ML4802

August 2000 PRELIMINARY ML4802 PFC/PWM Controller Combo with Green Mode GENERAL DESCRIPTION The ML 4802 is a controller for power factor corrected, switched mode power supplies that offers Green Mode operation and reduced start-up and operating currents. Green Mode is an efficiency improving circuit feature which operates automatically in low power situations. This feature helps meet the demands of Energy Star™ programs. Power Factor Correction (PFC) offers the use of lower cost bulk capacitors, reduces power line loading and stress on the switching FETs. The ML4802 includes circuits for the implementation of a leading edge, average current, “boost” type power factor corrector and a trailing edge Pulse Width Modulator (PWM). The PFC frequency of the ML4802 is automatically synchronized to be one half that of the PWM. This technique allows the user to design with smaller PWM components while maintaining the optimum operating frequency for the PFC. 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 brown-out protection. s s FEATURES Internally synchronized PFC and PWM in one IC Green Mode maximizes efficiency during low power standby operation Low supply current (Start-up 200µA typ., operating 5.5mA typ.) Average current continuous boost leading edge PFC High efficiency trailing edge PWM can be configured for current mode operation Reduced ripple current in the storage capaci...