e.g. If a phone charger is plugged into an outlet yet has no phone connected to be charged, why does it draw power?
In: Technology
Modern chargers draw very little power when just plugged in. They have active power-electronics (a high-frequency switching rectifier) on the input.
Older chargers would have a big 60 Hz transformer to step down the voltage followed by a rectifier to make it DC. The transformer would always see wall voltage, and the core would be magnetized back and forth at 60 Hz regardless of load. This caused hysteresis loss (almost like friction of the magnetic domains flipping back and forth) that was not so tiny. I am pretty sure new products are not allowed to do that any more because of this.
Latest Answers