A Simple Resonant Frequency Tracking Technique for DC Transformer Operation

In this article, we proposed a simple transformer secondary average voltage based resonant frequency tracking technique for LLC converter with DC transformer operation. It was found out that the transformer secondary side average voltage is lees than the output voltage in below resonant frequency operation region, which can be adopted to achieve resonant frequency tracking for LLC converter. Nevertheless, the proposed method fails to track the resonant frequency in above resonant frequency operation region since the transformer secondary voltage is always clamped by the output voltage in both at resonant frequency operating point and above resonant frequency operation region. Experiment results with different scenarios are presented to validate the effectiveness of the proposed method. Low cost, simple, and high noise immunity are the main advantages of the proposed method.