Narrow Variation In Switching Frequency Research Articles

Analysis & Simulation of Different LLC Converter Topologies

There is an expanding trend in electric vehicle (EV) technologies because of finite fuel sourcesand environmental concerns. One of the essential barriers in EVs commercialization is the charging ofbatteries. The inductor-inductor-capacitor (LLC) resonant converter appears the most appealing design dueto its advantages, such as small electromagnetic interference, obtaining high-power density, ability to bedesigned at very high switching frequencies, operation for wide input and output voltage range with narrowswitching frequency variation, and high efficiency. This study compares different topologies of LLCresonant converter that can be adapted as battery charger of electric vehicle. The schematics of topologies,detailed design calculation of the parameters, simulation results of topologies to show the circuitperformance are presented, respectively. The simulation model is realized for whole examined topologieswith a proportional integral controller to obtain constant output voltage using MATLAB. LLC resonantcircuit is designed for the input voltage range of 305-345V, output voltage range of 36-58V, and outputpower of 700W. Analytical and simulation results are included in this study to illustrate the performancedifferences among the presented topologies of LLC resonant converter in terms of structure, efficiency, anddynamic response at sudden load changes.

A New LLSC Series Quasi-Resonant Converter With Narrow Switching Frequency Variation

In this paper, the FHA model including the stray capacitance is analysed. The causes of the voltage gain distortion are studied. Limiting the working frequency is an effective method to solve the voltage gain distortion problem. A new type of the LLSC converter is proposed in the paper. It can regulate the voltage at a constant frequency. At the same time, the soft switch can be realized if the parameter design is reasonable. The proposed converter can overcome the voltage gain distortion problem and obtain the high efficiency at the light load condition. Some mathematical analyses are used to prove that the proposed converter can avoid the voltage gain distortion problems. The simulation and experimental results based on a 200W LLSC converter prototype confirm the correctness of the topology.

A Boost PFC Stage Utilized as Half-Bridge Converter for High-Efficiency DC–DC Stage in Power Supply Unit

The half-bridge (HB) LLC converter is one of the most attractive dc–dc converters for medium power supplies due to its soft switching capability. However, its conversion efficiency is considerably degraded in wide-link-voltage applications because of a small magnetizing inductance and wide switching frequency variation for a high voltage gain. In this paper, a boost power factor correction (PFC) stage, which can also play an important role during the hold-up time, is proposed for a high-efficiency HB LLC converter. In the proposed PFC stage, the boost PFC converter can be effectively utilized as a HB converter by replacing a boost diode and inductor with a synchronous switch and transformer, respectively. After the ac line is lost, the proposed PFC stage can operate as the HB converter and regulate the output voltage instead of the HB LLC converter. Thus, it enables the HB LLC converter to be designed with a large magnetizing inductance and narrow switching frequency variation. As a result, the proposed PFC stage can enhance the overall efficiency of the PSU by improving the efficiency of the HB LLC converter. To confirm the validity of this paper, a prototype with 180–264-Vrms ac line, 250–400-V link voltage, and 48 V/480 W output is tested.

PWM–PFM hybrid controlled LCC resonant converter with wide ZVS range and narrow switching frequency variation

Variable frequency controlled LCC resonant converter suffers from wide variation of switching frequency. Although fixed frequency controlled LCC resonant converter benefits from constant switching frequency, it suffers from narrow zero voltage switching (ZVS) range of power switch and high circulating energy. A pulse width modulation – pulse frequency modulation (PWM-PFM) hybrid controlled LCC resonant converter is proposed to achieve wide ZVS range of power switch with narrow variation of switching frequency. Experiment results of a 500 W prototype are provided to verify theoretical analysis of the proposed converter.

A New LLC Series Resonant Converter with a Narrow Switching Frequency Variation and Reduced Conduction Losses

A new LLC series resonant converter that has a narrow switching frequency variation and reduced conduction losses is proposed in this paper. In the proposed converter, one leg of the full-bridge diode rectifier is replaced with synchronous rectifier (SR) switches. In the nominal state, the proposed converter is controlled using frequency modulation, and the SR switches are controlled using in-phase switching signals with primary side switches in order that the proposed converter can obtain a reduced conduction loss in its secondary side rectifiers. During the hold-up time which is the condition where the input voltage of the converter decreases, the SR switches are controlled using phase-shifted switching signals in order that the proposed converter can obtain a higher gain without decreasing the switching frequency. Because the proposed converter operates with a narrow switching frequency variation, a small transformer core can be selected, which results in a decreased core size and loss. Furthermore, it is possible for the proposed converter to be designed optimally in the nominal state and this results in the proposed converter exhibiting a maximized efficiency over the entire load condition. The feasibility of the proposed converter is verified with a 400-250 V input and 200 V/1.5 A output prototype.

High-power-factor operation of three-phase AC-to-DC resonant converter

Analysis and design of a three-phase AC-to-DC resonant converter is considered. The power factor of the three-phase AC input line diode bridge rectifier is improved by injecting high-frequency current. The three-phase AC-to-DC resonant converter is operated at frequencies above the resonant frequency. The analysis of the converter is carried out using different operating modes in one switching cycle of the resonant inverter. The design of the AC-to-DC resonant converter is discussed step by step. An experimental prototype of a 3 kW, 500 V output power and operating above 300 kHz has been developed in the laboratory. The proposed three-phase AC-to-DC resonant converter has high power factor, low total harmonic distortion and high efficiency. It requires narrow variation in switching frequency to regulate the output voltage

Novel single-phase AC-to-DC convertor using three-phase modified series–parallel resonant convertor

The paper deals with a single-phase AC-to-DC convertor using a three-phase modified series–parallel resonant convertor. A systematic procedure is presented for the design of three-phase resonant-convertor components. Based on the analysis and design curves, a resonant convertor is designed for 2.5 kW rating. The minimum switching frequency of the convertor is 290 kHz at full-load condition. The simulation and experimental results are presented for variable-load conditions. The variable frequency and duty-ratio control scheme are implemented using a digital signal processor for output-voltage regulation. The use of a three-phase high-frequency invertor reduces the filtering requirements, peak component stresses on the resonant components and peak invertor output current. The proposed convertor maintains excellent input-line power factor without any active control of AC-input line current. Apart from this, it requires narrow variation in switching frequency for its output-voltage regulation.

A three-phase series-parallel resonant converter-analysis, design, simulation, and experimental results

A three-phase DC-to-DC series-parallel resonant converter is proposed and its operating modes for a 180/spl deg/ wide gating pulse scheme are explained. A detailed analysis of the converter using a constant current model and the Fourier series approach is presented. Based on the analysis, design curves are obtained and a design example of a 1-kW converter is given. SPICE simulation results for the designed converter and experimental results for a 500-W converter are presented to verify the performance of the proposed converter for varying load conditions. The converter operates in lagging power factor (PF) mode for the entire load range and requires a narrow variation in switching frequency, to adequately regulate the output power.

Analysis and design of LCL-type series resonant converter

A series resonant converter modified by adding an inductor in parallel with the transformer primary (or secondary) is presented. This configuration is referred to as an LCL-type series resonant converter. A simplified steady-state analysis using complex AC circuit analysis is presented. Based on the analysis, a simple design procedure is given. Detailed experimental results obtained from a MOSFET-based 640 W converter are presented to verify the analysis. A narrow variation in switching frequency is required to regulate the output voltage for a very wide change in load, and the converter has load short-circuit capability. It is shown that by placing the parallel inductor on the secondary side, the parasitics of the high-frequency transformer can be used profitably. >

Analysis and design of a modified series resonant converter

A modified series resonant converter (SRC) (also referred to as the LCL-type SRC) which overcomes the problems of the standard series resonant converter is presented. A state-space approach is used for the analysis. Analysis shows that the converter enters into three different modes. Converter gain and other component stresses are plotted with variation in the load current. Detailed experimental results obtained from a 500 W MOSFET converter are presented to verify the theory. With a proper selection of inductor ratio, only a narrow variation in switching frequency is required to regulate the output voltage for wide variation in the load current. It is shown that, by placing the parallel inductor on the secondary side, the parasitics of the high-frequency transformer can be used profitably. >