ML4826

June 1997 ML4826* PFC and Dual Output PWM Controller Combo GENERAL DESCRIPTION The ML4826 is a high power controller for power factor corrected, switched mode power supplies. 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 IEC1000-3-2 specifications. The ML4826 includes circuits for the implementation of a leading edge, average current “boost” type power factor correction and a trailing edge, pulse width modulator (PWM) with dual totem-pole outputs. The device is available in two versions; the ML4826-1 (fPWM = fPFC) and the ML4826-2 (fPWM = 2 x fPFC). Doubling the switching frequency of the PWM allows the user to design with smaller output 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 input voltage brown-out protection. The PWM section can be operated in current or voltage mode at up to 250kHz and includes a duty cycle limit to prevent transformer saturation. FEATURES s s s Internally synchronized PFC and PWM in one IC Low total harmonic distortion Reduced ripple current in the storage capacitor between the PFC and PWM sections Average current, continuous boost, leading edge PFC High efficiency trailing edge PWM with dual totem-pole outputs Average line voltage compensat...