Location:Training / Power Supply / FAN7688 Advanced Secondary Side LLC Resonant Converter Controller with Synchronous Rectifier Control / Fairchild FAN7688

The FAN7688 is an advanced pulse frequency modulation (PFM) controller designed to provide the industry's best isolated DC/DC converter efficiency, LLC resonant converter including synchronous rectification (SR). It uses current-mode control technology based on charge control, where the oscillator's triangular waveform is combined with integrated switch current information to determine the switching frequency. This provides better transfer of power stage control to the output, simplifying feedback loop design while allowing true input power limiting characteristics. The closed-loop soft-start feature helps prevent error amplifier saturation and allows a monotonic rise in the output voltage regardless of load conditions. Dual edge-tracking adaptive dead-time control minimizes body diode conduction time, thereby maximizing efficiency.