The power calculation of a charger consists of the following main steps.
Determine the output voltage of the charger
Usually the charger will indicate the output voltage, e.g. 5V, 12V, etc.
Determine the output current of the charger
The output current of the charger is also usually indicated on the charger, such as 1A, 2A, etc.
Calculate the power of the charger
Power = Voltage × Current
For example, for a 5V 2A charger, the power = 5V × 2A = 10W.
Allowance
In practice, you can choose a charger with a power slightly higher than that required by the device to allow for some margin.
Charger
For example, choose a 10W charger for a device that requires 8W of power.
Consider conversion efficiency
The charger itself has a certain conversion efficiency loss, so the actual output power will be slightly lower than the calculated value.
Further adjustments can be made according to the efficiency data of the charger.
In conclusion, the core of calculating the power of a charger is to determine its output voltage and current, and then multiply them to get the power. When choosing a charger, it is necessary to leave an appropriate margin according to the actual demand.