An Optimized Design Method for Enhancing Efficiency of LLC Secondary Side MOSFETs Using Current‐Source Gate Driver

ABSTRACT Various resonant gate driver circuits aim to recover gate drive losses and reduce switching losses, particularly in high‐frequency applications, enhancing overall system efficiency. The LLC resonant converter is favored in high‐frequency, high‐power‐density settings due to its soft‐switching capabilities. However, existing gate driver circuits for LLC converters usually operate at fixed frequencies and duty cycles, failing to address the variable requirements of LLC voltage regulation. Most current variable frequency and duty cycle drivers focus on buck converters, targeting large current handling without optimization for LLC circuits. A dual‐channel current‐source gate driver for secondary‐side MOSFETs in LLC‐DCX is proposed in this paper. This circuit enables variable‐frequency and duty‐cycle control. Specifically for LLC‐DCX applications, an optimized design utilizing current‐source gate drivers to control the LLC secondary rectifier is presented. The loss mechanisms in current‐source drive circuits are analyzed, and a comprehensive loss model for the LLC circuit is established. Key resonant parameters of the driver are optimized along with the dead‐time adjustment of the LLC converter. A prototype LLC converter was developed, operating at a resonant frequency of 1.3 MHz. Testing results show that the LLC prototype driven by the current‐source gate driver achieves a peak efficiency improvement of 0.67% compared with traditional drivers and recovers 82% of gate drive energy.