Fairchild's FAN7688 is an advanced pulse frequency modulation (PFM) controller for LLC resonant converters with synchronous rectification (SR), which provides best-in-class efficiency for isolated DC-DC converters.
The device uses charge-control-based current-mode control technology in which a triangular wave from an oscillator is combined with integrated switching current information to determine the switching frequency. This provides excellent control-to-output transfer of the power stage, which simplifies the feedback loop design while achieving true input power limit capabilities. Closed-loop soft-start prevents the error amplifier from saturating and monotonically increases the output voltage regardless of load conditions. Dual edge tracking adaptive dead time control minimizes the body diode on-time and maximizes efficiency.
