The FAN7688 is an advanced pulse-frequency modulation (PFM) controller for LLC resonant converters with synchronous rectification (SR), providing the industry's best energy efficiency for isolated DC/DC converters. It uses the latest mode control technology based on charge control, where the triangular waveform from the oscillator is combined with integrated switch current information to determine the switching frequency. This provides better control of the power stage - output transfer function, simplifies the feedback loop design, while enabling a true input power limiting function. Closed-loop soft-start prevents saturation of the error amplifier, allowing a monotonic rise in output voltage regardless of load conditions. Dual-edge tracking adaptive dead-time control minimizes body diode conduction time to maximize energy efficiency.
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