Confused with fast charging and PD

[Freshman]

My question is regarding mobile and laptop charging.

I have recently gone through many products (mobiles and laptops) and the USB standards.

All are confusing as they speak about fast charging and USB PD. I am getting confused.

Can someone tell me whether USB PD implies fast charging or am I missing to understand something?

[JustMeHere]

https://en.wikipedia.org/wiki/USB_hardware#USB_Power_Delivery

[BeBuLamar]

USB PD is capable of supplying enough power for fast charging but it doesn't control the charge rate.

[LinuxHata]

Initially, Apple had standard, 5V 1A chargers.
Then they've made "Fast" chargers, which were delivering 2.1A at 5 volts.
However, while Apple was stuck at 10W charging, in the android world, several charging standards emerged, most common and popular to be Quallcom "Quick Charge", which was delivering up to 18W into phone. However, further improvements of that protocol made more into power efficiency, but not into power amount. So other companies started to develop their own solutions - Samsung, Huawei, Oppo, all have made their own standards. So it was really crowded there, and big guys decided to settle, so USB PD was born.

But USB PD does not means that you will get fast charge all the time. This is just standard, which has different "power levels", so it is quite possible for charger to be USB PD compliant, but deliver only 1 amp into load at 5V. To make things even worse, some companies developed their own extensions, which run over USB PD, and are not fully compatible. For example, Samsung developed PPS protocol, which runs over the USB PD protocol, but requires compatible charger, so even if you have USB PD charger, to charge the modern samsung phones, it should also have PPS support. So, things are really complicated.

[Siwastaja]

There has been this common nomenclature mismatch going on for at least two decades already.

In the past, it was usual to have a device called battery charger (e.g., for lead acid car batteries), which was then connected to a battery. Simple to understand.

Then became things like mobile phones, camcorders etc. Many had removable battery, which was physically put into a charger. So simple and clear, still a charger.

Later came a split: you had power wall plug, which is a power supply, but does not include all electronics required for charging any type of battery. And inside the decice (e.g. mobile phone, laptop) then resides the rest of charging electronics.

Now what is charger? Laymen continued to call the power plug a charger. To end user, the idea that there is some charging IC and semiconductors inside their phone is meaningless. But for people more than end users, e.g. hobbyists and beginner designers, this can get confusing. In a professional setting, I just call the parts "power supply" (the wall plug with USB cable), and "charging circuit" (the IC, inductor, capacitors inside the device).

USB standard does not specify anything about battery charging per se. The "USB chargers" are just special type of wall plugs, they are not chargers but power supplies that communicate and negotiate a certain voltage. More circuitry is needed to feed this voltage into a battery - often at lower voltage than the USB PD input, and with active and controlled current limitation. (The "current limitation" in USB power supplies is only for protection - basically electronic fuse, "turn this off if current is exceeded.)

How the DC input voltage is taken and fed into battery, i.e., charging, is then up to manufacturer to decide.

[Whales]

All are confusing as they speak about fast charging and USB PD. I am getting confused.

USB PD = a way of negotiating how much power you can get

fast charging = anything marketing wants it to be.   15W is fast for a phone but slow for a laptop.

[Don.don.don]

Much appreciated, thank you!