An energy supply device from low voltage to high voltage mainly comprises n (n is more than or equal to 2) isolation transformer subunits (5) and an isolation sleeve (4), wherein the n (n is more than or equal to 2) isolation transformer subunits (5) are connected in series and then are placed in the closed insulation sleeve (4) filled with an insulation medium. By the energy supply device, energy can be supplied from low voltage to high voltage, the energy supply device is simple in structure and is easy to implement, the problem of insulation between an energy supply load and the high voltage is solved, and the power supply reliability is improved.