UCC38050

• Transition Mode PFC Controller for Low Implementation Cost
• Industry Pin Compatibility With Improved Feature Set
• Improved Transient Response With Slew-Rate Comparator
• Zero Power Detect to Prevent Overvoltage Protection (OVP) During Light Load Conditions
• Accurate Internal VREF for Tight Output Regulation
• Two UVLO Options
• OVP, Open-Feedback Protection, and Enable Circuits
• ±750-mA Peak Gate Drive Current
• Low Start-Up and Operating Currents
• Lead (Pb)-Free Packages

The UCC38050 and UCC38051 are PFC controllers for low-to-medium power applications requiring compliance with IEC 1000-3-2 harmonic reduction standard. The controllers are designed for a boost preregulator operating in transition mode (also referred to as boundary-conduction mode or critical conduction-mode operation). They feature a transconductance voltage amplifier for feedback error processing, a simple multiplier for generating a current command proportional to the input voltage, a current-sense (PWM) comparator, PWM logic, and a totem-pole driver for driving an external FET.

In the transition mode operation, the PWM circuit is self-oscillating, with the turnon being governed by an inductor zero-current detector (ZCD pin), and the turnoff being governed by the current-sense comparator. Additionally, the controller provides features such as peak current limit, default timer, overvoltage protection (OVP) and enable.