DC to DC Converter vs AC to DC Converter

I asked about DC to DC converter and I got the answer that "when we need different dc voltages and need higher amperage from low amperage batteries we use DC to DC converters like in Laptops"

My question isn't possible that we get different AC voltage levels from transformer and simply convert them to DC.

As we know the purpose of using AC signal is that it can amplified very easily then why using DC to DC converter.

Hi

AC to DC conversion via a rectifier and filter is not a very efficient process as it involves line frequency which requires heavy core transformers. That is the reason why nowadays, every laptop adapter is smps based in order to reduce size, increase efficiency (SMPS circuits can have efficiency well above 90%) and also increase the operating voltage range to match US and European standards.

Once the DC voltage is fed into the laptop, we require several different voltages for different devices like: (DVD writer, Hard drive, Processor, WIFI etc). In that scenario, a DC-DC converter comes into picture which can efficiently convert high DC to low DC (buck converter) or low to High DC (boost converter). There are lot of textbooks based on DC-DC conversion.

You dont want multiple high voltage AC going into your laptop.

regards
Darkseid

1. For AC-DC conversion, the ripple is difficult to compress. But in DC-DC conversion, that is easier.
2. Telecomm equipment always use -48V DC, that is safe to human body. But AC, say 110V or 220V, is dangerous to operator.

Tony why did you use minus sign -48 DC. I think (-) sign only shows direction of current

That's not true. Because GND is always link to earth, shell of equipments, etc, voltage should have positive or negtive.