Isolated power source apparatus

An insulated power source apparatus for a power conversion circuit provided with a series-connected circuit composed of an upper arm switching element and a lower arm switching element, the power conversion circuit including a plurality of series connected circuits connected in parallel to each other to generate a parallel-connected circuit, the insulated power source apparatus comprising:

• a substrate;
• an upper arm transformer mounted on the substrate, including a primary coil capable of being connected to a DC power source, and a secondary coil capable of supplying an upper arm drive power to the upper arm switching element;
• a lower arm transformer mounted on the substrate, including a primary coil capable of being connected to the DC power source, and a secondary coil capable of supplying a lower arm drive power to the lower arm switching element;
• a wiring provided on the substrate, connecting the primary coil constituting each of the upper arm transformer and the lower arm transformer, and the DC power source;
• a power source control unit mounted on the substrate, including a control switch and a control circuit, the control switch switching between ON and OFF to apply voltage of the DC power source to the primary coil constituting each of the upper arm transformer and the lower arm transformer, and the control circuit turning the control switch ON and OFF;
• a plurality of upper arm connection portions connecting a plurality of upper arm switching elements to the substrate;
• and
• a plurality of lower arm connection portions connecting a plurality of upper arm switching elements to the substrate,
• wherein
• the control switch is provided to be capable of forming a closed circuit including the DC power source, a plurality of primary coils constituting the upper arm transformer and the lower arm transformer and the control switch, when the control switch is turned ON;
• the power source control unit is disposed on one side of a connection region on the substrate where the upper arm connection portions and the lower arm connection portions are provided, with respect to a specific direction parallel to a plate surface of the substrate;
• the upper arm transformer is arranged between the power source control unit and the connection region in the specific direction;
• and
• the lower arm transformer is arranged closer to the power source control unit in the specific direction than to an end portion of the connection region which is opposite side of a portion where the power source control unit is arranged.