The FAN7688 is an advanced pulse-frequency modulation (PFM) controller for an LLC resonant converter with synchronous rectification (SR) to provide the best efficiency for isolated DC / DC converters. It uses current-mode control technology in charge-controlled , Where the triangular waveform from the oscillator is combined with the integrated switch current information to determine the switching frequency.This provides a better control of the power stage to the output transfer function and simplifies the design of the feedback loop while allowing for a monotonic increase of the output voltage. Dual-edge tracking adaptive dead-time control minimizes body-diode conduction, maximizing efficiency.
Applications desktop ATX, server, telecommunications power supply; intelligent 100W ~ 2KW + off-line power supply; efficient isolated DC / DC converter; large-screen display power supply; industrial power.
System Features • Secondary PFM Controller with Synchronous Rectifier-Controlled LLC Resonant Converter • Charge Current Control for Better Transient Response and Easy Feedback Loop Design • Adaptive Synchronous Rectification with Dual-Edge Tracking Control; Dead-cycle soft start Operating bandwidth (39KHZ ~ 690KHZ) Green function improves light load efficiency Automatic restart function (OCP, OSP, NON-ZVS, OLP and OTP) Primary side switch and Secondary side synchronous rectifier programmable dead time; 9Vdd undervoltage lockout; wide operating temperature range -40 ℃ ~ +125 ℃.
Program Features • Current mode control solution for better ripple and noise loop response • Anti-capacitor zone operation prevents MOS damage due to Fo adapting to the sensing area; • Dead-cycle soft-start prevents brownout when power is in soft Turn on; PFM + PWM + Burst control can achieve better efficiency at no load, light load or full load; Bilateral tracking adaptive SR control solution can obtain good efficiency and suitable for all MOSFETs.