Are you talking about an Evolv DNA control board??? I have a HCigar VT75 with a DNA75 board in it, if I plug it in to charge the led power light fades in and out while charging, once the charge is done the light turns green and stays on until unplug it. Most recent DNA boards do this as normal operation, the physical signals to tell you what it is doing. It is not advisable to use a mod while using its USB charging, Evolv boards will or should shut down charge if you use it, if it is an off brand device that isn't an authentic Evolv board, they might have the firing feature disabled during charging as a safety feature so you are not overloading the USB port.