Obsolete as of 12-Mar-2013
The FAN4800 is a controller for power-factor-corrected, switched-mode power supplies. Power Factor Correction (PFC) allows the use of smaller, lower-cost bulk capacitors, reduces power line loading and stress on the switching FETs, and results in a power supply that fully complies with IEC-1000-3-2 specifications. Intended as a BiCMOS version of the industry-standard ML4800, the FAN4800 includes circuits for the implementation of leading edge, average current, boost-type power factor correction and a trailing-edge Pulse Width Modulator (PWM). A gate driver with 1A capabilities minimizes the need for external driver circuits. Low-power requirements improve efficiency and reduce component costs. An over-voltage comparator shuts down the PFC section in the event of a sudden decrease in load. The PFC section also includes peak-current limiting and input voltage brownout protection. The PWM section can be operated in current or voltage mode, at up to 250kHz, and includes an accurate 50% duty cycle limit to prevent transformer saturation. The FAN4800 includes a folded-back current limit for the PWM section to provide short-circuit protection.