It is defined VBUS 5V~20V in USB PD 3.0 version, it is added 28V, 36V, 48V in USB PD 3.1 spec, that is called EPR(Extended Power Range. Base on maximum 5A current condition, the maximum power support to 48V/5A=240W.
It also added the function like the PPS in PD 3.1 EPR mode. it is called the EPR AVS(Adjustable Voltage Supply). The minimum voltage step is 20mV in PPS, however the minimum voltage step is 100mV in AVS. Sink can ask Source to output 15.1V、15.2V.....47.9V、48V. There are CV(Constant voltage) and CL(Current limit) modes in PPS, but there is only CV mode in AVS.
There are only Fixed output voltage 28V, 386,48V in EPR mode, but output voltage can be 100mV a step between 15V to 48V after enter AVS mode,
The Source device's PDP(PD Power) between 100W and 140W can use only EPR 28V, it can't operateon 36V and 48V. The Source device's PDP above 180W can use EPR 48V mode.
If Source and Sink want to enter EPR mode, the cable EPR is needed. The communication procedure is showed as below. Establishing standard PD contract at first, when Sink ask to enter EPR mode the ,Source would try to communicate with cable to identify if Cable is EPR Cable. EPR Type-C cable can resist voltage 50V, it is different from standard Type-C 20V cable. But if cable is part of EPR Source device, Source can bypass the action of identifying EPR cable.
Reference：1.https://www.usb.org/sites/default/files/USB%20Power%20Delivery%2020210602.zip
USB_PD_R3_1 V1.0 202105.pdf
