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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 b...