Forcing Nexus 5 to charge wirelessly even when USB device connected

Is there some method to make wireless charging take priority over wired (USB) charging? I have a device that has to be plugged in to the micro-USB port of the Nexus, and it is preventing wireless charging from occurring. The device only draws power from the USB, but still wireless charging stops the moment it is plugged in. Google has not been helpful so far. There seem to be other phones whose wired charging stops when placed on a wireless charger, but apparently not the Nexus (nor have I been able to find a user's manual which states which one takes priority). There doesn't seem to be any visible setting in Android. Any clues? Maybe some App which can set the charging priority? Completely disabling USB charging is also fine, as long as the USB can still supply power to connected devices (rooting is not an option).