Charging is only supported from a USB-C PD source (laptop, power bank or adapter). Beware of current incompatibilities though, see Working external battery pack?
I haven’t (yet) encountered a laptop that is capable of 15V PD output. The MacBook Pro will output 5V at 3A for the first device connected and 1.5A for the second (per side). Nothing higher than 5V. Same thing with a USB-A to USB-C cable, the projector needs to be able to complete Power Delivery negotiation over the CC pin which simply isn’t available in the legacy USB-A connector.