USB-TTL problem connected to my UART-WIFI module help!
The PL-2303HX Datasheet doesn't seem very clear on the amount of current that the on-chip regulator can handle but according to the TLG10UA03 Datasheet which is written in Chinese it appears the module has a typical current draw of 300mA. Most chips like the PL-2303 use a linear regulator so you'll be dissipating around 510mW plus what the converter itself uses so it's enough to make it feel warm. That leaves a few possibilities:


You may not have a problem at all. For example see Why is my Arduino Ethernet shield getting hot? You might want to measure the temperature to see what it is although if the PL-2303 isn't designed to source that much current you might still run into problems.
If you want to be on the safe side another option would be to use the 5V output from the module that comes straight from the USB port along with a 3.3V regulator between the boards. That could either be a switching step-down regulator (many are available on e-bay) or a larger linear regular that can dissipate more heat.


Having said that the PL-2303 does have a way to request 500mA from the USB port which wouldn't make much sense if it wasn't capable of delivering that amount, so my best guess would be it's not really a problem.