Electronic circuit device

An electronic circuit device provided with:

• a multilayer circuit board having mounted thereon a plurality of circuit elements including a switching element to form a power conversion circuit, the multilayer circuit board having formed a wiring pattern electrically connecting the circuit elements to each other;
• and
• a heat dissipation member being in contact with the multilayer circuit board,
• the electronic circuit device comprising:
• a first wiring pattern formed on a first main surface of the multilayer circuit board, the first wiring pattern having the plurality of circuit elements including the switching element, mounted thereon along a predetermined direction, the first wiring pattern including a virtual shortest current path connecting the circuit elements to each other along the predetermined direction;
• a second wiring pattern formed on a surface of a specific layer including a second main surface opposing the first main surface, the second wiring pattern including an opposing current path that opposes an area where the virtual shortest current path is formed;
• vias configured to electrically connect the first wiring pattern formed on the first main surface with the second wiring pattern formed on the surface of the specific layer;
• and
• vias for heat transfer, configured to connect a mount area for the switching element on the first main surface with the second main surface, in an area on a side of the opposing current path, wherein
• the heat dissipation member is in contact with the second main surface, and heat generated in the switching element is dissipated by the heat dissipation member through the vias for heat transfer.