Battery charging technology in consumer devices has evolved over the past 15 years. During the early boom of mobile consumer devices, each mobile handset manufacturer used their own proprietary charging technology and their respective charging connector. This created interoperability issues among different handsets and created a large amount of electronic waste with numerous chargers being thrown away due to incompatibility with other handsets.
My first handset device 15 years ago was a Sony Ericson that had the charging connector the same size as a current HDMI connector. The power supply that came with it only worked with that particular handset and was not compatible with any other phones. Everyone in my family had a different phone and each phone came with its proprietary charger. It was clear that there was a need for a universal charging system.
Based on the need for a universal charging system across all handset manufacturers, in 2009 the Open Mobile Terminal Platform (OMTP) expanded its connectivity specification based on micro-USB standards to describe requirements for a common charger and common connector to enable sharing the same charger for different handsets. This initiative from OMTP revolutionized the universal charging system and all the major handset manufacturers accepted it (Figure 1).
The standard USB micro-B charging started initially as BC 1.0 with 5 volts or 0.5 amps (5V/0.5A) and then evolved into BC 1.2 (5V/1.2A). As the battery capacity started increasing over the years, handset manufacturers started to integrate faster charging proprietary protocols such as Qualcomm Quick Charge, Samsung Adaptive Fast Charging (AFC) over the USB connector. These faster proprietary charging technologies were all limited to a maximum of 3A current pushed through the micro-B connector. Another important limitation with the micro-B connector was non-reversibility. Consumers would have to align the cable in the correct orientation to insert into the micro-B port of the phone.
As mobile phone technology evolved over the years, especially with network speeds, display resolution and refresh rates, camera resolution and high density internal memory, consumers demanded faster charging for their phones. This faster charging demand was limited by the maximum power specification of the micro-B connector and USB-IF was compelled to develop a higher power connector. In addition, since Apple developed the reversible Lightning connector for a better user experience, USB-IF did not want to lag behind and developed the reversible type C connector not only to deliver higher power but also to improve the non-reversibility limitation that came with the micro-B connector (Figure 2).
Basics of USB Power Delivery (PD)
USB PD is a specification for handling higher power, up to 100W, and allows a range of devices to charge quickly over a USB connection. It operates by communicating over a single communication channel between two devices to negotiate a power contract so they can determine how much power can be pulled from the charger. PD starts at the 5V setting and is configurable up to 20V. The latest PD specification is USB PD PPS (PD 3.0 V2.0) and allows for a constant communication every 10 seconds between the two devices to vary the voltage and current in the magnitude of 20mV and 50mA respectively (Figure 3). The minimum voltage can be 3V and maximum up to 21V. Using a standard USB-C cable, it can handle up to 60W, and will go up to 100W using a designated EMCA (electronically marked cable). An EMCA is a cable that has embedded electronics (e-marker IC) that can communicate with the USB ports via the USB PD protocol.
The type C or USB-C connector is a 24 pin reversible connector, which can deliver up to 100W power and is capable of 40Gbps data transfer speed. PD negotiation is done via single communication channel (CC).
The USB-C connector has 24 pins and because of its reversibility the pins are mirrored (Figure 4 and Figure 5). For the PD protocol, the CC1 and CC2 pins are used to detect cable orientation, current capability and to negotiate power contract between the source (charger) and the sink (device). The USB-C cable is poised to become the “universal” cable due to its capability of supplying 100W of continuous power as well as blazing fast data transfer speeds.
USB PD now has become the de-facto charging protocol in consumer market and majority of handset manufacturers has adopted USB power delivery as the universal charging technology.