Power supply apparatus

A power supply apparatus, comprising:

• a multi-layer circuit board having a printed circuit board layer on a lower surface and a printed circuit board layer on an upper surface;
• one or more power devices attached to the printed circuit board layer on the lower surface of the multi-layer circuit board;
• electronic components attached to the printed circuit board layer on the upper surface of the multi-layer circuit board;
• a thermally conductive plate at least partly composed of a thermally conductive plastic, wherein an upper surface of the plate faces the printed circuit board layer on the lower surface of the multi-layer circuit board;
• and
• a thermally conductive encapsulant provided to fill substantially all of the empty space between the printed circuit board layer on the lower surface of the multi-layer circuit board and the one or more power devices attached thereto and the upper surface of the thermally conductive plate to dissipate heat through the encapsulant to the thermally conducive plate;
• and
• wherein the multi-layer circuit board further comprises a thermally conductive heat-spreading layer which is located no more than 150 micrometres from the printed circuit board layer on the lower surface of the multi-layer circuit board and which is thicker than that printed circuit board layer whereby the heat from the one or more power devices attached to that printed circuit board layer is spread across the multi-layer circuit board to dissipate through that printed circuit board layer and into the thermally conductive encapsulant.