7p does not support 20W PD fast charge,
It only supports charging from 5W to 12W. When the original charger of random distribution is charged early, it charges the phone with 5W charging power. If you want the charging speed of iPhone7 to be faster, you can use the charger of ipad to charge 12W slightly faster. But it can only charge up to 12W
This is OK, but the maximum charging power of this device is only five watts, so there is no way to use fast charging, only according to the charging power of 5 watts.