ML4803

February 1999 PRELIMINARY ML4803 8-Pin PFC and PWM Controller Combo GENERAL DESCRIPTION The ML4803 is a space-saving controller for power factor corrected, switched mode power supplies that offers very low start-up and operating currents. Power Factor Correction (PFC) offers the use of smaller, lower cost bulk capacitors, reduces power line loading and stress on the switching FETs, and results in a power supply fully compliant to IEC1000-3-2 specifications. The ML4803 includes circuits for the implementation of a leading edge, average current “boost” type PFC and a trailing edge, PWM. The ML4803-1’s PFC and PWM operate at the same frequency, 67kHz. The PFC frequency of the ML4803-2 is automatically set at half that of the 134kHz PWM. This higher frequency allows the user to design with smaller PWM components while maintaining the optimum operating frequency for the PFC. An overvoltage comparator shuts down the PFC section in the event of a sudden decrease in load. The PFC section also includes peak current limiting for enhanced system reliability. FEATURES s s Internally synchronized PFC and PWM in one 8-pin IC Patented one-pin voltage error amplifier with advanced input current shaping technique Peak or average current, continuous boost, leading edge PFC (Input Current Shaping Technology) High efficiency trailing-edge current mode PWM Low supply currents; start-up: 150µA typ., operating: 2mA typ. Synchronized leading and trailing edge modulation Reduces ripple current in ...