A new design strategy for DC/DC LLC resonant converter: Concept, modeling, and fabrication

Zhu

et al. 2023

Circuit Theory & Apps

SummaryResonant converters have been widely applied in many fields, such as electric vehicles, renewable energy sources, and switch‐mode power supply. Conventional resonant converters generally adopt pulse frequency modulation (PFM), which would cause an extremely wide frequency variation range under wide output applications. However, it would lead to high electromagnetic interference (EMI), low utilization of magnetic components, and loss of soft switching features. For catering to wide output range applications, this paper proposes a self‐adaptive narrow frequency range PFM and asymmetrical voltage‐cancelation hybrid modulation strategy to solve the above problem. The advantages of the proposed strategy include (1) narrow frequency variation range; (2) self‐adaptive shift frequency; and (3) full process achievement of zero voltage switch. The modulation strategy and operational principle and performance analysis of the proposed method are given. Eventually, a series resonant converters–based experimental platform was implemented to verify the proposed strategy.

Section: Fixed-frequency Modulationmentioning

confidence: 99%

“…The waveform diagrams of three fixed‐frequency modulation methods, which are mentioned in Khosrogorji et al, 9 are shown in Figure 2. Each modulation strategy has a control angle α .…”

Section: Proposed Pfm and Avc Modulation Strategymentioning

confidence: 99%

({, \begin{array}{l} M_{italicPS, italicADC} goodbreak= \frac{{italicnV}_{o}}{V_{italicin}} goodbreak= \frac{\cos ((), \frac{α}{2})}{\sqrt{1 + Q^{2} {((), ω_{n} goodbreak- \frac{1}{ω_{n}})}^{2}}} \\ M_{AVC} goodbreak= \frac{{italicnV}_{o}}{V_{italicin}} goodbreak= \frac{\sqrt{10 + 6 \cos α}}{4 \sqrt{1 + Q^{2} {(ω_{n} - \frac{1}{ω_{n}})}^{2}}} \end{array}),

where the quality factor Q , the equivalent resistance, the normalized switching frequency ω n , and the natural resonant frequency ω 0 of the converter are expressed as

({, \begin{array}{l} Q goodbreak= \sqrt{\frac{L_{r}}{C_{r}}} \frac{1}{R_{italiceq}}, R_{eq} goodbreak= \frac{8 n^{2} R_{0}}{π^{2}} \\ ω_{n} goodbreak= \frac{ω_{s}}{ω_{0}}, ω_{0} goodbreak= \frac{1}{\sqrt{L_{r} C_{r}}} \end{array}) .

…”

Section: Proposed Pfm and Avc Modulation Strategymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Frequency‐adapted hybrid modulation strategy of resonant converter with narrow frequency range

Zhu

et al. 2023

Circuit Theory & Apps

“…However, they are not recommended for high power application owing to high switch stress and lack of galvanic isolation. Among isolated battery charging topologies, many converters adopt the full bridge (FB) structure and its variants [8]. A hybrid FB converter integrated with a half-bridge (HB) structure or another FB structure on the primary side is presented in [9,10] where the reduction of conduction loss is realized due to the reduction of circulating current.…”

Section: Introductionmentioning

confidence: 99%

Constant-Current, Constant-Voltage Operation of a Dual-Bridge Resonant Converter: Modulation, Design and Experimental Results

Zhou

et al. 2021

Applied Sciences

To meet the requirements of charging the mainstream rechargeable batteries, in this work, a dual-bridge resonant converter (DBRC) is operated as a battery charger. Thanks to the features of this topology, the required high efficiency can be achieved with a wide range of battery voltage and current by using different modulation variables. Firstly, a typical charging process including constant-voltage stage and constant-current stage is indicated. Then, two different modulation methods of the DBRC are proposed, both of which can realize constant-voltage charging and constant-current charging. Method I adopts phase-shift modulation with constant switching frequency while Method II adopts varying frequency modulation. Furthermore, as guidance for practical application, the design principles and detailed design procedures of the DBRC are customized for the two modulation methods respectively in order to reduce the switching loss and conduction loss. Consequently, the full soft-switching operation with low rms tank current is achieved under the two modulation methods, which contributes to the high efficiency of the whole charging process. At last extensive simulation and experimental tests on a lab prototype converter are performed, which prove the feasibility and effectiveness of the proposed modulation strategies.

Adaptive droop control strategy of parallel LLC converters

Tang,

Xu,

Pei

et al. 2023

Circuit Theory & Apps

When the resonant converters are connected in parallel, the output current is unbalanced without additional current‐sharing measures due to differences in resonant component. In the input‐parallel output‐parallel resonant converter system, the output voltage accuracy of the converter under the traditional droop control is analyzed when the load changes. In this paper, an adaptive droop control is proposed, in which the droop coefficient is adaptively adjusted as the load changes. The control method proposed in this paper realizes the current sharing between the converters and solves the shortcomings of the output voltage changing under different loads in the conventional droop control. Taking two parallel LLC converters as an example, the control block diagram of the parallel control method for adaptive adjustment of the droop coefficient proposed in this paper is given, and the stability of the control loop is analyzed. Finally, two parallel prototypes of LLC converters with input 200 V/output 24 V input are built by digital control, and the experiment shows that the proposed control method improves the shortcomings of excessive output voltage droop caused by traditional droop control during dynamic load switching, which verifies the effectiveness of the method.