The transformer works on 220v AC, as its primary coils were directly connected main supply wires before it's pulled out from the circuit board. That means it designed to work on 220v mains.Try to Reduce the input Voltage.
A charger does not care if the transformer core is saturating. Then it can be very cheeeep.
solved by incorporating a primary series resistance to lower the voltage enough to stop the saturation
I am not sure that there is a quick and easy calculation that can be done without knowing a lot more about the transformer.How to calculate the required resistor?