Performance Characteristics of LLC Resonant Converter Using Modified Digital Filter

Inhalt:
LLC resonant converter has been widely used for various applications because of its high efficiency characteristics. In previous study, the digital control method using modified digital filter was proposed. The modified digital filter consists of a proportional-differential control and a FIR filter. It is confirmed that the proposed control method using modified digital filter achieves superior transient response with simulation. This paper discusses the steady state and dynamic characteristics of digital control LLC resonant converter using the modified FIR filter. Although digital filters are used to achieve desired droop characteristics in output current-output voltage characteristics, its dynamic characteristics are inferior to P-I-D control. The FIR filter is combined with the pro-portional-differential calculator. The purpose of the proposed method is to improve the dynamic response while obtain-ing a desired droop characteristic. It is confirmed that the switching frequency variation of LLC resonant converter is two-third of that of P-I-D Control while obtaining voltage droop characteristics. Also the transient response is superior to the FIR control method, which is experimentally verified with 48V/5V prototype.