FAN4800AU: CCM PFC + PWM Combination Controller, Line Sagging Protection

The highly integrated FAN4800AU parts are specially designed for power supplies that consist of boost PFC and PWM. They require very few external components to achieve versatile protections and compensation. They are available in 16-pin DIP and SOP packages.

The PWM can be used in current or Voltage Mode. In Voltage Mode, feed-forward from the PFC output bus can reduce secondary output ripple. To evaluate FAN4800AU for replacing existing FAN4800A, FAN4800AS, old version FAN4800 and ML4800 boards, six things must be completed before the fine-tuning procedure:

1.Change RAC resistor from the old value to a higher resistor value: 6 MΩ to 8 MΩ.

2.Change RT/CT pin from the existing values to RT=6.8 kΩ and CT=1000 pF to have fPFC=64 kHz and fPWM=64 kHz.

3.The VRMS pin needs to be 1.224V at VIN=85VAC for universal input application with line input from 85 VAC to 270 VAC.

4.Change ISENSE pin filter from the exiting values to RFilter=51 Ω and CFilter=0.01 µF for higher bandwidth.

5.At full load, the average VVEA must be ~4.5 V and ripple on VVEA needs to be less than 400mV.

6.For the SS pin, the soft-start current has been reduced to half the FAN4800 capacitor.

Features

• Pin-to-Pin Compatible with ML4800, FAN4800, CM6800, and CM6800A
• PWM Configurable for Current-Mode or Feed-Forward Voltage-Mode Operation
• Internally Synchronized Leading-Edge PFC and Trailing-Edge PWM in One IC
• Low Operating Current
• Innovative Switching-Charge Multiplier Divider
• Average-Current-Mode for Input-Current Shaping
• PFC Over-Voltage and Under-Voltage Protections
• PFC Feedback Open-Loop Protection
• Cycle-by-Cycle Current Limiting for PFC/PWM
• Power-on Sequence Control and Soft-Start
• Line Sagging Protection
• f_RTCT=4 x f_PFC=4 x f_PWM

Application Notes