Then, a compensation method based on magnetic flux cancellation is proposed to solve the duty cycle loss issue caused by the parasitic inductive coupling, which enables further increase of switching mode power supply efficiency. With the proposed compensation method, only an additional wire turn is required with no need to change the layout, resulting in reducing the difficulty for implementation in practical prototypes. Where, a most compatible method is employed after multiparameter extraction methods comparison and the parasitic parameters are given out. Then, the design process of a specific compensator is proposed. Finally, a prototype of 400 to 14 V, 1.5 kW LCLC resonant converter was employed to verify the advantages of the proposed method. An efficiency improvement of 0.8% is achieved. The method can be generally applied to different kinds of SR controllers. This article is accompanied by a video demonstrating operation waveforms.

ZVZCS Full-Bridge Three-Level DC/DC Converter With Reduced Device Count

This letter proposes a new zero-voltage and zero-current switching (ZVZCS) full-bridge (FB) three-level dc/dc converter (TLDC) with the reduced device count. The merits of the proposed converter with the corresponding modulation strategy are concluded as follows. In comparison with the zero-voltage-switching FB TLDC: 1) only one blocking capacitor is added to realize the ZVZCS strategy, 2) the primary circulating current and duty cycle loss can be effectively reduced. Also, the wide input voltage range can be satisfied because of having two working patterns. More significantly, the proposed converter with the corresponding modulation strategy can reduce the device count by removing the primary blocking diodes in comparison with other ZVZCS FB TLDCs, which would reduce the conduction losses of primary power devices and thus increase the converter's efficiency. Finally, experimental results are presented to verify the proposed converter with the corresponding modulation strategy.

Modulation Method and Control Strategy for Full-Bridge-Based Swiss Rectifier to Achieve ZVS Operation and Suppress Low-Order Harmonics of Injected Current

The Swiss-type rectifier (SR) uses a three-phase unfolder circuit to convert the ac voltage into two time-varying positive voltages. The power factor correction of ac sides and the stable dc voltage output can be realized by using two dc-dc topologies without any bulky decoupling capacitors. By applying the phase-shifted full-bridge topology into the dc structure, both the soft-switching and the high-frequency electrical isolation can be achieved. However, the power coupling between two full bridges using the traditional modulation method will affect the zero-voltage switching (ZVS) condition of lagging legs. Then, the duty cycle loss caused by the transformer leakage inductance will affect the input and output performance. Therefore, a new method using the up-counting mode modulation is proposed to implement the ZVS for both the lagging switches. Then, the relationship between the duty cycle loss and the extra 6N ± 1 harmonics added into the input current is theoretically analyzed. Hence, to suppress the low-order harmonics, a novel compensation strategy is proposed. The proposed modulation method and control strategy have been successfully verified by the experiments. 95% efficiency under half-rated power and 3% input current total harmonic distortion (THD) under rated power have been achieved under a 10-kW 380 Vac input/400 Vdc output prototype with 90-kHz switching frequency.

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.

IPOP-Connected FB-ZCS DC–DC Converter Modules for Renewable Energy Integration With Medium-Voltage DC Grids

This paper presents a dc–dc input-parallel output-parallel (IPOP) converter configuration for renewable energy integration with medium-voltage dc grids. A full-bridge zero-current-switching (FB-ZCS) converter with voltage-doubler output is proposed as the fundamental module. To achieve smooth current commutation and ZCS, the leakage inductance of transformer and a resonant capacitor across its secondary are utilized. This resonant capacitor is always charged to its full-rated capacity irrespective of converter loading and requires a dedicated charging interval resulting in duty-cycle loss. For a given leakage inductance, a large resonant capacitor is required for higher current ratings. With a single-centralized converter, these operational and design constraints result in significant duty-cycle loss, restricting the operation range. This paper proposes an IPOP configuration for high-power applications. Phase shedding at reduced loading ensures that individual modules are operated optimally. Input inductance requirement in modules is reduced due to interleaving of the input current. Additionally, voltage stress across converter components and input current ripple are reduced by 50% in the proposed converter modules. Steady-state operation, modeling, current-sharing control, start-up, and shutdown of modules in the IPOP configuration are demonstrated using simulations. Experimental results on a scaled-down prototype are presented to validate its operation.

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.

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.

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.