Confused with fast charging and PD - Page 1
Forum section: electronics / beginners

author: Freshman
author_rank: Regular Contributor
timestamp: August 07, 2024, 04:31:08 pm
content: 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?

author: JustMeHere
author_rank: Frequent Contributor
timestamp: August 07, 2024, 05:28:02 pm
content: https://en.wikipedia.org/wiki/USB_hardware#USB_Power_Delivery

author: BeBuLamar
author_rank: Super Contributor
timestamp: August 07, 2024, 05:30:14 pm
content: USB PD is capable of supplying enough power for fast charging but it doesn't control the charge rate.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: August 07, 2024, 06:13:13 pm
content: 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.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 08, 2024, 11:12:48 am
content: 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 putinto a charger. So simple and clear, still a charger.Later came a split: you had power wall plug, which is apower supply, but does not includeallelectronics 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 ischarger? Laymen continued to call the power pluga 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 batterychargingper se. The "USB chargers" are just special type of wall plugs, they are not chargers butpower suppliesthat 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.

author: Whales
author_rank: Super Contributor
timestamp: August 08, 2024, 11:34:58 am
content: Quote from: Freshman on August 07, 2024, 04:31:08 pmUSB PD = a way of negotiating how much power you can getfast charging = anything marketing wants it to be. 15W is fast for a phone but slow for a laptop.

author: Don.don.don
author_rank: Newbie
timestamp: August 08, 2024, 11:42:49 am
content: Much appreciated, thank you!