Why transformers are used.

377

04:35:41

We keep on seeing transformerless AC to DC circuits presented, in reality, the circuit is useless if it is not a switch mode circuit. For a 220 vac rms to 12 vdc conversion what ever power is used 16 times that power has to be disappated ( usually as heat), (do your maths). Thus if you really want to do transformerless AC to DC, let's have some switch mode circuits.

published 9 years ago

hurz

9 years ago

If you know what you are doing you can drive a little load transformerless. Unfortunately most presented circuits are wrong in configuration and description.

BillyT

9 years ago

@Hurz, I agree, also a lot of the circuits are for 5 vdc and the wastage is worse at over 40 times, so for a 5 watt power supply, there is over 200 watts of energy wasted.

rich11292000

9 years ago

How much is wasted if the voltage drop was achieved with a cap instead of a resistor.

hurz

9 years ago

Good question rich! In both cases the same amount of power is wasted in sense of global warming. But at different places. While the resistor directly burns the power and you have to pay for it, with a cap you shift the power into the powerline network and the provider pays. Or with some chance your neigbour does compensate it with an inductive power waster and nobody has to pay for!

eekee

8 years ago

I have to ask, what happens if you use both capacitative and inductive power dissipators together?

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