High-Frequency <italic>LLC</italic> Resonant Converter With Magnetic Shunt Integrated Planar Transformer

Abstract

Achieving high efficiency and high power density is emerging as a goal in many power electronics applications. LLC resonant converter has been proved as an excellent candidate to achieve this goal. To achieve smaller size of passive components, the resonant inductor in the LLC converter is usually integrated into the transformer by utilizing its leakage inductance. However, the leakage inductance of transformer is usually insufficient and thus the LLC converter has to be operated in a limited frequency range (this limits the input voltage range accordingly), otherwise the power efficiency will drop dramatically. Therefore, a larger resonant inductance in the LLC converter is expected to operate in a wider input voltage range. This paper proposes a new method to create a larger resonant inductance by using a magnetic shunt integrated into planar windings. The accurate leakage inductance modelling, calculation and optimal design guideline for LLC planar transformer, including optimal magnetic shunt selection and winding layout, are presented. A 280-380V input and output 48V-100W half bridge LLC resonant converter with 1MHz resonant frequency is built to verify the design methodology. A comparison is made between two converters with the same parameters, one using magnetic shunt integrated transformer and the others using traditional planar transformer and external inductor. Experimental result shows the proposed converter with magnetic shunt is capable to achieve comparable high efficiency and regulation capability with the other under a wide input voltage, which verify the optimal design methodology. Above all, this magnetics integration methodology reduces the whole converter's volume and thus increases the power density. Index Terms-magnetic shunt, LLC resonant converter, planar transformer, high frequency, wide input voltage.

Conceptualization and Analysis of a Next-Generation Ultra-Compact 1.5-kW PCB-Integrated Wide-Input-Voltage-Range 12V-Output Industrial DC/DC Converter Module

“…Figure12. Key operating waveforms captured at (a) nominal and (b) 50 % load, demonstrating good agreement with circuit-simulation data (shown as dashed lines).…”

“…Buck-based topologies support a wide-input-voltage range, but are hard-switched (over at least part of the regime) and therefore have low efficiency [8][9][10][11]. LLC-based converters are soft-switched with high efficiencies even at high switching frequencies, but are limited by a narrow input voltage range [12][13][14][15][16][17] that, in this application, would result in an unreasonablylarge DC-link capacitor to meet hold-up specifications. At the extreme of narrow input voltage ranges, DC transformers ("DCX") with a fixed voltage conversion ratio require, at a minimum, a differential-power pre-regulation stage [5].…”

“…The only prior art with a wide-input range, soft-switching over the complete range, and high-current output with PCB-integrated magnetics has either a maximum efficiency of only 93 % [18] or low power density when the necessary passives are included [19] ( [19] also features lower output current, which is simpler to PCB-integrate). Finally, designs with higher output voltages (e.g., V o = 48 V [12,13,20]) are much simpler to PCB integrate (with 16× lower conduction losses on the secondary side) but do not meet the entrenched and ubiquitous 12 V buses that currently dominate industrial applications.…”

Parameters Optimization of an Intermediate Frequency Isolated SiC Power DC-DC Converter

“…Since fs is very close to fr, the operating characteristics of the LLC converter are analyzed using the fundamental-wave approximation [12,13], and the normalized voltage gain M of the converter and the input impedance Zin,AB of the resonant network are obtained as…”

“…From (12), it can be seen that the voltage gain of the converter is influenced by the resonance parameter, the switching frequency, and the load at the same time. Fig.…”