LLC Converter Design Research Articles

Optimal LLC Converter Design with Topology Morphing Control for Wide Voltage Range Battery Charging Applications

Optimal LLC Converter Design with Topology Morphing Control for Wide Voltage Range Battery Charging Applications

Performance Comparison Analysis of a High Voltage DC LLC Resonant Converter for Telecom and Datacenter Applications

Intermediate Bus Architecture (IBA) is used for power distribution in information communication technology (ICT) equipment due to the flexibility of its power distribution and cost-effectiveness compared to centralized or DC-mediated power. The reason for IBA's good performance in this context is its greater reliability and efficient Intermediate Bus Converter (IBC). Existing IBAs comprise low-voltage systems with multiple power, resulting in power loss. This study outlines the need for a high-voltage DC-to-DC converter to solve the problems associated with conventional 48 VDC converters. A 300 W LLC series resonant converter is utilized for the design and analysis of converter efficiency and losses across various input voltages. The results indicate that the maximum converter efficiency is >92% at full load. MATHCAD is used to analyze the performance of the LLC converter and understand the suitable operating zones for zero-voltage-switching. The LLC converter's efficiency is investigated for multiple input voltage ranges. The LLC converter is designed and developed in MATLAB and the results of the simulation are presented. Trade-offs in the LLC converter's design are also discussed, with the goal of operating the converter in an optimal manner and achieving the maximum possible efficiency.

A New Optimization Method for Gapped and Distributed Core Magnetics in LLC Converter

LLC converter design optimization remains a challenging task for varying loads such as in battery chargers. There are numerous L-L-C combinations to choose from a design space that can satisfy the required voltage gains of the application. An accurate magnetic model is essential to optimally size the passive components according to the application needs. This paper provides a new design tool for gapped core magnetics to optimize the transformer and resonant inductor in LLC converters. Unlike conventional design algorithms, the proposed algorithm considers multiple distributed cores and selects the optimal magnetic flux density by minimizing a penalty function that includes power loss, cost and volume of the magnetic components using Big-Bang Big-Crunch Algorithm. The gapped core transformer and inductor design equations have been verified in Ansys Maxwell and Simplorer co-simulation environment for a 3700W 48V LLC and calculated power loss have been compared with experimental results. For the given L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> pair of 37.52 μH and 9.38 μH, the proposed magnetic model designed a transformer with two-distributed cores, each one exhibiting a magnetizing inductance of 17.73 μH and leakage inductance of 0.7 μH on a EE422120 with 3F36 material. The total power loss of the transformers are measured as 12.44 W on a 3700 W prototype switched at 350 kHz.

Analysis and Design of the LLC LED Driver Based on State-Space Representation Direct Time-Domain Solution

The LLC resonant converter has been widely used in switched power supply covering several kinds of applications. Although it has been the focus of numerous analysis, their general time-domain (TD) solution is not completely enclosed due to its complexity given by the multiple resonance nature and its variable structure behavior. Consequently, the LLC converter design is also impaired by the lack of an enclosed TD solution. To overcome these issues, this article systematically presents a highly accurate TD solution of the LLC converter supplying a light-emitting diode (LED) load, which is obtained from the state-space representation direct TD solution. Dissimilar to preceding analyses, all the converter states are considered and no current and voltage sinusoidal or average value approximations are taken. Finally, supported by the TD analysis, a new LLC LED driver design procedure is introduced, which is oriented by weighted-average-efficiency concept and constraints that ensure zero voltage switching, enough power gain, and practical switching frequency range over a wide operating window. Experimental results show the feasibility of the proposed design procedure as well as the accurate TD behavior prediction of the LLC converter supplying an LED load. This article is accompanied by active content that exemplifies the proposed TD solution and design procedure.

Design Considerations of Series-Connected Devices Based LLC Converter

This paper describes the design of a Series-Connected Device based on a fixed–frequency LLC resonant converter (SCDLLC). Isolation of the dc-dc converter like the LLC resonant converter is used for the stability of the high voltage system such as a solid-state-transformer (SST). The series-connected devices driving method is one of the methods applicable to a high voltage system. When driving series-connected devices, an auxiliary circuit for voltage balancing between series-connected devices is required, which can be simply implemented using a passive element. In this paper, LLC converter design with balancing circuits configured in parallel with a device is provided, and both the simulations and experiments were performed.

Low-Loss Integrated Inductor and Transformer Structure and Application in Regulated LLC Converter for 48-V Bus Converter

In this article, an LLC converter using gallium nitride (GaN) transistors is proposed for a 48-V regulated and isolated bus converter. Compared with pulsewidth modulation (PWM)-based topologies, the soft switching capability of an LLC allows operation at very high frequencies. In addition, the size of the magnetic components is reduced without sacrificing the efficiency. In this article, a novel magnetic structure that integrates a matrix transformer and inductor with minimum winding and a single magnetic core is proposed, to allow a high-density and high-efficiency LLC converter design for a bus converter. A 40—60-V input and regulated 12-V output converter is developed to deliver a 1-kW output power in a quarter brick form factor. The designed converter can achieve a power density of 700 W/in3 with a maximum efficiency of 97.82% at half-load, dropping to 97.7% at full-load operation.

Virtual prototype and GaN HEMT based high frequency LLC converter design

Gallium nitride (GaN) high-electron-mobility transistor (HEMT) with the merits of the fast switch speed, low on resistance and low switch loss is applicable to high-frequency LLC converters. However, voltage stress and ringing problems during the fast switching transient have retarded the promotion of switch speed and prolonged the design cycles. This study proposed an economic and time-saving virtual prototype based LLC converter design method, based on which the voltage stress and ringing problem can be analysed and suppressed by iteration design. The virtual prototype comprises of compact GaN HEMT device model and accurate circuit model. The correctness and effectiveness of the virtual-prototype-based design method is verified with well matching simulation and experiment waveforms.

Short‐circuit protection of LLC resonant converter using voltages across resonant tank elements

This paper describes two methods for the short-circuit protection of the LLC resonant converter. One of them uses the voltage across the capacitor and the other uses the voltage across the inductor of the resonant tank. These voltages can be processed (integrated or differentiated) to recover the resonant tank current. The two circuits illustrated in the described methods make it possible to develop a robust LLC converter design and to avoid using lossy current measurement elements, such as a shunt resistor or current transformer. The methods also allow measuring resonant tank current without breaking high-current paths and connecting the measuring circuit in parallel with the inductor or capacitor of the resonant tank. Practical implementations of these indirect current measurements have been experimentally tested for the short-circuit protection of the 1600 W LLC converter.

Modeling and Design of High Power Half-Bridge LLC Resonant Converter

ntroduction was made to the working principle of topology for the half-bridge LLC resonant converter. Steady-state models of the high power LLC resonant network were researched. The high power half-bridge LLC converter was modeled and analyzed with First Harmonic Approach so as to obtain the optimal parameters. The turn ration of the converter was selected. The resonant inductance, resonant capacitance and excitation inductance were designed. The feasibility of the high power LLC converter design has been verified through simulation.

Approximate Analysis of Resonant LLC DC-DC Converter

This paper presents an approximate analysis of LLC resonant converter with capacitive filter operating above and below resonance. An equivalent ac resistance model of the rectifier valid for discontinuous as well as continuous conduction modes is proposed. The dc voltage conversion ratio is then obtained using the fundamental harmonic approximation analysis method. Based on the analysis, LLC converter design plots and guidelines are suggested. The theory is verified by simulation and experiment.