The NCP1239 is a fixed-frequency current-mode controller

featuring a high-voltage start-up current source to provide a quick and

lossless power-on sequence. This function greatly simplifies the

design of the auxiliary supply and the VCC capacitor by activating the

internal start-up current source to supply the controller during start-up,

transients, latch, stand-by etc.

With a supply range up to 35 V, the controller hosts a jittered 65 or

100-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 minimum

level of 26 kHz. As the power further goes down, the part enters skip

cycle while limiting the peak current that insures excellent efficiency

in light load condition.

NCP1239 features a timer-based fault detection circuitry that

ensures a quasi-flat overload detection, independent of the input voltage.

Features

• Fixed-Frequency 65-kHz or 100-kHz Current-Mode Control

Operation

• Frequency Foldback Down to 26 kHz and Skip Mode to Maximize

Performance in Light Load Conditions

• Adjustable Over Power Protection (OPP) Circuit

• High-Voltage Current Source with Brown-Out (BO) Detection

• Internal Slope Compensation

• Internal Fixed Soft-Start

• Frequency Jittering in Normal and Frequency Foldback Modes

• 64-ms Timer-Based Short-Circuit Protection with Auto-Recovery or

Latched Operation

• Pre-Short Ready for Latched OCP Versions

• Latched OVP on VCC – Autorecovery for C and E Versions

• Latched OVP/OTP Input for Improved Robustness

• 35-V VCC Operation

• ±500 mA Peak Source/Sink Drive Capability

• Internal Thermal Shutdown

• Extremely Low No-Load Standby Power

• Pin-to-Pin Compatible with the Existing NCP1236/1247 Series

• These Devices are Pb-Free and are RoHS Compliant

Typical Applications

• AC-DC Converters for TVs, Set-Top Boxes and Printers

• Offline Adapters for Notebooks and Netbooks