A light emitting diode driving device and light system are provided. The light emitting diode driving device drives a light source by a received alternating current voltage. The light emitting diode driving device includes a rectifier, a feedback unit, a protection unit, a switch unit, a timing unit, and a control unit. The rectifier is electrically coupled to an alternating current voltage source and the light source for providing the alternating current voltage to the light source. The feedback unit is used to detect a loading state and generate a feedback signal according the loading state for outputting the feedback signal. The protection unit is used to receive the feedback signal and compare the feedback signal with a reference voltage built in the protection unit for outputting a switch signal. The switch unit is used to receive the switch signal and connect or disconnect the alternating current voltage source and the light source. Therefore, the protection unit can avoid a burnout due to an exceeding current of the light source.