Based on the mechanism of flash Joule heating (FJH) for graphene synthesis, this study developed a novel flash Joule heating power supply device to enable the efficient production of graphene using lignin as the carbon source. The power supply features a wide adjustable output voltage range from 0 to 900 V and a current output capacity up to 1000 A, with controllable pulse durations ranging from 0 to 500 ms. When combined with a lignin-based load setup, experimental results demonstrate that direct current conduction through the carbon source significantly reduces the energy consumption during graphene conversion. Under a discharge voltage of 300 V, Raman spectroscopy of lignin mixed with carbon black shows the lowest defect level (ID/IG = 0.457) and exhibits characteristics of monolayer graphene (I2D/IG = 2.104). Properly increasing the number of discharges effectively reduces the number of graphene layers, whereas excessive discharges may lead to restacking of graphene sheets. This power supply demonstrates strong energy output capabilities and shows promising potential for the scalable production of graphene.