Power Factor Controller (PFC) CCM + PWM Controller, with Surge Capability Enhancement

The highly integrated FAN4800AS/CS/01S/02S parts are specially designed for power supplies that consist of boost PFC and PWM. They require very few external components to achieve versatile protections / compensation. They are available in 16-pin DIP and SOP packages. The PWM can be used in either current or voltage mode. In voltage mode, feed-forward from the PFC output bus can reduce the secondary output ripple. Compared with older productions, ML4800 and FAN4800, FAN4800AS/CS/01S/02S have lower operation current that saves power consumption in external devices. FAN4800AS/CS/01S/02S have accurate 49.9% maximum duty of PWM that makes the hold-up time longer. Brownout protection and PFC soft-start functions available in this series are not available in ML4800 and FAN4800.

To evaluate FAN4800AS/CS/01S/02S for replacing existing FAN4800 and ML4800 boards, five things must be completed before the fine-tuning procedure: 1. Change RAC resister from the old value to a higher resister: between 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 1.224 V at VIN=85 VAC for universal input application from line input from 85 VAC to 270 VAC. 4. At full load, the average VVEA needs to be ~4.5 V and the ripple of VVEA needs to be less than 400 mV. 5. For the Soft-Start pin, the soft-start current has been reduced to half the FAN4800 capacitor.

There are two differences from FAN4800A/C/01/02 to FAN4800AS/CS/01S/02S: 1. Under-voltage protection debounce time is extended to one second. 2. PWM gate clamp voltage is raised to 19 V.