NCP1246 ONSEMI [ON Semiconductor], NCP1246 Datasheet - Page 25

• Manufacturer Part Number: NCP1246
• Description: Fixed Frequency Current Mode Controller for Flyback Converters
• Manufacturer: ONSEMI [ON Semiconductor]

NCP1246
Figure 55. Startïup, Shutdown and AC Line Unplug Time Diagram
Oscillator with Maximum On Time and Frequency
Jittering
The NCP1246 includes an oscillator that sets the
switching frequency 65 kHz or 100 kHz depending on the
version. The maximum on time is 12.3 ms (for 65 kHz
version) or 8 ms (for 100 kHz version) with an accuracy of
±7%. The maximum on time corresponds to maximum duty
cycle of the DRV pin is 80% at full switching frequency. In
order to improve the EMI signature, the switching frequency
jitters ±6 % around its nominal value, with a triangleïwave
shape and at a frequency of 125 Hz. This frequency jittering
is active even when the frequency is decreased to improve
Figure 56. Frequency Modulation of the Maximum
the efficiency in light load condition.
Switching Frequency
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