High-Voltage Current-Mode PWM Controller Featuring Peak Power Excursion and Extremely Low Stand-by Power Consumption

The NCP1249 is a highly integrated high−voltage PWM controller capable of delivering a rugged and high performance offline power supply with extremely low no−load consumption. With a supply range up to 30 V, the controller hosts a jittered 65−kHz switching circuitry operated in peak current mode control. When the power on the secondary side starts to decrease, the controller automatically folds back its switching frequency down to a minimum level of 26 kHz. As the power further goes down, the part enters skip cycle while freezing the peak current setpoint.

FEATUREs
• High−voltage Current Source for Lossless Start−up Sequence
• Remote Input for Standby Operation Control
• Automatic and Lossless X2 Capacitors Discharge Function
• 65−kHz Fixed−frequency Current−mode Control Operation with 130−kHz Excursion
• Internal and Adjustable Over Power Protection (OPP) Circuit
• Internal Brown−Out Protection Circuit
• Frequency Foldback down to 26 kHz and Skip−cycle in Light Load Conditions
• Adjustable Ramp Compensation
• Internally Fixed 4−ms Soft−start
• 100% to 25% Timer Reduction from Overload to Short−circuit Fault
• Frequency Jittering in Normal and Frequency Foldback Modes
• Latched OVP Input for Improved Robustness and Latched OVP on Vcc
• Up to 30 V Vcc Maximum Rating
• +300 mA/ −500 mA Source/Sink Drive Capability
• Extremely Low No−load Standby Power
• Option for Auto−Recovery or Latched Short−Circuit Protection
• Internal Thermal Shutdown with Hysteresis
• These are Pb−Free Devices

Typical Applications
• Converters Requiring Peak−power Capability such as Printers Power Supplies, ac−dc Adapters for Game Stations