SLYT819 October 2021 BQ25980
USB PD is a new protocol that enables faster and more flexible power sources. The USB Implementers Forum developed USB PD concurrently with USB-C, which is the physical connection, and it is a subset of the new USB 3.1 standards.
Table 2-1 shows the development of the USB standard. With the development of USB PD and USB-C connectors, the power source is capable to supplying as much as 100 W of power [1].
USB Standard | USB Port Output Voltage | USB Port Current Limit | USB Port Maximum Power output |
---|---|---|---|
USB 2.0 | 5 V | 500 mA | 2.5 W |
USB 3.1 | 5 V | 900 mA | 4.5 W |
USB BC1.2 | 5 V | 1.5 A | 7.5 W |
USB BC1.2 with high-voltage downstream charging port (HVDCP) | 5 V, 9 V, 12 V | 1.5 A | 18 W |
USB PD | 5 V, 9 V, 12 V, 20 V | 5 A | 100 W |
USB PD with PPS | Adjustable voltage from 3.3 V to 21 V in 20-mV step | Adjustable current up to 5 A in 50-mA step | 100 W |
Unfortunately, the traditional regulated buck, boost or buck-boost integrated circuit cannot fully use 100 W of power because of the relatively low efficiency. The unregulated switched-capacitor converter becomes feasible in the system with the development of USB PPS[2]. The ultra-high efficiency of the switched-capacitor converter can take full advantage of the latest USB Type-C PD PPS standard.