Determining synchronous rectification on-time of CLLC converter

A method for determining a synchronous rectification on-time of a CLLC (capacitor-inductor-inductor-capacitor) converter operating in an under-resonant mode, the method comprising:

• determining a transformer turns ratio and resonant frequency of the CLLC converter;
• using a simulation method, determining datasets of a peak current and output current of a secondary side diode, as well as an excitation current of a primary excitation inductor when the secondary side diode is off, and an excitation current of the primary excitation inductor when a primary side driving signal is off;
• measuring a current operating frequency and current output current of the CLLC converter;
• based on the operating frequency and the output current, calculating a first coefficient and a second coefficient by means of a linear interpolation method, wherein the first coefficient is equal to a ratio of the output current to the peak current then multiplied by
• π
• 2
• ,
• and the second coefficient is equal to a ratio of the excitation current of the primary excitation inductor when the secondary side diode is off to an excitation current of the primary excitation inductor when the primary side driving signal is off;
• measuring a resonant current initial value of a primary resonant inductor;
• and
• based on the transformer turns ratio, the resonant frequency, the resonant current initial value, the current output current, the first coefficient and the second coefficient, calculating a diode on-time.