Synchronous Rectification Control Research Articles

Predictive Synchronous Rectification Control Scheme for Resonant DC–DC Converters for Battery Charging and Telecom Application

Predictive Synchronous Rectification Control Scheme for Resonant DC–DC Converters for Battery Charging and Telecom Application

A bidirectional resonant CLLC converter combining three‐level characteristic and bipolar DC structure

SummaryIn order to meet the efficient and convenient usage requirements for bidirectional DC‐DC converters in some fields such as DC microgrids and vehicle power conversion systems, a bidirectional resonant CLLC converter combining three‐level characteristic and bipolar DC structure is used and analyzed in this paper. A three‐level topology is adopted in the resonant CLLC converter, which can achieve stable and wider range voltage regulation through the frequency adjustment combined with duty cycle and phase shift modulation, and can also increase the flexibility of control strategy. The application of bipolar DC structure enables this resonant CLLC converter to have multi‐port on one side, and the method of using two interleaved inductors combined with synchronous rectification enables the output voltage of the converter to maintain a certain balance. In this paper, the voltage gains and running states of the three‐level regulation method are analyzed, and then these operation modes and the bipolar DC voltage balance effect of the converter under synchronous rectification control are verified by the experiment results.

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 novel digital sensor-less synchronous rectification method for CLLLC resonant converters

With the rapid development of the renewable energy vehicles, pursuing the power converters with high efficiency and high reliability has caught more attention recently. In order to solve those problem with low cost, this paper proposes a sensor-less synchronous rectification method for the CLLLC resonant converters. The precise conduction time of the synchronous switches is obtained based on the analysis of the working principle of CLLLC resonant converter, and the relationship between the SRs switching time and the inverter switching time can be derived as well. To achieve the wide output voltage range, the converter requires wide working frequency. And the correct turn-on and turn-off time for the synchronous switches can be obtained respectively by calculation and piecewise linear function fitting methods within full working frequency range. Compared with traditional synchronous rectification control for CLLLC, which require additional high bandwidth voltage sensors or current sensors, the method proposed in this paper is realized by only one low-cost output voltage sensor. And the proposed method is suitable for high-power applications with a wide voltage and load variation. Moreover, because of the symmetrical topology, this method is valid in bidirectional power transfer. Additionally, the exist analog synchronous rectification control chips suffer from losing accuracy with wide bus voltage variation, however, this method can overcome this shortcoming. Thus, the proposed synchronous rectification method is a low-cost and suitable for high-power, high power density, high efficiency application which benefit from its simple algorithm. Finally, the proposed sensor-less synchronous rectification method is validated by the simulation results and experimental results. The results of simulation and experimental have shown the proposed method offers significant benefits which increases the efficiency of the whole CLLLC system by about 3%, and the reliability of the converter are greatly increased, due to the cooler SRs.

Synchronous rectification control method of AC/DC converters based on the response surface algorithm

Synchronous rectification control method of AC/DC converters based on the response surface algorithm

Synchronous rectification control method of AC/DC converters based on the response surface algorithm

In order to improve the stability and anti-interference ability of synchronous rectification control of AC/DC converter, a synchronous rectification control method of AC/DC converter based on response surface algorithm is proposed. A high speed and low power comparator is designed to compare input and output signals. The AC/DC converter optimisation model is constructed by response surface algorithm. Logic control is implemented through synchronous rectification logic and synchronous rectification control. The control part of power supply and drive AC/DC converter is designed to realise the synchronous rectification control of AC/DC converter. The performance of synchronous rectifier control of AC/DC converter under the application of the proposed method was tested. The test results show that the output waveform of the converter trigger pulse is very stable and regular. It has good phase shifting characteristic; the method has strong anti-interference ability and achieves the original design goal.

A 10 MHz DC/DC Converter With Zero-Phase Difference Synchronous Driving Signal

In this article, a 10 MHz dc/dc converter based on three-dimensional air core transformer with zero-phase difference synchronous driving signals is designed. By using the characteristics of no leakage inductance in the inner winding of the nested toroidal air core transformer, the phase difference between the output voltage of the inverter and the input voltage of the rectifier can be regarded as zero, so that the rectifier and the inverter can use the same driving signal, which simplifies the control of the synchronous rectifier switches, and realizes the reliable and efficient synchronous rectification control at 10 MHz. The prototypes with primary and secondary compensation are proposed and the experimental results verify the feasibility of the proposed control method and numerical design method.

Application of the Lyapunov Algorithm to Optimize the Control Strategy of Low-Voltage and High-Current Synchronous DC Generator Systems

In the present study, a novel multiple three-phase low-voltage and high-current permanent magnet synchronous generation system is proposed, which has only half-turn coils per phase. The proposed system is composed of a generator and two confluence plates with 108 rectifier modules. The output can reach up to 10,000 A continuous DC power supply, which is suitable for the outdoors and non-commercial power supply. The application of the Lyapunov algorithm in the synchronous rectification control was optimized. A current sharing loop control was added to the closed-loop control to ensure a stable output voltage and the output current sharing of each rectifier module. Since the two control variables solved by the Lyapunov algorithm were coupled and the negative definite function of the Lyapunov algorithm could not be guaranteed in this system, a simple decoupling method was used to decouple the control variables. Compared to the conventional control, the proposed strategy highly improved the dynamic performance of the system. The effectiveness of the proposed strategy was verified by the simulation. The 5 V/10,000 A hardware experiment platform was built, which proved the feasibility and validity of the proposed strategy for a high-power generation system.

Synchronous Rectification of LLC Resonant Converters Using Homopolarity Cycle Modulation

In order to further reduce losses in LLC resonant converters, the use of synchronous rectifiers (SRs) in the output rectifier is desirable. Analysis and detection of the conduction angles of the SRs used in an LLC converter are the main challenges in synchronous rectification. This paper develops a new time-domain theoretical analysis, called homopolarity cycle, enabling synchronous rectification in LLC resonant converters with the use of a low-cost polarity-based sensing technique. The homopolarity cycle considerably reduces the complexity of the LLC converter's analysis, relates the conduction angles of the SRs to the gate driving signals of the inverter switches and the polarity of the rectifier voltage, and finally introduces a low-cost polarity-based sensing technique. A synchronous rectification control algorithm, called homopolarity cycle modulation (HCM), is proposed, which only needs to sense the polarity of the rectifier voltage, which is simple to measure and immune to noise. A simple graphical plane, named the homopolarity, is introduced to provide information about the SRs’ conduction angles. The proposed HCM method is validated by experimental and simulation results. Unlike the conventional synchronous rectification technique, the results have shown that the proposed HCM synchronous rectification method has a flat synchronous rectification coverage from light to full loading conditions while using a simple sensing strategy.

Design of a 2.5-kW 400/12-V High-Efficiency DC/DC Converter Using a Novel Synchronous Rectification Control for Electric Vehicles

This paper proposes the design of a 2.5-kW 400/12 V high-efficiency isolated dc/dc converter for electric vehicles. The designed system accommodates the wide-range input voltage (450 V–220 VDC) and output voltage (16 V–6 VDC). An LLC half-bridge topology is adopted as the primary side of the dc/dc converter. For the secondary side, a novel synchronous rectification control (SRC) strategy is developed to switch metal oxide semiconductor field effect transistors (MOSFETs) through accurately tracking the target switching moments. Experimental results were carried out to charge the on-board 12-V battery and validate the proposed control algorithm. The maximum system efficiency is 93.2%. System power loss is also itemized.

A Switching-Capacitor PWM DC–DC Converter and Its Variations

This paper proposes a novel switching-capacitor pulsewidth modulation (PWM) converter. The converter is a combination of a switching-capacitor converter and a PWM converter, and it has the following advantages: 1) zero-voltage switching of all the MOSFETs; 2) with an autotransformer self-driven method, there is no need to adjust the synchronous rectifier control timing, and this reduces body diode conduction loss; 3) its efficiency is not sensitive to the leakage inductor, so a discrete transformer can be used, and it is suitable for both voltage regulator module (VRM) and voltage regulator down (VRD) application; and 4) a single-phase option makes it more flexible, and it can achieve higher efficiency in the whole load range with a phase-shedding control strategy. A 700-kHz 1.2-V/35-A POL prototype and a four-phase 700-kHz 1.2-V/130-A-output VRM prototype were built to verify the analysis.