Disclosed are a non-narrow voltage direct current (NON-NVDC) charger and a control method thereof. In the present disclosure, a proper target voltage, related to a turn-on voltage of a switch circuit, is determined according to an output voltage of a load, a storage voltage of an energy storage device and a turn-on resistance value of the switch circuit. Then, according to the determined target voltage, the NON-NVDC charger can enter a supplement mode at an appropriate time. The NON-NVDC charger can be operated stably and has excellent operation efficiency even when a current flowing through a transformer close to a maximum safe current.