Abstract: The power supply apparatus includes a transformer, a switching section, a feedback section; a control section; and a resistor adapted to separate a first ground and a second ground from each other on the secondary side of the transformer, the first ground being located on a load side supplied with the output voltage while the second ground being located closer to the transformer than is the first ground, wherein a second resistor is connected to the second ground and a reference voltage of the feedback section is connected to the first ground.

Abstract: The invention relates to a method for producing nitrogen trifluoride by gas-solid reaction. This method includes the steps of (a) providing a packed-bed-type vessel filled with a particulate solid of an ammonium complex of a metal fluoride; (b) introducing a fluorine-containing gas into the vessel to allow the fluorine-containing gas to flow upwardly through the vessel such that fluorine of the fluorine-containing gas is reacted with the particulate solid in the vessel, thereby to obtain a reaction gas containing nitrogen trifluoride; and (c) separating the nitrogen trifluoride from the reaction gas. A part of the reaction gas flowing out of the vessel may be introduced into the vessel, and thereby circulated through the vessel. The yield of nitrogen trifluoride becomes substantially improved by this method.