NCP1239

DATA SHEET www.onsemi.com Fixed Frequency Current‐Mode Controller for Flyback Converter NCP1239 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...