Current Mode PWM Controller for Both Forward and Flyback Converters

NCP1212 is a high performance current mode PWM controller specifically designed for off−line and DC−to−DC converter applications. The device requires very few external components and offers designer additional protection for better system reliability. The device features a trimmed oscillator for precise Duty Cycle control, accurate bandgap voltage reference, high gain error amplifier, current sensing comparator and a high current totem pole output gate driver that ideally drives the external power MOSFET.

FEATUREs
• Trimmed Oscillator Charge and Discharge Current for Precise Duty Cycle Control
• Internal High Accuracy Bandgap Voltage Reference
• Current Mode Operation up to 200 kHz
• Inherent Feed Forward Compensation
• Latching PWM for Cycle−by−Cycle Current Limiting
• High Current Totem Pole Output Gate Driver
• Low Startup and Operating Current
• Internal Undervoltage Lockout with Hysteresis
• Internal Leading Edge Blanking for Current Feedback
• Direct Interface with Optocoupler for Secondary Sensing
• Built−in Soft−Start Function, Programmable by External Capacitor
• User Programmable 48%/82% Maximum Duty Cycle Selection
• Output Overvoltage Protection Against Open Loop
• AC Line Brownout Detect Protection
• Output Overload Protection Irrespective of Auxiliary Voltage Level
• Pb−Free Packages are Available

Typical Applications
• ATX PC Power Supply
• Universal Input Wall Mount Adaptors
• CRT Monitor
• All Flyback and Forward SMPS Systems