Introduction
This application note describes a detailed design strategy for a high-efficiency, compact flyback converter. Design considerations and mathematical equations are presented as well as guidelines for a printed circuit board layout. The highly integrated FAN6751 series of PWM controllers provides several features to enhance the performance for LCDM/TV, NB, and adapters.
Features
â High-Voltage Startup
â Low Operating Current: 4mA
â Linearly Decreasing PWM Frequency to 18KHz
â Fixed PWM Frequency: 65KHz
â Peak-Current-Mode Control
â Cycle-by-Cycle Current Limiting
â Leading-Edge Blanking (LEB)
â Synchronized Slope Compensation
â Internal Open-loop Protection
â GATE Output Maximum Voltage Clamp: 18V
â VDD Under-Voltage Lockout (UVLO)
â VDD Over-Voltage Protection (OVP)
â Internal Recovery Circuit (OVP, OLP)
â Internal Sense Short-Circuit Protection
â External Constant Power Limit (Full AC Input Range)
â Internal OTP Sensor with Hysteresis
â Built-in 5ms Soft-Start Function
â Built-in VIN Pin Pull HIGH (> 4.7V) Recovery Function for Second-Side Output OVP
â Brownout Protection with Hysteresis
Applications
General-purpose, switch-mode power supplies and flyback power converters, including:
â Power Adapters
â Open-frame SMPS
â LCD Monitor/TV
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