A Variable Duty Cycle Soft Startup Strategy for &lt;italic&gt;LLC&lt;/italic&gt; Series Resonant Converter Based on Optimal Current-Limiting Curve

Yang, Dongdong; Chen, Changsong; Duan, Shanxu; Cai, Jiuqing; Xiao, Liangle

doi:10.1109/tpel.2016.2514399

Cited by 35 publications

(13 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…D ESPITE the nonlinear properties of the duty-cycle modulation in LLC converters [1]- [3], this method has become a popular and well-established solution for several specific tasks. In variable-voltage applications, the duty-cycle modulation was proposed several times for light-load efficiency optimization [4]- [6].…”

Section: Introductionmentioning

confidence: 99%

“…In dc transformer applications of LLC converter (DCX applications), where the voltage transfer ratio is fixed, the duty-cycle modulation can be utilized as a protection method. While these converters are usually operated in open-loop operation near resonant frequency with a constant duty cycle of δ = 0.5, the duty-cycle modulation is an effective measure to limit the transferred currents either during start-up of the converter [2], [3], [7] or during overload conditions [7]- [9]. Compared to the hardware-based methods for current limiting, such as application of clamping diodes [10], [11] or an additional resistor in the resonant tank [9], the dutycycle modulation does not require any modification of the converter, which results in reduced costs and converter size.…”

Section: Introductionmentioning

confidence: 99%

“…In the literature, two modulation techniques were proposed for the H-bridge LLC converters: duty-cycle method that uses only one zero-voltage state [3], and the phase-shift modulation [2]- [4], [6]- [8]. While they generate the same three-level voltage waveforms at the resonant tank, the distribution of the losses between the switches is not only different (due to the different utilization of zero states) but also unequal in both cases.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Equal Loss Distribution in Duty-Cycle Controlled H-Bridge LLC Resonant Converters

Kucka

Dujić

2021

IEEE Trans. Power Electron.

View full text Add to dashboard Cite

The duty-cycle control is a popular option for current limiting in LLC resonant converters. Such current limiting is required to protect the converter either during the start-up or during an overload. Although this method proved to be effective, the switching and conduction losses of the converter are increased because of the modified current waveforms in the resonant tank. Hence, for the safe operation, it is vital to distribute the losses between the switches symmetrically. However, the conventional duty-cycle or phase-shift modulation methods do not provide this naturally. This letter elaborates on a method that was proposed for a different soft-switching topology more than a decade ago to solve this problem, and is adaptable for the emerging dc transformers. Furthermore, a simple implementation of the method is shown and the equal distribution of losses is validated experimentally. The VHDL code with the implementation of the modulator is attached to this paper available openly for reuse.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Equal Loss Distribution in Duty-Cycle Controlled H-Bridge LLC Resonant Converters

Kucka

Dujić

2021

IEEE Trans. Power Electron.

View full text Add to dashboard Cite

show abstract

“…The RMS value of current flowing through the secondary diodes have been reduced in [24] , however, several control modes are required to regulate the converter at rated voltage. Recently, pulse-width or duty cycle modulation are gaining interest for wide gain range [25,26], enhanced light load efficiency [27,28] and suppressed inrush current [29]. The output can be well-regulated by adding a duty cycle in the input of the resonant tank and no loss of ZVS occurs in case of duty control at any load condition.…”

Section: Introductionmentioning

confidence: 99%

Circuit Topology and Small Signal Modeling of Variable Duty Cycle Controlled Three-Level LLC Converter

et al. 2019

View full text Add to dashboard Cite

With a view to regulate the output voltage with fixed frequency, without using any additional component or complex modulation technique, a topology of a variable duty controlled three-level LLC converter is proposed and an equivalent small signal model for Electric Vehicle (EV) charger applications is deduced in this paper. The steady state equations of each operating region are derived in time domain. Based on an Extended Describing Function (EDF) approach, a small signal equivalent circuit is modeled which includes both frequency and duty controlled terms. The equivalent circuit is further simplified to derive a transfer function of duty control to output voltage. The transfer function is verified through simulation software. Analyzing the transfer function, a voltage controller is designed and implemented with a PI compensator. The simulation results of the proposed control schemes are illustrated and discussed. The topology is compared to a conventional frequency control topology and the merits of the proposed topology are presented.

show abstract

“…However, it is benefit when the complexity of state variables is reduced. In [ 37 ], resonant variables and output voltage can be predicted by numerical equations during the startup process. Furthermore, the relationships between startup current, initial startup frequency, and duty cycle are presented.…”

Section: Introductionmentioning

confidence: 99%

An improved large signal model of full-bridge LLC converter

Yao

Liu

2018

PLoS ONE

View full text Add to dashboard Cite

For the full-bridge LLC converter, it is necessary to establish a large signal model with low-complexity and high-precision when the current of filter inductor works under the continuous conduction mode (CCM) situation. In terms of low complexity, peak values of resonant state variables and average values of slow state variables are taken as the measured indexes between models and actual converter. Models based on the first harmonic approximation (FHA) are studied in depth because they have lower complexity than the existing models. From prospective of high precision, deficiencies of typical FHA model are explained in the light of harmonic generation mechanism of primary current and influence of Fourier series on the typical equivalent circuit. Therefore, transient process of each metallic oxide semiconductor field effect transistor (MOSFET) and its related fast recovery diode, transient process of Schottky rectifier diodes, piecewise equivalent circuit, appropriate selection of variables, and simplified modified dynamic equations are all considered. Furthermore, the unified proposed model is achieved according to the equivalent principle of indexes between aforementioned improved analyses and proposed model. Numerical results of typical FHA model and proposed model are given in accordance with the key indexes. Then, corresponding experimental results are also presented. Differences of indexes between the two models and the actual converter are compared respectively. Though complexity of proposed model is the same as that of typical FHA model, precision of proposed model is higher than that of typical FHA model.

show abstract

A Variable Duty Cycle Soft Startup Strategy for <italic>LLC</italic> Series Resonant Converter Based on Optimal Current-Limiting Curve

Cited by 35 publications

References 14 publications

Equal Loss Distribution in Duty-Cycle Controlled H-Bridge LLC Resonant Converters

Equal Loss Distribution in Duty-Cycle Controlled H-Bridge LLC Resonant Converters

Circuit Topology and Small Signal Modeling of Variable Duty Cycle Controlled Three-Level LLC Converter

An improved large signal model of full-bridge LLC converter

Contact Info

Product

Resources

About