A Practical Analytical Small Signal Mode Applied for the LLC Converter Based on Hybrid Hysteretic Charge Control

In this paper, an analytical small-signal model applied for Hybrid Hysteretic Charge (HHC) control has been proposed and analyzed based on the improved analytical Direct Frequency Control (DFC) model which is based on the extended describing function method. For the first time, the systematical analytical open loop transfer functions from control to output, input to output, output impedance and the closed transfer functions of overall loop, audio susceptibility and output impedance are proposed and verified through simulation. Finally, the experiments on a design example of 12V&12A are conducted and verified. It has been shown that the calculations match well with the results from both the simulation results and experimental results, which has shown that the proposed analytical transfer functions are valuable and can be applied for the practical power design to achieve good prediction result.