Using TOP269EG off-line switcher IC, (U1), in a flyback configuration
can be designed a very simple high efficiency notebok laptop power
adapter.TOP269EG IC has an integrated 725 V MOSFET and a multi-mode
controller. It regulates the output by adjusting the MOSFET duty cycle,
based on the current fed into its CONTROL pin.This laptop power adapter
circuit will provide a fixed 19 volts output voltage at a maximum
current of 3.5A. input voltage range is between 90 to 265VAC.
Common-mode inductors L3 and L4 provide filtering on the AC input. X class capacitor C1 provides differential filtering, and resistors R1 and R2 provide safety from shock if the AC is removed, by ensuring a path for C1 to discharge. This is required by safety agencies when the capacitor value exceeds 100 nF. Bridge rectifier D1 rectifies the AC input, and bulk capacitor C2 filters the DC.
