Power Delivery (PD) Power Banks
Not only smartphones and tablets, but also notebooks and even small all-in-one PCs (AiO) are increasingly being supplied with energy via USB-C instead of proprietary connections. Since the original USB type A connector was initially designed for 0.5 watts, primarily supplying mice and keyboards, later increased several times up to 7.5 watts, a major innovation was needed.
This innovation actually came out in 2012, but never made it to a real-world product in its initial form. The big breakthrough came in 2014, together with the release of the new USB-C connector - which can not only be inserted in both directions, but was designed from the start for up to 100 watts power supply.
Obviously, we are talking about USB Power Delivery, often named USB-PD or just PD for simplicity. But Power Delivery isn't mandatory for USB-C devices. In practice, that means: Not every USB battery with an USB-C connection and not every battery with USB-PD supports up to a 100 watts!
While there were five fixed profiles in the first revision, which is now considered outdated, flexible groups have been introduced in revision 2.0, which are based on the maximum power consumption. For example, a notebook manufacturer that estimates 27 watts for a slim Ultrabook can define 9 volts (3 A), 15 volts and / or 20 volts as the input voltage.
Power Delivery 3.0 goes even further and eliminates almost all limits. Power source and consumers can freely negotiate the voltage between 5-20 volts in fine 20 mV steps, called Programmable Power Supply or PPS for short. Only the current may not exceed 3 or 5 amps respectively (the latter only at 20 volts). Fortunately, USB Power Delivery is backward compatible. Modern USB batteries with PD 3.0 generally work with old notebooks, tablets or smartphones, that were developed based on older revisions, without any problems.