Synchronous Rectifier Research Articles

An isolated high step‐down DC–DC converter with dual coupled inductors for ultracapacitor charger applications

SummaryIn this paper, an isolated high efficiency, high step‐down DC–DC converter for ultracapacitor charger applications is presented. In the proposed converter, by utilizing the structure of asymmetrical half‐bridge that combined the current‐doubler synchronous rectifier and the technique of coupled inductors to achieve high step‐down. The step‐down conversion ratio of the proposed converter can be increased by decreasing the turns ratios of transformer and coupled inductors. In contrast to the conventional full‐bridge or half‐bridge converter, the proposed converter can operate in a high step‐down situation; the extreme low duty and turns ratios are not necessary. The theoretical results are verified by experimental results, in the case of 380 V input voltage and 14.6 V output voltage with rated power 1 kW. In addition, the 250F ultracapacitor charged by prototype of the proposed converter from 0 to 14.6 V in 1 min verified its feasibility.

Synchronous Rectification and Parameter Design Based on Accurate Time-Domain Model for Asymmetrical CLLC Resonant Converter

Synchronous Rectification and Parameter Design Based on Accurate Time-Domain Model for Asymmetrical CLLC Resonant Converter

A Switching Delay Strategy for Sensorless Synchronous Rectification in CLLC Converters

A Switching Delay Strategy for Sensorless Synchronous Rectification in CLLC Converters

A Novel All-Passive Resonant Gate Driver for LLC DCX Synchronous Rectification

A Novel All-Passive Resonant Gate Driver for LLC DCX Synchronous Rectification

Geometrical State-Plane-based Synchronous Rectification Scheme for LLC Converter in EVs

Geometrical State-Plane-based Synchronous Rectification Scheme for <i>LLC</i> Converter in EVs

A High-Speed Synchronous Rectifier With Improved Dead Time Compensation and Suitable for High-Voltage Applications

A High-Speed Synchronous Rectifier With Improved Dead Time Compensation and Suitable for High-Voltage Applications

Model-Free Bidirectional Synchronous Rectification Control Scheme for LLC-Based Energy Storage System in Electric-Vehicle Energy Router

LLC resonant converters have been widely used in electric-vehicle energy router (EVER) as part of energy storage (ES) system, resulting in the increased demand for bidirectional synchronous rectification (SR) control. However, conventional bidirectional SR schemes are respectively limited by high cost of current sensing, difficulty of high voltage sensing, narrow operating range or high computational burden, especially for EVER. To deal with this problem, this paper proposes a model-free bidirectional SR control scheme for LLC-based ES system in EVER. Firstly, a novel SR tuning principle based on Kirchhoff’s law and phase relationship between inverter control signal and rectifier-side current is proposed. It no longer needs to calculate complicated models. Based on this principle, SR control signals in both forward and reverse modes are tuned by known signals available from main controller in ES system. To this end, no additional sensing component is required and the cost of SR is reduced. Meanwhile, an adaptive DC bus current compensation strategy is designed. It can guarantee high SR accuracy in reverse mode without sensing DC bus current. Moreover, an analog-digital mixed implementation is provided in which signal computation is performed by analog circuit. With these effects, the proposed scheme can achieve bidirectional SR control effectively over a wide operating range with low computational burden on controller. A 400-V/36-V 1-kW bidirectional LLC prototype is built to verify the proposed scheme.

A Modularized Voltage Equalizer Based on Phase-Shift Modulation for Series-Connected Battery Strings

The modular design can effectively improve the circuit extensibility and control flexibility of equalizers for long series-connected battery strings. This paper proposes a modular battery equalizer based on phase-shift modulation. The LC resonant converters with synchronous rectification are employed as the automatic cell-level equalizer to realize any-cells-to-any-cells (AC2AC) equalization and soft-switching operation, which enhances the balancing speed and efficiency. Different cell-level equalizers are connected with auxiliary windings. The fast equalization between modules is achieved by adjusting the phase shift of driving signals applying for the cell-level equalizers. A prototype with three modules, each consisting of three series cells, is built and tested. Experimental and comparative results confirm the validity and characteristics of the proposed modular equalizer.

Class-E Synchronous RF Rectifier: Circuit Formulation, Geodesic Trajectory, Time-Domain Simulation, and Prototype Experiment

This paper formulates a class-E synchronous RF rectifier from a new viewpoint. The key point is to introduce a matrix and convolute the DC terms into RF matrices. The explicit expression of input impedance is demonstrated in plane geometry. We find out their input impedance exhibits a geodesic arc in hyperbolic geometry under ZVS operation, where the theoretical RF-DC conversion efficiency results in 100%. We verify the developed theory both numerically (circuit simulation) and experimentally (6.78 MHz, 100 W). We confirm that the input impedance becomes a geodesic arc for a wide range of DC load resistance. The presented theory is quite elegant since it is based on a matrix-based formulation and plane-geometrical expression.

Switched Capacitor-Based Bidirectional Power Converter with Enhanced Voltage Boost and Reduced Switching Strain for Electric Vehicle Applications

This research work presents an improved design of a bidirectional converter for EVs, specifically focusing on its buck and boost operations. The proposed design incorporates a switched capacitor-based double switch converter, which offers enhanced performance compared to conventional converters. The utilization of switched capacitors reduces voltage stress on switches and improves overall efficiency, making it well-suited for electric vehicle applications. Moreover, the inclusion of synchronous rectification enables zero voltage switching, further enhancing the converter's performance. The effectiveness of the design is verified through MATLAB simulations, demonstrating improved voltage gain and reduced switch stress in both voltage increasing and decreasing modes.

Fundamental impedance-based digital synchronous rectification scheme for bidirectional CLLC resonant converters

Fundamental impedance-based digital synchronous rectification scheme for bidirectional CLLC resonant converters

Evaluation of antiparallel SiC Schottky diode in SiC MOSFET phase-leg configuration of synchronous rectifier

The MOSFET synchronous rectification (SR) is widely used to reduce the conduction loss during the freewheeling period. Due to the wide band gap of silicon carbide (SiC), the intrinsic body diode of SiC MOSFET exhibits a high voltage drop. Therefore, SiC Schottky diodes (SBD) and SiC MOSFETs are usually used in reverse parallel to reduce power loss. However, the increase of equivalent junction capacitance due to the addition of an external SiC SBD could bring larger turn-on current on opposite power transistor of the phase-leg. Furthermore, as the parasitic inductance associated with layout hinders the prompt transfer of current between SiC SBD and body diode, the external SiC SBD cannot be fully utilized, and it may deteriorate the overall performance, especially at heavy load. We comprehensively compare power losses when SiC SBD are antiparallel or not, at different working conditions, including different layout compactness, load current and dead time. It’s hard to get the effect of loss reduction loss when add antiparallel SiC SBD due to the parasitic inductance induced by the layout. The results can provide a guidance to properly select SiC SBD in a phase-leg configuration under SR mode for freewheeling during the dead time.

Self-Powered Synchronous Electric Charge Extraction Rectifier for Rotational Electret Energy Harvester With Dual-Stage Electrodes

Self-Powered Synchronous Electric Charge Extraction Rectifier for Rotational Electret Energy Harvester With Dual-Stage Electrodes

High-Efficiency Multioutput LLC Resonant Converter With Multiwinding Transformer and Cost-Effective Analog Control Circuit

A new multi-output LLC resonant converter with a multi-winding transformer is proposed. In the proposed converter, the main output is controlled by the pulse frequency modulation of the primary switches, and the additional outputs are regulated by the pulse width modulation of the secondary synchronous rectifiers (SRs). Synchronization between the primary switches and the SRs can be easily achieved by sensing the voltage across the secondary side of the transformer at the main output with simple and cost-effective analog circuitry. The proposed converter features high efficiency because of the reduced transformer core loss and conduction losses in the primary switches. It also achieves high power density because of the small size of the transformer, resonant capacitor, and primary switches. The validity of the proposed converter is verified through experiments on a prototype for a 55-inch TV power supply converting 390 VDC input to 13 V/6.3 A and 65-83 V/ 2.25 A outputs.

Machine Learning-Based Optimization of Synchronous Rectification Low-Inductance Current Secondary Boost Converter (SLIC-QBC)

For recycling waste batteries, high-gain DC-DC provides a great solution. In this article, the design and optimization of a high-gain converter–synchronous rectification low-inductance current secondary boost converter (SLIC-QBC) is studied. The optimization objective of this article is to propose an automatic design method for passive components and the switching frequency of the converter to improve efficiency and power density. A machine learning-integrated optimization method is proposed to minimize the converter mass and power loss of the converter. In this method, first, a component-based automatic design model is built with embedded SLIC-QBC simulation. Then, a series of design schemes is generated within a large parameter range, and training data for machine learning are collected. Support vector machine (SVM) and artificial neural network (ANN) are used to validate the converter design scheme, where ANN establishes the mapping relationship from design parameters to optimization objectives. After the optimization, an experimental prototype is built for experimental verification. The simulation and experimental results verify the practicability of the proposed method.

Isolated high step‐down DC–DC converter with current‐doubler rectifier for ultracapacitor charger applications

SummaryAn isolated high‐efficiency, high step‐down converter for ultracapacitor charger is presented. The proposed converter utilized the structure of switched inductors and combined the current‐doubler synchronous rectifier, which can reduce the secondary circulating currents. In addition, the energy of the leakage inductance can be recycled to reduce the voltage stresses of the switches. Therefore, the proposed converter can supply the requirement of charging high current, and keep converting high efficiency at the same time. The maximum efficiency of the proposed converter reaches 96.53% at 350 W, and the full load 1 kW is 94.31%, in the case of input voltage 380 V and output voltage 14.6 V. Finally, a 250 F ultracapacitor is charged by the proposed converter from 0 to 14.6 V with constant current (CC) and constant voltage (CV) modes in 1 min. The proposed converters can prove their feasibility by experimental results.

A Novel Synchronous Rectification Scheme With Low Computational Burden for LLC Resonant Converter in EV Charger Applications

In EV charger applications, high voltage level and high computational burden caused by multiple charging modes bring serious challenges to the synchronous rectification (SR) of LLC resonant converter. Conventional SR schemes can be classified as current sensing-based, voltage sensing-based and sensorless, which are limited by high cost of current sensing, difficulty of high voltage sensing, narrow operating range or high computational burden, respectively. To deal with these problems, this paper proposes a novel SR scheme for LLC resonant converter in EV charger applications. In this scheme, SR control signals are tuned only by main control signal, output voltage and output current, which are naturally available from main controller in EV charger. To this end, no additional signal sensing is required and the cost for SR is reduced. Moreover, the SR tuning principle is on the basis of Kirchhoff's law and phase relationship between main control signal and secondary-side current, which no longer needs to calculate complicated models. Meanwhile, the foresaid tuning process of SR control signals can be implemented by analog circuits. With these effects, this scheme can tune SR control signals effectively over a wide operating range with low computational burden. Furthermore, a virtual current injection strategy is designed to suppress the inversion current of synchronous rectifier. It can guarantee no inversion current and low body diode conduction (BDC) loss. A 600-V input 200 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 300-V output LLC prototype converter is built to verify the proposed SR scheme.

Bidirectional Control With Fitting Model-Based Synchronous Rectification and Input Ripple Current Feedforward for SiC Bidirectional CLLC EV Charger

Conventional CLLC Synchronous Rectification (SR) typically adopts detection circuits to sense the high frequency signals. It can hardly be used in the high voltage SiC applications directly as it is sensitive to high dv/dt and may cause false operation. A bidirectional control is proposed for the SiC CLLC charger to achieve the SR function and mitigate the input ripple current. Considering the switching frequency and load, the SR on-time is calculated by the proposed three-order fitting model with low calculation source and high immunity to high dv/dt. Moreover, an input ripple current feedforward control is proposed in the discharging mode, which adds the extracted double line-frequency ripple current to the bus voltage reference. It not only achieves low SR conduction loss, but also reduces the input ripple current largely in the discharge. A 6.6-kW SiC bidirectional CLLC charger was built. Compared to the conventional SR, the CLLC efficiency of proposed SR improves 0.28% at 6.6 kW in the charge. In the discharge, the reduction of CLLC input ripple current at the double line-frequency is up to 91%. The overall charging and discharging efficiencies are 95.4% and 96.1% at full load, respectively.

Transformerless bidirectional switched-inductor switched-capacitor converter

ABSTRACT This research presents a unique bidirectional converter based on the active switched-inductor and switched-capacitor networks of the ASL-SU2C converter. The converter’s primary advantages are its high voltage gain and reduced switch stress. This was accomplished by the converter using three inductors, two switched-capacitors, two switches, and diodes. Switches are used in place of diodes to enable bidirectional power flow in the proposed work, and synchronous rectification is used to boost efficiency by reducing conduction losses. Two inductors and two switches on the low voltage side of the converter aid in lowering the average switch current and, consequently, the current stress. The control operation is made simpler by the fact that two switches on the high voltage side (HVS) have one duty cycle and the other two switches on the low voltage side (LVS) have a different duty cycle. Consequently, two switches will always have identical duty cycles. In order to validate the theoretical findings, the performance of the transformerless bidirectional switched-inductor switched-capacitor (TBSISC) topology is examined in steady state, compared to that of other bidirectional converters, its efficiency is calculated, and experiments with a 500 W prototype are conducted.

Optimized Design Method of RC Damper Based on Modified Negative Conductance Model to Suppress Switching Oscillations in Synchronous Rectifier Circuits With GaN Devices

Optimized Design Method of RC Damper Based on Modified Negative Conductance Model to Suppress Switching Oscillations in Synchronous Rectifier Circuits With GaN Devices