5 volt DC to 220V AC

 

If we want a 5 volt DC from a 220V AC, what should we do?

Without building anything: buy an AC adapter that uses a universal input (look at the letters stamped into the plastic under “INPUT”).

IF you want to build it yourself, a simple linear AC->DC power supply:

1. AC Transformer with winding ratio to take the voltage down from 220V peak to slightly about 6V peak (e.g., say a 36:1 winding ratio)
2. A “rectifier” or arrangement of four diodes that will turn the positive/negative swinging sine wave to an all-positive wave of ‘camel humps”. You lose about 0.7V here, so that’s why we ended step 1 with a 6V peak voltage, not 5V.
3. A resistor-capacitor circuit (typically using a large eletrolytic or “can” capacitor.
4. A voltage regulator to eliminate any residual voltage > 5V. Some voltage loss here, too.

The resulting circuit and waveforms of each stage look like this: