A novel small signal modeling of series resonant converter based on peak value of resonant current

This paper presents a novel small signal analysis model based on peak value of resonant current to design controller of SRC. The small signal analysis of voltage controller is divided into software controller and SRC circuit. The software controller consists a PI controller and a voltage-to-frequency gain. The small signal model of SRC circuit is derived based on the assumptions where the output capacitor is small and the energy is transferred to load using controlled current source. The peak value of resonant current will be changed in proportional to the perturbation of small signal frequency command under constant load. Thereby the frequency to resonant current transfer function can be derived. Then the gains of PI voltage controller are yielded by Bode plot according to the required specifications under nominal condition. Moreover, simulated results by Simulink are carried out to analysis the controller design. In order to verify the correctness of proposed design method, a DSP-based SRC is constructed and tested by frequency response analyzer, which shows that the design and measured results are in good agreement and the bandwidth of voltage loop is near to 2 kHz.