The MC33368 is an active power factor controller that functions as a boost preconverter in off–line power supply applications. MC33368 is optimized for low power, high density power supplies requiring a minimum board area, reduced component count and low power dissipation. The narrow body SOIC package provides a small footprint. Integration of the high voltage startup saves approximately 0.7 W of power compared to resistor bootstrapped circuits.
The MC33368 features a watchdog timer to initiate output switching, a one quadrant multiplier to force the line current to follow the instantaneous line voltage a zero current detector to ensure critical conduction operation, a transconductance error amplifier, a current sensing comparator, a 5.0 V reference, an undervoltage lockout (UVLO) circuit which monitors the VCC supply voltage and a CMOS driver for driving MOSFETs. The MC33368 also includes a programmable output switching frequency clamp. Protection features include an output overvoltage comparator to minimize overshoot, a restart delay timer and cycle–by–cycle current limiting.

• Lossless Off–Line Startup
• Output Overvoltage Comparator
• Leading Edge Blanking (LEB) for Noise Immunity
• Watchdog Timer to Initiate Switching
• Restart Delay Timer