Modified Dynamic Time Domain Model for LLC Resonant Converter by Considering Parasitics and Various Modulation Strategies

To improve LLC resonant converters' performances in wide voltage range applications, many novel modulation strategies that are different from the conventional pulse frequency modulation (PFM) are proposed, such as phase-shift modulation and pulse width modulation. However, the existing LLC modeling methods are difficult to consider different modulation strategies. In addition, in most cases, the traditional time domain models are developed based on the assumption of ideal components. However, in practical applications, circuit parasitics have great influence on the modeling process. In this article, an accurate time domain model by considering common parasitics and suitable for different modulation strategies is developed. The idea of the proposed method is based on the iteration of different operation stages. Once the possible stages are solved and stage switching conditions are determined, the modeling of LLC with various modulation strategies can be achieved. The experimental results show that the error of the proposed model can be reduced from 8.1% to 3% when compared with the traditional time domain model.